Addition Of Ferrocyanide Research Articles

Effect of a mixed-in crystallization inhibitor on the properties of hydraulic mortars

<abstract> <p>Porous building materials are often subjected to damage due to salt crystallization. In recent years, the addition of crystallization inhibitors in lime-based mortar, has shown promising results in improving durability of this material against salt decay. Lime-based mortars have low mechanical properties and slow setting. They are often replaced with hydraulic binders to overcome these limitations. However, the effect of crystallization inhibitors in mortars with hydraulic binders is still unknown. Incorporation of crystallization inhibitors in hydraulic mortars would widen the application field of this new technology. In this research, the possibility to develop hydraulic mortars with mixed-in sodium ferrocyanide, an inhibitor of sodium chloride crystallization, is explored. As an essential first step, the influence of this inhibitor addition on the properties of hydraulic mortars is investigated. Two common types of hydraulic binders, natural hydraulic lime (NHL) and ordinary Portland cement (CEM I), were studied; the inhibitor was added in different amounts (0%, 0.1% and 1% by binder weight) during mortar (and binder paste) preparation. Relevant mortar and binder paste properties, in fresh (hydration, workability, setting time) and hardened (mechanical strength, elastic modulus, pore size distribution, water absorption) state, were assessed using several complementary methods and techniques. The results indicate that the addition of ferrocyanide does not alter the studied properties of both NHL and CEMI-based mortar and binder pastes. These results are promising for the further development of hydraulic mortars with an improved durability with respect to salt decay.</p> </abstract>

Determination of Cd and Zn with “green” screen-printed electrodes modified with instantly prepared sparked tin nanoparticles

Graphite screen-printed electrodes (GSPEs) modified with tin nanoparticles (SnNPs) through a “green”, fast and extremely facile sparking process were used for the anodic stripping voltammetric determination of trace Cd and Zn. The effect of the magnitude of the energy dissipated during sparking events as well as other sparking parameters on the amount of the deposited tin, the morphology of the sparked surfaces and the electroanalytical properties of SnNP/GSPEs were investigated. Experiments were performed in the presence of bromide ions, which were used to enable well-resolved stripping peaks for cadmium. Other experimental variables, such as the pH of the supporting electrolyte, the square wave voltammetry parameters, the concentration of bromide ions, the deposition potential and the deposition time were also examined. Copper interference on Cd and Zn detection was effectively alleviated by the addition of ferrocyanide and gallium ions, respectively. Under selected conditions, the limits of detection, for a 2 min preconcentration time, were 0.5 μg L−1 Cd and 0.3 μg L−1 Zn. SnNP/GSPEs were successfully applied to the determination of Cd and Zn in tap and bottled water samples. Results suggest that sparked SnNP/GSPEs represent a new promising type of environmentally friendly sensors for the determination of Cd and Zn in the sub-microgram-per-liter level that surpass those previously given in the literature in terms of simplicity, cost, time, labor effort, waste loadings of the modification procedure, and low cost of the final sensor.

Lithographically fabricated disposable bismuth-film electrodes for the trace determination of Pb(II) and Cd(II) by anodic stripping voltammetry

This work reports the photolithographic fabrication of disposable bismuth-film electrodes (BiFEs) using a thin-film deposition approach. The deposition of the bismuth layer was carried out by sputtering of metallic bismuth on a silicon substrate while the exact geometry of the BiFEs was produced by photolithography. The utility of these sensors was tested for the simultaneous trace determination of Cd(II) and Pb(II) by square wave anodic stripping voltammetry (SWASV). Using the selected conditions, the limits of detection were 0.5 μg l −1 for Pb(II) and 1 μg l −1 for Cd(II) at a preconcentration time of 4 min. The interference caused by Cu(II) was alleviated by the addition of ferrocyanide in the sample solution. Finally, the proposed BiFEs were successfully applied to the determination of Cd and Pb in a phosphate fertilizer and a river water sample. These sensors offer wide scope for trace metal analysis in terms of mass-production of mercury-free disposable sensors with performance comparable to their mercury counterparts.

Inhibition of pea ferredoxin-NADP(H) reductase by Zn-ferrocyanide.

