scholarly journals Impacts of Nickel Nanoparticles on Mineral Carbonation

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Marius Bodor ◽  
Rafael M. Santos ◽  
Yi Wai Chiang ◽  
Maria Vlad ◽  
Tom Van Gerven
Keyword(s):  
Reaction Time ◽  
Nickel Nanoparticles ◽  
Carbonic Acid ◽  
Mineral Carbonation ◽  
Ph Values ◽  
Bicarbonate Ions ◽  
Steelmaking Slags ◽  
Initial Stage ◽  
Solids Content ◽  
Rate Limiting

This work presents experimental results regarding the use of pure nickel nanoparticles (NiNP) as a mineral carbonation additive. The aim was to confirm if the catalytic effect of NiNP, which has been reported to increase the dissolution of CO2and the dissociation of carbonic acid in water, is capable of accelerating mineral carbonation processes. The impacts of NiNP on the CO2mineralization by four alkaline materials (pure CaO and MgO, and AOD and CC steelmaking slags), on the product mineralogy, on the particle size distribution, and on the morphology of resulting materials were investigated. NiNP-containing solution was found to reach more acidic pH values upon CO2bubbling, confirming a higher quantity of bicarbonate ions. This effect resulted in acceleration of mineral carbonation in the first fifteen minutes of reaction time when NiNP was present. After this initial stage, however, no benefit of NiNP addition was seen, resulting in very similar carbonation extents after one hour of reaction time. It was also found that increasing solids content decreased the benefit of NiNP, even in the early stages. These results suggest that NiNP has little contribution to mineral carbonation processes when the dissolution of alkaline earth metals is rate limiting.

scholarly journals Mechanism of d-fructose isomerization by Arthrobacterd-xylose isomerase

1992 ◽  
Vol 283 (1) ◽  
pp. 223-233 ◽  
Author(s):  
M Rangarajan ◽  
B S Hartley
Keyword(s):  
Ring Opening ◽  
Ph Dependence ◽  
Xylose Isomerase ◽  
Competitive Inhibitor ◽  
Apparent Dissociation Constant ◽  
Ph Values ◽  
Rate Limiting Step ◽  
Competitive Inhibitors ◽  
Rate Limiting ◽  
Very High

The mechanism of D-fructose isomerization by Arthrobacter D-xylose isomerase suggested from X-ray-crystallographic studies was tested by detailed kinetic analysis of the enzyme with various metal ions at different pH values and temperatures. At D-fructose concentrations used in commercial processes Mg2+ is the best activator with an apparent dissociation constant of 63 microM; Co2+ and Mn2+ bind more strongly (apparent Kd 20 microM and 10 microM respectively) but give less activity (45% and 8% respectively). Ca2+ is a strict competitive inhibitor versus Mg2+ (Ki 3 microM) or Co2+ (Ki 105 microM). The kinetics show a compulsory order of binding; Co2+ binds first to Site 2 and then to Site 1; then D-fructose binds at Site 1. At normal concentrations Mg2+ binds at Site 1, then D-fructose and then Mg2+ at Site 2. At very high Mg2+ concentrations (greater than 10 mM) the order is Mg2+ at Site 1, Mg2+ at Site 2, then D-fructose. The turnover rate (kcat.) is controlled by ionization of a residue with apparent pKa at 30 degrees C of 6.0 +/- 0.07 (Mg2+) or 5.3 +/- 0.08 (Co2+) and delta H = 23.5 kJ/mol. This appears to be His-219, which is co-ordinated to M[2]; protonation destroys isomerization by displacing M[2]; Co2+ binds more strongly at Site 2 than Mg2+, so competes more strongly against H+. The inhibition constant (Ki) for the two competitive inhibitors 5-thio-alpha-D-glucopyranose and D-sorbitol is invariant with pH, but Km(app.) in the Mg[1]-enzyme is controlled by ionization of a group with pKa 6.8 +/- 0.07 and delta H = 27 kJ/mol, which appears to be His-53. This shows that Km(app.) is a complex constant that includes the rate of the ring-opening step catalysed by His-53, which explains the pH-dependence. In the Mg[1]Mg[2]-enzyme or Co[1]Co[2]-enzyme, the pKa is lower (6.2 +/- 0.1 or 5.6 +/- 0.08) because of the extra adjacent cation. Hence the results fit the previously proposed pathway, but show that the mechanisms differ for Mg2+ and Co2+ and that the rate-limiting step is isomerization and not ring-opening as previously postulated.

