Removal of lignin and tannin colour from aqueous solution by adsorption onto activated charcoal

Sorptive uptake of lignin and tannin from an aqueous phase by activated charcoal was investigated in the laboratory. The sorption reaction was found to be of a first order. The influence on the rate of sorption of various factors, such as amount of sorbent and pH of the system, have been investigated. Sorption data fit well into the Langmuir adsorption isotherm, indicating formation of a monolayer over a homogeneous sorbent surface. Sorption capacity, rate constant, intraparticle diffusion coefficient, etc. were calculated from the sorption data. Desorption studies indicate the irreversible nature of the sorption reaction, whereas interruption studies suggest film diffusion to be rate limiting.