Oxidation Of Potassium Iodide Research Articles

Studies on the Sonochemical assisted Oxidation Reaction of Potassium Iodide for Iodine Release using Ultrasound

Ultrasound (US) application and sonochemical reactions in various environmental processes are gaining importance. In this regard, liberation of iodine obtained through oxidation of potassium iodide (KI) using US has been studied in the present work. This method finds wide application of oxidation process in various applications such as unit process reactions, synthetic chemistry as well as waste remediation. Process parameters such as time and ultrasound power have been investigated. Liberation of iodine from the reaction system has been analyzed using UV-Visible spectrophotometric method through iodometry. Maximum liberation of iodine was obtained using ultrasound (25 W, 20 kHz) for 30 minutes treatment with 10 ml of 16.6% KI solution. The study finds potential use in sonochemical based oxidation reactions and environmental processes.

ОКИСЛЕНИЕ ИОДИД-ИОНОВ ПЕРСУЛЬФАТОМ АММОНИЯ В ПРИСУТСТВИИ ИОНОВ ПЕРЕХОДНЫХ МЕТАЛЛОВ

The catalytic activity of four metal ions of the fourth period of the table by D.I. Mendeleev in the oxidation of potassium iodide with ammonium persulfate. The greatest increase in the reaction rate is observed in the presence of copper sulfate, the least in the presence of cobalt and nickel salts

Spectrophotometric determination of hydrogen peroxide in water with peroxidase-catalyzed oxidation of potassium iodide and its applications to hydroxylamine-involved Fenton and Fenton-like systems

A spectrophotometric method for the rapid measurement of hydrogen peroxide (H2O2) in aqueous solutions was developed in this study. This method is based on a reaction catalyzed by peroxidase (POD) in which potassium iodide (KI) is oxidized to generate the stable yellow-colored I3− within 15 s. The absorbance of the generated I3− at both 350 nm and 400 nm had good linear relationships with H2O2 concentration in the range of 0–70 μM (R2 > 0.999) with sensitivities of 2.34 × 104 M−1 cm−1 and 5.30 × 103 M−1 cm−1 respectively. Meanwhile, through calculation, the detection limits of the proposed POD-KI method at 350 nm and 400 nm were 0.09 μM and 0.33 μM, respectively. Even when the concentration of H2O2 was up to 350 μM, the absorbance of the generated I3− at 350 nm did not decrease observably. The generated I3− was found to be stable enough in ultrapure water, underground water, reservoir water and samples containing the strong reducing agent hydroxylamine. Moreover, the proposed POD-KI method was successfully used to analyze trace H2O2 in rainwater, and to monitor the change of H2O2 concentration in the Fenton, hydroxylamine/Fenton and hydroxylamine/Cu(II)/H2O2 systems. Overall, the POD-KI method could be adopted as a candidate method to determine H2O2 in Fenton and Fenton-like systems, and especially in those involving hydroxylamine.

Preparation and Characterization of Antioxidative and UV-Protective Larch Bark Tannin/PVA Composite Membranes.

In order to prepare functional materials for antioxidant and ultraviolet (UV)-protective green food packaging, condensed tannin, previously extracted from larch bark, was mixed with polyvinyl alcohol (PVA), and then the mixture was used to cast composite membranes. An antioxidative assay using 1,1-diphenyl-2-picrylhydrazyl (DPPH)—a free radical scavenger—and starch–potassium iodide oxidation–discoloration analyses showed that the composite membranes have good antioxidative activities. The low UV transmission and protective effect of the composite films on vitamin E indicated the UV protection ability of the composite membranes. Both larch bark tannin and PVA are rich in hydroxyl groups; scanning electron microscopy analysis demonstrated their compatibility. Also, the mechanical and crystallization properties of the composite membranes did not significantly decrease with the addition of larch bark tannin.

Cobalt-catalyzed stereoselective iodosulfonylation and diiodination of alkynes via oxidation of potassium iodide in air

Cobalt-catalyzed iodosulfonylation of alkynes can be achieved using sodium sulfinates in the presence of KI. This procedure produces numerous stereoselective (E)-β-iodoalkenyl sulfones with good yields and suppresses the formation of diiodoalkenes. Furthermore, when this reaction is performed in the absence of sodium sulfinates, the expected (E)-diiodoalkenes are obtained.

