A full factorial design for the decolorization of real textile wastewater using iron-rich montmorillonite by sonocatalytic process

In this study, the sonocatalytic process was used to remove colour from the effluent of a textile factory located in Turkey. Clay from a brick-tile factory located in the city of Eskisehir was used to enhance the effect of ultrasound (US) at 20 kHz frequency and 750 W power. The structure, morphology and composition of the clay were identified by characterization studies including FT-IR, XRD, XRF, SEM and TGA. The clay consists mainly of montmorillonite and iron-rich montmorillonite as smectite minerals, nontronite, quartz minerals, calcite and dolomite as minor clay minerals. In the scope of the study, Design of Experiment (DoE) and a Full Factorial Design (FFD) was used to determine the operating conditions that affect the color removal efficiency of textile industry wastewater. pH, clay amount, time, and H₂O₂ concentration were determined as critical factors using Analysis of Variance (ANOVA). It has been confirmed that when the critical factors for color removal efficiency—specifically, a pH of 2, 2 g of clay, a duration of 120 min, and 35 ppm of H₂O₂—are kept constant, the resulting removal percentage was predicted as 94 % approximately by using regression model. The optimal levels of factors have been verified by the validation experiments.