Omniphobic PVDF Hollow Fiber Membrane Surface Engineering for Wetting-Resistant Direct Contact Membrane Distillation of High-Salinity Oilfield Produced Water

This study investigates omniphobic surface engineering of PVDF hollow fiber membranes via hierarchical nanoparticle-fluoropolymer coating for wetting-resistant direct contact membrane distillation of oilfield produced water within the context of chemical engineering and membrane separation technology, an area of growing scientific importance given its implications for produced water desalination for oilfield water reuse, zero liquid discharge systems, and hypersaline industrial wastewater treatment. Using contact angle goniometry, liquid entry pressure measurement, and 72-hour DCMD flux stability testing with surfactant-containing high-TDS produced water at 60/20 C feed/permeate, we examine hierarchical re-entrant surface geometry preventing Wenzel-state wetting by reducing solid-liquid contact fraction, with low-surface-energy fluorosilane coating providing thermodynamic wetting resistance to surfactant-laden brines in 28 membrane variants (7 surface treatments x 4 nanoparticle loadings) tested in 72-hour DCMD stability runs against 5 produced water chemistries (TDS 50,000-180,000 mg/L) drawn from bench-scale DCMD test cell with hot/cold recirculation loops at feed temperature 60 C and permeate temperature 20 C. Results indicate that 1.0 wt% SiNP-PFOTS omniphobic membrane maintains 98.4% salt rejection and 24.2 LMH water flux for 72 hours against 120,000 mg/L TDS produced water with 0.1 mM SDS surfactant, versus wetting failure at 8.4 hours for unmodified PVDF (p < 0.001), with 72-hour wetting resistance vs. 8.4-hour failure for unmodified PVDF; 98.4% salt rejection maintained as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to chemical engineering and membrane separation technology and carry actionable implications for the design of programs and policies targeting produced water desalination for oilfield water reuse, zero liquid discharge systems, and hypersaline industrial wastewater treatment.