Study Of Cadmium Removal From Aqueous Solution By Steel Slag

Cadmium is a non-essential element of human and has biological toxicity, when it accumulated in the human body by long-term intake can lead respiratory tract, liver, kidney and other diseases. But at the same time, cadmium as an industrial raw material and catalyst has been widely used in various industries. Therefore, in order to avoid the occurrence of cadmium pollution, the cadmium wastewater must be treated to meet the standards before being discharged.Steel slag is a molten slag discharged from the steelmaking process and has been treated as solid waste. Chemical, XRD, SEM and BET analysis shows that the main component of the steel slag is CaO. So the steel slag has chemical precipitation of cadmium ions in aqueous solution by its alkaline. In addition, with a rough and porous surface, the steel slag has certain adsorption capacity. Therefore, choose the steel slag to process the water containing cadmium, and optimize the operating conditions and explore the mechanism.In this study, the operating conditions of Cd2+removal from water by steel slag has been compared and optimized by single-factor, orthogonal, dynamic and comparative experiment methods. The results show that reaction time, dosage and particle size of steel slag has more influence on the results, and the removal effect is better while reaction time longer, dosage greater or particle smaller. Dynamic experiment’s result shows the penetration and depletion time of steel slag is inversely proportional to the influent concentration. At the influent concentration of100mg/L, the penetration time is58h and depletion time is82h, while they’re30h and62h respectively at the influent concentration of500mg/L. By comparing steel slag and activated carbon powder for Cd2+removal performance shows that, the removal ability of steel slag is better the activated carbon powder with the removal rate of79.5%.The mechanism of cadmium removal from water by steel slag has been discussed, and corresponding mathematical models were also been established. The reaction phenomenon, XRD and SEM analysis proved that chemical precipitation exists in the reaction and the main precipitate is Cd(OH)2. And use the pseudo-second-order kinetic and Langmuir isotherm models to fit the reaction results to know that, the adsorption rate of steel slag is controlled by chemical adsorption mechanism and the adsorption form is belong to monolayer adsorption.