Isolating and Identifying Chromium-Reducing Fungus from Pistachio Shells: Investigation on Capacity of Dead and Live Fungi for Cr(VI) Removal

Hexavalent chromium represents a potent toxicant that poses significant health risks in the living environment, necessitating its reduction or removal below allowable limits before environmental discharge. This research investigates the elimination of hexavalent chromium from wastewater using three different fungal strains: Aspergillus niger NCIM۵۴۸, A. fumigatus UB۲ ۶۰˚, and A. niger isolated from a pistachio shell identified through ITS sequencing. In a brief interaction period within a mixing reactor, both strains of Aspergillus niger successfully eliminated Cr(VI) from an initial concentration of ۵۰ mg/L. The study assessed Cr(VI) removal using live and dead A. niger biomass from pistachio shells at Cr(VI) concentrations of ۵۰ to ۸۰۰ mg/L. The study examined the impact of pH, temperature, and Copper(II) and Nickel(II) on Cr(VI) removal. At ۳۰ °C and pH ۳, live biomass (۵ g dry cell/L) removed ۹۷% of Cr(VI) (up to ۴۰۰ mg/L) within ۴۸ hours. Dead biomass nearly fully removed Cr(VI) (۸۰۰ mg/L) at ۴۵ °C and pH ۲ within ۲۴ hours. Higher biomass concentrations improved removal efficiency, but Cu(II) and Ni(II) reduced it. The primary mechanism in live biomass was metabolic Cr(VI)-to-Cr(III) reduction, while dead biomass relied on redox reactions and biosorption. SEM-EDX confirmed Cr(VI) reduction and biosorption.

کلیدواژه ها:

Alive and dead biomass ، hexavalent chromium removal ، Biosorption ، Aspergillus niger