Fabrication of cobalt-iron Prussian blue analogs functionalized hybrid membranes for efficiently capturing Tl from water: performance and mechanism.

As trace levels of thallium (Tl) in water are lethal to humans and ecosystems, it is essential to exploit advanced technologies for efficient Tl removal. In response to this concern, an innovative composite membrane was developed, incorporating polytetrafluoroethylene (PTFE) and featuring a dual-support system with polydopamine (PDA) and polyethyleneimine (PEI), along with bimetallic Prussian blue analogues (Co@Fe-PBAs) as co-supports. The composite membrane exhibited an exceptional Tl+-adsorption capacity (qm) of 186.1 mg·g-1 when utilized for the treatment of water containing low concentration of Tl+ (0.5 mg⋅L-1). Transmission electron microscopy displayed the obvious Tl+ mapping inside the special hollow Co@Fe-PBAs crystals, demonstrating the deep intercalation of Tl+ via ion exchange and diffusion. The Tl+-adsorption capability of the composite membrane was not greatly affected by coexisting Na+, Ca2+ and Mg2+ as well as the tricky K+, indicating the excellent anti-interference. Co-doped PBAs enhanced ion exchange and intercalation of the composite membrane with Tl+ leading to excellent Tl+ removal efficiency. The composite membrane could efficiently remove Tl+ from thallium- contaminated river water to meet the USEPA standard. This study provides a cost-effective membrane-based solution for efficient Tl+ removal from Tl+-containing wastewater.

Enhanced removal of trace thallium by photo-promoted adsorption using Prussian blue@filter papers: Performance and mechanistic insights.

Developing highly efficient adsorbents for the removal of trace thallium(I) (Tl+) is crucial for addressing environmental challenges. In this study, we successfully synthesized cubic Prussian blue (PB) loading on filter papers using an intermediate layer (dopamine/polyethyleneimine) via in-situ methods. The as-prepared PB-modified FP demonstrated outstanding anti-interference properties and light-enhanced adsorption performance for Tl+ (0.5 mg/L) under ultraviolet (UV) irradiation, exhibiting twice the effectiveness compared to dark conditions, even in acidic and coexisting ionic environments. This indicated its suitability for treating complex Tl+-contaminated water. Notably, the removal efficiency for trace Tl+ was almost 100%, with a maximum experimental adsorption capacity of 86.2 mg/g after 1-h photo-promoted adsorption under 365 nm UV. Characterization results supported a proposed photo-driven redox mechanism that elucidated the interaction between Tl+ and PB-modified FP. Specifically, the accelerated Fe(III) to Fe(II) redox reaction facilitated Tl+ accommodation on the surface and/or lattice of PB, enhancing Tl+ adsorption by compensating for missed positive charges. This study provides valuable insights into utilizing PB-based materials to enhance the photo-enhanced Tl+ adsorption capacity in a cost-effective, easy-to-synthesize, and environmentally friendly manner.

Towards effective recovery of humate as green fertilizer from landfill leachate concentrate by electro-neutral nanofiltration membrane.

Under the environmental sustainability concept, landfill leachate concentrate can be up-cycled as a useful resource. Practical strategy for effective management of landfill leachate concentrate is to recover the existing humate as fertilizer purpose for plant growth. Herein, we designed an electro-neutral nanofiltration membrane to separate the humate and inorganic salts for achieving a sufficient humate recovery from leachate concentrate. The electro-neutral nanofiltration membrane yielded a high retention of humate (96.54 %) with an extremely low salt rejection (3.47 %), tremendously outperforming the state-of-the-art nanofiltration membranes and exhibiting superior promise in fractionation of humate and inorganic salts. With implementation of the pressure-driven concentration process, the electro-neutral nanofiltration membrane enriched the humate from 1756 to 51,466 mg∙L-1 at a fold of 32.6, enabling 90.0 % humate recovery and 96.4 % desalination efficiency from landfill leachate concentrate. Furthermore, the recovered humate not only exerted no phytotoxicity, but also significantly promoted the metabolism of red bean plants, serving as an effective green fertilizer. The study provides a conceptual and technical platform using high-performance electro-neutral nanofiltration membranes to extract the humate as a promising nutrient for fertilizer application, in view of sustainable landfill leachate concentrate treatment.

