Document Type : Research Article
Department of Chemistry, Ahmadu Bello University Zaria, Nigeria
AHMADU BELLO UNIVERSITY, FACULTY OF SCIENCES, DEPARTMENT OF CHEMISTRY, KADUNA ZARIA, NIGERIA
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 4-bromophenol (4-BP) from synthetic wastewater onto BiFeO3 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 0.60 g, pH of 7, and contact time of 167 minutes were found to be the optimum adsorption conditions at desirability of 1. The predicted and experimental adsorbed values were 88.02 % and 87.86 %, 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 65.96 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.