Persulphate Ion Research Articles

Kinetics of oxidation of ethylenediammine-N,N,N’,N’-tetraacetatocobaltate(II)complex by silver-activated persulphate ion in aqueous acidic medium

The kinetics of oxidation of Ethylenediammine-N,N,N’,N’-tetraacetatocobaltate(II) complex ([Co(II)EDTA2-]) by silver-activated persulphate ion in a ueous nitric acid medium was studied at I = 0.5 mol dm-3(NaNO3), [H+] = 1 × 10-2 mol dm-3, [Ag+] = 1 × 10-2 mol dm-3, T = 299 ± 1 K and λmax = 520 nm. Stoichiometric study showed 2:1 (Reductant: Oxidant) mole ratio. The reaction exhibited first order with respect to the [Co(II)EDTA2-] and [ S2O82-] and the rate constant, (5.90 × 10-2 dm3mol-1s-1) was independent of the acid concentration, but varied linearly with catalyst concentration, [Ag+]. The overall rate law is represented as: d[Co(II)EDTA2-]/dt = 5.90 x 10-2 [Ag+][Co(II)EDTA2-][s2082-] The reaction displayed zero salt effect suggesting an activated complex composed of either a neutralcharged, neutral-neutral reactant species or ion-pair. The reaction was catalysed by addition of formate ion, HCOO- and the Michaelis-Menten’s type plot gave zero intercept indicating the absence of intermediate complex. Also, the activation enthalpy ( △H# = +39.27 kJ mol-1) and entropy ( △H# = -136.73 J K-1 mol-1) were determined. The entropy of activation shows a more ordered activated complex relative to the reactants species. Evaluating the experimental data, an outer-sphere mechanistic pathway via ion pair activated complex is proposed for the reaction.Keywords: Kinetics, Oxidation, Aminocarboxylactocobaltate(II), Persulphate ion

Wastewater treatment of biodiesel production using persulphate ion as an oxidant

Introduction: The production of biodiesel produces a highly polluting effluent, because presents high values of Chemical Oxygen Demand (COD), oils and fats, among other contaminants. Sodium persulphate is a powerful oxidant (Eo = 2.1V). In addition to the direct oxidation that is favored in alkaline media, it can be induced by photolytic processes, catalytic and / or catalytic photos forming sulphate radicals (Eo = 2.6 V) thus providing reaction mechanisms with free radicals like hydroxyl radicals. Methods: In this work the effect of the potassium monopersulphate compound (2KHSO5.KHSO4K2SO4), (Oxone) on the removal of COD in residual water from the biodiesel purification step was tested. Results: The tests, direct oxidation at alkaline pH and catalytic oxidation with cobalt ions, Co(II), showed that the former, for Oxone concentrations of 1.00x10-2 M and 4.00x10-3 M, were not effective because no decomposition occurred, for reaction times over three hours, thus not occurring removal of COD. In the catalytic assays combinations were tested, varying between 5.00x10-3 M and 7.50x10-2 M for the oxidant and 0.10 μM and 1.00 μM for the catalyst. The complete decomposition of the oxidant was always verified between 15 min. and 2 h. The tests with the lowest concentration of cobalt showed COD removal rates around 20% and the highest one reached 60%. Conclusions: The most favorable assay achieves significant COD removals, but not enough for the effluent to be discharged in the hydric medium according the portuguese legislation.

Kinetics of Oxidation of Ethylenediammine-N,N,N',N'-tetraacetatocobaltate (II) complex by Silver-activated Persulphate ion in Aqueous Acidic Medium

Kinetics of Oxidation of Ethylenediammine-N,N,N',N'-tetraacetatocobaltate (II) complex by Silver-activated Persulphate ion in Aqueous Acidic Medium

Synthesis of novel probe 2-chloro-6-methoxy-3-phenyl hydrazone quinoline and its application to detection of persulphate in aqueous ethanol solution by fluorescence turn on

