Total Hydrogen Volume Research Articles

Production of Hydrogen by Purple Non-Sulfur Bacteria Rhodopseudomonas yavorovii IMV B-7620

Hydrogen production by microorganisms is studied by using different sources of carbon for their cultivation. Purple non-sulfur bacteria are capable of producing molecular hydrogen phototrophically with the simultaneous accumulation of biomass on organic substrates that may be waste from various industries. That fact makes the study of this group of microorganisms very much promising. The aim. The determination of the ability of purple non-sulfur bacteria Rhodopseudomonas yavorovii IMV B-7620 to produce hydrogen consuming different organic substrates and their effects on the main metabolic indicators of culture growth. Methods. Bacteria were grown in 100 mL glass jars in liquid modified ATCC No. 1449 medium for 14 days at temperature +27...+30ºC and at constant light (200 lux). Biomass accumulation and hydrogen production in the cultivation medium were determined using sodium acetate (12 and 36 mM), malate (12 and 36 mM), succinate (36 mM), glucose (36 mM), starch (36 mM), sodium citrate (36, 60, 90 mM). Biomass was determined turbidimetrically, the composition of the gas phase was determined using a gas chromatograph LHM-8-MD, redox potential and pH were estimated potentiometrically. The volume of gas synthesized was measured on a syringe scale. Determination of the content of organic acids in the culture liquid was analyzed by high performance liquid chromatography. Results. The utilization of organic compounds (malate, glucose, starch, sodium citrate) by R. yavorovii IMV B-7620 is accompanied by hydrogen synthesis. Under the growth with sodium acetate, bacteria produce small amounts of succinate. The malate metabolism results in the production of small amounts of fumarate on the 7th day of cultivation and isocitrate on the 10th day of cultivation. On the 14th day of cultivation, the cultural liquid contains a small amount of succinate. On the 14th day of cultivation, R. yavorovii IMV B-7620 produces 7.64±0.04% of hydrogen in the medium with malate (36 mM). However, the maximum concentration of hydrogen in the gas phase (21.26±0.08%) was gained on the 14th day of cultivation in the medium with sodium citrate. The maximum concentration of H2 in the gas phase during the growth in the medium with sodium citrate (60 mM) and NH4+ was 27.83±5.46% on the 7th day of cultivation and 35.69±0.40% with increasing concentration of sodium citrate up to 90 mM on the 10th day of cultivation. The total volume of hydrogen was 25.54±0.49 mL of H2 during the growth of R. yavorovii IMV B-7620 in the medium with 90 mM sodium citrate and NH4+. That is 1.5 times more than the amount of H2 produced during the growth of bacteria in the medium with 60 mM sodium citrate with the addition of NH4+. Conclusion. Purple non-sulfur bacteria R. yavorovii IMV B-7620 synthesize hydrogen during photofermentation of organic compounds. Bacteria were isolated from the water of Yavoriv Lake (Lviv region, Ukraine) formed as a result of flooding of the sulfur quarry. Bacteria consume sodium citrate, malate, glucose, starch and emit hydrogen. The total volume of hydrogen during the growth of R. yavorovii IMV B-7620 in the medium with 90 mM sodium citrate and NH4+ is 25.54±0.49 mL H2.

Production of biohydrogen by an anaerobic digestion process using the residual glycerol from biodiesel production as additive to cassava wastewater

Despite the significant increase in biogas and methane production provided by the addition of glycerol to agro-industrial waste when submitted to anaerobic biodigestion, just a few studies are directed to hydrogen production using this procedure. Thus, the present study evaluated the anaerobic biodigestion of the cassava wastewater with the addition of as much as 5% of residual glycerol mass. Wastewater inoculum from swine farming was used, which was characterized through the isolation of anaerobic microorganisms, DNA extraction and genetic sequencing, revealing that this inoculum contained bacteria from the genus Brevundimonas, from subgroup Bacillus subtilis and Bacillus cereus, and from species Bacillus licheniformis. Factor planning 32 was established in order to evaluate the effects of temperature (between 37 and 43 °C) and glycerol concentration (between 1 and 5%) on hydrogen production to find the optimal values that would result in higher volumetric production of this gas. Control treatments without the addition of glycerol were also performed. The kinetics of biohydrogen production was experimentally determined and described by the Gompertz model. It was observed higher values of organic load removal for the treatments with the lowest concentrations of glycerol, despite this, the addition of glycerol provided the production of high volumes of hydrogen in concentrations ranging from 25.3 to 46.7%. The production of this biofuel in the treatments without the addition of glycerol ranged from 215.1 to 243.5 mL, while in the treatment with the addition of 3% of glycerol 1106.7 mL of hydrogen were obtained, an increase higher than 400%. On the other hand, hydrogen production per volume of treated waste was between 168.0 and 864.6 mLH2/Lresidue. The optimal conditions obtained in this study for the biodigestion process were 4% glycerol and a temperature of 38.5 °C. In these conditions, the total volume of hydrogen predicted by the model was 1093.5 mL or 854.2 mLH2/Lresidue, while the experimental value was 1102.6 mL or 861.4 mLH2/Lresidue. The analysis of the organic acids produced and the removal of the organic load showed the need for additional treatment of the effluents produced, which can be carried out with the use of physically separated acid and methanogenic phase reactors, also providing the obtaining of methane.

Dark fermentative biohydrogen production from synthetic cheese whey in an anaerobic structured-bed reactor: Performance evaluation and kinetic modeling

This study investigated the potential of dark fermentative hydrogen production from cheese whey in an acidogenic anaerobic structured-bed reactor (ASTBR). The reactor was operated at 25 °C with an organic loading rate (OLR) of 24 kg COD m−3 d−1 and a hydraulic retention time (HRT) of 24 h. The ASTBR had an average volumetric hydrogen production rate (VHPR) of 1.6 ± 0.7 L H2 L−1 d−1 and an average hydrogen yield (HY) of 1.4 ± 0.7 moL H2 mol−1 of consumed lactose. Batch experiments were performed with biomass from the ASTBR to characterize the main metabolic transformations involved in hydrogen production. An ADM1-based, unstructured kinetic model was developed and fitted to the obtained temporal profiles. The model allowed a satisfactory description of the process and indicated that hydrogen production from lactate and acetate could explain 74.5% of the total hydrogen volume produced. Because lactic-acid-producing bacteria are expected to ultimately colonize acidogenic reactors treating cheese whey, optimizing electron flow through this pathway may be a suitable strategy to enable long-term hydrogen production from cheese whey using mixed-culture fermentation.

Co-gasification of coal/sewage sludge blends to hydrogen-rich gas with the application of simulated high temperature reactor excess heat

The experimental study on oxygen and steam gasification and co-gasification of hard coal and sewage sludge to hydrogen-rich gas was performed in the laboratory scale fixed bed gasifier equipped with an auxiliary gasification agents pre-heating system, simulating the utilization of an excess High Temperature Reactor (HTR) heat. The allothermal gasification and co-gasification tests were performed on fuel blends of coal and sewage sludge of the total mass of 10 g and biowaste content of 20% and 40%w/w in three system configurations. In the first one the reactor was heated up with a resistance furnace to the temperature of 700 °C in the inert gas (nitrogen) atmosphere. When the temperature inside the reactor was stable, oxygen and steam of the temperature of approximately 100 °C were introduced into the reactor. In the second system, after the reactor was heated up to 700 °C, the heating of the reactor was switched off and oxygen and steam were pre-heated to the temperature of 700 °C and fed into the reactor. In the third system a fuel sample in the reactor was heated to the temperature 700 °C and the set temperature was maintained with the resistance furnace. The results showed that sufficient thermal energy required for an effective oxygen/steam gasification process was generated in systems with the external heating of the reactor. The highest hydrogen contents in gas were reported in coal gasification, irrespective of the system configuration. The total hydrogen volume decreased with increasing biomass content in a fuel blend in all studied system configurations.

Applying a one-dimensional PDR model to the Taurus molecular cloud and its atomic envelope

In this contribution, we test our previously published one-dimensional PDR model for deriving total hydrogen volume densities from HI column density measurements in extragalactic regions by applying it to the Taurus molecular cloud, where its predictions can be compared to available data. Also, we make the first direct detailed comparison of our model to CO(1-0) and far-infrared emission. Using an incident UV flux G0 of 4.25 ({\chi} = 5) throughout the main body of the cloud, we derive total hydrogen volume densities of \approx 430 cm-3, consistent with the extensive literature available on Taurus. The distribution of the volume densities shows a log-normal shape with a hint of a power-law shape on the high density end. We convert our volume densities to H2 column densities assuming a cloud depth of 5 parsec and compare these column densities to observed CO emission. We find a slope equivalent to a CO conversion factor relation that is on the low end of reported values for this factor in the literature (0.9 x 1020 cm-2 (K km s-1)-1), although this value is directly proportional to our assumed value of G0 as well as the cloud depth. We seem to under-predict the total hydrogen gas as compared to 100 {\mu}m dust emission, which we speculate may be caused by a higher actual G0 incident on the Taurus cloud than is generally assumed.

Hydrogen volume densities in nearby galaxies – I. An automated approach

Using a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity data, provide an independent probe of the combined atomic and molecular hydrogen gas in galactic disks. We present a new, flexible and fully automated procedure using this simple model. This automated method will allow us to take full advantage of a host of available data on galaxies in order to calculate total hydrogen volume densities of giant molecular clouds surrounding sites of recent star formation. So far this was only possible on a galaxy-by-galaxy basis using by-eye analysis of candidate photodissociation regions. We test the automated method by adopting different models for the dust-to-gas ratio and comparing the resulting densities for M74, including a new metallicity map of M74 produced by integral field spectroscopy. We test the procedure against previously published M83 volume densities based on the same method and find no significant differences. The range of total hydrogen volume densities obtained for M74 is approximately 5-700 cm-3 . Different dust-to-gas ratio models do not result in measurably different densities. The cloud densities presented here add M74 to the list of galaxies analyzed using the assumption of photodissociated atomic hydrogen occurring near sites of recent star formation and further solidify the method. For the first time, full metallicity maps were included in the analysis as opposed to metallicity gradients. The results will need to be compared to other tracers of the interstellar medium and photodissociation regions, such as CO and CII, in order to test our basic assumptions, specifically, our assumption that the HI we detect originates in photodissociation regions.

NaBH4가수분해반응에서 수소 수율에 관한 연구

휴대용 고분자전해질 연료전지의 수소발생용으로써 <TEX>$NaBH_4$</TEX>는 많은 장점을 갖고 있다. 본 연구에서는 <TEX>$NaBH_4$</TEX> 가수분해 반응의 수소 수율에 대해 연구하였다. <TEX>$NaBH_4$</TEX> 가수분해 반응의 수소 수율에 미치는 촉매 형태, 온도, <TEX>$NaBH_4$</TEX> 농도, NaOH 농도 등의 영향에 대해 실험하였다. 촉매는 Co-P/Cu, Co-B/Cu와 Co-P-B/Cu를 사용하였는데 이들 촉매 종류에 따라 <TEX>$NaBH_4$</TEX> 가수분해 반응의 수소 수율에 미치는 영향은 거의 없었다. <TEX>$60^{\circ}C$</TEX> 이하의 온도에서 <TEX>$NaBH_4$</TEX> 농도가 증가하면 부산물과 <TEX>$NaBH_4$</TEX>에 의해 겔이 형성되면서 가수분해 반응의 수소 수율이 감소였다. 겔 형성에 의해서 <TEX>$NaBH_4$</TEX> 가수분해 반응 속도와 수소 총 발생량이 감소하였다. 안정화제인 NaOH를 첨가하면 겔 형성을 촉진해 수소 수율을 감소시켰다. Sodium borohydride, <TEX>$NaBH_4$</TEX>, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). The hydrogen yield of sodium borohydride hydrolysis reaction was studied. The effect of temperature, <TEX>$NaBH_4$</TEX> concentration, NaOH concentration and catalyst type on the hydrogen yield from <TEX>$NaBH_4$</TEX> hydrolysis reaction were measured. The catalysts of Co-P/Cu, Co-B/Cu and Co-P-B/Cu were used in this study and there was no different effect of these catalysts on the hydrogen yield from <TEX>$NaBH_4$</TEX>. Under the temperature of <TEX>$60^{\circ}C$</TEX>, the hydrogen yield decreased as <TEX>$NaBH_4$</TEX> concentration increased due to formation of gel with by-products and reactants. The gel formed during <TEX>$NaBH_4$</TEX> hydrolysis reaction diminished the hydrogen evolution rate and total volume of hydrogen. Addition of NaOH stabilizer enhanced the formation of gel and then decreased the hydrogen yield.

Effect of light intensity and initial pH during hydrogen production by an integrated dark and photofermentation process

Abstract Photofermentation was carried out with the spent fermentation broth obtained from the anaerobic dark fermentation in a two-stage process. For the first stage, i.e. dark fermentation Enterobacter cloacae DM 11 was used as hydrogen producing microorganism. For photofermentation Rhodobacter sphaeroides O.U. 001, a photo-heterotrophic purple non-sulfur bacterium, was used. pH study revealed that cumulative hydrogen production was maximum at initial medium pH of 7.0 ± 0.2. Biomass yield was also high at the vicinity of pH 7.0 and it decreased as the pH increased from 7.0 to 8.0. Increased light intensity resulted in an increase in the total volume of hydrogen evolved and also hydrogen production rate. However, light conversion efficiency decreased by increasing light intensity. A four-fold increase in light intensity resulted in a three-fold decrease in light conversion efficiency although the cumulative volume of hydrogen gas production increased. It was observed that only a maximum of 0.51% light conversion efficiency could be achieved but at the expense of very low light intensity of 2500 lux (3.75 W m −2 ).

Cloning and knockout of formate hydrogen lyase and H 2-uptake hydrogenase genes in Enterobacter aerogenes for enhanced hydrogen production

A 5431-bp DNA fragment partially encoding the formate hydrogen lyase (FHL) gene cluster hycABCDE was isolated and identified from Enterobacter aerogenes IAM1183 chromosomal DNA. All the five putative gene products showed a high degree of homology to the reported bacterial FHL proteins. The gene hycA, encoding the FHL repressor protein, and hybO, encoding the small subunit of the uptake hydrogenase, were targeted for genetic knockout for improving the hydrogen production. The pYM-Red recombination system was adopted to form insertional mutations in the E. aerogenes genome, thereby creating mutant strains of IAM1183-A (△ hycA), IAM1183-O (△ hybO), and IAM1183-AO (△ hycA/△ hybO double knockout). The hydrogen production experiments with these mutants showed that the maximum specific hydrogen productivities of IAM1183-A, IAM1183-O, and IAM1183-AO were 2879.466 ± 38.59, 2747.203 ± 13.25 and 3372.019 ± 4.39 (ml h −1 g −1dry cell weight), respectively, higher than that of the wild strain (2321.861 ± 15.34 ml h −1 g −1dry cell weight). The total H 2 yields by the three mutants IAM1183-A, IAM1183-O and IAM1183-AO were 0.73, 0.78, and 0.83 mol-H 2/mol glucose, respectively, while the wild-type IAM1183 was only 0.65 mol-H 2/mol glucose. The metabolites of the mutants including acetate, ethanol, 2,3-butanediol and succinate were all increased compared with that of the wild type, implying the changed metabolic flux by the mutation. In the fermentor cultivation with IAM1183△ hycA/△ hybO, the total hydrogen volume after 16 h cultivation reached 4.4 L, while that for the wild type was only 2.9 L.

Effect of Partial Shading on Photoproduction of Hydrogen by Chlorella

The photoproduction of hydrogen by the green alga Chlorella pyrenoidosa was studied in 650-ml bubble columns made of glass with 7 cm diameter. Hydrogen was produced by adding sodium dithionite as an oxygen scavenger directly to an algal suspension. When a part of the wall of the bubble column was shaded with a sheet of plastic film impervious to light, the production rate and total volume of hydrogen increased as compared to those in the columns without partial shading. This relationship between the hydrogen photoevolution rate and the proportion of lighted region is contrary to normal photochemical reactions. This phenomenon is considered to be related to the regulation by light of the activity of the enzymes and/or the photosynthetic electron transport systems, which was examined by measuring fluorescence induction curves of dark-adapted Chlorella cells and also the distribution of light intensity within the bubble column bioreactors.

Simulation of the daily sunlight illumination pattern for bacterial photo-hydrogen production

Methods of illumination to simulate the daily sunlight irradiation pattern were studied in relation to photohydrogen production using the photosynthetic bacterium Rhodobacter sphaeroides RV. Three illumination patterns were compared, in which the light intensity was changed in 1, 3, or 6 steps. As a control, outdoor experiments were also carried out over a 3-d period in Tsukuba, August 1996. Outdoors, hydrogen production by Rba. sphaeroides RV was dependent on the sunlight intensity: the total volume of hydrogen produced per day varied from 14 to 28 l·m −2, while the total light energy ranged from 5.5 to 6.4 kWh·m −2· d −1. The maximum hydrogen production rate was 2.8 l·m −2·h −1 under a 4.5-cm light path and the average light energy conversion efficiency was 1.1%. Indoors, the hydrogen production rate was found to be independent of the mode of illumination among the three patterns employed. The maximum hydrogen production rate was 3.3 l·m −2·h −1 with a light energy conversion efficiency of 1.0%, and it was concluded that the single-step illumination method provides an appropriate simulation of sunlight. Saturation of hydrogen production occurs during high light intensity around noon and this plays a key role in the simulation.

Valency of Ions Formed during Anodic Dissolution of Metals in Acids

The charge of cations of active metals, going anodically into solution in acid or alkaline electrolytes, can be computed from the current applied and the total hydrogen evolution rate after the initial, self‐dissolution rate has been subtracted. However, under such conditions an ionic charge, experimentally not provable, of much higher or lower value than the normal one is calculated. Evidently this charge is apparent and corresponds to the true one only then, if the self‐dissolution rate does not change when the anodic current is applied.It can be shown (by measuring the total hydrogen volume developed) that calculated abnormal valencies result when the change of self‐dissolution rate (difference effect) due to the anodic current is disregarded. In the case of the positive effect, high charges and, in the case of the negative effect, low (apparent) cationic charges are computed. The impossibility of the calculated high cationic charges proves in turn that the positive effect cannot be explained by the expulsion of such cations by the anode. Since it was shown at least in the case of Be (which also might be true with Mg) that the metal partially disintegrated into tiny metal particles under the influence of the anodic current, the need for the assumption of Be+ formation is removed. The appearance of the negative A effect can be explained in a better way.All the phenomena occurring in the anodic compartment in acidic as well as neutral solutions can be explained readily by the consequences of the altered self‐dissolution rates, especially if the activation of the dissolving surface of the anodic metal, the breakdown of the protective films, and the formation of metal fragments by the anodic current are considered.