Experimental design and response surface modeling for optimization of Rhodamine B removal from water by magnetic nanocomposite

A magnetic nanocomposite was developed, characterized, and studied for the removal of Rhodamine B dye from aqueous solution. A four-factor central composite design (CCD) combined with response surface modeling (RSM) and optimization was employed for maximizing the dye removal by the developed nanocomposite based on 30 different experimental data obtained in a batch study. Four independent variables, viz. temperature (10–50 °C), initial pH of solution (2–10), initial dye concentration (140–220 mg/l), and adsorbent dose (1–5 g/l) were transformed to coded values and quadratic model was built to predict the responses. Analysis of variance (ANOVA) and t-test statistics were used to test the significance of the independent variables and their interactions. Adequacy of the model was tested by the correlation between experimental and predicted response and enumeration of prediction errors. Optimization of the variables for maximum adsorption of dye by the magnetic nanocomposite was performed using the quadratic model. The predicted maximum adsorption efficiency (47.44 mg/g) under the optimum conditions of the process variables (temperature 50 °C, pH 2, initial dye concentration 220 mg/l, and adsorbent dose 1 g/l) was very close to the experimental value (46.94 mg/g) determined in batch experiment. The Langmuir sorption capacity of the magnetic nanocomposite and its precursor carbon were found to be 33.8 and 4.50 mg/g, respectively (at 50 °C, pH 2, 1 g/l dose, dye concentration 140–220 mg/l), suggesting for the superiority of the developed magnetic adsorbent over its precursor carbon, and for its potential towards removal of the dyes from water/wastewater.