| Algae blooms caused by eutrophication pollution has become a serious environmental problem.Cyanobacteria blooms reduce water clarity and produce microcystins which threats drinking water safety,fisheries and aquaculture.Nitrogen and phosphorus nutrition elements is the basic condition of blooms outbreak,the algal cell death after bloom outbreak,the concentration of organic matter become higher in water,therefore,in the process to remove algae,a new technology which can remove nitrogen and phosphorus from source,as well as avoid the secondary pollution in water after cell death is the trend of environmental protection in recent years.Hydrotalcite is a representative clay mineral material,which surface is positively charged,has a unique layer structure and performance,and possess “structure memory effect”,which can be recovery layered structure by adsorption anionic after calcination,has a good adsorption performance on anion.The magnetite is study widely by many scholars due to sources,low cost,easy to recycle.Therefore,based on the comprehensive utilization of resources and the control principle from source,the paper synthesis composite materials by magnetite and hydrotalcite,which full use of the high adsorption performance of hydrotalcite and easy to recycle performance of the magnetite,applied to treatment the pollutants what is negatively charged in the surface in blooms,such as nitrogen,phosphorus,humic acid and algal cells,as to achieve the goal of completely cure blooms.This paper main research content is as follows:1.Magnetite/hydrotalcite(Fe-HT)composite materials were synthesized by co-precipitation method and its calcination products was prepared by heating Fe-HT at different temperatures.SEM,XRD,FT-IR,and XPS were used to characterize and analyze the magnetite and hydrotalcite.The morphology and structural characteristics of composite materials before and after composite of them were studied.On this basis,the mechanism of the composite was study of the magnetite and hydrotalcite.The results show that interaction between hydrotalcite and magnetite,but it does not affect the structure of a single component,The XPS spectra show that the Fe-HT contains Mg,Al,O elements in the full spectrum of hydrotalcite,also contain Fe element in the whole spectrum of magnetite,which illustratesed the experiment synthesis Fe-HT successfully.2.The influence of nitrate adsorption was studied by different preparation methods,calcining temperature,metal factors such as mole ratio of hydrotalcite,and chose the best under the condition of hydrotalcite material for subsequent adsorption experiments;The adsorption mechanism of hydrotalcite was studied preliminarily by different concentrations of nitrate,phosphorus and humic acid on the absorption performance of hydrotalcite and thermodynamics and dynamics equation.Results show that hydrotalcite removed nitrate with good effect under the condition of concentration of 2~12 mg/L.Calcination of hydrotalcite affect prophase of phosphorus adsorption process,had no obvious effect on the final adsorption.hydrotalcite removed phosphorus with good effect under the condition of concentration of 1~6 mg/L.Calcination hydrotalcite is better than not calcination hydrotalcite to remove humic acid,hydrotalcite removed humic acid with good effect under the condition of concentration of 2.5~15 mg/L.The adsorption kinetics and adsorption isotherm showed that the Pseudo-second-order kinetic model and Langmuir isotherm model could be used to describe nitrate and phosphorus adsorption satisfactorily.The Pseudo-second-order kinetic model and Freundlich isotherm model could be used to describe humic acid adsorption satisfactorily.When the concentration of nitrate,phosphorus and humic acid was 6,12,15 mg/L respectively,the maximum theoretical monolayer Q0 were 10.183,10.649,24.272 mg/g.Meanwhile,we explored the recycling performance of hydrotalcite through the hydrotalcite repeat phosphorus adsorption experiments.Found that adsorption after many times of hydrotalcite calcined to expand its adsorption capacity in the process of hydrotalcite recycle.3.The adsorption performance of before and after composite were studied by hydrotalcite and composite materials for the adsorption efficiency of nitrate,phosphorus,humic acid.The results showed that the removal rate of nitrate,phosphorus,humic acid is slightly lower after hydrotalcite composite,but the impact is not big.We studied the influence of coexisting ions adsorption properties of the composites.At the same time,the adsorption mechanism of composite materials was studied preliminarily by the different concentrations of nitrate,phosphorus and humic acid on the adsorption performance of composite materials and thermodynamics and dynamics equation.The results showed that the composite material on humic acid,nitrate and phosphorus adsorption kinetics and adsorption isotherm analysis results are basically identical with hydrotalcite adsorption results,to explain the join of coexisting ions and composite adsorption kinetics and adsorption isotherm of the composites before and after not significantly affect the results.4.In bloom dominant species Microcystis aeruginosa as the research object,we studied the effect of the different concentration of algae,stirring time,the concentration of humic acid on Microcystis aeruginosa cell adsorption by composite material,and taked pictures in the process of Microcystis aeruginosa cell adsorption.We studied the removal effect of nitrate,phosphorus and humic acid by composite material in the process of M.Aeruginosa cell adsorption.Results show that the best mixing time was 3.0 h in the process of the composite material adsorption algae cells,composite material was suitable for low concentration algae removal,also suitable for high concentration algae removal,remove the algae is suitable for the condition of low concentration of humic acid environment,also fit under the environment of high concentration of humic acid.Composite material have good capture to algal cells.In the bloom water,the composites had good removal efficiency to algae cells,nitrate,phosphorus and humic acid.5.The Fe,Mg and Al dissolution quantity of composite materials were measuried in the aqueous solution,which provided the basis for the environmental friendly performance for the composites as a new type of anion adsorbent;We explored the recycling properties of composite materials by recycling composite materials used for adsorption experiment.Results show that the composite material can guarantee the environmentally friendly properties in the process of removel algae,and avoid to produce secondary pollution.With the increase of cycles number of composite materials,adsorption rate decreased slowly,but the removal rate of settlement of 120 min to remove algae in composite materials can achieve above 85%,shows that the performance of the recycled on material can still restore,composite material with good performance of the cycle. |
PDF Full Text Request