Direct degradation of Bisphenol A from aqueous solution by active red mud in aerobic environment.

As industrial waste from aluminum production, red mud (RM) poses a severe threat to the local environment that needs to be appropriately utilized. The activation of iron oxide, which is abundant in RM, improves its effectiveness as a catalytic material for the degradation of organic pollutants. This study developed a novel activation approach by adding dithionite citrate bicarbonate (DCB) for Bisphenol A (BPA) degradation under aeration conditions. Electrochemical experiments and reactive oxygen species (ROSs) trapping experiments showed that DCB treatment enhanced the redox cycle of Fe(II)/Fe(III), which promoted free radical generation. The optimized condition for the RM activation was achieved at 21 mmol/L dithionites, 84 mmol/L citrates, and 34 mmol/L bicarbonate, and the degradation of BPA by activated RM reached 410 µg BPA per gram of RM. This work provided a feasible way to utilize RM resources as an efficient, low-cost catalyst for organic pollutants treatment.

Highly TVB-N sensitive film with CMS as the 'bridge' via electrostatic interaction and hydrogen bond self-assembly for monitoring food freshness in intelligent packaging.

This work aims to develop the novel TVB-N sensitive film for monitoring food freshness. The film was fabricated based on carboxymethyl starch sodium (CMS)/agar (AG) complex and natural pigment, red radish anthocyanins (RRA). However, RRA is highly unstable under high humid conditions for their hydrophily. To immobilize RRA in AG film, we brought up CMS (negative charge) to immobilize RRA (positive charge) via electrostatic attractions and combined CMS and AG via hydrogen bond self-assembly. Zeta potential, Fourier transforms infrared (FT-IR) spectra, and X-ray diffraction analysis proved the electrostatic interaction and hydrogen bond self-assembly effect, indicating RRA immobilized effectively. Migration evaluation displayed that RRA remained stable in a high humidity environment (from RH 35%-95%). And its color difference is less than 5% in the low-temperature environment (4 °C). The prepared sensing film was found to be applied to detect the freshness of packaged grass carp and shrimp products. Its colors changed from initial orange-red to light red (3rd day) and then purple (4th day) with the increase of volatile amines inside the packaging. These findings suggested the film can be used as a sensing device for intelligent packaging of protein-rich food.

Comparative study of the effect of loading increments on the mesophilic codigestion of waste activated sludge and food waste: Reactor performance, stability analysis, and microbial community.

The performance and stability of mesophilic codigestion of waste activated sludge (WAS) and food waste (FW) were compared in two parallel, continuously stirred tank reactors using high- and low-magnitude loading increments for the loading regimes. The results indicated that a high methane (CH4) production of 6.98 L L-1·d-1 was realized without volatile fatty acid accumulation via low-magnitude loading increments at a high loading of 26.5 g-COD·L-1·d-1, and this system was more stable and achieved a higher efficiency than the codigestion system that used high-magnitude loading increments at similar loading and operating conditions. Furthermore, higher CH4 yields of 258-334 mL-CH4·g-COD-1, TCOD removal efficiencies of 64-79%, conversion ratios of 62-88%, and methanogenic activities of 0.37-0.40 g-CH4-COD·g-VS-1·d-1 were consistently maintained via the low-magnitude loading increments during the high-rate period. High abundances of the phyla Firmicutes (63.3%) and genus Methanosarcina (94.5%) contributed to the high rates and stable operating conditions of the mesophilic system for WAS and FW codigestion using low-magnitude loading increments.

Color-switchable hybrid dots/hydroxyethyl cellulose ink for anti-counterfeiting applications.

Many anti-counterfeiting inks have been explored recently, most of them are commonly involved in weak fastness, high cost and long-term toxicity, impeding their real-life applications. Herein, an environment-friendly and inexpensive anti-counterfeiting ink with excellent fastness is reported. The untifake ink is developed by combining hybrid dots (silicon/carbon) with hydroxyethyl cellulose (HEC) binder. Interestingly, the HEC binder can effectively prevent from aggregation-induced quenching of hybrid dots. Subsequently, the customized patterns are successfully transferred onto different surfaces of various substrates including cotton fabric, cellulosic paper, glass, metal, silicon wafer and PET film, using the as-prepared ink by screen-printing technique, exhibiting that the hybrid dots/HEC ink possesses widespread practicability. Notably, fluorescent color of these patterns can be switchable by adjusting environmental pH-value, further imparting the as-prepared ink with excellent covert performance. This new fluorescent hybrid dots/HEC ink will be promising candidates for high-level anti-counterfeiting applications including food packaging, apparel and documents.

