(678e) Electrocoagulation Combined with Electrospun Membranes for Membrane Distillation

Development of new cost effective unit operations for recovery, recycle and reuse of wastewater is critical as the demand for water for beneficial uses increases. Unit operations that maximize water recovery are particularly appealing. Membrane distillation is an emerging unit operation that has the potential to maximize water recovery. However, membrane fouling and pore wetting are major challenges that limit the viability of this process. Thus, development of integrated unit operations for treatment of highly impaired wastewaters will be essential. Here we focus on treating oily wastewaters from hydraulic fracturing operations as they are particularly challenging to treat given the range of contaminants present. Here we focus on combining electrocoagulation as a pretreatment step with novel electrospun membranes for membranes distillation that are shown to be fouling resistant.

We have developed a novel PVDF based electrospun membrane to simultaneously solve fouling and pore wetting. Initially a PVDF blended with etyltrimethylammonium bromide electrospun membrane was prepared. Next a second layer was electrospun consisting of PVDF. Negatively charged silica nanoparticles were attached to the PVDF blended with etyltrimethylammonium bromide electrospun membrane by electrostatic adsorption. This creates an amphiphobic surface. Finally, the unmodified PVDF fibers were modified by grafting poly(glycidyl methacrylate-sulfobetaine methacrylate) (zwitterions) to the surface of the PVDF layer. The novel bilayer electrospun membrane was tested using both synthetic and real produced water feed streams. In an alternative method, we have developed a trilayer composite membrane consisting of a hydrophilic membrane, a supporting nonwoven sheet, and a hydrophobic electrospun membrane.

Our novel membranes showed excellent fouling resistance and salt rejection when compared to base PVDF membrane. Further when combined with electrocoagulation we show excellent water recovery form highly impaired produced wasters.