Superhydrophobic aerogel blanket with magnetic and solar heating effect enables efficient continuous cleanup of highly viscous crude oil

Biomimetic materials for efficient emulsion separation: Based on the perspective of energy

Purifying emulsified oily wastewater is particularly crucial for solving environmental pollution and water scarcity. Membrane separation shows great potential for emulsified wastewater treatment. However, realizing continued effective emulsion separation remains a significant challenge. Fortunately, various kinds of creative schemes have been proposed to overcome the current dilemma. In this paper, biomimetic emulsion separation materials with unique wettability are introduced. Besides, This article summarizes the recently advanced emulsion separation strategies. First, we analyze the typical wettability theory and explore the trade-off between separation flux and efficiency. After that, based on emulsion types, the current common emulsion separation materials are summarized and analyzed. Notably, the integration of natural biological inspiration has made separation materials full of potential. Further, from the perspective of external energy input or no-external energy input, this article provides an overview of advanced emulsion separation materials and analyzes the potential separation mechanism. Encouragingly, efficient emulsion separation can be realized by membrane characteristics (microstructure, superwettability, electrostatic interaction) or the appropriate external stimulus (photo, electricity, magnetic). Finally, the challenges and trends are summarized. We hope that this article will provide inspiration for the advancement of novel generations of separation materials.

Hydrophobic Pedicularis Kansuensis/graphene aerogel with solar thermal effect enables efficient removal of sulfadiazine and oil from water

The contamination of water resources by organic pollutants is a significant factor contributing to the scarcity of water resources. Furthermore, the various forms and quantities of organic pollutants present a considerable challenge to their management and remediation. Antibiotics and oil are two typical organic pollutants in water, which have a serious impact on the environment and biological health. It is thus imperative to eradicate these two principal pollutants from the aquatic environment. The remediation of polluted water by adsorption represents an effective approach, with the adsorbent's performance determining the process's efficacy. In this study, Pedicularis Kansuensis/graphene aerogel (PKGA) was prepared, and its adsorption performance of sulfadiazine (SDZ) with low concentration and oil with high concentration was investigated. The results demonstrated that PKGA has good adsorption and removal ability for both SDZ and oil in water. The porous structure, hydrophobicity, and oleophilicity of PKGA facilitate the effective elimination of organic contaminants from aqueous media. The adsorption of SDZ by PKGA is an endothermic spontaneous process. The equilibrium adsorption of SDZ by PKGA increased with increasing temperature and the theoretical maximum equilibrium adsorption at 35 °C was 70.67 mg/g. Additionally, the adsorption capacity of PKGA for oil ranged from 51.27 to 120.71 g/g, indicating its potential for oil-water separation. Notably, PKGA, a representative carbon-based material, exhibits a photothermal effect that enhances its adsorption capabilities for removing SDZ and viscous oil from water. This study offers a novel perspective on organic pollutant adsorption and removal in water.

A heterogeneous polyurethane hybrid foam with enhanced demulsification and dynamic oil cleaning for continuous emulsion separation

Here, a top-down strategy was presented to fabricate a heterogeneous polyurethane hybrid foam with independent oil-absorbing frameworks and uninterrupted water transport channels for continuous emulsion separation. A commercial polyurethane foam (PUF) was hydrophobically modified to develop oil-absorbing frameworks (HPUF). Superhydrophilic carbon nanotubes/cellulose nanofibers (CNTs/CNFs) aerogels were assembled in the voids of the HPUF to establish independent water transport channels, forming a heterogeneous polyurethane hybrid foam (CHPUF). This design endowed the CHPUF with a heterogeneous wetting structure formed by the hydrophobic HPUF and the hydrophilic CNTs/CNFs aerogels, which allowed it to exhibit super hydrophilicity and underwater oil-absorbing properties. The underwater oil-absorbing properties can promote the dynamic cleaning of oil contamination at the separation interface to improve the continuity of emulsion separation. Meanwhile, the heterogeneous wetting structure of the CHPUF and photothermal-induced effect of CNTs synergistically enhanced their demulsification capability. Leveraging these structural and functional attributes, the CHPUF have demonstrated exceptional potential in continuous emulsion separation, demonstrating a robust separation capacity with a single separation volume surpassing 3000 mL and remarkable recyclability, evidenced by over five stable separation cycles each maintaining the separation efficiency of 98 %. The CHPUF have exhibited promising separation suitability for multiple surfactant-stabilized oil-in-water emulsions, achieving over 800 L·m-2·h-1and 99 % of separation flux and efficiency, respectively. Consequently, the CHPUF with dynamic oil cleaning and enhanced demulsification display great potential for treating oily wastewater, while inspiring the development of novel 3D superwetting materials, propelling their application in environmental remediation.