Acclimatization of anaerobic sludge with cow manure and realization of high-rate food waste digestion for biogas production.

Long-term acclimatization of anaerobic sludge was conducted by operating a mesophilic continuously stirred anaerobic reactor (CSTR) with continuous feeding of food wastes (FW) and cow manure (CM). During the long-term acclimatization, continued increase of enzyme activity was revealed, while the microbial structure tended stable as shown by the Shannon index and microbial community. By biomethane potential analysis, the acclimated sludge had a methane yield about 13 times higher than the initial anaerobic sludge. The acclimated sludge was subsequently used for FW digestion with stepwise organic loading rate increase without CM addition. The functional phyla of Bacteroidetes and Proteobacteria, which originated from CM but not very abundant, were significantly enriched not only during sludge acclimatization with CM addition but also in the process of FW digestion without CM addition. A microbe coexistence network was proposed to support an explanation of the metabolic pathways of FW digestion using the acclimated sludge.

A comparative study of artificial cow and sheep rumen fermentation of corn straw and food waste: Batch and continuous operation.

To optimize the artificial rumen microorganism sources and develop a stable artificial rumen system, batch and continuous operation were investigated with corn straw and food waste as substrates. The batch trials evaluated the volatile fatty acid (VFA) yield, biogas production, and lignocellulose degradation efficiency. The continuous test evaluated the performance of the artificial cow and sheep rumen systems using a dynamic membrane bioreactor (DMBR) with a stepwise organic loading rate at mesophilic temperature. The anaerobic digestion (AD) of the lignocellulose biomass after rumen fermentation pretreatment and of the permeate from the artificial rumen system were also evaluated for CH4 production. The results indicated that the cow rumen microorganisms were more suitable than sheep rumen microorganisms for lignocellulosic biomass pretreatment and maximized the CH4 yield through the AD process without inhibition. After approximately four months of continuous operation, a stable and continuous artificial rumen system for lignocellulosic biomass degradation was achieved with cow rumen fluid as inoculum. Based on analysis of the core lignocellulose-degrading enzyme levels and gel filtration chromatography, the cow rumen microorganisms could secrete more extracellular multienzyme complexes to hydrolyze lignocellulosic biomass than the sheep rumen microorganisms in vitro. During the batch and continuous operations, a high diversity and similar richness of bacteria and fungi demonstrated that the cow rumen microorganisms can be used as a preferred inoculum for the artificial rumen system. The use of an artificial cow rumen system with a DMBR is a promising way to construct a stable and continuous artificial rumen system to biodegrade lignocellulosic biomass for biogas production.

Stable and high-rate anaerobic co-digestion of food waste and cow manure: Optimisation of start-up conditions.

Food waste (FW) and cow manure (CM) were co-digested to achieve a stable and high-rate of methane production. The start-up conditions (substrate mixing (FW/CM) ratio, substrate to inoculum ratio, and initial pH) were optimised, and the optimised parameters were experimentally confirmed by batch operation under mesophilic temperatures. To further verify the effects of start-up conditions on the long-term co-digestion process, a semi-continuous dynamic membrane bioreactor was operated for over 300 days with an FW/CM ratio of 2.5. Following the optimised operation scheme, the organic loading rate gradually increased to 11.9 g COD/L/d. Thus, stable anaerobic co-digestion was maintained at FW/CM ratio of 2.5, and a high CH4 production of 2.71 L CH4/L/d and CH4 yield of 441 mL CH4/g VS was achieved. In the long-term operation, the digestate pH was stable at approximately 8.4, which indicated a very favourable anaerobic reaction condition without volatile fatty acid accumulation.

Host-guest interaction-mediated fabrication of a hybrid microsphere-structured supramolecular hydrogel showing high mechanical strength.

The introduction of structured microsphere composites into hydrogels is found to improve their mechanical strength capability. Herein, chitosan microspheres were functionalized with poly(acrylamide-co-1-benzyl-3-vinylimidazolium bromide) (CS-P(AM-G)), which was synthesized through an in situ copolymerization of acrylamide and a guest functional monomer. Supramolecular hydrogels were fabricated by dynamic host-guest interactions between guest units and the host molecule cucurbit[8]uril (CB[8]). Investigations on the mechanical properties of the hydrogels show that the tensile stress and the compress stress of the hydrogels are five times higher than those of CB[8] hydrogels without CS, and the healing efficiency of the hydrogels at room temperature is 88% after 24 h. The results show that CS microspheres serve as both polyfunctional initiating and cross-linking centers, whereas the dynamic host-guest interactions endow the hydrogels with a higher self-healing property. The process provides a novel method for the production of tough and self-healing supramolecular hydrogels with various potential applications.

