Study On The Enhanced Removal Of Ammonium And Phosphate From Aqueous Solution By Granular Aluminum-manganese Bimetal Oxide & Zeolite Composite Adsorbent

Eutrophication of surface water has been a major environmental problem that puzzles the construction of urban ecological civilization.However,few studies have been carried out on the simultaneous removal technology of ammonium and phosphorus from micro-polluted water.This study is intended to develop a novel and efficient granular adsorbent?GAMZA,Granular Aluminum-Manganese bimetal oxide&Zeolite Composite Adsorbent?.Rod particle adsorbent was prepared by mechanical extrusion method by using the modified zeolite that is on intimate terms with ammonium and the Al-Mn binary oxide with a hydroxyl-rich surface.GAMZA was characterized by the methods of SEM-EDS,FT-IR,XRD,XPS and BET.The adsorption properties of ammonium/phosphate were investigated by adsorption kinetics,adsorption isotherm and pH influence experiments.In addition,the regeneration property and recycling performance of GAMZA were evaluated through adsorption-desorption experiments.The main results are listed as follows:?1?The optimal modified method for natural zeolite on absorbing ammonium was 0.8mol/L NaCl.The optimum ratio was 2:3,which was determined by comparing the removal efficiency of ammonium/phosphate with different proportions of Al-Mn binary oxide and zeolite powder.Cylindrical GAMZA particles with size of d1.5mm*2.5mm and 0.6g/cm³ were prepared by extrusion method with polyvinyl alcohol?PVA?as binder.?2?The surface properties and structure features of GAMZA were studied by a number of characterization techniques.The results showed that Al-Mn binary oxide is coated or embedded in the crystalline phase of the zeolite to form large particles.FT-IR showed that the granulation process could effectively gathered the functional groups but not break material.The maximum mechanical load and average compressive strength of GAMZA were 32.45N and 7.3MPa,respectively.The specific surface area was14.4m²/g,isoelectric point was 8.53,the main elements were C,H,O,Al,Mn,Si,S,Na.?3?The kinetics data of ammonium or phosphate adsorption on GAMZA were in accordance with the pseudo-second-order model,which indicated that mechanism was the chemical adsorption.Meanwhile,the adsorption process was controlled by more than one rate-limiting step not only particle diffusion.With the aid of characterization results,ion-exchange was the main mechanism of ammonium removal,while phosphate adsorption depended on surface complexation.The thermodynamic tests indicated that the adsorption of ammonium/phosphate to GAMZA was the spontaneous and endothermic nature reaction.The effect of pH on ammonium is not significant,but opposite for phosphate,it was found that the phosphate removal efficiency decreased with an increase of pH?4-10?.The coexisting cation Ca²⁺and Mg²⁺had the inhibitory effect on the adsorption of ammonium,and the coexisting anion F^-and CO₃^2-had a great influence on phosphate removal.Compared with the single pollution system,the saturated adsorption capacity decreased from 12.9mg-N/g and 9.3mg-P/g to 7.1mg-N/g and 6.4mg-P/g under the condition of compound pollution.In addition,the interaction between the two pollutants was not obvious in low initial concentrations,while at high concentrations?C₀>50mg/L?that emerged mutual inhibition.?4?GAMZA had a good value of regeneration,because after five consecutive cycles there still had a high adsorption capacity by using 0.4M NaHCO₃ as the elusion solution.In addition,the dynamic experiment's results indicated that the GAMZA had obvious effect to improve the quality of the water.It is expected to be applied to the effective prevention and treatment of pollution of water eutrophication.