Porous Biodegradable Bamboo Fibers for Efficient Oil Droplet Separation in Emulsified Oily Wastewater

A biodegradable and porous bamboo fiber (F-BF) demulsifier was prepared by pretreatment and grafting of polyethylenimine on the bamboo fiber (BF) surface via the Schiff base reaction. After that, factors such as oil concentration, F-BF dosage, pH value, temperature, and salinity of emulsified oily wastewaters on F-BF demulsification were explored in detail. The results demonstrated that the demulsification efficiency (Ed) decreased with increasing oil concentration. The maximum Ed values achieved were 97.4% (pH 4.0), 95.2% (pH 7.0), and 86.5% (pH = 10.0), respectively. Moreover, the Ed of F-BF increased to 98.2% when the demulsification temperature was increased to 80 °C. Furthermore, the Ed of F-BF increased from 96.8 to 99.2% eventually when the concentration of NaCl was increased from 0 to 2.0 wt %. Significantly, F-BF can maintain superior Ed after cycling 5 times, confirming that it has high recyclability. The superior demulsification was ascribed to its positive surface charge under acidic and neutral environments, high interface activity, and interface interactions between the lignin of F-BF and interface-active species of emulsified oily wastewater. In addition, NaCl electrolytes migrated quickly to the interfacial region, which helped weaken the asphaltenes and resin layers during the demulsification process. Therefore, F-BF has positive application prospects in the field of emulsified oily wastewater treatment.