Academic literature on the topic 'Photo-Fenton-like'

Nicosulfuron, a sulfonylurea herbicide, was subjected to different Fenton reactions at pH of a nicosulfuron aqueous solution (pH 5). Usually, the optimal pH for the Fenton reaction is between 3 and 4, but the addition of acids is not environmentally acceptable. This is the reason why the reactions were performed at a higher pH value than usual. So, classical Fenton and Fenton-like reactions were applied as well as photo-Fenton and photo-Fenton-like reactions. In addition, microwave Fenton and Fenton-like reactions were used in nicosulfuron degradation. Influences of Fe2+ and Fe3+ concentrations, as well as hydrogen peroxide concentrations, were studied. The Fenton reaction was much faster and more efficient than the Fenton-like reaction, while the photo- Fenton reaction proceeded much faster and more efficiently than the Fenton reaction. The microwave-Fenton and microwave-Fenton-like reactions proceeded with increased efficiency in comparison to the Fenton and Fenton-like reactions. The phytotoxicity and acute toxicity of the reaction products of nicosulfuron oxidation by the photo-Fenton reaction were analyzed. The toxicity testing of nicosulfuron treatment by photo-Fenton process showed a decrease in phytotoxicity, while the acute toxicity tests showed that the samples after treatment had lower toxicity.

In this investigation, UV/H2O2, UV/H2O2/Fe2+ (photo-Fenton) and UV/H2O2/Fe3+ (photo-Fenton-like) systems were used to mineralize sulfamethizole (SFZ). The optimal doses of H2O2 (1–20 mM) in UV/H2O2 and iron (0.1–1 mM) in photo-Fenton and photo-Fenton-like systems were determined. Direct photolysis by UV irradiation and direct oxidation by added H2O2, Fe2+ and Fe3+ did not mineralize SFZ. The optimal dose of H2O2 was 10 mM in UV/H2O2 and that of iron (Fe2+ or Fe3+) was 0.2 mM in both UV/H2O2/Fe2+ and UV/H2O2/Fe3+ systems. Under the best experimental conditions and after 60 min of reaction, the SFZ mineralization percentages in UV/H2O2, UV/H2O2/Fe2+ and UV/H2O2/Fe3+ systems were 16, 90 and 88%, respectively. The UV/H2O2/Fe2+ and UV/H2O2/Fe3+ systems effectively mineralized SFZ.

Abstract The oxidative degradation of CV dye in aqueous media has been evaluated using Fenton (Fe2+/H2O2) and photo-Fenton (Fe2+/H2O2/UV) processes. Various operational parameters like H2O2 dosages, Fe2+ dosages and [CV]0 were optimized of both Fenton and photo-Fenton processes for the removal of CV dye from aqueous media. Kinetic results indicated that photo-Fenton process (kobs=0.0097 min−1, t1/2=71.45 min) is more effective than Fenton process (kobs=0.0074 min−1, t1/2=93.66 min). Second order rate constant of ˙OH radical with CV dye was calculated to be 3.96×109 M−1s−1. De-methylated organic intermediates of CV dye detected by LC-MS and some other intermediates like CH3COO−, HCOO−, NH4+ and Cl− were identified by ion-chromatography.

This study applies photo-Fenton and photo-Fenton-like systems to decolorize C.I. Reactive Red 2 (RR2). The oxidants were H2O2 and Na2S2O8; Fe2+, Fe3+, and Co2+ were used to activate these two oxidants. The effects of oxidant concentration (0.3–2 mmol/L) and temperature (25–55 °C) on decolorization efficiency of the photo-Fenton and photo-Fenton-like systems were determined. The decolorization rate constants (k) of RR2 in the tested systems are consistent with pseudo-first-order kinetics. The rate constant increased as oxidant concentration and temperature increased. Activation energies of RR2 decolorization in the UV/H2O2/Fe2+, UV/H2O2/Fe3+, UV/Na2S2O8/Fe2+ and UV/Na2S2O8/Fe3+ systems were 32.20, 39.54, 35.54, and 51.75 kJ/mol, respectively.

Photo-Fenton-like treatment of the commercially important naphthalene sulphonate K-acid (2-naphthylamine-3,6,8-trisulphonic acid) was investigated using UV-C, UV-A and visible light irradiation. Changes in toxicity patterns were followed by the Vibrio fischeri bioassay. Rapid and complete degradation of K-acid accompanied with nearly complete oxidation and mineralization rates (>90%) were achieved for all studied irradiation types. On the other hand, detoxification was rather limited and did not change significantly during photo-Fenton-like treatment. Several oxidation products could be identified via liquid chromatograph–mass spectrometer analyses, such as desulphonated and hydroxylated naphthalene derivatives, quinones, and ring-opening as well as dimerization products. Photo-Fenton-like treatment of K-acid with UV-C, UV-A and visible light irradiation occurred through a series of hydroxylation and desulphonation reactions, followed by ring cleavage. A common degradation pathway for photo-Fenton-like treatment of K-acid using different irradiation types was proposed.

Cuprous oxide that was prepared from Cu-containing waste liquid from a printed circuit board manufacturer was used to carry out Fenton-like and photo-Fenton-like oxidation reactions to decolorize a reactive dye (RB19). A microwave hydrothermal method was applied in the synthesis. The highest recovery rate of Cu from wastewater was 87% and was obtained when the synthesis was performed at a power of 200 W for 15 min. An RB19 decolorization efficiency of 99.9% was achieved when the Fenton-like reaction was conducted with 50 mmol/L H2O2 and 0.9 g/L of Cu2O. The decolorization of RB19 was more effective when the system was irradiated with visible light than with UV light. Under irradiation, the decolorization rate was the highest when the decolorization was performed in the RB19 solution that contained 50 mmol/L H2O2 and 0.9 g/L CuO2 in the Fenton-like and the 365 nm-irradiated photo-Fenton-like reactions. In the case of irradiation under 410 nm visible light, the system was operated with lower H2O2 (30 mmol/L) and Cu2O (0.5 g/L) to achieve a decolorization rate higher than 365 nm-irradiated photo-Fenton-like reactions.

