The Research On The Development Of Natural Materials And The Removal Of Environmental Pollutants

With the development of industrialization,many dye wastewater and arsenic wastewater are discharged into the environment,which poses a serious threat to the environment and human.Kapok fiber,a natural material,is mainly applied in filling materials and oil-absorbing materials.There are little reports on the removal of dye wastewater and arsenic wastewater.Therefore,aiming to make high value use of kapok fibers,three kinds of biomass adsorption materials based on kapok fiber were synthesized and applied to the removal of methyl orange and arsenic in water,and excellent results were obtained in this paper.(1)A novel biosorbent with abundant ammonium groups(KF-DOPAPEI/GA)was synthesized.The raw material,kapok fiber,was modified via the selfpolymerization of dopamine(DOPA)and then glutaraldehyde(GA)and polyethyleneimine(PEI)were cross-linked onto the surface of modified material via the layer-by-layer self-assembly technology.During the self-assembly process of the biosorbent,the response surface methodology was applied to establish the optimum modification conditions.The characterization analysis showed that the content of amine functional groups on the surface of KF-DOPA-PEI/GA increased significantly,which proved the success of the cross-linking reaction;compared with the original kapok fiber,the contact angle of KF-DOPA-PEI/GA decreased sharply,which proved that it changed from hydrophobicity to hydrophilicity.The changed contact angle of KFDOPA-PEI/GA provided the possibility for the removal of pollutants in the later solution.The adsorption tests demonstrated the adsorption kinetics of MO on KFDOPA-PEI/GA was well fitted with by the pseudo-first-order model,which proved the adsorption process was dominated by physical adsorption;the adsorption isotherm could be well explained by the Langmuir isotherm model,which proved the adsorption was monolayer,and the maximum adsorption capacity could reach to 85.02 mg/g.Meanwhile,the biosorbent showed excellent reusability after five cycles.The above experimental results show that KF-DOPA-PEI/GA has potential application value for wastewater containing anionic dyes.(2)For acid arsenic containing wastewater,in this study,kapok fiber(KF)was used as the raw material to produce nanocellulose with abundant carboxyl groups(TEMPO-NC)via hydrolysis oxidation.A novel pH sensitive nanosphere(NC-PEI/GA)was synthesized by crosslinking the nanocellulose with glutaraldehyde(GA)and polyethyleneimine(PEI)in aqueous solution.According to the instrumental analysis,it was found that the nanospheres displayed sensitively to solution pH,especially at pH 3.According to batch experiments,the biosorbent exhibited a rapid rate of adsorption at pH 3 of As(V)and the adsorption kinetic was well fitted with by the pseudo-secondorder model,which proved the adsorption process was dominated by chemical adsorption;the adsorption isotherm could be well explained by the Langmuir isotherm model,which proved the adsorption behavior was monolayer,and the maximum adsorption capacity could reach to approximately 255.19 mg/g at pH 3,which was five times higher than that achieved with the initial pH As(V)solution(44.33 mg/g).Based on the actual situation of the acidic wastewater,the effects of coexisting anions were also investigated,and the results showed that they had little influence on the As(V)adsorption.Additionally,the adsorption efficiency can still reach 100% after eight times of cycles.Finally,the adsorption mechanism of arsenic on NC-PEI/GA was investigated.These results demonstrated that this study provides some ideas for the development of pH sensitive materials,and such a novel material showed a huge potential for arsenic ions removal in the acid wastewater.(3)Inspired by the super stability of iron and arsenic minerals in nature,in this part,using the "bridging" effect of ferrous ions,we successfully cross-linked the nanocellulose(TEMPO-NC)with polyethyleneimine(PEI),and synthesized an iron rich composite(NC-PEI-Fe(II)),and studied its removal effect on arsenic(?/V).The adsorption tests demonstrated the adsorption kinetics of As(?)and As(V)on NC-PEIFe(II)was well fitted with by the pseudo-second-order model,which proved the adsorption process was dominated by chemical adsorption;The adsorption isotherm could be well explained by the Langmuir isotherm model,which proved the adsorption behavior was monolayer,and a high adsorption efficiency towards As(?)and As(V)with the maximum adsorption capacity of 87.70 mg/g and 100.82 mg/g respectively.The above results showed that the iron-based composite material has great potential in the treatment of arsenic containing wastewater and the immobilization of arsenic pollution.