Carboxylated cellulose for adsorption of Hg(II) ions from contaminated water: isotherms and kinetics

Microcrystalline cellulose (MCC) was modified with 1, 2, 3, 4-butanetetracarboxylic acid (BTCA) to obtain the adsorbent material named treated microcrystalline cellulose (TMCC), which was characterized for point of zero charge (pHZPC), estimation of carboxyl group content and surface group moieties, surface morphology and textural properties. Application of TMCC for the removal of Hg(II) ions from aqueous solution was studied with respect to carboxyl group content, and process parameters, including adsorbent dose, initial solution pH, temperature, contact time, and Hg(II) ion concentration, to provide information about the adsorption mechanism. Isothermal adsorption data were analysed using a range of two and three parameter adsorption models, with the level of fit determined using nonlinear regression analysis. The maximum adsorption capacity under optimised conditions was determined using Langmuir analysis and found to be 1140 mg/g, and Freundlich analysis showed that adsorption of Hg(II) ions onto TMCC is favourable. The kinetic results using a range of models, showed that a pseudo-second order kinetic model was most appropriate for the data obtained, which indicates that the process involves chemisorption. The results obtained show TMCC to have a high affinity for Hg(II) ions from aqueous media, which suggests that these materials may have potential for application in water treatment systems.