Application of Non-Noble Metal and Cellulose Nanocrystals Modified Date Pits as Novel Adsorbents for Groundwater Treatment

Abstract

This work was designed to investigate the potential of eliminating lithium (Li) and molybdenum (Mo) ions from groundwater through adsorption. A novel adsorbent was prepared by using agricultural waste, namely date pits. The date pits were modified with non-noble metal oxide/cellulose nanocrystal (CNC) composites namely copper oxide (CuO/CNC@DP), cobalt oxide (CoO/CNC@DP), and manganese oxide (MnO2/CNC@DP). The obtained results revealed that (MnO2/CNC@DP) exhibited more preferable characteristics than (CuO/CNC@DP) and (CoO/CNC@DP). Therefore, the adsorption process parameters such as pH values, temperature, and initial concentration of Li and Mo were assessed via (MnO2/CNC@DP) using synthetic solutions and real groundwater samples. At the optimum pH of 2, the removal efficiency for Li and Mo was 25.18% and 47.53%, respectively. The adsorption capacity increases with increasing the initial concentration of Li and Mo, which were 15.5 mg/g and 30.0 mg/g, respectively. The thermodynamics of adsorption was studied, and it is found that the adsorption is spontaneous and endothermic. Moreover, the adsorption isotherm models ( Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich) were calculated, and found that the best isotherm model fit with the experimental data was Langmuir. The physicochemical properties of the prepared v

adsorbents were examined by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM) techniques, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), Energy Dispersive X-Ray Spectroscopy (EDX) and zeta potential. The desorption experiment indicated that Li and Mo can be desorbed from the (MnO2/CNC@DP) surface by using 1.0M HCl. The removal of Li and Mo from real groundwater was 88.42% and 47.2%, respectively. The proposed mechanisms for the adsorption of Li and Mo by (MnO2/CNC@DP) were dominated by chemisorption, intra-particle diffusion and pore filling, inner-sphere complexation, and electrostatic attraction. The results indicated that (MnO2/CNC@DP) is stable and inexpensive. As a result of the research, (MnO2/CNC@DP) appears to be a promising adsorbent with a high potential for removing Li and Mo from contaminated water.