Extracellular Polymeric Substances from Penicillium expansum reduce Lead (II) and Chromium (VI) Concentrations and other Physicochemical Parameters in Tannery Wastewater

Abstract

Extracellular polymeric substances (EPS) are a collection of organic molecules from microbial metabolism, secreted outside the cell to counteract effects of harsh environment, a process that has enabled the application of the biopolymer for wastewater treatment. Reduction in concentration of lead II (Pb²⁺) and chromium VI (Cr⁶⁺) together with other physicochemical parameters from tannery wastewater by EPS from Penicillium expansum was studied. The maximum removal of Pb²⁺ and Cr⁶⁺ were 23.13% and 17.83% respectively under optimized removal conditions of 180 rpm agitation, 90 mg/L EPS concentration, 5.0 pH at  40 °C using a 2-h residence time. However, this low percentage removal of Pb²⁺ and Cr⁶⁺ in the tannery wastewater called for more batches of removal process under optimized conditions. After subjecting the EPS to four batches of removal process, 100% and 89.75% removal of Pb²⁺ and Cr⁶⁺ respectively were achieved in less than 8 h. Based on this, FTIR Analyses showed frequency shifts in alkenyl (C = C), hydroxyl (OH) and carbonyl (C = O) functional groups, and molecular overlapping in the EPS was observed on scanning electron micrograph. Physicochemical parameters in the tannery wastewater were significantly (p < 0.05) reduced by 50% or more with the exception of pH after the duration of the biosorption process. The findings in this study showed that EPS produced by P. expansum could significantly (p < 0.05) decrease the concentrations of Pb²⁺, Cr⁶⁺ and other heavy metals as well as other tannery wastewater physicochemical properties that contributed to its polluting effect.