PBAT/PLA food packaging film containing sodium dehydroacetate-loaded diatomite as an antibacterial agent: Fabrication, water-gas regulation and long-acting antimicrobial mechanism.

Biodegradable food packaging films with good antimicrobial properties are highly sought after for prolonging the shelf-life of fruits and vegetables whilst minimizing waste streams originating from the food sector. In this work, a series of PBAT/PLA food packaging films containing sodium dehydroacetate-loaded diatomite (SD/D) as an antimicrobial agent were fabricated. Structural analyses showed that the sodium dehydroacetate was incorporated into the pores of the diatomite. A uniform dispersion of SD/D in the composite films effectively enhanced water and gas permeability, whilst also giving the films good mechanical properties. The slow release of SD endowed the composite films with long-acting antibacterial ability (>90 % bacteriostasis rate for E. coli and >85 % bacteriostasis rate for S. aureus). The composite films were able to effectively maintain the quality of banana fruits during storage at room temperature, encouraging their use in food applications where non-biodegradable petrochemical-derived packaging films have traditionally been used.

Water-resistant and pyknotic recyclable waste-cotton-derived bio-polyurethane-coated controlled-release fertilizer: Improved longevity, mechanism and application.

Reasonably utilize the recyclable waste-cotton resource to develop the bio-polyurethane coatings had aroused more and more environmental interests recently. However, the terrible water resistance and porousness of the waste-cotton-derived bio-polyurethane coating caused the rapid nutrients release. In this work, the water-resistant and pyknotic cotton-fibre-derived coated-ureas (WPCUs) were fabricated with the recyclable low-cost waste-cotton-derived materials. The dramatically enhanced pyknotic and water-resistant characteristics of the WPCUs coatings can be obtained by the three-dimensional computerized tomography (2.33 to 1.19 %) and the water contact angle. The enhanced elasticity and the decreased water absorption were also vital to enhance the controlled-release performance. The accompanying controlled-release performance of the WPCUs was obviously improved (<2 h to 58.43 days). The modified WPCU75-10 with 4.0 % coating content exhibits the excellent controlled-release performance compared to the unmodified WPCU0-0. The controlled release mechanism can be clarified: The air column inside of the "small and few" micropores in the WPCUs coating only allow the gaseous water molecules to slowly penetrate and dissolve the inner urea cores (rather than liquid water). The obviously increased oilseed rape yield (128.75 %) showed the dependable agricultural application of the WPCUs. This work provides the resultful approach to develop the eco-friendly recyclable waste-plant-derived controlled-release fertilizers.

POSS(epoxy)8 reinforced poly (butylene adipate-co-terephthalate)/lignin biodegradable films: Fabrication, enhanced mechanical properties and UV aging resistance.

To reduce the white pollution, the eco-friendly biodegradable poly (butylene adipate-co-terephthalate) (PBAT)-based films had attracted increasing interests worldwide. However, the high-cost of the PBAT had limited the large-scale development and application. In this work, 10 wt% low-cost lignin was introduced into the PBAT to prepare composite films by melt blending and blow molding, and the POSS(epoxy)8 was selected as the compatibilizer to improve the compatibility of PBAT and lignin. The maximum tensile strength and the nominal strain at break subsequently increased by 48.2 % and 21.4 % respectively, while the water vapor permeability enhanced by 9.9 %. Furthermore, the UV aging resistance of PBAT/lignin films were significantly improved, with only 1 wt% POSS(epoxy)8 content. This work provides an efficient strategy to foster the end-user confidence in the low-cost and eco-friendly biodegradable polymer materials with efficient performance.

Ammonium Sulfite Slurry from Ammonia-Based Desulfurization Activates Water-Soluble Humic Substances from Lignite: Performance, Application, and Mechanism.

Both ammonium sulfite slurry (ASS) from ammonia-based desulfurization and lignite are waste materials with low value. In this work, an innovative method was developed by applying ASS in lignite activation to produce water-soluble humic substances (WHSs) with a high bioactivity and economic value. The optimal activation method was to mix lignite and ASS at a 4:1-liquid-solid ratio by vortex blender and then oscillate it for 30 min at 25 °C. Compared with that of the unactivated lignite (UAL), the yield of WHSs from activated lignite (AL) increased by 42.72%. WHSs from AL consisted of a large number of aliphatic carbons with low molecular weight and functional groups such as amides, amines, sulfonic acid groups, C-O, and so forth. Moreover, WHSs from AL at lower concentrations (2 mg/L) has a more obvious root-elongation-promoting effect than WHSs from UAL (10 mg/L). Activation experiment with the lignite-related model compounds revealed that ASS caused the breakage of Caliph-O, Caliph-Caliph, and Carom-Caliph linkages between aromatic rings. These findings provide a theoretical basis for the development of green and sustainable technologies for the beneficial reuse of ASS and lignite in agriculture.

