Performance studies of indigo dye removal using TiO2 modified clay and zeolite ultrafiltration membrane hybrid system

Dyes contamination causes serious damages to aquatic life and human health. With the increase in these persistent organic contaminants accumulation around the world, performant environmentally friendly and low-cost materials and techniques are required to protect the ecosystem and humans. In this study, the efficacy of titania-smectite nanocomposites (Sm-TiO2 NCs) at removing indigo blue (IB) dye was assessed by both batch adsorption and hybrid treatment combining adsorption and ultrafiltration (UF) processes. During the adsorption, the effect of different parameters on IB removal such as dose of Sm-TiO2, contact time, pH and IB concentration were studied. The optimal conditions were applied for the Sm-TiO2 during dye removal using adsorption/UF hybrid treatment. At 293 K and pH 2.5, an optimized dose of Sm-TiO2 (100 mg/L) removed 73% of the IB from a 25 mg/L solution in 240 min with an equilibrium adsorption capacity greater than 180 mg/g. The adsorption of IB dye by Sm-TiO2 NCs followed the Langmuir adsorption isotherm model and pseudo-second-order kinetics. The thermodynamic studies revealed that the adsorption process was spontaneous and exothermic. When a hybrid process was applied, a higher IB removal capacity has been obtained with a lower dose of Sm-TiO2 compared to the case of the batch adsorption process. In addition, the presence of Sm-TiO2 NCs has been found to reduce the UF membrane fouling. In this case, the adsorption followed by UF treatment applied in two stages was modified to a single-stage hybrid process. Permeate flux was increased from 71 L/h m2 (only UF) to 182 L/h m2 (Sm-TiO2/UF).