Split Plot Central Composite Design for Optimization of ۴-Bromophenol Adsorption from Synthetic Wastewater, using Synthesized BiFeO۳ Perovskite Material

Optimizing adsorption processes with the use of standard central composite designs (CCD) for the removal of contaminants from wastewater is becoming more popular. The use of standard CCD enables the variables under study to be randomized. However, some studies, particularly those conducted within industries, usually involve factors with some hard to change (HTC) levels and others with easy to change (ETC) levels, in which case the HTC factor cannot be totally randomized, resulting in a split-plot design. The optimum conditions for the removal of ۴-bromophenol (۴-BP) from synthetic wastewater onto BiFeO۳ were investigated in this study using split plot CCD and three adsorption factors (pH, adsorbent dosage, and shaking time) were considered. The pH was considered the HTC factor because of the duration of time, acid and/or base required to change it, whereas the adsorbent dosage and contact time were the ETC variables. Adsorbent dosage of ۰.۶۰ g, pH of ۷, and contact time of ۱۶۷ minutes were found to be the optimum adsorption conditions at desirability of ۱. The predicted and experimental adsorbed values were ۸۸.۰۲ % and ۸۷.۸۶ %, respectively, indicating that the experimental and predicted values were in good agreement. The equilibrium adsorption data was found to be best suited by the Langmuir isotherm model, yielding a monolayer adsorption capacity of ۶۵.۹۶ mg/g. Regression results, as well as qe experimental and qe calculated values, reveal that the pseudo-second-order model more closely represents the kinetics.