Sprayable, durable, and superhydrophobic coating of silica particle brushes based on octadecyl bonding and polymer grafting via surface-initiated ATRP for efficient oil/water separation

Fabrication of a poly(N-isopropylacrylamide)-grafted alginate composite aerogel for efficient treatment of emulsified oily wastewater

The treatment of emulsion wastewater poses significant challenges. In this study, a novel porous material, namely esterified bagasse/poly(N, N-dimethylacrylamide)/sodium alginate (SBS/PDMAA/Alg) aerogel, was developed for efficient demulsification and oil recovery. By grafting a poly(N-isopropylacrylamide) (PNIPAM) brush onto the SBS/PDMAA/Alg skeleton through free radical polymerization, the resulting aerogel exhibits both surface charge and a molecular brush structure. The aerogel demonstrates remarkable demulsification efficiency for cationic surfactant-stabilized emulsions at various concentrations, achieving a demulsification efficiency of 95.6% even at an oil content of 100 g L-1. Furthermore, the molecular brush structure extends the application range of the aerogel, enabling a demulsification efficiency of 98.3% for anionic and non-ionic surfactant-stabilized emulsions. The interpenetrating polymer network (IPN) structure formed by SBS, PDMAA, and alginate enhances the mechanical stability of the aerogel, enabling a demulsification efficiency of 91.3% even after 20 repeated cycles. The demulsification ability of the composite aerogel is attributed to its surface charge, high interfacial activity, and unique brush-like structure. A demulsification mechanism based on the synergistic effect of surface charge and molecular brush is proposed to elucidate the efficient demulsification process.

Magnetically recoverable poly (methyl methacrylate-acrylic acid)/iron oxide magnetic composites nanomaterials with hydrophilic wettability for efficient oil-water separation

Due to the environmental and production problems of emulsion, it is important to efficiently separate oil-water emulsion to meet the refinery requirement and clean up oil spills. Synthesis of a universal demulsifier is not an easy task because the physical properties of crude oil vary, which makes its characterization and demulsification procedure difficult. To overcome this problem, hydrophilic and magnetically recoverable poly (methyl methacrylate-acrylic acid)/iron oxide magnetic composite nanoparticles ((P(MMA-AA)/Fe₃O₄ NPs) were developed as an efficient and economical demulsifier via soap-free emulsion polymerization. To characterize the magnetic composite NPs for their appropriate surface morphology and magnetic domain, TEM, FTIR, VSM, and TGA analyses were carried out. The newly synthesized NPs displayed good hydrophilic properties as they migrated quickly to the aqueous emulsion phase, which was also reassured by their water contact angle of 75°. They exhibit strong magnetic characteristics (20 amu/g) in the oil-water emulsion, makings the hydrophilic wettability capable and attractive to the external magnet. Experimental results revealed that the prepared magnetic composite NPs separated 99% of the water from stable emulsion in 30 min and could be recycled 8 times through magnetic separation. The recycled magnetic composite NPs maintain their hydrophilic wettability and efficiency in separating oil-water emulsion, making them economical and commercially viable. The migration of magnetic composite NPs to the aqueous phase in the stable emulsion with a strong magnetic domain explains the coalescence of emulsified water droplets and their quick separation from the stable emulsions through the external magnet.

Robust multifunctional fluorine-free superhydrophobic fabrics for high-efficiency oil-water separation with ultrahigh flux

The limited robustness and complex preparation process greatly hinder the large-scale use of superhydrophobic surfaces in real life. In this work, we adopt a simple method to prepare robust fluorine-free superhydrophobic cotton fabrics by a facile dip-coating method based on silica microparticles and titanium dioxide nanoparticles. Microparticles and nanoparticles are used to build a suitable rough hierarchical structure, while strong bonds are formed between fabric and particles by a silane coupling agent. The cross-linking reaction between the isocyanate group of trimers of hexamethylene diisocyanate (HDI) and the hydroxyl group of each component in the condensation reaction further increases the bonding between the coating and the cotton fabric. In addition, polydimethylsiloxane (PDMS) is used as a low-surface-energy material to modify the fabric surface. The resulting coating shows excellent superhydrophobic properties with a water contact angle of 161.7°. Meanwhile, the prepared superhydrophobic fabric exhibits excellent durability and stability after sandpaper wearing, washing, and UV radiation, as well as treatment with various organic solutions, boiling water and different pH solutions. Moreover, the superhydrophobic fabric displays excellent UV protection performance and high oil-water separation efficiency (>99% after 30 cycles) with ultrahigh flux up to 20 850 L m^-2 h^-1.