Research On The Safe Utilization Of Pyrolysis For Antibiotics Fungus Residue And Sludge

As a big country in the production and export of antibiotic drugs,China has a large production of antibiotic fungus residue,and a large amount of sludge containing antibiotics will be produced in the treatment of antibiotic wastewater.If improperly disposed,they will cause serious ecological and environmental harm.At the same time,the environmental contamination with heavy metals occurs globally,and their presence in various water bodies has caused great harm to ecosystems and economic development.As an effective means of heavy metal removal,carbon material adsorption technology has attracted more and more attention due to its great advantages in raw material cost and environmental protection.Based on the difficult problem of waste disposal in the process of antibiotic production,this study used pyrolysis technology to transform antibiotic fungus residue and sludge into carbon-based materials.The changes in surface structure and physical and chemical properties were investigated by changing pyrolysis temperature and modification conditions,and then the adsorption performance and mechanism of metal ions in solution were analyzed.Firstly,biochar（PMD-BC）was prepared by pyrolysis of fungus residue（PMD）at400℃,600℃and 800℃respectively.The properties of PMD-BC material were analyzed by multiple characterization methods,and the potential of PMD-BC for Pb²⁺adsorption in solution was explored.With the increase of pyrolysis temperature,the ash content,carbon content,hydrophobicity and graphitization degree of PMD-BC gradually increased,while the functional groups on the surface gradually decreased,and the surface area first increased from 18.75 m²/g to 97.72 m²/g and then decreased to 55.40 m²/g.Temperature has a significant effect on the adsorption capacity of PMD-BC,and the adsorption capacities of Pb²⁺on PMD-BC400,PMD-BC600,and PMD-BC800 were37.04,62.89,and 107.53 mg/g,respectively.The adsorption process of Pb²⁺on PMD-BC can be well described by the Langmuir model and pseudo-second-order model,and mineral precipitation,ion exchange,functional group complexation and Pb²⁺-πinteraction were involved in the adsorption of Pb²⁺on PMD-BC.With increasing the pyrolysis temperature,the contributions of precipitation and Pb²⁺-πinteraction increased from 35.84%and 2.99%to 82.69%and 6.23%,while the contribution of ion exchange and complexation decreased from 48.87%and 12.29%to 10.04%and 1.04%,respectively.Mineral precipitation and ion exchange dominated Pb²⁺sorption on PMD-BC（84.71-92.73%）.Subsequently,the stabilization effect of heavy metals in antibiotic sludge pyrolysis char and its potential ecological and environmental risks were investigated to provide a theoretical and scientific basis for the safe application of sludge biochar in various fields.Considering the extensive source of sludge and the influence of sludge components on the properties of biochar,this chapter takes urban sewage sludge（mainly organic components）and antibiotic pharmaceutical sludge（mainly inorganic components）as the research object,and compared the influence of organic and inorganic components and temperature on the stability of heavy metals in sludge.The contents and morphologies of Cd,Cr,Cu,Ni,Pb and Zn during the pyrolysis of two kinds of sludge were analyzed,and the leaching of heavy metals from sludge char and the environmental risk of biochar were evaluated.After pyrolysis,the aromatization degree of biochar was significantly increased,and the concentration percentage of oxidizable state and residue state were significantly increased,while the concentration percentage of bioavailable state of heavy metals in biochar was significantly decreased.Compared with MSS and PS,the potential ecological risk index of biochar after pyrolysis at 800℃decreased by 95.51%and85.05%,respectively.The complexation reaction between heavy metals and amide functional groups（-CO-NH-）during thermal cracking is the main cause of heavy metals passivation in MSSB.In addition,the aromatic structure of MSS derived biochar providesπelectrons that have the potential to bind to heavy metals.The stability mechanism of heavy metals in PS lies in the formation of stable crystal structures with iron-containing minerals after high temperature pyrolysis,such as iron oxide of copper（Cu₆Fe₃O₇）and iron-copper phosphate（Cu₂Fe₅（PO₄）₆,Cu₃Fe₄（PO₄）₆）.The results show that pyrolysis can effectively reduce the potential ecological risk level of heavy metals in the sludge,and the components of sludge have an important influence on the stable transformation of heavy metals during the pyrolysis process,which provided a scientific basis for reducing the ecological toxicity of heavy metals and the safe disposal of sludge.Ultimately,sludge biochar（PC）prepared from antibiotic sludge pyrolysis at 400-800℃were characterized to analyze the properties of carbon materials,and the adsorption performance of PC for several heavy metals in the solution was studied.It was found that the sludge biochar（PC600）prepared at 600℃had the best adsorption effect for a variety of heavy metals,but the adsorption capacities were still low.Therefore,sludge and derived biochar were modified to improve the adsorption performance of biochar.The surface of magnetic biochar（PCMN600）modified by Na OH-KMNO₄ was coarser,and the modification process introduced ultrafine Mn Ox particles on the carbon surface.The specific surface area and pore volume of PCMN600 increased by 2.7 and 2.4times compared with PC600,and the magnetism was further enhanced.In addition,PCMN600 has larger hydrophobic surface and richer surface oxygen-containing functional groups than PC600.The results showed that the surface physicochemical properties of PCMN600 were greatly improved by KMn O₄-Na OH combined modification,and PCMN600 could be used as a promising adsorbent.Batch adsorption experiments show that the maximum adsorption capacities of PCMN600 for Pb²⁺,Cu²⁺and Cd²⁺were 181.82 mg/g,30.03 mg/g and 27.47 mg/g,respectively,at 25℃and p H5.0.Compared with PC600,the adsorption capacities increased by 6.97,4.58 and 4.29times,respectively.The adsorption processes of three toxic metal ions fitted well to the pseudo-second-order model and Langmuir isotherm,and the sorption mechanisms were identified as electrostatic attraction,ion exchange,surface complexation,cation-πinteraction and precipitation.The strong magnetic properties of the engineered biochar endowed the adsorbent with remarkable reusability,and after five cycles of recycling,PCMN600 still retained nearly 80%of its initial adsorption capacity.In conclusion,the waste antibiotic fungus residue and antibiotic sludge were prepared into biochars,and the safety of solid pyrolysis products was evaluated to provide theoretical guarantee for the feasibility of resource recovery and in-depth utilization.It can not only effectively manage and dispose of waste,but also have a good application prospect in the treatment of metals contaminated wastewater.