Cosubstrate strategy for enhancing lignocellulose degradation during rumen fermentation in vitro: Characteristics and microorganism composition.

To enhance the degradation of wheat straw (WS) and corn straw (CS) in rumen fermentation, characterization of degradation and ruminal microorganisms of monosubstrate (WS/CS) groups and a cosubstrate strategy with food waste (FW) group was performed. The cellulose, hemicellulose, and lignin degradation efficiency of WS and CS; soluble chemical oxygen demand; volatile fatty acid yields; and activity of ligninolytic, cellulolytic, and hemicellulolytic enzymes for the cosubstrate group were improved compared with those for the corresponding monosubstrate groups. An accurate and a good of fit of the Weibull kinetic model, decreased crystallinity index values, and characteristic absorbance bands in the Fourier transform-infrared spectra further confirmed that cosubstrate addition with FW decreased the resistance of cellulose and hemicellulose to biodegradation. High-throughput sequencing results suggested that the bacterial diversity in CS rumen fermentation and fungal diversity and richness in WS rumen fermentation were promoted with FW as a cosubstrate. The cosubstrate addition with FW significantly affected the composition of the ruminal bacteria and fungi in rumen fermentation. The relative abundances (RAs) of rumen bacteria were increased in the cosubstrate CS/WS and FW fermentation conditions, and the enhancement of CS degradation with FW supplementation was stronger than that of WS rumen fermentation with FW supplementation. The RAs of the ruminal fungal genera Ustilago and Fusarium were promoted in CS and WS fermentation with FW, respectively. Moreover, the fermentation properties and rumen flora in the FW rumen fermentation also provided some evidence to suggest an enhancement of the cosubstrate strategy compared with the monosubstrate strategy.

Persistent action of cow rumen microorganisms in enhancing biodegradation of wheat straw by rumen fermentation.

Rumen fermentation is known to be effective for lignocellulosic-wastes biodegradation to certain extent but it is still unclear if there exists a termination of the microorganisms' action to further degrade the bio-refractory fractions. In order to illuminate the related microbiological characteristics, experiments were conducted in a prolonged duration of rumen fermentation of mechanically ruptured wheat straw, with inoculation of cow rumen microorganisms in vitro. Although the organic wastes could not be biodegraded quickly, continuous conversion of the lignocellulosic contents to volatile fatty acids and biogas proceeded in the duration of more than three months, resulting in 96-97% cellulose and hemicellulose decomposition, and 42% lignin decomposition. X-ray diffraction and Fourier transform infrared spectroscopy further demonstrated the characteristics of lignocellulosic structure decomposition. Under the actions of cow rumen microorganisms, stable pH was maintained in the fermentation liquid, along with a steady NH4+-N, volatile fatty acids accumulation, and a large buffering ability. It was identified by enzyme analysis and Illumina MiSeq sequencing that the rich core lignocellulolytic enzymes secreted by the abundant and diverse rumen bacteria and fungi contributed to the persistent degradation of lignocellulosic wastes. Members of the Clostridiales order and Basidiomycota phylum were found to be the dominant lignocellulolytic bacteria and fungi, respectively. It could thus be inferred that the main lignocellulose degradation processes were a series of catalytic reactions under the actions of lignocellulolytic enzymes secreted from bacteria and fungi. The dominant hydrogenotrophic methanogens (Methanomassiliicoccus, Methanobrevibacter, Methanosphaera, and Methanoculleus) in the rumen could also assist CH4 production if the rumen fermentation was followed with anaerobic digestion.

Cow manure as additive to a DMBR for stable and high-rate digestion of food waste: Performance and microbial community.

Cow manure (CM) was added to a dynamic membrane bioreactor (DMBR) operated under anaerobic condition for enhancing food waste (FW) digestion for over 300 days with stepwise increase of organic loading rates (OLRs) from 1.07 to 11.9 g COD/L/day. At a FW/CM ratio of 3.5:1 (based on volatile solids), the mixed liquor pH was always above 8.0 and no apparent volatile fatty acids (VFAs) accumulation occurred even at the highest OLR of 11.9 g COD/L/day (hydraulic retention time as 10 days and solid retention time as 15.5 days, correspondingly), indicating a very stable operation condition which resulted in an average CH4 yield as high as 250 mL/g COD and CH4 production as high as 2.71 L CH4/L/day. The hardly biodegradable organic components, such as cellulose, hemicellulose, and lignin, were effectively degraded by 78.3%, 58.8%, and 47.5%, respectively. Significantly high anaerobic digestion reaction ratios, especially the hydrolysis ratio which is usually the limiting factor, were calculated based on experimental results. Furthermore, the high lignocellulase contents and coenzyme F420 levels, along with the decrease of cellulose crystallinity from 72.6% to 16.4% in the feedstock, provided strong evidence of an enhanced biological activity by CM addition. By high-throughput sequencing analysis, more abundant and diverse bacterial, archaeal, and fungal genera were identified from the DMBR sludge. With CM addition, the biodegradation of lignocellulose might have produced sufficient H2 and CO2 for the hydrogenotrophic methanogens such as Methanoculleus, Methanomassiliicoccus, and Methanobacterium, which were highly tolerant to ammonium inhibition, and then the elevated ammonium level would have provided high buffering capacity in the DMBR thus ensuring a stable condition for high rate FW digestion and CH4 production.

