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In this study, we have designed and synthesized a low-bandgap polymer, DPP-Qx, using quinoxaline (Qx), a non-alkylated weak acceptor, with diketopyrrolopyrrole (DPP) as an electron donor. The incorporation of Qx into DPP leads to the highest occupied molecular orbital level at −5.1 eV with a narrow optical bandgap (1.25 eV). The synthesized polymer is utilized in photovoltaics, and the photovoltaic properties are studied. This DPP-Qx with fullerene acceptors in polymer solar cells (PSCs) exhibits efficiency of 3.26%. Moreover, a minimum energy loss of 0.57 eV along with high extended external quantum efficiency is achieved with the DPP-Qx electron donor. The thermal, electrical and optical properties, energy levels and hole mobility of the synthesized polymer are studied and discussed.

A promising technique to enhance absorption of light in organic solar cells, “ternary approach” represents an important function in improving the device performance. We combined one small molecule dye (5,8-di(benzofuran-2-yl)-2,3-diphenylquinoxaline) (DB-Qx) with [6, 6]-phenyl C71 butyric acid methyl ester (PC71BM) (as the electron acceptor) and poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiopheneco-3-fluorothieno[3,4-b]thiophene-2-carboxylate] (PTB7-Th)(as the electron donor polymer) to form ternary solar cells. The morphology of the active layer of the ternary blend and hole mobility was potentially enhanced by the addition of a molecular donor. The complementary absorption of the two donors and matching photo-luminesce overlapping of DB-Qx with PTB7-Th contributed to improving the device performance. This means that the molecular donor in the ternary blend has an active function in the morphology. The devices produced PCE of 8.64% in the ternary blend system relative to 5.98% in the binary blend system. And, since the emission of DB-Qx partially overlaps with the absorption of PTB7Th, the transfer of energy from DB-Qx to PTB7-TH can improve the exciton utilization efficiency and achieve enhanced overall power conversion efficiency in this ternary solar cell. In this study, we synthesized a small fluorescent molecule material and constructed efficient ternary blend PSCs. Remarkably, the inverted device DIO-free ternary solar cells boost PCE from 5.98 to 8.64% and also exhibit the combined improvement in JSC and the morphology compared to those of DIO-processed films.

The safe handling of heavy metals and antibiotics during waste disposal has attracted wide attention. In the present study, hydrothermally treated sewage sludge was used for co-pyrolysis with different concentration ratios of pig manure at 600 °C for heavy metal immobilization and antibiotic removal. Heavy metals (except Cd) were mainly retained in the biochar samples due to a high degree of decomposition characteristic of organic matter. Pyrolysis significantly immobilized the heavy metals via converting unstable F1 + F2 + F3 fractions (acid-soluble fraction + reducible fraction + oxidizable fraction) to stable F4 fraction (residual fraction), and more pig manure addition led to improved immobilization performance. After co-pyrolysis, the potential environmental risk of feedstocks reduced significantly and the addition of 50 wt.% of pig manure gave a minimum potential ecological risk index of 10.36 with a low risk of contamination. In addition, six types of antibiotics in feedstocks were decomposed completely during pyrolysis. The co-pyrolysis process showed numerous advantages in the synthetic treatment of sewage sludge and pig manure by reducing the heavy metal toxicity and antibiotic levels.

The anionic detergent sodium dodecyl benzene sulfonate (SDBS) inhibits anaerobic solid waste fermentation process in mesophilic anaerobic digesters. In this study, the effect SDBS on the pe...

Supplementing nano zero valent iron (nZVI) is an attractive technology for wastewater treatment due to its advantages in accelerating the hydrolysis, fermentation and anaerobic digestion (AD) process. In this present study, nZVI was added to investigate its effects on enhancing tetracycline (TC) wastewater anaerobic treatment and the changes of microbial community, especially for underestimated syntrophic-methanogenic associations. The TC concentrations were 1, 10, 30, 50, 80, 100 and 150 mg/L with 0.38 g nZVI (with iron g/g VS of 0.50) complemented into reactors. Results revealed that nZVI could enhance AD process in both control and TC dosed systems, and the promoting effect on methanogenesis was more significant in systems of high concentration TC, with 100 and 150 mg/L. In addition, cumulative CH4 production for all TC added systems without nZVI were higher than the control indicating TC had positive effect instead of expected negative effect on AD process, high TC concentration of 100 and 150 mg/L only affecting the increase factor rather than causing inhibitory effect. After digestion, TC was largely removed in with/without nZVI systems. And also, nZVI evidently altered the bacterial and methanogenic community structure, with an increase abundance of syntrophic-methanogenic associations (Syntrophobacterales and Methanosarcinales) and resulting in the enhancement of methane generation. This research provides an efficient method for TC wastewater anaerobic treatment.

