Short-chain Acids Research Articles

Tin dioxide decorated on Ni-encapsulated nitrogen-doped carbon nanotubes for anodic electrolysis and persulfate activation to degrade cephalexin: Mineralization and degradation pathway

In this study, bamboo-shaped carbon nanotubes exhibiting high nitrogen content and Ni encapsulation (Ni@NCNT) were effectively synthesized by a simple pyrolysis method. The catalytic peroxydisulfate activation for cephalexin (CPX) degradation was investigated using the prepared material. SnO2 was further decorated and fabricated on the anode material (SnO2/Ni@NCNT) for electrochemical degradation of CPX in an aqueous solution. Transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy indicated that the SnO2 nanoparticles were uniformly distributed on the surface of Ni@NCNT. Electrochemical characterization employing cyclic voltammetry and linear sweep voltammetry demonstrated that SnO2/Ni@NCNT displayed higher oxygen evolution potential and electrocatalytic activity than Ni@NCNT. Mineralization of CPX in wastewater was performed using electrolysis coupled with persulfate oxidation. The analysis revealed a synergistic strengthening effect. The electropersulfate oxidation resulted in higher total organic carbon (TOC) removal (70.3%) than the sum of electrooxidation (48.1%) and persulfate oxidation (9.2%) toward CPX. This phenomenon might result from the regeneration of sulfate radicals (SO4•−) on the anode and complementary oxidation by SO4•− and OH. Persulfate oxidation alone was shown to result in low TOC removal, although CPX was mostly degraded. Additionally, the CPX degradation pathway involving electropersulfate oxidation was proposed and it is indicated that CPX molecules were completed decomposed by the examination of short chain acids, mineralized ions, and ecotoxicity evolution indicated that the antibiotic was completely degraded. This study provides a new approach for the design and preparation of novel electrode materials and electrochemical degradation facilities for the removal of pollutants via persulfate activation.

Utilization of waste cooking oil for highly efficient recovery of unburned carbon from coal fly ash

The disposal of industrial solids (e.g., coal fly ash (CFA)) and kitchen wastes (e.g., waste cooking oil (WCO)) has attracted much attention worldwide. However, it is challenging to manage these wastes economically. In this study, the potential of WCO as a collector to recover unburned carbon from CFA by froth flotation was investigated for the utilization of CFA and WCO resources. Traditional collectors, i.e., diesel oil and fresh cooking oil, were used for comparison. The composition of the collectors was determined via Fourier-transform infrared spectroscopy and gas chromatography/mass spectrometry. The interaction mechanisms between the CFA surface and different collectors were analyzed by atomic force microscopy, X-ray photoelectron spectroscopy, and dynamic contact angle measurements. The results indicate that WCO contains a large amount of oxygen-containing functional groups such as aldehydes, short-chain acids, and long-chain fatty acids. Furthermore, flotation tests indicated that in comparison with diesel oil and cooking oil as collectors, WCO can significantly enhance the recovery of unburned carbon from CFA and effectively lead to tailings with low loss on ignition. The major mechanism responsible for the enhanced CFA flotation is that its oxygen-containing functional groups, such as CO and COOH, were covered, whereas the C–H/C–C groups were exposed on the CFA surface due to the strong adhesion forces between the CFA and WCO under the synergistic effect of the short-chain acids/aldehydes and long-chain fatty acids in WCO. This resulted in a significant increase in the surface hydrophobicity of the CFA after the WCO treatment. This work provides an efficient and promising green method for the recovery of unburned carbon from CFA as well as the reuse of WCO, allowing the management of an industrial solid and kitchen waste.

