Abstract
Biochar-immobilized microorganism technology is an effective way to remove antibiotic contamination in aqueous solutions. In this study, the effect and mechanism of immobilization of Bacillus subtilis by honeysuckle residue–derived biochar for the removal of chlortetracycline (CTC) were investigated using corn straw biochar as a comparison. The biochar’s structural characteristics and properties were determined using scanning electron microscopy, X-ray diffractometer, Fourier-transform infrared spectrometer, specific surface area, and pore size analyzer. It was found that honeysuckle residue–derived biochar had a well-developed pore structure, which provided adequate living space for microorganisms. The removal rate of CTC (50 mg/L) by honeysuckle residue biochar-microbial complex (HBCM) was 15.31% higher than that of corn straw biochar-microbial complex, indicating that HBCM was an excellent carrier. The mechanism of CTC removal by HBCM was a synergistic effect of biochar adsorption and microbial degradation. The removal process of HBCM material was carried out for 3 days at an optimum substrate concentration of 50 mg/L, an ambient temperature of 35 °C, a solution pH of 7, and the addition of 5 g/L complexes, achieving a removal rate of 78.35%. In addition, the complex possessed high storage stability and could be reused three times continuously and efficiently. This study provides a method for preparing an efficient biochar-microbial complex using Chinese medicine residue waste substrate, which provides a new idea for removing CTC from water.
Highlights
Antibiotics are compounds that can inhibit or eliminate microorganisms' growth and are widely used in the treatment and prevention of human and animal diseases (Kummerer 2009)
BSZ1, HBC, CSB, HBCM and CSBM were added to 50 mg/L of CTC solution, and the removal rate was used as an evaluation index
The removal rates of CTC degrading bacteria increased by 18.77% and 3.46% (HBCM and CSBM), respectively, indicating that immobilization improved the degradation performance of the microorganisms
Summary
Antibiotics are compounds that can inhibit or eliminate microorganisms' growth and are widely used in the treatment and prevention of human and animal diseases (Kummerer 2009). Biodegradation is an inexpensive and simple method that uses enzymes and other substances produced by microbial cells in their metabolic activities to degrade and remove antibiotics, and less likely to cause secondary contamination (Shao et al 2009). Biochar has a welldeveloped pore structure and specific surface area, which provides space for microbial growth and reproduction and is conducive to increasing cell density and pollutant removal rate (Xiong et al 2017; Ma et al 2020). Nguyen et al (2016) used granular activated carbon as a carrier material to immobilize laccase to remediate sulfamethoxazole (SMZ) effluent. They found that the immobilization technique improved laccase activity and increased the removal rate of sulfamethoxazole in water. Most studies have focused on removing antibiotics in water, less research has been conducted on the removal mechanisms of biochar adsorption and microbial degradation
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