Preparation of cellulose-coated cotton fabric and its application for the separation of emulsified oil in water

Superhydrophilic and Underwater Superoleophobic Copper Mesh Coated with Bamboo Cellulose Hydrogel for Efficient Oil/Water Separation

Super-wetting interface materials have shown great potential for applications in oil-water separation. Hydrogel-based materials, in particular, have been extensively studied for separating water from oily wastewater due to their unique hydrophilicity and excellent anti-oil effect. In this study, a superhydrophilic and underwater superoleophobic bamboo cellulose hydrogel-coated mesh was fabricated using a feasible and eco-friendly dip-coating method. The process involved dissolving bamboo cellulose in a green alkaline/urea aqueous solvent system, followed by regeneration in ethanol solvent, without the addition of surface modifiers. The resulting membrane exhibited excellent special wettability, with superhydrophilicity and underwater superoleophobicity, enabling oil-water separation through a gravity-driven "water-removing" mode. The super-wetting composite membrane demonstrated a high separation efficiency of higher than 98% and a permeate flux of up to 9168 L·m-2·h-1 for numerous oil/water mixtures. It also maintained a separation efficiency of >95% even after 10 cycles of separation, indicating its long-term stability. This study presents a green, simple, cost-effective, and environmentally friendly approach for fabricating superhydrophilic surfaces to achieve oil-water separation. It also highlights the potential of bamboo-based materials in the field of oil-water separation.

Amine-functionalized cotton for the treatment of oily wastewater

Common commercial demulsifiers are typically made from ethylene oxide and propylene oxide. The production process is dangerous and complex, with poor adaptability and high cost. In this work, cotton modified with polyethylene polyamine was utilized as a demulsifier for the treatment of oily wastewater. The chemical structure and morphology of the as-prepared sample (CPN) were characterized by IR spectrum and SEM. The effect of CPN dosage, pH value, and salinity on the demulsification performance of oily wastewater was explored through the bottle tests. The results showed that the light transmittance of separated water was 81.7% and the corresponding deoiling rate was 98.5% when a CPN dosage of 25 mg/L was used at room temperature for 30 min. The interfacial properties were also systematically investigated, and the results indicated that CPN had better interfacial activity and a stronger reduction capability of interfacial tension compared to asphaltenes. The finding initiated and accelerated the demulsification process of oily wastewater. Based on the outstanding performance of this biomass-derived demulsifier, it shows promising potential for application in the treatment of oily wastewater.

Environmental-friendly regenerated lignocellulose functionalized cotton fabric to prepare multi-functional degradable membrane for efficient oil-water separation and solar seawater desalination

Freshwater pollution and shortage have become an imminent problem. Therefore, it is necessary to develop a multi-functional membrane for the production of fresh water. In this work, the regenerated lignocellulose modified cotton fabric was developed as a novel, multi-functional and degradable membrane (LCPT@CF) for efficient oil-water separation and solar steam generation for the first time. The fabrication method has the merits of simple, environmentally friendly and cost effective. The regenerated lignocellulose was adhered on the surface of cotton fabric by tannic acid and polyvinyl alcohol complexes tightly, and the multilayered structures of the LCPT@CF can be formed, which endowed the membranes with underwater superoleophobic property and durability. The underwater superoleophobic property enabled LCPT@CF to purify various kinds of oil-in-water emulsions with a separation efficiency of more than 99.90%. Moreover, benefiting from the excellent photothermal conversion capacity of regenerated lignocellulose, the LCPT@CF achieved high evaporation rate of 1.39 kg m^-2 h^-1 and favorable evaporation efficiency of 84% under 1 sun illumination, and the LCPT@CF also presented excellent salt-resistance for evaporating seawater for 20 cycles, without salt accumulation. More importantly, the LCPT@CF could be naturally degradable by microorganisms in the natural condition within 3 months, which had outstanding environmental friendliness. These above results demonstrated that the green and efficient LCPT@CF could play great potential in oil-water separation and sewage purification.

