Review
Enhancement in hydrophobicity of low rank coal by surfactants —A critical overview
Shobhana Dey ?
Council of Scienti ?c and Industrial Research-National Metallurgical Laboratory,Jamshedpur,India
a b s t r a c t
a r t i c l e i n f o Article history:
Received 30December 2010
Received in revised form 14September 2011Accepted 15October 2011
Available online 9December 2011Keywords:Low rank
Hydrophobicity Oxidation Wettability Surface charge
The ?otation of ?ne (?0.5mm)low rank or oxidized coal is dif ?cult to achieve with the common coal ?ota-tion collectors like kerosene,fuel oil or diesel oil (oily collector).The presence of small amounts of oxygen is enough to cause oxidation.The oxidation of coals starts with the physical adsorption of oxygen on the surface to form an oxycomplex followed by chemical adsorption of oxygen to form polar phenolic –OH,carbonyls,phenols and peroxide type oxygenated moieties by the rupture of cyclic rings.The addition of promoter,sur-factant or oxygenated functional groups to the collector molecule markedly enhances the ?otation of lower rank and oxidized coals due to the hydrogen bonding with the polar part of the coal surface and the reagent.The performance of these reagents is compared with that of oily collectors,namely kerosene,dodecane,non-ylbenzene and polar part of the surfactant having an oxygen atom.The mode of addition of non-ionic surfac-tant with oily collector also has a major role in the ?otation response.The addition of non-ionic surfactant after the oily collector has shown a positive effect on yield and grade.
?2011Elsevier B.V.All rights reserved.
Contents 1.Introduction ..............................................................1512.
Literature review............................................................1522.1.Forms of oxygen on coal surface .................................................1522.2.Generation of surface charge at coal/water interface ........................................1522.3.Wettability of oxidized coal ...................................................1532.4.Wettability of oxidized coal in presence of surfactants .......................................1532.5.Effect of coal particle –promoter interactions on ?otation......................................1542.6.Flotation of oxidized coals ..........................
..........................1542.6.1.Mechanism of adsorption ................................................1552.6.2.Collector spreading ...................................................1552.6.3.Interaction of the oxygenated non-ionic part of collectors on coal surface ...........................1562.6.4.Structural effect of reagents on ?otation response...........
..........................1563.Summary ...............................................................157References .......................................
..........................
157
1.Introduction
Coal ?otation makes use of the natural hydrophobicity of the car-bonaceous matter in coal.To enhance the hydrophobicity of the coal particles,oily collectors,such as diesel oil and kerosene are usually added.For higher-rank coals,the reagent consumption in ?otation is low because of the natural hydrophobicity of the coal.However,
the oxidized coals or low rank coals are dif ?cult to ?oat with com-monly used fuel oil or kerosene and large amounts of collectors are required to achieve satisfactory yields [1].The poor ?oatability is due to the presence of greater amounts of oxygen content and abun-dance of hydrophilic surface functional groups [2,3,4,5].It was reported by Quast and Readett [6]that sub-bituminous coals have an average oxygen content of 18%,with carboxylic groups constitut-ing about one third of this amount.Therefore,the amount of adhesion of oil droplets onto low rank coals is very small,and the use of oil alone does not improve ?otation.
Fuel Processing Technology 94(2012)151–158
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0378-3820/$–see front matter ?2011Elsevier B.V.All rights reserved.doi:
10.1016/j.fuproc.2011.10.021
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Fuel Processing Technology
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There are many coal processing plants that are facing problems in ?oating oxidized coal.The source can be from outcrop coal,strip mines—where the overburden was removed several years before mining started or even from improper stockpiling over a period of time.Oxidation alters both physical and chemical properties of the coal surface and reduces the?oatability.The surface oxidation of coal is re?ected by decrease in pH of the pulp.To solve this problem reagents containing promoter are recommended,along with large amount of fuels[7].
In?ne coal,oxidation by weathering or coals kept at mine site or during storage and transportation results in the formation of oxygenat-ed functional groups.Carboxyl,phenolic and carbonyl are the most commonly found functionalities on the coal surface and their concen-tration can be determined[8].This reduces the hydrophobicity of the coal surface by increasing the number of sites that form hydrogen bonds with water molecules.It is generally accepted that oxidation of coal(whether it be exposed arti?cially or to the atmosphere)proceeds in three stages.Stage I is the super?cial oxidation characterized by the formation of coal–oxygen complexes with acidic properties.In Stage II,the organic components of coal form alkaline soluble hydroxy car-boxylic acids called humic acids.In Stage III,the humic acids degrade to simple water-soluble acids[9].Adsorption of oxygen on the coal sur-face is exothermic and,besides the moieties formed on the coal surface, the reaction products like CO,CO2and H2O may be released from the structure[10].The most susceptible linkages to oxidation were found to be theα-CH2groups to polyaromatics[11,12,13,14].Mitchell et al.
[15]revealed an interesting point on oxidation that blue-light irradia-tion is also a strong agent to oxidize the vitrinite surfaces.Sarikaya et al.[16]observed that upon oxidation the?otation yield reduces from95%to24%for a bituminous coal using alcohol type frother only. The oxidation of the surface makes the coal more dif?cult to?oat with oily collectors[17–22].An oily collector cannot spread on the surface of the coal particles.The present paper highlights the study of oxidation of the coal surface,adsorption behavior of surfactants on oxidized or low rank coal,its effect on?oatability and improvement of their hydro-phobicity by adding reagents in different sequences.
2.Literature review
Coal?otation is a complex phenomenon involving several phases (particles,oil droplets and air bubbles).These phases then simulta-neously interact with each other and with other species viz,molecules of surfactants/promoting reagents and dissolved ions in water.The structure of surfactants/collector molecules,the type of electrical charge possessing the collector,its dispersion ability and the type of bonding(physisorption or chemisorption)that forms with the coal sur-face are all important factors for imparting hydrophobicity on the coal surface.Molecular orientations of the reagent molecules also play an important role on the adsorption process[23–25].The?otation studies performed with low rank coals indicated that the mixtures of oils could be used to improve?otation recovery and selectivity[26].As it is known,oil emulsions are thermodynamically unstable due to increased interfacial area.Therefore,to stabilize the emulsions,mechanical energy or a surfactant is needed.Mechanical emulsi?cation is usually stable only for a short period of time,while emulsions produced with surfac-tants are stable over a long period of time[27].It was shown that the emulsi?cation of the kerosene produced by the high intensity stirring shaped droplets of about20μm in size,while emulsi?cation with the addition of surfactants(anionic and cationic)reduced the droplet size to about1.5–2.0μm[28,29].This stabilization of the oil droplets using surfactants is due to the decrease in surface free energy with adsorption at the oil/water interface of the surfactants.
Surfactants,when added together with oil,are likely to improve coal ?otation by several mechanisms.When added as emulsi?ers,they aid dispersion of the oil into?ne droplets[27].The increased numbers of oil droplets assist?otation kinetics by increasing the probability of coal particle–oil droplet collisions[30].Surfactants also lower the ener-gy required to spread the collector oil[31]across the coal surface through adsorption at the coal/water interface and coal/oil interface. At low concentrations,such surfactants make coal hydrophobic,where-as,at high concentration,they make it hydrophilic[32].If the surfactant promotes the spreading and adhesion of oil,the hydrophobicity of coal will increase,leading to a high probability of adhesion of the air bubble to the coal particle[31,33].In contrast,if the wetting of the coal by water is increased by the surfactant,which usually happens at high con-centrations,the recovery of the coal will decrease.