Sonochemical effect induced by hydrodynamic cavitation: Comparison of venturi/orifice flow geometries

This study presents comparative assessment of four cavitation devices (three venturis and an orifice) in terms of cavitational yield. A fourfold approach was adopted for assessment, viz. CFD simulations of cavitating flow, simulations of individual cavitation bubble dynamics, high speed photographs of cavitating flow and model reaction of potassium iodide oxidation. Influence of design parameters of cavitation devices on nature of cavitation produced in the flow was studied. Number density of cavitation bubbles in the flow and interactions among bubbles had critical influence on cavitation yield. Orifice gave the highest cavitational yield per unit energy dissipation in flow (despite lower working inlet pressure) due to low density of cavitation bubbles in flow. On contrary, occurrence of large cavitation bubble clouds in venturi flow had adverse effect on cavitational yield due to high interactions among cavitation bubbles resulting in interbubble coalescence and recombination of oxidizing radicals generated from cavitation bubbles. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4705–4716, 2017

Dependence of cavitation, chemical effect, and mechanical effect thresholds on ultrasonic frequency

Cavitation, chemical effect, and mechanical effect thresholds were investigated in wide frequency ranges from 22 to 4880kHz. Each threshold was measured in terms of sound pressure at fundamental frequency. Broadband noise emitted from acoustic cavitation bubbles was detected by a hydrophone to determine the cavitation threshold. Potassium iodide oxidation caused by acoustic cavitation was used to quantify the chemical effect threshold. The ultrasonic erosion of aluminum foil was conducted to estimate the mechanical effect threshold. The cavitation, chemical effect, and mechanical effect thresholds increased with increasing frequency. The chemical effect threshold was close to the cavitation threshold for all frequencies. At low frequency below 98kHz, the mechanical effect threshold was nearly equal to the cavitation threshold. However, the mechanical effect threshold was greatly higher than the cavitation threshold at high frequency. In addition, the thresholds of the second harmonic and the first ultraharmonic signals were measured to detect bubble occurrence. The threshold of the second harmonic approximated to the cavitation threshold below 1000kHz. On the other hand, the threshold of the first ultraharmonic was higher than the cavitation threshold below 98kHz and near to the cavitation threshold at high frequency.

Towards the development of cavitation technology for upgrading bitumen: Viscosity change and chemical cavitation yield measurements

Among the different methods used for reducing viscosity of bitumen, acoustic cavitation during sonication is well recognised. Several chemical methods were used to detect the production of reactive species such as hydroxyl radicals and hydrogen peroxide during acoustic cavitation processes. However, quantification of cavitation yield in sonochemical systems is generally limited to low frequencies and has not been applied to bitumen processing. An empirical determination of the cavitation yield in mid- to high-frequency range (378, 574, 850, 992, and 1173 kHz) was carried out by measuring the amount of iodine liberated from the oxidation of potassium iodide (KI). Further, cavitation yield and the effects of different sonic operating conditions such as power input (16.67%–83.33%) and solute concentration on cavitation yield were carried out in KI solution and sodium carboxymethyl cellulose–water mixture to obtain benchmark changes in rheology and chemistry using these two model fluids. The findings were then applied to bitumen upgrading through sonication. Through this study, it was found that the chemical cavitation yield peaked with a sonication frequency of 574 kHz. It was also found that cavitation yield and viscosity change were correlated directly in bitumen and a 38% lower bitumen viscosity could be obtained by acoustic cavitation.

Three-Dimensional Simulation of Ultrasound-Induced Microalgal Cell Disruption.

The three-dimensional distribution (x, y, and z) of ultrasound-induced microalgal cell disruption in a sonochemical reactor was predicted by solving the Helmholtz equation using a three-dimensional acoustic module in the COMSOL Multiphysics software. The simulated local ultrasound pressure at any given location (x, y, and z) was found to correlate with cell disruption of a freshwater alga, Scenedesmus dimorphus, represented by the change of algal cell particle/debris concentration, chlorophyll-a fluorescence density (CAFD), and Nile red stained lipid fluorescence density (LFD), which was also validated by the model reaction of potassium iodide oxidation (the Weissler reaction). Furthermore, the effect of ultrasound power intensity and processing duration on algal cell disruption was examined to address the limitation of the model.

