Preparation Of Lanthanum-loaded Zeolite Composites For Phosphonate Removal From Industrial Wastewater

In recent years,phosphonates have become the main component of stabilizer,chelator,scale and corrosion inhibitor and have been put into industrial production of electroplating,papermaking,textile,reverse osmosis filtration and other aspects.Because the biological and chemical phosphorus removal methods can not effectively remove phosphonate in the conventional wastewater treatment process,the removal of phosphonate is worthy of further study.Because of its simplicity,high efficiency and no secondary pollution,adsorption method has been widely studied in the field of phosphate adsorption removal,but the systematic research on phosphonate is few.In this study,three kinds of lanthanum-loaded zeolite were synthesized by co-precipitation method and hydrothermal method.The optimum preparation conditions of the three materials were studied,and the removal and regeneration effects of the three materials on 1-hydroxyethylidene-1,1-diphosphonic acid（HEDP）were investigated,and applied to the adsorption in actual water.The main research contents are as follows:（1）La³⁺-modified zeolite and La（OH）₃-modified zeolite were prepared by co-precipitation method,and La₂（CO₃）₃-modified zeolite was prepared by hydrothermal method for the preparation of HEDP adsorption.The three lanthanum-loaded zeolite materials were characterized by SEM,XRD,BET,and ICP,which proved the multi-pore structure inside the three lanthanum-loaded zeolites and the results of successful lanthanum loading.The loading amounts were 49.8,65.5,and 73.3 mg/g respectively.At the same time the experiment explored the best synthesis optimization conditions for three lanthanum-loaded zeolite materials.The best preparation conditions of the three materials were obtained by investigating the adsorption effect of the three materials under different preparation conditions.（2）The performance effects of three lanthanum-loaded zeolites on the adsorption of HEDP were compared,and the materials before and after the adsorption of Phosphonate were characterized by FTIR,EDS,XPS and other means.Adsorption experiments show that the adsorption effect of La³⁺-modified zeolite and La（OH）₃-modified zeolite are stable in the range of pH=4～8,while the adsorption effect of La₂（CO₃）₃-modified zeolite can maintain a high level in the range of pH=3～11.The coexistence of anion and cation showed a certain promotion effect on the three lanthanum-loaded zeolites.The Freundlich model can better fit the adsorption process of the three lanthanum-loaded zeolites to HEDP,which indicates that they are all dominated by heterogeneous multi-layer adsorption.The Pseudo-second-order kinetic can better fit the adsorption process of HEDP on the three lanthanum-loaded zeolites,the results show that the adsorption of phosphonate on the three lanthanum-loaded zeolites is mainly chemical adsorption.The adsorption mechanism of lanthanum-loaded zeolite to HEDP is mainly electrostatic attraction,inner complexation and hydrogen bonding.The results of desorption and recycling experiments show that the recycling rate of La₂（CO₃）₃-modified zeolite reaches 90%.The results show that La₂（CO₃）₃-modified zeolite has the best effect by simulating the dynamic adsorption process of reverse osmosis concentrate.