A Review of the Processes Associated with the Removal of Oil in Water Pollution

Adsorption Parameters Optimization of Spent Coffee Ground Biochar for Methylene Blue Removal Using Response Surface Methodology

The disposal of spent coffee grounds (SCG) in landfills is a common practice. However, owing to their unique porous structure, SCGs can be transformed into biochar for use as a cost-effective adsorbent. Methylene blue (MB), a dye employed in textile and printing sectors, poses risks to both aquatic life and human health. To mitigate these effects, efficient treatment of MB prior to environmental release is essential. This research assesses the suitability of spent coffee ground biochar (SCGB) as an adsorbent for MB. The design of experiment (DOE) employed two approaches, classical and response surface optimization, considering adsorbent dosage, solution pH, contact time, temperature, and MB removal percentage as factors. Notably, adsorbent dosage and temperature emerged as critical factors for MB removal, with a well-fitting linear model. The optimum conditions for MB removal by SCGB were 0.99 g adsorbent, 30 min contact time, 30°C, and pH 7. The predicted MB removal was 99.99%, with a desirability of 1.000. The 0.02% discrepancy between predicted and experimental values confirmed the accuracy of the experimental parameter prediction by DOE. SCGB demonstrated robust adsorption capacity, attributed to its carbonaceous and highly porous structure, leading to significantly enhanced MB removal efficiency.

Universal Rapid Demulsification by Vacuum Suction Using Superamphiphilic and Underliquid Superamphiphobic Polyurethane/Diatomite Composites

A process for universal rapid demulsification by vacuum suction using an as-prepared superamphiphilic and underliquid superamphiphobic polyurethane (PU)/diatomite composite has been developed and is used to demulsify kerosene-in-water and water-in-kerosene emulsions with and without a surfactant. The results show that the demulsification rate of all the emulsions exceeds 98.5% in long-term operation, with a stable demulsification speed exceeding 0.303 L/m² min. When a superhydrophobic channel for separation is added, the oil/water separation efficiency exceeds 99.0%, and the final products are qualified oil and water. This attractive universal demulsification capability of PU/diatomite originates from its underliquid superamphiphobicity, which attracts a continuous phase to form a stable liquid film and thus repels dispersed phase droplets, which have a similar interaction with the surface but are much less abundant. The vacuum forces emulsion droplets into the microstructure of the PU/diatomite cake, where they are compressed, coalesce, and finally demulsified. This observed mechanism suggests a promising strategy to avoid the negative effects of oil fouling in demulsification and achieve large-scale universal continuous rapid demulsification.

Fundamentals and utilization of solid/ liquid phase boundary interactions on functional surfaces

The affinity of macroscopic solid surfaces or dispersed nano- and bioparticles towards liquids plays a key role in many areas from fluid transport to interactions of the cells with phase boundaries. Forces between solid interfaces in water become especially important when the surface texture or particles are in the colloidal size range. Although, solid-liquid interactions are still prioritized subjects of materials science and therefore are extensively studied, the related literature still lacks in conclusive approaches, which involve as much information on fundamental aspects as on recent experimental findings related to influencing the wetting and other wetting-related properties and applications of different surfaces. The aim of this review is to fill this gap by shedding light on the mechanism-of-action and design principles of different, state-of-the-art functional macroscopic surfaces, ranging from self-cleaning, photoreactive or antimicrobial coatings to emulsion separation membranes, as these surfaces are gaining distinguished attention during the ongoing global environmental and epidemic crises. As there are increasing numbers of examples for stimulus-responsive surfaces and their interactions with liquids in the literature, as well, this overview also covers different external stimulus-responsive systems, regarding their mechanistic principles and application possibilities.