Protein-activated atomic layer deposition for robust crude-oil-repellent hierarchical nano-armored membranes

Developing cellulose-based hydrophobic/hydrophilic composites for efficient adsorption of oils and heavy metals from water

The oily wastewater and heavy metal ions have been increasingly discharged into water environment, posting a serious threat to ecosystems and human health. However, it remains challenging to use single separation technology to effectively remove oil and heavy metal ions in oil-water mixtures simultaneously. Herein, novel hydrophobic/hydrophilic composites (HHC) were successfully prepared by using A4 paper-derived hydrophilic cellulose as the modified matrix, modifying the polydopamine layer and in-situ growth nanoscale zero-valent iron as active adsorption materials, combined with oleic acid-modified hydrophobic magnetic hollow carbon microspheres, which were used to efficiently and rapidly adsorb heavy metals and oil in oil-water mixtures. Under the optimal adsorption conditions, the adsorption amounts of As(III), As(V), Pb(II) and Cu(II) were 289.6 mg/g, 341.9 mg/g, 241.2 mg/g and 277.5 mg/g, respectively, and the mass transfer rate of HHC to the target ions is fast. The HHC have efficient separation performance for layered oil-water mixtures and emulsified oil-water mixtures, with separation efficiency of 97 % and 92 %. At the same time, due to the abundant adsorption sites, the HHC also exhibit splendid regeneration performance for the four ions after multiple adsorption utilization. Our work designed a approach to achieving promising oil and heavy metal adsorbents with higher adsorption capacity and better regenerative properties.

Dialdehyde cellulose (DAC) and polyethyleneimine (PEI) coated polyvinylidene fluoride (PVDF) membrane for simultaneously removing emulsified oils and anionic dyes

Developing high-efficiency membrane for oil and dye removal is very urgent, because wastewater containing them can cause great damage to human and environment. In this study, a coated membrane was fabricated by applying DAC and PEI onto the commercial PVDF microfiltration membrane for supplying the demand. The coated membrane presents superhydrophlic and superoleophobic properties with a water contact angle of 0o and underwater oil contact angle exceed 150°, as well as excellent low underwater oil adhesion performance. The coated membrane shows high separation efficiency exceeded 99.0% and flux 350.0 L·m-2·h-1 when used for separating for six kinds of oil including pump oil, sunflower oil, n-hexadecane, soybean oil, diesel and kerosene in water emulsions. Additionally, the coated membrane can effectively remove anionic dyes, achieving rejection rates of 94.7%, 93.4%, 92.3%, 90.7% for the CR, MB, RB5, AR66, respectively. More importantly, the membrane was able to simultaneously remove emulsified oil and soluble anionic dyes in wastewater containing both of them. Therefore, this novel coated membrane can be a promising candidate for treating complex wastewater.

Chelation-directed interface engineering of in-place self-cleaning membranes

Water-energy sustainability will depend upon the rapid development of advanced pressure-driven separation membranes. Although energy-efficient, water-treatment membranes are constrained by ubiquitous fouling, which may be alleviated by engineering self-cleaning membrane interfaces. In this study, a metal-polyphenol network was designed to direct the armorization of catalytic nanofilms (ca. 18 nm) on inert polymeric membranes. The chelation-directed mineralized coating exhibits high polarity, superhydrophilicity, and ultralow adhesion to crude oil, enabling cyclable crude oil-in-water emulsion separation. The in-place flux recovery rate exceeded 99.9%, alleviating the need for traditional ex situ cleaning. The chelation-directed nanoarmored membrane exhibited 48-fold and 6.8-fold figures of merit for in-place self-cleaning regeneration compared to the control membrane and simple hydraulic cleaning, respectively. Precursor interaction mechanisms were identified by density functional theory calculations. Chelation-directed armorization offers promise for sustainable applications in catalysis, biomedicine, environmental remediation, and beyond.

Zeolite Imidazolate Frameworks-8@SiO2-ZrO2 Crystal-Amorphous Hybrid Core-Shell Structure as a Building Block for Water Purification Membranes

Metal-organic frameworks (MOFs) are emerging as promising materials for water purification membranes, owing to their uniform microporous structures and chemical functionalities. Here, we report a simple procedure for depositing MOF-based nanofiltration membranes on commercial TiO2 ceramic tubular supports, completely avoiding the use of dispersants or binders. Zeolite imidazolate frameworks-8 (ZIF-8) nanocrystals were synthesized in methanol at room temperature and subsequently coated with an amorphous SiO2-ZrO2 gel to generate a dispersion of ZIF-8@SiO2-ZrO2 core-shell nanoparticles. The amorphous SiO2-ZrO2 gel served as a binding agent for the ZIF-8 nanocrystals, thus forming a defect-free continuous membrane layer. After repeating the coating twice, the active layer had a thickness of 0.96 μm, presenting a rejection rate >90% for the total organic carbon in an aquaculture effluent and in a wastewater treatment plant, while reducing the concentration of trimethoprim, here used as a target pollutant. Moreover, the oxide gel provided the MOF-based active layer with good adhesion to the support and enhanced its hydrophilicity, resulting in a membrane with excellent mechanical stability and resistance to fouling during the crossflow filtration of the real wastewater samples. These results implied the high potential of the MOF-based nanocomposite membrane for effective treatment of actual wastewater streams.