Abstract
In the current work, we have reported a cationic surfactant-modified Ethiopian kaolin for improved adsorption of Cr(VI) from aqueous solution. The raw kaolin was modified by treating with CTAB to enhance the adsorption properties. The crystal structure and vibrational analysis of CTAB–kaolin were investigated by Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (p-XRD) techniques. The successful modification of kaolin by CTAB through intercalation and coating was investigated by XRD and FTIR. p-XRD confirms the raw kaolin obtained from Belesa, Tigo kebele is kaolinite mineral. The study has also focused on the application of kaolin–CTAB for adsorption of hexavalent chromium. The percent removal of Cr(VI) was investigated at different parameters such as pH, contact time, concentration of Cr(VI) and adsorbent dosage. CTAB–kaolin shows 99% removal of Cr(VI) at the adsorption equilibrium (time = 180 min, 100 mg CTAB–kaolin, 10 ppm/100 ml). The Langmuir and Freundlich isotherm models were used to investigate the adsorption process of chromium onto kaolin–CTAB composites. The equilibrium data obeyed Langmuir model than Freundlich, which shows that the adsorption process proceeds through monolayer adsorption and maximum adsorption capacity was found to be Qo = 22.72 mg/g. The pseudo-second-order kinetics model is found to be well fitted than Pseudo-first-order kinetics, which implies that the adsorption mechanism more favors electrostatic interaction between chromium and kaolin–CTAB composites. In conclusion, CTAB–kaolin was found to be a promising adsorbent for the efficient removal of Cr(VI) from the aqueous solution.
Highlights
During the last decades, water pollution was one of the major concerns for the sustainability of life on earth
The positive surface charge of cetyl trimethyl ammonium bromide (CTAB)–kaolin is reasonable for the electrostatic interaction between the negative charge species of hexavalent chromium (Cr2O7− and CrO4−)
The adsorption removal Cr(VI) using CTAB–kaolin was found to be strongly dependent on pH, initial Cr(VI) concentration and adsorbent dose
Summary
Water pollution was one of the major concerns for the sustainability of life on earth. Toxic effluents discharged without being treated from various industries have taken huge responsibility for the pollution of water bodies. Chromium is the subject of many types of research and has taken huge attention in the last few years (Yusuff 2019; Pakade et al 2019). Numerous technologies have been applied for the removal of Cr(VI) from aqueous solutions such as adsorption (Gupta et al 2013), reduction (Bhati et al 2019), ion exchange (Rengaraj et al 2001) and membrane processes (Zolfaghari and Kargar 2019). The adsorption process is one of the most frequently encountered techniques for the removal of Cr(VI). Adsorption on activated carbon has been widely used for the removal of a broad range of water pollutants, especially
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