Developing efficient metal-organic framework (MOF) based nanocomposite sensor with superior performance for fast, sensitive and selective detection of ammonia (NH3) is essential for environmental protection and human health. This work reports synthesis of Pd-Co@IRMOF- 1 nanocomposite based gas sensor for the detection/sensing of ammonia (NH3) at room temperature. The successful synthesis of Pd-Co@IRMOF-1 nanocomposite was confirmed with spectroscopic and structural characterizations. Unlike earlier realizations, the fabricated Pd-Co@IRMOF-1 nanocomposite based sensor showed notable detection sensitivity for NH3 at concentrations down to 1ppm level. Distinctly, the MOF based nanocomposite sensor exhibited the excellent sensitivity and long-time stability to NH3. In contrast to other reported MOFs, Pd-Co@IRMOF-1 showed remarkable selectivity towards ammonia in comparison to formaldehyde, ethanol, acetone, Isopropyl alcohol and benzene. The Pd-Co@IRMOF-1 based sensor exhibited excellent performance for sensing of ammonia which can be helpful for future in wearable sensor device applications.

Acidic anaerobic digestion attracted much attention and interest due to its significant advantage in wastewater treatment. In the present study, methanogenic fermentation was successfully operated under acidic condition during treating wastewater containing oxytetracycline (OTC) in a scale up anaerobic baffled reactor (ABR). After start-up process, the pH value in the first compartment was 4.60 with high activity of methanogenesis. After stabilization, different OTC loading of 1.0, 3.3 and 5.0 g/m3/d was added in the influent for OTC removal. The resulted showed that OTC addition had little impact on the methane generation with whole COD and OTC removal rate of 95% and 60%, respectively. The microbial analysis, OTC addition could significantly influence the bacteria and archaea communities. To be more specific, Methanosaeta showed the highest relative abundance and tolerance to OTC under acidic condition. The present work supplied deeper insights into methane generation from acidic condition during wastewater containing OTC treatment.

Conductive materials presented promising advantages for enhancing anaerobic digestion (AD) performance. This study evaluated the effects of activated carbon (AC) and nano-zero-valent iron (nZVI) on the acidogenesis and whole AD to explore their potential mechanisms. AC increased the content of lactic and propionic acids in acidogenesis. nZVI increased the production of formic acid, acetic acid and H2 in acidogenesis, thus significantly promoted the methane yield in the whole AD. Mechanism exploration proved that AC enriched Trichococcus, and norank_f__Bacteroidetes_vadinHA17, and then improved the activity of enzymes involved in the production of lactic and propionic acids. nZVI buffered the pH to increase the activity of pyruvate formate-lyase (PFL) in formic acid production. Furthermore, nZVI enriched the Methanobacterium which use H2 and formic acid as substrate. The research paves pathway for the efficient enhancement of conductive materials added novel AD process.

Acetate is a pivotal intermediate product during anaerobic decomposition of organic matter. Its generation and consumption network is quite complex, which almost covers the most steps in anaerobic digestion (AD) process. Besides acidogenesis, acetogenesis and methanogenesis, syntrophic acetate oxidation (SAO) replaced acetoclastic methanogenesis to release the inhibition of AD at some special conditions, and the importance of considering homoacetogenesis had also been proved when analysing anaerobic fermentations. Syntrophic acetate-oxidizing bacteria (SAOB), with function of SAO, can survive under high temperature and ammonia/ volatile fatty acids (VFAs) concentrations, while, homoacetogens, performed homoacetogenesis, are more active under acidic, alkaline and low temperature (10°C-20°C) conditions, This review summarized the roles of SAO and homoacetogenesis in AD process, which contains the biochemical reactions, metabolism pathways, physiological characteristics and energy conservation of functional bacteria. The specific roles of these two processes in the subprocess of AD (i.e., acidogenesis, acetogenesis and methanogenesis) were also analyzed in detail. A two phases anaerobic digester is proposed for protein-rich waste(water) treatment by enhancing the functions of homoacetogens and SAOB compared to the traditional two-phases anaerobic digesters, in which the first phase is fermentation phase including acidogens and homoacetogens for acetate production, and second phase is a mixed culture coupling syntrophic fatty acids bacteria, SAOB and hydrogenotrophic methanogens for methane production. This review provides a new insight into the network on production and consumption of acetate in AD process.

