Preparation Of Cerium Based Composite Adsorption Materials Based On In-situ Synthesis For Phosphate Removal

In recent years,the excessive use of phosphorus worldwide has accelerated the eutrophication of aquatic ecosystem.Therefore,effective measures should be taken to control the content of phosphate in water bodies.At present,the main methods for phosphorus removal from wastewater include biological method,chemical precipitation method,membrane separation method,and material adsorption method.Among these methods,adsorption method has received widespread attention due to its simple operation,high efficiency,and recyclability.However,developing an efficient,low-cost adsorbent with high adsorption selectivity for phosphate remains a serious challenge.Research has found that cerium based metal organic framework materials（Ce-MOFs）have excellent properties such as high surface area and large pore volume.Considering these characteristics,designing metal organic frameworks and their derivatives for nanostructures has attracted the attention of researchers.But these powder particles are prone to secondary pollution when used in water treatment.Based on this,this topic introduced Ce-MOFs material to biochar and chitosan through simple in-situ synthesis,and prepared the corresponding green,efficient,low-cost and sustainable cerium based metal organic framework composite adsorbent.The structure,removal effect and phosphorus removal mechanism of the two modified composite adsorbents were studied,and the dynamic adsorption effect of chitosan/MOFs gel spheres was analyzed.The main conclusions are as follows:（1）By introducing cerium based metal organic frameworks into biochar through in-situ synthesis,carbon based/cerium based composite adsorption materials（CB-CD,PB-CD,CB-CT,and PB-CT）that can effectively remove phosphate were successfully prepared.Detect the carbon based/cerium based adsorbent before and after phosphate removal using SEM,BET,FT-IR,XRD,and XPS.Research has shown that the maximum phosphate adsorption capacities of CB-CD,PB-CD,CB-CT,and PB-CT are 151.90 mg/g,166.25 mg/g,215.85 mg/g,and 193.42mg/g,respectively;The kinetic experiment found that compared with CB-CT and PB-CT,the adsorption reaction rate of phosphate by CB-CD and PB-CD was extremely fast;The initial p H effect experiment shows that the adsorption capacity of CB-CD and PB-CD for phosphorus can reach a high level of more than 130 mg/g in the range of p H=2～12,while CB-CT and PB-CT only have better adsorption performance at p H=3～6,which may be due to the fact that the coordination bond of cerium on CB-CT and PB-CT is basically occupied by formic acid,so there are few active site,so the surface precipitation and ion exchange effect cannot be effectively exerted under alkaline conditions;Experimental studies on coexisting ions have shown that the ability of the above adsorption materials to adsorb phosphate decreases in the presence of F^-,and CO₃^2-also has an inhibitory effect on CB-CT and PB-CT;The regeneration experiment shows that the regeneration rate of these adsorbents decreases with the increase of cycle times,indicating that the four carbon based/cerium based composite materials have good phosphate removal potential in practice.（2）Different from the cerium based MOFs loaded after embedding method previously used,in this paper,Ce-MOFs were grown in situ into chitosan microspheres through a simple and low-cost in-situ synthesis method,and a highly efficient and easy to separate chitosan gel sphere composite（CS/CD-1 and CS/CD-2）was successfully prepared;SEM,BET,FT-IR and XPS were used to analyze the composite adsorbent of chitosan gel ball before and after phosphate removal;The isothermal experimental study shows that the maximum adsorption capacities of CS/CD-1 and CS/CD-2 are 124.13 mg/g and 132.07 mg/g,respectively;The initial p H effect experiment shows that the CS/CD-1 composite adsorbent cannot perform its excellent adsorption performance under alkaline conditions,while CS/CD-2 has excellent phosphorus removal performance in a wide range of p H=2-11.The results of adsorption column penetration experiment showed that when the concentration of phosphate in influent water increased,the penetration time of CS/CD-1 and CS/CD-2 adsorption columns significantly decreased,the effective treatment time decreased from 452 h and 490 h to 304 h and 346 h,and the treatment volume decreased from 81360 m L and 88200 m L to 54720 m L and 62280 m L,respectively.When the phosphate solution in influent water was added with coexisting ions,the effective treatment time of CS/CD-1 and CS/CD-2 gel ball materials was 120 h and 144 h,respectively,It indicates that both can be effectively applied in practical phosphorus removal for a long time.