Removal of benzene, toluene and xylene from aqueous solution using activated carbon

Abstract

As the objective of the present work is to maximize the adsorption of Benzene (B), Toluene (T) and Xylene (X) through adsorption using activated carbon (AC), six different ACs were utilized for investigating the removal of BTX. The highest adsorption capacity corresponds to AC C38 with the respective values of being 222mg/g for Benzene, 278mg/g for Toluene and 89mg/g for Xylene, which could be attributed to the higher π-π interactions compared to other AC. The surface modifications were rendered through different treatment techniques and characterized through the variation in the acid/base functional groups. Among the various ACs tested, sample C38 was found to be the most basic carbon with a pH of 9.49 and pH PZC of 11.40, with the acidic functional groups being the lowest at 1.203mmol/g. The BET surface area of C38 was determined to be 1129m2/g, total pore volume 0.649cm3/g, micropore volume 0.396cm3/g and mesopore volume 0.253cm 3/g. The adsorption isotherms were established for all the AC samples covering an adsorption temperature of 30°C to 50°C, while the adsorption kinetics was established only for the sample C38, as it exhibited the highest equilibrium adsorption capacity. The adsorption capacity decreased with increase in the adsorption temperature evidencing the adsorption process to be exothermic. The adsorption isotherms were tested with the various adsorption models such as Freundlich, Langmuir and Dubinin-Radushkevich (DR) models. The adsorption isotherms agreed well with the Freundlich model and the model parameters were evaluated. The kinetics of BTX adsorption was experimentally established at two different temperatures of 30°C and 50°C, which were tested with different kinetic models such as the pseudo-first order, pseudo-second order and intra-particle diffusion models. The pseudo-second order model was found to closely relate with the experimental data and the rate constant was calculated to be 3.24x10 -3g/mg.hr, 4.32 x10-3g/mg.hr and 1.30 x10-2 g/mg.hr at 30°C for BTX, respectively, while the activation energy for their adsorption was 47.2kJ/mol, 21.8kJ/mol and 17.2kJ/mol, respectively. Additionally, the thermodynamic parameters such as the change in enthalpy, entropy and Gibbs free energy were estimated using the van't Hoff equation. The adsorption of BTX was found to be spontaneous and exothermic in nature and resulted in a loss of entropy.

Date of Award	2013
Original language	American English
Supervisor	C. S. Kannan (Supervisor)