Energy characterisation of ultrasonic systems for industrial processes

Obtaining accurate power characteristics of ultrasonic treatment systems is an important step towards their industrial scalability. Calorimetric measurements are most commonly used for quantifying the dissipated ultrasonic power. However, accuracy of these measurements is affected by various heat losses, especially when working at high power densities. In this work, electrical power measurements were conducted at all locations in the piezoelectric ultrasonic system equipped with ½″ and ¾″ probes. A set of heat transfer calculations were developed to estimate the convection heat losses from the reaction solution. Chemical dosimeters represented by the oxidation of potassium iodide, Fricke solution and 4-nitrophenol were used to chemically correlate the effect of various electrical amplitudes and treatment regimes. This allowed estimation of sonochemical-efficiency (SE) and energy conversion (XUS) of the ultrasonic system. Results of this study showed overall conversion efficiencies of 60–70%. This correlated well with the chemical dosimeter yield curves of both organic and inorganic aqueous solutions. All dosimeters showed bubble shielding and coalescence effects at higher ultrasonic power levels, less pronounced for the ½″ probe case. SE and XUS values in the range of 10−10mol/J and 10−3J/J respectively confirmed that conversion of ultrasonic power to chemical yield declined with amplitude.

Intensification of cavitational activity in the sonochemical reactors using gaseous additives

Sonochemical reactors have a significant potential for intensification of physical as well as chemical processes due to the effects of hotspots, intense turbulence and generation of free radicals. However, it is observed that commercial scale applications of these reactors are scarce possibly due to lack of uniform intensified activity at large scale and reliable design/operating strategies. The present work deals with investigations related to the intensification of cavitational activity based on the use of different gaseous additives with the results being equally applicable for all gas–liquid applications of sonochemical reactors. Model reactions of oxidation of potassium iodide and salicylic acid degradation have been used for quantification of cavitational activity. Initially, effect of different operating parameters such as temperature, power, duty cycle and initial concentration has been investigated. The different gaseous additives used in the work include air, oxygen, nitrogen and carbon dioxide. Effect of air flow rate on the cavitational activity has also been examined. Theoretical modeling studies based on the use of COMSOL have also been performed to explain the alteration of pressure field distributions due to the presence of gaseous additives. Overall it can be said that presence of gases enhances the cavitational activity and the effect is dependent on the nature of the gas and its physicochemical properties as well as the operating conditions in terms of the flow rate of the introduced gas. The work presents new design related information helpful for effective scale up and operation of sonochemical reactors.

A comparison of the degree of intensification due to the use of additives in ultrasonic horn and ultrasonic bath

The inherent cavitational activity in the ultrasonic horn and ultrasonic bath can be further enhanced using different additives which can also aid in decreasing the processing cost of the operation. The present work deals with evaluation of different additives for enhancing the cavitational effects using a model reaction of potassium iodide oxidation. Two reactors with varying capacity have been used with an objective of understanding the dependency of scale of operation on the efficacy of additives. The effects of various additives such as air, solid particles like titanium dioxide, salts like sodium chloride and radical promoters such as hydrogen peroxide and carbon tetrachloride have been investigated. It has been observed that depending on the mechanism of intensification, the beneficial effects are strongly dependent on the reactor operating conditions, i.e. intensity and frequency of irradiations, which control the inherent cavitational activity. It is desirable to select an additive which can give additional reaction mechanisms in the system to aid the desired application under question. It has been conclusively established that for effective scale up it would be essential to provide an optimum power dissipation levels through a wider area of irradiation for the transducers.

