A novel Janus sponge fabricated by a green strategy for simultaneous separation of oil/water emulsions and dye contaminants

Improving multifunctional properties of the polyvinylidene fluoride (PVDF) membrane with crosslinked dialdehyde-starch (DAS) and polyethyleneimine (PEI) coating

Dialdehyde-soluble starch (DAS) and polyethyleneimine (PEI) were used to coat the polyvinylidene fluoride (PVDF) membrane for improving its antifouling and multifunctional properties through a combination of dip-coating and spray-coating techniques. The resulting membrane demonstrated excellent hydrophilicity and underwater oleophobicity due to hydrophilic DAS and PEI on its surface. The membrane achieved an impressive oil removal rate of 99.8 % and a flux 1420.8 ± 26.5 L·m-2·h-1 when it was used for oil-water emulsion separation. The hydration layer formed by the DAS and PEI greatly enhanced the membrane antifouling property, and its flux recovery rate was up to 96.6 % in BSA filtration experiments. The positive charge PEI and the negative charge DAS contributed to high separation efficiency of 99.1 % for the anion dye MO with the membrane D10P20, and high separation efficiency of 88.3 % for the cation dye RhB with the membrane P5D20. In addition, the coating layer was stable due to the cross-linked DAS and PEI. This research contributes greatly to the preparation of antifouling and multifunctional membrane using environmentally friendly material including polysaccharide derivatives and water soluble polymer.

Biomass-activated carbon-based superhydrophobic sponge with photothermal properties for adsorptive separation of waste oil

The increasing discharge of oily wastewater from life poses a serious threat to the ecological environment and human health. To develop green, efficient, and low-cost materials for oil-water separation, a superhydrophobic photothermal oil-absorbing sponge (CAC-PDA@MF) was prepared by using nanoscale coconut shell activated carbon (CAC) loaded on a melamine sponge in this study. The sponge had excellent superhydrophobicity (WCA of 159.53°) due to the reduction of surface energy by grafting long-chain silanes. The adsorption capacity of the sponge was 69.04 g/g-158.27 g/g for a wide range of oils and organic solvents, and the sponge had excellent mechanical properties for multiple adsorption and recovery of oil. After 50 cycles of oil-water separation, its separation efficiency was maintained at over 98 %. In addition, the material had high acid, alkali, and salt resistance as well as excellent photothermal conversion properties. Its surface temperature rose rapidly to 100 °C and above, at a light intensity of 1.0 kW/m2. The material was capable of adsorbing and recovering high-viscosity oils that were solid or semi-solid at room temperature. Its versatility and commercial value made it a promising candidate for a wide range of applications.

Robust nanoparticles growth in the interior of porous sponges for efficient dye adsorption and emulsion separation

Emulsified oils and dye contaminants already pose a huge threat to global ecosystems and human health. It is a significant research topic to develop efficient, rapid, versatile methods for emulsion separation and dye adsorption. The membrane material modified with common methods only modified the outer surface of the membrane, while the interior is hardly fully decorated. In this investigation, a solvent exchange method was used to in situ grow nanoparticles in the interior of a porous sponge. These nanoparticles were obtained with polyethyleneimine, gallic acid, and tannic acid via Michael addition and Schiff base reaction. The prepared nanoparticle-coated sponges provided efficient separation of dyes, emulsions, and complex contaminants. The separation efficiency of the dye reached 99.49%, and the separation efficiency of the emulsion was as high as 99.87% with a flux of 11140.3 L m-2 h-1. Furthermore, the maximum adsorption capacity reached 486.8 mg g-1 for cationic dyes and 182.1 mg g-1 for anionic dyes. More importantly, the nanoparticles were highly robust on the surface of the porous sponge, and the modified sponge could have long-term applications in hazardous environments. Overall, it is envisioned that the nanoparticles-modified porous sponge exhibited considerable potential for emulsion and dye wastewater treatment.

