An environment friendly multifunctional ZnO/wood fiber composite for the treatment of wastewater mixed with emulsions and dye

In general, oily wastewater is a complicated combination of dye wastewater, bacteria, and other pollutants. However, most of the materials used for treating oily wastewater are single-function. Effectively removing emulsions and dyes simultaneously from mixed wastewater is challenging. In this study, we chose wood fiber as a supporting material. ZnO was uniformly grown on the surface of the wood fiber by a one-step hydrothermal method. After freeze-drying, a ZnO/wood fiber composite was successfully created. The composite was hydrophilic and oleophobic and had excellent antibacterial characteristics (>99.94%). The effectiveness of the composite in the separation of oil-in-water emulsions stabilized with a surfactant could reach 99.31%, owing to ZnO's enhanced emulsion breaking and separation capabilities. In addition, ZnO may interact electrostatically with dye molecules, allowing for 99.92% efficiency in dye adsorption during emulsion separation. Then, ZnO provided ZnO/wood fiber composite photocatalytic degradation of dyes, which allowed for repeated recycling of the ZnO/wood fiber composite, resulting in 98.80% emulsion interception and 99.90% dye removal after five cycles. The environment friendly ZnO/wood fiber composite has remarkable multifunctionality for emulsion separation, dye adsorption, self-cleaning, and antibacterial properties, which provides a novel treatment option for mixed emulsion and dye wastewater.