Showing papers by "Jian Jin published in 2022"

Double‐Defense Design of Super‐Anti‐Fouling Membranes for Oil/Water Emulsion Separation

Abstract: Oil fouling threatens the water flux stability of membranes for oil/water separation. Simple hydrophilic modification fights for an opportunity to prevent oil contamination but fails to eliminate severe water flux decline. In essence, a “single‐defense” mechanism is insufficient to build a potent barrier against accumulated cake layer under a filtration environment. This work reports a “double‐defense” design by integrating hydrophilic polymer brushes and hydrogel layer on oil/water separation membranes for desired anti‐oil‐fouling property, where a poly(vinylidene fluoride) porous membrane is first covered by a layer of poly(hydroxyethyl methylacrylate) hydrogel and then controllably grafted with poly(sulfobetaine) brushes. The spatially hierarchical structure establishes a highly covered “double‐defense” barrier for the membrane surface to efficiently repel oil adhesion and the formation of an accumulated cake layer. When separating various surfactant‐stabilized oil‐in‐water emulsions, the permeating flux displays a nearly zero decline throughout the whole filtration period. Most importantly, the permeating flux of the membrane is almost the same when filtrating pure water and filtrating oil‐in‐water emulsions, which is difficult to be achieved by the general membranes, indicating that the membrane has excellent anti‐oil‐fouling property superior to the currently reported membranes.

Metal-Organic Framework Composite Photothermal Membrane for Removal of High-Concentration Volatile Organic Compounds from Water via Molecular Sieving.

Abstract: Water-soluble volatile organic compounds (VOCs) are among the most difficult-to-treat species during wastewater treatment. The current purification and removal of high-concentration VOCs still rely on the energy-consuming distillation and high-pressure driven reverse osmosis technology. There is an urgent need for an advanced technology that can effectively remove high-concentration VOCs from water. Here, we report a metal-organic framework (MOF)/polyaniline (PANI) nanofiber array composite photothermal membrane for removal of high-concentration VOCs from water via molecular sieving during a solar-driven evaporation process. The modified zeolitic imidazole framework-8 (ZIF-8) layer grown on a PANI nanofiber array acts as a molecular sieving layer to evaporate water but intercept VOCs. The composite membrane exhibits high VOCs rejection and a high-water evaporation rate for water containing different concentrations of VOCs. When treating water containing VOCs with a concentration of up to 400 mg L-1, the VOCs rejection rate is up to 99% and the water evaporation rate is 1.0 kg m-2 h-1 under 1 sun irradiation (1 kW m-2). Our work effectively combines the molecular sieve effect with a solar-driven evaporation process, which provides an effective strategy for the treatment of water containing VOCs.

Gradient Adhesive Hydrogel Decorated Superhydrophilic Membranes for Ultra‐Stable Oil/Water Separation

Abstract: Hydrogels are excellent for protecting membranes from oil fouling for oil/water separation. However, conventional hydrogels including adhesive hydrogels have a contradictory between high adhesion on membranes and anti‐oil‐fouling ability. Herein, the design of an adhesive hydrogel on membranes is proposed by ingeniously integrating high adhesion on membranes, outstanding anti‐oil‐fouling ability, ultrathin thickness suitable for membrane decoration and satisfactory durability, where an inside‐out gradient distribution of adhesive protocatechuic acid (PCA) and hydrated calcium alginate (CaAlg) on membranes is constructed. The innermost PCA enables the adhesive hydrogel to tightly adhere to the membranes. The outermost CaAlg defends membranes from oil fouling. The gradient distribution and uniform integration of PCA/CaAlg guarantee an excellent stability. Membranes decorated with the adhesive hydrogel demonstrate superhydrophilicity, anti‐fouling to various oils, and anti‐abrasion to external damaging. The membranes achieve ultra‐stable and efficient separation of surfactant‐stabilized oil‐in‐water emulsions and crude oil/water mixture with the most advanced cycling ability of ≈100% flux recovery and nearly zero irreversible oil fouling. This study provides a new strategy for designing anti‐oil‐fouling membranes toward practical oil/water separation applications.

