Pharmaceutically active compounds like diclofenac (DFS), ibuprofen (IBP), and other drugs that persist in the environment are listed as emerging contaminants. These escape from normal wastewater treatment plants and find their way to water streams; therefore, alternate treatment processes are needed. Herein, a sorbent material is reported that is prepared through hydrotermal carbonization from dried fruit powder of Zizipus mauritiana L. (HTC-ZM) and applied for simultaneous removal of DFS and IBP. Carbonized material (HTC-ZM) was found as agglomerates of approximately 1 μm particle size with surface area of 1160 m2/g having oxygen functional groups (e.g., COO, O, C=O) on surface. Simultaneous removal of IBP and DFS onto HTC-ZM was studied using response surface methodology with a set of 18 experiments using factors such as pH, amount of sorbent, contact time, and sorbate concentration. Maximum removal efficiency was obtained 88% and 97% for DFS and for IBP, respectively, with adsorption capacity of 2.03 mmol g-1 for DFS and 2.54 mmol g-1 for IBP. Kinetics modeling and "mean free energy" values predicted that sorption is mainly governed by physical interactions followed by "pore filling" mechanism for uptake of DFS and IBP.
Keywords: Central composite design; Hydrochar; Hydrotermal carbonization; Removal of diclofenac; Removal of ibuprofen; Ziziphus mauritiana L..