Chander et al.[34]carried out?otation of low rank coal of?150μm size with dodecane and it was shown that substantial amount of reagent was required to achieve the satisfactory yield.They also performed coal ?otation with non-ionic and ionic surfactants.Some of the water soluble surfactants make coal more hydrophilic or wettable when present in suf?cient quantities.In contrast,the same surfactants increase the hydrophobicity when present in small amount.Therefore,the?otation characteristics of coals largely depend on these surface properties.
2.1.Forms of oxygen on coal surface
Quast and Readett[6]reported the wettability of sub-bituminous coal surface by the presence of oxygen content of18%and the carboxylic groups constituting about one third of this amount.Considerable con-troversy exists regarding the forms of oxygen in coal and the means of analyzing for them.The values in Table1for carboxyl(–COOH)and hy-droxyl(–OH,both phenol and alcohol)are cited from Penn State Coal Data Bank and a variety of other sources[3,35–38].It was found that the oxygen functionalities also include ether(C–O–C),ketone(C=O) and methoxy(–OCH3)group in addition to–OH and–COOH.It was observed by Korobetskii et al.[39]that small amounts of residual oxygen are suf?cient to bring about oxidation.Natural oxidation mainly affects the external surfaces of coal,hence,for better?otation results the size reduction must be retarded as long as possible[40].Weathering of the coal particles developed cracks whose extent was a function of coal rank.Low rank coal particles developed extensive cracks whereas high rank coals hardly seem to be affected physically[41,42].
2.2.Generation of surface charge at coal/water interface
Since coal is a very heterogeneous substance,the mechanism of sur-face charge generation is very complex.Campbell and Sun[43]have proposed a simpli?ed model based on the earlier work of Glembotskii [44].This model assumes that when a freshly crushed coal surface is ex-posed to the atmosphere,the exposed carbon atoms in the lattice react with atmospheric oxygen and form oxidized surfaces with charging characteristics similar to oxide minerals.In this case,hydroxyl and hy-dronium ions will be the potential determining ions.
Kelebek et al.[45]investigated the generation of charging mechanism for low rank lignitic coals would be different due to the large amounts of oxygen-containing functional groups.The charging mechanism for lignite was explained based on the presence of oxygen-containing weakly acidic groups(e.g.,phenolic OH and COO).Depending on the moisture content, the surfaces possess these groups in dehydrated(oxide form)or in hydrated forms.The surface charge can be determined mainly by the
Table1
Approximate content of various oxygen functional groups in coal(based on the data of Blom et al.[35]).
%C Total O C–O–Cðer–OH C=O–COOH–OCH3
9511----856232--75166711-
65a28107281
a A European brown coal.
152S.Dey/Fuel Processing Technology94(2012)151–158
degree of dissociation of the weakly acidic groups at the surface.The dis-sociation takes place until equilibrium is reached.
2.3.Wettability of oxidized coal
The wettability of coal,which is better described by the degree of oxidation,can also be determined by the electrokinetic properties and contact angle measurements [46].As the hydronium and hydroxyl ions are the potential determining ions for both oxidized and non-oxidized coals,the addition of hydroxyl ions (OH ?)increases the nega-tive charges on the coal surface.Conversely,when the pH of the pulp decreases,the adsorption of hydronium (H 3O +)ions increases on the coal surface until the negative charge gets neutralized and as the acid groups increase,the surface becomes more positive.Hence,concentra-tion of the hydronium and hydroxyl ions present in the pulp not only changes the magnitude but also the sign.Sarikaya and Ozbayoglu [16]carried out the electrokinetic potential (Fig.1)and contact angle mea-surement (Fig.2)for correlating the ?otation recovery on Turkish coal.The Iso-electric point (IEP)of un-oxidized coal was found to be 4.2.As the oxidation increases,IEP decreases and increases the negative value on the surface of coal.The relationship between the electrokinetic potential and surface charge developed during the oxidation for differ-ent length of time at 200°C are shown in Fig.3.When the cationic collectors are used,the IEP's of oxidized coal shift towards the more alkaline pH,i.e.in the range of 9.3to 10.9,depending upon the type and concentration of the collectors.As the oxidized coal have negatively charged surface and the number of hydrophobic sites presence on the surface decreases due to oxidation,it is assumed that the positive amine ions are adsorbed electrostatically on oxidized coal surfaces in a wide range.This shifts the IEP's of oxidized coal towards the higher pH values.Adsorption increases as the concentration of the amine increases.
Vamvuka and Agridiots [47]investigated the behavior of reverse ?o-tation on dif ?cult-to-?oat lignites.They found that the hydrophobicity of these coals can be increased either by reduction of the oxygen functional at the coal surface before the treatment [48],or by using appropriate reagents [34,49].Both ionic and non-ionic surfactants may alter the surface characteristics of these coals.Blending of hydrocarbons and a non-hydrocarbon collector,such as copolymers,long chain amines and fatty acid amides improve the ?oatability [2,50,51,52,54].
2.4.Wettability of oxidized coal in presence of surfactants
It was found that the presence of surfactant with oily collector improves the ?otation of coal.The contact angle for un-oxidized coal in distilled water was found to be 59°.The oxidation of the coal deteriorated the natural ?oatability by reducing the contact angle from 59°to 7°and thus become more readily wetted by water after oxidation.Floatability of lignite was studied using kerosene along with different types of surfactants like cationic,anionic and non-ionic surfactants.The addition of suitable cationic collectors,like fatty alkyl propelene diamine (Flotigam,PA)or alkyl ether amine part of it neutralized by acetic acid (Flotigam,ENA),modi ?es the sur-face charge and increases the contact angle.Even with the oxidation of coal,the contact angle increased up to 75°[55].Cebeci used Acorga M5640(alkyl hydroxyl aryl aldoxime)as an emulsi ?er,Hosta ?ot LIP (sodium dialkyl-dithiophosphate)as anionic and Flotigol CS (mixture of crysylic acids)as non-ionic collectors during ?otation studies.It was found from his study that the combination of both kerosene+emulsi ?er and mixture of kerosene,emulsi ?er,surfactant were stable (except anionic),and easily dispersible in water.It formed very
Z e t a P o t e n t i
a l , m v
pH
Fig.1.Effect of oxidation on zeta potential of coal oxidized at 200°C and at different pH (after [16]).
C o n t a c t a n g l e d e g r e e , θ
Oxidation time, hours
Fig.2.Effect of 200°C oxidation on the contact angle of coal in distilled water and in the presence of 15mg I-1Flotigam PA at pH 7.4(after [16]).
pH
Z e t a P o t e n t i a l ,m v
R e c o v e r y (W t %), C o n t a c t a n g l e , θ
Fig.3.Correlation of the electrokinetic potential and contact angle of oxidized coal and its ?otation response in the presence of Flotigam PA (after [16]).