Microporous polymer adsorptive membranes with high processing capacity for molecular separation

Abstract: Trade-off between permeability and nanometer-level selectivity is an inherent shortcoming of membrane-based separation of molecules, while most highly porous materials with high adsorption capacity lack solution processability and stability for achieving adsorption-based molecule separation. We hereby report a hydrophilic amidoxime modified polymer of intrinsic microporosity (AOPIM-1) as a membrane adsorption material to selectively adsorb and separate small organic molecules from water with ultrahigh processing capacity. The membrane adsorption capacity for Rhodamine B reaches 26.114 g m-2, 10-1000 times higher than previously reported adsorptive membranes. Meanwhile, the membrane achieves >99.9% removal of various nano-sized organic molecules with water flux 2 orders of magnitude higher than typical pressure-driven membranes of similar rejections. This work confirms the feasibility of microporous polymers for membrane adsorption with high capacity, and provides the possibility of adsorptive membranes for molecular separation.

Synergistic Design of Enhanced π–π Interaction and Decarboxylation Cross-Linking of Polyimide Membranes for Natural Gas Separation

Abstract: Conventional gas separation membranes made of glassy polymers often exhibit increased segmental motion and reduced selectivity when exposed to high-pressure condensable gases. Decarboxylation cross-linking can effectively improve the plasticization resistance and gas permeability of polymer membranes, but this usually comes at the expense of the gas selectivity. In this work, enhanced π–π interactions and decarboxylation cross-linking are synergistically designed among polymer chains by introducing benzimidazole units and carboxyl side groups into the 6FDA-PABZ:DABA polyimide (PI-Im-COOH). After the thermal treatment, a cross-linked structure was formed through the decarboxylation reaction as confirmed by FTIR spectroscopy and thermal analysis. The π–π interactions between benzimidazole moieties were simultaneously enhanced as proven by WAXD, UV–vis, and fluorescence spectroscopy. The gas separation performance and plasticization resistance of the decarboxylated PI-Im-COOH membranes were enhanced significantly. In particular, the decarboxylated PI-Im-COOH membranes exhibit higher gas selectivities for CO2/CH4 and CO2/N2 gas pairs than the previously reported decarboxylated membranes. The PI-Im-COOH membrane that was thermally treated at 450 °C for 2 h showed outstanding CO2/CH4 separation performance with a CO2 permeability of 685.1 barrer and a CO2/CH4 selectivity of 38.1, surpassing the 2008 Robeson upper bound. The synergistic design of enhanced π–π interactions and decarboxylation cross-linking proves to be a facile strategy to regulate interchain interactions and distances to achieve a high performance for natural gas separation.

Polyaniline nanofiber array supported ultrathin polyamide membrane for solar-driven volatile organic compounds removal

Abstract: Water-soluble volatile organic compounds (VOCs) widely exist in wastewater and are among the most difficult-to-treat contaminants. Purification and removal of VOCs rely on energy-intensive technologies like distillation, reverse osmosis, or...

Conservation tillage regulates the assembly, network structure and ecological function of the soil bacterial community in black soils

Abstract: Traditional tillage represents a serious threat to the stability of soil ecosystems. Understanding the response mechanisms of soil microbial community assembly to different tillage practices is a major topic of soil ecological research. Here, we investigated the bacterial community structures and assembly in bulk and rhizosphere soils of soybeans grown under traditional tillage (moldboard plow, MP) and two conservation tillage practices, namely, no-tillage (NT) and ridge tillage (RT), using high-throughput sequencing methods. Compared with MP, NT and RT increased the relative abundances of nitrifying bacteria of Nitrosospira sp. and the nitrogen-fixing bacteria of Mesorhizobium sp., Bradyrhizobium sp. and Burkholderia sp., but decreased the abundance of carbon-degrading bacteria, especially Blastococcus sp., Streptomyces sp. and Sphingomonas sp. The altered functional bacteria were mostly affiliated with biomarkers and keystone taxa in the NT and RT networks. For the results of network properties and assembly processes, we found that NT and RT habited a more stable bacterial network structure and a lower homogenizing dispersal value. Soil pH was the primary factor regulating both the bacterial community structures and assembly processes under the three tillage practices. The soil bacterial community structures and assembly processes were profoundly altered by tillage practices. The changes in functional bacteria indicated that conservation tillage might contribute to soil carbon sequestration, while stimulating nitrogen fixation and nitrification.