Preparation and Nutrient Release Characteristics of Liquefied Apple Tree Branche-Based Biocoated Large Tablet Urea.

Controlled-release fertilizers (CRFs) could improve crop yield and fertilizer use efficiency. However, the coating materials of conventional CRFs are mainly derived from petrochemical products, which are expensive and nondegradable, bringing potential environmental pollution. Therefore, using sustainable bio-based materials is the development direction. In this study, large tablet urea (LTU) was prepared using physical extrusion technology. The economical and biodegradable liquefied apple tree branch bio-based coating material was used to coat LTU, obtaining large tablet CRFs (LTCRUs). Also, the optimum proportion of liquefaction of apple tree branches modified by castor oil was studied. The specific surface area, surface morphology, and FTIR of LTCRU were characterized. The results showed that the surface of the LTCRU was the most smooth and the LTCRU modified with 30% castor oil presented the best controlled-release characteristics. The specific surface area of LTCRU was one-third of that of traditional small-particle fertilizers, which indicated that reducing the using dosage of coating materials is economical. Overall, this work provided theoretical and technical supports for the industrialization of biocoated superlarge tablet urea, which is conducive to the green development of agriculture.

Development of multifunctional copper alginate and bio-polyurethane bilayer coated fertilizer: Controlled-release, selenium supply and antifungal.

Bio-based controlled release fertilizers (BCRFs) are cost-effective and renewable thus gradually replacing petroleum-based controlled release fertilizers (CRFs). However, most of the study mainly focused on modifying BCRFs to improve controlled-release performance. It is necessary to further increase the functionality of BCRF for expanding the application. A multifunctional double layered bio-based CRF (DCRF) was prepared. Urea was used as the core of fertilizer, bio-based polyurethane was used as the inner coating, and sodium alginate and copper ions formed the hydrogel as the outer coating. In addition, mesoporous silica nanoparticles loaded with sodium selenate was used to modify the sodium alginate hydrogel (MSN@Se hydrogel). The results showed that the nitrogen longevity of the DCRF was much better than that of urea and BCRF. The selenium nutrient longevity of the DCRF was 40 h, much longer than that of sodium selenate. The DCRF improved the yield and nutritive value of cherry radish (Raphanus sativus L. var.radculus pers) with the elevated contents of selenium, an essential trace element. Moreover, the DCRF showed inhibitory effect on Fusarium oxysporum Schltdl. and could resist soil-borne fungal diseases continuously. Overall, this multifunctional fertilizer has great potential for expanding the use of BCRFs for sustainable development of agriculture.

Bio-based Polyurethane Based on a Dynamic Covalent Network with Damage Tolerance for Controlled Release of Fertilizers.

Bio-based polyurethanes are promising for the controlled release of nutrients and fertilizers, but their toughness and plasticity need to be improved. We developed a smooth, dense, elastic, and indestructible bio-based polyurethane (BPU) coating with a nutrient controlled release ∼150% superior, a tensile strength ∼300% higher, and a toughness ∼1200% higher than those for the original BPU coating. Through a one-step reaction of soybean oil polyols (accounting for more than 60%), isocyanate, and benzil dioxime, the dynamic covalent network based on oxime-carbamate replaces part of irreversible covalent cross-linking. The dynamic fracture-bonding reaction in the modified coating BPU can effectively promote the hydrogen bond recombination and oxime-carbamate chain migration in the coating process, which avoids the structural defects caused by coating tear and fertilizer collision. This work provides a simple and versatile strategy for building controlled-release fertilizer coatings.

Prediction Model of Photodegradation for PBAT/PLA Mulch Films: Strategy to Fast Evaluate Service Life.

Eco-friendly biodegradable PBAT/PLA mulch films are attracting increasing interest in sustainable agricultural production. However, currently, little is known about the service life for the PBAT/PLA mulch films. Herein, PBAT/PLA mulch films are subjected to indoor UV-accelerated degradation (UAD) experiments and field cultivation environment degradation (CED) experiments to systematically investigate the relationship between UAD and CED processes. Results demonstrate that 10 days of indoor UAD treatment corresponds to around 120 days aging under outdoor CED conditions. Using eight PBAT/PLA evaluation indicators (haze, elongation at break, tensile strength, gel content, light transmittance, polydispersity index, Mn, Mw), we established a service life prediction model for PBAT/PLA mulch films based on short-term indoor UAD experiments, which could accurately estimate the long-term service life of the mulch films in the field. In particular, using the haze value, near-perfect correlation (R2 = 0.995 for eq. 1 and R2 = 0.993 for eq. 2) was found between CED days and UAD days. The establishment of these reliable predictive models for the service lifetime of PBAT/PLA mulch films will avoid the undesirable premature breakdown during crop growth, thus fostering end-user confidence in eco-friendly biodegradable mulch films.

