Preparation And Modification Of Biochar From Pepper Straw And Its Adsorption Properties For Organic Dyes

Due to the rapid development of printing and dyeing industry,China has become the country with the largest dye production in the world.At the same time,the discharge of organic dye wastewater will not only do great harm to the living environment,but also pose a certain threat to their own health through human production and social activities.At present,for the removal of organic dyes in water environment,adsorption method is widely accepted and applied.Among many adsorbents,biochar is favored by water pollution remediation because of its wide source,simple preparation method,low cost and excellent adsorption performance.In this thesis,the agricultural waste pepper waste straw in Handan area was selected as the original biomaterial to prepare biochar,and the optimal carbon was modified with alkali and zinc chloride.Various methods were used for characterization.Under the controlled conditions of different environmental factors,the acid dye Coomassie brilliant blue（CBB）and alkaline dye malachite green（MG）in the solution were removed respectively.The adsorption properties of various biochar for different types of organic dyes were comprehensively investigated,and the absorption mechanism was studied.The main research contents and conclusions include:（1）Raw biochar PC400,PC550 and PC700 were prepared at different pyrolysis temperatures;The modified carbon PC-1M,PC-2M and PC-4M were obtained by modifying biochar with carbon alkali ratio under Na OH condition;Pepper straw was modified with different concentrations of Zn Cl₂solution,and modified carbon PC-0.5L,PC-1L and PC-2L were prepared at the optimal pyrolysis temperature.（2）Characterization analysis was carried out by various means.The specific surface area of PC700 biochar is larger.Both modification methods can expand the specific surface area and make the carbon pores more developed;Alkali modification can improve the type and quantity of surface functional groups;Alkali modification will not change the crystal structure of biochar,but zinc chloride modification will convert biochar into composite biochar materials.（3）Through the single factor optimization experiment,it can be concluded that in the adsorption of biochar to CBB,the adsorption equilibrium is reached when the carbon dosage is 3g/L and the solution p H is 5 and 120min;For MG,the adsorption equilibrium is reached when the carbon dosage is 1 g/L,the solution p H is 4 and 60min,and the adsorption capacity of PC700 is the strongest.In the adsorption of CBB by alkali modified carbon and zinc chloride modified carbon,when the carbon dosage is1.5 g/L,the p H is adjusted to 4 by alkali modified biochar and 5 by zinc chloride modified carbon,the adsorption equilibrium is reached at 60min;For MG,the adsorption equilibrium is reached when the carbon dosage is 1 g/L,the solution p H is 4and 60min.Among them,PC-2M and PC-2L have the best adsorption performance.（4）Pseudo second-order kinetics can well explain the adsorption process of various biochar on different types of organic dyes,which also shows that the process is completed under the dual influence of physical adsorption and chemical adsorption.The fitting results of the adsorption isothermal model are more in line with the Langmuir model,and the maximum adsorption capacity Q_mof PC700,PC-2M and PC-2M dominant carbons for CBB is 20.51mg/g,48.54mg/g and 58.48mg/g respectively,and the maximum adsorption capacity Q_mfor MG is 175.44mg/g,714.28mg/g and833.33mg/g respectively.（5）According to the adsorption experimental results and fitting parameter analysis,the adsorption mechanism of biochar and organic dyes is mainly in the form of pore adsorption,π-πelectron donor receptor interaction and electrostatic attraction,and there may also be hydrogen bond.