Initial Persulfate Concentration Research Articles

Oxidation of Orange G by persulfate activated by Fe(II), Fe(III) and zero valent iron (ZVI)

Persulfate (PS) was employed in the oxidation of Orange G (OG), an azo dye commonly found in textile wastewaters. Activation of PS was conducted with iron to generate sulfate free radicals (SO4-) with high redox potential capable to oxidize most of the organics in water. Identification of oxidation intermediates was carried out by analyzing at different times organic by-products generated from treatment of a concentrate dye solution (11.6mM) with 153mM of PS and 20mM of Fe(II) at 20°C. Intermediate reaction products (mainly phenol (PH) and benzoquinone (BQ), and in less extent aniline, phenolic compounds and naphthalene type compounds with quinone groups) were identified by GC/MS and HPLC, and an oxidation pathway was proposed for the oxidation of OG with iron activated PS. The effect of iron valence (0, II and III) in the oxidation of an aqueous solution of OG (containing 0.1mM) was studied in a 0.5L batch reactor at 20°C. Initial activator and PS concentrations employed were both 1mM. Complete pollutant removal was achieved within the first 30min when iron II or III were employed as activators. Quinone intermediates generated during pollutant oxidation may act as electron shuttles, allowing the reduction of Fe(III) into Fe(II) in the redox cycling of iron. Therefore, activation of PS by Fe(III) allowed complete OG removal. When zero valent iron (ZVI) was employed (particle diameter size 0.74mm) the limiting step in SO4- generation was the surface reaction between ZVI and the oxidant yielding a lower oxidation rate of the dye. An increase in the oxidant dosage (0.2mM OG, 2mM Fe(III) and 6mM PS) allowed complete pollutant and ecotoxicity removal, as well as mineralization close to 75%.

Kinetic oxidation of antipyrine in heat-activated persulfate

The kinetic oxidation of antipyrine by activated persulfate oxidation was investigated. The reaction kinetic rates under different temperature (T, 40–70°C), initial persulfate concentration ([PS]0), and initial antipyrine concentration ([AP]0) were examined in batch experiments. The results show that higher temperature, higher persulfate concentration, and lower initial antipyrine favored antipyrine degradation. A deep investigation into the reaction order obtained a more accurate kinetics rate equation (−d[AP]/dt = 0.34 [PS]0 [AP]) with the limits of the experimental conditions applied here. The removal of antipyrine in 120 min was 54.3% at pH 4.5, and antipyrine degradation at different pH followed the order: pH 4.5 ##xgt; pH 11.0 ##xgt; pH 7.0 ##xgt; pH 9.5. The persulfate disappearance fits pseudo-first-order kinetics well, the calculated disappearance rate of persulfate (kobs-PS) was 2.33±0.23 × 10−4 min−1 at 60°C. Although 71.4% of initial antipyrine was degraded at 60°C, only 12.5% of initial antipyrine was mineralized. At last, norantipyrine and 5-pyrazolidinone-3-methyl-1-phenyl were identified to be the degradation products of antipyrine in heat activated persulfate system for the first time, and the degradation pathway of antipyrine was also tentatively proposed.

A study of the applicability of various activated persulfate processes for the treatment of 2,4-dichlorophenoxyacetic acid

This paper reports an investigation of different persulfate (PS) activations, including PS at 20 °C (PS), thermally activated PS at 70 °C (T-PS), ferrous-ion activated PS at 20 °C [Fe(II)-PS)], hydrogen peroxide activated PS at 20 °C, and sodium hydroxide activated PS at 20 °C, for degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous phase. Several findings were made in this study including the followings: the 2,4-D degradation rates in T-PS and Fe(II)-PS systems were higher than other systems. However, complete degradation of 2,4-D and associated derivatives can be reached in all oxidation systems, with various reaction times. When considering the results of PS consumption during the 48 h reaction time to reach complete 2,4-D degradation, the T-PS system consumed all of the PS while only 10 % of the PS was consumed in the Fe(II)-PS system. The evaluation of optimum PS and ferrous ion doses indicated that under a fixed initial PS concentration, increasing Fe2+ concentration generally increased the amount of initial rapid degradation of 2,4-D and dissolved organic carbon. However, the effectiveness of the Fe(II)-PS system may be inhibited by the presence of excess iron. When a fixed level of Fe2+ was employed, various PS concentrations resulted in approximately equal 2,4-D degradation. The Fe(II)-PS system was found to be sensitive to the initial Fe2+ concentration, and the presence of soil revealed minor influence on the 2,4-D degradation by the Fe(II)-PS system. These findings indicate that the iron-activated PS process may be an effective method for remediating 2,4-D contamination.