Photo-Fenton degradation of pollutants in wastewater is an ideal choice for large scale practical applications. Herein, two-dimensional (2D) in-plane CuS/Bi2WO6 p-n heterostructures have been successfully constructed by an in situ assembly strategy and characterized using XRD, XPS, SEM/TEM, EDX, UV-Vis-DRS, PL, TR-PL, ESR, and VB-XPS techniques. The XPS and the TEM results confirm the formation of CuS/Bi2WO6 heterostructures. The as-constructed CuS/Bi2WO6 showed excellent absorption in visible region and superior charge carrier separation efficiency due to the formation of a type-II heterojunctions. Under visible light irradiation, 0.1% CuS/Bi2WO6 heterostructure exhibited the best photo-Fenton-like catalytic performance. The degradation efficiency of Rhodamine B (RhB, 20 mg·L−1) can reach nearly 100% within 25 min, the apparent rate constant (kapp/min−1) is approximately 40.06 and 3.87 times higher than that of pure CuS and Bi2WO6, respectively. The degradation efficiency of tetracycline hydrochloride (TC-HCl, 40mg·L−1) can reach 73% in 50 min by employing 0.1% CuS/Bi2WO6 heterostructure as a photo-Fenton-like catalyst. The promoted photo-Fenton catalytic activity of CuS/Bi2WO6 p-n heterostructures is partly ascribed to its low carriers recombination rate. Importantly, CuS in CuS/Bi2WO6 heterostructures is conducive to the formation of heterogeneous photo-Fenton catalytic system, in which Bi2WO6 provides a strong reaction site for CuS to avoid the loss of Cu2+ in Fenton reaction, resulting in its excellent stability and reusability. The possible photo-Fenton-like catalytic degradation mechanism of RhB and TC-HCl was also elucidated on the basis of energy band structure analysis and radical scavenger experiments. The present study provides strong evidence for CuS/Bi2WO6 heterostructures to be used as promising candidates for photo-Fenton treatment of organic pollutants.

As an essential resource for life and most human activities, water resources protection have become one of the major focuses of scientific community, especially the increasing occurrence of emerging pollutants which have its origin in commonly used pharmaceuticals, personal care products, pesticides and some other anthropogenic origin compounds. Fenton and photo-Fenton are advanced oxidation processes (AOPs) that have been widely proved on the removal of these compounds, but they are conventionally applied at acidic pH, below 3.0, because these processes involve the use of iron (II) salts, which are not soluble above. Also, the acidic effluents must be neutralized and high amounts of iron sludge are formed in the process. Current research in the field tries to solve this drawback by focusing in two possible solutions: the use of chelating agents to keep iron soluble at circumneutral pH or the use of heterogeneous catalysts containing iron that can be easily removed and reused after its application. This work is focused on the study, application and improvement of alginate-based heterogeneous catalysts for conducting photo-Fenton reactions at circumneutral pH. Initially, the preparation process of the conventionally used Fe(III)/alginate catalyst was optimized by evaluating the effect of the parameters involved on its synthesis. Then, the synthetized catalyst was applied to the abatement of antibiotic sulfamethoxazole (SMX), which was used as reference compound. The reaction mechanism of alginate-based catalysts was proposed according to the results obtained. Also, a deep study about catalyst stability revealed a high dependence with water’s pH. Fe(III)/alginate catalyst proved to release iron when sample’s pH was below alginate’s pKa. Also, due to its organic nature, a significant HO· scavenging effect of alginate itself was observed, which reduced the effective amount of hydroxyl radicals available for the oxidation of the target compound. Fe(III)/alginate was also tested for disinfection by adjusting the conditions to ensure a minimal iron release. Thus, the contribution of homogeneous reaction was significantly avoided. The catalyst proved being able to be used for disinfection of waters with low organic loads. In order to improve the Fe(III)/alginate catalyst, some modifications were applied. The first one was the addition of a dehydration stage after its synthesis. The resulting catalyst was tested on the removal of SMX and had a similar effectiveness than the conventionally used Fe(III)/alginate but with a significantly lower iron release, which confirmed its improved stability. This more stable catalyst was also modified by including TiO2, zero valent iron (ZVI) particles or cerium on its structure with the aim of, not only increase its stability, but its effectiveness. The TiO2 catalyst proved to increase the effectiveness of the overall removal of SMX while the other two modifications did not. Red volcanic rocks, iron shavings from metallurgical industry, a commercial Fe/Mn/O catalyst and a self-synthetized Fe/Ce/O catalyst were also tested as heterogeneous catalysts for Fenton and photo-Fenton at acidic and neutral pH. These catalysts were selected as inorganic-based ones and were compared to the Fe(III)/alginate dehydrated catalyst when applied to photo- Fenton at neutral pH. Results proved that only volcanic rocks had a significant activity when applied for photo-Fenton at neutral pH, but the effectiveness on the removal of SMX was low in comparison to the alginate-based catalyst. All other catalysts presented too low activity or major drawbacks that made them not suitable for water purification through Fenton-like and photo-Fenton-like processes.