Recent advances in eco-friendly fabrics with special wettability for oil/water separation

Considering the serious damage to aquatic ecosystems and marine life caused by oil spills and oily wastewater discharge, efficient, environment-friendly and sustainable oil/water separation technology has become an inevitable trend for current development. Herein, fabrics are recognized as eco-friendly materials for water treatment due to their good degradability and low cost. Particularly, fabrics with rough structures and natural hydrophilicity/oleophilicity enable the construction of superwetting surfaces for the selective separation of oil/water mixtures and even complex emulsions. Therefore, superwetting fabrics for efficiently solving oil spills and purifying oily wastewater have received extensive attention. Especially, Janus and smart fabrics are highly anticipated to enable the on-demand and sustainable treatment of oil spills and oily wastewater due to their changeable wettability. Moreover, the fabrication of superwetting fabrics with multifunctional performances for oily wastewater purification can further promote their practical industrial applications, such as photocatalytic, self-cleaning, and self-healing characteristics. However, some potential challenges still exist, which urgently need to be systematically summarized to guide the future development of this research field. In this review, firstly, the fundamental theories of wettability and the separation mechanisms based on special wettability are discussed. Then, superwetting fabrics for efficient oil/water separation are systematically reviewed, such as superhydrophobic/superoleophilic (SHB/SOL), superhydrophilic/superoleophobic (SHL/SOB), SHL/underwater superoleophobic (SHL/UWSOB), and UWSOB/underoil superoleophobic (UWSOB/UOSHB) fabrics. Most importantly, we highlight Janus, smart, and multifunctional fabrics based on their superwetting property. Correspondingly, the advantages and disadvantages of each superwetting fabric are comprehensively analyzed. Besides, super-antiwetting fabrics with superhydrophobic/superoleophobic (SHB/SOB) property are also introduced. Finally, the challenges and future research directions are explained.

Recyclable amine-functionalized carbon nanotubes for the separation of oily wastewater

In this work, a CNTs-NH₂ demulsifier was prepared by grafting ethylenediamine on the surface of carbon nanotubes to break oily wastewater. The physicochemical and interfacial properties of CNTs-NH₂ were characterized and analyzed. It showed that CNTs-NH₂ had an eminent amphipathicity and high interfacial activity, which allows it to sharply migrates to the interface and effectively interacts with interfacial film by the combined action of π-π interaction and electrostatic attraction. The demulsification tests exhibited that CNTs-NH₂ could effectively remove emulsified oil from the oily wastewater. It could be used at acidic and neutral conditions, and high salinity. Moreover, it could be recycled and still maintained its interfacial activity, thusly vastly enhancing the application scope. The light transmittance was up to 88.1% and the corresponding oil removal rate was 99.2% with 100 mg/L of CNTs-NH₂ for 30 min. The oil removal rate of CNTs-NH₂ remained above 97.8% after 6 cycles. This work provides a deep understanding on the design of demulsifier and its demulsification mechanism.

Functionalization of cellulose fibers alongside growth of 2D LDH platelets through urea hydrolysis inspired Taro wettability

Here, Cotton fabric was functionalized via hybrid coating including 2D MgAl LDH (layered double hydroxide) and SA (stearic acid). The urea hydrolysis was employed for construction of vertically aligned LDH on surface of cellulose fibers under hydrothermal condition. The in situ formation mechanism of LDH on cotton surface was nucleation, growth, and interaction with activated cellulose chains. The partial cellulose ionization in the alkaline solution led to nucleophilic behavior towards electron deficient atom. The effect of different ageing, synthesis temperature, and amount of SA were investigated and optimized at 100 °C for 24 h with 0.05 M. The superhydrophobic surface architecture of treated cotton with hierarchical micro/nanostructure was inspired from the Taro leaf structure with continuous contact line presented WCA of 154 ° and CAH of 9 °. The Cotton@LDH@SA exhibited efficient oil/water separation after several washes (>90%) with good stain resistant. Also, the physico-mechanical properties were studied.