scholarly journals Outdoor Large-Scale Cultivation of the Acidophilic Microalga Coccomyxa onubensis in a Vertical Close Photobioreactor for Lutein Production

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 324 ◽  
Author(s):  
Juan-Luis Fuentes ◽  
Zaida Montero ◽  
María Cuaresma ◽  
Mari-Carmen Ruiz-Domínguez ◽  
Benito Mogedas ◽  
...  
Keyword(s):  
Biomass Production ◽  
Large Scale ◽  
Culture Conditions ◽  
High Concentration ◽  
Ph Values ◽  
Lutein Content ◽  
Acidic Waters ◽  
Large Scale Cultivation ◽  
Rate Limiting ◽  
Lutein Production

The large-scale biomass production is an essential step in the biotechnological applications of microalgae. Coccomyxa onubensis is an acidophilic microalga isolated from the highly acidic waters of Río Tinto (province of Huelva, Spain) and has been shown to accumulate a high concentration of lutein (9.7 mg g−1dw), a valuable antioxidant, when grown at laboratory-scale. A productivity of 0.14 g L−1 d−1 was obtained by growing the microalga under outdoor conditions in an 800 L tubular photobioreactor. The results show a stable biomass production for at least one month and with a lutein content of 10 mg g−1dw, at pH values in the range 2.5–3.0 and temperature in the range 10–25 °C. Culture density, temperature, and CO2 availability in highly acidic medium are rate-limiting conditions for the microalgal growth. These aspects are discussed in this paper in order to improve the outdoor culture conditions for competitive applications of C. onubensis.

scholarly journals Sulfamethoxazole and Trimethoprim Degradation by Fenton and Fenton-Like Processes

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1655 ◽  
Author(s):  
Antover Panazzolo Sarmento ◽  
Alisson Carraro Borges ◽  
Antonio Teixeira de Matos ◽  
Lincoln Lucílio Romualdo
Keyword(s):  
Reaction Time ◽  
Fenton Reaction ◽  
Desirability Function ◽  
Relative Concentration ◽  
Optimum Conditions ◽  
Degradation Model ◽  
Pareto Chart ◽  
Linear Effect ◽  
Ph Values ◽  
Antibiotic Degradation

In this work, the degradation of sulfamethoxazole (SMX) and trimethoprim (TMP) via Fenton and Fenton-like processes was evaluated using Mn2+ as supporting catalyst in the Fenton reaction. The optimum conditions of degradation were also evaluated. Besides that, the effect of independent factors pH, [H2O2], [Fe2+], [Mn2+] and reaction time (t) on the efficiency of the SMX and TMP degradation were assessed. Box–Behnken was the experimental design adopted, delineating the relative concentration (C/Co) of antibiotics after treatments as response variable. The inferences were conducted using variance analysis, Pareto chart, response surface methodology, and desirability function. Due to the lack of adjustment of the SMX degradation model, there are no more inferences about it. The significant variables (p ≤ 0.05) on TMP degradation were: reaction time quadratic and linear effect, [Fe2+] linear effect, [Mn2+] linear effect, interaction pH vs. [Mn2+]. The Mn2+ addition aided TMP degradation in environments with lower pH values. However, the addition may harm the efficiency of the antibiotic degradation at higher pH. The optimum condition for TMP degradation in the conventional process (without the addition of Mn2+) is: pH 5, [H2O2] equal to 4.41 mmol L−1, [Fe2+] equal to 0.81 mmol L−1 and 90 min reaction time.