Anaerobic digestion (AD) is widely used on waste treatment for its great capability of organic degradation and energy recovery. Accumulation of volatile fatty acids (VFAs) caused by impact loadings often leads to the acidification and failure of AD systems. Bioaugmentation is a promising way to accelerate VFA degradation but the succession of microbial communities usually caused unpredictable consequences. In this study, we used the sludge previously acclimated with VFAs for the bioaugmentation of an acidified anaerobic digestion system and increased the methane yield by 8.03-9.59 times. To see how the succession of microbial communities affected bioaugmentation, dual-chamber devices separated by membrane filters were used to control the interactions between the acidified and acclimated sludges. The experimental group with separated sludges showed significant advantages of VFA consumption (5.5 times less final VFA residue than the control), while the group with mixed sludge produced more methane (4.0 times higher final methane yield than the control). Microbial community analysis further highlighted the great influences of microbial interaction on the differentiation of metabolic pathways. Acetoclastic methanogens from the acclimated sludge acted as the main contributors to pH neutralization and methane production during the early phase of bioaugmentation, and maintained active in the mixed sludge but degenerated in the separated sludges where interactions between sludge microbiotas were limited. Instead, syntrophic butyrate and acetate oxidation coupled with nitrate and sulfate reduction was enriched in the separated sludges, which lowered the methane conversion rate and would cause the failure of bioaugmentation. Our study revealed the importance of microbial interactions and the functionality of enriched microbes, as well as the potential strategies to optimize the durability and efficiency of bioaugmentation.

Ciprofloxacin is the most commonly prescribed antibiotic, and its widespread use poses threat to environmental safety. The removal of ciprofloxacin from contaminated water has remained a major challenge. The present study investigated adding nanoscale zero-valent iron (NZVI) and activated carbon (AC) on high-level ciprofloxacin removal in hydrolysis-acidogenesis stage of anaerobic digestion. The results showed that the degradation rate of ciprofloxacin increased from 22.61% (Blank group) to 72.41% after adding NZVI/AC with concentration of ciprofloxacin in effluent decreasing from 8.25 mg L−1 to 3.48 mg L−1. The volatile fatty acids (VFAs) yield increased by 173.7% compared with the Blank group. In addition, the NZVI/AC group achieved the highest chemical oxygen demand (COD) removal rate and acidogenesis rate. The microbial community analysis presented that hydrolytic and acidogenic bacteria and microorganisms related to degrading ciprofloxacin were obviously improved in the NZVI/AC group. Moreover, eleven transformation products and the main degradation pathways were proposed based on mass spectrometry information. In summary, the NZVI/AC addition supplied promising approach for ciprofloxacin wastewater treatment.

Physical structures of sludge are critical factors determining the performance of the anaerobic digestion process, especially for the rate-limiting step, methanogenesis. Thus, to evaluate the effect of granular physical structure on methanogenesis and methanogenic community variation, intact and disintegrated granules were applied as inocula with formate, hydrogen and acetate as sole substrates in batch reactors. Kinetics results revealed that the physical structure of sludge had little impact on methane yield potential from three substrates, while a significantly different impact on methanogenesis rates of formate, hydrogen and acetate. The methanogenesis rate of formate in disintegrated granules was higher than that in the intact granular system, the methanogenesis rate of H2/CO2 in the intact granular system was higher than that in the disintegrated granules and the methanogenesis rate of acetate was similar with the in intact and disintegrated granular systems. Besides, in both intact and disintegrated granular systems, methanogenesis rates of formate were the highest, then followed the H2/CO2 and acetate was the lowest, indicating formate consumption has an advantage over hydrogen in the studied system. A microbial assay indicated that Methanobacteriales, Methanosarcinales and Methanomicrobiales are dominant methanogens on the order level, and the physical structure of granular sludge has little influence on methanogenic communities on the order level but showed significant influence on the species level. It enlightens us that the physical structure of sludge could be considered for regulating the anaerobic digestion via influencing the methanogenesis rates.