[Influence of Sludge Retention Time on the Performance and Stability of Mesophilic Anaerobic Co-digestion of Food Waste with Waste Activated Sludge].

Two parallel digestion systems of food waste (FW) and waste-activated sludge (WAS) were successfully initiated using a continuous stirred-tank reactor (CSTR), and the effect of different reduction extents of sludge retention time (SRT) on the co-digestion of FW and WAS was investigated. SRT Reduction extents longer than 8.3 d were not conducive to the stable operation of the co-digestion system when the organic load rate (OLR) was increased. The reduction extent of SRT should be reduced gradually from 5 d to 0.9 d to achieve high load and stable operation of the co-digestion of FW and WAS. After a long-term operation (approximately 282 d), the co-digestion reached stable operation at SRT of 9.1 d and OLR (calculated by COD) of (12.9±1.5) g·(L·d)-1. The corresponding methane production, methane yield (calculated by COD), pH, and volatile fatty acid (VFA, calculated by COD) were 3.94-4.25 L·(L·d)-1, 288-302 mL·g-1, 7.80-7.83, and 0.32-0.39 g·L-1, respectively. Additionly, the sludge characteristics of the co-digestion of FW and WAS under a high loading rate were also investigated. The results showed that the primary pathway of methane conversion was through acetic acid during the co-digestion of FW and WAS. Meanwhile, higher methanogenic activity of acetic acid, propionic acid, butyric acid, valeric acid, and coenzyme F420 concentration were also measured.

Titanium Dioxide Nanotube-Based Oxygen Indicator for Modified Atmosphere Packaging: Efficiency and Accuracy.

Colorimetric oxygen indicators can be applied for non-destructive testing in packaging; especially in modified atmosphere packaging (MAP). In this paper; titanium dioxide (TiO2) nanotube; which is used as a semiconductor photocatalyst in oxygen indicators; was synthesized via a microwave-assisted hydrothermal method. X-Ray Diffraction (XRD) was used to analyze its crystal form and Scanning Electron Microscope (SEM).to characterize its morphology. Its properties were studied using Brunauer-Emmett-Teller (BET), Diffuse Reflection Spectrum (DRS), and Bluebottle experiments. The results showed that the synthesized TiO2 nanotube was a mixture of rutile and anatase; with a specific surface area of 190.35 m²/g; and a wide band gap of 3.34 eV. Given the satisfactory performance; the TiO2-based oxygen indicator was prepared and combined with glycerol; methylene blue; and hydroxyethyl cellulose (HEC). The oxygen indicator demonstrated excellent photocatalytic performance and effectively avoided excitation by visible light. We studied the rheological properties; thixotropic properties; and wettability of the indicator. The results demonstrated the printability of the indicator solution; which was then printed in the polyethylene terephthalate (PET) film by screen printing and applied to MAP. The application results showed that the prepared oxygen indicator was able to provide visual support to judge whether the packaging was intact and the food was safe.

Polypyrrole-decorated Ag-TiO2 nanofibers exhibiting enhanced photocatalytic activity under visible-light illumination.

In this work, a novel photocatalyst, polypyrrole (PPy)-decorated Ag-TiO2 nanofibers (PPy-Ag-TiO2) with core-shell structure, was successfully synthesized using an electrospinning technique, followed by a surfactant-directed in situ chemical polymerization method. The results show that a PPy layer was formed on the surface of Ag-TiO2 nanofiber, which is beneficial for protecting Ag nanoparticles from being oxidized. Meanwhile, the PPy-Ag-TiO2 system exhibits remarkable light absorption in the visible region and high photocurrent. Among them, the 1%-PPy-Ag-TiO2 sample shows the highest photoactivity, which is far exceeds that of the single- and two-component systems. This result may be due to the synergistic effect of Ag, PPy, and TiO2 nanostructures in the ternary system.