A highly sensitive and selective fluorimetric detection method has been developed for persulphate anion using fluorescence turn on of 2-chloro-6-methoxy-3-phenyl hydrazone quinoline (Cl-MPHQ) in aqueous ethanol solution. Cl-MPHQ is a weakly fluorescent compound synthesized via a one-step reaction of 2-chloro-6-methoxyquinoline-3-carboxyaldehyde (Cl-MQCA) and phenyl hydrazine. The treatment of Cl-MPHQ with persulphate ion in aqueous ethanol solution (1:1 V/V) generates fluorescent Cl-MQCA, through C=N bond cleavage. The fluorescence intensity increased linearly with the concentration of persulphate ion (0–100 µmol L−1). The detection limit of the method is 1 µmol L−1determined from the standard deviation of the blank signal (3σ). The relative standard deviation of the method is 3% for 20 µmol L−1 of persulphate ion. The proposed method is simple, sensitive and useful for selective detection of persulphate ion in an aqueous ethanol solution.

The Kinetics of Single-Electron Transfer from a Pyrrole Molecule to a Persulphate Ion

An investigation was made of the kinetics of single-electron transfer from a pyrrole molecule to a peroxy disulphate ion in the initial period of oxidative polymerisation. It was shown that the reaction is second order, and the rate constants and activation energy of single-electron transfer were determined.

Chain extended vinyl aniline modified cyclohexanone formaldehyde resin

PurposeThe purpose of this paper was as follows. The in situ chemical oxidation (ICO) of vinyl aniline modified cyclohexanone formaldehyde resin (CFVAnR) in the presence of potassium persulphate salt (K2S2O8) was accomplished in dimethyl sulphoxide (DMSO) solutions at 35°C and 70°C. The chemical composition and structure of the oxidized CFVAnR were characterised by nuclear magnetic resonance (1H‐NMR) spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy, DSC, TGA and SEM.Design/methodology/approachThe reactive vinyl and amine groups of the cyclohexanone formaldehyde resin were reacted in the presence of potassium persulphate. CFVAn resin was dissolved in DMSO inside a round bottom flask immersed in a water bath thermostated at reaction temperature of 35°C and 70°C, respectively. Solution of K2S2O8 was prepared in DMSO and this was added into the resin solution.FindingsIt was shown that the vinyl groups in the resin were reacted easily with persulphate salt to obtain chain extended CFVAnR (CECFVAnR). The oxidised 4‐vinyl aniline modified cyclohexanone‐formaldehyde resin has solublity in organic solvents.Research limitations/implicationsThe reaction mixture must be stirred continuously. Temperature should be controlled to prevent the thermal polymerisation of vinyl group and higher branching of amino groups. The persulphate ion (S2O82−) has a standard oxidation potential, but when activated by heat (40‐60°C). Furthermore, sulphate radical can react with water or hydroxide to produce hydroxyl radical (−OH). When persulphate is used for in situ chemical oxidation (ISCO) application at relatively low temperatures (e.g. <20°C), the oxidation reactions are usually less aggressive due to a slow generation rate of SO4−.Practical implicationsThis study provides technical information for the synthesis of chain extended resins. The modified resins contain vinyl groups. The chemical radical system has been used to polymerise these vinyl groups and resins with much higher molecular weight might be produced. The resins may also promote the adhesive strength of a coating and corrosion inhibition to metal surfaces of a coating.Social implicationsThis resin will be used for the preparation of AB‐ and ABA‐type block copolymers. These block copolymers may exhibit different properties due to incorporation of ketonic resins into the block copolymer structure.Originality/valueChain extended CFVAnR (CECFVAnR) was synthesised by one step reduction‐oxidation reaction, at 35°C (CECFVAnR1) and 70°C (CECFVAnR2) in the presence of potassium persulphate salt. These soluble resins may overcome difficulties in the applications of polymers and open new application areas. Therefore, the chain extended vinyl aniline modified resin may find a number of new application areas as well as existing UV curable resin and polymer applications.

