A modified lignin adsorbent for the removal of 2,4,6-trinitrotoluene

Waste water containing 2,4,6-trinitrotoluene (TNT) in industrial production has caused many serious environmental problems worldwide. In this paper, a novel modified lignin adsorbent for TNT, aminated lignin (AmL) was synthesized by a two-step approach. The characterization using FTIR, SEM and XPS suggested that modification of the lignin was successful. Batch adsorption experiments of AmL for TNT were performed on factors of contact time, temperature, initial TNT concentration, initial pH and adsorbent dosage. The results show that the adsorption equilibrium can be achieved in 24h and the adsorption kinetics is well described by pseudo-second-order model. It was found that the equilibrium data was better represented by the Freundlich isotherm model and the saturated adsorption capacities reach a maximum of 55.7 mg/g at pH 7.0. Thermodynamic parameters were also evaluated and their values indicated that adsorption of TNT on AmL is an endothermic process and spontaneous in nature. The pH plays a key role in TNT adsorption capacity using AmL. The reusability characteristic has been also investigated and more than 95% recovery was obtained after 8 desorption-adsorption cycles for ethanol eluent. The results showed that the synthesized material is a promising sorbent of TNT in water. (C) 2011 Elsevier BY. All rights reserved.