Mechanistic insight into antibiotics and endocrine disruptors removal by wood-derived biochar, functionalized biochar and biochar composite
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Today water pollution has become one of the most critical issues in many regions of the world. The presence of antibiotics and endocrine disruptors (EDCs) in the aquatic environment causes critical problems to aquatic life and eventually on human. The efficacy for removing antibiotics (such as sulfamethazine (SMT), sulfamethoxazole (SMX), sulfathiazole (STZ) and chloramphenicol (CP)) and EDCs (such as estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2), bisphenol A (BPA) and 4-tert-butylphenol (4tBP)) in traditional wastewater treatment processes is not satisfactory. However, adsorptive materials are cost effective and highly suitable for removal of different pollutants. Adsorptive materials such as biochar, functionalized biochar (fBC) and biochar composite with zero-valent-iron were prepared by the utilization of Australian abundantly grown woody biomasses (e.g. bamboo and eucalyptus wood). The materials were applied, for the first time, to remove antibiotics and EDCs, in both single and competitive modes, from water and wastewaters (e.g. synthetic wastewater, Lake Water and sewage sludge wastewater). Special focus was given to both single and competitive sorption performance based on experimental and theoretical findings. Sorption mechanism was determined based on pH profile, speciation, ionic strength, materials characteristics, temperature, thermodynamics, solution chemistry, and water matrixes. Different isotherm models such as the Langmuir isotherm model, Freundlich isotherm model, and Polani-Mane model were applied to analyse the sorption data. For competitive sorption, summarized isotherm models were proposed. Several kinetic models such as pseudo first order kinetic model, pseudo second order kinetic model, intra-particle diffusion model and Boyd model were also employed. Effects of different synthetic wastewater composition, ions and competitive solute were also studied. The findings suggested that antibiotics and EDCs sorption occurred mainly through pseudo-second order and external mass transfer diffusion processes, by forming different types of H-bonds along with π-π electron-donor–acceptor (EDA) interactions at different pH. More importantly specific direction of π-π EDA interaction was proposed based on 1ᴴ NMR spectroscopic study. fBC was regenerated and reused several times after treatment of different water. Therefore, fBC can be a potent sorbent to adsorb a wide varieties of organic contaminants from water and wastewater.
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