Preparation And Properties Of Nanoscale Zero Valent Iron Supported On Modified Attapulgite

During twenty-first century,nano technology develop rapidly, which become a hot research in the field of science and get much attention by governments and technical workers. In recent years, as a new kind of nano materials,nanoscale zero valent iron has become a hot research topic in inorganic materials. The size of nanoscale zero valent iron is during 1-100nm,which has the characteristics of large specific surface area, strong reduction,etc.In the early days,nanoscale zero valent iron used for in-situ remediation of groundwater and at present it has been used in removal of chlorinated organic compounds, treatment of organic dyes or pesticides, removal of heavy metals and radioactive material. Although nanoscale zero valent iron has a lot of applications, it is prone to aggregation and easy oxidation in practical application. Therefore, solve the problem of prone to aggregation and improve stability has become a hot research for the use of nanoscale zero valent iron.The subject selected attapulgite which has the properties of rich, low cost, good settling, adsorption, modified and load performance. Acid treatment and microwave modification were used to modify attapulgite at first. And then with the modify attapulgite as supporter to prepare nanoscale zero-valent iron-support modified attapulgite.During the process of preparation, the attapulgite were characterized by orthogonal experiment to find the best preparation. The optimum conditions of modification were listed as follows:the iron and soil ratio 2.5:l,the concentration of acid 3mol/L, time of microwave 6min, microwave power 600W,the reaction time 24h.The nanoscale zero-valent iron-support modified attapulgite hit the nano scal and had good stability in usually hydraulic impact, mixing and pH of conventional water treatment.And then,analysised the nanoscale zero-valent iron-support modified attapulgite and find the different through scanning electron microscope(SEM),energy dispersive spectrometer(EDS),infrared spectroscopy(IR),X-ray diffraction(XRD) and surface area (BET). The results showed that acid treatment is advantageous to remove the surface impurities on attapulgite and provide a good environment for load. After modification, part of crystal water and adsorbed water in attapulgite was loss and the whole structure was loose and flake.In addition,studyed the adsorbent of Cr(Ⅵ) by nanoscale zero-valent iron-support modified attapulgite. At last,analysised the adsorption process of Cr(VI) on kinetics and thermodynamics mechanisms. The research results could be gain as follows:(1)The modified and loaded occurring on the surface of attapulgite and did not change the basic structure of the internal which could keep both special crystal structure and characteristic group of attapulgite. After modification and load, the specific surface area, average particle size and pore volume increased more than natural attapulgite which have increased 112.01%,17.72%,18.4%.(2)The nanoscale zero-valent iron-support modified attapulgite has good reduction which can remove Cr(Ⅵ).The maximum removal rate of Cr(Ⅵ) was 97.67% and the optimum reaction conditions was pH=2,reaction time 30min,dosage O.lg and Cr(Ⅵ) Concentration 5mg/L.(3)The ion, such as H+、SO42- and C2O42-, had positive effect on removing Cr(Ⅵ) by nanoscale zero-valent iron-support modified. The efficiencies of Cr(Ⅵ) removal for different iron were H+> C2O42> SO42-.The Cl- ion had negative effect on removing Cr(Ⅵ) by nanoscale zero-valent iron-support modified.(4)It was found that pseudo-2nd-order kinetic model could better describe the dynamic process of removing Cr(Ⅵ) by nanoscale zero-valent iron-support modified. And the dynamic process of adsorption could be described by the Langmuir isotherm equation. Moreover, it was the beneficial non reversible adsorption.