Kinetic Study of the Degradation of Crystal Violet by K2S2O8. Comparison with Malachite Green

The degradation of crystal violet (CV) and malachite green (MG) by potassium persulfate, was investigated by spectrophotometric methods. The behavior of degradation of crystal violet by persulfate was found to be similar to that of malachite green with only one important difference concerning the order with respect to the dye: the degradation is pseudo second order with respect to CV, but first order with respect to MG. The order with respect to persulfate is one in both cases. Degradation of CV by persulfate was effective at pH range of 2-8 and was found to increase with an increase in the initial concentrations of persulfate, temperature, and the presence of Ag + . The factors that were found to decrease the degradation rate of CV include: the initial concentration of CV, and the presence of halide salts and of the surfactant SDS. The rate of degradation remained the same after addition of Co(II), Ni(II) and Cu(II) salts.

Decolorization of anthraquinone dye Reactive Blue 19 by the combination of persulfate and zero-valent iron

Decolorization of anthraquinone dye Reactive Blue 19 (RB19) with sulfate radicals generated in situ from persulfate and zero-valent iron (ZVI) was investigated. The effects of initial solution pH, initial concentration of RB19, ZVI and persulfate, reaction temperature and common dissolved anions were studied. 100% color removal efficiency and 54% TOC removal efficiency were achieved in 45 min with an initial RB19 concentration of 0.1 mM under typical conditions (pH 7.0, 0.8 g L(-1) ZVI, 10 mM persulfate and 30 C). The decolorization efficiency of RB19 increased with higher iron dosage, higher initial persulfate concentration, and higher reaction temperature. It is also an acid driven process. The decolorization process followed pseudo-first order kinetics and the activation energy was 98.1 kJ mol-1. RB19 decolorization was inhibited by common dissolved anions such as CL-, NO3-, H2PO4- and HCO3- since they reacted with sulfate radicals that retarded the oxidation process. The experiment demonstrated that the combination of persulfate and ZVI was a promising technology for the decolorization of dye wastewater.

Feasibility study of ultraviolet activated persulfate oxidation of phenol

Using ultraviolet photolytic persulfate activation to produce two sulfate radicals ( SO 4 - ) exhibits a potential for destroying organic contaminants in wastewater treatment applications. This study investigated both the feasibility of using a UV/SPS (sodium persulfate) process to treat phenol in aqueous phase and the effect of pH on degradation efficiency and TOC removal. The results revealed that a high initial persulfate concentration (i.e., 84 mM) and a lower initial phenol concentration (i.e., 0.5 mM) resulted in rapid and complete phenol degradation within 20 min. For all three pHs evaluated (i.e., 3, 7 and 11), complete phenol degradation was also achieved after 30 min of treatment by UV/SPS oxidation processes (i.e., under an SPS/phenol molar ratio of 84/0.5) with pseudo-first-order rate constants ( k obs, phenol) of 0.14–0.16 min −1 (average half-life ( t 1/2) = 4.5 min). UV–Vis spectrum scanning of the aqueous solution during treatment identified the development of brown color in the wavelength range of 400–460 nm. The colored intermediate compounds that formed were suspiciously similar to those observed during Fenton treatment. However, a more aggressive oxidation at pH 11 showed a rapid and more complete removal of TOC in aqueous phase. Therefore, it is recommended that UV photolytic persulfate activation under basic pH be a preferred condition for treatment of phenol.

