Search

Aromatic sulfonated compounds and naphthalene derivatives are major chemical compounds used in the industry. Electron beam irradiation of aqueous solutions of 2-naphthalenesulfonate (90 µM) was investigated under various experimental conditions. The results obtained demonstrate that the 2-NS concentration decreased dramatically on increasing the absorbed dose in the range 0–1000 Gy. The effectiveness of the radiolytic system was demonstrably enhanced by the addition of oxidants (S 2 O 8 2− or H 2 O 2 ). 2-NS removal was higher with S 2 O 8 2− than with H 2 O 2 . For the EB, EB/H 2 O 2 , and EB/S 2 O 8 2− systems, the absorbed doses for 90% elimination of 2-NS (D 90 ) were 700, 480, and 274 Gy, respectively. 2-NS is poorly mineralized by EB but more than 35% mineralization was reached for 15 kGy when oxidants (820 µM S 2 O 8 2− or 935 µM H 2 O 2 ) were added. In all systems, the mineralization yield was markedly higher when air (i.e. dissolved oxygen increase) was introduced between successive doses. For 50% 2-NS removal, seven sulfonated transformation products were identified using LC/MS analyses. For the highest absorbed doses the sulfonate group in 2-NS was converted to sulfate ions in the radiolytic systems. [ABSTRACT FROM AUTHOR]

Abstract: The electron beam irradiation of aqueous solutions of citric acid was studied. The results showed the effectiveness of the degradation of the carboxylic acid by the radiation process. The impact of pH was examined. It was demonstrated that the increase of pH induces a drop of the degradation due to the scavenging of radicals by the inorganic carbon. Moreover the interest of persulfate () addition that induces the formation of sulfate radicals () by the reaction of persulfate with the hydrated electrons was studied. The addition of persulfate leads to a great enhancement of the degradation of the carboxylic acid and also a large increase of the mineralization of the solution. Effectively, it was shown that the particular reactivity of the sulfate radical causes an enhancement of the mineralization yield. [Copyright &y& Elsevier]

Abstract: The degradation of acetic acid in aqueous solution by ionizing radiation was studied. The radiolysis of acetic acid solution induces the almost complete degradation and mineralization of this compound. The high yield of acetic acid mineralization is explained by the degradation of oxalic acid by solvated electron. The degradation of acetic acid depends on the pH of the solution. The best degradation is observed at pH 4.5 due to the higher rate constant of reaction of acetate with hydroxyl radicals and the competitive reactions of inorganic carbon which occur at higher pH. The influence of persulfate ion (S2O8 2−) addition that forms the sulfate radical (SO4 −) during irradiation in solution was examined. The persulfate addition induces an almost constant degradation of acetic acid whatever the initial pH of the solution. The decrease of pH during the persulfate radiolysis partly explains the high degradation observed. But the additional radicals formed by the persulfate introduction also improve the degradation. [Copyright &y& Elsevier]

Abstract: These days, the use of persulfate in advanced oxidation processes (AOPs) has gained more attention as an emerging clean and efficient technology to degrade the organic pollutants. The objective of this study was to investigate the effect of the addition of persulfate on the oxidation of benzotriazole (BT) and humic acids (HAs) by irradiation. The degradation of BT (3.7μM) was followed under the influence of persulfate addition (200–500μM) in combination with a fixed radiation dose (15Gy) in the absence and presence of HA (5 and 20mg/L) in deionized water. The main results obtained in this study on the degradation of BT in the presence of HA showed a different effect of S2O8 2− addition during irradiation, depending on whether HA are oxidized or not-oxidized. (1) An inhibitory effect of S2O8 2− was observed in the presence of non-oxidized HA. (2) The removal of BT was generally more important during irradiation in the presence of S2O8 2− when HA is pre-oxidized. This could be explained by the different structures of humic acids. These differences of structures of HA were identified by physico-chemical parameters such as the absorbance in the UV (254nm), the fluorescence and the SUVA measurement. [Copyright &y& Elsevier]

Abstract: The radiolysis of persulfate (S2O8 2−) aqueous solution was studied for the enhancement of electron beam process applied to water treatment. It was shown that the persulfate ion reacts with aqueous electron and produces additional radical species in aqueous solution. The oxidative radical species formed (sulfate radical SO4 − ry strong oxidant able to react with various recalcitrant pollutants. A model of the evolution of persulfate concentration in solution was performed. It was shown that the presence of persulfate induces a decrease of pH and also an increase of dissolved oxygen concentration in solution during irradiation. Moreover the interest of persulfate addition for the improvement of an organic compound degradation by radiolysis was shown. [Copyright &y& Elsevier]

