Comprehensive experimental design for synergetic membrane filtration–adsorption purification of emulsified oil wastewater

To address the practical challenges of treating highly stable emulsified oil wastewater in industries such as petrochemicals and machining, and to meet the curriculum standards of “high-level, innovative, and challenging,” a comprehensive experimental project was designed for wastewater purification via the synergistic application of “membrane filtration–adsorption.” Based on the physicochemical properties of industrial emulsified oil wastewater (oil content: 5%–8%, initial chemical oxygen demand (COD): 3462.5 mg·L^–1, and initial turbidity: 190 NTU; main components: phenol, anthraquinone, alkanes, alkenes, alkynes, and organic acids), students are first guided to review relevant literature, identify technical bottlenecks in controlling membrane pore structure and enhancing adsorbent capacity, and then independently synthesize asymmetric carbon membranes and porous carbon materials.

Asymmetric carbon membranes are prepared using sol–gel and dip-coating methods. Porous carbon is fabricated with two formulations (solid content of 10 wt% and 20 wt%), followed by sol–gel formation, aging, drying, and carbonization. To regulate material characteristics and monitor water quality, students use modern analytical techniques, such as scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, physical adsorption analysis, and ultraviolet–visible spectroscopy. The results show that the asymmetric carbon membrane has a separation layer with a thickness of ~6.25 μm and a pore size of 8.3 nm, whereas the porous carbon with 20 wt% solid content exhibits a higher specific surface area (591.36 m²·g^–1) and micropore volume (0.28 cm³·g^–1). Based on these materials, a multitechnology coupled wastewater treatment system is established by filling porous carbon into the asymmetric carbon membrane tube, and its performance is evaluated using a dead-end filtration device using COD and turbidity as primary indicators. During the experiment, students optimize process parameters, such as transmembrane pressure difference (0.1–0.3 MPa), and investigate the influence of membrane pore size and porous carbon solid content on treatment efficiency.

The “membrane filtration–adsorption” system achieves a COD removal of 84.4% (leaving only small amounts of anthraquinone and organic acids) and 100% turbidity removal using porous carbon with 20 wt% solid content and a transmembrane pressure difference of 0.2 MPa. These results significantly outperform single membrane filtration (72.2% COD removal) or single adsorption (34.7% COD removal). Analysis of the purification mechanism shows that, driven by pressure, emulsified oil wastewater first flows through the asymmetric carbon membrane, where particulate pollutants, color, and most emulsified oil are removed via membrane filtration. The remaining soluble pollutants are subsequently removed through adsorption on porous carbon. The combined use of asymmetric carbon membrane filtration and porous carbon adsorption greatly improves COD removal, enabling efficient, one-step purification of emulsified oil wastewater.

This experiment engages students in the full research process: designing porous materials, analyzing industrial wastewater quality, optimizing process parameters, and interpreting the synergistic purification mechanism. It overcomes the limitations of traditional single-material experiments by integrating knowledge from multiple disciplines, such as environmental and chemical engineering. Simulating real industrial scenarios enhances students’ understanding of core theories (e.g., membrane filtration and adsorption) while cultivating their systematic thinking, practical engineering skills, and innovative problem-solving abilities for complex environmental engineering challenges.