153
S.Dey /Fuel Processing Technology 94(2012)151–158
small oil droplets compared to the kerosene.It was envisaged that all of the collectors except kerosene investigated in this study increased the?oatability of lignite.However,when the combustible recovery and?otation ef?ciency index were considered,the best results were obtained from the combination of both kerosene–emulsi?er and kerosene–emulsi?er–Flotigol CS(non-ionic).It was expected due to the high binding and spreading tendency of both collectors over the coal surface.The coal concentrates having relatively low ash content were obtained with the kerosene+emulsi?er+non-ionic surfactant. It was further observed that the oxidized coal surface became hydro-phobic after adding Flotigam PA(fatty alkyl propelene diamine),even when the oxidation is extensive.It has been shown that as the contact angle increases,the?otation recoveries also increase.The order of ad-dition of non-ionic surfactant with oily collector plays an important role on the?otation response.Chander et al.[34]observed that the ex-tent of adsorption on coal was expected to vary with dodecane.If the surfactants are added before any collector,it would adsorb on the coal surface,and not be available for emulsi?cation.Addition of surfac-tant before the dodecane lowered the yield.This was attributed to the adsorption of the surfactant molecules on the surface of coal,making the coal hydrophilic.Therefore,the adsorbed surfactants are no longer available for emulsi?cation.Ash rejection was also found to be poor when the surfactant was added prior to the addition of oily collector. They also compared the?otation results of the anionic surfactant with the oily collector.It was found that the yields were very similar for both mode of surfactant addition.The reason for this was attributed to a vast change in the froth characteristics due to this surfactant's well known foaming tendency.The anionic surfactant might have rapidly migrated into the aqueous phase.
Jia et al.[56]performed?otation of low rank/oxidized coal with dodecane,nonyl benzene and nonyl phenol(Table2).Nonyl benzene was found to be a better?otation collector than dodecane for two coals,indicating strong interaction of the benzene ring with aromatic sites on the coal surface.This is due to strong p-bonding between the aromatic component of the coal matrix and the benzene ring of the reagent[22,57].
2.5.Effect of coal particle–promoter interactions on?otation
Promoters act as surface modi?ers and may alter hydrophobicity depending on its concentration and the rank of coal[17,34,41,42,47,58-66].A change in the surface properties of the coal particles largely affects their attachment and detachment characteristics with other dispersed phases in?otation pulp.In the?otation of low rank or oxidized coals with highly negative surfaces in the pH range of3–5,and the use of cat-ionic promoters,enhance the?otation performance[47,67-69].Busta-mante and Woods[70]found that adsorption of dodecylammonium on non-polar parts of the coal surface decreased its hydrophobicity,while the adsorption on the mineral matter caused an increase in hydrophobic-ity.With weathered coal,where both the carbonaceous and the mineral matter were extensively negatively charged,dodecylammonium adsorbed with the polar group interacting with the surface and therefore all types of composite grains became hydrophobic.Non-ionic surfactants (NIS)and water-soluble polymers are found to modify the coal surface.Li et al.[71]used a comb-like polymer and found that the coal became more hydrophobic with increasing promoter concentration regardless of its original?oatability.The triblock poly(ethylene oxide)(PEO)and poly(propylene oxide)(PPO)based systems,PEO-PPO-PEO were also found to improve coal?otation and the mechanism of polymer action was a function of the coal rank[18,41,42,64-66,72].They have amphi-philic characteristics and self-assemble into micelles to form a variety of close packed structures.By varying the block composition(PEO/PPO ratio)and the molecular weight,it is possible to tailor the?nal properties of these systems to meet the speci?c application needs.These reagents had double effect on?otation.They modi?ed the coal surface and also improved the emulsi?cation of the oily collector.For high rank coals, which usually require relatively small amounts of the collector,the sur-face modi?er function of the polymers was dominant over their emulsi-?er function.It is generally accepted that the collector disperses into droplets in the pulp and these droplets collide with,adhere to and spread on the coal particles to render them more hydrophobic.Size distribution of oil droplets depends on dispersion and coalescence sub-processes, which were determined by the intensity of mechanical agitation and presence of promoters and?ne solid particles in the system[42,66,73]. Polat et al.[66]investigated the effect of the addition of the PEO/PPO tri-block copolymeric promoters on the dispersion kinetics of oil(dode-cane).Addition of promoter reduced the size of median oil droplets sig-ni?cantly and the extent of this reduction was a strong function of promoter concentration,as can be seen in Fig.4.
2.6.Flotation of oxidized coals
Most coals are susceptible to weathering or oxidation.With oxida-tion,the number of oxygenated functional groups increases,thus making the coal surface hydrophilic and less amenable to?otation [17,20,74].Cebeci[55]studied the?oatability of Yozgat Ayridam lignite using kerosene and mixture of kerosene,emulsi?er and surfactant
C
HO C
H O)4O C
O CH2O
O
C R
L-64 Conc., M
80
70
60
50
40
30
20
110100
Time, minutes
x
5
,
μ
m
0.1% Dodecane
10-4
10-6
10-8
None
Fig.4.Kinetics of emulsi?cation of n-dodecane(0.1%by volume)at various concentra-
tions of Pluronic acid L-64,a PEO/PPO/PEO tri block polymer(after[52]).
154S.Dey/Fuel Processing Technology94(2012)151–158
(both cationic and anionic).It was shown that a mixture of kerosene and an emulsi?er,and kerosene,emulsi?er and surfactant is easily dispersible in water and produce stable emulsions with smaller oil droplets,when compared to kerosene alone.The effectiveness of the surfactants for?otation of oxidized or sub-bituminous coals was also studied by many researches.The performance of non-ionic surfactant (NIS)is found to be more effective than the cationic(CS)/anionic surfac-tant(AS).The non-ionic surfactants possess effective hydrogen bonding at one end of the alkyl chain which confers on them the required water-solubility.The interaction of the oily collector in the presence of a cationic surfactant that had a polar nature with the coal surface may be due to hydrogen bonding and the electrostatic attraction with the negatively charged coal surface.This type of adhesion would result in a tendency for a residual water?lm to be retained between the coal surface and oil.Therefore,the coal surface would be to a lesser extent, covered with the oil as obtained from NIS.Similarly,the presence of an-ionic collector with oily collector was due to the hydrogen bonding as a result of their polar nature.However,the electrostatic repulsion between the negatively charged oil droplets and coal surface was also indicated.Therefore,the surface of coal would be,to a lesser extent, covered with kerosene.It was also possible that the residual water ?lm remained between the coal surface and kerosene droplets.As a result of the combining of these two effects,the yields were lower than those obtained from NIS[55].This is attributed to the pore pene-tration phenomenon with short chain oils and to insuf?cient spreading of long chain hydrocarbon oils due to viscosity[33].The?otation of this type of coal was carried out also by using derivatives of tetrahydrofuran (THF)as collector[56].The oxidized coal possesses large number of hy-drophilic oxygenated functional groups and it is expected that the THF series might be even more effective as?otation collectors due to the hydrogen bonding between the reagents and the coal surface.This hypothesis was tested by Jia et al.[56]employing two types of coals, i.e.Illinois No.6and Pittsburgh No.8.These two coals were oxidized and?otation tests were carried out using dodecane and some of the THF surfactants as collectors under two fairly similar laboratory condi-tions.Fig.5(A)and Fig(B)present plots of the combustible matter re-covery as a function of collector dosage for the?otation of lab-
oxidized Illinois No.6coal and Pittsburgh No.8respectively.From Fig.5,it is found that recovery of combustible matter is very low when dodecane was used as the collector,but with THF collectors a much lower dosage was required for the same combustible matter.It appears that a higher dosage of dodecane is required to?oat the oxidized coal,whereas a lower dosage of THF-11is required for the ?otation of oxidized coal in comparison to the?otation of as-received coal.These results indicate that the surfactants used have the ability to restore the?oatability of oxidized coal.Harris et al.[22]showed that the tetrahydrofurfuryl butyrate designated(THF-3)is an effective collector for?otation of bituminous coal.These authors indicated that the THF series of reagents might be effective alternatives as collectors in the?otation of both low rank and oxidized coal.Jia et al.[56]investi-gated the ef?cacy of the collecting ability of THF compounds having various hydrocarbon chain con?gurations to function as collectors for the?otation of un-oxidized coals,laboratory-oxidized coals,and natu-rally weathered coals(see Fig.5).The results show that THF-17en is more effective than the other collectors for both coals.The plots also show that surfactants with an oxygenated group are generally more effective than those without one and that nonylbenzene is more effec-tive than dodecane.This indicates that there might be two mechanisms for the interaction between the surfactants and the coal surface.
