Bioscorodite Production from As(III) and Fe(II) Salts under Oxidizing and Acidic Conditions of Trichoderma atroviride Culture

Abstract

Arsenic (As) contamination of groundwater is widespread and significantly affects drinking water, posing a threat to public health due to its classification as a human carcinogen. Arsenic (As) can be removed from contaminated water using sustainable technologies (e.g., biotechnological processes). The process of removing Arsenic from water through reactions with iron under acidic and oxidizing conditions in a fungal broth has been proposed alongside the production of bioscorodite (FeAsO4·2H2O) crystals by Trichoderma atroviride culture. This ascomycete was selected based on tests with three other fungi (Aspergillus niger, and the basidiomycetes, Postia placenta, and Phanerochaete chrysosporium) because it decreased the pH to 2.2, raised the redox potential (Eh) to 207 mV, and was the quickest to produce 0.39 µg/L of H2O2 in a modified Wunder medium. The Eh was further increased to 324.80 mV under improved fungal culture conditions, selected using a 23−1 fractional factorial design (FFD). The fungal broth was then used for bioscorodite production by adding Fe(III)/As(III) salts and scorodite seeds at 92 °C for 21 h. Scorodite seeds and bioscorodite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Arsenic was determined in solution by atomic absorption spectrophotometry (AAS), and a 73% reduction in the initial As concentration (0.30 g/100 mL) was observed after bioscorodite production. Bioscorodite production under appropriate fungal culture conditions could be an option for sustainable As removal from water. The production of H2O2 by the fungus resulted in the oxidation of As(III) into As(V) and acidification of the culture broth, which created the necessary conditions for the production of bioscorodite without the need for chemical acids or oxidants. This approach is environmentally friendly and cost effective, making it a promising alternative for the treatment of arsenic-contaminated water.