Study On The Recovery Of Phosphorus From Sludge Dewatering Filtrate By Magnetic Anion Exchange Resin

Phosphorus(P)is a non-renewable and unidirectional limited resource.Besides,eutrophication caused by phosphorus and other nutrient elements is more and more serious.Recovery of phosphorus from sewage are essential for controlling water eutrophication and sustainable using P resource.Aiming to phosphorus in the sludge dewatering filtrate from wastewater treatment plants,we studied the adsorption characteristics and removal mechanism of P adsorption on MAEX resin and discussed the regeneration property of M A EX resin.The results observed that the adsorption capacity of MAEX could reach maximum 2.74 mg/mL,when initial P concentration was 25 mg/L,dose of MAEX was 8 mL/L and initial pH was 8.The P adsorption on MAEX resin was suit for large temperature range(283K?323K),which indicated MAEX resin can be better to cope with the environmental temperature fluctuation.However,the adsorption capacity of MAEX was reduced in different degree with the existing of various anions and organic compounds.The order of the inhibition of anion was as follows:Br>SO42->Cl->NO3->HCO3->CO32-.And the inhibition of humic acid was stronger than that of bovine serum albumin.The kinetic process and thermodynamic characteristics of P adsorption by MAEX resin were fitted and analyzed respectively.The kinetics studies displayed that the P adsorption process followed the pseudo-second-order model with different P concentration,resin dosage or initial pH,which illustrating that chemisorption was the main factor controlling the P adsorption on MAEX resin.The fractal research result shows that the adsorption of P by MAEX resin is nonlinear adsorption.Furthermore,the adsorption reaction was mainly but not only controlled by intra-particle diffusion,while the adsorption rate was also affected by particle diffusion,such as liquid film diffusion.Thermodynamic experiments showed the adsorption isotherm data fitted to Langmuir model more than Freundlich model.According to the analysis of thermodynamic parameters,it was found that the adsorption process of P on MAEX resin was spontaneous and endothermic.Moreover,to the absolute value of AG at five temperatures ranged from 14?17 KJ/mol,we could infer that the adsorption is not only chemical adsorption,but also physical adsorption.The change of functional groups,characteristics of microstructure,the change of thermal stability and magnetic MAEX resin before and after P adsorption were characterized by the method infrared analysis,surface morphology analysis,thermal analysis and magnetic analysis.From FTIR analysis,we could confirm that ion exchange,charge attraction,hydrogen bonding and so on affected the removal of P by the MAEX resin.Aeeording to VSM analysis,the MAEX resin was soft magnetic material with good magnetism.Regeneration characteristics of MAEX resin after P adsorption were analyzed.The result showed that 1.0 mol/L NaHCO3 had good regeneration effect on MAEX resin.The regeneration process was basically stable after 30 min of regeneration time.After 10 times of adsorption-desorption cycles,the P adsorption capacity was reduced with less loss(9.48%)which indicated that MAEX has an excellent regeneration ability and thus has a very good application prospect in P removal and recovery.