Preparation Of Peanut Shell Biochar Electrode And Electrochemical Properties Of Water Treatment

Water is one of the most important resources for human survival and development,but due to the rapid development of industrial activities and agricultural production and economy,a large amount of polluted industrial wastewater and domestic sewage are discharged into the living environment without treatment,leading to increasingly serious water pollution and threatening the safety of human and ecosystems.This kind of wastewater often contains both organic and inorganic pollutants.How to remove these two types of pollutants efficiently is an urgent problem.In recent years,low-cost and high-efficiency electrochemical technologies have become popular research in water treatment.Among them,electro-Fenton technology is to use the generated-OH degradation of organic pollutants,capacitive deionization technology is under the action of electrostatic field,so that the charged ions in the solution to move to the opposite electrode,and combined with the electrode to achieve the purpose of purifying the solution.These two technologies have the advantages of low energy consumption,high removal rate and green environment.However,both technologies require cathode materials with good performance.In the current context of environmental sustainability,it is very important to use a low-cost,effective and simple method to make electrodes.Biochar has promising applications in environmental remediation,soil improvement and wastewater treatment.Due to its stable structure,large specific surface area and pore volume,and abundant active functional groups,biochar is widely used for decolorization of wastewater and removal of heavy metals and other inorganic pollutants.The resulting topic:peanut shell biochar electrode preparation and electrochemical performance for water treatment,is a fundamental theoretical research topic of great significance.The specific research work carried out in this thesis is as follows.1.Synthesis,electrode preparation and characterization of peanut shell biocharIn this study,a new porous biochar material is prepared by hydrothermal carbonization and activation of Zn Cl₂ molten salt with peanut shell as raw material without additional nitrogen source.Z0、Z1、Z2、Z3 and Z4 are obtain by Zn Cl₂ in the proportions of 0、1:1、1:2、1:3、1:4.SEM characterization shows that the biochar activated by molten salt formed micropores on the surface of the etched materials.BET test results shows that the specific surface area of the activated biochar Z3(950 m²·g^-1)is much larger than that of the unactivated biochar Z0(307 m²·g^-1).With the increase of molten salt,the specific surface area and pore size also increase.XPS characterization results shows that there are N elements in Z3,including pyridinic-N（11.8%）and graphitic-N（88.2%）.EIS results show that with the increase of the molten salt ratio,the Rct value decreases first and then increases.When the molten salt ratio is 1:3,the minimum impedance is 3.04 ohm.2.Peanut shell biochar material for degradation of X3B and 2-CP by Electro-Fenton techniqueIn this work,the prepared peanut shell biochar is used as a cathode for the degradation of dyes X3B and 2-CP by electro-Fenton,and their application in real water bodies is also investigated.The Z3 electrode shows good electrochemical performance with a maximum yield of 1.3 mmol·L^-1 of H₂O₂ and a corresponding current efficiency of 43.5%.In the degradation of X3B,the kinetic constant of the reaction is 1.4 times higher than that of Z0,and the removal rate of X3B reach 95%after 15 min;in the degradation of 2-CP,2-CP is completely degraded within 10 min and the removal rate reach 100%.The results show that the degradation of X3B and 2-CP in two real water bodies,namely,Donghu Lake water and Yangtze River water,has a good effect,and the removal rate of X3B and 2-CP can reach 100%.3.Peanut shell biochar material for Cu²⁺removal by capacitive deionization techniqueIn this chapter,a homemade CDI device is developed to use peanut shell biochar for capacitive deionization experiments to remove Cu²⁺.The optimal conditions of voltage,flow rate and concentration and the capacitive properties of the material are investigated to study the adsorption mechanism and the effects of monovalent and divalent ions on the effect of Cu²⁺removal.The optimal conditions are deter mined as follows:working voltage of 1.4 V,inlet flow rate of 2 m L/min and initial concentration of 50 mg/L.CV tests show that the prepared Z3 samples maintain a good rectangular shape of the CV curve at a high scan rate(100 m V·s^-1),and their specific capacities are up to 183 F/g.Compared with Z0 and commercial carbon（VXC-72）,the removal rate of Cu²⁺by Z3 is 95.8%,67.9%and 27.1%higher than that by Z0（27.9%）and VXC-72（68.7%）,respectively.The adsorption capacity of Z3（64.7 mg/g）was also much higher than that of Z0（17.2 mg/g）and VXC-72（41.5 mg/g）.Quasi primary adsorption kinetics,Elovich and Weber-Morris adsorption kinetics are fitted to the Z3 electrode adsorption process,and the results can well describe the whole stages of the electroadsorption process.The effects of monovalent and divalent metal ions on the adsorption of Cu²⁺under the same conditions are found to be greater than the effects of monovalent metal ions on the adsorption of Cu²⁺.