Acetaminophen and trimethoprim batch and fixed-bed sorption on MgO/Al2O3-modified rice husk biochar.

Pharmaceuticals' ubiquitous presence in surface and groundwater from their increased consumption and inefficient conventional wastewater treatment removal, poses a threat to flora and fauna. Pyrolyzed co-precipitated Mg/Al oxides (3:1) on rice husk biochar surfaces (MgO/Al 2 O 3 -BC700) were prepared to treat aqueous acetaminophen and trimethoprim contamination. This adsorbent, characterized for proximate and elemental compositions, crystallinity, surface area, morphology, zero-point charge and functional groups, had a higher surface area (419 m2/g) and pore volume (0.132 cm3/g) than its pristine biochar BC700 analog (surface area 182 m2/g and pore volume 0.062 cm3/g). Hybrid multiphase MgO/Al 2 O 3 -BC700 easily adsorbed aqueous acetaminophen and trimethoprim (∼8 h equilibrium) with capacities of 69.7–137.4 mg/g and 54.2–269 mg/g, respectively. It has excellent sorption efficiency at significant ionic strengths (10–50 mM KCl), with competing individual anions (Cl − , CO 3 2 − , HCO 3 − , SO 4 2 −) and cations (Ca2+, Na+, Mg2+, Al3+) and with anionic mixtures and cationic mixtures at 0.1, 1.0 and 10 mM concentrations. Column studies for both pharmaceuticals were conducted, and key sorption parameters (EBCT, column capacity, adsorbent use rate, and % saturation) were calculated. Spent MgO/Al 2 O 3 -BC700 was regenerated using optimized concentrations of EDTA, HCl, H 2 SO 4 , ethanol, and methanol. Regeneration was performed after 3-consecutive adsorption-desorption cycles. Thorough characterization and spectroscopic investigations suggested potential sorption interactions. [Display omitted] • MgO/Al 2 O 3 was dispersed onto rice husk biochar adsorbent (MgO/Al 2 O 3 -BC700). • High acetaminophen (137.4 mg/g) and trimethoprim (269 mg/g) sorption capacities achieved on MgO/Al 2 O 3 -BC700. • Both batch and column studies were performed. • Acetaminophen and trimethoprim were recovered on regenerating MgO/Al 2 O 3 -BC700 with several solutions. • Possible sorption interactions were established via spectroscopic investigations. [ABSTRACT FROM AUTHOR]