Adsorption kinetics for the removal of chromium(VI) from aqueous solution by adsorbents derived from used tyres and sawdust

The batch removal of hexavalent chromium (Cr(Vl)) from wastewater under dif ferent experimental conditions using economic adsorbents was investigated i n this study. These adsorbents were produced from the pyrolysis and activat ion of the waste tyres (TAC) and from the pyrolysis of sawdust (SPC). The p erformance of these adsorbents against commercial activated carbon F400 (CA C) has also been carried out. The removal was favoured at low pH, with maxi mum removal at pH = 2 for all types of carbon. The effects of concentration , temperature and particle size have been reported. All sorbents were found to efficiently remove Cr(VI) from solution. The batch sorption kinetics have been tested for a first-order reversible r eaction, a first-order and second-order reaction. The rate constants of ads orption for all these kinetic models have been calculated. The applicabilit y of the Langmuir isotherm for the present system has been tested at differ ent temperatures. The thermodynamic parameters (AGO, K,) obtained indicate the endothermic nature of Cr(Vl) adsorption on TAC, SPC and CAC. (C) 2001 E lsevier Science B.V. All rights reserved.