Electrochemically Enhanced Fenton’s Reaction

A wide range of gaseous and particulate phase pollutants are emitted into the atmosphere by routes like external or internal combustion,evaporation,eolian and others.Once released into the atmosphere,these primary emissions are dispersed,transported and,at the same time,transformed by various chemical processes that determine their ultimate environmental fate.The secondary products of these processes are more important ones concerning their effects on human health and the quality of the environment,which represent the critical property determining the establishment of certain air standards and regulatory policies.The prevalence of tropospheric photooxidants is of international concern because of their adverse effects on human health and environment.A lot of nitrogen oxides(NOx) and volatile organic compounds(VOCs) have been emitted from natural and factitious sources,and then transform into secondary photochemical oxidants by the atmospheric oxidation reactions,contributing to atmospheric oxidation capacity and climate change patterns.The formation of secondary photochemical oxidants including ozone(O3),gaseous nitric acid(HNO3),hydrogen peroxide(H2O2) and peroxy acetyl nitrate(PAN) is driven by hydroxyl radical(OH) during the daytime whose main sources are photolysis of O3 and nitrous acid(HONO).At night,the nitrite radical(NO3) substitutes OH radical and plays the most important role in the nighttime atmospheric chemical processes.However,the more complicated situation is that aerosol particles are ubiquitous in the Earth's atmosphere.As reactive surfaces they can take part in the heterogeneous reactions with secondary photochemical oxidants.It changes the tropospheric composition and the properties of the gaseous reactants,making the atmosphere pollution even more serious.It also alters the properties of aerosols like hygroscopicity and influences the radiation balance by the direct and indirect effects.Thus,many efforts have been made to this subject,which has become one of focuses of the atmospheric chemical research currently.In order to make clear the intricate coupling effect between secondary photochemical oxidants and aerosol particles,laboratory simulation is basic.Aerosol samples produced in the laboratory or collected in the atmosphere are selected and put into the reactor such as flow tube,Knudsen cell or aerosol chamber,which react with the secondary photochemical introduced.The kinetics processes and products can be detected by the equipment involving mass spectrometry(MS),Fourier transform infrared spectrometry(FTIR),diffuse reflectance infrared Fourier transform(DRIFTS) and aerosol mass spectrometry(AMS),which are connected to the reactors.Chromatography and surface characterization techniques also can be applied to detect the heterogeneous reaction as the off-line methods.Laboratory researches about heterogeneous kinetic and mechanism are of importance to understand this coupling effect,which could contribute to comprehending the field observed events and provide the basic parameters to model forecast.Research on heterogeneous reactions of secondary photochemical oxidants is challenging.However,there are some aspects that are not clear,and more studies are needed.First,the researches mainly concentrate on the O3 and HNO3 heterogeneous reactions,while less about others.The data must be enriched through the future studies.Second,the reaction system often has isolated secondary photochemical oxidant and individual particles,which is not consistent with real atmospheric composition.It leads certain error between the results from laboratory simulation and field observation.Last but not least,no commercial equipment is applicable to this area.Researchers must establish high-precision and sensitive apparatuses to detect the transformation of reactants under atmospheric conditions.In this review,the formation of secondary photochemical oxidants is introducesd and the recent international laboratory researches and state of the art with regard to this area are concluded.In the end the main scientific problems are put forward,and the prospect is made.

The Origin of the Hydroxyl Radical Oxygen in the Fenton Reaction

Electrocoagulation (EC) using aluminum (Al) and stainless steel (SS) electrodes was investigated for color and chemical oxygen demand (COD) removal from a simulated spent disperse dyebath. EC was optimized for electrolyte (NaCl) concentration (750–3000 mg/L), current density (9–87 mA/cm2), and initial pH (3.5–11.5). Optimum EC conditions were established as 2,500 mg/L NaCl, pHo = 7.0 and 44 mA/cm2 for 100% color and 58% COD removals using Al electrodes (total treatment time = 30 min), whereas 100% color and 45% COD removals were obtained for 2,000 mg/L NaCl, pHo = 7.3 and a current density of 44 mA/cm2 when SS electrodes were employed for a 60-min treatment. EC results were compared with color and COD removals achieved via coagulation with alum, ferrous sulfate, and ferric chloride at varying doses (200–2,000 mg/L). Alum was more effective in color (100%) and COD (64%) removals than ferrous sulfate and ferric chloride. The amount of sludge formed during EC using SS electrodes was approximately 10 times less than the sludge produced during EC with Al electrodes, whereas electrical energy requirements to achieve 100% color and 50% COD removals were 10 and 30 times higher, respectively, when SS electrodes were employed for EC.

