Preparation Of Sodium Alginate/Metal Salt Hydrogel And Its Sorption Behavior To Phosphate

Phosphorus is an indispensable resource in life.A large amount of phosphorus ore was mined every year and used in various fields.However,during the application of phosphorus,part of phosphorus-containing wastewater was discharged into the water bodies without treatment or with imperfect treatment,resulting in the deterioration and algal bloom of the receiving water bodies.Thus,it is of great significance to effectively remove phosphorus from phosphorus-containing wastewater,so as to improve the water quality in our production and life.The adsorption methods have gained great attention because of its easy operation,simple design and cost effectiveness with high recovery rate for low concentration phosphorus solution.Therefore,adsorption was applied to remove phosphorus element in phosphorus-containing wastewater and improve the quality of phosphorus-containing wastewater in this study.The traditional hydrogel materials were synthesized by multi-step method which was relatively complicated.In this work,sodium alginate/zirconium（SA/Zr）hydrogel was synthesized by a simple method,with the phosphate adsorption performance and mechanism being explored.As a result,the adsorption capacity of SA/Zr hydrogel to phosphate was greatly affected by p H.The maximum adsorption capacity of SA/Zr hydrogel to phosphate could reach 246.23 mg/g at p H 3 and the initial phosphate concentration at 200 mg/L.As the initial p H increased,the maximum adsorption capacity showed a gradual decrease,but at p H 7,the maximum adsorption capacity could still reach 121.85 mg/g.The material showed high ion selectivity to phosphate,and the coexisting ions such as HCO₃^-,SO₄^2-,and NO₃^-had little effect on phosphate adsorption.The process of phosphate adsorption was well fitted by Intraparticle Diffusion model,indicating that there was chemical adsorption during the adsorption process,and the adsorption rate of phosphate showed a trend of first fast and then slow.The isotherm data was well fitted by Redlich-Peterson isotherm model,and the phosphate adsorption was a mixed process of single-layer adsorption and multi-layer adsorption.Both X-ray Photoelectron Spectroscopy characterizations and Zeta-potential results indicated that the adsorption mechanisms were related to electrostatic action,and hydrogen bonding and ligand exchange.In order to further reduce the manufacturing cost of the adsorbents.The Ca²⁺was inducted into this system to prepare sodium alginate/zirconium@calcium（SA/Zr@Ca）hydrogel.The material was characterized by X-ray Diffraction,Scanning Electron Microscope and X-ray Photoelectron Spectroscopy,and its adsorption performance were studied.As a result,the maximum adsorption capacity of SA/Zr@Ca hydrogel to phosphate could reach 124.23 mg/g at p H 2 and the initial phosphate concentration at50 mg/L,and the adsorption capacity of SA/Zr@Ca to phosphate was more than 60mg/g in initial solution p H of 2-9.The coexistenting ion such as HCO₃^-,SO₄^2-and NO₃^-had little effects during the adsorption process.The phosphate adsorption process was well fitted by Intraparticle Diffusion model,and the isotherm data was well fitted by Redlich-Peterson isotherm model.It was found that theΔG^θof phosphate adsorption program<0 at various temperatures,indicating that the phosphate adsorption process to SA/Zr@Ca hydrogel was spontaneous.