Evaluation of hydrophobic polyvinyl-alcohol formaldehyde sponges as absorbents for oil spill

Macroporous materials are a class of absorbents used for oil spill cleanup. In this article, novel macroporous and hydrophobic polyvinyl formaldehyde (PVF-H) sponges were prepared by the reaction of stearoyl chloride with hydroxyl groups of hydrophilic PVF sponge at different temperatures. Attenuated total reflectance-infrared (ATR-IR) spectroscopy confirmed the successfully anchoring of hydrophobic stearoyl groups on the PVF networks. Scanning electron microscopy (SEM) images demonstrated that the as-prepared PVF-H had interconnected open-cell structures, and mercury intrusion porosimetry indicated that the average pore size ranged from 60 to 90 μm and porosity was greater than 94.8%. Such PVF-H sponges can absorb oil products effectively, such as toluene, n-hexane, kerosene, soybean oil, hydraulic oil, and crude oil up to 13.7 g·g(-1) to 56.6 g·g(-1), and this level of absorption was approximately 2-4 times higher than that absorbed by commercial polypropylene nonwoven mat. In low-viscosity oils, the samples can reach the saturated absorption amount only in 1 min, but in higher-viscosity oils, absorption equilibrium can be reached in 10 min. In a simulated oil slick system, these macroporous and hydrophobic sponges can still maintain high oil absorption capacities within the range of 14.4 g·g(-1) to 57.6 g·g(-1), whereas a relatively low absorption rate (approximately 20 min) indicated high absorption performance and excellent selectivity in the oil-water mixture. In addition, the absorbed oils were collected effectively only through a simple squeeze. The PVF-H sponges were subjected to 35 absorption-squeeze cycles and exhibited good reusability and 90% recovery for oils. The samples prepared at different temperatures differed in their absorption capacities to some extent. However, this new kind of macroporous and PVF-H sponges had excellent absorption performance on oil products.