Mordanting of mercury on styrene-divinylbenzene copolymer beads from aqueous solutions

摘要

The sorption of mercury ions from aqueous solutions on styrene-divinylbenzene copolymer beads (St-DVB) has been investigated for the decontamination of mercury from aqueous media. Various physico-chemical parameters, such as selection of appropriate electrolyte, contact time, amount of adsorbent, concentration of adsorbate, effect of diverse ions and temperature were optimized to simulate the best conditions which can be used to decontaminate mercury from aqueous media using St-DVB beads as an adsorbent. The radiotracer technique was used to determine the distribution of mercury. The highest adsorption was observed at 0.001 mol L-1 acid solutions (HNO3, H2SO4 and HClO4) using 0.2 g of adsorbent for 5.14×10-5mol L-1 mercury concentration in five minutes equilibration time. Studies show that the adsorption decreases with the increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the mercury concentration range of 2.19×10-4 to 5.90×10-3mol L-1. The characteristic Freundlich constants, i.e. 1 = 0.42±0.01 and A = (1.54±0.03)×10-3mol g-1 have been computed for the sorption system. The sorption mean free energy from Dubinin–Radushkevich isotherm is 11.9±0.1 kJ mol-1 indicating ion-exchange mechanism of chemisorption. The uptake of mercury increases with the rise in temperature. Thermodynamic parameters, i.e. ΔG, ΔS and ΔH have also been calculated for the system.