Halide Concentration Research Articles

Controlled eco-friendly shrink-resist finishing of wool using bromelain

Shrink-resist finishing is imperative to introduce dimensional stability and characteristic handle for wider acceptance of woolen garments. Conventionally used oxidative anti-felting treatments using sodium hypochlorite, gaseous chlorine, dichloroisocyanuric acid etc. release chlorine leading to high concentration of absorbable organic halides in waste water; application of resin results in stiffer handle because of spot welding effect. In contrast, enzymatic processing using protease is a sustainable alternative to substitute eco-hazardous conventional processes though diffusion of protease deep inside the wool in alkaline pH is the major concern for substantial weight as well as tensile loss thus limiting its application on wool. Treatment with bromelain even at very mild alkaline pH around 7.5 in absence of salt results in considerable damage in wool structure with consequence of higher weight and tensile loss due to partial/complete removal of cuticles on the surface. In this work, bromelain, a type of proteolytic enzyme, was used along with salt in acidic pH for controlled superficial hydrolysis of wool. A two-step acidic bromelain treatment was opted first using Box–Behnken design keeping in view minimum area shrinkage succeeded by optimization of the treatment parameters to achieve least area-shrinkage, weight loss, strength loss along with improved subjective softness. Controlled adsorption of bromelain at the outer surface of wool in presence of salt at pH ∼6 was observed yielding desirable anti-felting behaviour with minimum weight and strength loss. In contrast to conventional chlorine based technologies, acidic bromelain may be used in presence of sodium chloride to yield machine washable wool possessing minimum loss in weight and tensile strength both at industrial level.

Effect of halide concentration on tribocorrosion behaviour of 304SS in artificial seawater

Recently, increasing efforts have been made to study the tribocorrosion mechanism and influencing factors, and yet little relevant to the influence of electrolyte characteristics. In this work, the dependence of tribocorrosion on halide ions concentration in seawater is taken into consideration, and it follows that halide can improve solution lubricity and reduce friction coefficient and wear rate remarkably. However, high halide ions concentration may increase the corrosion susceptibility of 304SS, especially pitting susceptibility. Although over the entire range of halide ions concentration corrosion and wear interact positively, high halide ions concentration is beneficial for decreasing total material loss.

Towards a Mechanistic Understanding of Platinum Thin Film Deposition on Au(111)

Pt group metals and alloys thereof have important application as magnetic thin film materials and catalysts for fuel cell applications. The production of ultrathin Pt group metals thin films currently relies on surface-limited place-exchange, requiring the time-consuming exchange of electrolyte, and resulting in films with a possibility of metallic impurities. A new method was recently reported for the production of thin films through the use of large overpotential deposition of Pt on Au(111) using Pt(II) electrolytes with a high halide concentration. Under these conditions, two-dimensional islands form, and three-dimensional growth is inhibited. The mechanisms of this two-dimensional deposition and the self-termination are not completely understood, although experimental evidence suggests that the self-termination is due to underpotential deposited hydrogen blocking the surface of the newly-formed platinum film, preventing additional layers from growing. We use computational techniques coupled with electrochemical experiments to probe the reaction pathway and associated barriers to gain more insight into the growth process and its extendability to other metals.

Kinetic Screening for the Acid‐Catalyzed Hydrolysis of Some Hydrophobic Fe(II) Schiff Base Amino Acid Chelates and Reactivity Trends in the Presence of Alkali Halide and Surfactant

ABSTRACTKinetics of acid‐catalyzed hydrolysis of some high‐spin Fe(II) Schiff base amino acid complexes were followed spectrophotometrically at 298 K under pseudo–first‐order conditions. The studied ligands were derived from the condensation of 5‐bromosalicylaldehyde with different four amino acids (phenylalanine, aspartic acid, histidine, and arginine). The acid hydrolysis reaction was studied in aqueous media and in the presence of different concentrations of the alkali halide (KBr) and cationic surfactant (cetyl‐trimethyl ammonium bromide, CTAB). The general rate equation was suggested to be rate = kobs[complex], where kobs = k2[H+]. The increase in [KBr] enhances the reactivity of the reaction, and the addition of CTAB to the reaction mixture accelerates the reaction reactivity. The obtained kinetic data were used to determine the values of δmΔG# (the change in the activation barrier) for the studied complexes when transferred from “water to water containing different [KBr]” and from “water to water containing altered [CTAB].”

