Uptake of 2,4-dichlorophenoxyacetic acid and tetracycline in single and binary systems onto a biomass-MOF composite: adsorption and mechanism study

In this study, an adsorbent based on waste peanut husks was synthesized. To facilitate the easy removal and efficiency of these peanut husks, it was first endowed with magnetic properties via the coprecipitation method after which NH 2 -MIL-101 (Fe) was loaded onto the magnetized peanut husks. This magnetic biomass-MOF composite (MPN@NH 2 -MIL-101 (Fe)) was used for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and tetracycline (TC) in single and binary systems. MPN@NH 2 -MIL-101 (Fe) was found to be a crystalline magnetic adsorbent with a mesoporous structure with a surface area of 70.5 m 2  g −1 , pH point of zero charge of about 4.05, and possesses oxygen and nitrogen atoms containing functional groups which promoted its interactions with the studied pollutants leading to their uptake. Owing to the nature of these contaminants, the interactions that occurred in these adsorption processes were found to be dominated by both chemisorption and physisorption mechanisms. The monolayer adsorption capacity of MPN@NH 2 -MIL-101 (Fe) towards 2,4-D and TC was found to be 79.2 ± 8.3 and 109 ± 3.76 mg g −1 according to the Langmuir model, respectively. In binary systems, MPN@NH 2 -MIL-101 (Fe) had a higher selectivity towards 2,4-D which could be due to its smaller size in comparison with TC signifying the role of intraparticle diffusion. These excellent features of MPN@NH 2 -MIL-101 (Fe) coupled with its stability in aqueous solution and ease associated with its removal may enhance its prospects as an alternative adsorbent for practical applications. Graphical abstract