Research On The Efficiencies And Mechanisms Of Antibiotic Residues And Sludge Pyrolysis For Resource Utilization

The production of antibiotics generates a large amount of antibiotic residues and resistance genes in the antibiotic residues,wastewater and sludge from the wastewater treatment process,of which the annual production of antibiotic residues alone exceeds2 million tons in China,and improper treatment and disposal can cause serious ecological and environmental hazards.In this paper,we studied the pyrolysis characteristics and pyrolysis kinetics of antibiotic residues and sludge,investigated the release characteristics of gaseous products and nitrogen conversion during the pyrolysis of residues and sludge,and explored the mechanism of harmlessness of antibiotics and resistance genes in the process of pyrolysis;by using biochar generated from the pyrolysis of antibiotic residues and sludge as adsorbent,we studied the effectiveness of antibiotic residues and sludge-based In order to improve the application value of residues-based biochar,the adsorption performance of magnetic biochar prepared by iron activation on pollutants in water was investigated.Firstly,the pyrolysis of antibiotic residue and sludge was investigated,and it was found that the high organic matter content of antibiotic residue(AR)had good pyrolysis performance,and its pyrolysis mainly occurred in the temperature range of50-550°C;the high inorganic matter content of sludge(AS)had poor pyrolysis performance,and its pyrolysis mainly occurred in the temperature range of 50-450°C and 650-850°C;the main gaseous products of sludge pyrolysis were monocyclic aromatic hydrocarbons,alcohols and nitrogenous organic matter,etc.,while monocyclic aromatic hydrocarbons and nitrogenous organic matter are the main gaseous products of sludge pyrolysis.A study of nitrogen in antibiotic residues and sludge revealed that the nitrogen in antibiotic residues was mainly protein nitrogen,nitrile nitrogen and pyridine nitrogen.The nitrogen in antibiotic residues was mainly pyrrole nitrogen,nitrile nitrogen,protein nitrogen,pyridine nitrogen and quaternary nitrogen,and the nitrogen content of biochar produced by pyrolysis of both decreased with the increase of pyrolysis temperature.When the temperature was higher than600°C,the nitrogenous organic matter in both the antibiotic residues and sludge-based biochar was dominated by pyridine nitrogen and pyrrole nitrogen.Detection of resistance genes in the antibiotic residues and sludge and the biochar produced by their pyrolysis revealed that both the residue and sludge contained a variety of?-lactam resistance genes,with 23 resistance genes detected in the residue and 36 in the sludge.After pyrolysis at 600°C and 800°C,all?-lactam resistance genes were destroyed in both.The pyrolysis of penicillin V occurred mainly below 300°C and was almost complete at 500°C.Pyrolysis temperatures above 600°C ensure that the biochar produced from the penicillin fermentation residue or sludge pyrolysis is free of penicillin residues and resistance genes.It is found that the antibiotic based biochar prepared by 800°C pyrolysis(ARB8)and sludge based biochar prepared by pyrolysis at 600°C(ASB6)have better adsorption effect on penicillin with low concentration in water.The adsorption of penicillin V on ARB8 was in accordance with the pseudo primary kinetic model and could be better described by the Langmuir adsorption isotherm model,with the equilibrium adsorption capacity of 5.89 mg/g,while the adsorption of penicillin V on ASB6 was more in accordance with the pseudo primary kinetic and intraparticle diffusion model,with the equilibrium adsorption capacity of 10.73 mg/g.The adsorption of penicillin V on ARB8 is mainly due to the weak interaction between the penicillin V molecule and the aromatic ring on ARB8.The binding sites on the penicillin V molecule are mainly the aromatic ring and H.The active adsorption sites on ARB8 are mainly the aromatic ring and its marginal functional groups,and the adsorption of penicillin V on ASB6 is mainly due to the strong interaction between the penicillin V molecule and Fe₃O₄.The binding sites on the penicillin V molecule are mainly C=O and COO-,and the active sites on the surface of ASB6 are mainly Fe on the surface of Fe₃O₄.For the removal of glyphosate from water,the antibiotic residue-based biochar(ARB6)prepared by pyrolysis at 600°C and the sludge-based biochar(ASB8)prepared by pyrolysis at 800°C were more effective.the adsorption processes of both ARB6 and ASB8 on glyphosate were in accordance with the pseudo-secondary kinetic model;the adsorption of ARB6 on glyphosate was in accordance with the Freundlich adsorption isotherm model,while the adsorption of ASB8 on The adsorption of glyphosate by ARB6 was consistent with the Freundlich adsorption isotherm model,while the adsorption of glyphosate by ASB8 could be better described by the Langmuir adsorption isotherm model.The magnetic biochar(MC_HCl and MC_HAc)with high specific surface area,good magnetic separation performance and surface nanostructure were prepared by pyrolysis,K₂FeO₄ activation and acid washing of the antibiotic residue.The adsorption of MC_HCl on penicillin V was consistent with the pseudo-primary kinetic model.The adsorption of MC_HAc on penicillin V was consistent with both pseudo-primary and pseudo-secondary kinetic models.Also,the intraparticle diffusion model can well describe the adsorption of penicillin V by both adsorbents.The adsorption of glyphosate was consistent with the pseudo-secondary kinetic model.The adsorption of penicillin V and glyphosate on both magnetic biochars conformed to the Langmuir adsorption isotherm model,and the adsorption was a spontaneous process of heat absorption,and both were entropy increasing processes.The maximum adsorption capacities of penicillin V on MC_HCl and MC_HAc were 196.08mg/g and 322.58 mg/g at 308K,respectively,while the maximum adsorption capacities of glyphosate on MC_HCl and MC_HAc were 23.42 mg/g and 79.37 mg/g at318K,respectively.MC_HAc has better adsorption effect on two pollutants in water than MC_HCl.The adsorption amount of MC_HCl decreased slightly before and after regeneration,and the regeneration performance was good;the adsorption amount of MC_HAc decreased rapidly before and after regeneration,but the adsorption performance was still better than that of MC_HCl after five regenerations.This study proposes a technical route for the safe treatment and disposal of antibiotic residues and sludge pyrolysis and safe resource utilization,which provides a theoretical basis and scientific basis for the in-situ utilization of antibiotic residues and sludge for energy and materialization.