Use of rhamnolipid in micellar‐enhanced ultrafiltration for simultaneous removal of Cd⁺² and crystal violet from aqueous solution

Abstract

The application of rhamnolipid (RHL) in micellar‐enhanced ultrafiltration (MEUF) was investigated to remove both cadmium ion (Cd+2) and crystal violet (CV) simultaneously from aqueous solution. The effects of the membrane pore size, feed conditions, and operating conditions on solute removal efficiency and permeate flux were studied. Response surface methodology (RSM) was used to obtain the optimal feed conditions. Eigenvalue analysis was performed to evaluate the nature of optimal condition. Critical micelle concentration and aggregate size of RHL in the presence of Cd+2 and CV were determined. Ultrafiltration data were used to estimate the partition coefficient, distribution coefficient and relative affinity of the pollutants, and loading capacity of RHL vesicles. Compared with chemical surfactants, the use of RHL in MEUF process with larger membrane pore size performed better in terms of process throughput. About (84 ± 1)% of initial RHL was recovered from retentate stream using acid precipitation technique, at the optimal recovery condition obtained through RSM. The experimental results obtained using optimal feed condition and RHL recovery condition matched well with the predicted results. Reclaimed RHL was successfully used two times in MEUF with rejection efficiency of 96.7% for Cd+2 and 97.8% for CV, thus, significantly lower the cost of the MEUF process.