Enhanced biosorptive removal of cadmium from aqueous solutions by silicon dioxide nano-powder, heat inactivated and immobilized Aspergillus ustus

Heat inactivated Aspergillus ustus (Asp), silicon dioxide-nano-powder (N―Si), and silicon dioxide nano-powder-combined-heat inactivated Aspergillus ustus (N―Si―Asp) were used to study the biosorption of Cd(II) from aqueous solutions via batch equilibrium technique. Surface characterization and immobilization of the fungal cells on silicon dioxide-nano-powder were examined and confirmed by using FT-IR and ESM analysis. Cadmium biosorption processes were investigated under the effect of pH, contact time, sorbent dosage and initial metal concentration. The three examined sorbents were found to exhibit maximum μmol g-1 capacity values in pH 7.0. The maximum determined cadmium capacity by silicon dioxide-nano-powder (N―Si) (600 μmol g− 1) was found higher than that exhibited by the heat inactivated fungal cells (Asp) (400 μmol g− 1). However, (N―Si―Asp) exhibited the highest sorption cadmium capacity (1000 μmol g− 1) as a combined behavior of both silicon dioxide nano-powder and Aspergillus ustus units. Sorption equilibria were established in 20 min and their data were well described by both Langmuir and Freundlich models. The potential applications of these sorbents for biosorptive removal of Cd(II) from real samples contaminated with cadmium, were successfully accomplished via a micro-column under constant flow rate.

Research highlights
► For the first time, Aspergillus ustus was used in biosorption process.
► Modified biosorbents was formed between Aspergillus ustus and nano-silica.
► Excellent biosorption of Cd(II) was established under various controlling factors.
► Optimization of all sorption controlling factors was studied and evaluated.
► Successful application of the novel biosorbents for biosorption from real samples.