An efficient removal of crystal violet from aqueous solution using rhamnolipid micellar solubilization followed by ultrafiltration and modeling of flux decline

Abstract

Micellar‐enhanced ultrafiltration (MEUF) using rhamnolipid (RHL) biosurfactant has been shown to be an effective and promising method for removal the hazardous heavy metal ions and organic pollutants from aqueous stream. However, the potential application of rhamnolipid was not explored much in the treatment of dye wastewater. The aim of this study was to evaluate the performance of the rhamnolipid based MEUF process for the removal of crystal violet (CV) from the aqueous solution. MEUF experiments were performed in both dead-end stirred cell and cross-flow cell. Response surface methodology was used to optimize the MEUF feed conditions. Under optimal feed conditions (RHL: 175 × 10-3 kg m-3; CV: 32 × 10-3 kg m-3; NaCl: 15 kg m-3 and pH: 8.3), the maximum CV rejection efficiency was found to be 99.5%. This study also investigated the effects of the transmembrane pressure difference, cross-flow velocity and feed temperature, on the CV rejection efficiency and profiles of permeate flux and fouling resistance. A model based on resistance-in-series theory coupled with Hermia’s cake filtration model adapted to cross-flow was developed together with the expression of transition time of fouling mechanism, to analyze the flux decline behavior during operation. The experimental flux decline data were in good agreement with the model predictions. The proposed model was also found to be applicable to sodium dodecyl sulfate (SDS) based MEUF process for removal of CV. For similar CV rejection efficiency, the present study showed a 31.5% lower operating cost compared to SDS based system.