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ABSTRACT: The cathodic electrogeneration of hydrogen peroxide in seawater by means of oxygen reduction on a gas diffusion cathode was
studied. The effects on the reaction yield of several operative parameters such as cell design, medium composition, anolyte
concentration, pH and working potential were investigated. Results indicate that in a two-compartment cell notable concentrations
of hydrogen peroxide are obtained with a constant yield in a wide range of charge. Lower catholyte pH values, obtainable by
means of the anolyte choice, mitigate the decrease in the efficiency due to cathode fouling. Application of hydrogen peroxide
electrogeneration to seawater disinfection was also tested. Comparative tests conducted using both commercial and electrogenerated
hydrogen peroxide, either alone or combined with iron in Fenton’s treatment, are also presented.
Journal of Applied Electrochemistry 06/2008; 38(7):997-1003. · 1.75 Impact Factor
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ABSTRACT: Biofilms of sulfate-reducing bacteria Desulfovibrio desulfuricans G20 were used to reduce dissolved U(VI) and subsequently immobilize U(IV) in the presence of uranium-complexing carbonates. The biofilms were grown in three identically operated fixed bed reactors, filled with three types of minerals: one noncarbonate-bearing mineral (hematite) and two carbonate-bearing minerals (calcite and dolomite). The source of carbonates in the reactors filled with calcite and dolomite were the minerals, while in the reactor filled with hematite it was a 10 mM carbonate buffer, pH 7.2, which we added to the growth medium. Our five-month study demonstrated that the sulfate-reducing biofilms grown in all reactors were able to immobilize/reduce uranium efficiently, despite the presence of uranium-complexing carbonates.
Environmental Science and Technology 01/2008; 41(24):8349-54. · 5.23 Impact Factor
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ABSTRACT: Lab-scale experiments of in situ chemical oxidation (ISCO), were performed on soil contaminated with 100 mg kg(-1) of atrazine (CIET). The oxidant used was hydrogen peroxide catalysed by naturally occurring minerals or by soluble Fe(II) sulphate, added in aqueous solution. The oxidation conditions were: CIET:H2O2=1:1100, 2 PV or 3 PV reaction volume, Fe(II):H2O2=0, 1:22, 1:11. Stabilized (with KH2PO4 at a concentration of 16 g l(-1)) or non-stabilized hydrogen peroxide was used. The pH of the reagents was adjusted to pH=1 with sulphuric acid, or was not altered. Results showed that the addition of soluble Fe(II) increased the temperature of the soil slurry and the use of stabilized hydrogen peroxide resulted in a lower heat generation. The treatment reduced the COD of the soil of about 40%, pH was lowered and natural organic matter became less hydrophobic. The highest atrazine conversion (89%) was obtained in the conditions: 3 PV, Fe(II):H2O2=1:11 with stabilized hydrogen peroxide added in two steps. The stabilizer only increased H2O2 life-time significantly when soluble Fe(II) was added. Results indicate as preferential degradation pathway of atrazine in soil dechlorination instead of dealkylation.
Chemosphere 04/2006; 62(9):1481-9. · 3.21 Impact Factor
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ABSTRACT: An electro-Fenton treatment of a solution containing phosphorus compounds using a graphite electrode is described. Different operating conditions are tested to investigate the influence of the reagent ratio on the oxidative efficiency. Results show that electro-Fentons reagent is able to provide a powerful conversion of the phosphorous compounds into phosphate. As hydrogen peroxide is continuously provided by the cathodic reduction of oxygen, the crucial step appears to be the iron dosage whose optimal concentration is found in the range 50–150mgl–1. Quantitative oxidation is not reached for concentration lower than 50mgl–1. Nonetheless, an excess of both iron and hydrogen peroxide in the bulk is found to negatively affect the oxidation yield because of the occurrence of undesired side reactions.
Journal of Applied Electrochemistry 03/2005; 35(4):391-398. · 1.75 Impact Factor
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ABSTRACT: This work studies the production of hydrogen peroxide through the cathodic reduction of oxygen in acidic medium, by comparing the results obtained using a commercial graphite and a gas diffusion electrode. A low pH was required to allow the application of hydrogen peroxide generation to an electro-Fenton process. The influence of applied potential and the gas flow composition were investigated. The gas diffusion electrode demonstrates a higher selectivity for hydrogen peroxide production, without significantly compromising the iron regeneration, thus making its successful application to a cathodic Fenton-like treatment, possible. Unlike the graphite cathode, the gas diffusion cathode also proved to be effective in the air flow.
Journal of Applied Electrochemistry 01/2005; 35(4):413-419. · 1.75 Impact Factor
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ABSTRACT: The influence of humic substances on the electrochemical treatment of solutions resulting from the remediation of atrazine contaminated soil has been investigated. In particular the effect on the hydrogen peroxide production stage and the effect on the hydroxyl radical oxidation treatment have been separately studied. In order to quickly assess the possible inhibition of the removal, an inorganic system has been adopted as a standard system. The results confirm the validity of electrochemical technologies also for the treatment of a real effluent where a matrix effect is expected since the organic matter content affects only the hydrogen peroxide production.