Micropollutants are emerging as a new challenge to the scientific community. The discharge of treated effluent from wastewater treatment plant (WWTP) is a major pathway for the introduction of emerging contaminants into surface water. Solar advanced oxidation processes can achieve high and consistent micropollutants' removal. This study deals with the destruction of trace organic contaminants in secondary treated effluents by (i) sulphate radical based (SO 4 -) homogeneous photo-Fenton using peroxymonosulphate as an oxidant, ferrous ion Fe(II) as catalyst, (ii) hydroxyl radical (○ OH) heterogeneous photocatalysis using suspended titanium dioxide (TiO 2) as catalyst, (iii) photolysis and solar irradiation as a light source. Solar advanced oxidation processes of wastewater was conducted in a panel solar pilot and the efficiency of this treatment was evaluated on the basis of micropollutants' disappearance, reduction of total organic matter content (TOC), and measurement of the final estrogenicity. The chemical analyses of the wastewater collected showed that several contaminants persisted at the end of its treatment in the WWTP. Contaminants elimination was followed by Liquid Chromatography/Quadrupole ion trap Mass Spectrometry analysis after a pre-concentration 100:1 by solid phase extraction. 74 target micropollutants were identified. Some of them were found at trace level also after the applied AOPs. The ecotoxicity of the effluent wastewater was evaluated using different commonly adopted bio-tests as Daphnia magna, Vibrio fischeri, Brachionus calyciflorus, Spirodela polyrhiza, Pseudokirchneriella subcapitata. These standard methods can give an idea about of quality of wastewater, but they are not able to respond also to the presence of estrogenic activity, that can be a crucial problem. For overtake this point, the treatment efficiency was provided by estrogenic activity measurements based on the use of bioluminescent HELN ERa cell line. The order of micropollutants elimination efficiency under the experimental condition evaluated was solar heterogeneous photocatalysis with TiO 2 > solar PMS/Fe (II) >solar photolysis.

Potential involvement of alkoxyl and hydroxyl radicals in the peroxidative action of oxyfluorfen

Effects of various chemical compounds on spontaneous and hydrogen peroxide-induced reversion in strain TA104 of Salmonella typhimurium

Oxygen contribution to phenolic evolution during aging of red wines

Chapter 6 - Treatment of Industrial wastewater through new approaches using Algae biomass

Water protection is one of the most important priorities of environmental protection. It is necessary to reduce pollution of wastewater in order to reduce pollution of drinking‐water and water pools. One of the most dangerous wastewater pollutants are heavy metals (HM). They have a negative influence on people and aquatic water systems. The paper analyses possibilities of the sorption method application for heavy metal elimination from waste‐water. Experimental investigation of HM sorption from water and numerical modeling usage possibilities for prognosis of the HM sorption kinetic process was carried out as well as experimental study of HM elimination efficiency dependence on sorption time of HM from wastewater, when using sorbents. Two pseudo kinetic models, i e the pseudo first‐ and second‐order models, were developed on the basis of experimental investigation. These models were applied in numerical modeling in the computer program PHOENICS. The results of the computer program PHOENICS and th...

Oxidative stress in clinical situations - fact or fiction?

Evaluation of chemicals to control the generation of malodorous hydrogen sulfide in waste water

Biochar (B) and pumice (P) enhance water retention and soil-plant productivity, while arbuscular mycorrhizal fungi (AMF) improve plant access to soil moisture and promote productivity. The use of recycled wastewater (WW), is an effective approach to protect freshwater resources, increases soil-plant fertility, reduces the need for fertilizer, and contributes to the sustainable European Green Consensus by reducing the discharge of WW. However, the heavy metal (HM) content of WW can negatively affect the environment, soil, and plant health. The study investigated the B, P, and their combination (B+P) in the soil of pepper irrigated with different water qualities in conditions with and without AMF, hypothesized that B+P under AMF would limit HM contamination in irrigation with WW, in addition to reducing irrigation water quantity (IWQ) and increasing irrigation water productivity (IWP), and soil-plant efficiency. As a result, IWP increased between 14% and 38% in parallel with the IWQ reduction by 2% to 15%, and yield increased between 7% and 20% with B+P, B, P, respectively, also AMF and WW. These treatments increased the yield of the plant by improving the organic matter, total nitrogen, and cation exchange capacity of the soil, but a moderate increase in soil salinity for B and WW treatments, thus increasing the electrolyte leakage. Although there was more Fe, Cu, Mn, Zn, Pb in the soil of the B, P, B+P and AMF and WW, no-contamination was observed and B, P, B+P increased the plant's uptake of Fe, Cu, Mn, Zn, Pb while limiting the uptake of Cd, Cr, Ni, and AMF also created a barrier in the uptake of HM. However, in WW, the accumulation of HM in pepper was higher but did not exceed threshold values. It was found that B+P under AMF conditions can be safely used in irrigation with WW due to its effects in reducing HM, its regulating properties of soil and plants, and its increase in IWP.