Elevated atmospheric CO2 alters the microbial community composition and metabolic potential to mineralize organic phosphorus in the rhizosphere of wheat

Abstract: Understanding how elevated atmospheric CO2 (eCO2) impacts on phosphorus (P) transformation in plant rhizosphere is critical for maintaining ecological sustainability in response to climate change, especially in agricultural systems where soil P availability is low.This study used rhizoboxes to physically separate rhizosphere regions (plant root-soil interface) into 1.5-mm segments. Wheat plants were grown in rhizoboxes under eCO2 (800 ppm) and ambient CO2 (400 ppm) in two farming soils, Chromosol and Vertosol, supplemented with phytate (organic P). Photosynthetic carbon flow in the plant-soil continuum was traced with 13CO2 labeling. Amplicon sequencing was performed on the rhizosphere-associated microbial community in the root-growth zone, and 1.5 mm and 3 mm away from the root.Elevated CO2 accelerated the mineralization of phytate in the rhizosphere zones, which corresponded with increases in plant-derived 13C enrichment and the relative abundances of discreet phylogenetic clades containing Bacteroidetes and Gemmatimonadetes in the bacterial community, and Funneliformis affiliated to arbuscular mycorrhizas in the fungal community. Although the amplicon sequence variants (ASVs) associated the stimulation of phytate mineralization under eCO2 differed between the two soils, these ASVs belonged to the same phyla associated with phytase and phosphatase production. The symbiotic mycorrhizas in the rhizosphere of wheat under eCO2 benefited from increased plant C supply and increased P access from soil. Further supportive evidence was the eCO2-induced increase in the genetic pool expressing the pentose phosphate pathway, which is the central pathway for biosynthesis of RNA/DNA precursors.The results suggested that an increased belowground carbon flow under eCO2 stimulated bacterial growth, changing community composition in favor of phylotypes capable of degrading aromatic P compounds. It is proposed that energy investments by bacteria into anabolic processes increase under eCO2 to level microbial P-use efficiencies and that synergies with symbiotic mycorrhizas further enhance the competition for and mineralization of organic P. Video Abstract.

Benzyl-Induced Crosslinking of Polymer Membranes for Highly Selective CO2/CH4 Separation with Enhanced Stability

Abstract: Chemical crosslinking is the most commonly used solution to address the issue of poor structure stability and low plasticization resistance of polymer membranes for gas separation. However, the general crosslinking route requires the introduction of reactive groups into the polymer chain and is very likely to weaken the separation performance of membranes. Here, we report a new and nondestructive benzyl-induced crosslinking strategy. Owing to the high reactivity and wide existence in most polymers, the benzyl-induced crosslinking could universally happen in unmodified polymer membranes. Our crosslinked polyimide membrane exhibits unprecedented performance with a CO2/CH4 selectivity > 70, three times that of non-crosslinked membranes, and with CO2 plasticization pressures above 42 bar, the highest value among the polyimide membranes reported so far. The comprehensive performance surpasses the state-of-the-art 2018 upper bound for mixed gas. Our work provides a facile and reliable route for constructing polymer membranes with highly improved stability and performance.

Soil microbial metabolism on carbon and nitrogen transformation links the crop-residue contribution to soil organic carbon

Abstract: The beneficial effect of crop residue amendment on soil organic carbon (SOC) stock and stability depends on the functional response of soil microbial communities. Here we synchronized microbial metagenomic analysis, nuclear magnetic resonance and plant-15N labeling technologies to gain understanding of how microbial metabolic processes affect SOC accumulation in responses to differences in N supply from residues. Residue amendment brought increases in the assemblage of genes involved in C-degradation profiles from labile to recalcitrant C compounds as well as N mineralization. The N mineralization genes were correlated with the C and N accumulation in the particulate and mineral-associated C pools, and plant-derived aliphatic forms of SOC. Thus, the combined C and N metabolic potential of the microbial community transforms residue into persistent organic compounds, thereby increasing C and N sequestration in stable SOC pools. This study emphasizes potential microbially mediated mechanisms by which residue N affects C sequestration in soils.

