Adsorption of pb²⁺ in water by zr-containing silica residue and its mechanism

Zr-containing silica residue (Zr-s-r) is waste residue discharged during the industrial production of ZrOCl2. Its purified product (Zr-s-r-P) can be used as an adsorbent whose main component is amorphous SiO2. Herein, Pb(NO3)(2) solution was used as wastewater containing Pb2+. The adsorption of Pb(2+ )in water by Zr-s-r-P and its mechanism were studied. The results showed that the adsorption effect was affected by the initial concentration of Pb2+ in the solution, pH, and adsorption time. The adsorption capacity of Zr-s-r-P to Pb2+ was 45.3 mg/g under the optimized conditions (25 degrees C, pH=6, Zr-s-r-P dosage of 2 g/L, and adsorption time of 25 min). The process of adsorption fits the pseudo-second-order model, and the isothermal adsorption fits the Langmuir adsorption model. Pb2+ was adsorbed in the pores of Zr-s-r-P. Moreover, the adsorption of Pb2+ by ZSR-P was achieved through the reaction between Si-OH on the surface of SiO2 and Pb2+ hydroxyl compounds.