Abstract A rotatable central composite design was employed to optimize the operational parameters for textile wastewater treatment via Direct Contact Membrane Distillation. Using synthetic dye solutions (disperse and reactive classes) and a polytetrafluoroethylene (PTFE) membrane, this study systematically analyzed the effects of feed and permeate flow rates and feed temperature on permeate flux. Interaction effects were identified, and response surface curves revealed that, despite specific variations between dye classes, the optimal conditions were identical (feed flow rate = 4.0 L.min⁻¹, permeate flow rate = 1.0 L.min⁻¹, feed temperature = 84 °C). Water quality analysis showed color rejection exceeding 99% in both cases, demonstrating robust performance across different conditions. Statistical validation confirmed the model’s reliability, with high coefficients of determination (R 2 = 0.93 for reactive dye, R 2 = 0.95 for disperse dye). Tests with real wastewater under optimized conditions showed membrane wetting in cotton dyeing effluents due to high chemical concentrations, whereas polyester dyeing wastewater achieved a permeate flux of 40.6 kg.m⁻².h⁻¹ with over 99% color rejection. Membrane characterization confirmed surface stability and the integrity of functional groups. This study highlights the distinct influences of operational conditions on permeate flux across dye classes. Quantifying these effects through statistical analysis, it enables a comparative evaluation of their impact. Finally, it provides valuable insights for implementing membrane distillation in the textile industry, optimizing operational variables to improve wastewater treatment efficiency and reduce costs. Graphical Abstract
Silva et al. (Fri,) studied this question.