WO2008077191A1 - Improved water analysis - Google Patents
Improved water analysis Download PDFInfo
- Publication number
- WO2008077191A1 WO2008077191A1 PCT/AU2007/001987 AU2007001987W WO2008077191A1 WO 2008077191 A1 WO2008077191 A1 WO 2008077191A1 AU 2007001987 W AU2007001987 W AU 2007001987W WO 2008077191 A1 WO2008077191 A1 WO 2008077191A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- electrode
- sample
- cod
- working electrode
- light source
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
- G01N33/1806—Water biological or chemical oxygen demand (BOD or COD)
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
Definitions
- This invention relates to a new method for determining oxygen demand of water using photoelectrochemical cells.
- the invention relates to an improved direct photoelectrochemical method of determining chemical oxygen demand of water samples using a titanium dioxide nanoparticulate semiconductive electrode. It is particularly adapted to a use in a probe configuration
- Oxygen demand assay based on photoelectrochemical degradation principles has been previously disclosed in patent specification WO2004088305 where the measurement was based on exhaustive degradation principles. It is an object of the present invention to develop an analyzer based on non- exhaustive degradation principles. It is another object of this invention to develop a probe type COD analyzer.
- the present invention provides a method of determining chemical oxygen demand (COD) of a water sample, comprising the steps of a) applying a constant potential bias to a photoelectrochemical cell, having a photoactive working electrode and a counter electrode, and containing a supporting electrolyte solution; b) illuminating the working electrode with a light source and recording the background photocurrent produced at the working electrode from the supporting electrolyte solution; c) adding a water sample, to be analysed, to the photoelectrochemical cell; d) illuminating the working electrode with a light source and recording the steady state photocurrent produced with the sample; e) determining the chemical oxygen demand of the water sample using the formula
- the intensity of the light on the photoelectrode influences the linear range of the instrument. However increasing light intensity to too high a value can lead to stability problems with the instrument either emanating from the light source or from photo corrosion of the electrode.
- a preferred light intensity is within the range of 3 to 10 W/cm 2 with a value of 6 to 7 W/cm 2 being preferred.
- Solution pH also affects the signal and an operational pH range of 3 to 10 is preferred.
- the working electrodes may be regenerated by exposure to UV light and have a useful working life.
- the counter electrode it is preferred to also use a reference electrode.
- this invention provides a probe for determining water quality comprising a) an electrochemical cell containing a photoactive working electrode, a counter electrode and optionally a reference electrode b) a supporting electrolyte solution chamber; c) a light source to illuminate the working electrode d) sample collection means to provide a volume of sample to the cell e) control means to i) actuate the light source and record the background photocurrent produced at the working electrode from the supporting electrolyte solution; ii) add a water sample, to be analysed, to the photoelectrochemical cell; iii) actuate the light source and record the steady state photocurrent produced with the sample; iv) determine the chemical oxygen demand of the water sample using the formula
- ⁇ is the Nernst diffusion layer thickness
- D is the diffusion coefficient
- A is the electrode area
- F the Faraday constant
- i ss the steady state photocurrent
- Figure 1 is a schematic view of the photoelectrochemical cell used in this invention.
- Figure 2 is a graph of a typical photocurrent response of 0.1 M NaCIO 4 blank solution
- Figure 3A shows the quantitative relationship between the net steady state current
- Figure 3B shows the quantitative relation between the net steady state current (in mA) and nFADC;
- Figure 4A shows the plot of the theoretical and experimental / ss against the theoretical COD values of KHP solution;
- Figure 4 B shows the plot of experimental / ss against the theoretical COD values of KHP and GGA solutions;
- Figure 5A shows the photoelectrochemical oxidation of glucose under different UV light intensities
- Figure 5B shows the effect of potential on / ss ( ⁇ ) and ibiank(o) due to the photoelectrochemical oxidation of 0.2 mM glucose and its blank solution, respectively;
- Figure 5 C shows the effect of pH on / ss ( ⁇ ) and i b ian k (o) due to the photoelectrochemical oxidation of 0.2 mM glucose and its blank solution, respectively;
- Figure 6 shows typical GGA standard addition for the determination of the wastewater from a bakery;
- Figure 7 shows the correlation between the PECOD and the standard dichromate COD methods for the real sample measurements.
