Adsorptive removal of diethyl phthalate (DEP) from water using grape fruit peel waste derived adsorbents

Abstract Crop production is often accompanied by the generation of wastes whose management often becomes a critical environmental issue in some parts of the world due to lack of proper recycling technologies. Agricultural wastes could be used sustainably to synthesize low cost adsorbents for the removal of contaminants in water. In this study grapefruit peel (GFP) waste was used to synthesize carbonaceous adsorbents for use in the removal of diethyl phthalate (DEP) from water. Three adsorbents were prepared in a muffle furnace at low temperature (400, 500 and 600 °C) and 4-hour residence time. The production yields ranged between 27 and 38% and the adsorbents were characterised by alkaline pH (> 9), high ash content (30.09–42.13%) and low surface area (9–13 m 2 g − 1 ). At optimal experimental conditions DEP maximal adsorption capacity was 23.8, 24.1, 24.2 mg g − 1 for the adsorbents prepared at 400, 500 and 600 °C respectively. Evidently there were no significant differences in the adsorption capacity for adsorbents prepared at different temperatures. DEP adsorption capacity was optimal at acidic pH (4–6). The adsorption kinetics followed the pseudo first order model (R adj 2 = 0.99) whilst the isotherms were governed by the Langmuir model (R adj 2 = 0.99) for adsorbents prepared at 400 and 500 °C and Freundlich model for adsorbents prepared at 600 °C. The adsorption capacities reported in this study are comparable to those previously reported in literature thus positioning GFP as a competitive material for the synthesis of adsorptive materials for sustainable removal of plasticizers from the environment. Nonetheless further work is necessary to determine the adsorption mechanisms as well as adsorbent stability and reusability.