Recent advances in functional micro/nanomaterials for removal of crude oil via thermal effects

Crude oil is one of the most widely used energy and industrial raw materials that is crucial to the world economy, and is used to produce various petroleum products. However, crude oil often spills during extraction, transportation and use, causing negative impacts on the environment. Thus, there is a high demand for products to remediate leaked crude oil. Among them, oleophilic and hydrophobic adsorbents can absorb crude oil through thermal effects and are research hotspots. In this review, we first present an overview of wettability theory, the heating principles of various thermal effects, and the theory of reducing crude oil viscosity by heating. Then we discuss adsorbents based on different heating methods including the photothermal effect, Joule heating effect, alternating magnetic field heating effect, and composite heating effect. Preparation methods and oil adsorption performance of adsorbents are summarized. Finally, the advantages and disadvantages of various heating methods are briefly summarized, as well as the prospects for future research.

TDA/rGO@WS with Joule heat and photothermal synergistic effect: A promising adsorption material for all-weather recovery of viscous oil spills at sea

Oil spills are a global environmental protection challenge, and traditional adsorption materials have poor effect on low temperature and high viscosity marine oil spills. This article reports composite adsorption materials TDA/rGO@WS for viscous oil spills: loaded with rGO/TDA coating on a commercial biomass wood pulp sponge (WS), achieving Joule heating, photothermal effect and hydrophobic modification. The results showed that the TDA/rGO@WS has good photothermal conversion ability and Joule heating ability, and the temperature increased to 83.7 °C and 148 °C, respectively, under simulated solar irradiation and additional voltage at room temperature. The efficiency of adsorption at a low temperature of 5 °C increased by 22.41% at 1 sun and by 51.53% at 10 V. Temperature effectively reduced the viscosity of the offshore oil spill and ensures the efficient adsorption of oil spills at low temperatures promoted. The TDA/rGO@WS also showed good hydrophobicity (WCA=129°), excellent efficiency of water-oil separation (99.53%) and good adsorption capacity (9.4-13.68 g/g) for marine fuel oils. TDA/rGO@WS effectively solves the problem of cleaning up high-viscosity oil spills from ships in winter and polar waters, and proposes a new strategy for all-weather efficient treatment of oil spills at sea.

Cellulose nanofiber/MXene/luffa aerogel for all-weather and high-efficiency cleanup of crude oil spills

The remediation of heavy crude oil spills is a global challenge because frequent crude oil spills cause long-term damage to local living beings and marine ecosystems. Herein, a solar-driven and Joule-driven self-heated aerogel were developed as an all-weather adsorbent to efficiently absorb crude oil by obviously decreasing the viscosity of crude oil. The cellulose nanofiber (CNF)/MXene/luffa (CML) aerogel was fabricated via a simple freeze-drying method using CNF, MXene, and luffa as raw materials, and then coated with a layer of polydimethylsiloxane (PDMS) to make it hydrophobic and further increase oil-water selectivity. The aerogel can quickly reach 98 °C under 1 sun (1.0 kW/m²), which remains saturated temperature after 5 times photothermal heating/cooling cycles, indicating that the aerogel has great photothermal conversation capability and stability. Meanwhile, the aerogel can also rapidly rise to 110.8 °C with a voltage of 12 V. More importantly, the aerogel achieved the highest temperature of 87.2 °C under outdoor natural sunlight, providing a possibility for promising applications in practical situations. The remarkable heating capability enables the aerogel to decrease the viscosity of crude oil substantially and increase the absorption rate of crude oil by the physical capillary action. The proposed all-weather aerogel design provides a sustainable and promising solution for cleaning up crude oil spills.

Efficient oily wastewater treatment by a novel electroflotation-membrane separation system consisting a Ni-Cu-P membrane prepared by electroless nickel plating

Electroflotation-membrane separation system with a conductive membrane has recently emerged as a promising technology for oily wastewater treatment. However, the conductive membrane prepared by electroless plating often suffers the problems of low stability and high activation cost. To solve these problems, this work proposed a new strategy regarding surface metallization of polymeric membrane by surface nickel-catalyzed electroless nickel plating of nickel‑copper‑phosphorus alloys for the first time. It was found that, addition of copper source remarkably enhanced the membranes' hydrophilicity, corrosion resistance and fouling resistance. The Ni-Cu-P membrane had an underwater oil contact angle of up to 140°, and simultaneously possessed rejection rate > 98 % with rather high flux of 65,663.0 L·m^-2·h^-1 and excellent cycling stability when separating n-hexane/water mixtures under gravity drive. The permeability is higher than the state-of-the-art membranes for oil/water separation. The Ni-Cu-P membrane as the cathode can be assembled into an electroflotation-membrane separation system, allowing to separate oil-in-water emulsion with 99 % rejection. Meanwhile, the applied electric field significantly improved membrane flux and fouling resistance (flux recovery up to 91 %) when separate kaolin suspensions. Polarization curve and Nyquist curve analysis further confirmed that addition of Cu element obviously enhanced corrosion resistance of the Ni modified membrane. This work provided a novel strategy to make up high-efficiency membranes for oily wastewater treatment.