Optimization, kinetics, and thermodynamics aspects in the biodegradation of reactive black 5 (RB5) dye from textile wastewater using isolated bacterial strain, Bacillus albus DD1

Abstract

This study is aimed to model and optimize the decolorization of reactive black 5 (RB5) dye using Bacillus albus DD1. The response surface methodology (RSM) along with rotatable central composite design (rCCD) is used to optimize the response, % decolorization with four input variables: (i) pH (5–9), initial dye concentration (50–500 ppm), the composition of yeast extract as nitrogen source (0.2–1%) and amount of bacterial inoculum (5–25% v/v). The % decolorization is predicted to be ≈ 98% at the optimized condition (pH ¼ 7.6, dye concentration ¼ 200 ppm, bacterial inoculum ¼ 20 v/v% and yeast extract ¼ 0.4%). Furthermore, the kinetics and thermodynamics of RB5 degradation are also determined. The kinetic order of biodegradation of RB5 is found to follow first-order kinetics with a kinetic rate constant ¼ 0.0384. The activation energy, Ea and frequency factor, A values are calculated as 34.46 kJ/mol and 24,343 (1/Day). A thermodynamic study is also carried out at different temperatures (298 K, 308 K, 310 K, 313 K, and 318 K) using optimized conditions. The values of the DH and ΔS are found to be þ30.79 kJ/mol, and -0.1 kJ/mol/K, respectively using the Eyring–Polanyi equation. The values of ΔG are also calculated at all temperatures.