Los procesos Fenton y foto-Fenton son procesos de oxidación avanzada (POA) que se basan en la descomposición del peróxido de hidrógeno catalizada por sales de hierro (II), produciendo radicales hidroxilo que son altamente oxidantes. El segundo además incorpora la irradiación con luz ultravioleta en el rango A, cosa que permite acelerar el proceso debido a la recuperación del hierro (II), que durante la reacción principal pasa a hierro (III). Estos procesos se suelen llevar a cabo a pH ácido (pH<3) debido a la baja solubilidad y la poca actividad de las especies de hierro a pH cercanos a la neutralidad. Este trabajo se centra en el estudio y aplicación de un catalizador heterogéneo de Fe/alginato formado gracias a la propiedad del alginato de formar geles sólidos en presencia de cationes di y trivalentes. En este caso, el Fe(III) actúan como enlace entre cadenas de alginato. Inicialmente se estudió el proceso de fabricación de este catalizador y se propuso un proceso estándar optimizado para su uso aplicado a la reacción foto-Fenton. Posteriormente se evaluó su aplicación a la eliminación del antibiótico sulfametoxazol y a la desinfección de bacterias Escherichia Coli. Basándose en los resultados obtenidos se propuso un mecanismo de reacción que además explicaba la inestabilidad observada experimentalmente que producía la liberación de hierro dependiendo del pH del medio de reacción, lo que desencadenaba la vía de reacción homogénea. Con la intención de mejorar la estabilidad del catalizador, se modificó el proceso de síntesis añadiendo una etapa de deshidratación controlada al final del proceso. Los resultados en su prueba para la reacción foto-Fenton aplicada a la eliminación de sulfametoxazol mostraron que el rendimiento no empeoraba pero mejoraba significativamente su estabilidad. Para aumentar su eficiencia se probó incorporar cerio, partículas de hierro monovalente y TiO2. Los resultados mostraron que solo el catalizador modificado con TiO2 mejoraba el rendimiento global de la reacción. Por último, se probaron otros catalizadores heterogéneos (piedras volcánicas, Fe/Ce/O, Fe/Mn/O, limaduras de hierro) aplicados a la reacción foto-Fenton. Solo las piedras volcánicas mostraron actividad catalítica y ésta, en comparación con la del catalizador de alginato fue baja.

In the last decades, the scientific community has been involved in the research of new kinds of contaminants generally known as of “emerging concern” (CECs). The harmfulness of CECs, even at small concentrations as well as, property of bioaccumulation and persistence, makes them extremely dangerous for the human health. The scientific community is constantly researching about novel treatments able to achieve the removal of these contaminants. Advanced Oxidation Processes (AOPs) are considered one of the most useful treatments to achieve CECs degradation. Among the AOPs, Fenton and photo‐Fenton processes are particularly powerful, cheap and easily managed. Nevertheless, some setting requirements of Fenton processes have limited their application at industrial scale. One of the most important limits is the necessity to operate a tight control of the pH in order to avoid iron precipitation (optimum pH~2.8). Unfortunately, the optimum pH for Fenton reaction is essentially far from the normal values of the wastewater treatment plant (WWTP) effluents. Scientific community is then working on the improvement of the operating conditions of Fenton processes in order to improve the applicability in wastewater treatment. These modifications are essentially focused on the possibility to perform the treatment at circumneutral pH (Fenton and photo‐ Fenton like processes). Fenton like processes can be carried out in heterogeneous or homogeneous way according to the phase of the catalyst into the solution. In this study was firstly confirmed the suitability of Fenton based processes in recalcitrant compounds removal. Fenton, UV‐A photo‐Fenton and UV‐C photo‐Fenton were, in fact, applied for atrazine removal from secondary effluent (SE) of municipal wastewater treatment plant (MWWTP). UV‐A and UV‐C photo‐Fenton allowed remove 50% and 100% of the initial atrazine content respectively. The main objective of this thesis was then the assessment of photo‐Fenton’s suitability for recalcitrant contaminant at circumneutral pH. Thus, homogeneous photo‐Fenton like at neutral pH was applied for sulfamethoxazole (SMX) removal. In order to avoid iron precipitation, chelating agents were used to keep soluble the iron at circumneutral pH. The chelating ability of four chelating agents (ethylenediaminetetraacetic acid‐EDTA, nitrilotriacetic acid‐NTA, oxalic acid and tartaric acid) was tested. Then, once determined the optimum molar ratio L:Fe for iron chelation (1.5:1 for EDTA and NTA, 10:1 for tartaric acid and 20:1 for oxalic acid), their catalytic activity was evaluated when employed in photo‐Fenton like for SMX removal. The highest SMX percentage removal, together with the minimum chelating agents required and the better property of biodegradability and low toxicity, demonstrated the suitability of NTA for the purpose. A further study on the stability of the chelates under reaction was carried out. The operating conditions adopted for the treatment significantly influence the stability of the chelate solution. Thus, in order to proper control the parameter set up the behavior of chelates has been study under thermal, oxidative and photochemical stress. It was demonstrated as the temperature control can represent an interesting tool to extend the chelates lifetime under oxidative and photochemical stress. By adopting different H2O2 doses, a linear correlation between doses and chelate decomposition could be identified. The better suitability of UV‐A irradiation, against UV‐C and Xe lamp, to preserve the iron chelate solution was demonstrated. Moreover, the influence of the influent characteristics on the process efficiency needed to be also considered. Thus, different water matrices were used for the experiments. The efficiency of photo‐Fenton like catalyzed by Fe(III)‐NTA has been compared when applied to different aqueous matrixes (Milli‐Q water, tap water, secondary effluent wastewater and well water). It was demonstrated as the ions content, especially Ca2+ and Mg2+, significantly compromise the process of chelation. High alkalinities and organic matter, instead, mainly influenced the phase of process, when acting as radicals scavengers, reduced the amount available for SMX oxidation. Some strategies were then adopted to promote SMX removal. Between them, Mn2+ mediated photo‐Fenton like showed somehow possibility for improvement. Highest removal rate was in fact exhibited in the first minutes of reaction when adding Mn2+ to the solution in ratio molar Mn:Fe 0.5:1. The conclusive study of the thesis regarded the assessment of the Br‐ presence on the efficiency achievable in recalcitrant compounds removal when applying UV/PS/Fe2+ for removal of benzophenone‐4 (BZ4), nitrobenzene (NB), nitrobenzoic acid (NBA), atrazine (ATZ) and ampicilline (AMP). Br‐ demostrated to be a strong inhibitor in the removal of all the considered contaminants except for NB when, the removal was instead enhanced in bromide containing water.

