Study Of The Modification And Performance On The Phosphate Removal Of Porous Ceramisite Adsorbent

Phosphorus is considered as the major limiting factor in the eutrophication of water bodies.In this study,porous ceramsite?PC?made with clay and sludge was selected as the phosphate adsorbent,and the modification conditions of ceramsite were optimized by using different modification methods.Two kinds of modified ceramsite of HCl-modified porous ceramsite?PCH?and lanthanum-modified porous ceramsite?PCL?with higher phosphate removal efficiency were obtained.The physicochemical properties of PCH and PCL were studied by a variety of characterization methods.The modification mechanism and the main phosphoate removal mechanism were further analyzed.Besides,the effects of solid-liquid ratio,initial phosphoate concentration,pH,coexisting ions on the adsorption effect were further studied.In addition,the regenerative properties of the modified ceramsite and the performance of the dynamic phosphate removal were also tested.In the study of the modification conditions,it was found that pure heat treatment had little improvement on the phosphate removal efficiency of the ceramsite.The hydrochloric acid modified ceramiste prepared at a hydrochloric acid concentration of 2 mol/L,an activation temperature of 60°C and a modification time of 6 h had better adsorption performance.When the doping mass ratio was 0.1,the lanthanum-modified ceramsite obtained under the calcination temperature of 400°C had a relatively stable structure and satisfactory phosphate removal efficiency.In the pH range of 4-10,PCL can effectively remove phosphate,the adsorption process was in line with the Langmuir adsorption isotherm model and the reaction kinetics followed pesudo-second-order kinetic model.Under the neutral conditions,PCL was also enable to remove the pyrophosphate effectively.The process of phosphate adsorption by PCH corresponded to the Frendlich adsorption isotherm model and the reaction kinetics was also followed pesudo-second-order kinetic model.Thermodynamic studies indicated that the adsorption of phosphate by PCH and PCL were endothermic process.The coexisting ions of Cl^-,NO₃^-,SO₄^2-had little effect on the phosphate removal by PCH and PCL,while HCO₃^-had a significant effect on that.In the fixed-bed adsorption study,a lower flow rate could increase the breakthrough volume of the dynamic adsorption and improve the utilization efficiency of the adsorbent.It was found that the PCL could be effectively regenerated by using of 1 mol/L NaOH,while PCH was difficult to be desorbed.The possible mechanism of phosphate removal by PCH and PCL were mainly included electrostatic attraction,ligand exchange,surface precipitation and so on.Compared with traditional adsorbents for phosphate removal,the modified ceramsite were easy to be seperated and in accord with the innovative concept of treating waste by waste.Besides,there were suitable for fixed-bed column adsorption and have great value for practical application.