Thin Films Based on Polyimide/Metal–Organic Framework Nanoparticle Composite Membranes with Substantially Improved Stability for CO2/CH4 Separation

Abstract: As one of the gas separation membranes, the thin-film nanocomposite (TFN) membrane can effectively reduce gas transport resistance and improve gas permeance. However, due to the high mobility of the chain in the thin film, it is still a great challenge to realize the TFN membrane with stable separation performance. In this work, we report a less destructive and efficient cross-linking strategy based on metal-ion coordination to improve the stability of the TFN membrane for CO2/CH4 separation. The selective layer is made of carboxylated polyimide as a matrix and UiO-66 nanoparticles (diameters of ∼50 nm) as fillers. By simply immersing TFN membranes in Cu(NO3)2 solution, coordination bonds are successfully constructed between Cu2+ and carboxyl groups (−COOH). The cross-linked TFN membranes exhibit high CO2/CH4 selectivity of up to 29–35 with CO2 permeance of 110–350 GPU, outperforming most previously reported membranes. Moreover, the plasticization pressure of the cross-linked membranes improves from 0.3–0.9 to 0.9–1.5 MPa, higher than most reported asymmetric and hollow fiber membranes. In the CO2/CH4 (50:50 v/v) mixed-gas permeation tests, the cross-linked membranes retain constant CO2/CH4 selectivity at 23.9–25.2 with increasing mixed-gas feed pressure. The cross-linked membranes also demonstrate stable CO2/CH4 selectivity in the range of 27.2–31.2 within 100 h of testing time under a 1.0 MPa CO2 partial pressure.

Ultrasmall Cu3(PO4)2 Nanoparticles Reinforced Hydrogel Membrane for Super-antifouling Oil/Water Emulsion Separation.

Abstract: Membrane fouling is a persistent and crippling challenge for oily wastewater treatment due to the high susceptibility of membranes to contamination. A feasible strategy is to design a robust and stable hydration layer on the membrane surface to prevent contaminates. A hydrogel illustrates a distinct category of materials with outstanding antifouling performance but is limited by its weak mechanical property. In this research, we report a reinforced hydrogel on a membrane by in situ growing ultrasmall hydrophilic Cu3(PO4)2 nanoparticles in a copper alginate (CuAlg) layer via metal-ion-coordination-mediated mineralization. The embeddedness of hydrophilic Cu3(PO4)2 nanoparticle with a size of 3-5 nm endows the CuAlg/Cu3(PO4)2 composite hydrogel with enhanced mechanical property as well as reinforced hydrate ability. The as-prepared CuAlg/Cu3(PO4)2 modified membrane exhibits a superior oil-repulsive property and achieves a nearly zero flux decline for separating surfactant stabilized oil-in-water emulsions with a high permeate flux up to ∼1330 L m-2 h-1 bar-1. Notably, it is capable of keeping similar permeate flux for both pure water and oil-in-water emulsions during filtration, which is superior to the currently reported membranes, indicating its super-antifouling properties.

Soil microbial metabolism on carbon and nitrogen transformation links the crop-residue contribution to soil organic carbon

Abstract: The beneficial effect of crop residue amendment on soil organic carbon (SOC) stock and stability depends on the functional response of soil microbial communities. Here we synchronized microbial metagenomic analysis, nuclear magnetic resonance and plant-15N labeling technologies to gain understanding of how microbial metabolic processes affect SOC accumulation in responses to differences in N supply from residues. Residue amendment brought increases in the assemblage of genes involved in C-degradation profiles from labile to recalcitrant C compounds as well as N mineralization. The N mineralization genes were correlated with the C and N accumulation in the particulate and mineral-associated C pools, and plant-derived aliphatic forms of SOC. Thus, the combined C and N metabolic potential of the microbial community transforms residue into persistent organic compounds, thereby increasing C and N sequestration in stable SOC pools. This study emphasizes potential microbially mediated mechanisms by which residue N affects C sequestration in soils.