Cilj  ove  doktorske  disertacije  je  bio  razvoj  brzih  i  pouzdanih  voltametrijskih  metoda zasnovanih na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala (ugljenične  paste  napravljene  od  grafitnog  praha  i  parafinskog  ulja  i  štampanih  ugljeničnih elektroda)  za  određivanje  H ₂O₂ u  odabranim  složenim  model  i  realnim  uzorcima.  U  tu  svrhu, ispitana je primenljivost različitih radnih elektroda. Amperometrijska  metoda  zasnovana  na  elektrodi  od  ugljenične  paste  (CPE)  zapreminski modifikovane  sa  5%  (m:m)  MnO2 je,  pri  optimizovanim  uslovima  i  pri  radnom  potencijalu  od 0,40 V  u  odnosu  na  zasićenu  kalomelovu  elektrodu  (ZKE)  u  fosfatnom  puferu  pH  7,50  kao pomoćnom elektrolitu, omogućila kvantifikaciju H ₂O₂ u opsegu koncentracija od 1,4 do 65 µg mL -1 sa  relativnom  standardnom  devijacijom  (RSD)  manjom  od  10%.  Ova  metoda  je  primenjena  za određivanje sadržaja H ₂O₂ u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija)  tretirane  Fentonovim  (Fe ²⁺ i  H ₂O₂ )  i  Fentonu-sličnim  (Fe ³⁺ i  H ₂O₂ )  reagensima  u  cilju uklanjanja  prirodnih  organskih  materija  (POM)  pri  čemu  su  korišćene  različite  početne koncentracije  gvožđa  i  različiti  odnosi  molarnih  koncentracija  gvožđa  i  H ₂O₂ .  Utvrđeno  je  da oksidaciono  stanje  gvožđe  (Fe ²⁺ ili  Fe ³⁺)  i  molarni  odnos  jona  Fe  i  H ₂O₂ utiču  na  stepen potrošnje/razgradnje  H ₂O₂u  podzemnoj  vodi  sa  visokim  sadržajem  POM.  Takođe,  u  slučaju Fentonu-sličnog  procesa,  za  sve  početne  koncentracije  Fe ³⁺ i  H ₂O_{2 ,}  signifikantna  količina  H ₂O₂ ostaje  neiskorišćena,  što  ukazuje  na  nižu  efikasnost  ovakvog  sistema u  poređenju  sa  Fentonovim procesom.Štampana  ugljenična  elektroda  (SPCE)  zapreminski  modifikovana  sa  MnO 2 kao medijatorom  je  primenjena  za  određivanje  sadržaja  H ₂O₂ u  toku  Fentonovog  (Fe ²⁺ ,  H₂O₂ )  i vidljivom  svetlošću  potpomognutog  foto-Fentonovog  (Fe ²⁺ ,  H ₂O₂ ,  hν)  procesa  uklanjanja neonikotinoidnog  insekticida  acetamiprida  (ACT).  Pri  optimizovanim  uslovima  (radni  potencijal 0,40  V  u  odnosu  na  ZKE,  fosfatni  pufer  pH  7,50  kao  pomoćni  elektrolit)  amperometrijskog određivanja  H ₂O₂ ,  postignuta  je  linearnost  u  opsegu  koncentracija  0,01–1,24  mmol  L-1(0,34– 42,2 µg mL -1) i vrednost RSD nije prelazila 4,2%. U ispitivanimuzorcima (nakon odgovarajućegpodešavanja pH vrednosti od 2,8 do 7,5 odmah nakon  uzorkovanja radi stopiranja ili maksimalnog usporavanja  procesa  oksidacije,  filtriranja,  zamrzavanja  i  odmrzavanja  neposredno  pre  merenja) sadržaj  H ₂O₂ je  određen  metodom  standardnog  dodatka  analiziranjem  odgovarajućih amperometrijskih  krivi.  Paralelna  HPLC-DAD  merenja  su  vršena  u  cilju  praćenja koncentracije/uklanjanja ACT. U slučaju foto-Fentonovog procesa (početne koncentracije 0,31; 2,0 i 3,0 mmol L -1 (70,0; 111,7 i 102,1 µg mL -1 ) za ACT, Fe²⁺ i H ₂O₂, redom) nakon 10 min H ₂O₂ je izreagovao, a može se smatrati da je ACT uklonjen nakon 5 min. U toku Fentonovog procesa ACT je  uklonjen  nakon  20  min  tretmana  i  oko  10%  početne  koncentracije  H ₂O₂ je  ostalo  u  sistemuneiskorišćeno.CPE  je  površinski  modifikovane  kompozitom  na  bazi  nanočestica  Pt  (<  5  nm)  i grafitizovanog  ugljenika  (Pt-C,  10%  Pt  na  Vulkanu  XC72)   etodom  nanošenja  kapi. Nemodifikovana  CPE  i  modifikovana  (Pt-C/CPE)  su   okarakterisane  primenom  SEM/EDS  i  CV merenja.  Pt-C/CPE  je  pokazala  izuzetne  elektrokatalitičke  osobine  u  pogledu  elektrohemijskeredoks  reakcije  H₂O₂ u  poređenju  sa  nemodifikovanom  CPE  u  fosfatnom  puferu  (0,1 mol  L -1 ;pH 7,50),  a  takođe  i  u  acetatnom  puferu  (0,1  mol  L -1 ;  pH  4,50)  kao   pomoćnim  elektrolitima. Prilikom  amperometrijskog  određivanja  H ₂O₂ primenom  Pt-C/CPE  u  model  sistemima, zadovoljavajuća linearnost je postignuta u koncentracionom opseguH₂O₂od 0,15 do 1,45 µg mL -1 ,dok su vrednosti GO iznosile 0,06 µg mL -1 (pH 7,50, radni potencijal 0,20 V) i 0,10 µg mL -1 (pH4,50,  radni  potencijal  0,50  V).  Optimizovane  analitičke  metode  su  primenjene  za  određivanje sadržaja H ₂O₂ u komercijalno dostupnim proizvodima za ličnu negu: rastvoru za dezinfekciju (pH 7,50)  i  rastvoru  za  čišćenje  kontaktnih  sočiva  (pH  4,50).  Amperometrijski  dobijeni  rezultati  su  u dobrom  slaganju  sa  rezultatima  dobijenim  primenom  tradicionalne  spektrofotometrijske  metode bazirane  na  titanijum-sulfatu  kao  reagensu  sa  određenim  koncentracijama  2,91%  i  2,94%  zadezinfekcioni rastvor i 3,04% i 3,17% za rastvor zakontaktna sočiva, redom. RSD je bila manja od 2%.  