Effect and mechanism of an anionic surfactant on membrane performance during direct contact membrane distillation

Membrane Distillation Hybrid Peroxydisulfate Activation toward Mitigating the Membrane Wetting by Sodium Dodecyl Sulfate

“…When the SDS concentration was increased to 0.8 mM, the PVDF membrane sharply lost its vapor permeability within 2 h, while the flux of the PTFE membrane gradually dropped to a final value of 4 kg/m 2 /h, with the performance of their permeate conductivity in line with the flux behavior (not further extended). Previous studies have confirmed experimentally and theoretically that the SDS monomers tend to distribute on the membrane surface due to hydrophobic-hydrophobic interaction between the non-polar tails of the SDS and the hydrophobic membrane, and the adsorption of SDS would finally turn the membrane hydrophilic, partially wetted [32][33][34][35][36]. The present data agreed with the membrane wetting phenomenon by surfactant adsorption and highlighted the different behavior of two membrane coupons.…”

“…Since the above fouling/wetting phenomenon in Figures 4 and 5 was hypothesized to be the consequence of SDS attachment onto the membrane matrix under their hydrophobichydrophobic affinity, FTIR analysis was performed to confirm the existence of SDS on the used membranes (Figure A2) with respect to the pristine membranes. Note the information given by SDS moiety includes two peaks around 2926 cm −1 and 2851 cm −1 , which were attributed to CH 2 symmetric and asymmetric stretching, respectively [34,37]. The results indicated that the featured peak for SDS was only slightly observable on the PTFE membrane dealing with feed containing a relatively higher SDS quantity (null for the PVDF membrane dealing with feed of 0.5 mM SDS).…”

Understanding the fouling/scaling resistance of superhydrophobic/omniphobic membranes in membrane distillation

“…Similarly, long chain hydrocarbon oil, often found in the shale oil and gas produced water [17], readily fouls MD hydrophobic membranes because of the long-range hydrophobic-hydrophobic attraction [86,87]. Surfactants' lyophobic tails show strong affinity to hydrophobic membrane [30,80,88,89], but hydrophilic head-groups incur hydrophilic characteristics [81]. Once fouled by the surfactants, the membranes are prone to wetting by the feed streams though some contradictory results have been reported.…”

“…The interfacial free energy between the membrane and foulant provides an indication of the attraction or repulsion between two materials. xDLVO theory has often been utilized to interpret experimental results [67,87,89,[126][127][128][129] and severe organic fouling has been ascribed to hydrophobic-hydrophobic interactions [67,75,77,79,87]. The theory implies that the electric interaction between the foulants and the hydrophobic membrane surface is negligible comparing to the LW and AB interactions [87,130].…”

Mitigation of Membrane Wetting by Applying a Low Temperature Membrane Distillation

“…This phenomenon decreases organic rejection and worsens the quality of the distillate, which is similar to effects when the pores are wetted by water. Rapid wetting of membranes causes the presence of surfactants in the feed, such as sodium dodecyl sulfate (SDS) [ 11 ]. Even at low SDS concentration (over 0.1 mmol/L), the membranes were wetted during a few hours of the MD process.…”