Treatment of Trichloroethylene by Adsorption and Persulfate Oxidation in Batch Studies

For remediation of trichloroethylene (TCE) contaminated groundwater, activated carbon (AC) has been used to adsorb and reduce the TCE concentration and to manage contaminant migration. Additionally, AC may also act as an activator of the electron-transfer mediator in activating persulfate anion (S2O82−) to generate sulfate radical (SO4−·) for contaminant destruction. The objective of the present research was to examine the combined use of AC and persulfate to treat TCE. The degradation of persulfate in the presence of AC follows a first-order kinetic behavior, and the faster persulfate degradation is observed when elevated AC dosage is used. Higher initial persulfate concentration results in a decrease of the persulfate degradation rate. Upon persulfate oxidation, the AC surface properties are altered including: an increase in acidity of surface concentration, a decrease in pHzpc, and a slight decrease in the surface area. The results of a study of adsorption kinetics and isotherms suggest that the adsorp...

Thermally Activated Persulfate Oxidation of Trichloroethylene: Experimental Investigation of Reaction Orders

The kinetics of dissolved trichloroethylene (TCE) oxidation by thermally activated sodium persulfate (Na2S2O8) was investigated in a phosphate-buffered solution at pH 7 and an ionic strength of 0.1 at a temperature of 40 °C. Thermal activation results in the production of a highly reactive sulfate free radical (SO4•-). The method of half-lives was used to determine the reaction order with respect to TCE. This was accomplished by conducting a series of kinetic experiments and keeping in great excess (and therefore essentially constant) the sodium persulfate concentration while varying the TCE initial concentration. Resulting plots of normalized TCE concentration (C/Co) vs time were analyzed by polynomial regression analysis. Half-lives were calculated based on the resulting polynomial equations. To determine the reaction order with respect to persulfate, experiments were designed to examine a range of initial persulfate concentrations while maintaining the same initial TCE concentration. These results were also analyzed using polynomial regression analysis. The results of these studies indicate that the degradation rate of TCE by sodium persulfate could be described by the kinetic rate equation −d[TCE]/dt = (5.59 × 10-4 mM0.2 min-1)[TCE]0[S2O82-]0.8 within the limits of the experimental conditions utilized here (i.e., 40 °C, ionic strength 0.1, pH 7, TCE 0.14−0.52 mM, and S2O82- 13.5−43.7 mM). This equation indicates that the thermally activated persulfate oxidation of TCE appears to be pseudo zero order with respect to TCE (and therefore independent of the initial TCE concentration) and fractional order with respect to persulfate. This result should serve as a starting point for modeling of the TCE/persulfate system.

Model Studies of Nitroxide‐Mediated Styrene Miniemulsion Polymerization – Opportunities for Process Improvement

AbstractModeling studies were performed to investigate how persulfate‐initiated nitroxide‐mediated styrene miniemulsion polymerizations are influenced by changes to the polymerization recipe. By manipulating the initial concentrations of potassium persulfate and nitroxide, and the aqueous phase volume, trends in the predicted polymerization time, number average molecular weight, polydispersity and degree of polymer livingness were identified that indicate operating conditions for improved process performance. Specifically, our model predicts the existence of experimental conditions that simultaneously minimize polymer polydispersity and maximize the livingness of the polymer. The mechanisms responsible for the predicted trends were identified from the predicted molecular weight distributions of the living and dead polymer chains.Predicted number MWDs at 20% monomer conversion for styrene NMMP systems employing various levels of [KPS]aq,0. Dormant KPS‐initiated polymer radicals.imagePredicted number MWDs at 20% monomer conversion for styrene NMMP systems employing various levels of [KPS]aq,0. Dormant KPS‐initiated polymer radicals.

Mechanism of Organic Oxidation in Aqueous Solution. II. Effect of Initial Persulfate Concentration on the Rate of Oxidation of Isopropyl Alcohol1

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of Organic Oxidation in Aqueous Solution. II. Effect of Initial Persulfate Concentration on the Rate of Oxidation of Isopropyl Alcohol1Edmund R. Malinowski and Leonard S. LevittCite this: J. Am. Chem. Soc. 1958, 80, 20, 5334–5337Publication Date (Print):October 1, 1958Publication History Published online1 May 2002Published inissue 1 October 1958https://doi.org/10.1021/ja01553a003RIGHTS & PERMISSIONSArticle Views136Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (402 KB) Get e-Alerts Get e-Alerts