Removal Of Copper And Tetracycline In Aquaculture Wastewater By NZⅣ And Sewage Sludge-based Biochar

Copper（Cu） and Tetracycline（TC）are typical contaminants in aquaculture wastewater,which have brought serious harm to the water supply environment and human health.Therefore,how to efficiently remove TC and copper from aquaculture wastewater is an urgent problem to be solved.Adsorption is an effective method to remove pollutants from water,and the adsorbent is the key factor to determine the removal efficiency.In this study,wastewater sludge and nano-zero-valent iron（nZⅣ）co-pyrolytic biochar were used as adsorbents to evaluate the removal performance of TC and copper by static and dynamic experiments,and the removal mechanism of TC and copper was discussed.The main results of this study are as follows:（1）The results show that when the dosage of sludge biochar is 0.5g,p H=5,the removal rate of Cu²⁺can reach 99.35%,and the adsorption capacity can reach 4.968mg/g.When the dosage of sludge biochar was 0.05g and p H=4,the TC removal rate reached 91.31%,and the adsorption capacity reached 45.65 mg/g.Sludge biochar material has obvious removal effect on Cu and TC,but the adsorption capacity of TC is greater.The higher the temperature,the easier the adsorption reaction,the greater the adsorption capacity of copper and tetracycline.（2）Kinetics,thermodynamics and isotherms were used to study the adsorption and removal process of Cu and TC.The results show that the adsorption process is more consistent with the Langmuir isotherm model,and the Temkin model can describe the isotherm adsorption process well,which indicates that the adsorption process is mainly chemisorption.The adsorption process follows a quasi-second-order kinetic model,and the fitting results of the intra-particle diffusion model and the liquid film diffusion model show that the adsorption rate is controlled by both the liquid film diffusion and the intra-particle diffusion.Thermodynamic parameters such as enthalpy and entropy are positive,and Gibbs free energy are negative,indicating that the adsorption of Cu and TC by NZⅣ sludge biochar is an endothermic reaction.（3）Before and after NZⅣ sludge biochar adsorption of Cu and TC,scanning electron microscopy,infrared spectrum,X-ray diffraction analysis,X-ray photoelectron spectrum analysis,GC-MS analysis were used.The results show that the sludge biochar has a good pore structure and the iron is successfully attached to the biochar.Zero-valent iron of sludge biochar provides electrons for the adsorption of Cu and tetracycline,and the surface complexation,hydrogen bonding and metal coordination bonding of functional groups are also involved in the adsorption process.The solution analysis by GC-MS showed that the organic matter in biochar also participated in the adsorption of Cu and TC.（4）The dynamic experiments of Cu and TC in wastewater were carried out by using NZⅣ sludge biochar.The results showed that the greater the depth of the adsorption column bed 225mm,the lower the flow rate 5m L/min and the initial influent concentration 50mg/L,the better the adsorption effect of NZⅣ sludge biochar on Cu and TC,and the adsorption capacity of copper and tetracycline were 0.659mg/g and0.753mg/g,respectively.Thomas model and Yoon model were used to fit the dynamic adsorption experimental data and analyze the penetration curve of the fixed bed reactor.The fitting correlation coefficients R² are all above 0.9,which can well predict the running condition of the adsorption column.