Preparation And Adsorption Properties Of Organic/Inorganic Composite Gel Materials

Among various wastewater treatment methods,adsorption method is widely used because its simple operation,low cost and high performance.Natural or synthetic micro-nano powder materials(such as clay minerals,metal-organic frameworks(MOFs))have unique small size effects,surface and interface effects,and exhibit good adsorption properties.However,after completing the adsorption of dyes in the water body,it is often to use filtration or centrifugation to separate these micro-nano-scale powder materials from th e water body.The separation process is difficult and easy to cause secondary pollution,which seriously limits the practical application of micro-nano materials in dye wastewater treatment.How to fully exploit the adsorption properties of micro-nano materials and improve their solid-liquid separation properties is the key issue,in this paper,two nano-powder materials(MOFs and natural nano-clay minerals)were introduced into the solid-liquid separation through in-situ chemical cross-linking reaction.In the highly swollen hydrogel threedimensional network structure,organic/inorganic composite gel adsorbents were prepared,and their removal behavior for typical organic dyes in water was studied,in order to provide a useful reference for the development of new adsorption materials based on micro-nano powders.The specific work carried out is as follows:1.UiO-66 nanoparticles with extremely strong stability and good adsorption as adsorption functional materials,Polyacrylamide/UiO-66(referred to as PAM/UiO-66)composite gel adsorption was prepared by aqueous solution radical polymerization.The successful preparation of PAM/UiO-66 was verified by FTIR,SEM and XRD characterization methods.Using the anionic dye methyl orange(MO)as a model dye,the adsorption behavior of PAM/UiO-66 composite gels was studied.The effects of adsorbent dosage,the initial pH valu,contact time and initial concentration of MO solution on the adsorption process were investigated respectively.The adsorption kinetics and adsorption thermodynamic characteristics of PAM/UiO-66 composite gel for MO were analyzed.At the same time,the solid-liquid separation characteristics and recycling performance of PAM/UiO-66 composite gel were evaluated.The results show that:UiO-66 in PAM/UiO-66 composite gel can give full play to its adsorption properties;pseudo-second-order kinetics can describe the adsorption process of PAM/UiO-66 composite gel for MO well,and the adsorption isotherm According to the Langmuir model,the calculated maximum adsorption capacity was 52.13 mg/g.The adsorption process is an endothermic spontaneous process.Millimeter-sized PAM/UiO-66 composite gel particles settled on the bottom of the water naturally,showing good solid-liquid separation characteristics and recycling performance.2.In order to reduce the cost of composite adsorbents and reduce the dependence on petroleum-based small-molecule monomers,the natural one-dimensional nano-mineral attapulgite(ATP)was used as the inorganic functional component,The pullulan/attapulgite composite(referred to as PU/ATP)gel material was prepared by in situ chemical cross-linking of natural pullulan polysaccharide.Based on the successful preparation,the adsorption behavior of PU/ATP composite gel for the cationic dye crystal violet(CV)was studied.The results show that the ATP in the PU/ATP composite gel can effectively exert its adsorption function.For low-concentration CV dye solutions,the PU/ATP composite gel showed a good removal effect.The pseudosecond-order kinetic model can better describe the adsorption kinetic process,the adsorption isotherm conforms to the Langmuir model,and the calculated maximum adsorption capacity is 13.13 mg/g.The adsorption thermodynamic results indicated that the adsorption of CV on the PU/ATP composite gel was an exothermic spontaneous process.The millimeter-scale PU/ATP composite gel particles have excellent sedimentation characteristics,showing good solid-liquid separation characteristics and recycling performance.After repeated use for 5 times,the adsorption capacity can still reach 83.86%of the initial adsorption capacity.3.In order to further improve the adsorption performance of attapulgite(ATP)-based composite gels,on the basis of attapulgite(ATP)as an inorganic functional component,AMPS and P(AMPS-co-IA)/ATP composite gels were prepared by the free-radical copolymerization of the biobased monomer itaconic acid(IA).The adsorption behavior of the cationic dye crystal violet(CV)on the P(AMPS-coIA)/ATP composite gel was studied.The results showed that the P(AMPS-co-IA)/ATP composite gel exhibited a good removal effect for low-concentration CV dye solutions.The three kinetic models are in good agreement with the adsorption kinetic process,the adsorption isotherm is in accordance with the Langmuir model,and the calculated maximum adsorption capacity is 512.82 mg/g.The adsorption thermodynamic results indicated that the adsorption of CV on the P(AMPS-co-IA)/ATP composite gel was an exothermic spontaneous process.The millimeter-scale P(AMPS-co-IA)/ATP composite gel particles have good sedimentation characteristics,showing excellent solid-liquid separation characteristics and recycling performance,and the adsorption capacity can still reach 109.51 mg/g after repeated use for 5 times.