Microwave treated activated carbon from industrial waste lignin for endosulfan adsorption

BACKGROUND: Disposal of large amounts of recurring industrial waste lignin is a big problem for the paper industries and there is need for a rational alternative to utilize this waste lignin. Thus highly porous activated carbons (ACs) were prepared from lignin using H3PO4 as an activating chemical with and without microwave treatment in a self-generated environment at 600 degrees C and the influence of different types of impregnation on the adsorption-desorption capacities of endosulfan from a liquid phase was studied. RESULT: The maximum adsorption capacities (X-m) for ACs prepared by a microwave treatment and using a simple impregnation method were 6.2422 mg g(-1) and 3.9557 mg g(-1), respectively. Equilibrium adsorption time determined from kinetic experiments was 5 h and the experimental kinetic data were described by a pseudo-second-order rate model. Surface characteristics and desorption patterns showed considerable difference between the two ACs with the microwave treated AC showing less hysteresis, greater X-m and established overall superiority over the other. CONCLUSION: Use of microwave treatment produced more oxygen surface functional groups. Results indicate that surface chemistry of the microwave treated sample is more important than the textural properties for the higher adsorption of endosulfan. The microwave treated sample also resulted in less hysteresis and fewer carbonyl surface groups. Desorption patterns cannot be predicted from adsorption alone. (C) 2011 Society of Chemical Industry