| Abstrakt: |
The objective of this study consists to investigate an efficient, and green pathway of multi-metals Cd (II), Cr (VI), and As (III) recovery from aqueous solutions by adsorption process using natural sedimentary rock (NSR) in the batch mode. This adsorbent was characterized before and after the adsorption process by several techniques i.e., X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FTIR), Time-of-Flight Secondary Ion Mass Spectrometry (ToF–SIMS), Scanning Electron Microscopy with Energy-Dispersive X-ray spectroscopy (SEM/EDX), Atomic Force Microscopy (AFM), and Cation Exchange Capacity (CEC). The competitive removal process was undertaken to evaluate the effect of adsorbent mass, contact time, initial concentration, solution pH, and temperature. The kinetic data were analyzed using the linear and nonlinear forms of pseudo-first-order and pseudo-second-order kinetic models. According to the modeling of the experimental results, the adsorption kinetics was adapted to the linear pseudo-second-order model. The adsorption isotherm was evaluated by the linear and nonlinear forms of Langmuir and Freundlich isotherm models. The experimental isotherm data were better fitted with the linear Langmuir model rather than the Freundlich isotherm model. The maximum experimental adsorption capacities (Qmax) predicted by the Langmuir model were 16.75 mg g−1for Cr (VI), 21.45 mg g−1for As (III), and 12.63 mg g−1for Cd (II). The values of thermodynamic parameters revealed that the multi-metals removal of Cd (II), Cr (VI), and As (III) onto NSR was exothermic, favorable, and spontaneous in nature. Based on the results, this untreated rock can be used as an inexpensive adsorbent to treat water contaminated by heavy metals in the multi-metals system. |
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