Optimizing interfacial adhesion in PBAT/PLA nanocomposite for biodegradable packaging films.

Biodegradable films poly(butylene adipate-co-butylene terephthalate) (PBAT)/poly(lactic acid) (PLA) incorporated with nano-polyhedral oligomeric silsesquioxane (POSS(epoxy)8) as a reactive compatibilizer were developed by melt processing. Structural, morphological, mechanical, and gas permeability properties of the films were determined. 1H NMR and GPC demonstrated that the POSS(epoxy)8 was chemically bound at the PBAT/PLA boundary phase via an epoxide ring opening reaction. SEM micrographs of impact fracture surfaces demonstrated the POSS(epoxy)8 improved interfacial adhesion between PBAT and PLA matrix. The mechanical properties of the PBAT/PLA films containing POSS(epoxy)8 were enhanced relative to pristine PBAT/PLA films. The water vapor, CO2 and O2 permeability of the PBAT/PLA films were improved by POSS(epoxy)8 addition. PBAT/PLA films containing POSS(epoxy)8 were shown to be superior to pristine PBAT/PLA films and polyethylene films in food storage tests. Results suggest that POSS(epoxy)8 addition during PBAT/PLA film production offers a simple strategy for the production of high performance biodegradable plastic packaging films.

Activation of Humic Acid in Lignite Using Molybdate-Phosphorus Hierarchical Hollow Nanosphere Catalyst Oxidation: Molecular Characterization and Rice Seed Germination-Promoting Performances.

Although solid-phase activation of lignite using a nanocatalyst has great potential in producing low-cost and sustainable humic acid, the large-scale application of this technology still faces challenges because of the high price and toxicity of the nanocatalyst. Additionally, the specific molecular components of humic acid in activated lignite remain unknown. In this work, a multifunctional molybdate-phosphorus hierarchical hollow nanosphere (Mo-P-HH) catalyst was successfully manufactured by a simple way followed by phosphorization. In comparison with a commercial Pd/C catalyst, the multifunctional Mo-P-HH catalyst was more effective in producing water-soluble humic acid with small molecular functional groups from lignite via solid-phase activation. Moreover, Fourier transform ion cyclotron resonance mass spectrometry revealed the molecular compositions of humic acid in activated lignite. Compared with that from raw lignite, the humic acid after Mo-P-HH activation had less aromatic structure but higher content of lipids, proteins, amino sugar, and carbohydrates. In addition, the activated humic acid simulated seed germination and seedling growth. Therefore, this study provided a high-performance hierarchical hollow nanocatalyst for activation of humic acid and also offered the theoretical basis for the application of humic acid in agriculture.

Cu(II)-Based Water-Dispersible Humic Acid: Synthesis, Characterizations, and Antifungal and Growth-Promoting Performances.

The complex synthesis process, low utilization, and single function of fungicides have seriously hindered the development of fungicides in resistance to rice sheath blight. Here, an inexpensive and multifunctional Cu(II)-based water-dispersible humic acid (Cu-WH) fungicide with growth-promoting ability was developed with a simple method. A 3D molybdate carbon hierarchical nanosphere (MoO2-C-HN) catalyst was successfully synthesized using a green route and applied in a solid-phase activation of lignite to obtain water-dispersible humic acid. Cu(II)-based water-dispersible humic acid (Cu-WH) was then formed through a simple reaction of Cu(II) and the humic acid. The resultant Cu-WH showed strong antifungal performance against Rhizoctonia solani in laboratory incubation experiments. After being treated with Cu3-WH (0.1 mg L-1), the control efficiency of rice sheath blight at 1, 3, and 5 days after infection was 90.54%, 78.96%, and 66.31%, respectively. It also enhanced the water-holding capacity of the substrate and thus effectively improved the growth of rice seedlings. In comparison to commercial rice seedling substrate, the substrate treated with 8 wt % of Cu3-WH increased plant height, stem diameter, fresh weight, and chlorophyll content by 19.23%, 35.91%, 14.52%, and 42.85%, respectively. The newly developed Cu-WH thus can be used as a novel low-cost efficient fungicide and growth stimulator to treat rice sheath blight as well as to increase rice production.