Activity and mechanism of vanadium sulfide for organic contaminants oxidation with peroxymonosulfate.

Transition metal sulfides have been demonstrated to be effective for peroxymonosulfate (PMS) activation towards wastewater treatment. However, the activity of vanadium sulfide (VS4) and the role of the chemical state of V have not been revealed. Here, three types of VS4 with various morphologies and chemical states of V were synthesized by using methanol (M-VS4, nanosphere composed of nanosheets), ethanol (E-VS4, sea urchin like nanosphere) and ultrapure water (U-VS4, compact nanosphere) as hydrothermal solvent, respectively, and used as heterogeneous catalysts to activate PMS for the degradation of refractory organic pollutants. The effects of PMS concentration, temperature, pH, inorganic ions, and humic acid (HA) on the degradation efficiency of VS4/PMS system were investigated systematically. The results indicated that the highest specific surface area and lowest ratio of V5+ enable E-VS4/PMS system possessed the highest performance in degrading tetracycline hydrochloride (TCH), in which 100% TCH was removed after operating 10 min (0.805 min-1) under a relatively low concentration of PMS (1 mM) and catalyst (100 mg/L). It also revealed that the system exhibited a typical radical process in TCH degradation, which could be attributed to the redox cycles between V5+, V4+ and V3+ in the presence of PMS to generate various radicals. This radical process enabled the E-VS4/PMS system with a high activity in wide reaction conditions and high mineralization ratios in degrading various refractory organic pollutants within 10 min. In addition, the E-VS4/PMS system exhibited favorable reusability and stability with very less V and S ions leaching, and showed excellent performance in real water purification.

Embedding Co in perovskite MoO3 for superior catalytic oxidation of refractory organic pollutants with peroxymonosulfate.

A cobalt (Co)-doped perovskite molybdenum trioxide (α-MoO3) catalyst (Co-MO) was synthesized by a facile pyrolysis strategy and used for degrading various organic contaminants via peroxymonosulfate (PMS) activation. The doped Co was inserted in the inter space between the octahedron [MoO6], facilitating the growth of the α-MoO3 crystal on the [010] direction. This unique structure accelerated the activation of PMS as the Co-MO could function as a carrier for electron transfer to facilitate the Co(II)/Co(III) cycle in the Co-MO/PMS system. As a result, the Co-MO/PMS system showed noticeable activity for removing 100% bisphenol A (BPA) under a broad conditions within 30 min. The radical quenching test and electron paramagnetic resonance analysis revealed that singlet oxygen (1O2) was the main active species for BPA degradation in the Co-MO/PMS system, while free radicals, such as O2•-, SO4•- and •OH, were also produced as the intermediate species. Furthermore, the carrier mechanism may enable the Co-MO/PMS system maintain relatively high performance during repeat use, and also excellent adaptability was revealed by the well function in various water matrices and high activity in degrading various refractory organic pollutants. Our findings pave a useful avenue for the rational design of novel cobalt-doped catalysts with high catalytic performance toward wide environmental applications.

Enhancing Thermal Conductivity of Polyvinylidene Fluoride Composites by Carbon Fiber: Length Effect of the Filler.

Thermally conductive polyvinylidene fluoride (PVDF) composites were prepared by incorporating carbon fibers (CFs) with different lengths (286.6 ± 7.1 and 150.0 ± 2.3 µm) via cold pressing, followed by sintering. The length effects of the CF on the thermal conductivity, polymer crystallization behaviors, and mechanical properties of the PVDF composites were studied. The through-plane thermal conductivity of the PVDF composites increased significantly with the rise in CF loadings. The highest thermal conductivity of 2.89 W/(m∙K) was achieved for the PVDF composites containing 40 wt.% shorter CFs, ~17 times higher than that of the pure PVDF (~0.17 W/(m∙K)). The shorter CFs had more pronounced thermal conductive enhancement effects than the original longer CFs at higher filler loadings. CFs increased the storage modulus and the glass transition temperature of the PVDF. This work provides a new way to develop thermally conductive, mechanically, and chemically stable polymer composites by introducing CFs with different lengths.

