Micellar Enhanced Ultrafiltration (MEUF) Using Cetylpyridinium Chloride (CPC) and Hexadecyltrimethylammonium Bromide (HDTAB) Surfactants for Fluoride Rejection: Modeling and Process Optimization

Introduction: The current study aimed to optimize micellar-enhanced ultrafiltration (MEUF), a low-pressure membrane method, for removing fluoride from water, a contaminant linked to serious health risks such as fluorosis-through two cationic surfactants. Methods: In this study, a dead-end ultrafiltration system was employed to remove fluoride using cetylpyridinium chloride (CPC) and hexadecyltrimethylammonium bromide (HDTAB). Important operational parameters such as pH (4-10), initial fluoride concentration (4-10 mg/L), and surfactant concentration (0.5-1.5 mM) were modeled and optimized via Response Surface Methodology (RSM) based on a Box-Behnken design. Results: Analysis of variance (ANOVA) confirmed the high significance of the developed quadratic models, with regression coefficients (R2) of 0.99 and 0.97 for CPC and HDTAB, respectively. The optimal removal efficiencies were 94.5% for CPC (at pH 8, 1.2 mM CPC, 8 mg/L F-) and 89.6% for HDTAB (at pH 7, 1.4 mM HDTAB, 10 mg/L F-). Under the optimum conditions, flux values of 268.1 L/m2.h and 276.5 L/m2.h were also obtained for CPC and HDTAB, respectively. Conclusion: It was found that MEUF is an effective technique for fluoride rejection. And the RSM successfully modeled and optimized the process, with CPC demonstrating superior performance and model predictability compared to HDTAB. These observations suggest that the proposed system can be reliably applied to larger-scale fluoride removal from aqueous solutions.