Anti-Fouling Double-Skinned Forward Osmosis Membrane with Zwitterionic Brush for Oily Wastewater Treatment

Abstract

Despite its attractive features for energy saving separation, the performance of forward osmosis (FO) has been restricted by internal concentration polarization and fast fouling propensity that occur in the membrane sublayer. These problems have significantly affected the membrane performance when treating highly contaminated oily wastewater. In this study, a novel double-skinned FO membrane with excellent anti-fouling properties has been developed for emulsified oil-water treatment. The double-skinned FO membrane comprises a fully porous sublayer sandwiched between a highly dense polyamide (PA) layer for salt rejection and a fairly loose dense bottom zwitterionic layer for emulsified oil particle removal. The top dense PA layer was synthesized via interfacial polymerization meanwhile the bottom layer was made up of a zwitterionic polyelectrolyte brush - (poly(3-(N-2-methacryloxyethyl-N,N-dimethyl) ammonatopropanesultone), abbreviated as PMAPS layer. The resultant double-skinned membrane exhibited a high water flux of 13.7 ± 0.3 L/m2.h and reverse salt transport of 1.6 ± 0.2 g/m2.h under FO mode using 2 M NaCl as the draw solution and emulsified oily solution as the feed. The double-skinned membrane outperforms the single-skinned membrane with much lower fouling propensity for emulsified oil-water separation.

Research on Forward Osmosis Membrane Technology Still Needs Improvement in Water Recovery and Wastewater Treatment

“…One active skin face to the DS to prevent RSD and another to the FS to prevent the membrane fouling. An anti-fouling double-skinned FO membrane composed with a fully porous sublayer sandwiched between a highly dense polyamide (PA) layer and a fairly loose dense bottom zwitterionic layer made up of a zwitterionic polyelectrolyte brush was used for highly contaminated emulsified oil-water treatment [39]. Much lower fouling propensity and higher water flux (13.7 ± 0.3 L/m 2 , 2 M NaCl) were observed compared with the single-skinned membrane.…”

Fouling and Cleaning in Osmotically Driven Membranes

“…On the other hand, ODM systems use the osmotic pressure gradient, which is the chemical potential difference between the feed water and the concentrated draw solution as its driving force. With this application, the use of external pressure is not needed [3,10,17,18]. As a result of this, the system is said to be more economically viable due to its significantly low Fouling and Cleaning in Osmotically Driven Membranes http://dx.doi.org/10.5772/intechopen.73047 energy consumption [19].…”

“…la _______ la . la (10) where D ml is diffusion coefficient of the solutes inside the fouling layer; la is porosity and la the thickness and la is the tortuosity of the fouling layer, respectively.…”

“…Studies on the fouling in ODMs have revealed that fouling propensity within the ODMs is lower as compared to PDMs [2,3,9,10]. The lower fouling propensity is said to be so in the case, whereby the active layer of the membrane is arranged to face the feed solution containing the foulant.…”

“…In addition, the low flux conditions and lack of applied pressure in the FO process have been highlighted as some of the reasons for this occurrence. However, internal concentration polarisation (ICP) could still occur within the membrane [10]. Therefore, ICP is one of the major drawbacks of ODMs especially in FO [3].…”