Natural deep eutectic solvent modified nanofiltration membranes with superior antifouling properties for pharmaceutical wastewater treatment

Abstract

Herein, the L-menthol/10-camphorsulfonic acid (L-M/CSA) natural deep eutectic solvent (NDES) was introduced as an innovative modifier for polyethersulfone (PES) nanofiltration (NF) membrane. Four membranes with different L-M/CSA NDES loadings (0, 0.2, 0.6, and 1 wt%) were prepared and characterized to evaluate the influence of L-M/CSA NDES on the properties of the membranes. The modified membrane with 0.2 wt% L-M/CSA NDES (M-0.2NDES) showed the pure water flux (PWF) of 111.5 L/m2h, which was about 7 times higher than that of the control membrane (M-0NDES). Meanwhile, the mean pore radius was increased from 0.7 nm for the M-0NDES membrane to 0.85 nm for the M-0.2NDES membrane, indicating the good pore forming capability of L-M/CSA NDES. Benefiting from L-M/CSA NDES blending, the modified membranes showed excellent removal efficiency to ceftriaxone (CTX) and amoxicillin (AMOX) solutions. Particularly, the M-0.2NDES membrane possessed 99.6 and 99.2% rejection to CTX and AMOX, respectively, with permeated flux up to about 111 L/m2h, which was far better than the data reported in the literature. M-0.2NDES membrane showed 89.1% chemical oxygen demand (COD), 100% turbidity, and 51.6% total dissolved solids (TDS) removal from the industrial pharmaceutical wastewater. Blending with L-M/CSA NDES was also confirmed to be crucial to ameliorate the membrane antifouling properties. The related results revealed that the flux recovery ratio (FRR) of the M-0.2NDES membrane for milk solution reached 90.2%. The facile fabrication method of L-M/CSA NDES from green materials, good pore forming capability, enhanced antifouling properties, together with the efficient pharmaceuticals removal indicated the good prospect of L-M/CSA NDES for membrane separation applications.