Box-Behnken design approach for optimizing removal of copper from wastewater using a novel and green adsorbent

The aim of the present research was to apply the Box-Behnken experimental design and response surface methodology for modeling of copper (Cu2+) ions from an industrial wastewater and leachate pretreated astragalus herbal plant. A three factor, three level Box-Behnken experimental design combined with response surface modeling (RSM) and quadratic programming (QP) was employed for maximizing Cu(ID removal from aqueous solution based on 17 different experimental data obtained in a batch experimental study. Three independent variables (pH ranging from 2.0 to 8.0, contact time from 10 to 180 minutes, and adsorbent amount from 0.1 to 1 g) were studied. The significance of the independent variables and their interactions were tested by means of the analysis of variance (ANOVA) with 95% confidence limits. The standardized effects of the independent variables and their interactions on the dependent variable were also investigated by preparing a Pareto chart. The optimum values of the selected variables were obtained by solving the quadratic regression model as well as by analyzing the response surface contour plots. Using the experimental conditions of pH = 5.0, contact time = 92.5 minutes, adsorbent dosage = 0.25 g, the recovery efficiency of Cu(II) was found to be 100%. Copper-free and copperloaded astragalus was analyzed using fourier transform infrared spectrometry (FTIR) which evidenced the functional groups involved in copper uptake. Adsorption equilibrium for copper was described by using the Freundlich and Langmiur adsorption isotherms. This adsorbent was applied to different industrial wastewater and leachate samples for copper removal.