Indium removal by Aspergillus niger fungal pellets in the presence of selenite and tellurite

Abstract

The feasibility of simultaneous removal of indium, selenite and tellurite using biological reduction by Aspergillus niger fungal pellets is explored. Initially, batch experiments were conducted to study the capability of A. niger pellets to remove indium, selenium and tellurium in different combinations. The indium removal efficiency ranged between 52.3 and 65.6 % at 10 mg/L, with a maximum removal (~65 %) in incubations with only indium or indium with tellurite. The tellurium removal efficiency was maximum (76.7 %) in experiments with indium, but dropped drastically to 47.2 and 33.7 %, respectively, when selenite and indium were incubated together. The selenite removal efficiencies of the A. niger pellets were more consistent (50.2–59.5 %) for different experimental combinations and were not affected by either indium or tellurium. Further characterization of fungal biomass showed accumulation of mainly elemental Se and Te nanoparticles within the pellets. In addition, XRD analysis showed the formation of indium selenide and indium telluride during their simultaneous removal. The EPS production by A. niger increased in the presence of these elements along with changes in the polysaccharide and protein content of the EPS. The fluorescence EEM spectra revealed that the EPS produced by A. niger during pollutant removal was mostly composed of soluble microbial products and humic acid like substances. This study demonstrated recovery of elemental chalcogen and indium chalcogenide nanoparticles can be achieved using fungal pelleted systems.