Molecular Composition of Size-Fractionated Fulvic Acid-Like Substances Extracted from Spent Cooking Liquor and Its Relationship with Biological Activity.

The treatment of spent cooking liquor is critical for clean production of pulp and paper industry. There is a compelling need to develop a cost-effective and green technology for reuse of organic matter in spent cooking liquor to mitigate the negative impacts on the environment. The objective of this study is to examine the chemical structure of fulvic acid-like substances extracted from spent cooking liquor (PFA) and their relationship with bioactivity in plant growth. Compared with the benchmark Pahokee peat fulvic acid (PPFA), PFA has less aromatic structure, but higher content of lignin, carbohydrates, and amino acid. After fractionation, protein/amino proportion decreased with increasing molecular weight, but the aromaticity increased. Under salt stress, rice seedling growth was promoted by PFA with low molecular weight (<5 kDa), but inhibited by fraction with high molecular weight (>10 kDa). Principal component analysis suggested that promoted growth was more related with chemical structure (O- and N-alkyl moieties) than with molecular weight. This study provided the theoretical basis for development of an innovative green technology of sustainable reuse of spent cooking liquor in agriculture.

Activation of fulvic acid-like in paper mill effluents using H2O2/TiO2 catalytic oxidation: Characterization and salt stress bioassays.

Increasing environmental concerns about organic waste in paper mill effluents demand alternative wastewater management technology. We reported novel activation of fulvic acid-like in paper mill effluents using hydrogen peroxide (H2O2) as oxidizer and titanium oxide (TiO2) as catalyst. Spectroscopic characteristics of fulvic acid-like in paper mill effluents before and after activation (PFA and PFA-Os, respectively) were compared with a benchmark fulvic acid extracted from leonardite (LFA). Results indicated that PFA-Os exhibited less lignin structures, more functional groups and lower molecular weight than PFA, sharing much similarity with LFA. Among PFA-Os with varying degrees of oxidation, PFA-O-3 activated with 1:2 vol ratio of paper mill effluent and 30% H2O2 for 20 min digestion at 90 °C stands out to be the optimal for further examination of its biological activity. Bioassays with rice seed/seedling indicated that applications of LFA at 2-5 mg-C/L and PFA-O-3 at 60-100 mg-C/L significantly increased rice seed germination rate and seedling growth under salt stress imposed with 100 mM NaCl. The mechanism was mainly through reduced oxidative damage via activation of antioxidative enzymes and lipid peroxidation. This study provides the needed technical basis of safer and cleaner technologies for innovative management of paper mill effluents.

Magnetic-Sensitive Nanoparticle Self-Assembled Superhydrophobic Biopolymer-Coated Slow-Release Fertilizer: Fabrication, Enhanced Performance, and Mechanism.

Although commercialized slow-release fertilizers coated with petrochemical polymers have revolutionarily promoted agricultural production, more research should be devoted to developing superhydrophobic biopolymer coatings with superb slow-release ability from sustainable and ecofriendly biomaterials. To inform the development of the superhydrophobic biopolymer-coated slow-release fertilizers (SBSF), the slow-release mechanism of SBSF needs to be clarified. Here, the SBSF with superior slow-release performance, water tolerance, and good feasibility for large-scale production was self-assembly fabricated using a simple, solvent-free process. The superhydrophobic surfaces of SBSF with uniformly dispersed Fe3O4 superhydrophobic magnetic-sensitive nanoparticles (SMNs) were self-assembly constructed with the spontaneous migration of Fe3O4 SMNs toward the outermost surface of the liquid coating materials ( i.e., pig fat based polyol and polymethylene polyphenylene isocyanate in a mass ratio 1.2:1) in a magnetic field during the reaction-curing process. The results revealed that SBSF showed longer slow-release longevity (more than 100 days) than those of unmodified biopolymer-coated slow-release fertilizers and excellent durable properties under various external environment conditions. The governing slow-release mechanism of SBSF was clarified by directly observing the atmosphere cushion on the superhydrophobic biopolymer coating using the synchrotron radiation-based X-ray phase-contrast imaging technique. Liquid water only contacts the top of the bulges of the solid surface (10.9%), and air pockets are trapped underneath the liquid (89.1%). The atmosphere cushion allows the slow diffusion of water vapor into the internal urea core of SBSF, which can decrease the nutrient release and enhance the slow-release ability. This self-assembly synthesis of SBSF through the magnetic interaction provides a strategy to fabricate not only ecofriendly biobased slow-release fertilizers but also other superhydrophobic materials for various applications.

