Competitive adsorption of Ni(II) and Cu(II) ions from aqueous solution by vermiculite-alginate composite: batch and fixed-bed column studies

The present study introduces vermiculite-Alginic composite (VMT-ALG) as a low-cost adsorbent for the uptake of Ni(II) and Cu(II). The fabricated composite was characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The different process parameters such as contact time, pH, initial heavy metal concentration, and temperature were optimized. According to the experimental data, the Freundlich adsorption model with the coefficient determination of 0.9945 and 0.9925 is the best isotherm model to describe the adsorption of Cu(II) and Ni(II) by VMT-ALG, respectively. Also, the equilibrium study confirmed the heterogeneous adsorption for Ni(II) and Cu(II). Kinetic studies indicate that intra-particle diffusion would be the significant rate-limiting step of the adsorption process. Thermodynamic studies indicated that the adsorption process was physisorption and endothermic. Research on fixed-bed column (20 cm length and 1.0 cm inner diameter) has been carried out under different volumetric flow rates (10 and 20 ml/min) and different initial concentrations of Cu(II) and Ni(II) (250, 500, and 750 mg/l). The results of column data were successfully explained using the Thomas and Yoon-Nelson models. Finally, continuous adsorption studies for Cu(II) and Ni(II) simultaneous uptake from aqueous solutions were conducted by VMT-ALG composite. The results indicated that the adsorption capacity of Cu(II) and Ni(II) both increased with an increase in the concentration of metal ions, and decreased with an increase in the flow rate.