Abstract: Nowadays the removal of organic micropollutants is one of the major challenges of water and wastewater treatment plants. The objective of this study was to investigate the influence of persulfate addition on micropollutants degradation by ionizing radiation. In this system, the radicals SO4 −/OHresent simultaneously due to persulfate reaction with solvated electrons. Ibuprofen (IB), progesterone (Pg) and benzotriazole (BT) have been selected for this study. The degradation of micropollutants was followed at various radiation doses and under the influence of persulfate (S2O8 2−) addition at a fixed dose (30Gy), in deionized and tap water. In deionized water the addition of 500μM persulfate improved the degradation of BT, IB and Pg by 17%, 36% and 24% respectively and the removal of micropollutants was increased when the concentration of persulfate ions increased. No influence of the presence of persulfate ions was observed in tap water. Contrary to tap water experiments, the persulfate (500μM) increases the elimination of BT slightly in the presence of bicarbonate ions. In the case of IB and Pg the influence of persulfate addition is significant even in the presence of bicarbonate ions which indicate that the bicarbonate ions do not completely inhibit the influence of persulfate addition in tap water. Even if the bicarbonate ions have an inhibitory effect on the irradiation system, it was suggested that the inhibition could be explained by the presence of nitrate ions, which would prevent the formation of sulfate radicals. [Copyright &y& Elsevier]

This work aims at envisaging the use of a solid catalyst in the catalytic ozonation process to avoid the separation step needed after the treatment for catalyst recovery when powdered material is involved. This work devoted to the removal of succinic acid (SA), a low molecular weight refractory organic acid whose heterogeneous catalytic ozonation was previously studied using powder form catalysts. Heterogeneous catalytic ozonation of succinic acid was carried out in a reactor fitted with a recirculation loop. This study investigated if the location of the solid catalyst, i.e. inside the reactor in the zone of ozone transfer or in a cartridge placed on the recirculation loop, had an influence on the amount of SA removed or on the elimination rate expression. No influence of the catalyst location was detected. The rates of SA removal by catalytic ozonation were found to depend on both the catalyst concentration and the initial SA concentration for weak SA initial concentrations, but only on the catalyst concentration for greater initial SA concentrations. The pattern of SA concentration from modelization closely matched the experimental results. This implementation of the catalytic ozonation process with solid catalyst is of interest for the application at industrial scale. The 1.8 ratio between the rates of SA and DOC removal showed that mineralization to CO 2 did not occur simultaneously with SA removal. [ABSTRACT FROM AUTHOR]

Abstract: The removal of phenol (Co=100μM) during electron beam irradiation was studied in pure water and in the presence of HCO3 − and Br− ions. It was found that the introduction of S2O8 2− ions (1mM), by generating SO4 − increases the radiation yield of phenol removal. 90% removal of phenol was obtained with radiation doses 600 and 1200Gy with and without S2O8 2− ions respectively. This system induced smaller oxygen consumption with smaller concentration of catechol and hydroquinone found in the solution. HCO3 − and Br− have an inhibiting effect in the presence as in the absence of S2O8 2−. In most cases, the introduction of S2O8 2− ions in water radiolysis system can advantageously increase the yield of organic compounds removal by oxidation. [ABSTRACT FROM AUTHOR]

In wastewater treatment, advanced oxidation processes are largely accepted as efficient technologies. Unfortunately, in general, these approaches present a high operating cost due to an open-loop implementation, i.e. the inlet reagent is introduced in excess in order to respect discharge standards. Therefore a mixture between automatic control techniques and chemical engineering expertise should significantly improve and expand their industrial applications via closed-loop implementations. More precisely, the present paper deals with a catalytic ozonation reactor where the main objective is to reduce the oxygen consumption by minimizing the ozone overproduction. For this end, a H ∞ control strategy is used in order to obtain a significant abatement of the pollutant, and by the way illustrates the gain one can expect when applying such techniques to this kind of process. [ABSTRACT FROM AUTHOR]

Paracetamol oxidation by ozonation and H 2 O 2 /UV processes was investigated. The second-order rate constant for the reaction of paracetamol with ozone was determined at pH 7.2 ( k O 3 / PRC = 2.57 × 10 6 M - 1 s - 1 ) . The rate constant of the elementary reaction of ozone with the ionized form of PRC was then calculated and the pH dependence of the ozonation reaction of PRC was estimated. The second-order rate constant of the reaction of paracetamol with HO radicals was also determined at pH 5 through the H 2 O 2 /UV oxidation system ( k HO / PRC = 4.94 × 10 9 M - 1 s - 1 ) . In the light of the high rate constants obtained, two conclusions on the kinetics of paracetamol ozonation in real water were drawn: (i) hydroxyl radicals do not have any impact on the removal of paracetamol during ozonation of real waters; (ii) a half-life of 0.03 s can be estimated for paracetamol, for a residual ozone concentration of 0.4 mg L − 1 . Hydroquinone and two other ozonation transformation products were identified by LC/UV, LC/MS and MS/MS analyses. In parallel, for the first time, toxicity was measured in ozonated paracetamol solutions with the luminescent bacteria Vibrio fisheri test. The results showed an increase in toxicity as paracetamol degraded. This toxicity could not be assigned to hydroquinone formation only. One or several other transformation products more toxic than paracetamol might be formed. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the control of a wastewater treatment pilot by catalytic ozonation. In general, catalytic ozonation processes operate with a deliberate ozone overproduction to obtain a treated water which respects discharge standards. But, in this case, the oxygen consumption is not optimal and the operating costs are important. The objective of this study focuses on the optimization of the catalytic ozonation reactor. A continuous-time transfer function model is identified to represent the pilot behavior, and an optimal control is proposed to obtain a significant abatement of the pollutant. In this application, the pollutant abatement is represented by the absorbance. [Copyright &y& Elsevier]