2.6.1.Mechanism of adsorption
It is known that surface of coal consists of inherently hydrophobic areas and also sites containing oxygenated moieties viz.as carboxyl, carbonyl,phenolic and ester groups[75,76].The?rst mechanism of in-teraction between the surfactants and the coal surface appears to be through the polar groups of the reagent interacting with the oxygenated functional groups on the coal surface by hydrogen bonding. The second mechanism involves the interaction of the non-polar chain with the carbonaceous sites on the coal surface by dispersing water molecules from the coal surfaces.The interaction between an aliphatic chain and the coal surface is less pronounced than that of a benzene ring with the aromatic sites on the coal surface.This may be due to strong p-bonding interaction between the aromatic component of the coal matrix and the benzene ring of the reagent[22,57].Reagents con-taining a benzene ring showed better collecting ability compared to dodecane.This indicates that although the benzene ring has a stronger interaction with the aromatic coal surface than an aliphatic chain,the interaction is not as strong as that between the polar group of the re-agents and the coal surface.This also suggests that hydrogen bonding of the oxygenated groups in the reagents is stronger than the van der Waal interaction of the aliphatic chains with the carbonaceous portions of the surface.This explains why the reagents containing oxygen func-tional groups are much better collectors than hydrocarbon oil,such as dodecane,for the?otation of bituminous coals(Fig.6).It was expected that THF series would adsorb onto the oxygenated surface sites on the coal through hydrogen bonding,hydrophobic bonding of the aliphatic hydrocarbon chain with the hydrophobic sites on the coal surface and p-bonding of the benzene ring on the hydrocarbon chain of the collector with aromatic sites on the coal surface and thus making the subsequent spreading of dodecane on the coal surface more ef?cient.
2.6.2.Collector spreading
Generally coal?otation studies are carried out using oily collectors. The insoluble oils used as collectors for the?otation of coal must spread over the coal surface for effective?otation.If the coal is somewhat Illinois No 6
MIBC 0.52Kg/t
C
o
m
b
u
s
t
i
b
l
e
s
m
a
t
t
e
r
r
e
c
o
v
e
r
y
,
%
100
80
60
40
C
o
m
b
u
s
t
i
b
l
e
s
m
a
t
t
e
r
r
e
c
o
v
e
r
y
,
%
100
80
60
40
0.1110
0.1110
Reagent dosage, Kg/t
Reagent dosage, Kg/t
GH4
Nonyl Phenol
THF-17en
Nonyl Benzene
Dodecane
GH4
Nonyl Phenol
THF-17en
Nonyl Benzene
Dodecane
Pittsburg No. 8 a
b
https://www.doczj.com/doc/d64668111.html,parison of the collecting ability of the nonionic THF-17en with that of nonyl-phenol,GH4,nonylbenzene,and dodecane for the?otation of?74μm Illinois No.6(A) and Pittsburgh No.8coals(B)(after[56]).
155
S.Dey/Fuel Processing Technology94(2012)151–158
oxidized,water molecules will tend to interact with the coal surface,thus reducing the oil/water contact angle and tendency of the oil to spread over the coal surface.The spreading coef ?cient,S O/W for an oil phase displacing water on a solid surface is given by Berg [77]:S o =w ?γow Cos θ?1eT
where,γow is the oil/water interfacial tension and θis the contact angle measured through the oil phase.The spreading coef ?cient is deter-mined by both the contact angle and the oil/water interfacial tension.Polar oils,such as the THF esters,will tend to in ?uence both parameters.The insuf ?cient spreading of long chain hydrocarbon oils is due to the result of high viscosity.During spreading of the oils,the oil droplets displace the interfacial water from the coal surface.As a result of this effect,the stabilization of the oil ?lm is achieved at the coal surface.The number of oil droplets is increased due to the improved dispersion occasioned by the decrease in the oil/water interfacial tension.As a result of this,the energy needed for spreading of the oil over the coal surface is lowered and hydrophobicity of the coal increases.
2.6.
3.Interaction of the oxygenated non-ionic part of collectors on coal surface
The interaction of collectors on coal surface plays an important role in coal ?otation.The interaction energy for different functional groups present within the compound and with the surface of the oxidized or low rank coals are different.In view of the action of the non-ionic surfactants,it is noticed that they are bifunctional:they possess (i)ox-ygenated functional groups and (ii)a hydrocarbon chain.In the case of the THF series of reagents,the oxygenated functional groups them-selves have two components:the tetrahydrofuran (a ring-structured saturated ether)and an ester functionality.Hydrogen bonding plays an important role in determining the physical properties of such
compounds.The simple oxygenated compounds,having signi ?cant sol-ubility in the range of 8parts per 100parts of water,indicate strong hy-drogen bonding with water.Except for diethyl ether (which cannot form hydrogen bond with itself),the relatively high boiling points indi-cate internal hydrogen bonding of molecules with each other.Reduc-tion in the number of carbons by one in the case of butanol to propanol and ethyl methyl ketone to acetone leads to compounds that are completely miscible with water.Furan,a ring-structured 4-carbon unsaturated ether,is insoluble in water and has a boiling point similar to that of diethyl ether.The double bonds in the molecule strongly at-tract the electrons away from the oxygen through resonance interac-tion,thereby eliminating its ability to hydrogen bond.On the other hand,tetrahydrofurfuran,which is simply comprised of a ring-structured saturated alkane,is miscible with water and boils at 66°C,both indicating strong hydrogen bonding capacity.In the tetrahydrofu-ran,the bond angle of the –O –is constrained,increasing the basicity of the oxygen atom [78].On the other hand,tetrahydrofurfuryl acetate is also miscible in water but boils at a high temperature,194°C.The strong tendency of both the ether group and the ester group in the tetrahydrofurfuryl molecule to hydrogen bond must be responsible for hydrogen bonding action with polar sites on the coal surface.In order to reduce their solubility and to give the surfactants an oily char-acter,the hydrocarbon chains of various con ?gurations were intro-duced to the ester functional group on the THF series of reagents.Among intermolecular interactions,hydrogen-bonding is one of the most abundant.The enthalpy of hydrogen bonding between proton donor groups such as OH and NH and the electron donor atoms such ox-ygen and nitrogen is within the range of 3–10kcal/mol [79,80].It is expected that when the coal surface becomes oxidized water molecules interact strongly through hydrogen bonding with the oxygen atoms on the surface,giving rise to hydrophilicity.It was noted that CH/πinterac-tions are the weakest among all the six,lower than CH 2/CH 2,which means that the ?otation of highly aromatic coals with an aliphatic hydrocarbon (dodecane or fuel oil)will not be as effective as in the ?o-tation of less aromatic (more aliphatic)coals,keeping mineral matter and the density of various surface functional groups on the surface con-stant.This may possibly explain why highly aromatic coals exhibit decreased ?oatability with fuel oil.
