Biosorption of hexacyanoferrate(III) complex anion to dead biomass of the basidiomycete Pleurotus mutilus: Biosorbent characterization and batch experiments

This work is a contribution to the use of natural, cost-effective biosorbants in industrial wastewater treatment processes, addressing more particularly to the effluents resulting from surface treatment and mining industries. A dead fungal biomass (i.e., Pleurotus mutilus) collected as a waste from an antibiotic production plant was tested as a biosorbent for iron(III)–cyanide complex ions. A physicochemical characterization of this biomass was followed by batch biosorption experiments. Potentiometric titration confirmed by FTIR analysis indicated a variety of functionalities on the biomass surface, primarily carboxylic and amine groups which conferred to the biosorbent a positive charge in acid medium and a negative charge in alkaline medium. Biomass pre-treatment with acetic acid slightly improved its biosorption efficiency which was also affected by the initial pH of the test solution, the size and concentration of biosorbent particles, and the stirring speed of the particle suspension. In particular, the best performance was obtained at strongly alkaline pH (around 12) even though the overall electrical charge of the biomass was negative in this pH range. The sorption kinetics obeyed both pseudo-first-order and pseudo-second-order models and intraparticle diffusion was the main limiting step in the biosorption kinetics. Applying the Langmuir isotherm modelling, the highest biosorption efficiency, i.e., the maximum solid phase concentration of complex ions (forming a complete monolayer coverage on the sorbent surface) was over 620 mg g−1. Continuous fixed-bed sorption–desorption experiments are in progress to confirm these promising results.