Equilibrium, kinetics, and thermodynamic studies of the biosorption of Congo red dye by the biomass of Serratia marcescens MM06

Dyes pose environmental risks with carcinogenic effects, felt globally including in Malaysia. Water contamination stems from various sources like manufacturing companies, research, and medical centers. The research aims to study bacterial biomass biosorption of Congo red (CR) dye for industry applications. Twelve different bacterial species were tested against CR. The study screens and optimizes the bacterial sorption process using a one-factor-at-a-time (OFAT) approach, and characterizes the biosorbent through FTIR analysis, SEM imaging, adsorption kinetic and isotherm modeling, and thermodynamic evaluation. Serratia marcescens strain MM06 re- moved the most dye among 12 bacterial isolates. Biomass was incubated with 100ppm dye, then centrifuged and measured at 507nm. Optimal conditions after OFAT were 25 °C, pH 7.0, 125 rpm agitation, 20 min, 90 mg/L dye concentration, and 0.94g absorbent dosage. FTIR and SEM characterized biosorption. Nonlinear regression analyzed isotherms and kinetics, revealing pseudo-second-order and Langmuir as best fits. The parameters of the fitted isotherms, namely, Langmuir, Freundlich, BET, Sips, Fritz-Schlunder IV, and Fritz-Schlunder V were 4.387657 mg/g, 3.750862 mg/g, 4.387657 mg/g, 2.800659 mg/g, 12.178957 mg/g, 2.557313 mg/g respectively. The parameters of thermodynamic Gibbs free energy (DG), enthalpy (DH), and entropy (DS) modifications indicated exothermic and spontaneous processes. Serratia marcescens MM06 proved effective for CR dye removal from wastewater.