| With the development of society and economy,a large amount of organic dye wastewater has been produced in many industrial fields,which leads to more and more serious environmental problems such as water pollution.In recent years,advanced oxidation technology(AOPs)based on sulfate radical(SO4-.)has shown broad application prospects in the field of organic wastewater treatment,which is highly toxic and difficult to biodegrade due to its characteristics of high efficiency,convenience and good applicability.It has become a new attracting wastewater treatment process.At present,peroxide monosulfate(PMS)has been widely used as an oxidizing agent in sulfate radical based advanced oxidation technology(SR-AOPs)to provide SO4-.,but the rate of reaction between PMS and pollutants without catalysis is too slowly.Novel cobalt-based metal organic framework materials(MOFs)have been developed for SR-AOPs to degrade organic pollutants in water,and the reaction system composed of MOFs and PMS can produce SO4-.with strong oxidizing properties.However,MOFs are mostly powdered materials at micro and nano levels,which are not easy to be recycled after the reaction.At present,some studies have taken aerogel material as the skeleton and supported MOFs on aerogel by in-situ growth method,which not only solved the problem of its difficult recovery,but also gave the composite aerogel a good ability of adsorption and catalytic degradation of organic dye wastewater.In recent years,carboxymethyl cellulose(CMC)based aerogels,as one of biomass aerogel adsorbents,have been widely used because of its low density,high specific surface area and good biocompatibility,but its poor mechanical stability for the application in dye wastewater treatment is often limited.Graphene oxide(GO)is rich of rigid structure and the oxygen containing groups of benzene ring,the surface characteristics make it easy to through their own interface self-assembly to form macroscopic three-dimensional materials,combined with CMC is the preparation of aerogel can give this material must be structural strength,at the same time improve the adsorption performance,therefore,this paper puts forward the CMC and GO composite,choose poly(methyl vinyl ether-alt-maleic acid)(PMVEMA)and polyethylene glycol(PEG)of polymer crosslinking system,the CMC and GO stronger together,The composite aerogel with excellent adsorption performance and structural stability was prepared by the guided freeze-drying method,and the aerogel catalytic material supported cobalt-based metal organic framework ZIF-67 was further prepared by the in-situ growth method,which was used as the catalyst for the catalytic degradation of organic dyes by PMS.The structural stability,adsorption and catalytic degradation capacity of aerogels were studied,and the process of catalytic degradation of organic dyes was further analyzed.The specific research contents are as follows:(1)Pure CMC aerogel and CMC/rGO composite aerogel were prepared by means of a guided freeze-drying method with a PMVEMA/PEG cross-linking system,and the amount of GO was changed to prepare composite aerogel(Cro-CMC/rGO)with different proportion of GO.The structural and mechanical properties of different aerogels were compared.It was found that the addition of GO,the introduction of cross-linking system and the guided freeze-drying method effectively improved the structural stability of aerogels.The adsorption of methylene blue(MB)by Cro-CMC/rGO aerogels with different GO supplemental amounts was studied.The results showed that the Cro-CMC/rGO aerogels exhibited the best adsorption capacity for MB at 25℃ with pH=7,and the maximum adsorption capacity reached 871.48 mg/g.Kinetic and isothermal adsorption simulations of the adsorption process were carried out,and it was found that the process was spontaneous according to the quasi-second-order kinetic model and Langmuir isothermal adsorption model.In addition,the composite aerogel showed good recycling performance.(2)In order to give aerogel a certain catalytic degradation performance,the ZIF-67@Cro-CMC/rGO composite aerogel was prepared by in-situ growth method using Cro-CMC/rGO aerogel as skeleton material.Because adsorption simply transfers dye molecules from medium A to medium B,it cannot fundamentally solve the problem.Therefore,the reaction system composed of ternary composite aerogel and oxidant PMS is expected to achieve deep degradation of dyes in SR-AOPs.The catalytic degradation of dye wastewater by ZIF-67@Cro-CMC/rGO aerogel and the stability of its structure and properties were studied.The results show that the composite aerogel can effectively catalyze the degradation of dyestuff wastewater,and can achieve the complete degradation of MB within 5 min,and can maintain the catalytic activity in a wide pH range,and the reaction conditions are easy to achieve,and the composite aerogel shows good recycling performance.(3)In order to further evaluate the stability of the structure and performance of ZIF-67@Cro-CMC/rGO aerogel and study the degradation of dye wastewater treatment principle,we compared and analyzed the morphology structure of the aerogel circulation before and after using,in addition,also by electron paramagnetic resonance(EPR),inductively coupled plasma emission spectrometer(ICP-OES)methods to explore the reaction system to complete the necessary conditions of catalytic degradation.It was found that the aerogel retained its excellent structure and properties after repeated use.When ZIF-67@Cro-CMC/rGO aerogel was applied to SR-AOPs,ZIF-67 in the reaction system could catalyze PMS to produce SO4-.and ·OH two kinds of strong oxidizing radicals,which could degrade the dye macromolecules and reduced its toxicity.Further study found that SO4-.played a major role in the two kinds of free radicals.In addition,it was found that this material also showed excellent catalytic degradation of RhB.The above research results provide some theoretical support for the application of MOFs aerogel in the treatment of dye wastewater by SR-AOPs. |
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