Adsorption of Cu (II) and Zn (II) in aqueous solution by modified bamboo charcoal

Due to the development of industries such as mining, smelting, industrial electroplating, tanning, and mechanical manufacturing, heavy metals were discharged into water bodies seriously affecting water quality. Bamboo charcoal, as an environmentally friendly new adsorbent material, in this paper, the virgin bamboo charcoal (denoted as WBC) was modified with different concentrations of KMnO4 and NaOH to obtain KMnO4-modified bamboo charcoal (KBC) and NaOH-modified bamboo charcoal (NBC) which was used to disposed of water bodies containing Cu2+ and Zn2+. The main conclusions were as following: The adsorption of Cu2+ by WBC, KBC and NBC was significantly affected by pH value, and the optimum pH was 5.0. Differently, the acidity and alkalinity of the solution doesn't effect the adsorption of Zn2+ seriousely. Meanwhile, surface diffusion and pore diffusion jointly determine the adsorption rate of Cu2+ and Zn2+. The test result of EDS showed that Mn-O groups formed on the surface of K6 (WBC treated by 0.06 mol/L KMnO4) can promote the adsorption of Cu2+ and Zn2+ at a great degree. The O content on N6(WBC treated by 6 mol/L NaOH) surface increased by 30.95% compared with WBC. It is speculated that the increase of carbonyl group on the surface of NBC is one of the reasons for the improvement of Cu2+ and Zn2+ adsorption capacity. Finally, the residual concentrations of Cu2+ and Zn2+ in wastewater are much lower than 0.5 mg/L and 1.0 mg/L, respectively. Thus it can be seen, KBC and NBC could be a promising adsorbent for heavy metals.

Activated carbon fibers functionalized with superhydrophilic coated pDA/TiO2/SiO2 with photoluminescent self-cleaning properties for efficient oil-water separation

The adhesion of high-viscosity oil contamination poses limitations on three-dimensional (3D) materials' practical use in treating oilfield-produced water (OPW). In this study, we developed a hybrid pDA/TiO2/SiO2 coating (PTS) on the surface of hydrophilic activated carbon (ACF1) through a combination of dopamine (DA) polymerization, ethyl orthosilicate (TEOS) hydrolysis, and the condensation of TiO2 nanoparticles (NPs) with SiO2 NPs. This coating was designed for gravity-based oil-water separation. The inherent porosity and generous pore size of ACF1-PTS conferred it an ultra-high permeation flux (pure water flux of 3.72 × 105 L∙m-2∙h-1), allowing it to effectively separate simulated oil-water mixtures and oil-water emulsions while maintaining exceptional permeation flux and oil rejection efficiency. When compared to cleaning methods involving ethanol aqueous solutions and NaClO, ultraviolet (UV) illumination cleaning proved superior, enabling oil-contaminated ACF1-PTS to exhibit remarkable flux recovery efficiency and oil-removal capabilities during cyclic separation of actual OPW. Furthermore, the ACF1-PTS material demonstrated impressive stability and durability when exposed to acidic environments (acid, alkali, and salt), robust hydraulic washout conditions, and 25-cycle tests. This study offers valuable insights and research avenues for the development of highly efficient and environmentally friendly 3D oil-water separation materials for the actual treatment of OPW.

Highly elastic photothermal nanofibrillated cellulose aerogels for solar-assisted efficient cleanup of viscous oil spill