Preliminary Study on the Removal of Hexavalent Chromium in Wastewater with Reduction of Sulfur Dioxide

2013 ◽  
Vol 864-867 ◽  
pp. 1699-1703
Author(s):  
Ji Ming Wu ◽  
Sheng Gao Cheng
Keyword(s):  
Reaction Time ◽  
Sulfur Dioxide ◽  
Hexavalent Chromium ◽  
Reduction Reaction ◽  
High Concentration ◽  
Reaction Conditions ◽  
Ph Values ◽  
Different Temperatures ◽  
Preliminary Study ◽  
High Concentrations

The paper focused on a self-developed methodology through using sulfur dioxide to deal with high concentration of chromium-containing wastewater. It studied the effects of different pH values, different reaction time, different temperatures and different amounts of sulfur with sulfur dioxide reduction reaction on the chromium-containing wastewater. The results showed that: when the reaction conditions were controlled as follows: the pH values ranged from 2 to 4, the reaction temperature was controlled 40~60°C, the amount of sulfur in theoretical was 1.2 times and the reaction time was 40 min, the hexavalent chromium in the high concentrations of chromium-containing wastewater could be effectively removed.

Photochemisch initiierte Telomerisation von Äthylen mit Formamid / Photo-Initiated Telomerization of Ethylene with Formamide

1975 ◽  
Vol 30 (9-10) ◽  
pp. 740-747 ◽  
Author(s):  
H. P. Rath ◽  
A. Saus ◽  
B. Dederichs
Keyword(s):  
High Pressure ◽  
Reaction Time ◽  
Low Temperatures ◽  
Carbonic Acid ◽  
Uv Light ◽  
Electrical Power ◽  
Power Input ◽  
Elevated Pressure ◽  
Reaction Pressure ◽  
Geometrical Progression

Under the influence of UV light (high pressure HPK 125, Philips) and in presence of acetone ethylene and formamide react under elevated pressure (12.5-100 kp/cm2) to give odd-numbered n-alkane carbonic acid amides of chain lenghth C3-C19. Product yields improve with rising pressure. By increasing the concentration of aceton (0.1-8 mol-%), the reaction pressure the reaction time and at low temperatures the average mol.-weight is shifted to higher values. The chain distribution corresponds to a geometrical progression. Per 1 kwh electrical power input of the uv-equipment 0.5 kg of product is formed with chain length: 78% C3-C7, 12% C9, 10% C11-C19.

scholarly journals Estimation and impact of carbon dioxide capture on drinking water: Tillmans equilibrium diagram

2019 ◽  
Vol 11 (2) ◽  
pp. 380-389
Author(s):  
C. Alvarez-Bastida ◽  
M. Solache-Ríos ◽  
I. Linares-Hernández ◽  
G. Vázquez-Mejía ◽  
G. Fonseca-Montes de Oca ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Drinking Water ◽  
Carbonic Acid ◽  
Carbon Dioxide Capture ◽  
Equilibrium Diagram ◽  
Cation Composition ◽  
Bicarbonate Ions ◽  
Different Seasons ◽  
User Friendly ◽  
The Impact

Abstract The increase of CO2 in the atmosphere may produce some effects on drinking water because water tends to naturally capture CO2 species. The main purpose was the study of the impact of capture of free CO2 and its transformation to carbonic acid (H2CO3) and bicarbonate ions (HCO−3). The study used a Tillmans equilibrium diagram obtained from the modified Mojmir Mach model as a function of water temperature and considered the effects on anion and cation composition. Three wells located in different zones were selected, with similar characteristics (capture of CO2). Samples were taken in different seasons of the year and the amount of CO2 in the drinking water was calculated. It was found that with increasing concentrations of free CO2 the pH decreases, and this process makes the water acid and susceptible to dissolve some elements (Ca, Na, K, Si) and other species (HCO−3). The capture of CO2 has important effects on the anion and cation composition of drinking water and on the variation of pH by more than one unit, which may affect the health of consumers. The method presented in this study is an excellent user-friendly alternative to determine the impact of natural capture of total CO2 by water.

