Biosorbents based on residual biomass of Lactobacillus sp. bacteria consortium immobilized in sodium alginate for Orange 16 dye retention from aqueous solutions

Residual biomass from the lactic acid production (fermented dairy industry) represents a viable and important source of valuable compounds (nutrient, material) and energy which can be used as raw material for the production of a wide range of new added-value products and in certain valorisation processes and sanitation services. The aim of this work is to use the prepared biosorbent from the residual biomass (a Lactobacillus plantarum and Lactobacillus casei bacteria consortium, separated after the biosynthesis process by centrifugation and dried at 80 degrees C) immobilized in sodium alginate (by cell inclusion technology) (in form of spherical beads with 0.5 and 1.5 mm in diameter) into a specific biosorption treatment step applied for certain aqueous solutions containing the reactive Orange 16 dye (28.96-231.68 mg/L). The biosorption potential of this imobilized residual bacteria consortium for the reactive Orange 16 dye retention from aqueous solutions was studied in a batch system. The preparation and characterization of the obtained biosorbent (SEM and FTIR spectra), the analysis of different equilibrium isotherm (Langmuir, Freundlich and Dubinin-Radushkevich - D-R) to estimate the quantitative characteristic biosorption parameters, thermal effect and possible action mechanism were investigated, and the modeling of experimental data was satisfactorily achieved. Langmuir was found the most suitable isotherm model (L II) and the basic mechanism is found to be of physical type, being spontaneous (probably exothermic) after the calculated values of the free biosorption energy (E = 13 kJ/mol, from D-R equation), free Gibbs energy (Delta G degrees = -1.845 - -1.768 kJ/mol) and biosorption enthalpy (Delta H degrees = -6.512 kJ/mol). Analysis of SEM images and FTIR spectra suggests that Orange 16 reactive dye is retained on biosorbent granules by a physical adsorption mechanism. The obtained results conclude that this residual bacterial biomass immobilized in sodium alginate can be a good biosorbent in static operating system for reactive organic dye-containing effluents.