Evaluation of adsorption capacities of nanocomposites prepared from bean starch and montmorillonite

To date, many efforts have been made in order to develop novel cost-efficient materials that can be used to remove heavy metal ions from aqueous solution. The aim of this work was to evaluate the adsorption capacity of nanocomposites prepared from starch and sodium montmorillonite (starch/Na-MMT). To this end, nanocomposites with different starch-to-nanoclay ratio (SN) of 5:1, 10:1 and 10:3 were prepared by intercalation technique in acetic acid solution and used for nickel and cobalt uptake. The characterization techniques of Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) were conducted to determine physicochemical and morphological properties of nanocomposites as well as bean starch. The initial concentration of metal ions, pH and SN ratios were varied to assess how well the starch/Na-MMT nanocomposites could remove cobalt and nickel from aqueous solutions. Experimental results were used to calculate parameters of the Langmuir and Freundlich isotherms. It was found that pH = 4.5, C-o = 100 ppm (metal concentration in solution), and SN = 10:1 were the most suitable conditions based on the removal yield (97.1%) and adsorptive favourability for nickel ions. For cobalt, the highest removal yield (78.07%) was achieved using pH = 6, C-o = 140 ppm and SN = 10:3. The fitting of the data to the Langmuir and Freundlich isotherms indicated a multilayer adsorption process for both heavy metals. These results showed that the nanocomposite starch/Na-MMT exhibited attractive adsorption properties for its application during wastewater remediation. The incorporation of Na-MMT in the bean starch matrix is strongly encouraged for nickel uptake due to the adsorption efficiencies increase by 35% compared to the unmodified starch.