Electrochemical Characterization of the Bi(111) | 1-Butyl-3-Methylimidazolium Iodide Interface

The need for alternative high energy and power density energy sources has led scientists to study extensively the electrochemical energy conversion/storage devices such as electrochemical double layer capacitors (EDLC), batteries, fuel cells, etc. The values of power and energy densities of EDLC depend strongly on the properties of the electrode material and electrolyte used. EDLCs based on non-aqueous electrolytes or room temperature ionic liquids have a wider region of ideal polarizability (ΔE) compared to those based on traditional aqueous electrolytes 1-4. The wider ΔE in turn improves the energy and power density values of EDLCs. The specific adsorption of halide ions at single crystal electrodes from aqueous and non-aqueous electrolyte solutions has been demonstrated before 5,6. However, the specific adsorption of ions is a complicated process depending on the electrode potential, chemical composition and concentration of halides etc., and the kinetics of formation/rearrangement of electrical double layer between electrode and ionic liquid (IL) needs an extended examination. The main aim of this work was to characterize the adsorption of iodide ions from ionic liquid media without added electrolytes. Electrochemical impedance spectroscopy and cyclic voltammetry methods have been applied to study the electrochemical characteristics of the interface between electrochemically polished Bi(111) electrode and 1-butyl-3-methylimidazolium iodide (BMImI). All measurements were carried out inside a glovebox using a 3-electrode electrochemical cell: a Bi(111) as a working, Pt net as a counter, and Ag wire coated with AgCl as a reference electrodes. Current density (i) vs. electrode potential (E) dependencies show that the system is stable within a wide range of potentials. ΔE is 1.7V i.e from ─1.4 V to +0.3 V (vs. Ag | AgCl), which is extremely high for the bismuth electrode, known as a catalytically, chemically and electrochemically inactive electrode material. The shape of the complex impedance plane, i.e. Nyquist plots, total impedance vs. log frequency and phase angle vs. log frequency dependences depend on the electrode potential applied. The values of phase angle are high as -85o within a wide range of potentials at medium and low ac frequencies. Also the Nyquist plots show only a slight deviation from the ideal capacitive behavior of the system at f < 1 Hz within wide ΔE applied. The values of series differential capacitance (C s) were calculated from Nyquist dependencies at different fixed ac frequencies (C s = (Z''i2πf)−1; where i = √−1and Z’’ is the imaginary part of impedance). In the studied system C s depends strongly on ac frequency and electrode potential, increasing at lower ac frequencies and at anodic range of potentials. C s values for Bi(111) | BMImI are much higher compared to Bi(111) | 1-ethyl-3-methylimidazolium tetrafluoroborate system. References L. Siinor, J. Poom, C. Siimenson, K. Lust, E. Lust, J. Electroanal. Chem., 719, 133 (2014).L. Siinor, C. Siimenson, K. Lust, E. Lust, Electrochem. Commun. 35, 5 (2013).R. Palm, H. Kurig, K. Tõnurist, A. Jänes, E. Lust, Electrochim. Acta, 85, 139 (2012)., T. Tooming, T. Thomberg, L. Siinor, K. Tõnurist, A. Jänes, E. Lust, J. Electrochem. Soc. 161, A222 (2014).L. Siinor, K. Lust, E. Lust, J. Electroanal. Chem., 601, 39 (2007).M. Väärtnõu, E. Lust, J. Electroanal. Chem., 565, 211 (2004). Acknowledgements Estonian Energy Technology Program project SLOKT10209T, Estonian Centers of Excellence in Science project: High-technology Materials for Sustainable Development TK117, Functional Micro/Mesoporous Nanomaterials for Novel Energy Conversion and Storage Systems IUT 20-13, Functionalization of carbon nanomaterials: synthesis, characterization and application SLOKT12180T.

Textures on the surface of BSA films with different concentrations of sodium halides and water state in solution.

The formation of the textures on the surface of the films from the solutions of bovine serum albumin (BSA) with sodium halides (NaF, NaCl, and NaBr) of various concentrations was studied. The formation of symmetric zigzag textures on the surface of BSA films (Cryst Eng 3:173-194, 2000) in the presence of sodium halides depends on the conformational state of the protein globule. Thermal denaturation of BSA also did not allow to form zigzag textures on the surface of the films.

