Study On The Characterization Of Biochar Prepared By Different Biomass And Adsorption Of Cr(?) And Azo Dyes

Biochar is a kind of solid material with high stability,aromaticity and abundant carbon.It is made up of biological residues which is prepared by high temperature slow pyrolysis(<700?)or hydrothermal carbonization under low temperature or low oxygen content.Since the emergence of"biological carbon"concept,due to the excellent characteristics of biological carbon,related research has been widely concerned.In particular,with the concept of sustainable agricultural development,the potential value of biological carbon has been further expanded,and theoretical research and technological development are constantly improved.In this paper,wheat straw and municipal sludge were used as biomass sources.The composition and structure of biochar prepared under different cracking conditions were analyzed.The best cracking conditions were screened.Zinc chloride was used to activate the straw biochar and sludge biochar separately,the changes of biochar struction and adsorptive property after activation were observed.There are many studies on municipal sludge activated carbon adsorption of acid red GR,but few studies on wheat straw activated carbon adsorption of acid red GR.The factors influencing the adsorption of Cr(?)and acid scarlet GR were discussed.The adsorption capacity of wheat straw and municipal sludge biochar on heavy metal Cr(?)and azo dye acid red GR under the optimal adsorption condition was compared for the first time.The conclusions were as following:1.During the preparation of biological carbon,the cracking temperature has a great influence on the structure composition of biological carbon.When the cracking temperature rises,the carbonization of biomass materials is more complete and the aromaticity is higher.The hydrophobicity of biological carbon is gradually increased with the increase of cracking temperature,while the polarity of biological carbon decreases with the increase of cracking temperature.The surface area of biological carbon rises first and then decreases with the increase of cracking temperature,and the pore volume increases gradually.The best cracking temperature of straw biochar is 500?,cracking the straw biochar for 1 h under this condition,the yield of biochar is 31.63%,the specific surface area is 70.57 m~2/g,and the pore volume is 0.63 cm~3/g.The best cracking temperature of sludge biochar is 500?,cracking the sludge biochar for 1 h.under this condition,the yield of biochar is 65.02%,the specific surface area is 19.37 m~2/g,and the pore volume is 0.056cm~3/g.Straw biochar and sludge biochar that activated by Zinc chloride respectively,the number of micropores increased obviously than before.SEM scanning observation was used to prove that their productivity is increased.The experimental data show that specific surface area and pore volume all increased to varying degrees.2.When the cracking temperature is 500?,and the cracking time is 1 h,the order of straw biochar and sludge biochar functional groups from large to small is:lactone>carboxyl>phenol hydroxyl>carbonyl.Due to the presence of these functional groups,two kinds of biological charcoal have better adsorption capacity for Cr(?)and acid red GR.The best adsorption conditions for Cr(?)by straw biochar and sludge biochar were as follows:The initial concentration of Cr(?)is 100 mg/L,pH is 2,the adsorption time is4 h,and the dosage of biological carbon is 0.8 g.The best adsorption conditions for acid red GR by straw biochar were as follows:pH was 2,adsorption time was 40 min,and the dosage of biological carbon was 0.6 g;The best adsorption conditions for acid red GR by sludge biochar were as follows:pH was 2,adsorption time was 50 min,and the dosage of biological carbon was 0.8g.The adsorption methods of Cr(?)and azo dyes on wheat straw and municipal sludge biochar were mainly monolayer physical adsorption,which was consistent with Langmuir isothermal adsorption model.Under the optimal adsorption conditions,the adsorption capacity of wheat straw biochar to Cr(?)and azo dye acid red GR was better than that of municipal sludge biochar.In this study,biochar was made from reclaimed wheat straw and municipal sludge,and the activation process and raw materials of biochar with stronger adsorption capacity for heavy metals and azo dyes were screened out through comparison.On the one hand,the preparation of biochar solves the problem of disposal and disposal of crop residues and solid wastes.On the other hand,biochar as adsorbent material can adsorb heavy metals and organic pollutants,and control environmental pollution.To sum up,the research and development of biological carbon in this paper has very great environmental and economic benefits.