Silicone membrane contactor for selective volatile fatty acid and alcohol separation

The effect of pH and extraction temperature on flux, recovery, mass transfer coefficient and separation factor of volatile fatty acids (VFAs) and alcohols from synthetic solutions and cheese whey fermentate was investigated using a silicone membrane contactor with water as extractant. The silicone membrane allowed extraction of undissociated acids only, resulting in substantially higher recovery efficiencies at pH 3 than at pH 5. Furthermore, the non-porous silicone membrane favoured extraction of longer chain over shorter chain acids. Caproic acid was extracted with the highest flux of 1.30 (± 0.02) g m−2 h−1 in short time (32 h), with a 41.5 % recovery efficiency at pH 3 and 20 °C, indicating the feasibility of its selective separation from the VFA mixture. A similar trend was observed for alcohols, with butanol being extracted with a 39 % recovery efficiency at 40 °C, against 32 % and 19 % of propanol and ethanol, respectively, while the mass transfer coefficients were not affected by temperature. When applying the silicone membrane contactor to real cheese whey fermentate at pH 3, butyric and acetic acid were extracted with 21.5 % and 7% recovery efficiency, respectively, suggesting the feasibility of the contactor for VFA recovery from real fermentate.

Fast Pyrolysis of Hemicelluloses into Short-Chain Acids: An Investigation on Concerted Mechanisms

The nature of the main primary mechanisms involved in lignocellulosic fast pyrolysis is often assumed to be radical mechanisms. Here we demonstrate that thermal depolymerization of native hemicelluloses can undergo several primary and secondary concerted reactions leading to light oxygenates that can compete with radical mechanisms. To model these reactions at a microscopic level, we used high-level quantum calculations based on functional theory. In parallel, a set of experimental data was collected to confirm the main structural features of extracted and purified hemicelluloses and to describe chemical variations within fast pyrolysis products released from various hemicellulosic fractions at 823 K. In general, the barriers computed at 800 K for pericyclic reactions were found to be reasonably low competing with these of homolytic reactions. The critical role of hydrogen bonding and spatial arrangement on product distribution was clearly demonstrated, stabilizing effects depending greatly on temperature. We reported a useful data set of intrinsic kinetic parameters and a reaction network readily available to complete kinetic models for “primary” and “secondary” fast pyrolysis of hemicelluloses.

16S rRNA Sequencing and Metagenomics Study of Gut Microbiota: Implications of BDB on Type 2 Diabetes Mellitus.

Gut microbiota has a critical role in metabolic diseases, including type 2 diabetes mellitus (T2DM). 3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)-1,2-benzenediol (BDB) is a natural bromophenol isolated from marine red alga Rhodomela confervoides. Our latest research showed that BDB could alleviate T2DM in diabetic BKS db mice. To find out whether BDB modulates the composition of the gut microbiota during T2DM treatment, 24 BKS db diabetic mice were randomly grouped to receive BDB (n = 6), metformin (n = 6), or the vehicle (n = 6) for 7 weeks in a blinded manner. Non-diabetic BKS mice (n = 6) were used as normal control. Diabetic mice treated with BDB or metformin demonstrated significant reductions in fasting blood glucose (FBG) levels compared with the vehicle-treated mice in the 7th week. Pyrosequencing of the V3–V4 regions of the 16S rRNA gene revealed the changes of gut microbiota in response to BDB treatment. The result demonstrated short-chain acid (SCFA) producing bacteria Lachnospiraceae and Bacteroides were found to be significantly more abundant in the BDB and metformin treated group than the vehicle-treatment diabetic group. Remarkably, at the genus levels, Akkermansia elevated significantly in the BDB-treatment group. Metagenomic results indicated that BDB may alleviate the metabolic disorder of diabetic mice by promoting propanoate metabolism and inhibiting starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism. In conclusion, our study suggests that the anti-diabetic effect of BDB is closely related to the modulating structure of gut microbiota and the improvement of functional metabolism genes of intestinal microorganisms.

