OBJECTIVE: An innovative strategy for designing high-performance demulsifiers is proposed. It hypothesizes that integrating mesoscopic molecular simulations with macroscopic physicochemical experiments can enhance the understanding and effectiveness of demulsifiers. Specifically, it is suggested that amphiphilic hyperbranched polyethyleneimine (CHPEI) could act as an efficient demulsifier in oil-water systems, with its performance influenced by its adsorption behaviors at the oil-water interface and its ability to disrupt asphaltene-resin aggregates.
METHODS: Several coarse-grained models of oil-water systems, with CHPEI, are constructed using dissipative particle dynamics (DPD) simulation. Following the insights gained from the simulations, a series of CHPEI-based demulsifiers are designed and synthesized. Demulsification experiments are conducted on both simulated and crude oil emulsions, with the process monitored using laser scanning confocal microscopy. Additionally, adsorption kinetics and small angle X-ray scattering are employed to reveal the inherent structural characteristics of CHPEI demulsifiers.
RESULTS: CHPEI demonstrates over 96.7 % demulsification efficiency in high acid-alkali-salt systems and maintains its performance even after multiple reuse cycles. The simulations and macroscopic experiments collectively elucidate that the effectiveness of a demulsifier is largely dependent on its molecular weight and the balance of hydrophilic and hydrophobic groups. These factors are crucial in providing sufficient interfacial active functional groups while avoiding adsorption sites for other surfactants. Collaborative efforts between DPD simulation and macroscopic measurements deepen the understanding of how demulsifiers can improve oil-water separation efficiency in emulsion treatment.

In this study, boron nitride nanotubes (BNNTs) were utilized as covering and reinforcing materials owing to their extraordinary insulation and extremely high hydrophobicity. The gas-liquid-solid annealing process was used to manufacture the BNNT stainless-steel filter, with a 120 mesh stainless steel filter serving as the substrate and B2O3 as the raw material. Scanning electron microscopy showed that the average diameter of the nanotubes was 0.40 μm. The BNNTs were bamboo shaped, and the BNNT stainless-steel filter was superhydrophobic, with a water contact angle was 150.49°. The materials demonstrated good separation performance, as indicated by the separation results obtained under four different test conditions (0 and 0.3 MPa, 3 and 10 mL/min). The solid-liquid separation effect of the BNNT stainless-steel filter was better than that of the Teflon filter. In oil-water separation experiments with varying water contents (1.2 and 5.8 wt%), the BNNT stainless-steel filter was more hydrophobic. Based on the results, the role of the hydrodynamic method in the separation of two superhydrophobic materials is discussed. The method introduced in this study can serve as a reference for the application of other filtration separation technologies. Furthermore, the superior separation performance of the superhydrophobic BNNT stainless-steel filter may enable the quick, effective, and continuous collection of water contaminated with oil, giving it a wide range of potential applications.

With the increase of oily wastewater discharge and the growing demand for clean water supply, high throughput green materials for oil-water separation with anti-pollution and self-cleaning ability are urgently needed. Herein, the polysaccharide-based composite aerogels of CMC/SA@TiO2-MWCNTs (CSTM) with fast photo-driven self-cleaning ability have been prepared by a simple freeze-drying and ionic cross-linking strategy. The introduction of TiO2 /MWCNTs nanocomposites effectively improves the underwater oleophobic and mechanical properties of polysaccharide aerogels and enables their photo-driven self-cleaning ability for efficient oil-water separation and purification of complex oily wastewater. For immiscible oil-water mixtures, a high separation flux of about 7650 L m-2 h-1 and a separation efficiency of up to 99.9 % was obtained. For surfactant-stabilized oil-in-water emulsion, a flux of 3952 L m-2 h-1 was achieved with a separation efficiency of up to 99.3 %. More importantly, the excellent photoluminescent self-cleaning ability and low oil adhesion contribute to the high contamination resistance, excellent reusability, and robust durability of CSTM aerogel. With the advantages of simple preparation, remarkable performance, and recyclability, this aerogel is expected to provide a green, economical, and scalable solution for the purification of oily wastewater.