Electron doping in bottom-up engineered thermoelectric nanomaterials through HCl-mediated ligand displacement.

A simple and effective method to introduce precise amounts of doping in nanomaterials produced from the bottom-up assembly of colloidal nanoparticles (NPs) is described. The procedure takes advantage of a ligand displacement step to incorporate controlled concentrations of halide ions while removing carboxylic acids from the NP surface. Upon consolidation of the NPs into dense pellets, halide ions diffuse within the crystal structure, doping the anion sublattice and achieving n-type electrical doping. Through the characterization of the thermoelectric properties of nanocrystalline PbS, we demonstrate this strategy to be effective to control charge transport properties on thermoelectric nanomaterials assembled from NP building blocks. This approach is subsequently extended to PbTe(x)Se(1-x)@PbS core-shell NPs, where a significant enhancement of the thermoelectric figure of merit is achieved.

The dissolution of palladium as a function of glucose concentration in chloride containing solutions of acidic pH

A strong anodic peak observed in cyclic voltammetry measurements of palladium electrodes when adding glucose to chloride containing (0.1M) slightly acidic (pH 5.3) unbuffered media was studied in detail. The peak was highly sensitive to glucose concentration (5–20g/L). Experiments were conducted by variation of pH (1–13) and chloride concentration (0.5–50g/L) of the medium over a wide range, as well as substituting chloride with bromide. The resulting data suggests dissolution of the electrode as a chloride complex as the root cause for the peak, which is triggered by the addition of glucose to the electrolyte. The organic substances are oxidised thereby removing the protecting oxide layer and enabling the dissolution. This reaction is only observed in a certain window confined by both pH and halide concentration.

Inhibitive and Synergistic Properties of Ethanolic Extract of Moringa oleifera Leaves on the Corrosion of Zinc in HCl Solution

The potentials of ethanolic extract of Moringa oleifera leaves as corrosion inhibitor was investigated by evaluating the corrosion behaviour of Zinc immersed in 0.5M, 1.0M, 1.5M and 2.0M HCl (corrodent) solutions each containing varied concentration of the extract (0.1 g/L, 0.3 g/L and 0.5 g/L) and halides (0.1M, 0.3M and 0.5M each of KCl and KI) for synergism using thermometric method. Maximum temperature attained, reaction time, synergism parameter and adsorption characterizations were utilized to evaluate the corrosion inhibition, synergism and adsorption properties of the extract. The results revealed that the corrosion of Zinc decreases with increase in concentration of ethanol extract and halides which are both inhibitors; also, it increases with increase in HCl (corrodent) concentration. The addition of KI and KCl to the extract, improve the values of inhibition efficiency of the extract in the order KI > KCl. In all cases, KI exhibits least effect on the corrosion of Zinc in comparison with KCl. Results obtained from adsorption studies indicated

Cl-mediated electrochemical oxidation for treating an effluent using platinum and diamond anodes

In this work, the role of chloride with respect to the oxygen evolution reaction by using BDD and Pt/Ti anodes was investigated to understand the performance of both anodes for the electrochemical treatment of a real sample of wastewater, with lower organic load, generated at Federal University of Rio Grande do Norte. Bulk experiments were performed under real discharged effluent conditions (pH and conductivity) in order to verify the applicability of direct and mediated electrochemical oxidation by applying 2.5 and 5.0mAcm−2. Results clearly showed that, a partial elimination of chemical oxygen demand (COD) was achieved, depending on applied current density. Using Pt/Ti, by applying 2.5 and 5.0mAcm−2, COD removal efficiencies of 25.2% and 30.49% were obtained. Under the same conditions, a minor COD removal was achieved by using BDD electrode. However, the removal efficiencies were improved when Cl-mediated oxidation approach was employed, obtaining 63.7% and 60% for Pt/Ti by applying 2.5 and 5.0mAcm−2, respectively; while for BDD electrode, COD removals were about 15% and 47%, under the same conditions. These figures are in agreement with the polarization curves obtained, where it was possible to confirm that the concentration of halide in solution increases the importance of Cl2/oxy-chloro radicals system depending on the electrocatalytic material and this behavior plays an important role in relation with the oxygen evolution reaction, influencing on the efficiency of electrochemical approach adopted.

