Parametric and kinetic studies on biosorption of mercury using modified Phoenix dactylifera biomass

Biosorption of mercury was investigated using protonated Phoenix dactylifera biomass as the adsorbent under batch conditions. The dependence of metal removal efficiency on process parameters such as pH, sorbent dose, initial mercury concentration, agitation speed, temperature competitive ion concentration and particle size was studied. The zero point charge of the adsorbent was estimated. The optimal pH and sorbent dose were found to be 7.0 and 3.0 g/L, respectively, and the removal efficiency attained was 92% with an equilibrium removal time of 180 min. The removal efficiency increased with increase in sorbent dose due to the availability of more surface sites. High initial concentration of metal was found to have an inhibitory effect on metal removal. The sorption process was identified as endothermic in nature. The optimal speed of agitation was found as 300 rpm and the metal uptakes were found to decrease with increase in sorbent particle size. Pseudo-second-order model was found to represent the kinetic experiments very well with higher values of R-2 (>0.95). The pseudo-second-order kinetic constants, namely equilibrium uptake (q(e)) and rate constant (k(2)), were evaluated as 46.73 mg/g and 1.87 g/(mg min) at an initial mercury concentration of 100 mg/L. (C) 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.