Study of MOF incorporated dual layer membrane with enhanced removal of ammonia and per-/poly-fluoroalkyl substances (PFAS) in landfill leachate treatment

Effect of pyrolysis temperature on characteristics and chloramphenicol adsorption performance of NH2-MIL-53(Al)-derived amine-functionalized porous carbons

Several activities such as aquaculture, human and feedstock therapies can directly release antibiotics into water. Due to high stability, low hydrolysis and non-biodegradation, they can accumulate in the aqueous environment and transport to aquatic species. Here, we synthesized amine-functionalized porous carbons (ANC) by a direct-pyrolysis process of NH2-MIL-53(Al) as a sacrificial template at between 600 and 900 °C and utilized them to eliminate chloramphenicol antibiotic from water. The NH2-MIL-53(Al)-derived porous carbons obtained high surface areas (304.7-1600 m2 g-1) and chloramphenicol adsorption capacities (148.3-261.5 mg g-1). Several factors such as hydrogen bonding, Yoshida hydrogen bonding, and π-π interaction, hydrophobic interaction possibly controlled adsorption mechanisms. The ANC800 could be reused four cycles along with high stability in structure. As a result, NH2-MIL-53(Al)-derived porous carbons are recommended as recyclable and efficient adsorbents to the treatment of antibiotics in water.

Removing polyfluoroalkyl substances (PFAS) from wastewater with mixed matrix membranes

Polyfluoroalkyl and perfluoroalkyl (PFAS) chemicals are fluorinated and exhibit complicated behavior. They are determined and highly resistant to ecological modifications that render plants ecologically robust. Thermal stability and water and oil resistance are examples of material qualities. Their adverse consequences are causing increasing worry due to their bioaccumulative nature in humans and other creatures. Direct data indicates that PFAS exposure in humans causes endocrine system disruption, immune system suppression, obesity, increased cholesterol, and cancer. Several PFASs are present in drinking water at low doses and may harm people. These cancer-causing PFAS have caused concern for water bodies all around the globe. Analytical techniques are used to identify and measure PFAS in an aqueous medium (membrane). Furthermore, a deeper explanation is provided for PFAS removal methods, including mixed matrix membrane (MMM) technology. By removing over 99 % of the PFAS from wastewater, MMMs may effectively remove PFAS from sewage when the support matrix contains adsorbing components. Furthermore, we consider several factors affecting the removal of PFAS and practical sorption methods for PFAS onto various adsorbents.

Dynamic evolution and response strategy of demand in buffer zone between scattered groundwater sources and hazardous waste landfill

Groundwater contamination by landfill leachate is a major concern. Ignoring the long-term increase in leakage caused by the aging of engineered materials may lead to underestimation of the buffer distance (BFD) demand of landfills. In this study, a long-term BFD prediction model was developed by coupling an engineering material aging and defect evolution module with leachate leakage and migration transformation model, and was applicated and validated. The results showed that under landfill performance degradation, the required BFD was 2400 m, i.e., 6 times higher than under undegraded conditions. With the degradation of the performance, the BFD required to attenuate the heavy metal concentrations of groundwater increases more than the BFD required to attenuate organic pollutants. For example, the BFD required for zinc (Zn) was 5 times higher than that required for undegraded conditions, while for 2,4-dichlorophenol (2,4-D), the BFD was 1 times higher. Considering the uncertainties of the model parameters and structure, the BFD should be greater than 3000 m to ensure long-term safe water use under unfavorable conditions such as large leachate production and leakage, weak degradation and fast diffusion of pollutants. If the actual BFD does not meet the demand due to landfill performance degradation, the landfill owner can reduce the reliance on the BFD by reducing the waste leaching behavior. For example, the landfill in our case study would require a BFD of 2400 m, but by reducing the leaching concentration of zinc in the waste from 120 to 55 mg/L, this requirement could be reduced to 900 m.

