Ultrasonically enhanced photocatalytic degradation of methylene blue by Nano-CoFe2O4-immobilized<i> Saccharomyces</i><i> cerevisiae</i> yeast composite as a photo-Fenton catalyst: A central composite design study

In this study, a novel nano-CoFe2O4-immobilized Saccharomyces cerevisiae yeast nanobiocomposite (CFO-yeast) was synthesized by a physical immobilization method for ultrasonically enhanced photo-Fenton degradation of methylene blue (MB) from aqueous medium. CFO-yeast was comprehensively characterized by UV-Visible spectroscopy, FTIR, SEM, BET, pHPZC and XRD before and after immobilization that revealed pure nano-CoFe2O4 (CFO) possessed cubic spinel crystal system having 19.0 nm average crystallite size whereas after immobilization the size reduced to 14.0 nm showing the control over growth of nanoparticles by yeast immobilization. Band gaps of CFO and CFO-yeast were observed as 3.0 eV and 2.6 eV respectively. BET surface area was observed to be 39m2/g. The characterization results also affirmed successful immobilization of Saccharomyces cerevisiae yeast over nano-CoFe2O4. Central Composite Design (CCD) with four factors and 5 levels was used to design the photoFenton degradation process and Response Surface Methodology (RSM) was used to optimize MB degradation. The optimum optimized parameters (OOP) were observed as 20 mg/L of initial MB dye concentration, 0.02 g of CFO-SC dosage, 120 min of photo-irradiation time, and a pH of 4.5. The CFO-yeast nanobiocomposite displayed a remarkable 99.5 % photocatalytic activity that proves the immense potential of the treatment process in dealing with the contemporary challenges like water pollution economically and efficiently.