Preparation Of Attapulgite/Nano-iron Composite And Its Removal Application To Methylene Blue

Nano-iron has the characteristics of strong reducibility,tiny geometry,low preparation cost,etc.It is widely used to adsorb and degrade organic pollutants in waters.The nano-iron is easy to be oxidized and agglomerated,which limits its application.In order to solve this problem,we selected modified attapulgite?HCl/dodecyl dimethyl benzyl ammonium chloride?as the carrier of nano-iron,and prepared two attapulgite/nano-iron composite by liquid phase reduction method,and used composite to remove methylene blue in waters.The preparation process was optimized by the single factor method.The microscopic morphology,crystal structure,specific surface area,thermal stability,etc.were analyzed using Scanning electron microscope?SEM?,Fourier infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,Thermogravimetric analysis?DSC-TG?,Specific surface area analysis?BET?.The removal processes of methylene blue by two kinds of composite were optimized.The removal mechanism of methylene blue by organic ultrasonically modified and loaded nano-iron attapulgite?DDBAC/ATP/n ZVI?was discussed.The main research works and results are as follows:The first part of the work is to prepare acid-modified and loaded nano-iron attapulgite?H/ATP/n ZVI?composite and apply the material to the adsorption of methylene blue.?1?The best preparation process of H/ATP/n ZVI composite is:purify and acidify the attapulgite,and then use the liquid phase reduction method to load nano-iron,in which the ratio of iron to soil is 1:3,the concentration of KBH₄is 0.075mol/L,reaction time is 3 h.?2?The H/ATP/n ZVI composite has the layered crystal structure of the original attapulgite,the impurities are removed to some extent,and the nano-iron is loaded on the surface of the attapulgite in the form of particles.?3?When the dosage is 2.0 g/L,under the conditions of p H value 4,reaction temperature of 30?,and reaction time of 30 min,the H/ATP/n ZVI composite is suitable for 25 m L 300 mg/L methylene blue,the removal rate can reach 97.02%,and the maximum adsorption removal amount is 158.34 mg/g.The second part of the work is to prepare DDBAC/ATP/n ZVI composite modified with organic ultrasonic modified attapulgite,and discuss the removal process and mechanism of methylene blue in detail.?1?The optimal preparation process of the DDBAC/ATP/n ZVI composite is:select dodecyl dimethyl benzyl ammonium chloride?DDBAC?as the organic modifier,the addition amount is 20mmol/100 g,the purificated attapulgite is calcined at 300?for 1.5 h for organic ultrasonic modification,the ultrasonic time is 20 min,and the nano-iron is loaded on the organic modified attapulgite,the reaction time is 3 h.?2?The DDBAC/ATP/n ZVI composite has the layered crystal structure of attapulgite.The organic modifier has grafted on the attapulgite and made the nano-iron uniformly disperse on the surface of the attapulgite.The composite is stable in 60 days.?3?The 2.0 g/L DDBAC/ATP/n ZVI composite material can achieve a 96.56%removal rate of 25 m L of 150 mg/L methylene blue at a p H of 6,a reaction temperature of 40?,and a reaction time of 30 min,and the maximum removal amount is 111.99 mg/g.?4?The adsorption data of methylene blue by DDBAC/ATP/n ZVI composite conforms to the Lagergren second-order kinetic model and Langmuir model;The calculated thermodynamic parameters?G<0,?S>0,?H>0,it shows that the adsorption process is spontaneous and endothermic reaction.?5?The removal mechanism of methylene blue by DDBAC/ATP/n ZVI composite may be:after the organic modification of the attapulgite,the methylene blue is more easily adsorbed to the surface of the composite,the nano-iron in the composite reacts with the chromogenic group-C=N-in methylene blue,-C=N-is reduced to-C-NH-,and the nano-iron is converted to Fe³⁺.