Optimization of synthetic dyes removal from wastewaters using loofah biomaterial: equilibrium, kinetic, and thermodynamic studies

In this study, loofah was used to remove organic dyes (crystal violet, methylene blue, and basic fuchsine) from an aqueous solution by biosorption. The effects of operating parameters, such as contact time, initial pH, dyes concentration, size of biosorbent and temperature, on the discoloration yields were evaluated. The experimental results revealed that the highest removal efficiencies of crystal violet, methylene blue, and basic fuchsine were 99.5%, 98.66%, and 85%, respectively, at the optimum conditions (operating time of 60 min, initial pH (6.92 for the crystal violet, 6.60 for methylene blue and 8.53 for basic fuchsine), dyes concentration of 6 mg/L, size of loofah squares S = 16 cm(2) and temperature of 60 degrees C). The structural characterization of the loofah after biosorption of dyes using Fourier-transform infrared spectroscopy analysis showed an intensity reduction of the characteristic peaks of the hydroxyl groups and the apparition of novel characteristic peaks of amine groups indicating thus the fixation of dyes on loofah. Equilibrium isotherms models showed that the Langmuir isotherm model gives the best fit for the experimental data with the best regression coefficient R-2 > 0.99. Adsorption kinetics showed that the biosorption followed a pseudo-second-order reaction. Thermodynamic study indicates an endothermic process with physical nature.