Ferredoxin-NADP(H) reductases (FNRs) represent a prototype of enzymes involved in numerous metabolic pathways. We found that pea FNR ferricyanide diaphorase activity was inhibited by Zn2+ (Ki 1.57 microM). Dichlorophenolindophenol diaphorase activity was also inhibited by Zn2+ (Ki 1.80 microM), but the addition of ferrocyanide was required, indicating that the inhibitor is an arrangement of both ions. Escherichia coli FNR was also inhibited by Zn-ferrocyanide, suggesting that inhibition is a consequence of common structural features of these flavoenzymes. The inhibitor behaves in a noncompetitive manner for NADPH and for artificial electron acceptors. Analysis of the oxidation state of the flavin during catalysis in the presence of the inhibitor suggests that the electron-transfer process between NADPH and the flavin is not significantly altered, and that the transfer between the flavin and the second substrate is mainly affected. Zn-ferrocyanide interacts with the reductase, probably increasing the accessibility of the prosthetic group to the solvent. Ferredoxin reduction was also inhibited by Zn-ferrocyanide in a noncompetitive manner, but the observed Ki was about nine times higher than those for the diaphorase reactions. The electron transfer to Anabaena flavodoxin was not affected by Zn-ferrocyanide. Binding of the apoflavodoxin to the reductase was sufficient to overcome the inhibition by Zn-ferrocyanide, suggesting that the interaction of FNRs with their proteinaceous electron partners may induce a conformational change in the reductase that alters or completely prevents the inhibitory effect.

Comparative study of the effect of ferrocyanide and EDTA on the production of ethyl alcohol from molasses by Saccharomyces cerevisiae

The effects of potassium ferrocyanide and EDTA on ethyl alcohol production from molasses by Saccharomyces cerevisiae were investigated on simulated batch pilotplant-scale conditions for alcoholic fermentation of molasses. Ethyl alcohol production was more sensitive to ferrocyanide than to EDTA. When ferrocyanide was introduced into the cultures at the time of inoculation, there was stimulation of ethyl alcohol production, with 261 ppm ferrocyanide producing the maximum effect, which was 3.0% more than in control cultures. When added during the propagation of the yeast, ferrocyanide depressed ethyl alcohol production by 4.0% maximum whereas EDTA stimulated ethyl alcohol production by 2.0%. Addition of ferrocyanide during the fermentation stage produced no significant effect on alcohol production, whereas over a wide range of EDTA concentration there was a steady increase in alcohol yield.

The relationship of some metal ions with citric acid production by Aspergillus niger using tamarind seed powder as raw material

Tamarind seed powder (TSP) was used as raw material for microbial production of citric acid. The maximum citric acid production was observed when the TSP-basal medium (TSP with inorganic nitrogen and phosphorus source) was supplemented with Mg 2+, Fe 2+, Cu 2+ and Zn 2+. The use of methanol and ferrocyanide as a modulator for citric acid production was studied. On methanol supplementation to the medium, ammonium nitrate was found to be better than ammonium carbonate as a source of inorganic nitrogen. Addition of ferrocyanide after sterilization to the medium containing methanol gave the maximum citrate production of 363 μg/ml.

PRODUCTION OF CITRIC ACID FROM CANE MOLASSES ON A SEMI-PILOT SCALE

Up to 59.73% yield and 69% conversion coefficient of citric acid were obtained on using Naga-Hammade or Abou-Korkas black strap cane molasses. The molasses was simply clarified by centrifugation and supplemented with 0.2% NH4NO3. Methanol was better than ethanol, and 2.5% methanol was added before inoculation. Inoculation was performed by spraying the spores over the surface of the fermentation medium. Stainless steel trays proved to be resistant to prolonged use against deformation. Addition of potassium ferrocyanide in the presence of 2.5% methanol did not increase the yield of the acid. In the absence of methanol, addition of the ferrocyanide at a concentration of 0.15% doubles the yield of the acid.

Two modes of inhibition by 2-heptyl-4-hydroxyquinoline- <italic>N</italic>-oxide of electron transport associated with photosystem 2 in spinach chloroplasts

2-Heptyl-4-hydroxyquinoline-N-oxide (HOQNO) exerted two modes of inhibition on the Hill reaction in spinach chloroplasts. The first mode of inhibition by HOQNO, which developed rapidly and reversibly on addition of the inhibitor to chloroplasts, was observed in the Hill reaction with various electron acceptors and in photoreduction of methyl viologen with ascorbate as electron donor, but was not observed in methyl viologen photoreduction supported by reduced DPIP. Fifty percent inhibition of the Hill reaction was obtained with HOQNO at a low concentration of the order of 10−6 M. Besides the fast-developing inhibition, HOQNO caused a progressive decrease in the Hill activity during the reaction when ferrricyanide was used as electron acceptor. Similar time-dependent inactivation occurred when chloroplasts were incubated with HOQNO and ferricyanide in the dark. Chloroplasts, thus inactivated, showed lowered activity for ascorbate-supported methyl viologen photoreduction but had unchanged activity for photoreduction with reduced DPIP as electron donor. Progress of the time-dependent inhibition was accelerated by increasing the concentration of HOQNO or ferricyanide and was suppressed by addition of ferrocyanide. On changing the ratio of ferri- to ferrocyanide in the reaction medium, fifty percent protection of the Hill activity was obtained with a ferri- and ferrocyanide mixture giving the redoxpotential of 560 mv. A simple kinetic model for the second time-dependent inhibition by HOQNO is presented.

