Effects of co-substrate and biomass acclimation concentration on the bioregeneration of azo dye-loaded mono-amine modified silica.

Bioregeneration of mono-amine modified silica gel (MAMS) adsorbent loaded with Acid Orange 7 (AO7), Acid Yellow 9 (AY9) and Acid Red 14 (AR14), respectively, was investigated under two different operational conditions, namely absence/presence of sucrose/bacto-peptone as the co-substrate and different biomass acclimation concentrations. The results revealed that the AY9- and AR14-loaded MAMS adsorbents could almost be completely bioregenerated but only in the presence of co-substrate whereas the bioregeneration of AO7-loaded MAMS could achieve up to 71% in the absence of the co-substrate. These differences could be related to the structural properties of the investigated azo dyes. In addition, the results showed that the bioregeneration duration of AO7-loaded MAMS could be progressively shortened by using biomass acclimated to increasingly higher AO7 concentration. However, the bioregeneration efficiencies were found to be relatively unchanged under different biomass acclimation concentrations.

Effect of structural properties of acid dyes on their adsorption behaviour from aqueous solutions by amine modified silica.

Monoamine modified silica particles (MAMS) were prepared and characterized by infrared (FT-IR) and thermogravimetric analysis (TGA). The modified silica particles were used for removal of acid orange 10 (AO-10) and acid orange 12 (AO-12) from their aqueous solutions. The adsorption behaviour of the two dyes was studied at different experimental conditions of pH, contact time, concentration of dye, temperature and salt solution. The adsorption of AO-10 followed pseudo-first order kinetics whereas AO-12 followed pseudo-second order. The two dyes showed different modes of interaction with silica surface. Desorption of the loaded dyes was carried out at pH 10 and found to be 10.4 and 91.6% for AO-12 and AO-10, respectively.