Sulfadiazine Degradation By Ion-functionalized Biochar Activated Peroxymonosulfate

Antibiotic contamination in environmental media such as water and soil is becoming increasingly serious,seriously threatening ecological safety.The non-homogeneous catalytic oxidation technology of activating peroxymonosulfate has gained much attention in the field of treatment of refractory organic matter because of its strong oxidation capacity,good stability,wide p H tolerance range,and high interference resistance.Biochar has been widely used in the activation of peroxymonosulfate due to its large specific surface area,abundant oxygen-containing functional groups and low cost,but it has some disadvantages such as poor stability and difficult recovery.Therefore,based on the analysis of the structure of sheep manure biochar,this study prepared magnetic sheep manure biochar by co-precipitation method to improve the reusability of the activated material,and re-pyrolyzed it to prepare iron-functionalized biochar composites with multilayer structure to further improve the stability and activation ability of the composites.This study provides theoretical and technical support for the application of peroxymonosulfate activation technology in the treatment of difficult organic wastewater pollution.The main research findings are as follows:（1）The characterization results of biochar prepared from sheep manure under different pyrolysis atmospheres showed that sheep manure biochar prepared in a tube furnace had a more regular morphological structure and a larger specific surface area.The higher the pyrolysis temperature,the stronger the activation activity of the prepared biochar,which is related to its larger specific surface area,rich pore structure and aromaticity.The activation of peroxymonosulfate by sheep manure biochar（SMB）for sulfadiazine degradation is a combination of the radical pathway(SO₄^·-,·OH and O₂^·-)generated by activating peroxymonosulfate byπ-electrons on the biochar surface and the non-radical pathway（¹O₂）promoted by the C=O on the biochar.（2）The magnetic sheep manure biochar（Fe₃O₄-SMB）with different iron ion loadings was prepared from sheep manure biochar prepared by pyrolysis at 400℃ by co-precipitation method and changing the mass of iron salt in the precursor,and the results showed that too much iron ion loading would lead to blockage of the pores of the biochar by the generated Fe₃O₄,thus reducing the adsorption capacity of the activated material.Due to the loading of Fe₃O₄,Fe₃O₄-SMB is more recyclable than SMB,and Fe₃O₄-SMB has better reusability.The radical pathway(SO₄^·-,·OH and O₂^·-)by Fe₃O₄-SMB activating peroxymonosulfate and Fe induces neighboring carbon atoms to promote the non-radical pathway（¹O₂）together for the degradation of SDZ,in which the radical pathway generating SO₄^·-,·OH and O₂^·-as the dominant.（3）Fe₃O₄-SMB prepared by loading 0.8 mmol Fe ions per g of biochar was further pyrolyzed to obtain Fe functionalized sheep manure biochar（Fe@SMBs）,which not only formed a graphitized carbon layer structure,but also produced Fe⁰ and Fe₃C to further enhance the activation properties of the composites through synergistic effects.Fe@SMBs had better recoverability and stability than Fe₃O₄-SMB.In the reaction system of Fe@SMBs/peroxymonosulfate degradation of SDZ,the free radical pathway was dominated by activating peroxymonosulfate by Fe⁰ to produce SO₄^·-,and the non-free radical pathway was mainly through Fe₃C to change the carbon electron distribution to produce ¹O₂,and the graphitic carbon layer structure of Fe@SMBs provided a good electron transfer site for the non-free radical pathway.