Comparison of four supports for adsorption of reactive dyes by immobilized Aspergillus fumigatus beads

Abstract

Four materials sodium carboxymethylcellulose (Na-CMC) sodium alginate (SA) polyvinyl alcohol (PVA) and chitosan (CTS) were prepared as supports for entrapping fungus Aspergillus fumigatus. The adsorption of synthetic dyes Reactive Brilliant Blue KNR and Reactive Brilliant Red K-2BP by these immobilized gel beads and plain gel beads was evaluated. The adsorption efficiencies of Reactive Brilliant Red K-2BP and Reactive Brilliant Blue KN-R by CTS immobilized beads were 89.1% and 93.5% in 12 h respectively. The adsorption efficiency by Na-CMC immobilized beads was slightly lower than that of mycelial pellets. But the dye culture mediums were almost completely decolorized in 48 h using the above-mentioned two immobilized beads (exceeding 95%). The adsorption efficiency by SA immobilized beads exceeded 92% in 48 h. PVA-SA immobilized beads showed the lowest adsorption efficiency which was 79.8% for Reactive Brilliant Red K-2BP and 92.5% for Reactive Brilliant Blue KN-R in 48 h. Comparing the adsorption efficiency by plain gel beads Na-CMC plain gel beads ranked next to CTS ones. SA and PVA-SA plain gel beads hardly had the ability of adsorbing dyes. Subsequently the growth of mycelia in Na-CMC and SA immobilized beads were evaluated. The biomass increased continuously in 72 h. The adsorption capacity of Reactive Brilliant Red K-2BP and Reactive Brilliant Blue KN-R by Na-CMC immobilized beads was 78.0 and 86.7 mg/g respectively. The SEM micrographs show that the surface structure of Na-CMC immobilized bead is loose and finely porous which facilitates diffusion of the dyes.