Enriching suitable fermentative products by optimizing operation conditions could effectively improve the efficiency of anaerobic digestion. In the present study, pH (5.0-6.0) and hydraulic retention time (HRT) (2 h-12 h) were regulated for volatile fatty acids (VFAs) production during glucose fermentation in acidogenic continuous stirred tank reactor (CSTR). Results showed that acetate and butyrate dominated during pH regulation. HRT reduction favored butyrate production and formate retainment. Maximum total VFAs production with highest acetate content was achieved at pH of 6.0 and HRT of 6 h. Microbial analysis revealed that Clostridium_sensu_stricto_1 was predominant butyrate producer during pH regulation, and Bacteroides was main contributor when HRT shorter than 6 h. In addition to acetyl-CoA pathway, acetate could also be produced via homoacetogenesis by Parabacteroides, UCG-004 and norank_f__Acidaminococcaceae. These results give guidance for enhancing targeted VFAs products by optimizing operational parameters or bio-augmentation with specific bacteria.

Composting, as an effectively bio-oxidative process, has been widely used for converting organic waste to organic fertilizer. However, the low fertilizer efficiency of composting product limited its application in agriculture. To improve the growth-promoting effect of composting product, the present study investigated the bioaugmentation strategy of inoculating indole-3-acetic-acid (IAA)-producing bacteria. Firstly, two IAA-producing bacteria (Bacillus safensis 33C and Rhodococcus rhodochrous YZ) were isolated from composting products with high IAA yields of 39.18 and 16.32 μg mL-1, respectively. Secondly, the microbial inoculants were prepared with 33C, YZ and a previously isolated IAA-producing strain Corynebacterium stationis 29B. To increase the accumulation of microbial secondary metabolites, microbial inoculants were amended at the secondary fermentation stage of composting. Physicochemical characterization showed that the maturity of composting product was significantly promoted by inoculating microbial inoculants prepared with 33C and 29B (single and combined inoculants). Finally, bioaugmentation with 33C and 29B increased the IAA contents of composting products by 2.9-5.2 times, which benefited the germination and early vegetative growth of plants. In summary, inoculating proper IAA-producing bacteria during secondary fermentation of composting could improve the quality of composting product and expand its application.

In this study, the performances of a conventional anaerobic baffled reactor (ABR) and an ABR combined with microbial electrolysis cells (MECs) for enhancing degradation of volatile fatty acids (VFAs) were evaluated in 55°C. The ABR-MECs system achieved a total chemical oxygen demand (COD) removal rate of 97.2% and a methane yield of 236 ± 5 mL g-1 CODremoved at organic loading rate (OLR) of 6.9 kg COD m-3 d-1, which were higher than those of the ABR with 77.6% and 207 ± 5 mL g-1 CODremoved, respectively, at OLR of 5.1 kg COD m-3 d-1. The pyrosequencing analysis confirmed that the introduction of MECs into ABR was conducive to establishing stable functional communities of syntrophic fatty acids oxidizing bacteria (SFOB), exoelectrogens and hydrogenotrophic methanogens, such as Syntrophobacter (5.4%), Thermodesulfovibrio (2.0%), Methanobacterium (43.8%), Methanolinea (20.4%). The content of unclassified bacteria increased from 12.4% in the ABR system to 52.3% in the ABR-MECs system. In contrast, the proportion of aceticlastic methanogens decreased from 50.1% in the ABR to 24.5% in the ABR-MECs system. The improved performance of the thermophilic ABR-MECs system resulted from phase separation, wide ecological niche and intensification of methanogenesis process via functional microbes, which significantly enhanced the degradation of propionic acid and acetic acid.

In this work, we present a high-performance smart electronic nose (E-nose) system consisting of a multiplexed tin oxide (SnO2) nanotube sensor array, read-out circuit, wireless data transmission unit, mobile phone receiver, and data processing application (App). Using the designed nanotube sensor device structure in conjunction with multiple electrode materials, high-sensitivity gas detection and discrimination have been achieved at room temperature, enabling a 1000 times reduction of the sensor’s power consumption as compared to a conventional device using thin film SnO2. The experimental results demonstrate that the developed E-nose can identify indoor target gases using a simple vector-matching gas recognition algorithm. In addition, the fabricated E-nose has achieved state-of-the-art sensitivity for H2 and benzene detection at room temperature with metal oxide sensors. Such a smart E-nose system can address the imperative needs for distributed environmental monitoring in smart homes, smart buildings, ...

