Adsorption of antibiotics from water by using Chinese herbal medicine residues derived biochar: Preparation and properties studies

The residue of Chinese Herbs has been increasing at a rapid rate with the development of Traditional Chinese Medicine. As the residue become solid waste, serious second pollution can result to waters and soil. In the meanwhile, substance abuse had led to an antibiotic's accumulation in aquatic ecological environment. In this study, a residue from a Chinese herbal medicine, Flueggea suffruticosa, was used to prepare biochar for antibiotics pollution control. The biochar was modified by zinc chloride (Zn-BC) and used as an adsorbent to remove tetracyclines (TCs) from water. The surface area of Zn-BC was 1556 m2/g, and tetracycline (TC), chlortetracycline (CTC), and oxytetracycline (OTC) were chosen as target pollutants to detect the adsorptive capacity of Zn-BC. The adsorption process can be described by the pseudo-second-order model and Langmuir model, and the influences of pH and ionic strength on adsorption were also investigated. According to the Langmuir model, the maximum adsorption capacity of Zn-BC to CTC, TC and OTC was 200.0, 188.7 and 129.9 mg/g. Hydrogen bonding and electrostatic interaction played dominant roles in the adsorption process and the adsorption process was spontaneous. The biochar derived from the Chinese herbal medicine residue is an effective adsorbent for removing TCs from wastewater.