Restricted Geometry Conditions Promoted by AlOOH Nanoparticles: Variable Strength and Character of AlOOH-Cluster/Charged Ligand Interactions As a Consequence of Changes in the Solvent

AlOOH nanoparticles have been used to study the strength and character of the binding of the persulphate ion (S2O82−), at pH = 5.4, to them. The strength of the binding has been studied using a kinetic approach which consists of the study of the oxidation kinetics of a metal cation complex ([Ru(NH3)5pz]2+ (pz = pyrazine)) by S2O82− at different NaCl concentrations. When the ionic strength increases, the strength of the binding decreases, as a consequence of the partial neutralization of the charge on the AlOOH surface which, at pH = 5.4, is positively charged. The increase of the ionic strength also produces a change in the character of the binding, which changes from anticooperative to noncooperative when the ionic strength increases. The nonelectrostatic and electrostatic components of the free energy of binding are determined. The nonelectrostatic component of the free energy of binding is almost zero. On the other hand, the values of the differences of electrostatic potential at the AlOOH/solutions interface have been obtained from the electrostatic component.

TiO 2-assisted degradation of acid orange 7 textile dye under solar light

Photocatalytic degradation of acid orange 7 (AO7) in aqueous systems was successfully achieved by the combination of TiO 2 with potassium persulphate under solar light using a photochemical reactor with recirculation. Degradation of AO7 involves color removal and mineralization. The employment of TiO 2 removed ∼85% of color from the 0.2 mM AO7 aqueous solution under solar light; while, ∼66% of color was abated using the persulphate ion as oxidant in the absence of TiO 2 under similar conditions in 2 h. However, over 90% of color removal was achieved by combining TiO 2 and the persulphate ion for the same solution under similar conditions. Color removal was faster at pH 3. Mineralization of AO7 was followed by measuring chemical oxygen demand (COD). Negligible COD abatement of the textile dye was observed in the absence of persulphate ions (S 2O 8 2−) while over 70% of COD abatement was observed for the initial dye concentrations of 0.2–0.7 mM employing a mix of TiO 2–S 2O 8 2− under solar light.

Sonolytic degradation of methyl tert-butyl ether: the role of coupled fenton process and persulphate ion

The sonolytic degradation of methyl tert-butyl ether (MTBE) has been investigated at ultrasonic frequency of 20 kHz. The observed pseudo-first-order rate constant decreased from 1.25×10 −4 to 5.32×10 −5 s −1as the concentration of MTBE increased from 2.84×10 −2 to 2.84×10 −1 mM. The rate of degradation of MTBE increased with the increase of the power density of ultrasonicator and also with the rise in reactor system temperature. In the presence of oxidising agent, potassium persulphate, the sonolytic rate of degradation of MTBE was accelerated substantially. Tert-butyl formate (TBF) and acetone were found to be the major intermediates of the degradation of MTBE. It is found that the ultrasound/Fe 2+/H 2O 2 method is promising process for the degradation of MTBE. More than 95% degradation of MTBE (2.84×10 −2 mM) along with its intermediate products has been achieved during the coupled ultrasound/Fe 2+/H 2O 2 method. Hence, the coupled ultrasound/Fe 2+/H 2O 2 may be a viable method for the degradation MTBE within a short period of time than the ultrasound irradiation process only. A kinetic model, based on the initial rates of degradation of MTBE and TBF, provides a good agreement with the experimental results.

KINETICS OF PHOTOCATALYTIC DEGRADATION OF REACTIVE YELLOW 17 DYE IN AQUEOUS SOLUTION USING UV IRRADIATION

In this paper photoinduced degradation of reactive yellow 17 (RY 17) dye has been studied employing TiO2 in the form of slurry in a batch reactor. UV lamps were used as the source for irradiation. The disappearance of the dye in the solution follows approximately pseudo-first order kinetics. The apparent rate constant decreases with increase in initial concentration of the dye. The addition of oxygen, hydrogen peroxide and persulphate ion influences the degradation rate of the dye. The formation of CO2, SO4 2−, NO3− and NH4+ions have been identified in the mineralisation process. The decolourisation and mineralisation were followed by UV-Visible spectrophotometer and high performance liquid chromatography respectively. The results reveal that photocatalytic degradation may be a useful technique in the removal of reactive dyes in wastewater from textile industries.

