Separation of Diclofenac using pseudo-emulsion hollow fiber membrane: Optimization by Box-Behnken response surface design

Abstract

Diclofenac (DCF) is an anti-inflammatory drug detected in various aquatic sources and found harmful to aquatic life. In spite of adopting various treatment techniques, complete removal is not observed and remaining DCF can interact with other existing contaminants leading to the generation of more toxic contaminants in wastewater. In the present work, investigations on removal of DCF from aqueous solutions were carried out through Pseudo-emulsion hollow fiber strip dispersion (PEHFSD) technique with pseudo-emulsion consisting of Di-2-ethylhexyl phosphoric acid (D2EHPA) as carrier, n-heptane as diluent and HCl as stripping phase. Morphological features of hollow fiber membrane module were revealed through Field emission scanning electron microscopy which shows pore size and size distribution ranging from 95 nm to 120 nm. Energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy of membrane phase before and after extraction of DCF confirms interaction between D2EHPA and DCF. Contact angle measurement shows that due to hydrophobicity and strong capillary force, membrane phase retains within the micropores of the hollow fiber and helps to diffuse DCF forming DCF-D2EHPA complex. Uniform droplet sizes and size distribution of pseudo-emulsion provides high interfacial contact area and higher extraction efficiency. Studies on permeability and investigations regarding the effect of several operational parameters such as concentration of feed phase (F), carrier (C) and stripping phase (S) for the extraction of DCF as well as multivariable optimization were carried out by Response surface methodology using Box-Behnken design approach. 97.50% extraction of DCF was achieved with PEHFSD technique at optimum conditions.