Study On Preparation Of Reduced-charge Lithium Bentonites And Its Adsorption Properties

At present,researchers have been focusing on changing the internal structure characteristics of bentonite to improve its absorption performance.Increasing the surface of the silicone of the bentonite is a way to adjust the internal structure of bentonite characteristics and relevant research shows that the surface of the silicone can absorb organic pollutants.However,the present research on the silicone surface conditioning concentrates on the short carbon chain intercalation of the reduced-charge lithium bentonite while its absorption performance to the small molecule organics which with benzene ring,like phenol and nitrobenzene needs to be further studied.And the reduced-charge lithium bentonite is mainly prepared by the traditional heating method,where the heating temperature is high and the time is long,thus restricting the application of this kind of bentonite in the actual production.Aiming at the existing problems,this paper prepares the reduced-charge lithium bentonite by the means of microwave heating and the process parameters of the preparation process is optimized.At the same time,the reduced-charge lithium bentonite is characterized to prove its internal structure change.And the effects of different reaction conditions on the absorption of Congo red,and methylene blue are studied and the absorption kinetics and the absorption isotherm of the Congo red and methylene blue are analyzed to elucidate its absorption mechanism.Through the relevant experimental data analysis,the following results are obtained:First,the experiment of Preparation and characterization of reduced charge lithium bentonite shows that the microwave heating method can effectively reduce the interlayer charge of lithium bentonite and the decrease of interlayer charge has little effect on the basic structure of montmorillonite.The preparation conditions of 0.80CEC-Li-Bent were: Q = 40 W / g,t = 8min;0.67CEC-Li-Bent was prepared by the following conditions: Q = 80 W / g,t = 4min;The preparation conditions of 0.44CEC-Li-Bent were: Q = 80 W / g,t = 8 min.The energy consumption and the time required for preparation are significantly less than those of conventional heating methods.In the process of microwave heating,the lithium ion expels water and comes into the montmorillonite crystal layer structure,thus making the interlayer charge decrease gradually.In the process of reduced charge,montmorillonite crystal structure appears a little change.The process of microwave charge reduction makes the water molecules evaporate which is on the silicone suiface,and the lithium ion migration also makes the silicone surface to be exposed.The interaction between the interlayer ions decreases,and the pores with a large number of siloxane surfaces between the layers are formed.When the interlayer charge is further reduced to 0.44 times the original,although the layers have collapsed,the montmorillonite crystal layer structure is still complete.Second,the experiment of the effect of reduced charge on the red absorption of Congo red clay shows that:The absorption effect of the reduced charge lithium bentonite o n the 100 mg / L Congo red solution increases with the decrease of the interlayer charge.For the 0.44CECLi-Bent,when the p H value is 6 and the dosage is 1.6 g / L,the reaction time was 60 mins,the absorption rate is 94.6%.The absorption of Congo red is consistent with the quasisecond order kinetic model,the intra-particle diffusion model and the Freundlich absorption isothermal model.That is to say,the absorption of Congo red is mainly nonhomogeneous surface absorption.So the effect of the reduced charge on the direct dye is better than that of the acid dye and the reactive dye.Third,the experimental results of the absorption of methylene blue show that :The absorption of 200 mg / L methylene blue solution shows that the reduced charge lithium bentonite absorption rate of methylene blue is lower than that of lithium bentonite and decreases with the decrease of interlayer charge.The absorption rate of 200 mg / L methylene blue solution is 99.9% when the solution p H is 8,the dosage is 0.6g / L an d the reaction time is 60 mins.The absorption of methylene blue is consistent with the qu asisecond order kinetic model,the intra-particle diffusion model and the Langmuir absorption isothermal model.In other words,the methylene blue molecules can exchange the cations between the bentonite layers,so the effect of the reduced charge of the lithium bentonite on the methylene blue decreases with the decrease in the charge between the layers.