An environmentally friendly and cost-effective method to fabricate superhydrophobic PU sponge for oil/water separation

The Separation of Oil/Water Mixtures by Modified Melamine and Polyurethane Foams: A Review

Melamine (MA) and polyurethane (PU) foams, including both commercial sponges for daily use as well as newly synthesized foams are known for their high sorption ability of both polar and unipolar liquids. From this reason, commercial sponges are widely used for cleaning as they absorb a large amount of water, oil as well as their mixtures. These sponges do not preferentially absorb any of those components due to their balanced wettability. On the other hand, chemical and physical modifications of outer surfaces or in the bulk of the foams can significantly change their original wettability. These treatments ensure a suitable wettability of foams needed for an efficient water/oil or oil/water separation. MA and PU foams, dependently on the treatment, can be designed for both types of separations. The particular focus of this review is dealt with the separation of oil contaminants dispersed in water of various composition, however, an opposite case, namely a separation of water content from continuous oily phase is also discussed in some extent. In the former case, water is dominant, continuous phase and oil is dispersed within it at various concentrations, dependently on the source of polluted water. For example, waste waters associated with a crude oil, gas, shale gas extraction and oil refineries consist of oily impurities in the range from tens to thousands ppm [mg/L]. The efficient materials for preferential oil sorption should display significantly high hydrophobicity and oleophilicity and vice versa. This review is dealt with the various modifications of MA and PU foams for separating both oil in water and water in oil mixtures by identifying the chemical composition, porosity, morphology, and crosslinking parameters of the materials. Different functionalization strategies and modifications including the surface grafting with various functional species or by adding various nanomaterials in manipulating the surface properties and wettability are thoroughly reviewed. Despite the laboratory tests proved a multiply reuse of the foams, industrial applications are limited due to fouling problems, longer cleaning protocols and mechanical damages during performance cycles. Various strategies were proposed to resolve those bottlenecks, and they are also reviewed in this study.

Magnetic and Hydrophobic Composite Polyurethane Sponge for Oil–Water Separation

Crude oil spills from offshore oil fields will cause serious pollution to the marine ecological environment. Many 3D porous materials have been used for oil–water separation, but they cannot be widely used due to complex preparation processes and expensive preparation costs. Here, a facile and cheap approach to disperse expanded graphite (EG), stearic acid, and Fe3O4 magnetic nanoparticles on the skeleton surface of polyurethane (PU) sponge to prepare the magnetic and hydrophobic composite polyurethane sponge for oil–water separation. The results show that the composite PU sponge had a strong oil absorption capacity for various oils, the oil adsorption capacities has reached 32–40 g/g, and it has become more hydrophobic. The addition of Fe3O4 magnetic nanoparticles endowed the sponge with magnetic responsivity, and the composite PU sponge still had a strong oil adsorption capacity after several adsorbing-squeezing cycles. The magnetic and hydrophobic composite polyurethane sponge is a very promising material for practical oil adsorption and oil–water separation.

Modification of polyurethane sponge with waste compact disc-derived activated carbon and its application in organic solvents/oil sorption

Polyurethane@activated carbon derived from waste compact disc sponge demonstrated comparable or even better sorption capacity contrasted with other polyurethane-based composites.