Removal Of Ammonia Nitrogen From Ion-adsorped Type Rare Earth Tailings Water By Halloysite-based Materials

Ion-adsorped type rare earths is the earliest discovered the unique rare earth resources in our country,the current conditions,the use of ammonium sulfate in-situ leaching mining is relatively common,ore leaching process inevitably bring many pollution problems,including ammonia nitrogen pollution is serious,the current has been closed of ionic type rare-earth ore still has a high concentration of ammonia nitrogen in wastewater,long-term effects to surrounding soil and water environment.The general method of treating ammonia nitrogen wastewater is complicated and expensive.The adsorption method is favored by many people because of its rich raw materials and simple operation.In this paper,halloysite nanotubes(HNTs)were selected as the carrier material for the adsorption of ammonia nitrogen.It is abundant in nature and has a special hollow tubular structure,and its use and recovery process will not harm the environment and organisms.This paper mainly studies the adsorption of ammonia nitrogen in ionic rare earth tailings wastewater by eluo stone based materials through experiments from three parts,and draws the following conclusions:(1)The optimal dosage of HNTS for ammonia nitrogen adsorption in simulated ammonia nitrogen wastewater was 7.5 mg/L;The optimum pH value is around 7.31.The adsorption of ammonia nitrogen by HNTs satisfied the quasi-second-order kinetics and Langmuir adsorption isotherm model.(2)Modified natural halloite was prepared by thermal,thermal-acid,thermal-alkali,thermalalkali-acid,thermal-acid-base modified halloite,respectively,and the adsorption experiment was carried out.The results showed that the best modification method for the adsorption of ammonia nitrogen was "heat-acid-base" method,and the optimal material was called H-H-OH-HNTs,whose adsorption capacity was more than 7 times that of natural halloite nanotubes.The optimal conditions for composite modification are as follows: concentration of 8 mol/L sodium hydroxide,calcination temperature of 800℃,alkali impregnation temperature and time of 50℃,30 min and3.5 mol/L sulfuric acid,respectively.H-H-OH-HNTs adsorption process of ammonia nitrogen was well fitted by quasi-second-order kinetic model,and the Langmuir adsorption isotherm model was well fitted by isotherm adsorption experiments.Combined with the characterization results,it is concluded that the main reason for the performance improvement of H-H-OH-HNTs is sodium ion exchange.(3)When the concentration of ammonia nitrogen is 100mg/L,the removal rate of composite modified haloite is 91.3%,and when the concentration of rare earth ions is 8 mg/L,the removal rate can still reach more than 70%.The influence of light rare earth elements on the material is greater than that of rare earth elements.With the increase of sulfate concentration,the removal rate of ammonia nitrogen decreased.When the sulfate concentration was 2000 mg/L,the removal rate of ammonia nitrogen could still reach more than 70%.In general,the influence of high concentration of rare earth ions and high concentration of sulfate on the material is within the acceptable range.When the concentration of ammonia nitrogen in the actual wastewater is185.3mg/L,the H-H-H-HNTs removal rate is 78.15%,and the adsorption capacity can reach 10.42mg/g.In order to achieve the purpose of recycling,magnetic particles are introduced.The magnetic materials obtained by hydrothermal synthesis are easy to be separated from wastewater and friendly to water environment,which also provides conditions for recycling.