Engineered biochars from organic wastes for the adsorption of diclofenac, naproxen and triclosan from water systems

Abstract

Abstract The increased volume of produced toxic sewage sludge requires suitable management and utilization. Biochar production is an eco-efficient technology that uses toxic wastes towards highly efficient materials in pharmaceuticals removal from water. The management of sewage sludge towards engineered biochar can solve several problems: waste volume minimalization and obtaining of the novel highly efficient sorbents. The objective of this work was an evaluation of the affinity of sewage sludge-derived biochars towards selected pharmaceuticals in water systems. In order to achieve high specific surface area and high carbon content of biochar different carrier gas conditions, preparation temperatures and different raw materials were tested. The maximum adsorption capacity was following: diclofenac - 92.7 mg/g; triclosan - 113 mg/g and naproxen - 127 mg/g. The best fitting of the experimental results revealed mainly pseudo-second order model. The adsorption of diclofenac can occur via π-stacking interactions with the biochar surface mainly via Dubinin-Radushkevich model. Both interactions between the phenyl groups of triclosan molecules and phenol groups on biochar via hydrogen bonding, and non-covalent π-π stacking of aromatic groups of triclosan and biochar were responsible for monolayer surface coverage. The adsorption of naproxen was ascribed to Langmuir, Temkin and Dubinin-Radushkevich models and strong π–π electro-donor-acceptor interactions.