Substantial formation of reactive oxygen species (ROS) is inevitable in aerobic life forms. Due to their extremely high reactivity and short lifetime, hydroxyl radicals are a special case, because cells have not developed enzymes to detoxify these most dangerous ROS. Thus, scavenging of hydroxyl radicals may only occur by accumulation of higher levels of simple organic compounds. Previous studies have demonstrated that plant-derived sugars show hydroxyl radical scavenging capabilities during Fenton reactions with Fe(2+) and hydrogen peroxide in vitro, leading to formation of less detrimental sugar radicals that may be subject of regeneration to non-radical carbohydrates in vivo. Here, we provide further evidence for the occurrence of such radical reactions with sugars in planta, by following the fate of sucralose, an artificial analog of sucrose, in Arabidopsis tissues. The expected sucralose recombination and degradation products were detected in both normal and stressed plant tissues. Oxidation products of endogenous sugars were also assessed in planta for Arabidopsis and barley, and were shown to increase in abundance relative to the non-oxidized precursor during oxidative stress conditions. We concluded that such non-enzymatic reactions with hydroxyl radicals form an integral part of plant antioxidant mechanisms contributing to cellular ROS homeostasis, and may be more important than generally assumed. This is discussed in relation to the recently proposed roles for Fe(2+) and hydrogen peroxide in processes leading to the origin of metabolism and the origin of life.

Using a lysosome-enriched "light mitochondrial" fraction of a rat liver homogenate, the effects of the reactive oxygen species hydrogen peroxide, superoxide- and hydroxyl radicals were determined. Alterations in the intralysosomal pH and the release of a lysosomal marker enzyme, N-acetyl-glucosaminidase, were used as indicators of changes in the lysosomal membrane integrity. Lipid peroxidation of the fraction was assayed by TBARS measurement. Neither superoxide radicals, generated by hypoxanthine/xanthine oxidase, nor a bolus dose of hydrogen peroxide (0.5-1.5 mM) induced any lysosomal damage. If, however, Fe(III)ADP was included in the superoxide radical-generating system, lysosomal membrane damage was detected, both as an increase in lysosomal pH and as a release of N-acetyl-glucosaminidase, but only after a lag phase of about 7 min. Lipid peroxidation, on the other hand, proceeded gradually. Lysosomes treated with hydrogen peroxide displayed similar dose-dependent alterations, albeit only if both Fe(III)ADP and the reducing amino acid cysteine were added. In the latter system, however, alterations of the lysosomal membrane stability occurred more rapidly, showing a lag phase of only 2 min. Lipid peroxidation, which proceeded faster and displayed no lag phase, levelled out within 10 min. The results indicate that neither superoxide radicals nor hydrogen peroxide are by themselves damaging to lysosomes. Available catalytically active iron in Fe(II) form, however, allows reactions yielding powerful oxidative species--probably hydroxyl radicals formed via Fenton reactions--to take place inducing peroxidation of the lysosomal membranes resulting in dissipation of the proton-gradient and leakage of their enzyme contents.

Abstract: Phosphonoformic acid (foscarnet) is an antiviral agent that is used to treat severe cytomegalovirus infections in AIDS patients. We demonstrate by using the ferrous iron indicator Ferrozine and ascorbic acid (vitamin C) that foscarnet can chelate ferric iron and form a redox‐active iron complex. By using the hydroxyl radical indicator coumarin‐3‐carboxylic acid we found that the foscarnet‐Fe3 complex formed can readily catalyze hydroxyl radical (˙OH) generation by the Fenton reaction: (Fe2++ H2O2→Fe3++˙OH +−OH) if hydrogen peroxide and ascorbic acid are present. Hydroxylation of coumarin‐3‐carboxylic acid could be blocked by addition of known hydroxyl radical scavengers such as mannitol, sucrose, glucose and dimethyl sulfoxide. Moreover, by using a DNA nicking assay, we found that foscarnet catalyzed hydroxyl radicals can induce single strand brakes in DNA. The potency of the hydroxyl radicals formed to induce damage could also be demonstrated in a phosphate‐free buffer where the hydroxyl radicals formed attacked and liberated phosphate from the foscarnet molecule. Our results indicate that foscarnet catalyzed hydroxyl radical formation might take place during conditions where a peroxide generating system(s), vitamin C and transitions metals are present.