Phosphate Adsorption Behaviors Of Polyacrylic Resin Containing Lanthanum Carbonate

As a non-renewable resource,phosphorus is an indispensable element in the activities of natural life and agricultural production;on the other hand,phosphorus plays a dominate role in eutrophication.Under the situations of shortage of phosphorus and serious eutrophication,the demand for further phosphorus removal and phosphorus recovery from sewage increased significantly.Lanthanum carbonate,which is a highly insoluble rare earth metal compound,has a strong ability to bind phosphate from water.In this study,a novel nanocomposite adsorbent NLC@213 was developed by immobilizing nanosized lanthanum carbonate（NLC）into the pores of macro-porous polyacrylic ion exchange resin D213 through an in-situ precipitation method for phosphate removal from wastewater.ICP-OES,BET,SEM-EDX,TEM,FT-IR,XPS,XRD and Zeta potential were employed to characterize NLC@D213.The results of batch adsorption experiments indicated that phosphate could be removed effectively by NLC@213 in a wide pH range.The Double-Langmuir isotherm model was suitable to fit the adsorption of phosphate,and the maximum adsorption capacity at 30℃reached to 53.64 mg/g.Moreover,the phosphate adsorption process of NLC@213 was spontaneous and endothermic.The pseudo-first-order kinetics model fitted the data well,and the phosphate adsorption of NLC@213 could reach equilibrium in 6 h when the initial concentration of phosphate was 10 mg P/L.The influences of co-existing inorganic anions on the phosphate adsorbtion of NLC@213 were in the following order:SO₄^2->NO₃^->Cl^->Si O₃^2->HCO₃^-.Compared with the supporting resin D213,a significantly improvement of NLC@213 was observed for resisting the interference of co-existing inorganic anions.Additionally,the influences of co-existing organic on the phosphate adsorbtion of NLC@213 were in the following order:gallic acid>tannic acid>humic acid.Compared with NLC@201 which possessed conventional polystyrene supporting,NLC@213was more efficient for resisting the interference of co-existing organic.The real bio-effluent from sewage treatment plant was employed to conduct the fixed bed adsorption-desorption experiment,and the results indicated that NLC@213 could reduce the concentration of phosphate to 0.5 mg P/L for meeting the primary A standard of total P（GB18918-2002）.The treatment volume of NLC@213could reach 2400 BV.The used NLC@213 could be regenerated effectively by a binary solution of Na Cl-Na₂CO₃,and no significant reduction in the efficient treatment volume was observed after three consecutive adsorption-desorption runs,indicating the satisfactory stability of NLC@213.Finally,the mechanism study revealed that NLC@213 adsorbed phosphate through electrostatic interaction and inner-sphere complexation,and the latter played the dominant role in the process of phosphate adsorption from real secondary effluent which containing co-existing inorganic anions and interfering organics.