Enhanced performance of ZIF-8 nanocrystals hybrid monolithic composites via an in-situ growth strategy for efficient capillary microextraction of perfluoroalkyl phosphonic acids

Enrichment of perfluoroalkyl phosphonic acids (PFPAs) is of great significance and challenging for environmental monitoring, due to their toxic and persistent nature, highly fluorinated character as well as low concentration. Herein, novel metal-organic frameworks (MOFs) hybrid monolithic composites were prepared via metal oxide-mediated in situ growth strategy and utilized for capillary microextraction (CME) of PFPAs. A porous pristine monolith was initially obtained by copolymerization of the zinc oxide nanoparticles (ZnO-NPs)-dispersed methacrylic acid (MAA) with ethylenedimethacrylate (EDMA) and dodecafluoroheptyl acrylate (DFA). Afterwards, nanoscale-facilitated transformation of ZnO nanocrystals into the zeolitic imidazolate framework-8 (ZIF-8) nanocrystals was successfully realized via the dissolution-precipitation of the embedded ZnO-NPs in the precursor monolith in the presence of 2-methylimidazole. Experimental and spectroscopic results (SEM, N₂ adsorption-desorption, FT-IR, XPS) revealed that the coating of ZIF-8 nanocrystals significantly increased the surface area of the obtained ZIF-8 hybrid monolith and endowed the material abundant surface-localized unsaturated zinc sites. The proposed adsorbent showed highly enhanced extraction performance for PFPAs in CME, which was mainly ascribed to the strong fluorine affinity, Lewis acid/base complexing, anion-exchange, and weakly π-CF interaction. The coupling of CME with LC-MS enables effective and sensitive analysis of ultra-trace PFPAs in environment water and human serum. The coupling method demonstrated low detection limits (2.16-4.12 ng L^-1) with satisfactory recoveries (82.0-108.0%) and precision (RSDs ≤6.2%). This work offered a versatile route to design and fabricate selective materials for emerging contaminant enrichment in complicated matrices.

Treatment to surfactant containing wastewater with membrane distillation membrane with novel sandwich structure

Surfactant containing wastewater widely exists in textile industry, which hardly to be treated by membrane technology due to its high in salinity and wetting potential. In this study, PVDF membrane was modified by constructing a PDMS-SiO₂-PDMS "sandwich" structure on top of its surface via coating to achieve resistance to surfactant induced wetting. The "sandwich" layer was optimized based on the membrane performance during membrane distillation. Compared to the pristine PVDF membrane with contact angle of 92°, the water contact angle of the membrane with a "sandwich" layer of 0.44 μm increased to 153°. For the feed contained 0.5 wt% NaCl and 0.25 wt% surfactant, there was no membrane wetting occurred during the experiment period using the membrane with a "sandwich" structure, in comparison to the pristine PVDF membrane being wetted from beginning. For a challenge experiment to the developed membrane lasting for 100 h using a surfactant containing feed, there is no wetting sign observed and the stable flux is 20 kg·m^-2·h^-1.

Enhanced high-salinity brines treatment using polyamide nanofiltration membrane with tunable interlayered MXene channel

The introduce of a nanomaterial interlayer between the substrate and polyamide is identified as a promising strategy to construct highly performed membranes. Two-dimensional (2D) materials are potential candidates as interlayer for advanced thin-film nanocomposite interlayer (TFNi) membranes. Nevertheless, low permeability, selectivity and long-term stability are still critical issues in TFNi membrane manufacture. Herein, a scalable approach for constructing TFNi membranes was implemented using stacked MXene nanosheets as interlayer, wherein the Fe₃O₄ nanoparticles worked as the sacrificial template to regulate the interlayer spacing of the 2D channels. SEM, XPS, water contact angle, and zeta potential were used to characterize the physical and chemical properties of prepared TFNi membranes, and the results shows that the presence of MXene interlayer increased the hydrophilicity, thinness and roughness of polyamide layer compared to that of pure TFC membranes. Besides, the enlarged interlayer channel after the sacrifice of the Fe₃O₄ nanoparticles greatly boosted the transport of the water molecules. The resultant membranes exhibited nearly double fold of water flux (66.4 ± 3.45 L·m^-2·h^-1) and higher selective separation factor (48.4) compared with those prepared without interlayer, while the outstanding salt rejection (>97 %) was maintained. This work achieves an innovative strategy for multifunctional polyamide nanofiltration membrane construction.

