Phosphate adsorption performance of zirconium-calcium synergistically loaded hydrogel
Phosphate(P)is an essential nutrient for living organisms and a key ingredient in crop fertilizers and industrial products.The problem of phosphate pollution brought by industrial and agricultural development has become increasingly serious,and excessive phosphate in the aquatic environment can lead to severe eutrophication.Therefore,it is imperative to remove phosphate from phosphate-containing wastewater before discharging.Adsorption is an effective method for removing phosphate from wastewater with the advantages of high efficiency,easy operation and flexible design.Among them,a representative material is hydrogel,which is widely used for the phosphate adsorption because of its advantages of low cost,environmental friendliness,and high adsorption capacity.Sodium alginate(SA)is non-toxic and biocompatible,and it can quickly form hydrogels by complexing divalent or multivalent metal cations through ion exchange reactions,so it has been widely used for embedding and adsorption of pollutants.In this research,a hydrogel was prepared using sodium alginate as a substrate to complex Zr4+,which is highly selective for phosphate,through an ion exchange reaction.At the same time,Ca2+was added to reduce the contamination of Zr4+in the hydrogel,so as to prepare a zirconium-calcium@sodium alginate(ZrCa@SA)hydrogel with high efficiency in adsorption of phosphates.The ZrCa@SA hydrogels were specifically characterized by the scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),Fourier infrared spectroscopy(FT-IR)and X-ray spectroscopy(XPS)for examining the micromorphological structure and chemical properties.The influences of the initial phosphate mass concentration,zirconium-calcium mass ratio,and temperature on the adsorption performance of the phosphate of the hydrogel were explored.After determining the optimal process conditions,the adsorption process of phosphate on hydrogel was investigated by fitting an adsorption kinetic model.The results showed that,when the zirconium-calcium mass ratio was 1∶4,the initial phosphate mass concentration was 50 mg/L,and the temperature was 45℃,the adsorption capacity reached 124.04 mg/g,and the residual phosphate mass concentration was 0.12 mg/L,which meets the phosphate discharge requirement of industrial wastewater(≤0.5 mg/L).The phosphate adsorption process of the ZrCa@SA hydrogel conformed to the pseudo-second-order kinetic and intraparticle diffusion model.The results showed that the ligand exchange between—OH which was generated by Zr4+hydrolysis and phosphate(chemisorption)dominated the phosphate adsorption process,and the adsorption process was mainly controlled by the intraparticle diffusion step of phosphate in the ZrCa@SA hydrogel.This research provides some theoretical support for the treatment of phosphate pollution in aquatic environment.
hydrogelphosphatezirconium-calcium mass ratioadsorption performanceadsorption kinetics
万方数据
维普