Enhanced degradation of furfural by heat-activated persulfate/nZVI-rGO oxidation system: Degradation pathway and improving the biodegradability of oil refinery wastewater

Oil refinery wastewater is characterized by high values of temperature and furfural concentration. Furfural is a toxic and non-biodegradable substance in aqueous media that its absorption through the skin causes acute neurological and pulmonary effects. In this study, a heat-activated persulfate (HAP) system in combination with reduced graphene oxide-supported nano zero-valent iron catalyst (nZVI-rGO) was developed for oil refinery wastewater treatment. Five operational parameters regarding furfural removal were statistically modeled by an orthogonal central composite design (OCCD) and then optimized by genetic algorithm (GA) technique. The main characteristics of the nZVI-rGO as well as its reusability were investigated by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy mapping (EDX-mapping), X-ray diffraction analysis (XRD) and vibrating sample magnetometer (VSM) analysis. The optimum values for the solution temperature, nZVI-rGO dosage, persulfate (PS) concentration, solution pH and reaction time were predicted to be 70 °C, 1.25 g L−1, 4.28 mmol L−1, 5.46 and 50 min, respectively. Under the optimized conditions, the experimental furfural removal efficiency in HAP/nZVI-rGO and HAP oxidation systems were obtained to be 97.80 and 68.20 %, respectively. Sulfate radical (SO4•-) has greater participation in furfural mineralization than hydroxyl radical (HO•). The major intermediates resulting from the furfural mineralization were short-chain acids including acetic acid and formic acid. Regardless, almost complete furfural mineralization was achieved after 100 min of the oxidation reaction. The optimized HAP/nZVI-rGO process was able to significantly improve the biodegradability of wastewater by more than 2 times.

Aqueous phase reforming coupled to catalytic wet air oxidation for the removal and valorisation of phenolic compounds in wastewater

Aqueous phase reforming (APR) coupled to catalytic wet air oxidation (CWAO) has been investigated as an approach to remove phenolic compounds from wastewater, converting them into valuable gases. Partial oxidation of phenol was achieved in the first CWAO stage trying to minimize mineralization so to allow a high yield to valuable gases in the second APR stage. APR runs were carried out with different mixtures of compounds corresponding to phenol oxidation pathway (phenol, quinones, long and short chain acids) and representing different degrees of oxidation in CWAO stage. A range of TOC and COD removal (74–90%) was observed in APR stage for the single compounds, with higher removal for long chain acids. Likewise, long chain acids provided with the highest conversion to gases. APR of mixtures rich in acids gave the highest yield to CH4 (11.0 mmol CH4/g TOCinitial). H2 production was low in all cases, due to competing direct conversion of long and short chain acids into CH4. TOC and COD removal from wastewater was similar in APR-CWAO and APR, however the conversion to gases and the yield to CH4 were markedly higher for APR-CWAO, thus overcoming the difficulties previously observed in the direct APR of phenol.

Lactobacillus plantarum prevents obesity via modulation of gut microbiota and metabolites in high-fat feeding mice

Abstract Lactobacilli are reported to reduce weight gain, the mechanism has not been well elucidated. In this study mice received either normal-chow-diet or high–fat-diet (HFD), and drinking water with or without addition of Lactobacillus plantarums HT121 for 11 weeks. We found that HT121 decreased the body weight and improved glucose tolerance in high-fat fed mice. ELISA analysis showed HT121 decreased levels of LPS and inflammatory cytokines in serum, and increased short chain acids levels in feces. 16S rRNA sequencing indicated HT121 restored Firmicutes/Bacteroidetes ratio, PCOA, major phyla, genera of Akkermansia, lactobacillus, and Ruminococcus changed by HFD to the levels of normal group. Untargeted metabolomics analysis indicated HT121 reversed the levels of discriminant metabolites in liver, such as taurine, isoleucine, L-phenylalanine, methionine, and spermidine changed by HFD. Our results provide a new insight in prevention and treatment of obesity and type 2 diabetes.

Value Proposition of Untapped Wet Wastes: Carboxylic Acid Production through Anaerobic Digestion.

Although traditional anaerobic digestion (AD) process to produce methane-rich biogas from wet waste is deep-rooted, high carbon footprint and its low value as compared with other renewable sources demand advanced strategies to avoid its production. An emerging conversion pathway to arrest methanogenesis for producing value-added fuels and chemicals instead of biogas is sought as a sustainable alternative. This research provides a comprehensive analysis on current technology development, process challenges, applications, and economics for producing high-value short-chain carboxylic acids from AD of wet wastes. We show that (1) the theoretical energy yields of acids equal or exceed biogas, and (2) the cost of these acids is competitive with those produced from chemical markets, making this economically viable for mass production. With global abundance of wet waste feedstocks, this process of short-chain acid production provides a promising alternative to conventional biogas production technology, while achieving waste management and carbon mitigation goals.

