In the textile industry, water mixed with multiple dyes creates complex wastewater. This poses significant treatment challenges. This study evaluates Luffa cylindrica fibres as a biosorbent for removing anionic dyes, in particular indigo carmine (IC) and methyl orange (MO), which are taken as models, from synthetic wastewater. Experiments assessed the effects of initial dye concentration, temperature, salt presence, and desorption characteristics on biosorption. Results showed that Luffa cylindrica fibers had varying biosorption capacities for the two dyes. MO had a significantly higher capacity (Qe = 60.27 mg/g) compared to IC (Qe = 30.84 mg/g) when treated individually. In binary dye solutions, competitive interactions led to a decrease in biosorption capacity for MO (Qe = 50.50 mg/g) and an increase for IC (Qe = 37.04 mg/g) at an initial concentration of 500 mg/L. Thermodynamic analysis revealed that IC biosorption was endothermic, with capacity increasing at higher temperatures, MO exhibited exothermic behavior in single dye solutions but endothermic behavior in competitive interactions. The presence of salts negatively affected biosorption efficiency due to competitive ion presence. Desorption studies highlighted potential for dye recovery and biosorbent reuse. Fourier-transform infrared spectroscopy identified functional groups such as hydroxyl, carbonyl, and carboxyl groups involved in dye adsorption. The Brouers–Sotolongo model provided insights into adsorption kinetics and equilibrium behavior. Luffa cylindrica fibers are a promising, low-cost biosorbent for removing anionic dyes from wastewater. They offer valuable insights into adsorption mechanisms and potential applications in waste treatment processes.
