Preparation Of Cellulose Based Hydrogels And Study On Adsorption Of Methylene Blue Dye And Heavy Metal Ions

With the development of dyestuff and textile industry,the effluents from these industries usually contain dyes and heavy metal ion,which cannot be removed by conventional processes are carcinogenic and possess a potential health hazard to all forms of life.Usually,physical method,chemical method,biological method and physical and chemical combined processing are used in effluents treatment.Among them,the adsorption method plays an important role in the treatment of dyes heavy metal ion wastewater because of its advantages such as simple operation,low investment cost,good selectivity and excellent removal effects.Hydrogel,with three-dimensional network structure,is a high-molecular polymer,which can be used as a kind of adsorption materials.With high water absorbability,sensitive to temperature and pH,environment friendly,hydrogel plays an important role in the adsorption of dyes heavy metal ion wastewater treatment,especially biodegradable composite hydrogel for industrial wastewater treatment has caused wide attention of scholars.In this study,carboxymethyl cellulose(CMC),gelatin(GEL)and montmorillonite(MMT)were used as raw materials,glutaraldehyde as crosslinking agent,to prepare cellulose based new hydrogel composite.The influence of the amount of each component in hydrogel composite on the swelling rate was studied.XRD,SEM,TG and FTIR were used to characterized the composite structure of the hydrogel.The adsorption properties of hydrogel composite for methylene blue(MB)and series heavy metal ions(Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ),Cr(Ⅲ))were studied.This study is divided into the following aspects:(1)CMC-GEL/MMT hydrogel composite was prepared with CMC,GEL and MMT as raw materials and glutaraldehyde as cross-linking agent.The influence of the amount of each component of the hydrogel composite on the swelling rate was studied.The results showed that the swelling rate of CMC-GEL/MMT hydrogel composite was positively correlated with the increase of the mass fraction of CMC and MMT while negatively correlated with the increase of GEL dosage,with first increased and then decreased trend as the dosage of glutaraldehyde increased.By investigating the swelling rate and mechanical properties,the compose of CMC、GEL、MMT and glutaraldehyde in the composite hydrogel was 40%,60%,5%(mass fraction of CMC-GEL)and 0.50%(mass fraction of CMC-GEL),respectively.The results of XRD,SEM,FTIR and other characterizations showed that CMC-GEL/MMT formed network structure under the cross-linking action of glutaraldehyde.(2)The cationic dye methylene blue(MB)was adsorbed by CMC-GEL/MMT hydrogel composite.The sorption experiment results showed that when initial concentration of MB was 100mg/L,pH was 7,amount of adsorbent was 4.3 g/L,adsorption temperature was 30℃,adsorption time was 90 min,the adsorption capacity was 20.91 mg/g.(3)The prepared CMC-GEL/MMT hydrogel composite were used to adsorb heavy metal ions(Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ),Cr(Ⅲ)),and the results showed that the adsorption effect of CMC-GEL/MMT hydrogel composite on heavy metal ions(Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ),Cr(Ⅲ))was best when the hydrogel composite in mass fraction of CMC,GEL,MMT were 40%,60%,5%(mass fraction of CMC-GEL),respectively.However,CMC-GEL/MMT hydrogel composite had the worst adsorption effect on heavy metal ions(Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ)and Cr(Ⅲ))when the mass fraction of CMC,GEL and MMT was 20%,80% and 0%(mass fraction of CMC-GEL),respectively.The optimum adsorption conditions for Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ)and Cr(Ⅲ)by hydrogel composite were: initial concentration of four kinds of metal ions was 150 mg/L,pH was 5,adsorbent dosage was 4.3 g/L,adsorption temperature was 30 ℃,the adsorption time was 90 min,adsorption of Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ),Cr(Ⅲ)were 32.72 mg/g,24.44 mg/g,26.01 mg/g and 28.03 mg/g,respectively.(4)Through the study of adsorption thermodynamics and kinetics,the results showed that the adsorption of CMC-GEL/MMT hydrogel composite for MB conforms to the pseudo-second-order kinetics model,and the adsorption isotherm conforms to the Langmuir isotherm model(monomolecular layer adsorption).(5)Through the study of adsorption thermodynamics and kinetics,the results showed that the adsorption of heavy metal ions(Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ),Cr(Ⅲ))by CMC-GEL/MMT hydrogel composite all accord with the pseudo-second-order kinetics model,and the adsorption isotherm accord with the Langmuir isotherm model(monomolecular layer adsorption).(6)The adsorption of mixed heavy metal ions(Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ),Cr(Ⅲ))by CMC-GEL/MMT hydrogel composite was studied,the results showed that adsorption of the three mixed metal ions adsorption amount was lower than that of single adsorption quantity,and three kinds of metal ions adsorption in the mixed adsorption amount of Cu(Ⅱ)> Pb(Ⅱ)> Cd(Ⅱ).On this basis,the adsorption of Cu(Ⅱ)by the hydrogel composite was studied.The results showed that after three cycles,the removal rate of Cu(Ⅱ)by the hydrogel composite was still 69.48%,indicating that the prepared hydrogel composite had a good regeneration performance.