Optimization of Ni(II) & Co(II) removal from wastewater and statistical studies on the results of experimental designs

In this study, mono-dispersed carboxymethyl chitosan (CCS)-bounded Fe ₃ O ₄ (OCMCS/Fe ₃ O ₄ ) nanoparticles were used as a novel magnetic nano-adsorbent for the removal of Ni(II) and Co(II) ions from wastewater. Chitosan (CS) was first carboxymethylated and then covalently bounded on the surface of Fe ₃ O ₄ nanoparticles. The micrographs of the scanning electron microscopy analysis showed that the nanoparticles were mono-dispersed and had spherical morphology with mean diameter of 33 nm. X-ray diffraction patterns indicated that the magnetic nanoparticles were pure Fe ₃ O ₄ with a spinel structure, and the binding of O-CCS did not change the phase of Fe ₃ O ₄ . In this study, the most significant factors affecting adsorption process, i.e., pH, adsorbent dosage, contact time and concentration of Ni(II) and Co(II) ions were studied. Box–Behnken design and analysis of variance were used to determine the main effects and their interactions. The optimization study revealed that pH, adsorbent dosage and metal concentration had a significant effect on metal removal. In addition, results indicated that contact time parameter had no significant effect on the removal of Ni(II) and Co(II) ions (p-value > 0.01).