Lanthanum Modified Clay Minerals On Microcystis Aeruginosa And Its Extracellular Organic Matter Removal Study

Small scale water bodies are mainly located in vast rural areas,they are related closely with our daily life.The characteristics of small scale water bodies contain poor mobility,poor self-purification capacity,small scale and large number.These water bodies are vulnerable to human activities and agricultural pollution,which can cause environmental problems such as algal blooms.Algal blooms have a serious threat to ecological safety and human health.Therefore,the remediation of algae blooms in small scale water bodies has become a powerful grip for rural revitalization.Clay mineral materials for algal removal were considered to be one of the most potential methods for application.Such as Hydrotalcite（LDHs）has good adsorption performance for electronegative pollutants such as algae cells and algal organic matter in the water bodies.In addition,Montmorillonite（MMT）has good ductility,and it is cheap and easy to get.These clay minerals are widely studied.In the natural algal bloom water,there are not only algal cells,but also a lot of organic matter and coexisting ions.This has led to inefficient and less practical algae removal by a single clay mineral.Based on the structural similarity and complementarity between LDHs and MMT,a composite algae removal material with dual adsorption properties was synthesized by using the modulating properties of lanthanum.Microcystis aeruginosa was selected as the target of the study.Study explored the algae removal efficiency and mechanism of the composite algae removal materials,then investigated the application prospects of the composite algae removal materials in natural water bodies.The paper firstly prepared the composite algae removal materials in situ by co-precipitation method.The proportion of the materials was determined by comparison of algae removal rate,and its characterization was analyzed.The results showed that the LDHs/La-MMT_2:1with LDHs to MMT ratio of 2:1 possessed the optimal algae removal efficiency.As shown in the figure of XRD,FTIR,BET and SEM characterization results of LDHs/La-MMT_2:1,we had successfully prepared a material with uniform distribution of lanthanum,and three metal ions of Mg/Al/La had good synergy.In which the main structure of MMT and LDHs existed,the lamellae of MMT was peeled open,LDHs was generated in situ on the MMT.The agglomeration phenomenon of composite algae removal material was weakened,the specific surface area was increased,and the adsorption performance of the composite algaecide material was significantly improved.The composite algae removal material was applied to the removal of algae cell in algae bloom water,and the application conditions were optimized by using CCD response surface design.Then study explored the mechanism of its application in algae bloom water bodies.The results showed that the composite algae removal material had a good removal efficiency on algal cells.When p H was 8.0,dosage of material was 1.16 g/L,initial algal concentration was 5.0 mg/L,the algal removal efficiency could reach 96.09%.After the removal of algae,the electronegality of water decreased,the algae cells were uniformly and densely covered on the surface of the algae removal material.And the reaction trace heat was-19.7 J/g,which was a spontaneous exothermic reaction.The mechanisms of algae removal was surface adsorption,complexation precipitation,charge neutralization and ion exchange.The removal efficiency of algal organic matter was discussed by composite algal removal materials.Analyzed the removal mechanism of algal organic matter using adsorption kinetic model,adsorption isotherm model and the variation of trace heat of reaction.The results showed that the main removal fraction of the composite algaecide material was humic-like substance.The composite algaecide material had faster adsorption efficiency and higher adsorption capacity for fulvic acid（FA）and huminic acid（HA）,and the adsorption and removal rate could reach more than 90%at 5 min of reaction,and the maximum adsorption capacity was 105.43 mg/g for FA and 120.26 mg/g for HA.In the case of high organic matter,the adsorption of algae removal materials occurred in a more favorable direction,and the removal mechanism was dominated by chemical monomolecular layer adsorption.The static column experiment was designed to analyze the stability and durability of the application of composite algae removal materials.Explored the feasibility discussions of composite algae removal materials to cope with actual algae bloom water.The results show that the composite algae material still had a good algae removal effect on simulated natural algae bloom water,and there was no phenomenon of algae secondary upwelling and algae organic matter surge during the stacking period.The removal rates of protein-like and humus-like substances by the compound algal removal material were 34.67%and 60.7%respectively in the natural water body control group.Combined with the parallel factor analysis method which showed that the dosing material could delay the time node of rapid growth of humus-like material,while the immobilization effect on protein-like material was obvious.In summary,the study proposed an algae removal material that could remove algal cells as well as algal organic matter efficiently and rapidly at the same time,which could be applied to the in situ emergency treatment of algae bloom in small scale water.