2.6.4.Structural effect of reagents on ?otation response
The effect of chemical structure of the collectors on the ?otation response of the coal and dosages of the various reagents required for 70%combustible matter recovery were studied by Harris et al.[22]and given in Fig.7A and B.The reagent requirements for Pittsburgh No.8coal (Fig.7A)are much less than for Illinois No.6coal (Fig.7B).The effectiveness of dodecane and nonyl benzene is included for com-parative purposes.With Illinois No.6coal,the amount of dodecane required for adequate ?otation is 50times that of the appropriate THF compounds.The aromatic nonylbenzene is considerably more effective than dodecane.For ?otation of the more hydrophobic Pittsburgh No.8coal,only about a tenth of the amount of dodecane is required in com-parison to the ?otation response of Illinois [9]No.6.The rejection of ash as a function of the combustible matter recovery for the ?otation of ?74μIllinois No.6coal with the various collectors were studied [56,53]and the results are given in Fig.8.It shows that the ash rejection with these non-ionic surfactants over dodecane for the more hydrophil-ic Illinois No.6coal is signi ?cantly higher than more hydrophobic Pitts-burgh No.8coal.The most effective collector for Pittsburgh No.8coal was found to be THF-3,indicating an optimum in the balance between the hydrophobic and hydrophilic part of the collector molecule for the more hydrophobic coal surface.While THF-1has the shortest alkyl chain,miscible with water and even if the hydrogen bonding mecha-nism dominates,its short chain is not long enough to make the coal sur-face more hydrophobic.The ?otation results for both coals indicate that the main role of the polar group of the THF collectors is interaction with polar sites on the coal surface,and non-ionic surfactants can spread on
a
B
α
(A)> α(B)
Hydrophilic Coal
B
α
(A)≈ α(B)
Intermediate Coal
A
B
α(B)> α(A)
Hydrophobic Coal
α(B ′)> α(B)
A B B ′
Fig.6.Schematic representation of interaction between surfactant molecules and coal surface,showing A as polar head and B or B ′as hydrocarbon chain [40].
156S.Dey /Fuel Processing Technology 94(2012)151–158
hydrophilic coal surface more readily than an oily hydrocarbon collec-tor,thereby creating a hydrophobic surface.In case of Pittsburgh No.8coal,the spreading of dodecane on the hydrophobic surface takes place more readily than THF surfactants.
In assessing collector interaction with bituminous coals,it should be noted that the surface of these coals is comprised of aromatic
carbonaceous sites plus oxygenated functional groups (and contained mineral matter).Fig.8shows that the results exhibit distinctly different behavior,depending on the hydrophobicity of the coal and whether the reagents are aliphatic or aromatic.For both coals,the results given in Fig.5show the following for reagent effectiveness:
i.Aromatic hydrocarbon oils are more effective than aliphatic hydrocarbon oil.
ii.Oxygenated non-ionic surfactants are more powerful collectors than hydrocarbon oil.
iii.Oxygenated aliphatic surfactants have better collecting proper-ties than oxygenated aromatic surfactants.
3.Summary
Flotation studies on coal largely depend on its rank.Sometimes even having the maturity,the surface of the coal gets oxidized,changes the surface properties and reduces the hydrophobicity.This change can be investigated by characterizing the oxygenated functional group present on the surface adopting different techniques.It explains the possible type of collector requirement,the type of interaction (physisorption or chemisorpton)to the surface,blending ratio of the collectors and the orientation of the collector molecules.Therefore,depending on the rank of the coal and its hydrophobicity,one or the other of the afore-mentioned interaction mechanisms may be more dominant.Types of surfactant used in ?otation have an impact on performance.The mode of addition of the surfactants also has an important role.The emulsi ?ca-tion of the oily collector by the surfactant is only possible when they are added after the oily collectors.Flotation studies on low rank coal shows dif ?cultly with oily collectors.Flotation results on low rank or laboratory-oxidized coal indicated that it was also dif ?cult to ?oat oxidized coal with dodocane.The PEO –PPO –PEO tri-block copolymers have amphiphilic characteristics and self-assemble into micelles to form a variety of close packed structures.By varying the block composi-tion (PEO/PPO ratio)and the molecular weight,it is possible to improve the coal ?otation.The THF series of reagents have the ability of restoring the ?oatability of oxidized coal through their aptitude to form hydrogen bonds to oxygen functional groups on the oxidized coal surface.Nonyl-benzene was found to be a better ?otation collector than dodecane for the above mentioned low rank coals,indicating strong interaction of the benzene ring with aromatic sites on the coal surface.This type of in-teraction also has an in ?uence on the performance of THF reagents when a benzene ring is incorporated into the collector chain.In partic-ular,?otation is less effective with aromatic THF reagents than with the alkyl analogs,probably because of molecular orientation that results from competition between the benzene ring and the oxygenated func-tional groups for different sites on the coal surface.References
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Pittsburg No.8
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比较级与最高级 1.as...as 与(not) as(so)...as as...as...句型中，as的词性 第一个as是副词，用在形容词和副词的原级前，常译为“同样地”。第二个as是连词，连接与前面句子结构相同的一个句子(相同部分常省略)，可译为“同..... He is as tall as his brother is (tall) . (后面的as 为连词) 只有在否定句中，第一个as才可换为so 改错: He is so tall as his brother.（X） 2.在比较状语从句中，主句和从句的句式结构一般是相同的 与as...as 句式中第二个as一样，than 也是连词。as和than这两个连词后面的从句的结构与前面的句子大部分情况下结构是相同的，相同部分可以省略。 He picked more apples than she did. 完整的表达为: He picked more apples than she picked apples. 后而的picked apples和前面相同，用did 替代。 He walked as slowly as she did.完整表达为: He walked as slowly as she walked slowly. she后面walked slowly与前面相同，用did替代。
