Preparation Of Lanthanum Compound Modified Adsorbents And Studies Of Their Phosphate Removal Performances

Phosphate is a basic nutrient which is vital for the growth of aquatic organisms.But excessive emission of phosphate to the runoff system is confirmed to lead to eutrophication,which causes aquatic ecosystem collapse.Therefore,it is very urgent to remove phosphate from wastewater,which is a hot research in the field of environmental protection.At present,there are many techniques for the removal of phosphate.Particularly adsorption is regarded as a promising technology to remove phosphate,due to the advantages of high selectivity and easy operation.However,most of the adsorbents have various shortcomings,such as high cost,low adsorption rate,low adsorption capacity.Therefore,we devoted to develop a low-cost,highly efficient and possessing potential application adsorbent for phosphate removal.The thesis is based on the following three areas:1.La（OH）₃-modified magnetic pineapple biochar were prepared and used as phosphate adsorbents,which exhibited excellent magnetic property for easy recovery and high adsorption capacity up to 101.16 mg P/g.Adsorption isotherm and adsorption kinetics were better fitted by Langmuir model and pseudo second-order model,respectively.The removal efficiency greater than 96.04%in coexisting ions indicated its high selectivity to phosphate.Little decrease in removal efficiency after three adsorption-desorption cycles suggested its excellent stability and cyclic utilization.Leaching study demonstrated the negligible risk of La³⁺and Fe³⁺leakage during adsorption process.Mechanism study revealed that the adsorption mechanism involved precipitation,electrostatic interaction,ligand exchange and inner-sphere complexation.2.La（OH）₃-loaded magnetic carboxymethyl cellulose adsorbent was prepared,and a series of studies on its phosphate removal performance were studied.The results show that the adsorption capacity of the adsorbent was up to 62.98 mg P/g and possess good magnetic recovery performance.The initial phosphate concentration,adsorption time,pH value of the solution,and the effect of coexisting ions on the adsorption performance were systematically investigated.In addition,the adsorption mechanism was discussed,which contained precipitation,ligand exchange and inner-sphere complexation mechanism in the process of adsorbing phosphate.This work obtain a novel adsorbent with simple process,excellent adsorption performance and good magnetic properties.3.Lanthanum-magnesium bimetallic composite modified lotus leaf biochar adsorbent was prepared and its phosphate removal performance were studied.The results show that the maximum adsorption capacity was up to 100.02 mg P/g.The adsorption data were better fitted by the Langmuir isotherm model and pseudo second-order model,revealing that the adsorption process was monolayer adsorption and chemisorption.In addition,the adsorption capacity maintains a high level within the pH between 3.0 and 6.0.Leaching study demonstrated the negligible risk of La³⁺and Mg²⁺during adsorption process,which suggested its excellent stability.Desorption experiments showed that the adsorbent could be regenerated.The adsorption mechanism was revealed.