Biosorptive removal of fluoride from wastewater using tea domestic waste biochar

The biochar of tea domestic waste was applied to eliminate F− from their aqueous artificial solutions and real contaminated wastewater. Pre-pyrolysis chemical activation method was used to synthesize biochar from tea domestic waste. Two modification methods were applied, acidic modification using H3PO4 (H-modified form) and basic modification using NaOH (OH-modified form). The synthesized forms of tea biochars were characterized by the determination of ash content, bulk density, Brunauer–Emmett–Teller analyses to detect the pore size, specific surface area, and pore volume, Elemental analyses to detect C, H, O, and N contents, Thermogravimetric analyses to detect the thermal behavior of biochars, and Fourier Transform Infrared analyses to detect the functional active groups of biochars. The synthesized forms of tea biochars were optimized for fluoride removal from aqueous solutions via filter bags method and applied in enhancement of the quality of wastewater from the factories of the new Borg El-Arab City, Egypt. The highest biosorption efficacy achieved was 109.18 mg F−/g biochar using the H-modified form under the optimum conditions of biochar dosage: pH: 2, 0.25 g/l, temperature: 50 °C, initial concentration of F−: 500 mg/l, exposure time: 30 min, and agitation rate: 300 rpm. The OH-modified form achieved less than half biosorption efficacy which reached 49.39 mg F−/g biochar. The existence of competitive anions in the solution had a negative influence on F− biosorption efficacy, where the impact followed the order of PO43− > SO42− > Cl− > NO3− > HCO3−. The H-modified tea biochar proved to be a promising biosorbent for industrial wastewater treatment by achieving removal efficacy ranges of 80.89–93.31% and returning all violated F− concentrations to the allowable limit. Sustainable development can be greatly supported by using domestic tea wastes in the removal of F− due to the dual disposal of waste and contaminants at the same time. The tea wastes are eco-safe and cheap biosorbent material can be utilized as a precursor for an efficacious tool for the elimination of F− from artificial solutions in addition to real wastewater.