Factorial design analysis for biosorption of Reactive Red-84 dye using fermentation spent waste biomass, biosorbent regeneration and desorbed dye photo-degradation using TiO₂ nanoparticles

Abstract

In this work, factorial design analysis based on central composite design of experiments was employed to study the effect of process parameters for biosorption of Reactive Red-84 dye onto bioethanol fermentation spent waste biomass of Saccharomyces cerevisiae. Factorial experiments with five factors: mixing rate rpm, incubation period h, process temperature °C, initial dye concentration mg/L and biosorbent dosage wt% (w/v) at three levels were conducted. A highly statistically significant quadratic model at 95% confidence level (p < 0.0001, R² 0.9120 and 0.8519) was developed to charcterize the influence of the different considered variables on biosorption efficiency. Response surface methodology was employed to optimize the process, recording maximum biosorption % of ≈62% (51.67 mg/g) at 90 rpm, 13 h, 15°C, 100 mg/L and 0.6%, respectively. Approximately 95% of adsorbed dye was desorbed by elution with NaOH solution of pH 9 and the regenerated biosorbent was employed for four successive cycles. TiO₂ nanoparticles 6–15 nm were prepared and used for photo-catalytic degradation of desorbed dye solution. The proposed integrating biosorption and photo-catalytic degradation process results in no secondary pollution in the form of any concentrated wastes, which is an important environmental aspect.

Keywords:

• Biosorption
• Response surface methodology
• Photo-catalytic degradation
• Reactive Red-84
• TiO₂ nanoparticles