Exhaustive thin-layer cyclic voltammetry for absolute multianalyte halide detection.

Water analysis is one of the greatest challenges in the field of environmental analysis. In particular, seawater analysis is often difficult because a large amount of NaCl may mask the determination of other ions, i.e., nutrients, halides, and carbonate species. We demonstrate here the use of thin-layer samples controlled by cyclic voltammetry to analyze water samples for chloride, bromide, and iodide. The fabrication of a microfluidic electrochemical cell based on a Ag/AgX wire (working electrode) inserted into a tubular Nafion membrane is described, which confines the sample solution layer to less than 15 μm. By increasing the applied potential, halide ions present in the thin-layer sample (X(-)) are electrodeposited on the working electrode as AgX, while their respective counterions are transported across the perm-selective membrane to an outer solution. Thin-layer cyclic voltammetry allows us to obtain separated peaks in mixed samples of these three halides, finding a linear relationship between the halide concentration and the corresponding peak area from about 10(-5) to 0.1 M for bromide and iodide and from 10(-4) to 0.6 M for chloride. This technique was successfully applied for the halide analysis in tap, mineral, and river water as well as seawater. The proposed methodology is absolute and potentially calibration-free, as evidenced by an observed 2.5% RSD cell to cell reproducibility and independence from the operating temperature.

Re-evaluating the reactive uptake of HOBr in the troposphere with implications for the marine boundary layer and volcanic plumes

Abstract. The reactive uptake of HOBr onto halogen-rich aerosols promotes conversion of Br−(aq) into gaseous reactive bromine (incl. BrO) with impacts on tropospheric oxidants and mercury deposition. However, experimental data quantifying HOBr reactive uptake on tropospheric aerosols is limited, and reported values vary in magnitude. This study introduces a new evaluation of HOBr reactive uptake coefficients in the context of the general acid-assisted mechanism. We emphasise that the termolecular kinetic approach assumed in numerical model studies of tropospheric reactive bromine chemistry to date is strictly only valid for a specific pH range and, according to the general acid-assisted mechanism for HOBr, the reaction kinetics becomes bimolecular and independent of pH at high acidity. This study reconciles for the first time the different reactive uptake coefficients reported from laboratory experiments. The re-evaluation confirms HOBr reactive uptake is rapid on moderately acidified sea-salt aerosol (and slow on alkaline aerosol), but predicts very low reactive uptake coefficients on highly acidified submicron particles. This is due to acid-saturated kinetics combined with low halide concentrations induced by both acid-displacement reactions and the dilution effects of H2SO4(aq). A mechanism is thereby proposed for reported Br enhancement (relative to Na) in H2SO4-rich submicron particles in the marine environment. Further, the fact that HOBr reactive uptake on H2SO4-acidified supra-micron particles is driven by HOBr+Br− (rather than HOBr+Cl−) indicates self-limitation via decreasing γHOBr once aerosol Br- is converted into reactive bromine. First predictions of HOBr reactive uptake on sulfate particles in halogen-rich volcanic plumes are also presented. High (accommodation limited) HOBr+Br- uptake coefficient in concentrated (&gt; 1 μmol mol−1 SO2) plume environments supports potential for rapid BrO formation in plumes throughout the troposphere. However, reduced HOBr reactive uptake may reduce the rate of BrO cycling in dilute plumes in the lower troposphere. In summary, our re-evaluation of HOBr kinetics provides a new framework for the interpretation of experimental data and suggests that the reactive uptake of HOBr on H2SO4-acidified particles is substantially overestimated in current numerical models of BrO chemistry in the troposphere.