Simultaneous improvement of the electrical conductivity and mechanical properties via double-bond introduction in the electrically conductive adhesives

For electrically conductive adhesives (ECAs), high electrical conductivity generally conflicts with excellent mechanical properties because electrical conductivity increases while desirable mechanical properties decrease with the increase in loading of conductive fillers or removal of lubricants on the silver filler surface. In this work, a method was developed to improve both the electrical conductivity and mechanical properties of the ECAs by introducing double bonds. Itaconic acid (IA) was used to replace the lubricant on the silver flake (Ag-F) surface, and acrylic acid (AA) was used as part of the ECA resin matrix. IA can replace the lubricant on the Ag-F surface, similar to other short-chain dibasic acids, to improve the ECA electrical conductivity. Furthermore, IA can be polymerized with AA to form covalent bonds between the silver flakes and the resin matrix, enhancing the mechanical properties of ECA. Compared with ECA filled with commercial silver flakes, the electrical conductivity of ECA filled with IA-treated silver flakes increased by ~ 21%, and the lap shear strength increased by ~ 29%.

A phytotoxicity assessment of the efficiency 2,4-D degradation by different oxidative processes

Highly stable compounds such as dichlorophenoxyacetic acid (2,4-D), which are present in the commercial herbicide Tordon®, are difficult to degrade. Therefore, the objective of this work was to degrade 2,4-D present in Tordon® using different oxidative processes, such as anodic oxidation, Fenton reactions, electro-Fenton, photoelectro-oxidation and photoelectro-Fenton processes. An oxide electrode with the nominal composition Ti/Ru0.3Ti0.7O2 was prepared and inserted into an electrochemical cell containing 100 mL of 0.05 mol L−1 Na2SO4 (pH 3) and 100 mg L−1 of Tordon®. Electrolysis was performed applying a constant current of 50 mA cm−2 for 2 h. The concentration of Fenton's reagent was varied from 5 to 10 mg L−1 (Fe2+), and from 50 to 100 mg L−1 (H2O2). Chemical analyses of the total organic carbon (TOC) and the chemical oxygen demand (COD) were performed whilst high-performance liquid chromatography (HPLC) was used to monitor the degradation. A phytotoxicity assessment was performed using cucumber seeds as bioindicators. Germination tests were performed using cucumber seeds in the presence of the solutions collected after the application of the oxidative processes. Several analyses were carried out to determine the following: total protein content, the extent of lipid peroxidation, activity of superoxide dismutase, hydrogen peroxide content, catalase activity, and glutathione reductase activity. Oxidation of 2,4-D was observed in all of the oxidative processes, and significant results for the removal of TOC and COD were obtained. Anodic oxidation, and the Fenton and photoelectro-oxidation processes were the least efficient, affording 2,4-dichlorophenol, 2-chlorohydroquinone, and 2-chlorobenzoquinone as by-products. The electro-Fenton and photoelectro-Fenton processes were the most efficient, giving short-chain acids as the main by-products. The formation of these by-products directly affected the phytotoxicity results. The processes that formed short-chain by-products did not generate significant oxidative stress during seed growth, and therefore, seed germination tests were successful.