Gelcasting of Fused Quartz Crucible with Large Scale

2012 ◽  
Vol 512-515 ◽  
pp. 399-402 ◽  
Author(s):  
Cheng Gong Sun ◽  
Jin Ye Niu ◽  
Hai Jian Li ◽  
Qiang Lian ◽  
Hai Jie Yu ◽  
...  
Keyword(s):  
Coupling Agent ◽  
Large Scale ◽  
Bending Strength ◽  
Volume Density ◽  
Curing Temperature ◽  
Quartz Crucible ◽  
Ph Values ◽  
Fused Quartz ◽  
Solids Content

Fused Quartz crucible with large scale was formed by gelcasting processing in this paper. Effects of dispersant, pH values and particle grading on solids content of slurries were discussed to increase the volume density of the green compacts and decrease the shrinkage and deformation during sintering. Effects of acrylamide content and the ratio of acrylamide to coupling agent on bending strength of the green compacts were investigated. Effects of the amount of initiator and curing temperature on the gelcasting processing were studied as well. The green compacts with solids content of 80% was obtained when the addition ratio of dispersant to Quartz powders was 0.3wt %, the ratio of Quartz powders in D50 of 1.9μm and 7.6μm was adjusted to 3:7, the addition ratio of acrylamide to Quartz powders was 1.0wt % and the ratio of acrylamide to coupling agent was 16:1. The bending strength of the sinterred produts was found to be 76.0MPa with volume density of 1.94 g/cm2. Fused Quartz crucible prepared under conditions mentioned above was 800mm in length, 800mm in width and 400mm in height.

The influence of pH on kinetic parameters of coleoptile phosphoenolpyruvate carboxylase. Relationship to auxin-stimulated dark fixation

1979 ◽  
Vol 57 (5) ◽  
pp. 543-547 ◽  
Author(s):  
Ceredwyn Smith ◽  
Ahmed Doo ◽  
Alan W. Bown
Keyword(s):  
Binding Affinity ◽  
Catalytic Efficiency ◽  
Enzymic Activity ◽  
Carboxylase Activity ◽  
Pep Carboxylase ◽  
Ph Values ◽  
Dark Fixation ◽  
Rate Limiting ◽  
Cytosol Ph

In vitro phosphoenolpyruvate (PEP) carboxylase activity from Avena coleoptile tissue was investigated over a range of pH values which include cytosol pH values. Increasing the pH from 7.0 to 7.5 increased optimal PEP carboxylase activity (Vmax) by over 100%. In the presence of rate-limiting 0.07 mM PEP, noncompetitive inhibition by 0.1 mM malate decreased from 80% at pH 7.1 to 50% at pH 7.5. The Km for PEP was not influenced by malate, but as the pH was increased from 7.1 to 7.5, the Km decreased from 0.16 to 0.08 mM. Over the same pH rise, the KI for malate inhibition increased from 0.04 mM to 0.09 mM. Fusicoccin had no detectable influence on enzymic activity. These results are discussed in relation to the stimulation of H+ excretion and dark CO2 fixation by indoleacetic acid and fusicoccin. The data indicate that any increase in cytosol pH, resulting from H+ excretion, would stimulate PEP carboxylase activity by promoting catalytic efficiency and binding affinity for PEP and by reducing the binding affinity for the inhibitor malate.

scholarly journals Kinetics of the diamine oxidase reaction

1973 ◽  
Vol 131 (3) ◽  
pp. 459-469 ◽  
Author(s):  
William G. Bardsley ◽  
M. James C. Crabbe ◽  
Julian S. Shindler
Keyword(s):  
Diamine Oxidase ◽  
Experimental Conditions ◽  
Ph Values ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Deuterium Substitution ◽  
Effects Of Temperature ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Oxidase Reaction

1. The oxidation of p-dimethylaminomethylbenzylamine was followed spectrophotometrically by measuring the change in E250 caused by the p-dimethylaminomethylbenzaldehyde produced under a wide variety of experimental conditions. 2. The effect of variations in concentrations of both substrates (amine and oxygen) and all products (aminoaldehyde, hydrogen peroxide and ammonia) on this reaction was studied and the results used to develop a formal mechanism. 3. The nature of the rate-limiting step was elucidated by studying the effects of alterations in ionic strength, dielectric constant and deuterium substitution on the velocity of the forward reaction. 4. Thermodynamic activation energy parameters were obtained at several pH values from the effects of temperature on the reaction.

Sign in / Sign up

Export Citation Format

Share Document