Postignuti  rezultati  su  u  dobrom  slaganju  sa  sadržajem  H₂O₂ deklarisanim  od  strane proizvođača (3%) u oba ispitivana uzorka. Pt-C/CPE je takođe testirana za praćenje koncentracije H₂O₂ u rastvoru za kontaktna sočiva u toku procesa njegove neutralizacije/razgradnje. Nakon 6 h procesa neutralizacije, 24,68  µg mL -1 je bila određena koncentracija H ₂O_{2 ,} što je ispod dozvoljeneH₂O₂ koncentracije u rastvoru za kontaktna sočiva imajući u vidu granicu koja izaziva iritaciju oka. CPE  je  površinski  modifikovana  višezidnim  ugljeničnim  nanocevima  (MWCNT)  i kompozitima MnO 2 -MWCNT ili Pt-MWCNT metodom nanošenja kapi radi pripreme jednostavnih, osetljivih i pouzdanih voltametrijskih senzora za  određivanje H ₂O₂ u odabranom uzorku. Rezultati SEM/EDS  analize  kompozitnih  materijala  su  potvrdili da  su  medijatori,  čestice  MnO 2 i  Pt, nasumično  raspoređeni na površini MWCNT i zastupljeni sa blizu 5% (m:m) u kompozitu izraženopreko Mn i Pt. CV merenja su vršena sa pripremljenim radnim elektrodama u acetatnom (pH 4,50), fosfatnom  (pH  7,50)  i  boratnom  (pH  9,18)  puferu  kako  bi  se  okarakterisalo  osnovno elektrohemijsko  ponašanje  H ₂O₂ i  odabrali  pogodni  radni  potencijali  za  amperometrijsko određivanje ovog ciljnog analita. Pt- WCNT/CPE je primenljiva za rad kako u fosfatnom puferu pH  7,50  tako  i  u  acetatnom  puferu  pH  4,50  V  kako  pri  negativnim  tako  i  pri  pozitivnim  radnimpotencijalima, pri  čemu su vrednosti RSD uglavnom ispod 2,5%. U slučaju MnO 2-MWCNT/CPE, na  potencijalu  0,30  V  i  višim  vrednostima,  oksidacioni  signali  H₂O₂ su  signifikantni  u  blago alkalnoj sredini (pH 7,50), pri pH 4,50 ova elektroda pokazuje nezadovoljavajuće ponašanje, dok  pri pH 9,18 ima prihvatljive performanse. Granice određivanja (GO) su bile u oblasti µg mL -1 . H ₂O₂ je  određen  u  spajkovanom  uzorku  mleka  metodom  standardnog  dodatka  nakon  odgovarajuće pripreme  uzorka  (pH  podešavanje  i  centrifugiranje)  i  primenom  optimizovane  amperometrijske procedure (acetatni pufer pH 4,50, radni  potencijal-0,75 V) koristeći Pt-MWCNT/CPE kao radnu elektrodu. RSD za tri  ponovljena merenja je iznosila 2,5%, dok je prinos metode bio nešto veći od 71%.Kompozitni materijali koji se sastoje od MWCNT i  čestica na bazi Pd (Pd-MWCNT) ili Pt (Pt-MWCNT) su primenjeni za pripremu zapreminski modifikovanih SPCE (Pd-MWCNT-SPCE i Pt-MWCNT-SPCE)  i  površinski  modifikovane  SPCE  (Pd-MWCNT/SPCE).  Ove  elektrode,  kao  i nemodifikovana  SPCE  i  MWCNT-SPCE,  su  okarakterisane primenom  CV  i  amperometrije  u fosfatnom puferu pH 7,50 radi određivanja H ₂O₂ . Pd-MWCNT-SPCE i Pd-MWCNT/SPCE su se pokazale  pogodnim  za  određivanje  H ₂O₂ na  radnim  potencijalima  između  -0,50  i  0,50  V,  a  PtMWCNT-SPCE na ispitivanim radnim potencijalima od -0,80 do 0,70 V. Ove  elektrode su zatim modifikovane  enzimom  glukoza  oksidazom  (GOx)  metodom  nanošenja  kapi  rastvora  GOx  i Nafion ® -a  na  njihovu  površinu,  pri  čemu  je  optimizovana  količina  nanetog  biofilma.  GOx/PdMWCNT-SPCE  je  pokazala  bolje  analitičke  performanse  za  određivanje  glukoze  u  poređenju  sa GOx/Pd- WCNT/SPCE.  Kao  optimalan  radni  potencijal  GOx/Pd-MWCNT-SPCE  je  odabranavrednost  potencijala  -0,40  V  u  odnosu  na  ZKE,  sa  zadovoljavajućom  linearnošću  u  ispitivanom opsegu  koncentracija  glukoze  od  0,16  do  0,97  mmol  L -1 (od  29,1  do  174  µg  mL -1),  dok  je  GO iznosila 0,14 mmol L -1 (25 µg mL-1 ). Optimizovana metoda zasnovana na GOx/Pd-MWCNT-SPCE je  uspešno  primenjena  za  određivanje  glukoze  u  uzorku  livadskog  meda.  Dobijeni  rezultati  su  u dobroj  saglasnosti  sa  onima  dobijenim  primenom  komercijalno  dostupnog  aparata  za  merenje glukoze. Pogodan radni potencijal za GOx/Pt-MWCNT-SPCE je bio -0,50 V u odnosu na ZKE, pri čemu je zadovoljavajuća linearnost postignuta u ispitivanom opsegu koncentracija glukoze od 65,8 do 260,6 µg mL -1 , sa GO 35 µg mL -1 . Optimizovana metoda zasnovana na GOx/Pt-MWCNT-SPCE je  uspešno  primenjena  za  određivanje  glukoze  u  u  uzorku  belog  grožđa  i  uzorku  tableta (Traubenzucker-bonbons),  pri  čemu  su  dobijeni  rezultati  u  dobroj  saglasnosti  sa  rezultatima dobijenim primenom Accu-Chek aparata.Na  osnovu  dobijenih  rezultata  može  se  zaključiti  da  su  razvijene  analitičke  metode  pre svega jednostavne, pouzdane i pogodne za dobijanje brzih informacija o sadržaju H ₂O₂ u različitim tipovima  uzoraka.  Svakako  odabir  pogodne  radne  elektrode,  kao  i  optimizacija  eksperimentalnih uslova su ključni faktori za uspešno određivanje H ₂O₂
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The aim of this doctoral dissertation was the development of fast and reliable voltammetric methods  based  on  the  application  of  simple  and  contemporary  electrodes/sensors  based  on carbonaceous materials (carbon paste made of graphite powder and paraffin oil and screen printed carbon electrodes) for the determination of H  ₂ O₂ in the selected complex model and real samples.For this purpose, applicability of different working electrodes was investigated.The  amperometric  method  based  on  carbon  paste  electrode  (CPE)  bulk- modified     with 5% (m:m) MnO 2 , under optimized conditions, with a working potential of 0.40 V vs. the saturated calomel  elect rode  (SCE)  and  a  phosphate  buffer  solution  (pH  7.50)  as  supporting  electrolyte, enabled the quantitation of H  ₂ O₂in the concentration interval from 1.4 to 65 µg mL −1 with a relative standard deviation (RSD) of less than 10%. This meth od was applied for the determination of the H ₂ O₂ consumption  in  samples  of  groundwater  fro m  the  Central  Banat  region  (Province  of Vojvodina, Serbia) treated by the Fenton (Fe ²⁺ and H ₂O₂ ) and Fenton-  like (Fe ³⁺and H ₂O₂ ) reagents to remove natural organic matter (NOM) at  differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H₂O₂ . It was found that the form of Fe (Fe ²⁺ or Fe ³⁺ )and the molar  ratio to H ₂O₂influenced the degree of the H ₂O₂ decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe ³⁺ and H  ₂ O₂, a sign ificant amount of H  ₂ O₂ remained unused, whi ch also indicates a lower efficiency of such system compared to the Fenton process. Screen  printed  carbon  electrode  (SPCE)  bulk-modified  with  MnO  ₂ as  a  mediator  was applied  for  amperometric  determination  of  the  H  ₂ O₂ content  during  the  Fenton  (Fe ²⁺ ,  H  ₂ O₂ )  and  visible  light-assisted ,  photo-Fenton  (Fe ²⁺  ,  H  ₂ O₂ ,  hν)   based  removal  of  neonicotinoid  insecticide acetamiprid (ACT). Under  optimized conditions (working potential of 0.40 V vs. SCE, phosphate buffer  pH  7.50  as  supporting  electrolyte)  amperometric  determination  of  H  ₂ O₂ showed  a  linear dynamic range from 0.01 to 1.24 mmol L -1 (from 0.34 to 42.2 µg mL -1) and the RSD did not exceed 4.2%. In the investigated samples (after appropriate pH adjustment from 2.8 to 7.5 instantly after the sampling  to stop or maximum decelerate the oxidation processes, filtering, and storage of the deep- frozen sample with defrosting immediately before the measurements) the H  ₂ O₂  contents were determined by the standard addition method by analyzing the corresponding amperometric curves. Parallel HPLC-DAD measurements were performed to monito r the concentration/removal of ACT. In the case of the photo- Fenton process (initial concentrations: 0.31; 2.0 and 3.0 mmol L -1 (70.0; 111.7 and 102.1 µg mL -1 ) of ACT, Fe ²⁺ and H  ₂ O₂, respec tively) after 10 min of irradiation H  ₂ O₂ was  consumed  and  it  can  be  consi dered  that  ACT  was  removed  after  5  min.  During  the  Fenton process ACT was removed after 20 min of treatment and around 10% of the initial concentration of the H 2O2 remained still unused.CPE  was  surface  modified  with  a  composite  of  Pt  nanoparticles  (<  5  nm)  on  graphitized carbon (Pt-C, 10% Pt on Vulcan XC72) by simply dropcoating method. The unmodified CPE and the  modified  one  (Pt-C/CPE)  were  characterized  by   EM/EDS  and  CV  measurements.  The  PtC/CPE showed remarkable electrocatalytic propertiestoward the electrochemical redox reaction of H ₂ O₂ compared to  modified CPE in phosphate buffer (0.1 mol L -1 ; pH 7.50), as well in acetatebuffer  (0.1 mol  L -1 ; pH .50) supporting  electrolytes. Amperometry of  H2O2 in the concentration range from 0.15 to 1.45 µg mL -1 with the Pt-C/CPE showed acceptable linearity, while the obtained values of LOQs were 0.06 µg mL -1  (pH 7.50, working potential 0.20 V) and 0.10 µg mL -1 (pH 4 .50, working potential 0.50 V). The proposed analytical  methods were applied to the determination of the H 2O2 content in commercially available personal care products; i.e., disinfection (pH 7.50) and contact lens cleaning solutions (pH 4.50). The obtained amperometric results are in good agreement with those measured by traditional titanium sulfatereagent based spectrophotometric method with determined concentrations as 2.91% and 2.94%  for the disinfection product, and 3.04% and 3.17% for the contact lens solution, respectively. RSD was lower than 2%. The obtained results are in a good agreement with the amounts of the H  ₂ O₂ declared by producers (3%) in the both investigated samples. The Pt-C/CPE was also tested for monitoring of the H  ₂ O₂ residual concentration in contact lens  solution  during  its  neutralization/decomposition  rocess.  At  6  h  of   neutralization  treatment 24.68 µg mL -1 of the H  ₂ O₂ was  determined which is almost half of the allowedH2 O2 concentration in the case of the contact lens solution concerningthe limit of eye irritation. CPE  was  surface   modified  with  multiwalled  carbon  nanotubes  (MWCNT)  and  with composites of MnO ₂ -MWCNT or Pt-MWCNT by drop coating method to prepare simply, sensitive and reliable volta mmetric sensors for the determination of H  ₂ O₂ in selected sample. The results of the  SEM/ EDS  analysis  of  composite  materials  have  confirmed  that  the  mediators,  MnO ₂ and  Pt  articles, are randomly distributed on the surface of MWCNT and represent nearly 5% (m:m) of the composite expressed as Mn and Pt. CV measurements were performed  with prepared electrodes in acetate  (pH  4.50),  phosphate  (pH  7.50)  and  borate  (pH  9.18)  buffers  to  characterize  the  basic electrochemical  behavior  of  H  ₂ O₂ and  to  select  the  working  potentials  suitable  for  amperometric determination  of  this  target  analyte.  The  Pt-MWCNT/CPE  performs  well  in  phosphate  buffer pH .50 and acetate buffer solution pH 4.50 in the  negative as well as in the positive polarization range with RSD mainly lower than 2.5%. In case of MnO ₂ -MWCNT/CPE at  0.30 V and above the H ₂ O₂ oxidation signal is rem arkable in slightly alkaline media (pH 7.50), at pH 4.50 this electrode showed poor behavior and at pH 9.18 offered acceptable performance. LOQs were in the µg mL -1 concentration  range.  