Frequent oil spills and illegal industrial pollutant discharge cause ecological and resource damages, so it is necessary to establish efficient adsorption and recovery strategies for oils in wastewater. Herein, inspired by solar-driven viscosity-breaking, we propose a facile approach to fabricate multifunctional nanofibrillated cellulose-based aerogel with high elasticity, excellent photothermal conversion, efficient selective oil adsorption and antibacterial properties. Firstly, copper sulfide (CuS) nanoparticles were in situ deposited on the template of oxidative nanofibrillated cellulose (ONC), aiming at achieving efficient photothermal effect and antibacterial properties. Ethylene glycol diglycidyl ether (EGDE) was employed to establish multiple crosslinking network between CuS@ONC and polyethyleneimine (PEI). A thin hydrophobic PMTS layer deposited on the surface of aerogel via a facile gas-solid reaction ensured stable oil selectivity. The resulting composite aerogel can rapidly adsorb oil under solar self-heating, significantly reducing the adsorption time from 25 to 5 min. Furthermore, it exhibits excellent adsorption capacities for various oils, retaining over 92 % of its initial capacity even after 20 adsorption-desorption cycles, and the antibacterial properties extend its lifespan. This work offers a promising method for constructing multifunctional aerogels for efficient oil-water separation, especially beneficial for high-viscosity and high-melting-point oil cleanup.

Degradation of sulfamethoxazole by super-hydrophilic MoS2 sponge co-catalytic Fenton: Enhancing Fe2+/Fe3+ cycle and mass transfer

To promote the cycle of Fe²⁺/Fe³⁺ in co-catalytic Fenton and enhance mass transfer in an external circulation sequencing batch packed bed reactor (ECSPBR), super-hydrophilicity MoS₂ sponge (TMS) modified by tungstosilicic acid (TA) was prepared for efficiently degrading sulfamethoxazole (SMX) antibiotics in aqueous solution. The influence of hydrophilicity of co-catalyst on co-catalytic Fenton and the advantages of ECSPBR were systematically studied through comparative research methods. The results showed that the super hydrophilicity increased the contact between Fe²⁺ and Fe³⁺ with TMS, then accelerated Fe²⁺/Fe³⁺ cycle. The max Fe²⁺/Fe³⁺ ratio of TMS co-catalytic Fenton (TMS/Fe²⁺/H₂O₂) was 1.7 times that of hydrophobic MoS₂ sponge (CMS) co-catalytic Fenton. SMX degradation efficiency could reach over 90% under suitable conditions. The structure of TMS remained unchanged during the process, and the max dissolved concentration of Mo was lower than 0.06 mg/L. Additionally, the catalytic activity of TMS could be restored by a simple re-impregnation. The external circulation of the reactor was conducive to improving the mass transfer and the utilization rate of Fe²⁺ and H₂O₂ during the process. This study offered new insights to prepare a recyclable and hydrophilic co-catalyst and develop an efficient co-catalytic Fenton reactor for organic wastewater treatment.

Bimodal Antimicrobial Surfaces of Phytic Acid-Prussian Blue Nanoparticles-Cationic Polymer Networks

Surface modification plays a pivotal role in tailoring the functionalities of a solid material. Introduction of antimicrobial function on material surfaces can provide additional protection against life-threatening bacterial infections. Herein, a simple and universal surface modification method based on surface adhesion and electrostatic interaction of phytic acid (PA) is developed. PA is first functionalized with Prussian blue nanoparticles (PB NPs) via metal chelation and then conjugates with cationic polymers (CPs) through electrostatic interaction. With the aid of surface adherent PA and gravitation effect, the as-formed PA-PB-CP network aggregates are deposited on the solid materials in a substrate-independent manner. Synergistic bactericidal effects of "contact-killing" induced by the CPs and localized photothermal effect caused by the PB NPs endow the substrates with strong antibacterial performance. Membrane integrity, enzymatic activity, and metabolism function of the bacteria are disturbed in contact with the PA-PB-CP coating under near-infrared (NIR) irradiation. The PA-PB-CP modified biomedical implant surfaces exhibit good biocompatibility and synergistic antibacterial effect under NIR irradiation, and eliminate the adhered bacteria both in vitro and in vivo.