Combination of highly efficient microflora to degrade paint spray exhaust gas

Spray paint exhaust gas contains recalcitrant volatile organic compounds (VOCs), such as benzene, toluene and xylene (BTX). Treating BTX with a biofilter often achieves unsatisfactory results because the biofilter lacks efficient microbial community. In this work, three strains for BTX degradation were isolated and identified as Pseudomonas putida, Bacillus cereus and Bacillus subtilis by using 16S rRNA sequencing technology. A consortium of highly efficient microbial community was then constructed on a stable biofilm to treat BTX in a biofilter. A relatively suitable ratio of P. putida, B. cereus and B. subtilis was obtained. An efficiency of over 90% was achieved in the biofilter with VOC concentration of 1000 mg/m3 through inoculation with the microbial community after only 10 days of operation. Thus, fast start-up of the biofilter was realised. Analysis of intermediate products by gas chromatography–mass spectrometry indicated that BTX was degraded into short-chain aldehydes or acids via ring opening reactions.

Transformation analysis of key liquid phase products during lignite fermentation to produce biological hydrogen

There was little research on the changes and interconversion of organic compounds in the intermediate liquid-phase productsin the hydrogen production by anaerobic fermentation of coal. The types and concentrations of the intermediate liquid-phase products are not only related to the efficiency of coal conversion into biohydrogen, but one of the important contents of study on the generation mechanism of biohydrogen from coal. In order to study the change of key liquid phase products in the process of bio-hydrogen production from coal, the simulation experiments of bio-hydrogen production were conducted under suitable environmental conditions using lignite from Daliuta, Shaanxi province. The hydrogen concentration and key liquid phase products were measured using gas chromatography and GC–MS, respectively, to reveal its change. The results show that: (1) there is correspondence between the key liquid phase products and hydrogen yield. The saturated alkanes and cyclic hydrocarbons show a trend of first increasing, then decreasing, and finally increasing, but the changes of proteinaceous materials are just the opposite, which is correspondent to the initial stage, peak stage and terminal stage of hydrogen production, respectively. (2) The short-chain volatile fatty acids are accumulated gradually in the process of hydrogen production, and the short-chain acids of aromatic show a trend of first increasing, then decreasing, increase again and finally decreasing, which is correspondent to the different biochemical reactions, such as the release of small molecules, the utilization of microorganisms, hydrocarbon oxidation and the redegradation of macromolecule. (3) The lipids, aldehydes and ketones are the parent substances of acid production, and the changes are related to the increased acids to a certain extent. This research not only reveals the biochemical effects between gas and liquid phases, but further enriches the theory of bio-hydrogen production from coal.

Polysaccharide from flammuliana velutipes improves colitis via regulation of colonic microbial dysbiosis and inflammatory responses

The aim of this study is to investigate whether Flammuliana Velutipes Polysaccharide (FVP) could aid in the prevention of colitis. Effect of FVP on colitis was evaluated using dextran sulfate sodium (DSS)-induced colitis in rats. Influence of FVP on the expression of inflammation related biomarkers and signal pathway element of TLR4\\NF-κB were assessed. The composition and taxonomy of colonic microbiota were analyzed by 16S rDNA high throughput sequencing, and the concentrations of caecal short fatty chain acids were assessed by chromatography-mass spectrometry. Our results showed that FVP treatment could regulate the colonic microbial dysbiosis and promote the levels of caecal short fatty chain acids, leading to down-regulation of TLR4\\NF-κB signal pathway, which finally ameliorate the colitis. Thus, the present study is the first attempt to elucidate the effect of FVP on colitis and support the potential application of FVP as a functional food ingredient or preventive drugs for colitis.

An efficient synthetic strategy for ligand-free upconversion nanoparticles

An efficient synthetic approach was developed to prepare ligand-free UCNPs using short-chain acids as stripping agents by a simple vortexing method in a short time, allowing the transfer of UCNPs from hydrophobic to hydrophilic media.