Pervaporation Polyvinyl Alcohol Membranes Modified with Zr-Based Metal Organic Frameworks for Isopropanol Dehydration

Metal-organic frameworks (MOFs) are perceptive modifiers for the creation of mixed matrix membranes to improve the pervaporation performance of polymeric membranes. In this study, novel membranes based on polyvinyl alcohol (PVA) modified with Zr-MOFs (MIL-140A, MIL-140A-AcOH, and MIL-140A-AcOH-EDTA) particles were developed for enhanced pervaporation dehydration of isopropanol. Two membrane types (substrateless-freestanding; and formed on polyacrylonitrile support-composite) were prepared. The additional cross-linking of membranes with glutaraldehyde was carried out to circumvent membrane stability in pervaporation dehydration of diluted solutions. The synthesized Zr-MOFs were characterized by scanning electron microscopy, X-ray powder diffraction analysis, and specific surface area measurement. The structure and physicochemical properties of the developed membranes were investigated by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, thermogravimetric analysis, swelling experiments, and contact angle measurements. The PVA and PVA/Zr-MOFs membranes were evaluated in pervaporation dehydration of isopropanol in a wide concentration range. It was found that the composite cross-linked PVA membrane with 10 wt% MIL-140A had optimal pervaporation performance in the isopropanol dehydration (12-100 wt% water) at 22 °C: 0.15-1.33 kg/(m²h) permeation flux, 99.9 wt% water in the permeate, and is promising for the use in the industrial dehydration of alcohols.

Nitrogen Recovery from Landfill Leachate Using Lab- and Pilot-Scale Membrane Contactors: Research into Fouling Development and Membrane Characterization Effects

Membrane contactor technology affords great opportunities for nitrogen recovery from waste streams. This study presents a performance comparison between lab- and pilot-scale membrane contactors using landfill leachate samples. Polypropylene (PP) and polytetrafluoroethylene (PTFE) fibers in different dimensions were compared in terms of ammonia (NH₃) recovery on a lab scale using a synthetic ammonium solution. The effect of pre-treating the leachate with tannin coagulation on nitrogen recovery was also evaluated. An ammonia transfer on the lab and pilot scale was scrutinized using landfill leachate as a feed solution. It was found that PTFE fibers performed better than PP fibers. Among PTFE fibers, the most porous one (denoted as M1) had the highest NH₃ flux of 19.2 g/m².h. Tannin pre-treatment reduced fouling and increased NH₃, which in turn improved nitrogen recovery. The mass transfer coefficient of the lab-scale reactor was more than double that of the pilot reactor (1.80 × 10^-7 m/s vs. 4.45 × 10^-7 m/s). This was likely attributed to the difference in reactor design. An analysis of the membrane surface showed that the landfill leachate caused a combination of inorganic and organic fouling. Cleaning with UV and 0.01 M H₂O₂ was capable of removing the fouling completely and restoring the membrane characteristics.

A Review on Removal and Destruction of Per- and Polyfluoroalkyl Substances (PFAS) by Novel Membranes

Per- and Polyfluoroalkyl Substances (PFAS) are anthropogenic chemicals consisting of thousands of individual species. PFAS consists of a fully or partly fluorinated carbon–fluorine bond, which is hard to break and requires a high amount of energy (536 kJ/mole). Resulting from their unique hydrophobic/oleophobic nature and their chemical and mechanical stability, they are highly resistant to thermal, chemical, and biological degradation. PFAS have been used extensively worldwide since the 1940s in various products such as non-stick household items, food-packaging, cosmetics, electronics, and firefighting foams. Exposure to PFAS may lead to health issues such as hormonal imbalances, a compromised immune system, cancer, fertility disorders, and adverse effects on fetal growth and learning ability in children. To date, very few novel membrane approaches have been reported effective in removing and destroying PFAS. Therefore, this article provides a critical review of PFAS treatment and removal approaches by membrane separation systems. We discuss recently reported novel and effective membrane techniques for PFAS separation and include a detailed discussion of parameters affecting PFAS membrane separation and destruction. Moreover, an estimation of cost analysis is also included for each treatment technology. Additionally, since the PFAS treatment technology is still growing, we have incorporated several future directions for efficient PFAS treatment.