MOF-Like 3D Graphene-Based Catalytic Membrane Fabricated by One-Step Laser Scribing for Robust Water Purification and Green Energy Production.

Increasing both clean water and green energy demands for survival and development are the grand challenges of our age. Here, we successfully fabricate a novel multifunctional 3D graphene-based catalytic membrane (3D-GCM) with active metal nanoparticles (AMNs) loading for simultaneously obtaining the water purification and clean energy generation, via a "green" one-step laser scribing technology. The as-prepared 3D-GCM shows high porosity and uniform distribution with AMNs, which exhibits high permeated fluxes (over 100 L m-2 h-1) and versatile super-adsorption capacities for the removal of tricky organic pollutants from wastewater under ultra-low pressure-driving (0.1 bar). After adsorption saturating, the AMNs in 3D-GCM actuates the advanced oxidization process to self-clean the fouled membrane via the catalysis, and restores the adsorption capacity well for the next time membrane separation. Most importantly, the 3D-GCM with the welding of laser scribing overcomes the lateral shear force damaging during the long-term separation. Moreover, the 3D-GCM could emit plentiful of hot electrons from AMNs under light irradiation, realizing the membrane catalytic hydrolysis reactions for hydrogen energy generation. This "green" precision manufacturing with laser scribing technology provides a feasible technology to fabricate high-efficient and robust 3D-GCM microreactor in the tricky wastewater purification and sustainable clean energy production as well.

Confining Nano-Fe3O4 in the Superhydrophilic Membrane Skin Layer to Minimize Internal Fouling.

Membrane surface fouling is often reversible as it can be mitigated by enhancing the crossflow shear force. However, membrane internal fouling is often irreversible and thus more challenging. In this study, we developed a new superhydrophilic poly(vinylidene fluoride) (P-PVDF) membrane confined with nano-Fe3O4 in the top skin layer via reverse filtration to reduce internal fouling. The surface of the P-PVDF membrane confined with nano-Fe3O4 had superwetting properties (water contact angle reaching 0° within 1 s), increased roughness (from 182 to 239 nm), and enhanced water affinity. The Fe3O4@P-PVDF membrane surface showed a thicker and enhanced hydration layer, which prevented foulants from approaching membrane surfaces and pores, thereby improving the rejection. For example, when 50 ppm humic acid (HA) solution was used as the feed, the removal efficiency of the Fe3O4@P-PVDF membrane was ∼67%, while the HA removal of the P-PVDF membrane was only ∼20%. The results from the resistance-in-series model showed that nanoconfinement of Fe3O4 in the top skin layer of the membrane allowed foulants to accumulate on the membrane surface (i.e., surface fouling) rather than within the internal pores (i.e., internal fouling). The filtration results under crossflow fouling and cleaning confirmed that the Fe3O4@P-PVDF membrane had higher surface fouling but it was much more reversible and much lower internal fouling compared with the control membrane. Our fouling analysis offers new insights into mass transfer mechanisms of the membrane with a nanoconfinement-enhanced hydration layer. This study provides an effective strategy to develop membranes with low internal fouling propensities.

Edible films and coatings for shelf life extension of mango: a review.

Edible films and coatings are eco-friendly promising materials for preserving the quality and extending the shelf life of fresh and minimally-processed fruits. They can form protective layers around fruits, regulate their respiration rates, and protect them from loss of water, tissue softening, browning, and microbial contamination. Edible films and coatings have many advantages over other post-harvest treatments. They can add commercial value to fruits by enhancing their appearance, and act as carriers of functional ingredients, such as antioxidants, antimicrobial agents and nutraceuticals. Mango, a highly perishable tropical fruit, has a short post-harvest life, which limits transport to distant markets. Application of edible films and coatings on mango fruits is an effective method to preserve their quality and safety. This paper provides an overview of desirable properties for films and coatings, and recent development in different edible coatings for both fresh and minimally-processed mango. The most popular edible coating materials, such as chitosan, waxes, starch, gums, and cellulose used for mango are reviewed. The commercialization of coating formulations and equipment used for application of coatings are discussed. The environmental impacts, safety aspects, and the challenges encountered are outlined. The opportunities to use other coating materials, such as aloe-vera gel, microbial polysaccharides, and photosynthetic microorganisms are also examined.

