A Comparison between Various Polymeric Membranes for Oily Wastewater Treatment via Membrane Distillation Process

Area of Science:

• Environmental Science and Engineering
• Materials Science
• Chemical Engineering

Background:

• Oily wastewater (OW) poses significant environmental and health risks, necessitating advanced treatment solutions.
• Membrane technology, particularly membrane distillation (MD), offers high pollutant rejection but faces challenges with commercial membrane fouling.
• Effective treatment requires identifying membranes with optimal separation performance and fouling resistance for OW.

Purpose of the Study:

• To evaluate and compare the separation performance of various ultrafiltration (UF) and nanofiltration (NF) membranes for treating oily wastewater.
• To assess the efficacy of membrane pressure-filtration versus membrane distillation (MD) in removing oil contaminants.
• To identify membranes with superior performance and investigate fouling and wetting characteristics for optimized OW treatment.

Main Methods:

• Tested six UF and NF membranes (NFS, NFX, XT, MT, GC, FILMTEC) for oily wastewater (100 ppm) separation performance.
• Compared pressure-driven membrane filtration and MD for long-term treatment (2 hours, 5000 ppm oil concentration) using XT and MT membranes.
• Analyzed membrane flux, oil removal rates, contact angles, and fouling/wetting behavior.

Main Results:

• XT and MT UF membranes exhibited the best performance, with high flux and oil removal rates (>99% for XT).
• MD showed higher oil removal efficiency but experienced significant flux reduction (82%) compared to membrane pressure-filtration (25%).
• Hydrophilic XT and MT membranes demonstrated fouling resistance, but MD encountered wetting issues, leading to flux reduction.

Conclusions:

• The XT and MT UF membranes are promising for oily wastewater treatment, with XT achieving >99% oil removal.
• While MD offers high rejection, membrane wetting and significant flux reduction necessitate further investigation and membrane modification.
• Developing modified dual-layer membranes with tailored hydrophobic/hydrophilic properties is crucial for enhancing anti-fouling and anti-wetting capabilities in MD treatment of oily wastewater.