Surfactants are widely used and discharged into wastewater treatment plants, which might influence the anaerobic digestion (AD) treatment of municipal waste. In this study, the effects of typical anionic surfactants sodium dodecyl benzene6 sulfonate (SDBS) and non-ionic surfactants APG, on mesophilic anaerobic co-digestion of sludge, food waste, and green waste were investigated. Results indicated that at 5 mg/g, the biogas production was inhibited in SDBS supplemented systems while stimulated in APG-added reactors, with the methane yield of 146.58 L/g VS consumed. At 15 mg/g, the biogas production in both SDBS and APG supplemented reactors was both inhibited. It means the negative or positive effect of APG on AD depends on the dose of APG supplementation. The 16S rRNA gene analysis demonstrated the microbial community structure in the digester was changed due to the addition of surfactant.

Conductive material assisted anaerobic digestion presented much interest and promising prospect in pollutant removal during wastewater treatment. The present study deeply investigated the effect iron/carbon in anaerobic digestion for dichlorophen (DCP) degradation and methane production in synthetic DCP wastewater treatment. Results showed that nano-zero valent iron/activated carbon (nZVI/AC) and zero valent iron/activated carbon (ZVI/AC) gave higher chemical oxygen demand (COD) conversion (42.18% and 42.61%) and DCP removal (98.49 wt% and 99.00 wt%) in acidification step with better methane production from anaerobic digestion of the pretreated effluent. Same phenomenon occurred in the direct anaerobic degradation process due to the formation of galvanic cells between iron and carbon. In comparison, applying iron/carbon in acidification as pretreatment strategy plus following effluent anaerobic degradation showed higher efficiency in methane production and DCP removal than that of direct anaerobic degradation. Specifically, the methane production was 253.70 mL and 253.41 mL in subsequent anaerobic digestion system after nZVI/AC and ZVI/AC acidification pre-treatment, which was higher than 224.37 mL and 246.31 mL in direct anaerobic digestion system. Microbial community analysis showed that Clostridium_sensu_stricto_1 was the dominated bacteria due to its important role in DCP wastewater treatment. Both acetoclastic and hydrogenotrophic methanogens were enhanced in iron/carbon added systems, which was also agreement with the strengthen in related genes involved in methanogenesis. In conclusion, the present work systematically investigated the enhancement role of iron/carbon system in anaerobic digestion for DCP wastewater treatment and paved way for future application.

In this study, anaerobic batch experiments were conducted to investigate the effect of carbon-based (biochar) and metal-based (nanoscale zero-valent iron, NZVI and zero valent iron, ZVI) mediators on the AD process treating phenolic wastewater. Fresh apricot shell- and wood-derived biochar (BiocharA, BiocharB) could remove the phenol efficiently (77.1% and 86.2%), suggesting that biodegradation cooperated with adsorption had advantage in phenol removal. BiocharB, NZVI and ZVI enhanced the methane production by 17.6%, 23.7% and 23.2%, respectively. Apart from serving as carrier for microbial growth, BiocharB might promote the direct interspecies electron transfer (DIET) since the Anaerolineaceae/Clostridium sensu stricto, which have potential for DIET, were enriched. NZVI and ZVI added systems mainly enhanced the abundance of Clostridium sensu stricto (24.5%, 37.6%) and Methanosaeta. Interestingly, BiocharA inhibited the methanogenesis completely. An inhibitory mechanism was proposed: the exposure of absorbed microbes on the BiocharA to the highly concentrated phenol in biochar' pores resulted in the inhibition of methanogens, especially for Methanosarcina. In conclusion, this study showed that suitable biochar (BiocharB) could serve as an alternative redox mediator for realizing simultaneously the efficient phenol removal and methane production.