3.谓语的替代 在as和than 引导的比较状语从句中，由于句式同前面 主句相同，为避免重复，常把主句中出现而从句中又出现的动词用do的适当形式来代替。 John speaks German as fluently as Mary does. 4.前后的比较对象应一致 不管后面连词是than 还是as,前后的比较对象应一致。The weather of Beijing is colder than Guangzhou. x than前面比较对象是“天气”，than 后面比较对象是“广州”，不能相比较。应改为: The weather of Bejing is colder than that of Guangzhou. 再如: His handwriting is as good as me. 应改为: His handwriting is as good as mine. 5.可以修饰比较级的词 常用来修饰比较级的词或短语有: Much,even,far,a little,a lot,a bit,by far,rather,any,still,a great deal等。 by far的用法: 用于强调，意为“...得多”“最最...”“显然”等，可修饰形容词或副词的比较级和最高级，通常置于其后，但是若比较级或最高级前有冠词，则可置于其前或其后。
The way 的用法 Ⅰ常见用法： 1)the way+ that 2)the way + in which（最为正式的用法） 3)the way + 省略（最为自然的用法） 举例：I like the way in which he talks. I like the way that he talks. I like the way he talks. Ⅱ习惯用法： 在当代美国英语中，the way用作为副词的对格，“the way+ 从句”实际上相当于一个状语从句来修饰整个句子。 1)The way =as I am talking to you just the way I’d talk to my own child. He did not do it the way his friends did. Most fruits are naturally sweet and we can eat them just the way they are—all we have to do is to clean and peel them. 2）The way= according to the way/ judging from the way The way you answer the question, you are an excellent student. The way most people look at you, you’d think trash man is a monster. 3）The way =how/ how much No one can imagine the way he missed her. 4）The way =because
人教版（新目标）初中英语形容词与副词的比较级与最高级 （一）规则变化： 1．绝大多数的单音节和少数双音节词，加词尾-er ，-est tall—taller—tallest 2．以不发音的e结尾的单音节词和少数以-le结尾的双音节词只加-r，-st nice—nicer—nicest , able—abler—ablest 3．以一个辅音字母结尾的重读闭音节词或少数双音节词，双写结尾的辅音字母，再加-er，-est big—bigger—biggest 4．以辅音字母加y结尾的双音节词，改y为i再加-er，-est easy—easier—easiest 5．少数以-er，-ow结尾的双音节词末尾加-er，-est clever—cleverer—cleverest, narrow—narrower—narrowest 6．其他双音节词和多音节词，在前面加more，most来构成比较级和最高级 easily—more easily—most easily （二）不规则变化 常见的有： good / well—better—best ; bad (ly)/ ill—worse—worst ; old—older/elder—oldest/eldest many / much—more—most ; little—less—least ; far—farther/further—farthest/furthest
用法： 1．原级比较：as + adj./adv. +as（否定为not so/as + adj./adv. +as）当as… as中间有名字时，采用as + adj. + a + n.或as + many / much + n. This is as good an example as the other is . I can carry as much paper as you can. 表示倍数的词或其他程度副词做修饰语时放在as的前面 This room is twice as big as that one. 倍数+as+adj.+as = 倍数+the +n.+of Your room is twice as larger as mine. = Your room is twice the size of mine. 2．比较级+ than 比较级前可加程度状语much, still, even, far, a lot, a little, three years. five times,20%等 He is three years older than I (am). 表示“（两个中）较……的那个”时，比较级前常加the（后面有名字时前面才能加冠词） He is the taller of the two brothers. / He is taller than his two brothers. Which is larger, Canada or Australia? / Which is the larger country, Canada or Australia? 可用比较级形式表示最高级概念，关键是要用或或否定词等把一事物（或人）与其他同类事物（或人）相分离 He is taller than any other boy / anybody else.
大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和 -est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音字母然后再加 -er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不 形容词比较级的用法: 形容词的比较级用于两个人或事物的比较,其结构形式如下: 主语+谓语(系动词)+ 形容词比较级+than+ 对比成分。也就是, 含有形容词比较级的主句+than+从句。注意从句常常省去意义上和主句相同的部分, 而只剩下对比的成分。
The way的用法及其含义（二） 二、the way在句中的语法作用 the way在句中可以作主语、宾语或表语： 1.作主语 The way you are doing it is completely crazy.你这个干法简直发疯。 The way she puts on that accent really irritates me. 她故意操那种口音的样子实在令我恼火。The way she behaved towards him was utterly ruthless. 她对待他真是无情至极。 Words are important, but the way a person stands, folds his or her arms or moves his or her hands can also give us information about his or her feelings. 言语固然重要,但人的站姿,抱臂的方式和手势也回告诉我们他(她)的情感。 2.作宾语 I hate the way she stared at me.我讨厌她盯我看的样子。 We like the way that her hair hangs down.我们喜欢她的头发笔直地垂下来。 You could tell she was foreign by the way she was dressed. 从她的穿著就可以看出她是外国人。 She could not hide her amusement at the way he was dancing. 她见他跳舞的姿势，忍俊不禁。 3.作表语 This is the way the accident happened.这就是事故如何发生的。 Believe it or not, that's the way it is. 信不信由你, 反正事情就是这样。 That's the way I look at it, too. 我也是这么想。 That was the way minority nationalities were treated in old China. 那就是少数民族在旧中
英语比较级和最高级的用法归纳 在学习英语过程中，会遇到很多的语法问题，比如比较级和最高级的用法，对于 这些语法你能够掌握吗？下面是小编整理的英语比较级和最高级的用法，欢迎阅读！ 英语比较级和最高级的用法 一、形容词、副词的比较级和最高级的构成规则 1.一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级 在后面加-est; (1)单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest (2)双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2.以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st; 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3.在重读闭音节(即：辅音+元音+辅音)中，先双写末尾的辅音字母，比较级加-er，最高级加-est; 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4.以“辅音字母+y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est; 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5.其他双音节词和多音节词，比较级在前面加more，最高级在前面加most; 如：bea utiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily 注意：(1)形容词最高级前通常必须用定冠词 the，副词最高级前可不用。 例句： The Sahara is the biggest desert in the world. (2) 形容词most前面没有the，不表示最高级的含义，只表示"非常"。 It is a most important problem. =It is a very important problem.
定冠词the的用法： 定冠词the与指示代词this ,that同源,有“那(这)个”的意思,但较弱,可以和一个名词连用,来表示某个或某些特定的人或东西. (1)特指双方都明白的人或物 Take the medicine.把药吃了. (2)上文提到过的人或事 He bought a house.他买了幢房子. I've been to the house.我去过那幢房子. (3)指世界上独一无二的事物 the sun ,the sky ,the moon, the earth (4)单数名词连用表示一类事物 the dollar 美元 the fox 狐狸 或与形容词或分词连用,表示一类人 the rich 富人 the living 生者 (5)用在序数词和形容词最高级,及形容词等前面 Where do you live?你住在哪? I live on the second floor.我住在二楼. That's the very thing I've been looking for.那正是我要找的东西. (6)与复数名词连用,指整个群体 They are the teachers of this school.(指全体教师) They are teachers of this school.(指部分教师) (7)表示所有,相当于物主代词,用在表示身体部位的名词前 She caught me by the arm.她抓住了我的手臂. (8)用在某些有普通名词构成的国家名称,机关团体,阶级等专有名词前 the People's Republic of China 中华人民共和国 the United States 美国 (9)用在表示乐器的名词前 She plays the piano.她会弹钢琴. (10)用在姓氏的复数名词之前,表示一家人 the Greens 格林一家人(或格林夫妇) (11)用在惯用语中 in the day, in the morning... the day before yesterday, the next morning... in the sky... in the dark... in the end... on the whole, by the way...
