SEPARATION OF OIL/WATER MIXTURES BY CHEMICALLY MODIFIED MELAMINE FOAMS

Abstract

Polymeric foams represent suitable porous sorbents for separating various contaminants dispersed in water. One of the most common polymeric foams is melamine (ME) foams, which are particularly suitable for removing oil impurities from water. The commercial ME foams provide facile, low-cost, recyclable, and efficient methods for treating oily water. ME foams are inherently highly oleophilic and hydrophilic. However, for practical reasons, it is suitable to enhance, or at least conserve olephilicity on the one hand, but suppress hydrophobicity on the other hand, and vice versa, to ensure efficient separation of oil/water mixtures. In this work, a simple modification of ME foams was realized by their immersion in FeCl3 solution. The process, due to the reaction of melamine resin with Fe3+ cations, leads to the significant enhancement of hydrophobicity of ME foams (water contact angle ≥150°), maintaining their superolephilic character (oil contact angle ~ 0°). The modified foams performed excellent separation efficiency for treating of various oily emulsions, synthetic produced water, oil/water mixtures, and showed high sorption ability of free oil. Two types of oil in water emulsions were prepared and studied in this work, namely emulsions prepared by dispersion of diesel oil in distilled water, and synthetic produced water, which was prepared in such a way to mimic the real produced water by-produced from the petroleum industry. The ME foam purified highly concentrated diesel emulsions up to 1000 ppm of oil component with an efficiency of 94%. Synthetic produced water was also treated successfully by the modified foams with 91% efficiency. Even much higher separation efficiency was demonstrated for separation of o/w mixtures with volume portion of oil up to 60 vol.%., where the separation efficiency was greater than 99%. Finally, the oleophilic foams also exhibited high and fast sorption capability to remove free oils having an oil sorption capacity of 98-112 g/g. The approach explored in this work represents a cost-effective, scalable, and facile method of modifying ME foams, making them a feasible sorbent material for treating different types of oily polluted waters.