Behaviour of activated carbons with different pore size distributions and surface oxygen groups for benzene and toluene adsorption at low concentrations
M.A.Lillo-Ro
´denas *,D.Cazorla-Amoro ´s,A.Linares-Solano Departamento de Quı
´mica Inorga ´nica,Universidad de Alicante,Apartado 99,E-03080Alicante,Spain Received 28October 2004;accepted 17February 2005
Available online 21March 2005
Abstract
This paper deals with the study of the effect that the porosity and the surface chemistry of the activated carbons have on the adsorption of two VOC (benzene and toluene)at low concentration (200ppmv).In this sense,activated carbons with very different porosities and contents in oxygen surface groups have been tested.Our results regarding the effect of the porosity show that the volume of narrow micropores (size <0.7nm)seems to govern the adsorption of VOC at low concentration,specially for benzene adsorption.Regarding the surface chemistry,AC with low content in oxygen surface groups have the best adsorption capacities.Among the AC tested,those prepared by chemical activation with hydroxides exhibit the higher adsorption capacities for VOC.The adsorption capacities achieved are higher than those previously shown in the literature for these conditions,specially for tol-uene.Adsorption capacities as high as 34g benzene/100g AC or 64g toluene/100g AC have been achieved.Ó2005Elsevier Ltd.All rights reserved.
Keywords:Activated carbon;Adsorption;Porosity;Surface properties
1.Introduction
VOC are pollutants present in gas and/or liquid streams of many industrial applications.They are very harmful for both human health and environment,even at very low concentrations [1–6].It can be remarked that they are:(1)agents that destroy the ozone stratospheric layer,(2)precursors of photochemical oxidants,(3)agents of the acid rain,(4)elements of the climatic change,(5)agents that affect the nervous system and (6)carcinogenic and mutagenic agents.
For all these reasons,a considerable effort has been dedicated in the last years regarding their removal.
The most important methods used for treating VOC
gaseous streams are [3,7]:(i)absorption,(ii)adsorption,(iii)condensation,(iv)thermal oxidation and (v)cata-lytic oxidation.All these methods provide good results when using the appropriate conditions of concentration,flow and temperature.
Many of the gaseous streams involved in industrial processes contain VOC at very low concentrations.Both legislation and human health determine that these streams must be treated to remove the organic com-pounds.Considering the low concentration of the VOC in the streams,adsorption is one of the techniques which provides better results [2,3,7,8].
The adsorption of organic pollutants can be carried out employing different adsorbents.Among them,acti-vated carbons are one of the best options due to their hydrophobic properties and their high surface
area
Carbon 43(2005)
1758–1767
/locate/carbon
0008-6223/$-see front matter Ó2005Elsevier Ltd.All rights reserved.doi:10.1016/j.carbon.2005.02.023
*
Corresponding author.Tel.:+34965909350;fax:+34965903454.
E-mail address:mlillo@ua.es (M.A.Lillo-Ro
´denas).