More than的用法 A. “More than+名词”表示“不仅仅是” 1)Modern science is more than a large amount of information. 2)Jason is more than a lecturer; he is a writer, too. 3) We need more than material wealth to build our country.建设我们国家，不仅仅需要物质财富. B. “More than+数词”含“以上”或“不止”之意，如： 4)I have known David for more than 20 years. 5)Let's carry out the test with more than the sample copy. 6) More than one person has made this suggestion. 不止一人提过这个建议. C. “More than+形容词”等于“很”或“非常”的意思，如： 7)In doing scientific experiments, one must be more than careful with the instruments. 8)I assure you I am more than glad to help you. D. more than + (that)从句，其基本意义是“超过（=over）”，但可译成“简直不”“远非”.难以，完全不能（其后通常连用情态动词can） 9) That is more than I can understand . 那非我所能懂的. 10) That is more than I can tell. 那事我实在不明白。 11) The heat there was more than he could stand. 那儿的炎热程度是他所不能忍受的 此外，“more than”也在一些惯用语中出现，如： more...than 的用法 1. 比……多，比……更 He has more books than me. 他的书比我多。 He is more careful than the others. 他比其他人更仔细。 2. 与其……不如 He is more lucky than clever. 与其说他聪明，不如说他幸运。 He is more （a）scholar than （a）teacher. 与其说他是位教师，不如说他是位学者。 注：该句型主要用于同一个人或物在两个不同性质或特征等方面的比较，其中的比较级必须用加more 的形式，不能用加词尾-er 的形式。 No more than/not more than 1. no more than 的意思是“仅仅”“只有”“最多不超过”，强调少。如： --This test takes no more than thirty minutes. 这个测验只要30分钟。 --The pub was no more than half full. 该酒吧的上座率最多不超过五成。-For thirty years，he had done no more than he （had）needed to. 30年来，他只干了他需要干的工作。 2. not more than 为more than （多于）的否定式，其意为“不多于”“不超过”。如：Not more than 10 guests came to her birthday party. 来参加她的生日宴会的客人不超过十人。 比较： She has no more than three hats. 她只有3顶帽子。（太少了） She has not more than three hats. 她至多有3顶帽子。（也许不到3顶帽子） I have no more than five yuan in my pocket. 我口袋里的钱最多不过5元。（言其少） I have not more than five yuan in my pocket. 我口袋里的钱不多于5元。（也许不到5元） more than, less than 的用法 1. （指数量）不到，不足 It’s less than half an hour’s drive from here. 开车到那里不到半个钟头。 In less than an hour he finished the work. 没要上一个小时，他就完成了工作。 2. 比……（小）少 She eats less than she should. 她吃得比她应该吃的少。 Half the group felt they spent less than average. 半数人觉得他们的花费低于平均水平。 more…than,/no more than/not more than (1)Mr．Li is ________ a professor; he is also a famous scientist． (2)As I had ________ five dollars with me, I couldn’t afford the new jacket then． (3)He had to work at the age of ________ twelve． (4)There were ________ ten chairs in the room．However, the number of the children is twelve． (5)If you tel l your father what you’ve done, he’ll be ________ angry． (6)－What did you think of this novel? －I was disappointed to find it ________ interesting ________ that one． 倍数表达法 1. “倍数+形容词（或副词）的比较级+than+从句”表示“A比B大（长、高、宽等）多少倍” This rope is twice longer than that one.这根绳是那根绳的三倍（比那根绳长两倍）。The car runs twice faster than that truck.这辆小车的速度比那辆卡车快两倍（是那辆卡车的三倍）。 2. “倍数+as+形容词或副词的原级+as+从句”表示“A正好是B的多少倍”。
“tｈｅwａｙ+从句”结构的意义及用法 首先让我们来看下面这个句子: Ｒead the foｌloｗｉnｇpassagｅａnd talkａbout ｉt wi ｔh your classmaｔes．Try tｏｔeｌl whaｔyｏu thiｎk ｏf Tom aｎd ｏｆｔhe ｗay the chiｌｄrenｔrｅated ｈim. 在这个句子中，ｔhe waｙ是先行词,后面是省略了关系副词that或in whｉch的定语从句。 下面我们将叙述“the ｗaｙ+从句”结构的用法。 1.tｈe wａy之后，引导定语从句的关系词是tｈat而不是hoｗ,因此，<<现代英语惯用法词典＞＞中所给出的下面两个句子是错误的：Ｔhｉs is ｔｈeｗayｈowｉtｈａppened. This is the way how he ａlwａｙs treats me. 2．在正式语体中,thaｔ可被in which所代替;在非正式语体中，ｔhat则往往省略。由此我们得到theｗay后接定语从句时的三种模式：1) tｈe ｗaｙ＋ｔhａt-从句２）the way +ｉn whiｃh－从句3) the ｗay +从句 例如：Ｔｈe way(in whiｃh ，thａt) ｔhｅｓｅｃomｒade ｓloｏｋａｔｐrobｌems is wrong．这些同志看问题的方法
不对。 Ｔｈｅｗａy(that ,ｉn ｗhiｃh)yoｕ’ｒe doinｇit is comple ｔeｌy crａzy.你这么个干法,简直发疯。 Wｅａdmiｒｅd him for thｅｗay ｉｎｗhｉch he fａｃeｓdiｆficultieｓ． Waｌlａｃe ａｎd Ｄarwiｎｇreed ｏn the way ｉｎwhi ｃh ｄｉfｆｅrｅnt forms ｏf life had ｂegｕn.华莱士和达尔文对不同类型的生物是如何起源的持相同的观点。 Thｉs is ｔｈe ｗaｙ（tｈａｔ) hｅdｉd it. I lｉkeｄｔhe waｙ(ｔhat) ｓｈeｏｒganized ｔhe ｍeetｉng． 3.theｗay(tｈat)有时可以与hｏw(作“如何”解）通用。例如： That’s tｈe ｗaｙ(tｈaｔ) shｅspoke. = Tｈat’s how shｅspoke.
初中英语比较级和最高级讲解与练习 形容词比较级和最高级 一．绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 1. 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 2. 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基 础上变化的。分为规则变化和不规则变化。 二．形容词比较级和最高级规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加-er 和-est 构成。 great (原级) greater(比较级) greatest(最高级) 2) 以-e 结尾的单音节形容词的比较级和最高级是在词尾加-r 和-st 构成。 wide (原级) wider (比较级) widest (最高级) 3) 少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和-est构成。 clever(原级) cleverer(比较级) cleverest(最高级)， slow(原级) slower(比较级) slowest (最高级) 4) 以-y 结尾,但-y 前是辅音字母的形容词的比较级和最高级是把-y 去掉,加上-ier 和-est 构成. happy (原形) happier (比较级) happiest (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该 辅音字母然后再加-er和-est。 原形比较级最高级原形比较级最高级 big bigger biggest hot hotter hottest red redder reddest thin thinner thinnest 6) 双音节和多音节形容词的比较级和最高级需用more 和most 加在形容词前面来构 成。 原形比较级最高级 careful careful more careful most careful difficult more difficult most difficult delicious more delicious most delicious 7)常用的不规则变化的形容词的比较级和最高级: 原级比较级最高级 good better best 好的 well better best 身体好的 bad worse worst 坏的 ill worse worst 病的 many more most 许多 much more most 许多 few less least 少数几个 little less least 少数一点儿 （little littler littlest 小的） far further furthest 远（指更进一步，深度。亦可指更远） far farther farthest 远（指更远，路程）