Implications of gut microbiota dysbiosis and metabolic changes in prion disease

Evidence of the gut microbiota influencing neurodegenerative diseases has been reported for several neural diseases. However, there is little insight regarding the relationship between the gut microbiota and prion disease. Here, using fecal samples of 12 prion-infected mice and 25 healthy controls, we analyzed the structure of the gut microbiota and metabolic changes by 16S rRNA sequencing and LC-MS–based metabolomics respectively as multi-omic analyses. Additionally, SCFAs and common amino acids were detected by GC–MS and UPLC respectively. Enteric changes induced by prion disease affected both structure and abundances of the gut microbiota. The gut microbiota of infected mice displayed greater numbers of Proteobacteria and less Saccharibacteria at the phylum level and more Lactobacillaceae and Helicobacteraceae and less Prevotellaceae and Ruminococcaceae at the family level. A total of 145 fecal metabolites were found to be significantly different in prion infection, and most (114) of these were lipid metabolites. Using KEGG pathway enrichment analysis, we found that 3 phosphatidylcholine (PC) compounds significantly decreased and 4 hydrophobic bile acids significantly increased. Decreases of 8 types of short-chain acids (SCFAs) and increases of Cys and Tyr and decreases of His, Trp, and Arg were observed in prion infection. Correlation analysis indicated that the gut microbiota changes observed in our study may have been the shared outcome of prion disease. These findings suggest that prion disease can cause significant shifts in the gut microbiota. Certain bacterial taxa can then respond to the resulting change to the enteric environment by causing dramatic shifts in metabolite levels. Our data highlight the health impact of the gut microbiota and related metabolites in prion disease.

Highly Responsive Ultraviolet Sensor Based on ZnS Quantum Dot Solid with Enhanced Photocurrent

Detection of visible blind UV radiation is not only interesting but also of technologically important. Herein, we demonstrate the efficient detection of UV radiation by using cluster like ZnS quantum dot solid nanostructures prepared by simple reflux condensation technique. The short-chain ligand 3-mercaptopropionic acid (MPA) involved in the synthesis lead to the cluster like formation of ZnS quantum dots into solids upon prolonged synthesis conditions. The ZnS QD solid formation resulted in the strong delocalization of electronic wave function between the neighboring quantum dots. It increases the photocurrent value, which can be further confirmed by the decrease in the average lifetime values from 64 to 4.6 ns upon ZnS cluster like QD solid formation from ZnS QDs. The ZnS quantum dot solid based UV sensor shows good photocurrent response and a maximum responsivity of 0.31 (A/W) at a wavelength of 390 nm, is not only competitive when compared with previous reports but also better than ZnS and metal oxide-based photodetectors. The device exhibits a high current value under low-intensity UV light source and an on/off ratio of IUV/Idark = 413 at zero biasing voltage with a fast response. Further, photocurrent device has been constructed using ZnS quantum dot solid nanostructures with graphene hybrids as an active layer to improve the enhancement of photoresponsivity.

WO3/TiO2 Hybrids and Their Applications for the Photocatalytic Degradation of P-Substituted Phenols

Tungsten trioxide (WO3) has received a great attention in last decade because of its commercial applications in smart windows, display devices, mobile phones, photocatalysis, solar cells and hydrogen generation. Due to a bandgap around 2.8 eV, WO3 is a semiconductor suitable for photocatalytic and photovoltaic applications using sunlight1, in contrast to most popular TiO2 of the bandgap of about 3.2 eV.2 However, a combination of WO3 with TiO2 leads to significantly enhancement of photoactivity of the system mainly due to increased separation efficiency of photogenerated electron-hole pairs3. When these charge carriers reach the semiconductor/solution interface, they may be involved in the surface reactions leading to decomposition of pollutants. These reactions occur via formation of highly reactive intermediates, such as hydroxyl radicals and superoxide radicals that break down organic pollutants into safe, smaller compounds such as carbon dioxide, water, and short-chain acids.5 Photocatalysis is important in the degradation of phenolic compounds, for example 4-chlorophenol that are products of industrial waste.4 This method is both eco-friendly and inexpensive. Tungsten trioxide and its composites were synthesized on indium-doped tin oxide (ITO) plates using sol-gel, electrochemical and hydrothermal methods. The morphology and composition of the synthesized WO3 and WO3/TiO2 hybrid were characterized using SEM, XRD, UV-Vis and an optical microscope. Electrochemical studies including cyclic voltammetry and chronoamperometry were performed to test their photoactivity. Lastly, the samples were used in the photocatalytic degradation of 4-chlorophenol monitored by UV-vis spectroscopy. Chronoamperometry studies showed that the WO3 by itself had a rapid electron-hole recombination rate. After combination with TiO2, the charge recombination rate decreased and the system was rapidly stabilized under illumination. The photoactivity of WO3 and WO3/TiO2 hybrid was measured with the use of cyclic voltammetry. HPLC analysis of the degradation products of 4-chlorophenol over time using the TiO2/WO3 composite indicated that the hybrid was able to degrade the pollutant more effectively, in a shorter time than WO3 alone. The addition of TiO2 to WO3 deposited on ITO resulted in increase of photoactivity of the system due to slowing down the electron-hole recombination process. Secondly, the degradation of 4-chlorophenol was more efficient using the WO3/TiO2 system. Future experiments will be focused on explanation of differences in the degradation mechanisms of 4-chlorophenol with the use of WO3 alone and WO3/TiO2 hybrid. The effect of the ratio of TiO2 and WO3 in the hybrid on photoactivity and photocatalytic degradation will also be explored. Tada et. al, Langmuir. 20, 4665-4670 (2004)Dette et. al, Nano Lett. 14, 6533-6538 (2014)DohLevil-Mitrovil et. al, Materials Research Bulletin. 83, 217-224 (2016)Meng et. al, Materials Science and Engineering: B. 180, 20-26 (2014)Linsebigler et. al, Chem. Rev. 95, 735-758 (1995)

