Preparation Of Municipal Sludge Biomass Carbon Composites And Their Adsorption Performance

Due to the mass production and use of tetracycline,which has seriously polluted the water environment and threatened human life health to some extent,how to treat antibiotic wastewater has become a great challenge.Antibiotic wastewater can be removed by traditional treatment methods,and currently,adsorption is widely considered as an effective measure to capture antibiotics and PAHs because of its low cost,high efficiency and simple operation.Municipal sludge is a waste product rich in organic matter and microorganisms generated from municipal wastewater treatment plants,and due to its low cost and wide distribution,it is used in different fields,especially prepared as biomass carbon for treatment in wastewater.However,due to its limited affinity for antibiotic wastewater,this paper investigates various methods to modify municipal sludge biochar based on experimental theory in an effort to improve the adsorption performance of sludge biomass char and to gain new insights into the adsorption performance and mechanism of sludge char as a new and effective adsorbent,which is studied in the following three parts.In the first part,Fe/S modified municipal sludge biomass carbon(Fe/S@BC)was prepared from municipal sludge with Fe³⁺as precursor by titrating Na₂S and Na BH₄to improve the adsorption capacity of sludge biomass carbon on TC.The adsorbent was characterized by XRD,FTIR and XPS tests,and the TC adsorption kinetics,adsorption isotherms and adsorption-adsorption thermodynamics were analyzed.The optimal conditions for TC adsorption were determined by intermittent adsorption experiments.A detailed kinetic study at 298 K,Fe/S@BC adsorption of TC reached202.56 mg/g,then showed that the adsorption process is more in line with pseudo-secondary kinetics,indicating that chemisorption and physical adsorption coexist in the process and that the adsorption limiting phase is determined by chemisorption.the Langmuir isotherm indicates that the adsorption is monolayer and the removal process is heat-absorbing.The above results suggest that municipal sludge biomass carbon can be used as an inexpensive and effective adsorbent for the removal of TC from water.In the second part,a novel KOH-Fe/Zn biochar(KOH-Fe/Zn-BC)was prepared for tetracycline removal using KOH activation and Fe/Zn modification.The chemical,morphological and structural characteristics of the biochar were characterized using FTIR,SEM-EDS,N₂adsorption isotherms and XPS.EDS images showed that comparing the elemental distribution on the surface of the material before and after adsorption,the elemental content of Si,Fe and Zn decreased,which was consistent with the results of XPS analysis that these elements interacted with TC molecules.the BET results showed that KOH-Fe/Zn-BC reached a specific surface area of 191.47m²/g.The adsorbent formed a pseudo-secondary kinetic and Langmuir isotherm adsorption process even under the interference of external ions and p H.The adsorption mechanism of KOH-Fe/Zn-BC was evaluated and attributed to the synergistic effects of electrostatic attraction,hydrogen bonding interactions,and physical and chemical adsorption.The results of the study provide a theoretical basis for the removal of tetracycline from water by municipal sludge biochar.In the third part of the study,a novel bimetallic modified sludge-based sodium alginate microsphere adsorbent was prepared by crosslinking the sludge-based sodium alginate composite with Fe/Co bimetallic solution.The effects of p H(2-11),initial TC concentration and competing cations(Na⁺,K⁺,NH₄⁺and Ca²⁺)on TC removal by BC-Fe/Co@SA were investigated.The experiments showed that BC-Fe/Co@SA exhibited good adsorption performance over a wide p H range.BC-Fe/Co@SA maximum adsorption to TC was 239.99 mg/g.The inhibition of TC removal by Ca²⁺was stronger,while the other cations were less inhibited.The mechanism of BC-Fe/Co@SA adsorption was revealed using kinetics,isotherms,thermodynamics and site energy distribution.The pseudo-secondary kinetic model suggests that the adsorption process is a combination of chemisorption and external mass transfer.In simulating the adsorption isotherm data,the Sips model was better fitted compared to the Langmuir and Freundlich models,again indicating that the adsorption process is a mixed chemical reaction process.This study demonstrates that municipal fouling peat composites are a low-cost"green"adsorbent that can effectively remove TC from the aqueous environment.