Preparation and application of low-cost fibers for efficient adsorption of oil from coal pyrolysis wastewater and establishment of quantitative equation for calculating oil contact angle under water

The removal of oil from coal pyrolysis wastewater persists to be a challenging problem. Thus, this study proposes a new scheme that integrates the adsorption of oil using fibers and subsequent centrifugation or elution to achieve efficient oil–water separation. Based on their stable chemical property, PP and were selected as the substrates for drawing the fibers. In addition, PVDF and PTFE were explored to modify the wettability of PP and PE. The performances of as-prepared fibers were tested for removing oil from wastewater in both batch and continuous modes. Among all the fibers, the PVDF-modified PP fibers exhibited the best performance. For PP-based fibers with 5 wt% PVDF, the saturated oil-removal efficiency reached 92.24 % in case of the simulated wastewater and 81.10 % for the actual wastewater. Given that the oil content in coal pyrolysis wastewater was ~2000 ppm, the residual oil content in the outlet water would be ~380 ppm, which satisfies the requirement of the subsequent treatment process. Furthermore, the PVDF-modified PP fibers exhibited excellent reusability and stability to defy various environmental corrosions. The separation of oil and water based on the adsorption by fibers offers promising prospect to remove oil from coal pyrolysis wastewater. In addition, we derived a formula to calculate the oil contact angle under water based on Young's equation using several measurable parameters. As the calculation results were consistent with real scenarios, this derived formula can provide quantitative guidance for material modification in coal wastewater treatment .