表示“方式”、“方法”，注意以下用法： 1.表示用某种方法或按某种方式，通常用介词in(此介词有时可省略)。如： Do it (in) your own way. 按你自己的方法做吧。 Please do not talk (in) that way. 请不要那样说。 2.表示做某事的方式或方法，其后可接不定式或of doing sth。 如： It’s the best way of studying [to study] English. 这是学习英语的最好方法。 There are different ways to do [of doing] it. 做这事有不同的办法。 3.其后通常可直接跟一个定语从句(不用任何引导词)，也可跟由that 或in which 引导的定语从句，但是其后的从句不能由how 来引导。如： 我不喜欢他说话的态度。 正：I don’t like the way he spoke. 正：I don’t like the way that he spoke. 正：I don’t like the way in which he spoke. 误：I don’t like the way how he spoke. 4.注意以下各句the way 的用法： That’s the way (=how) he spoke. 那就是他说话的方式。 Nobody else loves you the way(=as) I do. 没有人像我这样爱你。 The way (=According as) you are studying now, you won’tmake much progress. 根据你现在学习情况来看，你不会有多大的进步。 2007年陕西省高考英语中有这样一道单项填空题： ——I think he is taking an active part insocial work. ——I agree with you_____. A、in a way B、on the way C、by the way D、in the way 此题答案选A。要想弄清为什么选A，而不选其他几项，则要弄清选项中含way的四个短语的不同意义和用法，下面我们就对此作一归纳和小结。 一、in a way的用法 表示：在一定程度上，从某方面说。如： In a way he was right.在某种程度上他是对的。注：in a way也可说成in one way。 二、on the way的用法 1、表示：即将来(去)，就要来(去)。如： Spring is on the way.春天快到了。 I'd better be on my way soon.我最好还是快点儿走。 Radio forecasts said a sixth-grade wind was on the way.无线电预报说将有六级大风。 2、表示：在路上，在行进中。如： He stopped for breakfast on the way.他中途停下吃早点。 We had some good laughs on the way.我们在路上好好笑了一阵子。 3、表示：(婴儿)尚未出生。如： She has two children with another one on the way.她有两个孩子，现在还怀着一个。 She's got five children，and another one is on the way.她已经有5个孩子了，另一个又快生了。 三、by the way的用法
形容词比较级和最高级的形式 一、形容词比较级和最高级的构成 形容词的比较级和最高级变化形式规则如下 构成法原级比较级最高级 ①一般单音节词末尾加 er 和 est strong stronger strongest ②单音节词如果以 e结尾，只加 r 和 st strange stranger strangest ③闭音节单音节词如末尾只有一个辅音字母， 须先双写这个辅音字母，再加 er和 est sad big hot sadder bigger hotter saddest biggest hottest ④少数以 y, er(或 ure), ow, ble结尾的双音节词， 末尾加 er和 est(以 y结尾的词，如 y前是辅音字母， 把y变成i，再加 er和 est，以 e结尾的词仍 只加 r和 st) angry Clever Narrow Noble angrier Cleverer narrower nobler angriest cleverest narrowest noblest ⑤其他双音节和多音节词都在前面加单词more和most different more different most different 1) The most high 〔A〕mountain in 〔B〕the world is Mount Everest，which is situated 〔C〕in Nepal and is twenty nine thousand one hundred and fourty one feet high 〔D〕 . 2) This house is spaciouser 〔A〕than that 〔B〕white 〔C〕one I bought in Rapid City，South Dakota 〔D〕last year. 3) Research in the social 〔A〕sciences often proves difficulter 〔B〕than similar 〔C〕work in the physical 〔D〕sciences. 二、形容词比较级或最高级的特殊形式：
比较级和最高级 1.在形容词词尾加上―er‖ ―est‖ 构成比较级、最高级： bright（明亮的）—brighter—brightest broad（广阔的）—broader—broadest cheap（便宜的）—cheaper—cheapest clean（干净的）—cleaner—cleanest clever（聪明的）—cleverer—cleverest cold（寒冷的）—colder—coldest cool（凉的）—cooler—coolest dark（黑暗的）—darker—darkest dear（贵的）—dearer—dearest deep（深的）—deeper—deepest fast（迅速的）—faster—fastest few（少的）—fewer—fewest great（伟大的）—greater—greatest hard（困难的,硬的）—harder—hardest high（高的）—higher—highest kind（善良的）—kinder—kindest light（轻的）—lighter—lightest long（长的）—longer—longest loud（响亮的）—louder—loudest low（低的）—lower—lowest near（近的）—nearer—nearest new（新的）—newer—newest poor（穷的）—poorer—poorest quick（快的）—quicker—quickest quiet（安静的）—quieter—quietest rich（富裕的）—richer—richest short（短的）—shorter—shortest slow（慢的）—slower—slowest small（小的）—smaller—smallest smart（聪明的）—smarter—smartest soft（柔软的）—softer—softest strong（强壮的）—stronger—strongest sweet（甜的）—sweeter—sweetest tall（高的）-taller-tallest thick（厚的）—thicker—thickest warm（温暖的）—warmer—warmest weak（弱的）—weaker—weakest young（年轻的）—younger—youngest 2.双写最后一个字母,再加上―er‖ ―est‖构成比较级、最高级： big（大的）—bigger—biggest fat（胖的）—fatter—fattest hot（热的）—hotter—hottest red（红的）—redder—reddest sad（伤心的）—sadder—saddest thin（瘦的）—thinner—thinnest wet（湿的）—wetter—wettest mad（疯的）—madder—maddest 3.以不发音的字母e结尾的形容词,加上―r‖ ―st‖ 构成比较级、最高级：able（能干的）—abler—ablest brave（勇敢的）—braver—bravest close（接近的）—closer—closest fine（好的,完美的）—finer—finest large（巨大的）—larger—largest late（迟的）—later—latest nice（好的）—nicer—nicest ripe（成熟的）—riper—ripest
The way的用法及其含义（一） 有这样一个句子：In 1770 the room was completed the way she wanted. 1770年，这间琥珀屋按照她的要求完成了。 the way在句中的语法作用是什么？其意义如何？在阅读时，学生经常会碰到一些含有the way 的句子，如：No one knows the way he invented the machine. He did not do the experiment the way his teacher told him.等等。他们对the way 的用法和含义比较模糊。在这几个句子中，the way之后的部分都是定语从句。第一句的意思是，“没人知道他是怎样发明这台机器的。”the way的意思相当于how；第二句的意思是，“他没有按照老师说的那样做实验。”the way 的意思相当于as。在In 1770 the room was completed the way she wanted.这句话中，the way也是as的含义。随着现代英语的发展，the way的用法已越来越普遍了。下面，我们从the way的语法作用和意义等方面做一考查和分析： 一、the way作先行词，后接定语从句 以下3种表达都是正确的。例如：“我喜欢她笑的样子。” 1. the way+ in which +从句 I like the way in which she smiles. 2. the way+ that +从句 I like the way that she smiles. 3. the way + 从句(省略了in which或that) I like the way she smiles. 又如：“火灾如何发生的，有好几种说法。” 1. There were several theories about the way in which the fire started. 2. There were several theories about the way that the fire started.
英语语法---比较级和最高级的用法 在英语中通常用下列方式表示的词:在形容词或副词前加more(如 more natural,more clearly )或加后缀 -er(newer,sooner )。典型的是指形容词或副词所表示的质、量或关系的增加。英语句子中，将比较两个主体的方法叫做“比较句型”。其中，像“A比B更……”的表达方式称为比较级；而“A最……”的表达方式则称为最高级。组成句子的方式是将形容词或副词变化成比较级或最高级的形态。 一、形容词、副词的比较级和最高级的构成规则 1．一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est； （1）单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest （2）双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2．以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st； 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3．在重读闭音节（即：辅音＋元音＋辅音）中，先双写末尾的辅音字母，比较级加-er，最高级加-est； 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4．以“辅音字母＋y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est； 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5．其他双音节词和多音节词，比较级在前面加more，最高级在前面加most； 如：beautiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily