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•A mechanism that drives a successful and fast bioaugmentation process is proposed.•Hydrogenotrophic methanogens are crucial for an efficient bioaugmentation process.•Successful ...bioaugmentation was achieved in ammonia-inhibited thermophilic reactors.•Bioaugmentation with hydrogenotrophic methanogen stimulated the growth of SAOB.•The VFA-ammonia co-inhibitory effect decreased rapidly after bioaugmentation.
Bioaugmentation to alleviate ammonia inhibition under thermophilic anaerobic digestion has never been reported, as well as the working mechanism that allows a fast and successful bioaugmentation. Thus two bioaugmentation inocula (an enriched culture, and a mixed culture composed 50/50 by Methanoculleus thermophilus and the enriched culture) on the recovery of ammonia-inhibited thermophilic continuous reactors was assessed. The results showed that bioaugmentation improved methane yield by 11–13% and decreased the volatile fatty acids (VFA) by 45–52% compared to the control reactor (abiotic augmentation). Moreover, the importance of hydrogenotrophic methanogens to a fast and successful bioaugmentation was recognized. Specifically, the instant hydrogen partial pressure reduction by the bioaugmented hydrogenotroph created thermodynamically favourable conditions for the acetate oxidation process and consequently, the catabolism of other VFA. High-throughput sequencing results strengthened this explanation by showing that the bioaugmented M. thermophilus stimulated the growth of syntrophic acetate oxidising bacterium Thermacetogenium phaeum, immediately after bioaugmentation.
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•56% of the energy contained in the agave bagasse was recovered by two-stage process.•Energy recovery from two-stage process was 7 times higher than one-stage process.•The increase of ...stirring speed decreased the H2-consumption by homoacetogenesis.•In the second-stage, methane yields of 90% were obtained at high OLR and short HRT.
Continuous H2 and CH4 production in a two-stage process to increase energy recovery from agave bagasse enzymatic-hydrolysate was studied. In the first stage, the effect of organic loading rate (OLR) and stirring speed on volumetric hydrogen production rate (VHPR) was evaluated in a continuous stirred tank reactor (CSTR); by controlling the homoacetogenesis with the agitation speed and maintaining an OLR of 44 g COD/L-d, it was possible to reach a VHPR of 6 L H2/L-d, equivalent to 1.34 kJ/g bagasse. In the second stage, the effluent from CSTR was used as substrate to feed a UASB reactor for CH4 production. Volumetric methane production rate (VMPR) of 6.4 L CH4/L-d was achieved with a high OLR (20 g COD/L-d) and short hydraulic retention time (HRT, 14 h), producing 225 mL CH4/g-bagasse equivalent to 7.88 kJ/g bagasse. The two-stage continuous process significantly increased energy conversion efficiency (56%) compared to one-stage hydrogen production (8.2%).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Pyrolysis of dried sewage sludge is regarded as an effective treatment method as well as a promising technology for energy/fuel production. In this work, thermochemical conversion of dried sewage ...sludge in a continuous reactor at different pyrolysis temperatures (400–800 °C) and solid residence times (6–46 min) was conducted. The pyrolysis products obtained using different pyrolysis conditions were extensively investigated. It is indicated that high pyrolysis temperature (>700 °C) and long solid residence time (>23 min) could enhance secondary reactions and decrease the yield of bio-oil. The maximum yield of bio-oil of 16.69% was achieved at reaction temperature of 700 °C and solid residence time of 23 min. The FTIR and GC-MS analyses of the bio-oil obtained at optimum condition indicated that it contained large amounts of phenols and esters. H2 and CO2 were the main components of pyrolysis gas, with a total amount that exceeded 52.18%. The characteristics of the char, including elemental composition, functional groups, and combustion property were investigated by XRF, FTIR, and TG. FTIR analysis of the char showed that the main functional groups are M–X, C–O, and C–H. The volatile content in the char decreased with an increase of pyrolysis temperature, while it increased with an increase of solid residence time. Heavy metals distribution in pyrolysis products of dried sewage sludge were investigated by inductively coupled plasma atomic emission spectroscopy. The results showed that most of the heavy metals remained in char. In addition, the potential ecological risk assessment of heavy metals was assessed.
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In recent years, a broad range of nanocrystals have been synthesized in droplet-based microfluidic reactors which provide obvious advantages, such as accurate manipulation, better reproducibility and ...reliable automation. In this review, we initially introduce general concepts of droplet reactors followed by discussions of their main functional regions including droplet generation, mixing of reactants, reaction controlling,
in situ
monitoring, and reaction quenching. Subsequently, the enhanced mass and heat transport properties are discussed. Next, we focus on research frontiers including sequential multistep synthesis, intelligent synthesis, reliable scale-up synthesis, and interfacial synthesis. Finally, we end with an outlook on droplet reactors, especially highlighting some aspects such as large-scale production, the integrated process of synthesis and post-synthetic treatments, automated droplet reactors with
in situ
monitoring and optimizing algorithms, and rapidly developing strategies for interfacial synthesis.
Different synthetic strategies derived from droplet reactors with integrated functional regions for NC synthesis.
A combination of photocatalysis and membrane separation technology is applied to the degradation of refractory antibiotic organic compounds in aqueous solutions. TiO2 photocatalysts, which are ...inexpensive, commercially available, and nontoxic, have lately been of wide concern. In this study, a submerged ceramic membrane photocatalytic reactor (SCMPR) coupling with a suspended TiO2 photocatalyst was designed and developed for removing antibiotics in environmental water remediation. Separation of the TiO2 photocatalyst was carried out via antifouling ceramic membranes with hollow structures. The SCMPR had high removal capacity and stability for amoxicillin (AMX) degradation over a wide pH range, i.e., 6.5 to 9.0. The unique hollow structure of the ceramic membranes and aeration system not only provided high self-purification capability, but also enhanced the removal stability, of the SCMPR. As a result, SCMPRs are promising wastewater processing devices for practical application. Two possible pathways for AMX photodegradation in the SCMPR were analyzed by means of a Q-TOF LC/MS system, with most of the intermediates finally mineralized to CO2, water, and inorganic ions by hydroxyl radicals.
•The SCMPR exhibited high mineralization capacity and stability for AMX degradation.•Ceramic membranes showed good corrosion and oxidation resistance.•The hollow structure of ceramic membrane provided high self-purification capability.•The TiO2 was separated effectively using the ceramic membrane separation technology.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Catalytic hydrogen production by methanol steam reforming is considered to be an attractive hydrogen source option. However, performance of conventional packed beds for methanol steam reforming may ...be limited by heat transfer, which results in a low effective factor of the catalyst. In this work, CuO/ZnO/Al2O3 catalyst particles with diameter of 0.5 mm were filled in the micro-reactor for hydrogen production by methanol steam reforming. At steam to methanol ratio of 1.3, effects of inlet temperature, space velocity on reactor performance were investigated. The temperature distribution in the catalyst bed has also been studied. Results showed that methanol conversion decreased with space velocity and it increased with inlet temperature. Hydrogen production yield increased firstly and then decreased with space velocity. And it increased with the increasing of temperature. However, CO content in the product also increased with temperature, and it decreased with the increasing of inlet space velocity, especially at low temperature condition. Compared to conventional tubular fixed bed reactor, the micro-reactor presented a slightly better performance due to the fixed bed nature of catalyst, which is inefficiency in tubular reactor. Cold spot was observed at inlet of micro-reactor reaction chamber, and the highest temperature difference at cold spot area reached about 6 K. The maximum temperature difference throughout the catalyst bed reached 10 K in the micro-reactor.
Temperature distribution on the catalyst bed in micro-reactor at inlet temperature of 473K. Display omitted
•MSR in Micro-reactor was compared to that of Tube reactor.•Performance of Micro-reactor is superior to Tube reactor.•Methanol conversion of Micro-reactor is 5.46% higher than that of Tubular reactor.•The highest methanol conversion of 94.06% was achieved in Micro-reactor.•Temperature distribution in Micro-reactor was obtained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•CuO NPs in 1mgL−1 performed most severe suppression on Anammox.•TiO2 NPs in 1mgL−1 showed most durable inhibition on Anammox.•Long-term exposure within NPs led to the increase of microbial ...diversity.•Long-term exposure within NPs resulted in abundance decrease of AAOB.•Candidatus Brocadia showed more tolerance to NPs than Candidatus Kuenenia.