Voltage-induced modifications of porous silicon luminescence

The remarkable voltage-tunable electroluminescence (VTEL) observed on porous silicon—electrolyte junctions is investigated in relation to material morphology and electrolysis parameters. The electroluminescence (EL) is obtained upon cathodic polarization of n-type porous silicon in contact with aqueous solutions containing the persulphate ion. The observed long-lived EL shows a reversible spectral shift as large as 300 nm for an external bias variation of about 0.6 V. The study of the EL behaviour as a function of the external voltage and the persulphate ion concentration shows that while the amplitude of the EL is proportional to the intensity of the exchanged current, the spectral position is only determined by the applied voltage. A qualitative model, taking into account the voltage dependence of the charge injection probability into the size-distributed silicon crystallites, gives a good description of the observed VTEL behaviour. In a similar manner, cathodic polarization induces a dramatic change in the porous silicon photoluminescence. It leads to a reversible, highly contrasted and energy-selective quenching of the photoluminescence (QPL) for a polarization variation of only about 500 mV. A spectral blue shift, along with a significant narrowing of the PL line accompanies the observed strong QPL. This results from selective quenching starting at the low luminescence energy and reaching progressively the high luminescence energy as the cathodic polarization is increased. Just as for VTEL, this selective character of the QPL can be explained by a voltage-induced enhancement of charge injection into the size-distributed silicon nanocrystallites.

Voltage-controlled spectral shift of porous silicon electroluminescence.

In this paper, it is reported that the electroluminescence (EL) of porous silicon shows a reversible spectral shift as large as 270 nm for an external bias variation of 0.6 V. This electroluminescence is obtained upon cathodic polarization of lightly doped n-type porous silicon in contact with aqueous persulphate solutions. The study of the EL behavior as a function of the external voltage and the persulphate ion concentration proves that while the amplitude of the EL is proportional to the intensity of the exchanged current, the spectral position is only determined by the applied voltage

Polypyridylruthenium(II) persulphate as photoinitiator in the grafting of vinyl monomers onto cellulose acetate

The use of tris(2,2′-bipyridyl)ruthenium(II) and tris(1,10-phenanthroline)ruthenium(II) to photoinitiate the grafting of vinyl monomers onto cellulose triacetate in the presence of persulphate ion is described. IR spectra and gravimetric studies of the product, after separation of homopolymer, confirm that grafting occurs when acrylamide, acrylic acid, acrylonitrile, methyl acrylate, methacrylamide and glycidyl methacrylate are used as monomers. With maleic acid, there is no evidence of grafting. Photolysis can be carried out using mercury or tungsten lamps, sunlight or an argon ion laser. For acrylamide, acrylic acid, acrylonitrile and methyl acrylate, the effects of monomer and persulphate concentration and irradiation time on the yield of grafting were studied. Luminescence quenching studies suggest that reaction involves the formation of SO 4 − by interaction between persulphate and excited ruthenium(II) complexes. These then form radicals with the cellulose derivative, which react with vinyl monomers to yield, eventually, graft copolymer. With poly(methyl acrylate) copolymer, the graft, after hydrolysis of cellulose triacetate, has a molecular weight of 40 000. No ruthenium(III) species is present in the final product, showing that the photoinitiation is catalytic. The graft copolymer with poly(glycidyl methacrylate) can be used to immobilize the enzyme trypsin.

