Application of agricultural waste-derived biochar for removing ammonium, phosphate, and oxytetracycline from agricultural wastewater

Abstract

Biochars derived from agricultural residues, including corn cobs, coconut fiber, rice husk, and bagasse, have been synthesised by oxygen-limited combustion and sand incubation techniques. Following synthesis, the biochar materials were applied to remove phosphate, ammonium, and residual oxytetracycline (OTC). The materials reached the adsorption equilibrium within 10 minutes and exhibited optimal adsorption at pH 5 for PO₄^3-, pH 7 for OTC, and pH 9 for NH₄⁺. The equilibrium adsorption data fit the Langmuir adsorption isotherm model with maximum adsorption capacities ranging from 7.78 to 9.16 mg/g for NH₄⁺, 4.80 to 6.32 mg/g for PO₄^3-, and 3.04 to 4.38 mg/g for OTC. These biochars were applied to treat pollutants in local agricultural wastewater samples and exhibited adsorption capacities of 5.17-7.99 mg/g for NH₄⁺, 3.71-5.97 mg/g for PO₄^3-, and 2.14-4.14 mg/g for OTC.