H ₂ O₂ was  determined  in  a  spiked  milk  sample  by  standard addition  method after  appropriate  sample  preparation  (pH  adjustment and  centrifugation)  and  using  optimized amperometric p rocedure (acetate buffer pH 4.50, working potential -0.75 V) by Pt-MWCNT/CPE as a working electrode. RSD for three repeated measurements was 2.5%, while the recovery of the method was a bit higher than 71%. The  composite  materials  consisting  of  MWCNT  and  Pd  (Pd-MWCNT)  or  Pt  containing particles  (Pt-WCNT)  were  applied  to  the  preparation  of  bulk- modified  SPCEs  (Pd-MWCNTSPCE and Pt-MWCNT-SPCE) and surface modifiedSPCE (Pd- MWCNT/SPCE). These electrodes, as well as unmodified SPCE and MWCNT-SPCE,  were characterized by CV and  amperometry  in phosphate  buffer  solution  of  pH  7.50  for  the  H  ₂ O₂ determination.  Pd-MWCNT-SPCE  and  PdMWCNT/SPCEare convenient for the etermination of H 2O2 at working potentials from -0.50 to 0.50 V, and Pt-MWCNT-SPCE at investigated working potentials in the range from -0.80 to 0.70 V. These electrodes were then modified with glucose  oxidase (GOx) by drop coating a solution of GOxand Nafion ® on their surface, whereby the applied amount of biococktail was optimized. GOx/PdMWCNT-SPCE  showed  better  analytical  performance  for  glucose  determination  in  comparison with  GOx/Pd-MWCNT/SPCE.  The  optimal  working  potential  for  GOx/Pd-MWCNT- SPCE  was -0.40 V vs. SCE and  satisfactory linearity was obtained in the investigated glucose concentration range from 0.16 to 0.97 mmol L -1 (from 29.1 to 174  µg mL -1 ), hile the LOQ was 0.14 mmol L -1 (25 µg mL -1 ). The optimized method based on GOx/Pd-MWCNT-SPCE was successfully applied to the determination of glucose in multifloral honey sample.  The results are in a good agreement with those  obtained by commercially available equipment for determination of glucose. Optimal working potential  for  GOx/Pt-MWCNT-SPCE  was  -0.50  V  vs.  SCE,  and  the   satisfactory  linearity  was obtained in the investigated concentration range ofglucose from 65.8 to 260.6  µg mL -1 , with LOQ of 35  µg mL -1 . The optimized method based on GOx/Pt- MWCNT-SPCE was successfully applied for determination of glucose in white grape and glucose tablets (Traubenzucker-bonbons) samples, whereby  the  obtained  results  were  in  a  good  agreement  with  the  results  obtained  by  Accu-Chek device. Based on the results, the developed analytical methods are first of all simple, reliable and suitable  for  obtaining  fast  information  about  the  content  of  H ₂O₂ in  different  types  of  samples. Certainly the selection of a suitable working electrode, as well as the optimization of experimental conditions are key factors for the successful determination of H₂O₂ .

碩士
國立臺中教育大學
科學應用與推廣學系科學教育碩士班
100
The research aimed to investigate dye degradation using the advanced oxidation treatments, including Fenton, Photo-Fenton, Photo-Fenton-like, and Fenton-like systems. There were eight homogeneous catalytic experiments containing the interactions between two types of dyes, Acid Blue 1 (AB1) and Ethyl Violet (EV), and four oxidation treatments. These methods apply the homogeneous catalytic experiments which yield powerful oxidization to degrade various types of dyes. The purpose is to evaluate the ability of degradation of AB1 and EV and assess the effects of different levels of reagent concentration and pH ratio from these four oxidation treatments respectively. In addition, the HPLC–PDA-ESI-MS is applied to separating and identifying the impact of ABI and EV on the degradation of generated intermediates. As a result, the possible degradation pathways can be inferred and argued in order to provide a stylized fact for the industrial dye wastewater. The experimental results are shown as follows. (1) The optimum AB1 degradation are 0.5mM FeSO4 and 10m MH2O2 during Photo-Fenton and Fenton; and 2mM Fe(NO3)3 and160m MH2O2 during Photo-Fenton-like and Fenton-like. (2) The optimum EV degradation are 0.5mM FeSO4 and 5mM H2O2 during Photo-Fenton and Fenton; and 2mM Fe(NO3)3 and 160mM H2O2 during Photo-Fenton-like and Fenton-like. (3) The optimum pH is about 3 regardless of different oxidation treatments. Regardless of AB1 or EV in the Photo-Fenton, Fenton (Photo-Fenton-like, Fenton-like), requiring very high wattage 254nm UV irradiation effect, can be significantly presentedin the light. Generally speaking, the degradationexperiments show that Photo-Fenton and Fenton treatments are more efficient than the Photo-Fenton-like and Fenton-like. This research also utilizes the HPLC–PDA-ESI-MS for separating and identifying the impact of AB1 and EV in order to uncover the dye degradationpathways. The intermediates are generated by the degradation of AB1 and EV under Photo-Fenton. However, the AB1 with a very small amount of oxidant (H2O2) efficiently accelerates the degradation, leading to rapid Benzene ring-opening reactions, such that few intermediates are found. In addition, the results indicate that the probable degradation pathways are Dealkylation and Hydroxy-lation of chromophore, and cleavage of the conjugated chromophore structure. The findings provide the fundamental applications of photocatalyst to dye degradation.