Sustainable management of landfill leachate concentrate via nanofiltration enhanced by one-step rapid assembly of metal-organic coordination complexes.

Sustainable treatment of the highly saline landfill leachate concentrate for application as green fertilizer calls for effective fractionation of the existing humic substances and inorganic salts; advanced selective nanofiltration membranes are proposed for this. One-step, rapid assembly of a tannic acid-Fe3+ coordination complex is a promising strategy to endow the membranes with an enhanced nanofiltration performance. In this study, a robust and homogeneous tannic acid-Fe3+ coordination complex layer was effectively coated onto the surface of a loose nanofiltration substrate in an extremely short time (15 s). After the coating of the tannic acid-Fe3+ coordination complex layer, the nanofiltration membrane showed a significantly reduced molecule weight cutoff (i.e., reduction from 601 to 279 Da) and thus enhanced selectivity towards humic substances. Specifically, the rejection to humic substances of the coated nanofiltration membrane increased from 95.31±0.54% to 99.32±0.18% with negligible rise in salt rejection, demonstrating an enhanced fractionation efficacy for humic substances and salts. Assisted by a diafiltration operation with the coated nanofiltration membrane, humic substances in the landfill leachate concentrate were effectively purified and extracted with 96.60% recovery. Particularly, the humic substances were linearly enriched by ca. 7.8 folds (i.e., from 1837 to 13970 mg·L-1) with a purity of 98.91% for potential application as liquid fertilizer. The one-step rapid tannic acid-Fe3+ coordination complex coating exhibits an impressive efficacy to engineer advanced nanofiltration membranes that could be applied at a large scale for sustainable resource extraction from landfill leachate concentrate.

Integrated loose nanofiltration-electrodialysis process for sustainable resource extraction from high-salinity textile wastewater.

Effective extraction of useful resources from high-salinity textile wastewater is a critical pathway for sustainable wastewater management. In this study, an integrated loose nanofiltration-electrodialysis process was explored for simultaneous recovery of dyes, NaCl and pure water from high-salinity textile wastewater, thus closing the material loop and minimizing waste emission. Specifically, a loose nanofiltration membrane (molecular weight cutoff of ~800 Da) was proposed to fractionate the dye and NaCl in the high-salinity textile wastewater. Through a nanofiltration-diafiltration unit, including a pre-concentration stage and a constant-volume diafiltration stage, the dye could be recovered from the high-salinity textile wastewater, being enriched at a factor of ~9.0, i.e., from 2.01 to 17.9 g·L-1 with 98.4% purity. Assisted with the subsequent implementation of electrodialysis, the NaCl concentrate and pure water were effectively reclaimed from the salt-containing permeate coming from the loose nanofiltration-diafiltration. Simultaneously, the produced pure water was further recycled to the nanofiltration-diafiltration unit. This study shows the potential of the integration of loose nanofiltation-diafiltration with electrodialysis for sufficient resource extraction from high-salinity textile wastewater.

A general QSPR protocol for the prediction of atomic/inter-atomic properties: a fragment based graph convolutional neural network (F-GCN).

In this study, a general quantitative structure-property relationship (QSPR) protocol, fragment based graph convolutional neural network (F-GCN), was developed for the prediction of atomic/inter-atomic properties. We applied this novel artificial intelligence (AI) tool in predictions of NMR chemical shifts and bond dissociation energies (BDEs). The obtained results were comparable to experimental measurements, while the computational cost was substantially reduced, with respect to pure density functional theory (DFT) calculations. The two important features of F-GCN can be summarised as: first, it could utilise different levels of molecular fragments for atomic/inter-atomic information extraction; second, the designed architecture is also open to include additional descriptors for a more accurate solution of the local environment at atomic level, making itself more efficient for structural solutions. And during our test, the averaged prediction error of 1H NMR chemical shifts is as small as 0.32 ppm, and the error of C-H BDE estimation is 2.7 kcal mol-1. Moreover, we further demonstrated the applicability of this developed F-GCN model via several challenging structural assignments. The success of the F-GCN in atomic and inter-atomic predictions also indicates an essential improvement of computational chemistry with the assistance of AI tools.

