Preparation Of Modified Attapulgite And Its Removal And Application Of Methylene Blue And Chromium(Ⅵ)

In recent years,with the rapid development of industry,water pollution has become more and more serious.Among them,dye pollution and heavy metal pollution are particularly prominent,they have a great harm to river water,aquatic life and human health.Therefore,the exploration of economical and effective pollution treatment process of dyes and heavy metals is an urgent problem to be solved.As a natural nanomaterial,attapulgite(ATP)has a large specific surface area and exhibits an excellent adsorption performance,which is widely used in water pollution treatment.However,most of the current studies are focused on the treatment of specific adsorbates,and there are few researchs on the removal of dyes and heavy metals.In order to enhance the comprehensive adsorption capacity of attapulgite,In this paper,the removal of dyes and heavy metals by modified attapulgite is studied by loading β-cyclodextrin(β-CD)with representative cationic dyes methylene blue and heavy metal chromium(Ⅵ)as adsorption targets.The effects of different mass ratios(ATP:KH560:β-CD),adsorption time,pH,initial concentration of solution,dosage and ambient temperature on the adsorption effect are invesigated,and the adsorption mechanism is simply conjectured.In order to make up for the disadvantage that the adsorbent is difficult to achieve a rapid separation,magnetic attapulgite is prepared through hydro-thermal method.The effect of magnetized attapulgite on the removal of methylene blue solution was studied and the influence of Fe3O4 content and adsorption time on the adsorption effect was investigated.A series of modified attapulgite clays are prepared by loading β-cyclodextrin onto attapulgite for 12.0 h at 110℃ with silane coupling agent KH560 as the linker and its structure is characterized by a series of methods.IR results shows that the C-H characteristic peak of p-cyclodextrin appeare on modified attapulgite;in addition the modified attapulgite has a reduced surface area due to agglomeration.Static adsorption experiments shows that:the modified attapulgite clay prepared with the mass ratio of 6:1:3 has a good adsorption effect for 100.0 mg·L-1 methylene blue and 1.0 mg·L-1 chromium solution,the acid-modified modified attapulgite is superior to the directly modified attapulgite and the original soil(ATP<ATP/CD<HATP/CD).Under the conditions of room temperature and pH>9.0,10 mg of attapulgite was used to treat 20 mL of methylene blue solution with a concentration of 100.0 mg·L-1,the equilibrium adsorption rates of the three materials were all above 90%;in addition,under the conditions of room temperature and pH=2,10 mL of chromium solution with a concentration of 1.0 mg·L-1 was treated with 10 mg of attapulgite,after 8.0 h of adsorption,the removal rates was basically balanced.The kinetics study found that using a second-order kinetic model that describes a complex adsorption process was closer to the actual HATP/CD fitting result,indicating that the modified attapulgite clay adsorbed methylene blue and hexavalent chromium was a multi-activity site interactions.In the isotherm fitting,the adsorption process of HATP/CD using the Langmuir model is more consistent with the actual adsorption conditions,and the correlation coefficient R2 was above 0.97.The magnetic attapulgite clay(HATP/CD/Fe3O4)was prepared by hydrothermal method.The IR spectra showed that the magnetization process did not change the main structure and still retained the characteristic peaks of the attapulgite and β-cyclodextrin;The measurement results of specific surface area showed that the specific surface area gradually increased with the increase of the trivalent iron content,but decreased when the content exceeded 10 mM.Static Adsorption Tests found that 4 mM trivalent iron magnetization had a better adsorption effect;The pH value of the solution had a great influence on the removal of methylene blue.When pH<6.0,the adsorption rate increased slowly;when the pH changes from 6.0 to 7.0 over the isoelectric point of Fe3O4,the adsorption rate increased suddenly;after that,the overall adsorption rate did not change significantly with increasing pH.Compared with the magnetite attapulgite without reuse,the magnetized attapulgite clay still had a better adsorption removal effect after used repeatedly and the removal rate decreased only 3.2%.Repeated two or three times,the magnetized attapulgite still had a good adsorption effect.The magnetized attapulgite adsorption process was more consistent with the second-order kinetic equation and the Langmuir isotherm,the correlation coefficient R2 was all above 0.995.