Current Status of Cellulosic and Nanocellulosic Materials for Oil Spill Cleanup

Recent developments in the application of lignocellulosic materials for oil spill removal are discussed in this review article. The types of lignocellulosic substrate material and their different chemical and physical modification strategies and basic preparation techniques are presented. The morphological features and the related separation mechanisms of the materials are summarized. The material types were classified into 3D-materials such as hydrophobic and oleophobic sponges and aerogels, or 2D-materials such as membranes, fabrics, films, and meshes. It was found that, particularly for 3D-materials, there is a clear correlation between the material properties, mainly porosity and density, and their absorption performance. Furthermore, it was shown that nanocellulosic precursors are not exclusively suitable to achieve competitive porosity and therefore absorption performance, but also bulk cellulose materials. This finding could lead to developments in cost- and energy-efficient production processes of future lignocellulosic oil spillage removal materials.

Preparation of a rice straw-based green separation layer for efficient and persistent oil-in-water emulsion separation

Inefficiency, high cost, and complex operation have emerged as shackles for large-scale separate oil-in-water emulsion. Herein, a low-cost and eco-friendly separation layer with a rough structure and rich anionic groups was fabricated from rice straw (RS) via a simple acid-base treatment and slight squeeze process. The separation layer's morphology, composition, and wettability were investigated. It was then employed to separate oil-in-water emulsion. The RS after acid and alkali treatment (A₁A₂-RS) exhibited a clear fiber structure and abundant humps, which made the separation layer superwettable and highly electronegative (-26.55 mV). The overlapped and intertwined A₁A₂-RS layer structure owned a superior performance for hexadecyl-trimethyl-ammonium-bromide (CTAB) adsorption and tiny oil interception. As a result, the separation layer had stable fluxes (>500 LMH) for multiple CTAB-stabilized emulsions and the obtained filtrates performed low total organic carbon (TOC) contents (<30 mg/L). In addition, the A₁A₂-RS layer had excellent renewability (10 cycles/ 200 mL) and the flux could be substantially recovered merely by aqueous wash. Moreover, filtrate analysis showed that the A₁A₂-RS layer had a good effect on actual emulsion treatment with a TOC removal rate of 89.56%.

Cellulose-based special wetting materials for oil/water separation: A review

Oil spill accidents and oily wastewater discharged by petrochemical industries have severely wasted water resources and damaged the environment. The use of special wetting materials to separate oil and water is efficient and environment-friendly. Cellulose is the most abundant renewable resource and has natural advantages in removing pollutants from oily wastewater. The application and modification of cellulose as special wetting materials have attracted considerable research attention. Therefore, we summarized cellulose-based superlipophilic/superhydrophobic and superhydrophilic/superoleophobic materials exhibiting special wetting properties for oil/water separation. The treatment mechanism, preparation technology, treatment effect, and representative projects of oil-bearing wastewater are discussed. Moreover, cellulose-based intelligent-responsive materials for application to oil/water separation and the removal of other pollutants from oily wastewater have also been summarized. The prospects and potential challenges of all the materials have been highlighted.

Durable, magnetic-responsive melamine sponge composite for high efficiency,in situoil-water separation

The development of durable and high-performance absorbents forin situoil-water separation is of critical importance for addressing severe water pollution in daily life as well as for solving accidental large-scale oil spillages. Herein, we demonstrate a simple and scalable approach to fabricate magnetic-responsive superhydrophobic melamine sponges byin situdeposition of PDA coatings and Fe₃O₄nanoparticles, followed by surface silanization with low surface energy 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PTOS) layer. The prepared melamine sponge composite (PTOS-Fe₃O₄@PDA/MF) not only exhibits a very high water contact angle of 165 ± 1.5° and an excellent ability to uptake a variety of oils and organic solvents (e.g. up to 141.1 g/g for chloroform), but also shows robust durability and superior recyclability. The PTOS-Fe₃O₄@PDA/MF sponge can also efficiently separate oils (or organic solvents) and water, as demonstrated by different model systems including immiscible oil-water solution mixture and miscible water-oil (W/O) emulsion (stabilized by surfactants). Furthermore, the PTOS-Fe₃O₄@PDA/MF sponge is able toin siturecover organics from water using a peristaltic pump, which gives it significant advantages over other traditional batch processes for oil-water separation. We believe that the PTOS-Fe₃O₄@PDA/MF sponge provides a very promising material solution to address oil-water separation, especially for the large-scale problems that have been long-time challenges with conventional sorption methods.