Activation of persulfate by MnOOH: Degradation of organic compounds by nonradical mechanism.

Advanced oxidation processes (AOPs) based on persulfate (PS) has attracted great attention due to its high efficiency for degradation of organic pollutants. Manganese-based materials have been considered as the desirable catalysts for in-situ chemical oxidation since they are abundant in the earth's crust and environment-friendly. In this study, manganese oxyhydroxide (MnOOH) was used as an activator for PS to degrade p-chloroaniline (PCA) from wastewater. The effects of MnOOH dosage, PS dosage and initial pH on PCA degradation performance were studied. Experimental results showed that PCA degradation efficiency was enhanced by higher MnOOH and PS addition, and the degradation efficiency was slightly inhibited as the initial pH increased from 3 to 9. MnOOH showed excellent stability and reusability when used as the activator of PS. In addition, a comprehensive study was conducted to determine the PS activation mechanism. The results revealed that PS activation by MnOOH followed a nonradical mechanism. No 1O2 was generated, and the main active substance in the reaction was the activated PS molecule on the surface of MnOOH. The hydroxyl group on the catalyst surface acted as a bridge connecting PS and the catalyst, leading to the activation of PS. The intermediates during PCA degradation were also analyzed, and three possible degradation pathways of PCA were proposed. This study expects to deepen the understanding of the PS activation mechanism by manganese oxide, and provides technical support for the practical application of AOPs of manganese-based materials for wastewater treatment.

Simple Amphoteric Charge Strategy to Reinforce Superhydrophilic Polyvinylidene Fluoride Membrane for Highly Efficient Separation of Various Surfactant-Stabilized Oil-in-Water Emulsions.

Long-term efficient separation of highly emulsified oily wastewater is challenging. Reported herein is the preparation of a reinforced superhydrophilic, underwater superoleophobic membrane with demulsification properties using active iron nanoparticles in situ generated on a polydopamine (PDA)/polyethylenimine (PEI)-modified polyvinylidene fluoride (PVDF) membrane surface. A stable zwitterionic structure is fabricated on the membrane surface and provides it with an excellent capability of binding a hydration layer, leading to enhanced superhydrophilic/underwater superoleophobic properties. The interaction between the membrane surface and water is quantified using the relaxation time of water. After iron nanoparticles in situ anchoring, the superhydrophilic, underwater superoleophobic PDA/PEI modified PVDF membrane shows more stable flux behaviors, higher oil separation efficiency, demulsification, and excellent antioil-fouling properties for various anionic, nonionic, and cationic surfactant-stabilized oil-in-water emulsions in a crossflow filtration system. The reinforced hydration layer and the amphoteric charged demusification properties of the membrane play important roles in enhancing the membrane separation performance. The reinforced membrane also exhibits excellent cleaning and reusability performance in long-term operations. The outstanding separation performance, as well as the simple and cost-effective fabrication process of the membrane with various favorable properties, highlight its promise in practical emulsified oily water applications.

Hierarchically Active Poly(vinylidene fluoride) Membrane Fabricated by In Situ Generated Zero-Valent Iron for Fouling Reduction.

