Adsorption performance of cadmium onto shell powder
To study the adsorption mechanisms and the optimum adsorption conditions of Cd2+onto shell powder, batch experiments were conducted to investigate the effects of initial Cd2+concentration, adsorbent dose, pH, temperature, time, and ionic strength on Cd2+adsorption onto the shell powder. The results showed that the adsorption of Cd2+onto the shell powder rapidly increased and then decreased gradually with the increase of sorption agent under different initial Cd2+concentration, and the adsorption fitted well to pseudo-first-order and pseu-do-second-order kinetics. The isothermal adsorption was well described by the Temkin isotherm and the Langmuir isotherm. The adsorption process of Cd2+was a spontaneous and endothermic reaction that achieved adsorption equilibrium in only 30 min, and the maximum equilib-rium adsorption capacity was 161.75 mg·g-1. The adsorption of Cd2+onto the shell powder increased with increasing pH, and then stabilized when the pH was≥5. With increasing concentrations of Ca2+and Mg2+, the adsorption properties of the shell powder gradually decreased, with maximum reductions of 15.19%and 14.44%, respectively, compared with the control group.
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