Commercial polydimethylsiloxane modified melamine sponge for highly efficient oil-water separation

Abstract

Polydimethylsiloxane (PDMS) is considered a low surface energy material widely used in (super)hydrophobic modification. In this paper, the high hydrophobic melamine sponges (MS) were modified with commercial aminopropyl functionalized polydimethylsiloxane (NH2-PDMS) with different molecular mass. The chemical composition, surface morphology, and wettability of the NH2-PDMS-modified MS were investigated by X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and contact angle test. Owing to the porous structure and high hydrophobicity, NH2-PDMS-modified MS possesses remarkable absorption capacity (ranging from 46 to 155 times their own mass). Simultaneously, it can effectively separate oil-water mixtures with high separation efficiencies exceeding 98.2%. NH2-PDMS-modified MS has no obvious change after 10 cycles of oil-water separation. The results demonstrate PDMS molecular mass on surface can revise material properties and achieve high separation efficiencies in oil-water separation.

1. Introduction

Increased oil-solvent spillage and discharges have resulted in serious environmental pollution and ecological problems in past few decades. Therefore, it is an urgent need to develop an economical and straightforward technology for cleanup and recovery of oil/solvent from oily wastewater. Update, many techniques or methods, such as absorption, chemical treatment, and gravity separation, have been widely used in dealing with oily wastewater (such as immiscible oil-water mixtures and emulsions) [1−7]. Among the various methods for oily wastewater treatment, porous materials have emerged as the most promising due to their simplicity, effectiveness, low cost, and absence of secondary pollution. These materials can quickly remove and recycle oil/solvents from oil-water mixtures [8, 9]. In absorption process, the selection of absorbent materials is important, and these materials are used in different forms. Nowadays, the most used absorbent material forms are sponge [10−12], mesh [13, 14], aerogel [15, 16], fabric [17], and nanofiber [18, 19] for the removal of oils or for the separation of oil-water mixtures.

When compared to two-dimensional porous materials like fabrics, membranes, and meshes [20−24], three-dimensional porous materials (such as sponges) offer superior performance. These sponges with high porosity and extensive surface area can absorb significant quantities of oil/solvent from oily wastewater while effectively repelling water. Meanwhile, their exceptional elasticity further enhances their suitability for managing large-scale oil spills or oily wastewater [25−27]. Consequently, sponges featuring unique surface wettability and substantial pore volume are increasingly gaining recognition in the realm of oily wastewater treatment. In contrast to other materials, sponges, particularly melamine sponges (MS), exhibit dual hydrophilic and lipophilic properties. They have the advantages such as high porosity, excellent mechanical properties, and robust absorption capabilities. Therefore, they are regarded as a perfect foundation for developing materials that separate oil from water.