Enhanced coagulation with powdered activated carbon or MIEX® secondary treatment: A comparison of disinfection by-product formation and precursor removal

The removal of both organic and inorganic disinfection by-product (DBP) precursors prior to disinfection is important in mitigating DBP formation, with halide removal being particularly important in salinity-impacted water sources. A matrix of waters of variable alkalinity, halide concentration and dissolved organic carbon (DOC) concentration were treated with enhanced coagulation (EC) followed by anion exchange (MIEX® resin) or powdered activated carbon (PAC) and the subsequent disinfection by-product formation potentials (DBP-FPs) assessed and compared to DBP-FPs for untreated samples. Halide and DOC removal were also monitored for both treatment processes. Bromide and iodide adsorption by MIEX® treatment ranged from 0 to 53% and 4–78%, respectively. As expected, EC and PAC treatments did not remove halides. DOC removal by EC/PAC was 70 ± 10%, while EC/MIEX® enabled a DOC removal of 66 ± 12%. Despite the halide removals achieved by MIEX®, increases in brominated disinfection by-product (Br-DBP) formation were observed relative to untreated samples, when favourable Br:DOC ratios were created by the treatment. However, the increases in formation were less than what was observed for the EC/PAC treated waters, which caused large increases in Br-DBP formation when high Br-DBP-forming water quality conditions occurred. The formation potential of fully chlorinated DBPs decreased after treatment in all cases.

Application of the quasi-random lattice model to rare-earth halide solutions for the computation of their osmotic and mean activity coefficients

This work dealt with the computation of the mean activity coefficients of rare-earth halide aqueous solutions at 25°C, by means of the Quasi Random Lattice (QRL) model. The osmotic coefficients were then calculated consistently, through the integration of the Gibbs-Duhem equation. Using of QRL was mainly motivated by its dependence on one parameter, given in the form of an electrolyte-dependent concentration, which was also the highest concentration at which the model could be applied. For all the electrolyte solutions here considered, this parameter was experimentally known and ranged from 1.5 to 2.2 mol/kg, at 25 °C. Accordingly, rare-earth halide concentrations from strong dilution up to 2 mol/kg about could be considered without need for best-fit treatment in order to compute their osmotic and mean activity coefficients. The experimental knowledge about the parameter was an advantageous feature of QRL compared to existing literature models. Following a trend already observed with low charge electrolytes, a satisfactory agreement was obtained with the experimental values for all the investigated rare-earth chlorides and bromides. For the sake of compactness, in this work the considered rare-earth halides were all belonging to the P63/m space group in their crystalline (anhydrous) form.

Explaining unexpected data via competitive equilibria and processes in radical reactions with reversible deactivation.

In the game rock-paper-scissors, each of the three options, or pathways, has an equal chance of dominating, that is, rock beats scissors, scissors beats paper, and paper beats rock. In the classical form of the game, there is no one dominant pathway to follow, but they are all balanced in likelihood. However, in chemical reactions with several competing reagents, the question must be asked, are all competing reactions and pathways accessible? A related question is, if there are two, or more reversible processes that compete for the same reagent, will both processes equilibrate simultaneously, or will one process dominate system? Can these competing processes shed light on otherwise puzzling data? Several unexpected and counterintuitive experiments have been reported in radical reactions with reversible deactivation. These unexpected observations can be illustrated by the near absence of the products of conventional bimolecular radical coupling in the radical transformation of methylcobaltamine to acetylcobaltamine. Another counterintuitive observation is a difference in the copolymer composition in some copolymerizations proceeding via reversible-deactivation radical polymerization (RDRP) vs conventional radical polymerization (RP), for example, nitroxide mediated polymerization of styrene and methyl methacrylate. A similarly puzzling phenomenon is the reduction in the branching fraction in poly(acrylates) polymerized by RDRP vs conventional RP. In the three previously mentioned cases, the radicals formed in reversible deactivation radical reactions are identical to those formed in the corresponding conventional radical process; therefore an explanation for the discrepancy in the outcomes of the reaction is needed. Other unexpected observations include the presence of initial periods of slower monomer consumption in RDRP reactions initiated by a conventional radical initiator with certain chain transfer agents, while changing the nature of chain transfer agent can lead to an acceleration of the reaction during the initial period. Similarly, in Cu mediated atom transfer radical polymerization (ATRP) with initiators for continuous radical regeneration (ICAR) initiated by a conventional radical initiator, the rate of polymerization should not depend on either the alkyl halide concentration or the Cu concentration. However, experiments show that the rate could be 10 times faster with alkyl halide than without alkyl halide. Finally, in aqueous media, the presence of active alkyl halides can appear to stop the disproportionation of Cu(I) complexes. These unusual data point to a more complex mechanism than originally envisioned, and in fact all these counterintuitive observations can be explained by the concept of competing equilibria and processes. In these cases, the presence of two or more reactions competing for the same reagent typically causes one pathway to dominate, while the rate of the other pathways are diminished. Alternatively, the competing pathways and processes can cause one or more reversible or pseudoreversible reactions to be imbalanced and lead to products distinct from the case where rates of forward and reverse reactions are balanced. In this Account, the concept of competitive processes and equilibria is developed and used to explain each of the unusual observations highlighted above.

