Renewable terpene-based highly porous polymer monoliths for the effective removal of persistent pharmaceuticals of tetracycline and ibuprofen

Abstract

Adsorptive removal of residual pharmaceuticals from wastewater has become an important issue from an environmental aspect. Macroporous polymer-based monoliths are being used as efficient adsorbents to remove such toxic materials. Regarding this, the ease of preparation, sustainability and low production cost are the most demanded properties from polymer-based monoliths. This work describes the synthesis of the first sustainable β-myrcene (My) and d-limonene (Lim) derived adsorbents by free radical copolymerization crosslinking in water-in-oil (w/o) high internal phase emulsions (HIPEs). To demonstrate the influence of purification and drying steps on the pore morphology of the monoliths, the samples were either vacuum dried (PMLE-E) or freeze-dried (PMLE-L). Characterization tests indicated that the specific surface area of the PMLE-E monolith (64.71 m2/g) was much higher than that of PMLE-L monolith (19.38 m2/g), which was attributed to the abundant pore throats. The adsorption efficiencies of the monoliths were investigated towards removal of tetracycline (TC) and ibuprofen (IBU) from aqueous solution. The effects of solution pH, contact time, and temperature on the adsorption were investigated and the experimental data fitted to isotherm, kinetic and thermodynamic models. The maximum TC and IBU adsorption capacities were found as 23.8 mg/g and 10.6 mg/g over PMLE-E adsorbent, respectively. The highest TC removal (95%) was achieved within 30 min by using PMLE-E monolith, which was ascribed to its more permeable porous structure as well as higher surface area, boosting diffusion rate of antibiotic molecules. In the reusability tests, the PMLE-E adsorbent exhibited higher performance than PMLE-L sample after eight adsorption-desorption cycles. The polymer monoliths also exhibited considerable adsorption efficiencies towards different kinds of dye molecules, demonstrating their effectiveness in the removal of water pollutants.