A hierarchical ZnO nanostructure gas sensor was fabricated to evaluate the concentration of acetone in exhaled human breath. Such information can be used for the diagnosis of diabetes since acetone levels in exhaled breath in excess of 1.8ppm are typically associated with diabetes sufferers. When exposed to acetone, the fabricated sensor exhibits a unique U-shaped response curve as a function of temperature. It was discovered that its acetone sensing behavior changes from oxidizing to reducing as the temperature increases. The sensor's characteristic response was shown to be associated to the carbonyl group present in the acetone molecule. The fabricated hierarchical ZnO nanostructure sensor is able to detect acetone concentration levels as low as 1ppm even at room temperature, making it suitable for noninvasive diabetes diagnosis.

The anaerobic bio-treatment of lower COD/SO42- ratio wastewater constitutes a bottle-aqneck due to the limited carbon source. In this type of environment, interactions between acidogenic fermentation bacteria and methane-producing bacteria (MPB) are aided by syntrophic fatty acid oxidation bacteria present in the functional niche; MPB and sulfate-reducing bacteria (SRB) compete with each other due to the availability of sulfate. Therefore, introduction of syntrophic fatty acid oxidation bacteria into an SRB dominated culture can achieve maximum utilization of the substrate, weakening the competition of MPB. In this study, the mixed culture of dominant syntrophic propionate oxidation bacteria (SPOB) and SRB was established and characterized at 35°C. The dominant SPOB and SRB were enriched in a continuous flow stirred-tank reactor and in batch experiments, respectively. Subsequently, an equal proportion of the enriched sludge was mixed and incubated in conical flasks with propionate as the sole substrate. S...

Sludge filtrate is a kind of special organic wastewater generated from hydrothermally pretreated sewage sludge. The efficient treatment of sludge filtrate can promote the development of sludge recycling technology. Herein, the anaerobic baffled reactor (ABR) assisted by symbionts of short chain fatty acid-oxidation syntrophs (SFAS) and exoelectrogens was applied to treat the sludge filtrate. The influence of fermentation temperature and promotion of methanogenesis via symbionts were focused. The results showed that the COD removal efficiency and methane yield of the ABR system assisted by symbionts at 35 °C (R3) were 11.7% and 11.0% higher than the one at 55 °C (R2), respectively. And the COD removal efficiency and methane yield of the R2 system were 9.1% and 12.9% higher than the traditional ABR system at 55 °C (R1), respectively. Large abundances of exoelectrogens such as Thermincola and Geobacter were found in the R2 and R3 systems, respectively. Moreover, ample Syntrophobacter, Syntrophomonas and Methanobacterium were detected in both R2 and R3 systems. The present research revealed the importance of SFAS, exoelectrogens and hydrogenotrophic methanogens for the improvement of methanogenesis. Besides, the mesophilic condition is conducive to enhancing the methanogenesis rate of sludge filtrate.

Anodic aluminum oxide (AAO) template based gas sensor, is often used due to its large surface reaction area. With longer AAO tube, the effective reaction surface area is widely believed to further increase leading to a higher sensitivity. However, through 3D current density distribution figures generated from the simulation software, a more uniform distribution is found to form at the center of the tube area instead of only top surface, making the tube area more effective for the reaction. This double effect of tube length is thus believed to contribute to the improved sensitivity of AAO template based gas sensor.

Synthesis of high-performance room-sensing materials have attracted lots of attention in the gas sensor area. In this work, ternary sensing material of MoO2-Ni-Graphene composite was synthesized by the hydrothermal method. Through X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, the existence of chemisorbed oxygen contents introduced by the annealing processes are validated (the intensity of graphene oxide (GO) peak (C (0 0 2)) at 9.90° is increased, and the oxidation state of Mo is changed from 6+ to 4+ and 5+). The gas sensing performance of composites to ethanol, formaldehyde, and ammonia was then tested and response (Rg/Ra) of the sample annealed at 400 °C towards 1000 ppm ethanol was improved to 105 at room temperature and the minimum detection limit was 15 ppm. Meanwhile, it didn’t show response towards formaldehyde. For the enhanced sensitivity and selectivity of sensor towards ethanol, metallic nature of Ni and MoO2 on graphene surface, interaction of hydroxyl species via hydrogen bonding and lower LUMO energy levels (0.13 eV) value of ethanol were the main factors. Moreover, long term stability of 40 ppm ethanol for 30 days with response 21.61 ± 0.96 suggested that proposed sensor could be an ideal candidate for future commercial ethanol sensing.