Electrochemical Characterization of the PG | EMImBF4 + x% EMImI Interface

The need for alternative high energy and power density energy sources has led scientists to study extensively the electrochemical energy conversion/storage devices such as electrochemical double layer capacitors (EDLC), batteries, fuel cells, etc. The values of power and energy densities of EDLC depend strongly on the properties of the electrode material and electrolyte used. EDLCs based on non-aqueous electrolytes or room temperature ionic liquids have a wider region of ideal polarizability (ΔE) compared to those based on traditional aqueous electrolytes 1-4. The wider ΔE in turn improves the energy and power density values of EDLCs. The specific adsorption of halide ions at single crystal electrodes from aqueous and non-aqueous electrolyte solutions has been demonstrated before 5,6. However, the specific adsorption of ions is a complicated process (depending on the electrode potential, chemical composition and concentration of halides etc.) and the kinetics of formation/rearrangement of electrical double layer between electrode and ionic liquid (IL) needs an extended examination. The main aim of this work was to characterize the adsorption of iodide ions from the mixture of two ionic liquids based on the same electrochemically stable 1-ethyl-3-methylimidazolium cation. Electrochemical impedance spectroscopy and cyclic voltammetry methods have been applied to study the electrochemical characteristics of the interface between pyrolytic graphite (PG) and mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium iodide (1-10 wt%). All measurements were carried out in a 3-electrode electrochemical cell using a PG as a working, Pt net as a counter, and Ag wire coated with AgCl as a reference electrodes. Current density (i) vs. electrode potential (E) dependencies (Fig. 1) show that two peaks in CV are caused by the addition of x wt% of EMImI into EMImBF4 (for PG | EMImBF4 interface there is no peaks within the potential region from ─1.5 V to +1.5 V (vs. Ag | AgCl)). Reduction and oxidation processes are more intensive in more concentrated solutions. A strong dependence of current density on the potential scanning rate (υ) for PG | EMImBF4+EMImI interface was observed in the region of peaks. Also the capacitance values calculated from CV data (Ccv= i / υ) show the strong dependence on υindicating a very slow adsorption process occurs. The shape of the complex impedance plane, i.e. Nyquist plots, total impedance and phase angle vs. frequency dependences depend strongly on the electrode potential and on the concentration of the I-ions in the solution. The values of series differential capacitance (C s) were calculated from Nyquist dependencies at different fixed ac frequencies (C s = (Z''i2πf)−1; where i = √−1and Z’’ is the imaginary part of impedance). C s depends strongly on ac frequency and electrode potential, increasing at lower ac frequencies and at anodic range of potentials. C s values depend also on the added amount of I-(1-10%) to the solution, increasing from 1 to 5wt% and diminish in more concentrated solutions. References L. Siinor, J. Poom, C. Siimenson, K. Lust, E. Lust, J. Electroanal. Chem., 719, 133 (2014).L. Siinor, C. Siimenson, K. Lust, E. Lust, Electrochem. Commun. 35, 5 (2013).R. Palm, H. Kurig, K. Tõnurist, A. Jänes, E. Lust, Electrochim. Acta, 85, 139 (2012).R. Palm, H. Kurig, K. Tõnurist, A. Jänes, E. Lust, Electrochem. Commun. 22, 203 (2012).L. Siinor, K. Lust, E. Lust, J. Electroanal. Chem., 601, 39 (2007).M. Väärtnõu, E. Lust, J. Electroanal. Chem., 565, 211 (2004). Acknowledgements Estonian Energy Technology Program project SLOKT10209T, Estonian Centers of Excellence in Science project: High-technology Materials for Sustainable Development TK117, Functional Micro/Mesoporous Nanomaterials for Novel Energy Conversion and Storage Systems IUT 20-13, Functionalization of carbon nanomaterials: synthesis, characterization and application SLOKT12180T.