A Novel Heterojunction BiOBr/Bismuth Oxyhydrate Photocatalyst with Highly Enhanced Visible Light Photocatalytic Properties

In this study, a facile and effective method to modify the photocatalytic performance of a bismuth oxybromide (BiOBr) semiconductor through the fabrication of a heterojunction with a hydrated bismuth oxide (BHO) is reported. The new yBiOBr-(1 – y)BHO heterojunction, synthesized by a simple hydrothermal method, exhibits a high photocatalytic activity under visible light irradiation for the photodegradation of typical organic pollutants in water, such as Rhodamine B (RhB) and acetophenone (AP). Both the individual BiOBr and BHO components show very low photocatalytic efficiency. Furthermore, the unique photocatalytic performance of the new hybrid material was demonstrated through the uphill photocatalytic reaction that involves the oxidation of potassium iodide (KI) to triiodide. The remarkable photocatalytic activity of the coupled system is directly related to the effectual charge carrier separation due to the formation of the heterostructure. 0.9BiOBr-0.1BHO shows a higher photocatalytic activity as comp...

Hydrodynamic cavitation in micro channels with channel sizes of 100 and 750 micrometers

Decreasing the constriction size and residence time in hydrodynamic cavitation is predicted to give increased hot spot temperatures at bubble collapse and increased radical formation rate. Cavitation in a 100 × 100 μm2 rectangular micro channel and in a circular 750 μm diameter milli channel has been investigated with computational fluid dynamics software and with imaging and radical production experiments. No radical production has been measured in the micro channel. This is probably because there is no spherically symmetrical collapse of the gas pockets in the channel which yield high hot spot temperatures. The potassium iodide oxidation yield in the presence of chlorohydrocarbons in the milli channel of up to 60 nM min−1 is comparable to values reported on hydrodynamic cavitation in literature, but lower than values for ultrasonic cavitation. These small constrictions can create high apparent cavitation collapse frequencies

Comparison of cavitational activity in different configurations of sonochemical reactors using model reaction supported with theoretical simulations

The present work deals with evaluation of different configurations of sonochemical reactors using a model reaction with justification on the basis of cavitational activity predictions of theoretical simulations. In addition, intensification of the cavitational effects using additives has been investigated and its dependency on the inherent cavitational activity in the reactor has been established. The model reaction used for experimental investigations is the potassium iodide oxidation, also known as the Weissler reaction whereas the theoretical prediction of cavitational activity has been achieved using the numerical simulations of the sound wave equation using Comsol Multi physics software. The effects of various additives for enhancing the cavitational activity such as solid particles like cupric oxide, salts like sodium nitrite and radical promoters such as ferrous sulphate have also been investigated. It has been observed that the configuration with higher transducer areas gives better distribution of the cavitational activity and also gives enhanced effects as quantified using the cavitational yield measurements. Also it has been conclusively established that depending on the mechanism of intensification, the beneficial effects obtained using different additives are strongly dependent on the inherent cavitational activity which in turn depends on the type of reactor and the operating conditions.

Enhancement of Sonochemical Reaction by Dual-Pulse Ultrasound

In order to apply sonochemistry in wastewater treatment, enhancement of sonochemical reaction is necessary. Oxidation of potassium iodide and the degradation of acid orange 7 in aqueous solution using ultrasound irradiation were performed at 490 kHz. Power-modulated pulsed waves were employed and the enhancement of reaction amount was observed compared with using continuous wave. The enhancement ratio for irradiation to rigid wall was larger than that for irradiation to free surface. Moreover, the best modulated pulsed on time was experimentally determined and the effect of the superposition of pulsed waves (dual-pulse) was studied. Enhancement was also observed and calculated separately when using dual-pulse ultrasound. The enhancement upon the use of the dual-transducer was ascribed to the enlargement of sonochemical reaction field. The enhancement upon the incorporating pulsed waves was ascribed to both the reduction of reaction threshold effect and the residual acoustical pressure at the pulsed off time.

Influence of Cavitation on Ethanol Enrichment in an Ultrasonic Atomization System

Ethanol was separated from aqueous solutions through ultrasonic atomization. Ethanol enrichment was evaluated by determining ethanol concentration in condensates collected from atomized mist and vapor. The amount of collected mist and vapor accorded with the amount of liquid left from the atomization column. In the limited range of ethanol feed concentration below 30 mol%, the ethanol concentration in the condensates was affected by ultrasonic parameters such as frequency and input power. Ethanol enrichment was enhanced at higher frequencies and lower input power. The effect of ultrasonic parameters on ethanol enrichment was interpreted from the viewpoint of cavitation. Potassium iodide oxidation was conducted to examine the occurrence of cavitation, and the number of violently collapsing bubbles. The use of higher frequency and lower input power, which corresponded to enhance ethanol enrichment, resulted in a decrease in KI reactivity. This trend suggests that violently collapsing bubbles enhanced fragmentation of the bulk liquid where no separation mechanism works. Assuming that the surface excess of ethanol plays a significant role in the separation, possible routes of ethanol transfer from liquid to mist or vapor are suggested.