Kinetics of arsenite-ferricyanide reaction in an alkaline medium

The kinetics of the oxidation of arsenite to arsenate by ferricyanide has been studied in an alkaline medium. At low alkali concentrations the reaction is very slow and the reaction rates have therefore been determined in highly alkaline media (OH − > 10 −2M). The overall kinetics are first order in ferricyanide, arsenite and hydroxide ions. Addition of neutral salts viz. KCl and K 2SO 4 has a pronounced accelerating effect. Addition of ferrocyanide has no effect while methanol considerably lowers the reaction rate. The temperature coefficient of the reaction has been found to be unusually low. The energy and entropy of activation have been obtained as 8·2 Kcal and −42·8 cal. deg −1 mole −1 respectively. A mechanism has been proposed which involves the primary equilibria between various arsenite species and the hydroxide ions and is followed by the rate determining bimolecular reaction between a tribasic arsenite ion and ferricyanide.

A New Determination Method of Relative Rate Constants for Reactions with OH-radicals in Radiolysis of Aqueous Solutions

Abstract Radioactivity of water increased linearly with dose when aqueous solution of 3H-formate (2 μCi/ml and 2×10−8 m) was irradiated with γ-rays in the presence of oxygen. The increase of the radioactivity was found to be reciprocally proportional to the non-labeled formate concentration where the amount of 3H-formate was kept invariable. Addition of ferrocyanide and 2-propanol, effective OH-radicals scavengers, depressed the radioactivity increase to near zero. These facts show that the abstraction of tritium from 3H-formate by OH-radicals causes the increase of the radioactivity of water. A competition method to measure relative rate constants for reactions with OH-radicals was deviced on the present results. Some values obtained by this method were in agreement with published data.

LIGHT REACTION SYSTEMS IN CYANOPHYCEAE*

Abstract— In the blue green algae, Phormidium uncinatum and Ph. autumnale, movement in the dark is arrested by 2 × 10‐‐4 M DCPIP†, whereas photokinesis, i.e. the acceleration of the movement by light, is not markedly impaired. Thus at this concentration movement occurs in the light, but not in the dark. Obviously, the dark movement is coupled with oxidative phosphoiylation and the inhibitory effect of DCPLP is probably due to trapping of electrons from the cytochrome chain and uncoupling of the oxidative phosphorylation whereas photophosphorylation in vivo is not uncoupled and accordingly photokinesis is not inhibited. On the other hand, the dark movement is not influenced by 10‐‐4 M DCMU, a high concentration, which otherwise stops both cyclic and non‐cyclic photophosphorylation and hence photokinesis. The inhibition by DCMU of that part of the light induced movement which is due to non‐cyclic phosphorylation is reversible by the addition of ferrocyanide (10‐‐2 to 10‐‐4 M) as external electron donor.The photo‐phobotactic response is less sensitive to DCMU and is not completely suppressed even at 10‐‐3 M. The inhibition is not significantly reversible by the addition of ferrocyanide. However, 10‐‐4 M DCPIP, that does not considerably impair photokinesis, suppresses the photo‐phobotactic responx completely. Thus, contrary to Links' hypothesis, photo‐phobotaxis cannot be linked with photophosphorylation. But there is some evidence that photo‐phobotaxis is coupled with the non‐cyclic electron transport of photosynthesis at another point, which seems to lie between electron supply from oxygen and the inhibition point of DCMU, probably in the region of the acmssory pigments.

Decomposition of hydrogen peroxide by sodium nitroprusside

The photochemical after-effect in the reaction between hydrogen peroxide and sodium nitroprusside is due to the photo-formation of sodium aquopentacyanoferrate. The formation of aquopentacyanoferrate in pre-insolated nitroprusside solution has been proved by qualitative tests. Colloidal Prussian blue does not cause the after-effect. Pre-insolated nitroprusside continues to react in the dark in the manner indicated by the after-effect. Addition of ferrocyanide causes the reduction of aquopentacyanoferrate to aquopentacyanoferrite, which decomposes hydrogen peroxide with a high velocity. The validity of the suggested mechanism for the after reaction has been tested by the effect of potassium cyanide and sodium nitrite, which have been shown to suppress the after-effect by converting aquopentacyanoferrate to ferrocyanide and nitroprusside respectively. Sodium aquopentacyanoferrate, prepared in the laboratory and added to hydrogen peroxide-uninsolated nitroprusside mixture in the dark in presence and absence of ferrocyanide, has been shown to reproduce the observations obtained by insolation.