Microbial communities in the diagnostic horizons of agricultural Isohumosols in northeast China reflect their soil classification

Abstract: Soil depth greatly affects soil microorganisms due to the intensive changes in soil physical and chemical properties along soil profile. However, little is known about microbial communities in diagnostic horizons of soil profiles among different soil types, which is the key to understanding the biogeochemical cycling in deep soils. Herein, we collected soil samples from eight agricultural fields across Heilongjiang Province of China, which belong to two suborders of Isohumosols (Ustic and Udic), based on the diagnostic horizons. The microbial community abundances, diversities and structures were comparatively investigated using qPCR and high-throughput sequencing methods. Results showed that the abundances of bacteria, archaea, and fungi consistently decreased more than by 90% in C horizon (parent material horizons) compared with those in Ah horizons (humus horizons). In items of alpha diversity, the fungal diversity decreased by>50%, while archaeal diversity increased by more than two folds. The bacterial diversity varied along soil depths at different sites. In addition, all soil microbial community structures were obviously divided into Ustic and Udic groups, and a distinct succession of microbial communities was detected from Ah horizons to C horizons at individual sites. Moreover, compared to Ah horizons, the difference of microbial community structure between Ustic and Udic Isohumosols was greater in C horizons. Canonical correspondence analysis (CCA) and random forest (RF) analysis revealed that pH was the most important soil factor regulating the microbial communities among all tested edaphic variables. More importantly, using machine-learning methods, we found that soil microbial communities can be used to accurately predict two suborders of Isohumosols and diagnostic horizons. Overall, the findings of this study highlight that the microbial data of diagnostic horizons can be served as quantitative indices for the soil classification, and this conclusion needs to be verified in the future research using more soil types.

Ultrapermeable Polyamide Nanofiltration Membrane Formed on a Self-Constructed Cellulose Nanofibers Interlayer

Abstract: • TFC-PA NF membrane with in-situ formed cellulose nanofibers as interlayer is prepared via interfacial polymerization. • The membrane exhibits a pure water permeance up to 35.7 Lm −2 h −1 bar −1 and a high Na 2 SO 4 rejection >97%. • The membrane shows a high stability to applied pressure and long filtration time. • The membrane shows an obvious improvement of antifouling performance. Improving the water permeance of polyamide nanofiltration (NF) membranes without the simultaneous loss of rejection is highly desired but remains a challenge. In this work, we prepared an ultrapermeable polyamide NF membrane containing an in-situ -formed cellulose nanofibre (CN) interconnected network film between a polyamide active layer and ultrafiltration (UF) membrane support through direct addition of the CN to a piperazine aqueous solution for interfacial polymerization. Such in-situ -formed CN interlayer with high porosity can provide a large number of channels for water transport. Compared with the polyamide active layer directly supported by the UF support, the polyamide active layer supported by the CN interlayer can contribute a more effective area for water permeation. Consequently, the polyamide NF membrane exhibited a pure water permeance up to 35.7 L m −2 h −1 bar −1 while maintaining salt rejection to Na 2 SO 4 of >97%. This permeance is 2.5 times greater than that of the membrane without the CN interlayer.

Crop Residue Return Rather than Organic Manure Increases Soil Aggregate Stability under Corn–Soybean Rotation in Surface Mollisols

Abstract: Fertilization practices change soil organic carbon content and distribution, which is relevant to crop rotation and soil aggregates. However, how fertilization management under corn–soybean rotation affects soil organic carbon and aggregate stability at different soil depths in Mollisols is unclear. The effects of 6–yr fertilization under corn–soybean rotation on aggregate stability, soil organic carbon content and storage, and size distribution in soil aggregates were investigated. Five different fertilization practices were carried out in 2013: corn and soybean without fertilizer; corn with chemical fertilizer, soybean without fertilizer; corn with chemical fertilizer, soybean without fertilizer, returning the corn and soybean residues; corn and soybean with chemical fertilizer; and corn with chemical fertilizer, soybean with farmyard manure. Compared with corn and soybean without fertilizer, returning the corn and soybean residues increased bulk SOC content, and enhanced mean weight diameter and geometric mean diameter values at 0–10 cm because of increased water–stability aggregates (WSA) larger than 2 mm proportion and decreased WSA<0.053mm proportion. Simultaneously, corn with chemical fertilizer and soybean with farmyard manure increased bulk soil organic carbon content but reduced mean weight diameter and geometric mean diameter values at 0–20 cm due to increased WSA<0.053mm proportion and decreased WSA>2mm proportion. Altogether, the application of consecutive returning crop residues and chemical fertilizer in alternate years is the most favorable approach for soil organic carbon accumulation and aggregate stability at 0–10 cm under corn–soybean rotation in Mollisols.