Sustainable removal of aqueous naproxen using a ternary magneto-biochar-clay composite : competition with carbamazepine and influence of dissolved organic matter

Abstract

Low-cost magneto-biochar-clay (MBC) composite adsorbent prepared by a combination of synthesized Fe3O4, biochar (from grape cluster stalk), and feldspar clay was tested for naproxen removal from simulated and real contaminated aqueous solutions. Preliminary sorption results for naproxen and other contaminants showed higher removal efficiency of the MBC than the pristine materials. Naproxen adsorption optimum solid-liquid ratio was at 0.5 g/L and the adsorption equilibrium was attained in 720 min on this composite, while the optimum adsorption was achieved at solution pH of 2.5. The process was endothermic and better described by the Sips adsorption isotherm model. Adsorptive pore filling, electrostatic and hydrophobic interactions between the composite surfaces and the naproxen species were the main mechanisms of naproxen uptake. In a competitive adsorption study with carbamazepine, the two compounds showed higher competition at lower solution pH values. With increase in dissolved organic matter concentration in water, naproxen and carbamazepine sorption reduced significantly. The composite retained high removal efficiency (≥99 %) after five consecutive adsorption cycles. Naproxen removal efficiency in real environmental water (river water) containing low naproxen concentration (50 μg/L) was quite high (≈ 93 %). Based on this study, the composite is sustainable, cost-efficient, and potentially applicable for naproxen and carbamazepine removal from surface waters.