Cd (II) Removal from Aqueous Solutions by Adsorption on Henna and Henna with Chitosan Microparticles Using Response Surface Methodology

In this research, the capabilities of Henna and Henna with chitosan microparticles adsorbents were studied in order to remove the ion Cd (II). Response Surface Method (RSM) and Central Composite Design (CCD) were used to minimize the number of experiments (21 runs) for Henna and (26 runs) for the Henna with chitosan microparticles. The parameters were pH (2-9), initial solution concentration [10-100 mg/L (ppm)], adsorbent dosage (0.1-1 g) and process time (20-150 min). It was concluded that Cd (II) removal increased from 13.78% to 70.06% with increasing the pH from 2 to 9 (maximum adsorption was at pH 9) for Henna and 82.81% to 97.60% for the Henna with chitosan microparticles. The Cd (II) removal was decreased from 78.73% to 40.44% for Henna and 96.47% to 90.37% for the Henna with chitosan microparticles with increasing the initial solution concentration (from 10 to 100 ppm). Furthermore, the Cd (II) removal was increased from 37.5% to 64.59% for Henna and from 86.74% to 97.76 % for the Henna with chitosan microparticles with the adsorbent dosage increment (from 0.1 to 1 g). The error for the optimum point between the statistical data and experimental ones were at 1.53% for Henna and at 1.61% for the Henna with chitosan microparticles. The Langmuir and Freundlich isotherm models were applied as the adsorption mechanism. Two correlations (with R2</sup>=0.9750 for Henna and R2</sup>=0.8538 for the Henna with chitosan microparticles) between the Langmuir model and experimental data were investigated‍ although Freundlich model showed the better agreements between the theoretical data and experimental ones (R2</sup>=0.9949 for Henna and R2</sup>=0.9955 for the Henna with chitosan microparticles). It also showed that the Henna with chitosan microparticles is a fantastic adsorbent for Cd (II) removal.