Electrocatalysis of S 2O 82− ion reduction : The effect of underpotential deposition on the kinetics of the cathodic process on platinum

The effect of underpotential-deposited (upd) monolayers of heavy metals (i.e. Pb, Tl and Bi) on the rate of persulphate ion electroreduction on Pt has been studied in aqueous acid, neutral and alkaline media. It was found that upd adlayers improve significantly the electrocatalytic activity of platinum for S 2O 8 2- ion reduction. The enhancement in the electrocatalytic activity is characterized by a shift of the Tafel region for S 2O 8 2− ion reduction towards more positive potentials and by the attainment of diffusion-controlled limiting current densities within the upd range of the metals used. The catalytic effect has been interpreted in terms of preventing the covering of the Pt surface with chemisorbed species resulting from the dissociative chemisorption of S 2O 8 2− ions, thus leading to faster electron exchange for the charge-transfer step involved in the reaction mechanism.

Spectrophotometric determination of nickel(II), iron(II), boric acid and chloride in plating baths by flow injection analysis

A simple, non-separation method for the determination of nickel(II) and iron(II) in an electroplating bath by flow injection analysis is described. Methods are also described for the determination of boric acid and chloride. Nickel(II)(0.17–0.24 M) is determined by direct spectrophotometry of the nickel(II) ion at 675 nm in the presence of 2.7–5.4 mM iron(II). Iron(II) is oxidised by persulphate ion to iron(III), which then forms a complex with thiocyanate ion. The absorbance of the intensely red [Fe(SCN)2]+ species is measured at 505 nm. One hundred measurements h–1 are possible with this system. In a second manifold boric acid is measured indirectly by the association reaction of 8-amino-1-hydroxynaphthalene-3,6-disulphonic acid with salicylaldehyde to form azomethine H in the presence of boric acid. A linear calibration graph is obtained in the range 0.05–0.8 M boric acid versus absorbance at 420 nm with a two-fold on-line dilution. The chloride concentration (0–1.7 M) is measured in the third and fourth manifolds. Chloride reacts with mercury(II) thiocyanate to form mercury(II) chloride, releasing thiocyanate ion which then complexes any iron(III) ion present in the reagen stream; the absorbance of the [Fe(SCN)2]+ complex is measured at the absorbance maximum (480 nm). The analysis utilises a single-line manifold after a 500-fold manual dilution or after an on-line 380-fold effective dilution factor using a cascade dilution manifold to bring the concentration range of the analysis into the linear calibration region. Interferences by plating-bath components on each system are discussed.

Quantum chemical calculation of S 2O 2−8, SO 42− and SO 4− [rad] by INDO/ 2 method

Electron density distribution on atomic bonds SO and OO in persulphate ion for two different -OO- bond lengths −1.5 and 2.0Å using INDO/ 2 method with parameters proposed by Pople on the BESM-6 computer have been calculated. The results of the calculations show that the electron density is lowest on -OO- bond, which is in accordance with experimental data. The calculations based on the assumption that d -oo- » ∞ lead to the conclusion that the homolytic cleavage of -OO- bond in S 2O 2− 8 ion is more probable.

Persulphate ion as a reagent for the detection of aromatic compounds containing the NH 2 group using thin-layer chromatography

Persulphate ion as a reagent for the detection of aromatic compounds containing the NH 2 group using thin-layer chromatography

The photochemical decomposition of sulphuric acid catalysed by [HPt(PEt3)3

Far u.v irradiation of Pt(PEt3)3 in dilute sulphuric acid produces hydrogen and probably per-sulphate ion also.

Mechanisms for aromatic photocyanation: naphthalene and biphenyl

Photocyanation of naphthalene and biphenyl has been studied in the systems ArH–KCN–aqueous CH3CN and ArH–NaCN–CH3OH. The reaction is first order in CN– and in ground state ArH as well as in excited ArH. The proposed mechanism involves the formation of a singlet excimer, which dissociates into radical ions before the attack of cyanide ion. Photocyanations in the presence of oxidants such as p-dicyanobenzene and persulphate ion proceed by oxidation of the singlet excited hydrocarbon to form a radical cation directly.

Potassium ruthenate: a catalytic oxidant for organic substrates

Potassium ruthenate (K2[RuO4]) can be used catalytically in the presence of persulphate ion, for oxidation of organic substrates under mild conditions.