Mycoremediation of the Azo dye Acid Red 14 by Wickerhamomyces Anomalus: Physicochemical Characterization, Equilibrium, and Kinetics Studies

Abstract This study aimed to evaluate the potential application, and the involved mechanism in the biosorption of Acid Red14 (AR14) by the biomass of Wickerhamomyces anomalus. Kinetics and biosorption isotherms were first examined. Then, the physicochemical characterization of cells-AR14 interactions was determined using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, Fourier transforms infrared spectroscopy, zeta potential, zero-point charge, and contact angle measurements. Finally, the Plackett-Burman and the Box-Behnken designs were used respectively to identify the most influential factors on the biosorption process and their optimization. The pseudo-second-order and the intra-particle diffusion models best fit the experimental data. Furthermore, the Langmuir model was the appropriate isotherm to explain the biosorption system, suggesting the involvement of chemisorption on a monolayer of homogeneous sites. Biomass characterizations supported these theoretical predictions. A change in the transmittance of the functional groups present was noticed after AR14-biosorption, the analysis of the zeta potential confirms the presence of anionic groups, and the contact angle measurement indicates a significant variation of the electron donor and acceptor character. Hence, it can be concluded that both chemical and electrostatic interactions of AR14 onto the macromolecular structures composing the cell surface. The most influential factors on biosorption efficiency were dye and biomass concentration, and the pH of the medium. Optimal biosorption was achieved at pH 3-4, with AR14 concentrations around 50 - 75 mg L-1 and a biomass concentration at 1.25 g L-1. These results suggest that W. anomalus might be exploited as an effective, inexpensive, and environmentally friendly biosorbent.