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

Abstract

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.

Liquid-like nanofluid mediated modification of solar-assisted sponges for highly efficient cleanup and recycling of viscous crude oil spills

“…Due to its high porosity and strong stability, a commercial polyurethane sponge (PUS) was chosen as a porous substrate. 35 In Fig. 1, the detailed design route of the porous polymer membrane based on SiO 2 nfs is presented.…”

Effects of Different Mold Materials and Coolant Media on the Cooling Performance of Epoxy-Based Injection Molds

“…Figure 15 shows the SEM micrograph of injection mold made with Cu-filled epoxy resin. The underlying reason is that the mixture is easier to generate porosity [23] when the Cu powder was added in the epoxy resin, which will affect the heat transfer effect of the fabricated injection mold. Figure 14 shows cooling time of injection molded parts fabricated by ten sets of injection molds cooled with different cooling water temperatures.…”

Polymeric Membranes for Oil-Water Separation: A Review

“…The exploration, production, transportation, and refining of crude oil are always associated with the separation of water-oil mixtures as the primary stage of oil refining or due to the accidents resulting in the oil spilling. In the case of oil-polluted surface waters, there are a big variety of adsorbents traditionally used to collect the excess of the oil, including sponges [ 1 , 2 ], foam materials [ 3 ], and natural adsorbents [ 4 ]. However, the complete cleaning of water from the presence of the oil is complicated by the formation of oil-water emulsions, which become more stable due to the presence of different components in the oil or to water acting as emulsifiers such as asphaltenes, resins, mineral salts, clay particles, etc.…”