Annali di Chimica 01/2004; 93(12):997-1004. · 0.99 Impact Factor
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ABSTRACT: In this study a process for the remediation of soils contaminated by lead or copper is proposed, consisting of the operations in sequence: soil flushing, membrane treatment, acidification, and metal precipitation. Pb(II) and Cu(II) extraction from a synthetically contaminated soil using a 0.05 M EDTA aqueous solution were investigated in column. The metal removal efficiencies and the final soil metal concentration were 98.2% and 37.96 mg/g respectively for lead and 95.4% and 59.20 mg/kg for copper. The extracted solutions were concentrated through a membrane treatment to reduce the water content up to the 75% and to obtain a permeate metal concentration in compliance with the Italian Environmental Regulation. The recovery of the used EDTA from the retentate solution, with recovery yield of at least 85.4%, was also obtained through acidification. Metal precipitation from the filtered solution was then performed according two different methods, achieving metal removal yield of more than 99.4%.
Annali di Chimica 01/2004; 93(12):1005-11. · 0.99 Impact Factor
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ABSTRACT: In the present work a Fenton's treatment for the oxidation of a phosphorous compounds mixture, simulating a match manufacturing industry wastewater, were studied. Experimental tests were performed on three sample solutions at a phosphorus concentration of 250, 500 and 750 mg/l. In each solution an equal amount of sodium phosphite and sodium hypophosphite was dissolved. The investigation of pH, temperature and reagents ratio on the oxidation rate led to the individuation of the optimal process operating conditions. The results show that Fenton's reagent provides a powerful conversion to phosphate of the phosphorous solution. In particular at pH=3.5 and 20 degrees C a residual concentration of non oxidized phosphorus in compliance with the Italian regulation limits for industrial wastewater disposal. Tests performed on sample solution of 500 mg/l P and 750 mg/l P by adding hydrogen peroxide and bivalent iron in three sequential steps led to similar reaction efficiencies to tests carried out adding both Fenton's reagents in one step, but with a remarkably lower reagents consumption.
Annali di Chimica 12/2003; 93(11):935-45. · 0.99 Impact Factor
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ABSTRACT: Microbial biosensors are promising tools for the detection of specific substances in different fields, such as environmental, biomedical, food or agricultural. They allow rapid measurements, no need for complex sample preparation or specialized personnel and easy handling. In order to enhance the managing, miniaturization and stability of the biosensor and to prevent cell leaching, bacteria immobilization is desirable. A systematic characterization procedure to choose a suitable immobilization method and matrix, was proposed in this study. Physical properties, storage stability mass transport phenomena and biocompatibility were evaluated, employing agarose as the model matrix. Preliminary essays with bioluminescent bacteria detecting Tributyltin were also carried out.
Hemijska Industrija. 01/2003;
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ABSTRACT: The electrochemical oxidation of an atrazine solution obtained from a flushing treatment of a contaminated soil was investigated. The influence of ethanol on atrazine oxidation was studied. Results show that the electrogenerated Fenton's reagent provides a complete degradation of atrazine and its main chlorinated by-products via N-dehalkylation and dechlorination. This process therefore presents an effective alternative to the chemical oxidation treatment which necessarily needs a further biological state.
Annali di Chimica 11/2002; 92(10):1007-13. · 0.99 Impact Factor
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ABSTRACT: In this paper a process for the treatment of landfill leachate involving evaporation and reverse osmosis was proposed. Experimental tests were performed on an industrial landfill leachate. The leachate was subjected to evaporation so as to obtain a distillate containing a small amount of organic material and a substantial amount of inorganic substances (consisting primarily of metals and ammonium salts). The distillate of the evaporation treatment was then subjected to reverse osmosis. The reverie osmosis tests were performed using two different membranes: the AD membrane (thin two-ply film of polyamide) and the SC membrane (thin three-ply film of polyamide). Tests carried out at different values of pH showed a reduction of organic content of about 88% when AD membranes were used and about 80% with SC membranes independently of pH. As regards ammonium, comparable reductions of over 97% were registered for both types of membrane in the optimal conditions of pH = 6.4 (97.1% for AD membranes and 97.7% for SC).
Waste Management 02/2002; 22(8):951-5. · 2.43 Impact Factor
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ABSTRACT: The electrogeneration of polymeric phosphorus compounds during the anodic oxidation of aqueous solutions of phosphites on a boron-doped diamond electrode has been studied. Although the main oxidation product is orthophosphate, the results indicate the simultaneous generation of short-chain and cyclic compounds containing two and three phosphorus atoms whose evolution has been followed by ion chromatography.The effect on the reaction yield of several operative parameters such as current density, pH, temperature and initial phosphite concentration has been investigated.Consistently with the data presented, a new process for the generation of polymeric phosphates is obtained.
Electrochimica Acta.
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ABSTRACT: The different currently used Fenton-type treatments, either chemically or electrochemically generated, are reviewed. A particular attention is devoted to the traditional Fe++/H2O2 chemical process and to the indirect electrochemical oxidation which uses in situ generated hydrogen peroxide. Mechanisms and experimental conditions employed for the optimisation of each technology are reported; moreover advantages and main limitations are discussed.
Annali di Chimica 93(9-10):761-70. · 0.99 Impact Factor