Bio-based Large Tablet Controlled-Release Urea: Synthesis, Characterization, and Controlled-Released Mechanisms.

To improve nitrogen (N) use efficiency and minimize environmental pollution caused by fertilizer overuse, novel bio-based large tablet controlled-release urea (LTCRU) was prepared using bio-based coating materials to coat large tablet urea (LTU) derived from urea prills (U). Nano fumed silica (NFS) was added to the bio-based coating materials to improve the slow-release properties. The surface area of the LTU and U was measured by three-dimensional scanning. In comparison to U, LTU had a smaller surface area/weight ratio, which can reduce the coating materials. Scanning electron microscopy analysis showed that the addition of NFS in bio-based coating materials reduced the porosity of the coating shells of LTCRUs and, thus, enhanced the N release longevity of the controlled-released fertilizer. Dependent upon the pores on the coating shells of LTCRU, two N release patterns were revealed. Because of the good release characteristics, the novel LTCRU shows great potential to support sustainable agricultural production.

Innovative Linear Low Density Polyethylene Nanocomposite Films Reinforced with Organophilic Layered Double Hydroxides: Fabrication, Morphology and Enhanced Multifunctional Properties.

Herein, we reported the successful development of novel nanocomposite films based on linear low density polyethylene (LLDPE) with enhanced anti-drop, optical, mechanical, thermal and water vapor barrier properties by introducing organophilic layered double hydroxides (OLDHs) nanosheets. OLDHs loadings were varied from 0-6 wt.%. Structural analyses using the Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) indicated that the OLDHs nanosheets were homogeneously dispersed with an ordered alignment in the LLDPE matrix. The LLDPE film containing 2 wt.% OLDHs (denoted as OLDHs-2) showed the optimal mechanical, thermal and water vapor barrier properties, whilst the anti-drop and optical performance of the films improved with increasing OLDHs content. The enhanced antidrop properties of the composite films relative to pristine LLDPE can be expected to effectively reduce agricultural losses to disease when the films are applied as agricultural films, whilst the superior light transmittance and water-retaining properties of the composite films will boost agricultural production. Results presented suggest that multifunctional LLDPE/OLDHs nanocomposites show great promise as low cost agricultural plastic films.

Scale-Up Fabrication of Biodegradable Poly(butylene adipate-co-terephthalate)/Organophilic-Clay Nanocomposite Films for Potential Packaging Applications.

The development of biodegradable packing materials is a global priority due to the huge volumes of plastic refuse entering landfills and the environment. In this study, a series of biodegradable nanocomposite films based on poly(butylene adipate-co-terephthalate) (PBAT) and reinforced with an organophilic layered double hydroxide (OLDH) were scale-up fabricated. The OLDH nanosheets with a basal spacing of 4.07 nm were presynthesized on a large-scale by solvent-free high-energy ball milling. All of the PBAT/OLDH nanocomposite films (0.5-4 wt % OLDH) showed a uniform dispersion of OLDH nanosheets in the PBAT matrix. A PBAT/OLDH film containing 1 wt % OLDH (denoted herein as OLDH-1) demonstrated outstanding thermal, optical, mechanical, and water vapor barrier properties compared with a pure PBAT film (OLDH-0), including a 37% reduction in haze and a 41.9% increase in nominal tensile strain at break dramatically. Furthermore, the food packaging measurement revealed that the OLDH-1 film showed a better packaging effect than the pure PBAT film and commercial polyethylene packing materials. The feasibility of scale-up manufacture and the excellent processability, manufacturing scalability, mechanical performance, optical transparency, water vapor barrier properties, and food packaging performance of the PBAT/OLDH nanocomposite films encourage their future application as biodegradable packaging films.

Biomimetic Superhydrophobic Biobased Polyurethane-Coated Fertilizer with Atmosphere "Outerwear".

The development of efficient biobased controlled-release fertilizers has captured much research attention because of the environmental concerns and food scarcity problems. In this work, a biomimetic superhydrophobic biobased polyurethane-coated fertilizer (SBPF) was successfully fabricated by increasing surface roughness and reducing surface energy of polyurethane (PU) coating. The green PU coating was synthesized from low-cost, biodegradable, and renewable cottonseed oil. The nutrient release longevity of SBPF revealed 2-fold enhancement compared with the normal biobased PU-coated fertilizer (BPF). The significant improvement of nutrient release characteristics can be attributed to the atmosphere "outerwear" which ensured the nonwetting contact of water with superhydrophobic surfaces in gas state instead of in liquid state. The new concept introduced in this study can inform the development of the next generation of biobased controlled release fertilizers.