Effect of aqueous extract of leaves of Morinda tinctoria on corrosion inhibition of aluminium surface in HCl medium

The effect of Morinda tinctoria (MT) leaves extract on the corrosion inhibition of Al in acid medium was studied. The inhibition studies were carried out on Al in 0.5 mol/L HCl with the extract of leaves of MT using mass loss and electrochemical techniques. Parameters, such as concentration of the inhibitor, concentration of the acid, temperature and concentration of halide ions, were varied and optimized. Increase of the temperature and concentration of acid can decrease the performance of the inhibitor. Thermodynamic parameters show that the physisorption of the inhibitor molecules on Al surface obeys Langmuir isotherm.

Surface and zeta-potentials of silver halide single crystals: pH-dependence in comparison to particle systems

We have carried out surface and zeta-potential measurements on AgCl and AgBr single crystals. As for particle systems we find that, surprisingly and previously unnoted, the zeta-potential exhibits pH-dependence, while the surface potential does not. A possible interpretation of these observations is the involvement of water ions in the interfacial equilibria and in particular, stronger affinity of the hydroxide ion compared to the proton. The pH-dependence of the zeta-potential can be suppressed at sufficiently high silver concentrations, which agrees with previous measurements in particle systems where no pH-dependence was found at high halide ion concentrations. The results suggest a subtle interplay between the surface potential determining the halide and silver ion concentrations, and the water ions. Whenever the charge due to the halide and silver ions is sufficiently high, the influence of the proton/hydroxide ion on the zeta-potential vanishes. This might be related to the water structuring at the relevant interfaces which should be strongly affected by the surface potential. Another interesting observation is accentuation of the assumed water ion effect on the zeta-potential at the flat single crystal surfaces compared to the corresponding silver halide colloids. Previous generic MD simulations have indeed predicted that hydroxide ion adsorption is accentuated on flat/rigid surfaces. A thermodynamic model for AgI single crystals was developed to describe the combined effects of iodide, silver and water ions, based on two independently previously published models for AgI (that only consider constituent and background electrolyte ions) and inert surfaces (that only consider water and background electrolyte ions). The combined model correctly predicts all the experimentally observed trends.

Adenovirus inactivation by in situ photocatalytically and photoelectrocatalytically generated halogen viricides.

This study investigates and compares the virucidal performances of photocatalytic (PC) and photoelectrocatalytic (PEC) treatments in the presence and absence of halides, such as Br- and Cl-, under comparable experimental conditions. The results confirm that the PC virucidal efficiency can be enhanced in the presence of low halide concentrations (e.g., X=Br- or Cl-) and further enhanced by applying potential bias onto the photoanode in a PEC system. The PEC treatment in the presence of 1.0mM Br (PEC-Br) shows the highest virucidal efficiency, enabling complete inactivation of a ∼1000 TCID50 replication-deficient recombinant adenovirus (RDRADS) population within 31.7s. The superior virucidal performances of PEC-X treatments can be attributed to the increased production of active oxygen species and additional viricides resulting from the PEC halide oxidation, as well as prolonged lifetime of photoholes (h+ ) for direct inactivation. The findings of this work confirm that new forms of active species generated in situ via a PC or PEC process are effective for viruses.

Reaction media dominated product selectivity in the isomerization of glucose by chromium trichloride: From aqueous to non-aqueous systems

While chromium trichloride hydrate (CrCl3·6H2O) effectively catalyzed the isomerization of glucose into fructose in aqueous solution, a general product selectivity behavior was observed independent of reaction variables such as reaction time, temperature, catalyst loading, halide ion, and initial glucose concentration. By studying the mixed solution of dimethylsulfoxide (DMSO) and water at varied DMSO/H2O ratios, it was found that deviation from the general water-phase fructose yield curve, with concomitant 5-hydroxymethylfurfral (HMF) formation, occurred when the fructose concentration in available water became sufficiently high in DMSO rich solvent mix. Therefore, tuning the solvent system was the most effective approach to change the product distribution from CrCl3·6H2O catalyzed glucose conversion. The apparent activation energy of glucose conversion in the studied system was estimated to be 58.6kJmol−1. Special attention was also given to gain some mechanistic insights by control experiments with simple model compounds and additives, 13C NMR and UV–vis spectroscopic analyses.