Catalytic metal-organic framework-melamine foam composite as an efficient material for the elimination of organic pollutants

Water-insoluble organic pollutants in environment, such as sea oil spill, industrial reagents, and the abused organic pesticides, bring great risks to global water systems, which thus requires effective approaches for organic pollutant elimination. In this study, we report a catalytic metal-organic framework (MOF)-melamine foam (MF) composite material (DDT-UiO-66-NH₂@MF) showing excellent oil-water separation performance and enzyme-like degradation ability toward organophosphorus pesticides. The fabrication of DDT-UiO-66-NH₂@MF is based on the immobilization of a MOF-derived nanozyme (UiO-66-NH₂) on MF sponge, and followed by the hydrophobic modification of UiO-66-NH₂ by 1-dodecanethiol (DDT). The obtained DDT-UiO-66-NH₂@MF thus displayed superhydrophobic/superhydrophilic property with a high water contact angle (WCA = 144.6°) and specific adsorption capacity toward various oils/organic solvents (62.2-119.8 g/g), which leads to a continuous oil-water separation on a simple device. In the meanwhile, owing to the enzyme-like property of UiO-66-NH₂, DDT-UiO-66-NH₂@MF also displayed good ability to hydrolyze paraoxon under mild conditions, which facilitates the elimination of toxic pesticide residuals in water systems. This work provides a simple, efficient, and green approach for the separation and treatment of water-insoluble organic pollutants, as well as expands the use of MOFs-MF sponge composite materials in environmental sustainability.

A novel approach simultaneously imparting well-hydrophobicity and photothermal conversion effect to polymer materials: solar-promoted absorption of organic solvents and oils

In this work, a series of polymer materials including pomelo peel, cotton fabric, polyurethane foam, and so on, are treated by heated CH₃SiCl₃, presenting desirable photo-thermal conversion function and hydrophobicity. As a representative material, the surface element and skeleton morphology of pomelo peel foam treated by CH₃SiCl₃ are analyzed detailedly. It is found that well-hydrophobicity (water contact angle of ~147°) and photo-thermal conversion performance (~91.2 °C under one sun) are attributed to the surface carbonization reaction and formation of CH₃-SiO₂ nanoparticles. Meanwhile, the treatment of CH₃SiCl₃ significantly increases the BET surface area to 3.0635 m²/g from 0.0973 m²/g. Therefore, pomelo peel-derived carbon foam presents a desirable adsorption capacity of organic solvents and oils (up to 43.2 times its original weight) and excellent removal efficiency (>99.0%). In addition, the rapid photo-thermal response (achieve ~73 °C at 40 s) and high equilibrium temperature (~91.2 °C) are als° demonstrated in pomelo peel-derived carbon foam. As a result, the absorption rate of highly-viscous oils is effectively promoted by the higher fluidity and capillary action caused by the solar-promoted mechanism. This study offers a scalable, easily operated, and environmentally friendly approach to prepare hydrophobic and photo-thermal materials, thus demonstrating a huge potential in oil/water separation application.

Adsorption of Malachite Green and Pb2+ by KMnO4-Modified Biochar: Insights and Mechanisms

In this study, the feasibility and mechanism of Pb2+ and malachite green (MG) adsorption from wastewater using KMnO4-modified bamboo biochar (KBC) was evaluated. The KBC was characterized by SEM–EDS, XRD, FTIR and XPS. The adsorption results for Pb2+ conformed to pseudo-second-order kinetics and the Langmuir model theory. Unlike the case for Pb2+, the Freundlich model better described the adsorption behaviour of MG, indicating that adsorption occurred within multiple molecular layers. Both pseudo-first-order kinetics and pseudo-second-order kinetics fit the MG adsorption data well, indicating that physical adsorption was involved in the adsorption process. In addition, the maximum adsorption capacity for Pb2+/MG was 123.47/1111.11 mg·g−1, KBC had high adsorption capacities for Pb2+ and MG, and the mechanisms of Pb2+ adsorption were mineral precipitation, functional group complexation, and cation-π interactions, while the main mechanisms for MG adsorption were pore filling, π–π interactions, and functional group complexation. In this study, KMnO4-modified biochar was prepared and used as an efficient adsorbent, and showed good application prospects for treatment of wastewater containing MG and Pb2+.