Bio-hydrogen production by a new isolated strain Rhodopseudomonas sp. WR-17 using main metabolites of three typical dark fermentation type

In this work, a new strain WR-17 was isolated for photo-fermentative hydrogen production and its hydrogen production capacity was investigated by utilizing main liquid byproducts of three dark fermentation types in batch culture. Experimental results indicated that strain WR-17 was identified as genus Rhodopseudomonas and maximum hydrogen yield of 2.42 mol H2/mol acetate was obtained when the acetate was used as sole carbon source. Strain WR-17 had an excellent ability of using mixed short chain acids of three typical fermentations such as acetate and ethanol, acetate and butyrate, acetate and propionate. Result demonstrated that the metabolites of butyric acid-type fermentation as substrate is fitting to produce hydrogen and maximum cumulative hydrogen volume of 2156 ml/L-medium was obtained when acetate of 30 mmol/L and butyrate of 15 mmol/L were used. Therefore, butyric acid-type fermentation has great potential for further obtaining high hydrogen yield by the combining photo-fermentation.

Solar-Driven Removal of 1,4-Dioxane Using WO3/nγ-Al2O3 Nano-catalyst in Water

Increasing demand for fresh water in extreme drought regions necessitates potable water reuse. However, current membrane-based water reclamation approaches cannot effectively remove carcinogenic 1,4-dioxane. The current study reports on the solar-driven removal of 1,4-dioxane (50 mg L−1) using a homemade WO3/nγ-Al2O3 nano-catalyst. Characterization methods including scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF) analyses are used to investigate the surface features of the catalyst. The 1,4-dioxane mineralization performance of this catalyst under various reaction conditions is studied. The effect of the catalyst dosage is tested. The mean oxidation state carbon (MOSC) values of the 1,4-dioxane solution are followed during the reaction. The short chain organic acids after treatment are measured. The results showed that over 75% total organic carbon (TOC) removal was achieved in the presence of 300 mg L−1 of the catalyst with a simulated solar irradiation intensity of 40 mW cm−2. Increasing the dose of the catalyst from 100 to 700 mg L−1 can improve the treatment efficiency to some extent. The TOC reduction curve fits well with an apparent zero-order kinetic model and the corresponding constant rates are within 0.0927 and 0.1059 mg L−1 s−1, respectively. The MOSC values of the 1,4-dioxane solution increase from 1.3 to 3 along the reaction, which is associated with the formation of some short chain acids. The catalyst can be effectively reused 7 times. This work provides an oxidant-free and energy saving approach to achieve efficient removal of 1,4-dioxane and thus shows promising potential for potable reuse applications.