Abstract:
Industrial wastewater caused water pollution by trace heavy metals is a concerning issue worldwide. Developing eco-friendly remediation techniques for removing these toxic metals, such as employing nanomaterials as adsorbents, is crucial to mitigate heavy metals caused human and ecological effects. In this study, Ni-CdO NCs were synthesized using Artemisia afra leaf crude extract to remove hexavalent chromium (Cr (VI)) from electroplating wastewater. The synthesized nanomaterials were characterized using FT-IR, SEM, ZP, XRD, and UV-Vis analytical instruments. Batch adsorption studies were employed to assess the effects of various parameters such as contact time, pH, adsorbent dose, temperature, and initial Cr (VI) concentration on the adsorption of Cr (VI) by Ni-CdO NCs. The optimum conditions identified were an adsorbent dose of 0.15 g/100 mL, a pH of 2 (-), an initial Cr (VI) concentration of 5 mg/L, a treatment temperature of 25 °C, and a contact time of 15 minutes. The Cr (VI) removal results indicated that Ni-CdO NCs achieved a removal efficiency of 96.87 ± 0.12%, which was greater than the efficiency observed for CdO NPs (93.5 ± 0.78%). The adsorption capacity of Ni-CdO NCs was determined to be 22.91 mg/g based on the Langmuir adsorption isotherm model. The highest removal of Cr (VI) by Ni-CdO NCs confirmed following the Langmuir adsorption isotherm model (R2 = 0.996) and second-order kinetics model (R2 = 0.995), with separation parameter (RL) values of < 1.0 indicating that adsorption of Cr (VI) on Ni-CdO is favored. This preference may be attributed to lower band energy (3.27 eV), enhanced surface area, and semiconducting nature resulting from synergism as compared to CdO NPs (3.4 eV). Additionally, the recyclability study also revealed that the produced nanocomposite efficiently removes the target analyte up to five cycles. This study indicated that Ni-CdO NCs is a potential adsorbent for the removal of hexavalent chromium from industrial wastewater. The produced eco-friendly and low-cost nanomaterial may also have the potential to extend its application for micro-organic pollutants, including pesticides from agricultural wastewater