Interspecies electron transfer (IET) between syntrophic fatty-acid oxidizing bacteria (SFOBs) and methanogens decided the performance of anaerobic digestion. Electron shuttles, as potential IET accelerators, were controversial concerning their influences on methanogenesis. In this study, concentration-dependent effects of anthraquinone-2-sulfonate (AQS) and cysteine on glucose digestion were firstly demonstrated: low dosage of AQS and cysteine (50 and 100 µM, respectively) had highest methane yield (133.5% and 148.6%, respectively). Using butyrate as substrate, distinct tendencies towards the enrichment of methanogenic community were further revealed. Cysteine just acted as a reductant which lowered ORP quickly and enriched most methanogens. It benefited methanogenesis right until methanogenic substrates accumulated. AQS, however, showed characteristic features of electron shuttles: it was firstly oxidized by SFOBs and then reduced by hydrogenotrophic methanogens, which accelerated methanogenic butyrate degradation. This study showed wide spectrum of SFOBs and methanogens benefited from the addition of electron shuttles, which laid foundation for future application.

Growing environment problem and emphasis of environmental protection motivate intense research efforts in exploring technology to improve treatment efficiency on refractory organic pollutants. Hence, finding a method to make up for the deficiency of anaerobic digestion (AD) is very attractive and challenging tasks. The recent spark in the interest for the usage of some nanomaterials as an additive to strengthen AD system. The adoption of iron compounds can influence the performance and stability in AD system. However, different iron species and compounds can influence AD system in significantly different ways, both positive and negative. Therefore, strengthening mechanism, treatment efficiency, microbial community changes in Nanoscale Zero Valent Iron (nZVI) and Fe3O4 nanoparticles (Fe3O4 NPs) added AD systems were summarized by this review. The strengthening effects of nZVI and Fe3O4 NPs in different pollutants treatment system were analyzed. Previous study on the effects of nZVI and Fe3O4 NPs addition on AD have reported the concentration of nZVI and Fe3O4 NPs, and the types and biodegradability of pollutants might be the key factors that determine the direction and extent of effect in AD system. This review provides a summary on the nZVI and Fe3O4 NPs added AD system to establish experiment systems and conduct follow-up experiments in future study.

For evaluating the methanogenesis from typical methanogenic precursors (formate, acetate and H2/CO2), CH4 production kinetics were investigated at 37±1°C in batch anaerobic digestion tests and stimulated by modified Gompertz model. The results showed that maximum methanation rate from formate, acetate and H2/CO2 were 19.58±0.49, 42.65±1.17 and 314.64±3.58NmL/gVS/d in digested manure system and 6.53±0.31, 132.04±3.96 and 640.16±19.92NmL/gVS/d in sewage sludge system during second generation incubation. Meanwhile the model could not fit well in granular sludge system, while the rate of formate methanation was faster than from H2/CO2 and acetate. Considering both the kinetic results and microbial assay we could conclude that H2/CO2 methanation was the fastest methanogenic step in digested manure and sewage sludge system with Methanomicrobiales as dominant methanogens, while granular sludge with Methanobacteriales as dominant methanogens contributed to the fastest formate methanation.

Nowadays featuring outstanding eco-friendliness, the phytochemical fabrication method of nanostructures is very popular. Here, we propose to utilize the Astragalus membranaceus extract as the reducing and capping agent to stabilize the metal and to avoid the aggregations of nanoparticles during ZnO nanoflowers synthesis procedure. As a result, the whole fabrication procedure was highly efficient and cost-effective without requiring a special environment of high pressure or elevated temperature and without chemical hazards used or produced. After the fabrication, detailed characterization about material morphology and crystal structure was carried out, including scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscope (FTIR). Moreover, the ZnO nanoflowers demonstrated distinctive antibacterial, antioxidant and electrochemical sensing effect. Specifically, ZnO nanoflowers had an antibacterial inhibition zone of 19(±0.7) and 15(±0.8) mm in diameter against the concentration of 50 μL (1 mg/mL) Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which is greatly improved compared to the reference drug (Kanamycin). Besides, antioxidant activity was also tested using H2O2 free radical scavenging assay and 60% 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition of 0.5 mg/mL was reported. Finally, controlled by the diffusion process during the charge transfer procedure, 4-nitorphenol was dramatically reduced and a limit of detection of 0.08 μM by ZnO nanoflowers modified electrode was observed during the cyclic voltammetry (CV) experiment. Because the phenolic compounds originating from Astragalus membranaceus helped to facilitate the electron transfer, the limit of detection was lower compared to other materials, such as copper oxide nanoparticles (Cu2O-NPs), silicon dioxide/silver nanoparticles (SiO2/Ag-NPs), zinc oxide nanoparticles (ZnO-NPs), activated carbon (AC) and cobalt oxide nanocubes (Co3O4). Therefore, featuring easy operation, low-cost and eco-friendliness, our proposed ZnO nanoflowers fabrication method will have a great potential in biomedical and electro-catalytic fields.