Sodium hypochlorite (NaClO) solution is a typical cleaning agent for membrane fouling. However, it can damage membrane chemical structures and produce toxic disinfection byproducts, which in turn reduces the membrane performance. This study focuses on the fabrication of active membranes thereby overcoming the limitations of chemical cleaning. A hierarchical active poly(vinylidene fluoride) membrane with polydopamine/polyethyleneimine (PEI) co-supported iron nanoparticle (Fe NP) catalysts was successfully constructed and denoted as a Fe-HP-membrane. The Fe-HP-membrane exhibited excellent advanced oxidation activity with maximum flux recoveries (∼85% with bovine serum albumin [BSA] and ∼95% with humic acid [HA] solutions). After the static experiment of ∼30 days, the BSA proteins and HA successfully desorbed from the membrane surface. Especially, with a trace amount of hydrogen peroxide (H2O2) flowing over the surface of the Fe-HP-membrane, highly exposed active sites were observed. Membrane cleaning showed that the "outside-to-in" active surfaces generated considerable amounts of •OH radicals at the interface of BSA or HA and the fouled membrane. As a result, the unwanted foulants were successfully removed from the membrane interface, enabling multiple use of the Fe-HP-membrane. Therefore, backwashing with a small amount of H2O2 (0.33 wt %) covered ∼20% of the flux. In contrary, backwashing with NaClO (1 wt %) can only achieve a flux recovery of ∼10% after six consecutive BSA filtration cycles. The Fe-HP-membrane exhibited better HA foulant removal (a flux recovery of ∼51%) after backwashing with H2O2 than using NaClO (a flux recovery of ∼43%). Our findings demonstrate a new platform for water treatment and regeneration of fouled membranes.

Sustainable management of landfill leachate concentrate through recovering humic substance as liquid fertilizer by loose nanofiltration.

The hybrid membrane bioreactor - nanofiltration treatment process can be an effective approach for treating the landfill leachate, but the residual leachate concentrate highly loaded with the humic substance and salts remains an environmental concern. Herein, a loose nanofiltration membrane (molecular weight cut-off of 860 Da) was used to recover the humic substance, which can act as a key component of organic fertilizer, from the leachate concentrate. The loose nanofiltration membrane showed the high permeation fluxes and high transmissions (>94.7%) for most inorganic ions (i.e., Na+, K+, Cl-, and NO3-), while retaining 95.7 ±â€¯0.3% of the humic substance, demonstrating its great potential in effective fractionation of humic substance from inorganic salts in the leachate concentrate. The operation conditions, i.e., cross-flow rates and temperatures, had more pronounced impacts on the filtration performance of the loose nanofiltration membrane. Increasing cross-flow rates from 60 to 260 L h-1 resulted in an improvement of ca. 7.3% in the humic substance rejection, mainly due to the reduced concentration polarization effect. In contrast, the solute rejection of the nanofiltration membrane was negatively dependent on the temperature. The rejection of humic substance decreased from 96.3 ±â€¯0.3% to 92.0 ±â€¯0.4% with increasing the temperature from 23 to 35 °C, likely due to the enlargement of the membrane pore size and enhancement in solute diffusivity. The humic substance was enriched from 1735 to 15,287 mg L-1, yielding a 91.2% recovery ratio with 85.7% desalination efficiency at a concentration factor of 9.6. The recovered HS had significantly stimulated the seed germination and growth of the green mungbean plants with no obvious phytotoxicity. These results demonstrate that loose nanofiltration can be an effective promising technology to recover the humic substance as a valuable fertilizer component towards sustainable management of the landfill leachate concentrate.

Conventional Ultrafiltration As Effective Strategy for Dye/Salt Fractionation in Textile Wastewater Treatment.

Use of tight ultrafiltration (UF) membranes has created a new pathway in fractionation of dye/salt mixtures from textile wastewater for sustainable resource recovery. Unexpectedly, a consistently high rejection for the dyes with smaller sizes related to the pore sizes of tight UF membranes is yielded. The potential mechanism involved in this puzzle remains unclear. In this study, seven tailored UF membranes with molecular weight cut-offs (MWCOs) from 6050 to 17530 Da were applied to separate dye/salt mixtures. These UF membranes allowed a complete transfer for NaCl and Na2SO4, due to large pore sizes. Additionally, these UF membranes had acceptably high rejections for direct and reactive dyes, due to the aggregation of dyes as clusters for enhanced sizes and low diffusivity. Specifically, the membrane with an MWCO of 7310 Da showed a complete rejection for reactive blue 2 and direct dyes. An integrated UF-diafiltration process was subsequently designed for fractionation of reactive blue 2/Na2SO4 mixture, achieving 99.84% desalination efficiency and 97.47% dye recovery. Furthermore, reactive blue 2 can be concentrated from 2.01 to 31.80 g·L-1. These results indicate that UF membranes even with porous structures are promising for effective fractionation of dyes and salts in sustainable textile wastewater treatment.