Study On Removal Of Hexavalent Chromium From Water By Composite Aerogel Used Paper Cellulose

Chromium is a common transition metal.It is widely used in industries such as tanning,electroplating,metallurgy,textile,printed circuit board and metal surface treatment,which brings great economic benefits and causes serious chromium pollution.The common valence states of chromium are Cr(Ⅵ)and Cr(Ⅲ),which Cr(Ⅵ)has high toxicity and carcinogenicity.At present,the common treatment methods of hexavalent chromium include physical,chemical and biological removal method,which adsorption method and chemical reduction method are two simple and widely applicable removal methods.The selection of adsorption materials and return raw materials is particularly important for the two removal methods.Cellulose aerogel is a kind of material with porous structure which is prepared from cellulose based material.It has high specific surface area and porosity,chemical modification and surface modification can increase the active groups on the surface which are beneficial to the adsorption and conversion of heavy metals.It has a good application prospect in the field of adsorption material and carrier material.In this study,cellulose aerogel was prepared with recycled paper cellulose as raw material and functionalized to improve its adsorption and reduction performance for Cr(Ⅵ)removal in water.The specific work is mainly divided into the following three parts:(1)In this study,CA was prepared from recycled paper cellulose,and polyethylenimine(PEI)was used as functionalized agent to prepare polyethylenimine/ paper cellulose composite aerogel(CA/PEI)through Mannich chemical reaction.The morphology and structure of the adsorbent were characterized by SEM,FT-TR,TG,BET and XPS.The results showed that the adsorbent had a networked porous structure and nitrogen-containing functional groups.The CA/PEI was used as adsorbent for the removal of Cr(Ⅵ)from aqueous solution.Results showed the adsorption capacity of Cr(Ⅵ)reached 17.6 mg/L when the concentration of Cr(Ⅵ)was 10 mg/L and the material dosage was 0.5 g/L,which was 4 times higher than that before functionalization.The results showed that adsorption was in accordance with pseudo-second-order kinetics model and Langmuir adsorption isotherm parameters.(2)In this study,paper cellulose aerogel(CA)was prepared by using recycled paper cellulose as raw material.Zero-valent iron particles with reduction performance were grown on aerogel by sodium borohydrate liquid phase reduction method,then zero-valent iron / paper cellulose composite aerogel(CA/ZⅥ)with reducing performance was prepared.The morphology and structure of the adsorbents were characterized by SEM,XRD,TG,BET and XPS.The results showed the aerogel presented a network like porous structure and loaded with zero-valent iron particles on the surface.The CA/ZⅥ was used as the removel agent for the removal of Cr(Ⅵ)in aqueous solution.The results showed that Cr(Ⅵ)was reduced to Cr(Ⅲ),and the removal rate of Cr(Ⅵ)could reach 96.4% within 1 hour when the concentration of Cr(Ⅵ)was 10 mg/L and the material dosage was 0.75 g/L.The adsorption results showed the adsorption was in accordance with the pseudo-first-order kinetics model and Langmuir adsorption isotherm parameters.(3)This experiment with paper cellulose as raw material preparation of CA,poly dopamine / sulfide modified zero-valent iron / paper cellulose composite aerogel(CA/PDA/S-ZⅥ)was prepared by loaded polydopamine and sulfide modified zero-valent iron sulfide on the surface of CA.The morphology and structure of the adsorbent were characterized by SEM,FT-TR,XRD,XPS,TG and BET.The results showed the aerogel presented a networked porous structure and loaded with PDA and S-ZⅥ particles on the surface.The aerogel was used as an adsorption agent for the removal of Cr(Ⅵ)from aqueous solution.The results showed the aerogel has the ability of reduction and adsorption on Cr(Ⅵ),when the Cr(Ⅵ)concentration is 10mg/L and the material dosage is 0.75 g/L,the removal rate of Cr(Ⅵ)reached 98.2%within 1 hour.The results showed the adsorption was in accordance with the pseudo-second-order kinetics model and Langmuir adsorption isotherm model.