Fats, oils and grease (FOGs) deposits in sewers have recently become a significant problem, causing financial strain on water companies, damaging sewer lines, and exposing the environment to dirty water through sanitary sewer overflows. Despite the proactive use of grease traps/interceptors for physical oil-water separation, the issue of FOG deposits persists. This study proposes the use of adsorption-based oil-water separation, employing superhydrophobic cotton, as a new alternative method for removing FOGs. Durable superhydrophobic cotton was successfully prepared using a simple two-step sol-gel method, with octadecyltrimethoxysilane (ODTMS) as a modifying silane. The resulting cotton samples demonstrated remarkable superhydrophobicity, evidenced by water contact angle (WCA) above 154°. Additionally, it exhibited exceptional durability and stability when exposed to hot water, harsh acidic and alkaline solutions, as well as during a laundry test. Moreover, the cotton displayed excellent oil-water separation efficiency (> 98 %) and maintained consistent performance throughout 20 reuse cycles, highlighting its high reusability. This approach holds the potential to address the prevailing FOG deposit issues and contribute to more efficient and sustainable wastewater management practices.

In the alkaline-surfactant-polymer flooding emulsion, oil droplets with various sizes exhibited different interfacial properties, resulting in different stabilization and destabilization behaviors. In view of this, it is expected to achieve outstanding oil-water separation efficiency by screening targeted demulsifier for oil droplets with different size ranges (0-1, 1-5 and 5-10 μm). Based on the size effect of oil droplets, a series of multibranched polyether-polyquaternium demulsifiers that integrated different charge neutralization and interfacial displacement functionalities were designed by regulating the cationicity and EO:PO ratios. As a result, the most effective polyether-polyquaternium variant for each size range of oil droplet was screened out. By employing these three selected polyether-polyquaternium variants in a sequential batch demulsification test, the maximum demulsification efficiency of 95.1% was obtained, which was much higher than that using a single polyether-polyquaternium variant (82.5%, 80.5% and 83.8%). The adsorption behaviors of polyether-polyquaternium variants on the oil/water interface were investigated by the molecular dynamics simulation. Moreover, the interfacial properties and oil droplet size variations during the demulsification process were monitored, so as explore the demulsification mechanism. This demulsification protocol based on the size effect of oil droplets with its excellent oil-water separation performance offered significant technical promise for the emulsified oil wastewater disposal.

Photocatalytic membranes integrate membrane separation and photocatalysis to deliver an efficient solution for water purification, while the top priority is to exploit simple, efficient, renewable, and low-cost photocatalytic membrane materials. We herein propose a facile one-stone-two-birds strategy to construct a multifunctional regenerated cellulose composite membrane decorated by Prussian blue analogue (ZnPBA) microspheres for wastewater purification. The hypotheses are that: 1) ZnCl2 not only serves as a cellulose solvent for tuning cellulose dissolution and regeneration, but also functions as a precursor for in-situ growth of spherical-like ZnPBA; 2) More homogeneous reactions including coordination and hydrogen bonding among Zn2+, [Fe(CN)6]3- and cellulose chains contribute to a rapid and uniform anchoring of ZnPBA microspheres on the regenerated cellulose fibrils (RCFs). Consequently, the resultant ZnPBA/RCM features a high loading of ZnPBA (65.3 wt%) and exhibits excellent treatment efficiency and reusability in terms of photocatalytic degradation of tetracycline (TC) (90.3 % removal efficiency and 54.3 % of mineralization), oil-water separation efficiency (>97.8 % for varying oils) and antibacterial performance (99.4 % for E. coli and 99.2 % for S. aureus). This work paves a simple and useful way for exploiting cellulose-based functional materials for efficient wastewater purification.

