Individual And Competition Adsorption Of P, Cr(Ⅵ) And Tannicacid By Synthetic Fe(Ⅲ)-A(Ⅲ) Hydroxide

Chromium could directly and indirectly endanger human health when Cr-contaminated water was used as drinking water or for irrigation. Cr(Ⅵ) was much more toxic and carcinogenic for organism than Cr(Ⅲ), so the maximum level permitted of Cr(Ⅵ) was 0.05 mg/L in wastewater. Chromium and P were found in natural waters. Compared with physical and biological treatment, adsorption was widely used for P and Cr(Ⅵ) removal. So further investigation of the influence each other between P and Cr(Ⅵ) in the adsorption process was required.Loading tannic acid (TA) onto Fe(Ⅲ)-Al(Ⅲ) hydroxide was conducted to study the adsorption and competitive adsorption between phosphate (P) and Cr(Ⅵ). The amount of individual adsorption of P and Cr(Ⅵ) were 25.38 mg/g and 22.68 mg/g, respectively. The effect of pH and ionic strength were examined. Adsorption of P was decreased by competition of Cr(Ⅵ) and TA when the concentration of Cr(Ⅵ) and TA were 10 mg/L and 50 mg/L, but the effect was small. Adsorption of Cr(Ⅵ) was decreased significantly by the competition of P and TA when the concentration of P and TA were 10 mg/L and 50 mg/L. The amount of competition adsorption of P and Cr(Ⅵ) were 24.39 mg/g and 9.68 mg/g. Kinetic study of P, Cr(Ⅵ) and TA were performed. The competition between P and TA was much stronger than that between Cr(Ⅵ) and TA. The individual adsorption of Cr(Ⅵ) and P were well fitted to Langmuir model. The competition adsorption was well fitted to Freundlich isotherm for the P, and the Langmuir model was well fitted to the competition adsorption data for the Cr(Ⅵ). The TA could decrease the adsorption rate of the P and increase the adsorption amount of the Cr(Ⅵ).