Optimization of phenol adsorption from synthetic wastewater by synthesized BiFeO3 perovskite material, using split-plot central composite design

Abstract

BackgroundOptimization of adsorption processes using statistical methods of experiment for the removal of pollutants from wastewater, in an effort to curb the global problem of water pollution, is increasingly being adopted because it is cost-effective and time-saving. In most cases, standard central composite designs (CCDs) are often employed for the optimization processes, where the experimental variables are often randomized completely. However, most experiments especially within the industries often involve factors with some hard-to-change (HTC) levels and some with easy-to-change (ETC) levels, in which case the HTC factor cannot be completely randomized, and this challenge can only be overcome by the use of a split-plot CCD. However, there is scarcity of literature on the use of split-plot CCD for the optimization of adsorption processes, and hence in this study, the prime conditions for the removal of phenol onto BiFeO3 from synthetic wastewater were studied. The effect of three adsorption variables (pH, adsorbent dosage, and shaking time) was investigated using split-plot CCD. pH was considered as the HTC factor due to the amount of time, acid and/or base required to change it, while the adsorbent dosage and contact time were the ETC factors. Quadratic model was developed for the phenol percentage removal.ResultsThe optimum adsorption conditions obtained from the study were adsorbent dosage of 0.60 g, pH of 7 as well as contact time of 167 min with desirability of 1. The predicted and experimental values obtained were 89.73 and 89.21%, showing good agreement between the experimental value and those predicted by the quadratic model. Langmuir isotherm model was found to be the best fit for the equilibrium adsorption data giving rise to monolayer adsorption capacity of 106.50 mg/g. The pseudo-second-order kinetic model’s correlation coefficient (R2) was higher than that of the pseudo-second-order kinetic suggesting the applicability of the model to the adsorption of phenol.ConclusionsThe synthesized BiFeO3 could be considered as a viable alternative to the expensive commercial activated carbon for the removal of phenols in wastewater, and the use of split-plot CCD model makes the experiment much easier to run and save time and/or cost due to fewer number of runs and restriction in the randomization of HTC factors.