As the traditional aerogel has defects such as poor mechanical properties, complicated preparation process, high energy consumption and non-renewable, wood aerogel as a new generation of aerogel shows unique advantages. With a natural cellulose framework, wood aerogel is a novel nano-porous material exhibiting exceptional properties such as light weight, high porosity, large specific surface area, and low thermal conductivity. Furthermore, its adaptability to further functionalization enables versatile applications across diverse fields. Driven by the imperative for sustainable development, wood aerogel as a renewable and eco-friendly material, has garnered significant attention from researchers. This review introduces preparation methods of wood aerogel based on the top-down strategy and analyzes the factors influencing their key properties intending to obtain wood aerogels with desirable properties. Avenues for realizing its functionality are also explored, and research progress across various domains are surveyed, including oil-water separation, conductivity and energy storage, as well as photothermal conversion. Finally, potential challenges associated with wood aerogel exploitation and utilization are addressed, alongside discussions on future prospects and research directions. The results emphasize the broad research value and future prospects of wood aerogels, which are poised to drive high-value utilization of wood and foster the development of green multifunctional aerogels.

Conventional oil-water separation membranes are difficult to establish a trade-off between membrane flux and separation efficiency, and often result in serious secondary contamination due to their fouling issue and non-degradability. Herein, a double drying strategy was introduced through a combination of oven-drying and freeze-drying to create a super-wettable and eco-friendly oil-water separating aerogel membrane (TMAdf). Due to the regular nacre-like structures developed in the drying process and the pores formed by freeze-drying, TMAdf aerogel membrane finally develops regularly arranged porous structures. In addition, the aerogel membrane possesses excellent underwater superoleophobicity with a contact angle above 168° and antifouling properties. TMAdf aerogel membrane can effectively separate different kinds of oil-water mixtures and highly emulsified oil-water dispersions under gravity alone, achieving exceptionally high flux (3693 L·m-2·h-1) and efficiency (99 %), while being recyclable. The aerogel membrane also displays stability and universality, making it effective in removing oil droplets from water in corrosive environments such as acids, salts and alkalis. Furthermore, TMAdf aerogel membrane shows long-lasting antibacterial properties (photothermal sterilization up to 6 times) and biodegradability (completely degraded after 50 days in soil). This study presents new ideas and insights for the fabrication of multifunctional membranes for oil-water separation.

The present study aims to combat the problem of oil in water pollution via its separation using a superhydrophobic copper mesh. An ecofriendly superhydrophobic copper mesh with a water contact angle of 166 ± 2° is developed by a facile two-step process (electrodeposition followed by coating). The coated mesh with mechanical robustness, chemical endurance and thermal stability is a promising choice for real-world conditions. Additionally, its resistance to corrosion in harsh chemical environments ensures its long-term durability. With a separation efficiency of 99.9 %, the coated mesh serves as an efficient medium for oil-water separation. It can be used as a reusable filtering medium with high separation efficiency in alkali and neutral environments. Besides, it is also competent for continuous oil-water separation and collection of oil from wastewater. Thus, the above study clearly manifests that the coated mesh holds tremendous potential for large-scale oil spill cleanup.

A novel family of multifunctional nanomaterials called MXenes is quickly evolving, and it has potential applications that are comparable to those of graphene. This article provides a current explanation of the design and performance assessment of MXene-based membranes. The production of MXenes nanosheets are first described, with an emphasis on exfoliation, dispersion stability, and processability, which are essential elements for membrane construction. Further, critical discussion is also given to MXenes potential applications in Vacuum assisted filtration, casting method, Hot press method, electrospinning and electrochemical deposition and layer-by-layer assembly for the creation of MXene and MXene derived nanocomposite membranes. Additionally, the discussion is carried forward to give an insight to the modification methods for the construction of MXene-based membrane are described in the literature, including pure or intercalated nanomaterials, surface modifiers and miscellaneous two-dimensional nanomaterials. Furthermore, the review article highlights the potential utilization of MXene and MXene based membranes in separation and purification processes including removal of small organic molecules, heavy metals, oil-water separation and desalination. Finally, the perspective use of MXenes strong catalytic activity and electrical conductivity for specialized applications that are difficult for other nanomaterials to accomplish are discussed in conclusion and future prospectus section of the manuscript. Overall, important information is given to help the communities of materials science and membranes to better understand the potential of MXenes for creating cutting-edge separation and purification membranes.