Study of Glutamate-Modified Cellulose Beads for Cr(III) Adsorption by Response Surface Methodology

A cellulose-based adsorbent was prepared from a cellulose-ionic liquid solution by emulsification followed by modification with glutamic acid for Cr(III) adsorption from aqueous solution. Response surface methodology (RSM) coupled with central composite design (CCD) was employed to optimize the adsorption process to ensure high adsorption efficiency. Three independent variables [initial Cr(III) concentration, pH, and adsorbent dose] were coded as x(1), x(2), and x(3) at five levels (-1.68179, -1, 0, 1, -1.68179), and a second-order polynomial regression equation was then derived to predict the responses. The standardized effects of the independent variables and their interactions were tested by preparing a Pareto chart. Analysis of variance (ANOVA) showed that a high coefficient of determination value (R-2 = 0.9959) and a satisfactory predicted second-order regression model were achieved in the study. Therefore, the optimum conditions for Cr(III) adsorption were established, and the optimum values of the selected variables were obtained by solving the quadratic regression and by analyzing the response surface contour plots. Under the optimum conditions, four sets of experimental trials for Cr(III) adsorption rate were performed, with results that were very close to the predicted values.