Study On The Preparation And Performance Of Halloysite Arsenic Adsorption Materials

With the rapid economic development,human activities have brought many negative impacts on the environment.Natural weathering of rocks,volcanic eruptions,and human activities lead to the enrichment of arsenic in soil and groundwater,and ultimately enter the human body in the form of biological chains to affect human health.In recent years,there have been reports of acute and chronic arsenic poisoning in many countries and regions around the world.Therefore,arsenic contamination in drinking water has attracted worldwide attention.How to remove the arsenic ions in the water efficiently,conveniently and environmentally has become a pressing problem at present.In this paper,HNTs was first modified by y-aminopropyltriethoxysilane,which is environmentally friendly,low cost,unique structure and excellent adsorption performance.Then,the branched polyethylene imines were grafted onto HNTs nanotubes with glutaraldehyde as coupling agent.Quaternization was performed to prepare quaternary ammonium salted polyethyleneimine grafted halloysite(QAPEI-HNTs)nanocomposites for removal of arsenic from water.In this chapter,the composites were characterized by FTIR,TEM,TGA,BET and Zeta determination.The FTIR spectrum and TEM morphologies demonstrated that the QAPEI-HNTs was successfully prepared.Zeta potential measurements showed that a large number of positive charges on the surface of the composites when pH is less than 8.BET test showed that the materials had a higher specific surface area.Batch adsorption experiments were carried out to explore the best adsorption conditions of arsenic and to evaluate the kinetics of arsenic adsorption by QAPEI-HNTs.The results showed that the arsenic removal efficiency of QAPEI-HNTs is almost unaffected by temperature,and when the pH is 6-7,the adsorbent dosage is 2 mg/mL,the initial concentration is 4 mg/L,contact only 30 min,the treatment of arsenic wastewater can achieve an ideal removal efficiency and also showed excellent recycling performance.The adsorption kinetics study showed that the adsorption process of As(?)and As(?)by QAPEI-HNTs was more consistent with the pseudo-second-order kinetic model,indicating that the adsorption of arsenic occurred through chemical adsorption.From the above study,it was found that the material has excellent removal effect on As(V)and the removal advantage of As(?)is not obvious.In order to improve the removal ability of As(?),the rapid reduction coprecipitation method was used to prepare Fe3O4 with strong affinity for As(?)grown on HNTs.A highly efficient adsorbent Fe3O4/HNTs capable of rapid solid-liquid separation without causing secondary pollution was prepared.Using the unique spatial structure of HNTs,the size of Fe3O4 can be effectively controlled to avoid agglomeration.The FTIR and XRD patterns indicated that the composites were successfully prepared.Morphology of the Fe3O4/HNTs with different preparation methods were characterized by SEM and TEM.It was found that special acicular Fe3O4 can be generated on the surface of HNTs under the mass ratio of 3:1(iron salt:halloysite),and the materials were distributed evenly without any reunion.Batch adsorption experiments explored the optimal arsenic removal parameters by Fe3O4/HNTs.Studies have shown that the arsenic removal efficiency of Fe3O4/HNTs was not affected by temperature,and when the pH is 6-7,the adsorbent dosage is 2 mg/mL,and the initial concentration is 4 mg/L,the arsenic removal efficiency can achieve 98%of As(III)and 99%of As(V)respectively in 60 minutes.Meanwhile,the recycling performance is good and has obvious advantages for the removal of As(?).The adsorption kinetics study showed that the adsorption of As(III)and As(?)by Fe3O4/HNTs was more consistent with the pseudo-second-order kinetics model,indicating that the adsorption of arsenic ions by Fe3O4/HNTs occurred through chemical adsorption.The isothermal adsorption studies showed that the adsorption behaviors of As(III)and As(V)by Fe3O4/HNTs followed the Sips model,with the maximum adsorption capacities of 126.74 mg As(?)/g and 121.29 mg As(V)/g,respectively.These results show that Fe3O4/HNTs has great application prospect in the removal of arsenic wastewater.From the above study,the removal effect of As(?)on the material has been significantly improved,but due to the small size of the material and the strict preparation conditions,it is not conducive to large-scale application.In order to obtain arsenic sorbents with high adsorption performance and practical application value,natural halloysite nanotubes(HNTs)was used as matrix materials,a low-cost and three-dimensional porous polyurethane foams was used as a carbon source to generate HNTs/C composite materials after high temperature carbonization.Then,a co-precipitation method was used to prepare a high-efficient adsorbent with three-dimensional structre,high specific surface area and easy to separate.Characterization of the composites by FTIR,TEM,Raman,TGA,BET,VSM and other testing methods proves that HNTs/C/Fe3O4 magnetic nanocomposites has been successfully prepared.The composites has a rough surface,a large specific surface area,a strong magnetic response,a three-dimensional porous structure,a small pore size,uniform material distribution,and no agglomeration.The batch adsorption experiments explored the optimal arsenic removal parameters by HNTs/C/Fe3O4.Studies have shown that the arsenic removal efficiency of HNTs/C/Fe3O4 is not substantially affected by temperature and can remove arsenic from the solution rapidly(60 min)using a lesser(0.5 mg/mL)adsorbent under neutral conditions(pH 6-7).The material not only has a high removal efficiency,but also has good recyclability.The HNTs/C/Fe3O4 has high removal efficiency for As(III)and As(V)of more than 99%,it has obvious advantages compared to other reported arsenic adsorption materials.Adsorption kinetics studies showed that the adsorption of As(III)and As(V)by HNTs/C/Fe3O4 was more consistent with the pseudo-second-order kinetics model,indicating that adsorption of arsenic ions by the material occurred through chemical adsorption.Isothermal adsorption studies indicated that the adsorption of As(III)and As(V)by HNTs/C/Fe3O4 followed the Sips model.The maximum adsorption capacities were 34.54 mgAs(III)/g and 1491.72 mgAs(V)/g,respectively.Thermodynamic studies showed that the adsorption process was a spontaneous process.These results show that HNTs/C/Fe3O4 has great application prospects in the removal of arsenic wastewater,and have great regeneration performance with no secondary pollution.