A review of the developments in adsorbents for the efficient adsorption of ibuprofen from wastewater

This paper critically evaluates the recent advancements in developing adsorbents to remove ibuprofen (IBU) from wastewater. Adsorbent characteristics, their performance in removing IBU from wastewater in batch and column studies, the adsorption kinetics, isotherms, thermodynamics, and mechanisms, adsorbent regeneration, continuous adsorption, and future challenges are included in this paper. Activated carbons, nanomaterials, metal–organic frameworks, biochar, and other adsorbents have been developed to remove IBU from wastewater. Most adsorbents were mesoporous, while some were macro- and microporous, and they contained acidic and basic functional groups. Adsorbents' surface areas range from 2.38 to 2900 m2 g−1, pore sizes from 0.0195 to 87.3 nm, and pore volumes from 0.006 to 14.48 cm3 g−1. The adsorption capacity ranged between 0.220 mg g−1 to 497.3 mg g−1, with Cu-doped Mil-101(Fe) and Albizia lebbeck seed pods activated carbon (MSAC) adsorbents achieving the highest and lowest adsorption capacities. The optimal pH of 2–8, dose of 0.012–10 g L−1, IBU concentration of 0.07–200 mg L−1, and the equilibrium time of 0.083–120 h were obtained. The pseudo-second order and Langmuir isotherm models generally fit the data, showing that IBU was adsorbed through the chemisorption process by producing a monolayer of IBU onto the adsorbent, and the thermodynamics described the adsorption of IBU as a spontaneous and endothermic or exothermic process. The IBU was adsorbed through various mechanisms such as electrostatic interactions, π–π interactions, pore filling, pore diffusion, π–π EDA interactions, hydrogen bonding, and Yoshida interactions. More focus should be put on developing highly efficient, economical, green, and regenerable adsorbents that can adsorb multiple drugs from wastewater. Mass transfer adsorption kinetics should be studied to better understand adsorption processes, and artificial intelligence technologies should be utilized in IBU removal from wastewater to anticipate the adsorption capacity of adsorbents. This review serves as a guide in enhancing the performance of adsorbents in removing pharmaceuticals from wastewater.