碩士
東海大學
環境科學與工程學系
105
Copper(II) sulfide photocatalysts were successfully synthesized by hydrothermal method from the solution of CuCl2·2H2O and Na2S·9H2O at 130°C, with cetyltrimethyl ammonium bromide (CTAB) as a reducing agent, and the synthetic parameters such as reaction time (24 h, 48 h and 72 h) and molar ratio of copper-to-sulfur (1:6, 1:8 and 1:10). The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis diffuse reflectance (UV-DR) spectroscopy. The XRD peaks were indexed to the pattern of hexagonal phase of CuS and crystallite size were 25.89-38.40 nm. The particles size ranged from 250 to 500 nm. Energy band-gap was in range of 1.88–2.04 eV. The more complex structures (plate, rope-like and hierarchical structure) were obtained with increased sulfur content and reaction times. The photocatalytic activity was evaluated observing degradation of paraquat solution under visible light. The results showed that 100 % removal within 240 min was obtained for solution containing an initial concentration of 40 mg/L paraquat. CuS has better photocatalytic performance then the commercial TiO2 P25 in the presence of H2O2. CuS achieved an optimal photocatalytic performance when Cu:S equal 1:8 via hydrothermal treatment for 72 h, and followed a pseudo-first order with an observed rate constant (kobs) of 2.0×10^-2 /min and an initial reaction rate (r0) of 0.251×10^-2 mM/min. The photocatalytic degradation of paraquat kinetic model fit well with the Langmuir-Hinshelwood adsorption equilibrium constant (Ka) of 10.34 /mM and the surface reaction rate constant (kr) of 2.5×10^-3 /min expressed by Langmuir–Hinshelwood rate law. The presence of H2O2 in heterogeneous photo-Fenton-like system improved the photocatalytic activity due to overcomes the charge recombination in CuS when H2O2 as an electron acceptor and generates more hydroxyl radicals. It has two ways to decompose paraquat. One is direct decomposition via redox reactions from electron-hole pairs on the CuS surface. Another one is indirect decomposition by hydroxyl radicals (OH‧) in surroundings solution.

Industrialization and modernization in recent times have led to a water crisis across the world. Conventional methods of water treatment like physical, chemical and biological methods which comprise of many commonly used techniques like membrane separation, adsorption, chemical treatment etc. have been in use for many decades. However, problems like sludge disposal, high operating costs etc. have led to increased focus on Advanced Oxidation Processes (AOPs) as alternative treatment methods. AOPs basically involve reactions relying on the high oxidation potential of the hydroxyl (OH•) free radical. They have the potential to efficiently treat various toxic, organic pollutants and complete degradation of contaminants (mineralization) of emerging concern. Many different types of homogenous as well as heterogenous AOPs have been studied viz: UV/H2O2, Fenton, Photo-Fenton, Sonolysis, Photocatalysis etc. for treatment of a wide variety of organic pollutants. Different AOPs are suitable for different types of wastewater and hence proper selection of the right technique for a particular type of pollutant is required. The inherent advantages offered by AOPs like elimination of sludge disposal problems, operability under mild conditions, ability to harness sunlight, non selective nature (ability to degrade all organic and microbial contamination) etc. have made it one of the most actively researched areas in recent times for wastewater treatment. Despite the benefits and intense research, commercial applicability of AOPs as a practical technique for treating wastewater on a large scale is still far from satisfactory. Nevertheless, positive results in lab scale and pilot plant studies make them a promising water treatment technique for the future. In the present chapter, an attempt has been made to discuss all aspects of AOPs beginning with the fundamental concepts, classification, underlying mechanism, comparison, commercialization to the latest developments in AOPs.

Industrialization and modernization in recent times have led to a water crisis across the world. Conventional methods of water treatment like physical, chemical and biological methods which comprise of many commonly used techniques like membrane separation, adsorption, chemical treatment etc. have been in use for many decades. However, problems like sludge disposal, high operating costs etc. have led to increased focus on Advanced Oxidation Processes (AOPs) as alternative treatment methods. AOPs basically involve reactions relying on the high oxidation potential of the hydroxyl (OH•) free radical. They have the potential to efficiently treat various toxic, organic pollutants and complete degradation of contaminants (mineralization) of emerging concern. Many different types of homogenous as well as heterogenous AOPs have been studied viz: UV/H2O2, Fenton, Photo-Fenton, Sonolysis, Photocatalysis etc. for treatment of a wide variety of organic pollutants. Different AOPs are suitable for different types of wastewater and hence proper selection of the right technique for a particular type of pollutant is required. The inherent advantages offered by AOPs like elimination of sludge disposal problems, operability under mild conditions, ability to harness sunlight, non selective nature (ability to degrade all organic and microbial contamination) etc. have made it one of the most actively researched areas in recent times for wastewater treatment. Despite the benefits and intense research, commercial applicability of AOPs as a practical technique for treating wastewater on a large scale is still far from satisfactory. Nevertheless, positive results in lab scale and pilot plant studies make them a promising water treatment technique for the future. In the present chapter, an attempt has been made to discuss all aspects of AOPs beginning with the fundamental concepts, classification, underlying mechanism, comparison, commercialization to the latest developments in AOPs.