In this study, a sequencing batch reactor (SBR) was operated as Anammox and used as parent reactor. Then three SBRs seeded from the parent reactor were adopted for investigating the effect of CuO, ZnO and TiO2 nanoparticles (NPs) on nitrogen removal, microbial activity and microbial communities of Anammox. The bioactivities of anaerobic ammonia-oxidizing bacteria (AAOB) after different exposure period were detected by batch experiments. Results showed that NPs performed immediate and durable toxicity on Anammox. The nitrogen removal efficiency decreased to 2.3%, 2.9% and 14.0% from 71%, the Anammox rate decreased to 0.13, 0.16 and 0.75 from 2.76mgh−1g−1VSS, and the relative abundance of AAOB decreased to 2.57%, 2.78% and 2.61% from 7.99%, respectively. CuO and ZnO NPs performed similar effect, while CuO NPs led to the most severe toxicity and lowest accumulative effect. TiO2 NPs showed the lowest toxicity but most durable suppression on Anammox process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Mixed Ni–Fe oxides are attractive anode catalysts for efficient water splitting in solar fuels reactors. Because of conflicting past reports, the catalytically active metal redox state of the ...catalyst has remained under debate. Here, we report an in operando quantitative deconvolution of the charge injected into the nanostructured Ni–Fe oxyhydroxide OER catalysts or into reaction product molecules. To achieve this, we explore the oxygen evolution reaction dynamics and the individual faradaic charge efficiencies using operando differential electrochemical mass spectrometry (DEMS). We further use X-ray absorption spectroscopy (XAS) under OER conditions at the Ni and Fe K-edges of the electrocatalysts to evaluate oxidation states and local atomic structure motifs. DEMS and XAS data consistently reveal that up to 75% of the Ni centers increase their oxidation state from +2 to +3, while up to 25% arrive in the +4 state for the NiOOH catalyst under OER catalysis. The Fe centers consistently remain in the +3 state, regardless of potential and composition. For mixed Ni100–x Fe x catalysts, where x exceeds 9 atomic %, the faradaic efficiency of O2 sharply increases from ∼30% to 90%, suggesting that Ni atoms largely remain in the oxidation state +2 under catalytic conditions. To reconcile the apparent low level of oxidized Ni in mixed Ni–Fe catalysts, we hypothesize that a kinetic competition between the (i) metal oxidation process and the (ii) metal reduction step during O2 release may account for an insignificant accumulation of detectable high-valent metal states if the reaction rate of process (ii) outweighs that of (i). We conclude that a discussion of the superior catalytic OER activity of Ni–FeOOH electrocatalysts in terms of surface catalysis and redox-inactive metal sites likely represents an oversimplification that fails to capture essential aspects of the synergisms at highly active Ni–Fe sites.
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•Hydrocracking and hydrotreating reactions kinetics based on lumping technique.•Hydrotreating reactions are also considered.•Axial dispersion model is used to represent the ...slurry-phase reactor.•Dynamic and steady-state simulations for hydrocracking of heavy oils are presented.•The performance of CSTR and SPR is compared.
The dynamic modeling and simulation of a continuous slurry phase reactor for catalytic hydrocracking and hydrotreating of an atmospheric residue (312 °C+) are reported. The reactor model is based on an axial dispersion. The hydrocracking kinetic model takes into account a five-lump model previously reported in the literature. The hydrotreating reactions simulated are: hydrodesulfurization (described by Langmuir–Hinshelwood kinetics), hydrodenitrogenation (for basic and non-basic nitrogen), hydrodeasphaltenization and hydro Conradson carbon removal (modeled with power-law approach). All the intrinsic kinetic parameters and correlations were taken from the literature. The performance for the slurry-phase reactor was compared with a continuous stirred tank reactor. Dynamic simulations and steady-state predictions agreed with the expected behavior of the heavy fractions and impurities hydroprocesing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The environmentally-friendly, economically-viable production of ethanol from cellulosic biomass remains a major contemporary challenge. Much work has been done on the disruption of cellulosic biomass ...structure, the production of enzymes for the conversion of cellulose and hemicellulose into simple sugars that can be fermented by bacteria or yeast, and the metabolic engineering of ethanol-producing microbes. The results of these studies have enabled the transition from laboratory to industrial scale of cellulosic ethanol production. Notably, however, current processes use free microbial cells in batch reactors. This review highlights the advantages of using immobilized and co-immobilized cells together with continuous bioreactor configurations. These developments have the potential to improve both the yield and the green credentials of cellulosic ethanol production in modern industrial settings.
•Cellulosic ethanol production needs application of new technologies for competing with gasoline.•Cell immobilization technologies improve bioethanol productivity.•Ethanol yield in different processes is affected by the reactor configurations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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