Preparation Of Zr,Al,Fe Modified SBA-15 And Its Performance On The Adsorption-Oxidation Of Methylene Blue In Water

Organic wastewater is harmful to the environment,and the removal of wastewater containing organic matter is still the focus of research.Adsorption and Fenton-like catalytic oxidation reaction are two methods that are widely studied at present,in which adsorbents and catalysts are the key factors of wastewater treatment.The operating conditions of adsorption are mild,but the regeneration of adsorbents is the key to the application of adsorption.Fenton-like reaction uses H2O2 as oxidant to catalyze the oxidation of organic pollutants in water,but Fenton-like reaction usually has a good catalytic oxidation effect above 50?.Because of the high energy consumption,it is not suitable for the treatment of a large number of wastewater.Therefore,this paper will combine the advantages of adsorption and Fenton-like reaction to prepare bifunctional materials to improve the treatment effect of organic wastewater,that is,organic matter is adsorbed on the adsorbent,and then the adsorbent is oxidized by catalytic oxidation,and the adsorbent is regenerated at the same time.Dye wastewater is not easy to be biodegraded,so the wastewater containing methylene blue(MB)is selected as the treatment object in this paper.As a mesoporous material,SBA-15 has two-dimensional hexagonal pore structure,large pore size and good hydrothermal stability,so it can be used as an excellent carrier.In this paper,the adsorption of methylene blue by Zr and A1 modified SBA-15 and the catalytic oxidation performance of Fe modified SBA-15 were studied,and the synergistic effect of adsorption and oxidation was discussed.(1)Zr-SBA-15 was prepared by one-step hydrothermal synthesis and two-step hydrothermal pH adjustment method(marked as Zr-SBA-15(?)and Zr-SBA-15(?)respectively).The characterization of XRD,BET,SEM and TEM showed that the distribution of Zr elements in the Zr-SBA-15 prepared by the two methods was uniform,in which the Zr-SBA-15(?)prepared by one-step synthesis changed into a flake-like structure with short pores,and the Zr-SBA-15(?)prepared by two-step hydrothermal pH adjustment method retained the rod-like morphology of traditional SBA-15.UV-Vis DRS results showed that Zr species entered the framework of SBA-15.The adsorption experiment of MB shows that the adsorption performance of Zr-SBA-15(?)for MB is better than that of Zr-SBA-15(?).The order of MB removal rate is Zr-SBA-15(?,0.05)>Zr-SBA-15(?,0.1)>Zr-SBA-15(I,0.025)>Zr-SBA-15(I,0.15).Under the suitable experimental conditions(adsorption time 60 min,adsorbent dosage 40 mg,pH 5.3,MB solution 100 mL,concentration 40 mg/L),the removal rate of MB by Zr-SBA-15(I,0.05)reached 99.6%.According to the adsorption kinetics and adsorption isotherm experiments,the adsorption process of MB on Zr-SBA-15 conforms to the pseudo-second-order kinetic equation and Langmuir model.(2)Al-Zr-SBA-15 modified by Al and Zr was prepared by one-step hydrothermal synthesis.The characterization of XRD,BET,SEM and TEM showed that Al and Zr elements were uniformly distributed in SB A-15,which did not destroy the mesoporous structure of SBA-15 and maintained the flake morphology of Zr-SBA-15.UV-Vis DRS results showed that most of Al and Zr entered the framework of SBA-15.The NH3-TPD results show that the acidity of SBA-15 is improved by the introduction of Al,and the adsorption performance of Al-Zr-SBA-15 to MB is obviously better than that of Zr-SBA-15.Under the suitable experimental conditions(adsorption time 60 min,adsorbent dosage 30 mg,pH 5.3,MB solution 100 mL,concentration 40 mg/L),the removal rate of MB reached 99.8%.According to the adsorption kinetics and adsorption isotherm experiments,the adsorption process of MB on Al-Zr-SBA-15 conforms to the pseudo-second-order kinetic equation and Langmuir model.(3)Fe-Zr-SBA-15 modified by Fe and Zr was prepared by a two-step hydrothermal pH adjustment synthesis.BET analysis shows that the introduction of Fe and Zr elements does not destroy the mesoporous structure of SBA-15.The characterization results of XRD,SEM and TEM showed that the introduction of Zr helps to improve the dispersion of Fe,which makes the distribution of Fe and Zr elements on SBA-15 more uniform.The results of UV-Vis DRS characterization showed that Zr could change the existence form of Fe on SBA-15,so that most of Fe and Zr species entered the framework of SBA-15.The adsorption-oxidation MB experiments by Fe-Zr-SBA-15,Zr-SBA-15 and Fe-SBA-15 were investigated.In the adsorption stage,the adsorption removal rates of MB by Fe-Zr-SBA-15,Zr-SBA-15 and Fe-SBA-15 were 44.2%,45.1%and 19.9%,respectively.In the oxidation stage,the total removal rates of MB were 97.5%,52.5%and 50.8%,respectively.Generally speaking,Fe-Zr-SBA-15 has the best removal effect on MB.When Fe-Zr-SBA-15 as catalyst and H2O2 as oxidant,Fe-Zr-SBA-15 dosage,reaction temperature,pH value of solution and amount of H2O2 on the removal rate of MB were investigated.Under the suitable reaction conditions(reaction time 200 min,amount of catalyst 30 mg,pH 5.25,MB solution 150 mL,50?,concentration 50 mg/L,H2O2 0.6 mL),the MB removal rate reached 99.9%.Through repeated experiments,it is known that the MB removed in the adsorption stage is further degraded in the catalytic oxidation stage.Through the four-cycle experiments of Fe-Zr-SBA-15,the removal rates of MB are 98.1%,93.6%,89.6%and 83.8%,it shows that Fe-Zr-SBA-15 has good stability.