Preparation and mechanism of hydrophobic modified diatomite coatings for oil-water separation

It remains a significant challenge to separate oil and water in the metallurgical industry. Therefore, there is an urgent need for a low-cost process to prepare hydrophobic and lipophilic materials in order to improve oil-water separation performance. The hydroxyl group on the surface of diatomite was modified by a polysiloxane reaction. The microstructure, chemical composition, and hydrophobicity before and after modification were studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Diatomite@POS/EP coating was prepared using the spraying suspension method, to endow various materials with excellent hydrophobic properties (ceramic, sponge, stainless steel, paper, and gauze). The SEM results show that many spherical particles were stacked on the modified diatomite disk, and new elements and structures were observed. The Diatomite@POS floated on the water indicates that the modification was successful. The contact angle between coating on porous diatomite ceramics and water could reach 147.5 when the mass ratio of Diatomite@POS: EP was 7:5. After 0-1000 cm wear test, and soaked in acid and alkali solution for 4 h, the coating could keep hydrophobicity, indicating that it features excellent wear resistance, acid, and alkali resistance. Ceramic sprayed with Diatomite@POS/EP and melamine sponges soaked in Diatomite@POS/EP were capable of effectively separating vacuum pump oil from water, which showed the promising self-cleaning performance of the ceramic surface. Besides, modified diatomite powder had great potential for application in waterproofing, self-cleaning, oil-water separation, and other fields.