Aiming at relieving acid accumulation in anaerobic digestion (AD), syntrophic associations of syntrophic fatty acid-oxidation bacteria and H2/formate-scavenging methanogens were enriched by feeding propionate, butyrate and formate in an up-flow anaerobic sludge blanket (UASB) reactor. Results showed that methane yield increased by 50% with increasing formate concentration (0–2000 mg COD/L). In addition, the abundance and quantity of SFOB (Syntrophobacter, Smithella and Syntrophomonas) and H2/formate-scavenging methanogens (Methanobacteriales and Methanomicrobiales) were increased after microbial acclimation. The enriched syntrophic associations showed higher propionate and butyrate removal efficiencies of 98.48 ± 1.14% and 99.71 ± 0.71%, respectively. Furthermore, encoding genes of formate dehydrogenase and hydrogenases presented higher abundances after microbial enrichment, which suggested that the enhancements of interspecies formate transfer and interspecies hydrogen transfer between syntrophic associations benefited volatile fatty acids (VFAs) conversion. This research provided an effective strategy to relieve acid accumulation.

The increasing production of waste activated sludge (WAS) from wastewater treatment plants presents an inherent environmental burden. In this study, Free nitrous acid combined with potassium ferrate (FNA + PF) pretreatment was used to enhance solubilization and biochemical methane potential of WAS. Results indicated that the maximum removal rates of total suspended solid by PF, FNA, and PF + FNA pretreatment were 21.84%, 38.09%, and 56.17%, respectively. The biochemical methane potential of WAS without pretreatment reached 61.22 L CH4/kg VSS added while this value increased to 147.07 L CH4/kg VSS added after FNA + PF pretreatment (0.06 g/g TSS NaNO2 and 0.25 g/g TSS K2FeO4). Shotgun metagenomic analysis revealed that FNA + PF pretreatment could increase the diversity and stability of microbial communities by shifting methanogenic pathways from strictly acetoclastic to acetoclastic/hydrogenotrophic, thereby enhancing methane production. This study suggested that FNA + PF pretreatment is a promising technology to reduce WAS and enhance methane production by pretreated WAS during anaerobic digestion.

Analyzing the concentration of acetone in human breath constitutes a promising non-invasive means to diagnose the onset of diabetes, with acetone levels of at least 1.8ppm typically associated to individuals suffering from diabetes. In this paper, we report the performance of a hierarchical ZnO nanostructure gas sensor for acetone detection. The fabricated gas sensor can detect concentrations as low as 1ppm while operating at a comparatively lower temperature of 200°C. In addition, the proposed gas sensor can be fabricated on a silicon wafer using a MEMS process, making it thereby possible to fully integrate gas sensing and electronic circuitry on a single silicon chip.

In this paper, we report an on-chip gas sensor based on novel zinc oxide (ZnO) nanocombs for carbon monoxide (CO) sensing. With ZnO gas sensing nanocombs fully integrated on a single silicon chip, the concept of low cost complementary-metal-oxide-semiconductor (CMOS) microsensor capable of on-chip gas sensing and processing is enabled. Compared with all previous implementations, the proposed ZnO nanocombs feature much larger effective sensing area and exhibit ultra-high sensitivity even at the room temperature. Specifically, at room temperature, we demonstrate peak sensitivities as high as 7.22 and 8.93 for CO concentrations of 250 ppm and 500 ppm, respectively. As a result, by operating the proposed ZnO-nanocomb-based gas sensor at the room temperature, the widely adopted power consuming heating components are completely removed. This leads to not only great power saving, but also full compatibility between the gas sensor and the on-chip circuitry in term of acceptable operating temperature. In addition, the reported fast response/recovery time of ~200 s/~50 s (250 ppm CO) makes it well suited to real-life applications.