Adsorption Performance And Experimental Study Of Pb²⁺ And Cd²⁺ On Modified Antibiotic Residue Hydrochar

With the continuous development of industrial technology,wastewater discharged into the environment from mining,electroplating and metallurgy contain large amounts of heavy metal ions,which have a serious impact on ecosystems and biosecurity.Among them,lead（Pb）and cadmium（Cd）as typical heavy metals,Pb causes serious damage to the nervous,digestive and urinary systems,and Cd is associated with pulmonary edema,kidney dysfunction and cancer,and it is urgent to develop efficient removal technologies for Pb²⁺and Cd²⁺in the aqueous environment.In this thesis,we investigated the effects of reaction temperature,reaction time and solid content on the yield of hydrochar by using the"Hydrothermal carbonization+KHCO₃ activation"process to prepare porous high-performance adsorption carbon materials from antibiotic residue,and then characterized the solid-phase products to determine the optimal conditions for hydrochar preparation by HTC of antibiotic residue.conditions.The best-performing char materials were subjected to KHCO₃ activation experiments to investigate the effects of activation temperature,alkali-to-charcoal ratio and activation time on the yield of the modified hydrochar,and were also characterized by scanning electron microscopy,specific surface area and pore size,X-ray diffraction and Fourier infrared spectroscopy to select high-performance adsorbent char materials with high specific surface area and abundant oxygen-containing functional groups.The effects of initial p H,adsorbent dosing,initial solution solubility and adsorption time on the adsorption performance of the modified hydrochar were investigated,and the adsorption mechanism of the modified hydrochar was discussed.The main findings are as follows:（1）The relationship between the yield,elements composition,surface functional groups and pore structure of hydrochar prepared by Hydrothermal carbonization of antibiotic residues and the hydrothermal reaction temperature,reaction time and solids content was investigated.The results shows that the carbon yield decreases with increasing temperature,the species of oxygen-containing functional groups are retained but the abundance decreases,and the degree of aromatization and pore structure of the hydrochar are enhanced.（2）The"Hydrothermal carbonization+KHCO₃ activation"process is a feasible way to prepare porous high-performance adsorption carbon from antibiotic residues.The hydrochar was prepared by Hydrothermal carbonization with the raw material of Avermectin residue,and the reaction conditions as follows:the reaction temperature was maintained at 180℃for 120 min,the solid content was 6.6 wt.%,and the yield of hydrochar was 70.97%,and the specific surface area was 7.727 m²/g.The hydrochar was modified by KHCO₃ to produce porous adsorption carbon materials.The morphology of the modified hydrochar was controlled by changing the activation temperature and alkali-to-carbon ratio.Under the activation temperature of 700℃,alkali-to-carbon ratio of 4:1and activation time of 1 h,the yield of modified hydrochar was 53.33%and the specific surface area was 313.24 m²/g,which was 43.39 times of hydrochar,indicating that KHCO₃,as a green activator,could effectively promote the activation process of hydrochar.The optimal preparation conditions of Hydrothermal carbonization with a reaction of 240°C for 120 min and activation conditions with an alkali-to-charcoal ratio of 4:1 at 800°C for 1 h,using the residue of Typhimycin as the raw material.The resulting porous carbon yield was 41.33%and the specific surface area was 1111.95 m²/g,which was 3.55 times higher than the modified Avermectin residue hydrochar.In this study,a low-cost,energy-efficient and environmentally friendly green activator was proposed to provide a new way for porous high-performance adsorption carbon materials.（3）The experimental results of Pb²⁺and Cd²⁺adsorption performance with modified Typhimycin residue hydrochar showed that the adsorption amounts of Pb²⁺and Cd²⁺by Typhimycin residue hydrochar and modified Typhimycin residue hydrochar increased with the increase of p H value,adsorption time and initial concentration of heavy metals,and decreased with the increase of adsorbent dosing.The best effect of HC and KHC on heavy metal removal was achieved at p H=6,adsorption time of 180 min,adsorbent dosage of 100 mg,and initial heavy metal concentration of 100 mg/L,removal efficiencies were 99.86%,58.9%and 92.3%,45.65%,respectively.In the adsorption experiments for Pb²⁺and Cd²⁺,the adsorption patterns were in accordance with the quasi-secondary kinetic model and the Langmuir isotherm adsorption equation,indicating that the adsorption process was chemisorption-based monolayer adsorption.The maximum adsorption amounts of modified hydrochar for Pb²⁺and Cd²⁺were inferred from the isotherms as 289.35 mg/g and 186 mg/g,respectively.Characterization analysis of the modified hydrochar before and after adsorption revealed that the adsorption processes were related to those with chemisorption,complexation reaction,electrostatic attraction,ion exchange andπ-πinteractions.