Isotherm and kinetics study of Ni(II) ions adsorption from wastewater using carbon nanotubes decorated with ZnO nanoparticles

Abstract

A zinc oxide/carbon nanotube hybrid (ZnO/MWCNT) was synthesized utilizing a straightforward precipitation technique based on the physical approach of pulsed laser ablation. Various techniques were employed to investigate the composition, morphology and optical of the synthesized nanocomposite. The techniques employed were X-ray diffraction, Raman spectroscopy, transmission electron microscopy, FT-IR and thermal gravimetric analysis (TGA) to confirm the compete decoration to be applicable for removal Ni(II) ions in an aqueous solution. ZnO have a hexagonal wurtzite structure connected to hexagonal graphite of MWCNT from XRD. The interaction between ZnO and CNTs resulted in a reduction in the domain of sp2 bonds, according to Raman. From TGA, we can attribute the reduction in thermal analysis to the oxidation of surface hydroxyl functional groups (-OH), the evaporation of surface solvent and the presence of ZnO’s inorganic oxide structure compared to pristine MWCNT. These findings confirmed that adding ZnO NPs to MWCNT caused more structural flaws and surface disorder, even though the structure of the CNTs stayed the same. We then investigated numerous factors affecting the extraction of Ni(II) ions, including pH, duration of extraction, amount of nanosorbent used and circumstances. We observed the optimal conditions at room temperature, pH of 5.9, nanoadsorbent dosage of 0.2 g/L and contact time of 1 h. Atomic absorption spectrometry easily monitored the kinetics of this reaction. The Langmuir, Freundlich and Redlich–Peterson isotherm models explain the mechanism underlying the adsorption equilibrium isotherm. Furthermore, regeneration experiments revealed that the adsorbent still maintained a high adsorption capacity after six cycles, demonstrating remarkable potential for use in environmentally friendly applications.