Batch and continuous mode adsorption of methylene blue cationic dye onto synthesized titanium dioxide/polyurethane nanocomposite modified by sodium dodecyl sulfate

Abstract

In this study, we synthesized and characterized a modified polyurethane (PUF) adsorbent using Sodium Dodecyl Sulfate (SDS) and TiO2-PUF nanocomposite. The adsorption performance of these modified PUF adsorbents was evaluated for the removal of Methylene Blue (MB) dye from wastewater. Optimum values and conditions for the adsorption process were determined based on the maximum dye adsorption (temperature 25 ℃, equilibrium contact time 180 min, adsorbent dose 0.2 g, pH 9 and initial concentration 120 mg/L). The surface-modified PUF adsorbent exhibited significantly enhanced adsorption capacity, increasing from 6.25 to 20.12 mg/g compared to the pure PUF. Langmuir and Freundlich adsorption isotherm models were applied, with the Langmuir model providing the best fit (R2 = 0.99) and a maximum adsorption capacity of 120.48 mg/g of the adsorbent. Thermodynamic studies indicated an exothermic adsorption process, while the pseudo-second-order kinetic model dominated the adsorption kinetics. Continuous experiments at optimized conditions revealed an optimum flow rate of 15 mL/min and a bed height of 2 cm for efficient dye uptake. The adsorbent demonstrated good regeneration and reusability over more than 3 cycles. The modified PUF adsorbent showed great potential for MB dye adsorption. Surface modification significantly improved the adsorption capacity, and the Langmuir model accurately described the adsorption behavior. These findings contribute to our understanding of PUF adsorbents and their applicability for wastewater treatment.