The Indigo Blue Dye Decolorization Potential of Immobilized Scenedesmus quadricauda

Abstract

In this study, Scenedesmus quadricauda ABU12 was immobilized with sodium alginate to determine its potential for decolorizing indigo blue dye under different incubation conditions. The microalga was incubated at different pH (6.5–9.5), biomass concentrations (0.1–1.0 g l−1), dye concentrations (12–75 mg l−1) and temperatures (25–40°C). The concentration of biomass used significantly determined the rate of dye decolorization, as the lowest biomass concentration (0.10 g) was able to completely decolorize the dye by day 3, while the highest biomass concentration (1.00 g l−1) attained 100 % decolorization on day 4. Neutral pHs supported the highest dye decolorization rates compared alkaline pHs. The rate of dye decolorization had a linear relationship with the concentration of the dye in solution as increasing dye concentration in the medium significantly reduced the rate of decolorization (p < 0.05). At 25°C, the rate of dye decolorization was consistently higher from day 2 to the end of the experiment. Infra-red analyses of the algal biomass and the dye solution was done in Kbr by pressing between flat aperture plates of sodium chloride and scanning from 4,000 to 625 cm−1. This revealed the presence of functional groups associated with the biomass and dye that provided possible explanations for the decolorization of the dye under the different incubation conditions. These results showed that immobilized S. quadricauda is capable of decolorizing indigo blue dye at low biomass when immobilized with sodium alginate. However, this was dependent on the incubation temperature and dye concentration.