Intensification of cavitational activity in sonochemical reactors using different additives: Efficacy assessment using a model reaction

Sonochemical reactors offer excellent promise for the intensification of different chemical processing applications. The current work deals with intensification of cavitational activity using different additives with an objective of decreasing the processing cost as well as enhancing the applicability of sonochemical reactors for different applications. Potassium iodide oxidation has been used as a model reaction. Experiments have been carried out in a laboratory scale ultrasonic horn reactor. The effects of different additives such as air, solid particles (cupric oxide and titanium dioxide), salts (sodium chloride and sodium nitrite) and radical promoters (hydrogen peroxide, ferrous sulphate, iron metal, carbon tetrachloride and t-butanol) on the degradation of potassium iodide have been investigated. Combination of additives has also been investigated for examining the possible synergistic effects in comparison to the use of individual additions. It has been observed that based on the type of additive, optimum concentration needs to be selected and it may not be desirable always to use different additives in combination. It is desirable to select an additive which can give additional reaction mechanism in the system to aid the desired application under question.

Effect of resonance frequency, power input, and saturation gas type on the oxidation efficiency of an ultrasound horn

The sonochemical oxidation efficiency ( η ox ) of a commercial titanium alloy ultrasound horn has been measured using potassium iodide as a dosimeter at its main resonance frequency (20 kHz) and two higher resonance frequencies (41 and 62 kHz). Narrow power and frequency ranges have been chosen to minimise secondary effects such as changing bubble stability, and time available for radical diffusion from the bubble to the liquid. The oxidation efficiency, η ox , is proportional to the frequency and to the power transmitted to the liquid (275 mL) in the applied power range (1–6 W) under argon. Luminol radical visualisation measurements show that the radical generation rate increases and a redistribution of radical producing zones is achieved at increasing frequency. Argon, helium, air, nitrogen, oxygen, and carbon dioxide have been used as saturation gases in potassium iodide oxidation experiments. The highest η ox has been observed at 5 W under air at 62 kHz. The presence of carbon dioxide in air gives enhanced nucleation at 41 and 62 kHz and has a strong influence on η ox . This is supported by the luminol images, the measured dependence of η ox on input power, and bubble images recorded under carbon dioxide. The results give insight into the interplay between saturation gas and frequency, nucleation, and their effect on η ox .

Comparison of characterization methods in high frequency sonochemical reactors of differing configurations

The aim of this study was to compare different characterization methods in order to evaluate the sonochemical efficiency of a cavitational reactor. The selected characterization methods were calorimetry and dosimetry based on potassium iodide oxidation or nitrite and nitrate ion formation. The effects of experimental parameters on physical and chemical effects of ultrasound were quantified with two transducers at a frequency of 366 kHz. The studied factors comprised temperature (16–28 °C), acoustic power (6–38 W), power density (4–61 W L −1) and reactor configuration ( D reactor 1 = 65 mm, D reactor 2 = 102 mm). Spectrophotometry was compared to ionic chromatography as a method to quantify nitrite and nitrate ions. Spectrometry was shown to be as representative as ionic chromatography. The reaction system based on the formation of both nitrite and nitrate ions was demonstrated to be as reliable as a potassium iodide dosimeter . The representativity of calorimetry was limited since part of acoustic energy was assumed to be used in the chemical reactions observed by dosimetry. Similar sonochemical efficiencies resulted from an increase of sonified surface ( D reactor 1 = 65 mm vs. D reactor 2 = 102 mm) coupled to a 2-time decrease in power density at a constant emitting surface. The effect of emitting-to-sonified surface area ratio on the acoustic field was apparently limited by the height of the liquid.