- ITO Indium Tin Oxide
- SiO Indium Tin Oxide
- TiO titanium butoxide
- sodium nitrate purchased from Aldrich without further treatment prior to use. All other chemicals were of analytical grade and purchased from Aldrich unless otherwise stated.
- High purity deionised water (Millipore Corp., 18M ⁇ cm) was used in the preparation of solutions and the dilution of real wastewater samples.
- the real samples used in this study were collected within the State of Queensland in Australia from various industrial sites including wastewater treatment plants, sugar plants, brewery manufacturers, cannery manufacturers and dairy production plants. All samples were preserved according to the guidelines of the standard method. When necessary, the samples were diluted to a suitable concentration prior to the analysis. After dilution, the same sample was subject to analysis by both standard COD method and photoelectrochemical COD detector. To the samples for photoelectrochemical determination, NaCIO 4 solid equivalent to 0.1 M was added as supporting electrolyte.
- the light beam was passed through a UV-band pass filters, i.e. UG5 (Avotronics Pty. Limited), prior to illuminating the electrode surface.
- Standard COD values dichromate method
- COD analyzer NOVA 30, Merck
- the oxygen concentration was monitored by an oxygen electrode (YSI) and 90 FLMV Microprocessor Field Analyser (from T.P.S. Pty. Ltd.).
- Figures 2A and B show a set of typical photocurrent-time profiles obtained in the presence and absence of organic compounds in the photoelectrochemical cell.
- the dark current was approximately zero.
- the current increased rapidly before decaying to a steady value.
- the photocurrent ⁇ hian k resulted mainly from the oxidation of water
- photocurrent (i tota i) observed from the sample solution containing organics solid line
- photocurrent (ki a n k ) is the total current of two current components, one from the oxidation of water, which was the same as the blank photocurrent (ki a n k ), and the other from photoelectrocatalytic oxidation of organic compounds.
- the current / ss the diffusion limiting current originated from the oxidation of organics, can be obtained by subtracting the photocurrent of the blank ⁇ ibiank) in the absence of organic compounds from the total photocurrent in the presence of organic compounds (see Figure 1.2).
- i ss i m ⁇ l - W (1.1)
- the net current (i ss ) is directly proportional to the rate of electron transfer (the number of electrons transferred per unit of time).
- COD is defined as the amount of oxygen required for complete oxidation of organic compounds, subsequently, the net current (i ss ) can be used to quantify the COD value of a sample.
- the rate of steady state mass transfer (dN/dt) to the electrode can be given by a well-known semi-empirical treatment of Steady-State Mass Transfer model: where, C b and C 3 refer to the concentrations of analyte in the bulk solution and at the electrode surface respectively. D and ⁇ are the diffusion coefficient and the Nemst diffusion layer thickness respectively.
- Equation 1.4 defines the quantitative relationship between the steady-state photocurrent and the concentration of analyte. Converting the molar concentration into the equivalent COD concentration (mg/L of O 2 ), we have:
- Equation 1.5b is valid for the determination of COD in a sample which contains a single organic compound.
- the COD of a sample containing more than one organic species can be represented as:
- ⁇ is the collective Nernst diffusion layer thickness, which has been proved to be a constant and independent of the type of organics, under diffusion controlled conditions
- D is the composite diffusion coefficient that depends on the sample composition and is a constant for a given sample.
- Equation 1.6 should be valid under the same conditions, as required by Equation 1.4.
- Figures 4A and 4B show the plot of i ss against the theoretical COD value of the synthetic samples ([COD] t he or et ical) prepared with KHP, a test compound for the standard COD method.
- Equation 1.5 a linear relationship between i ss and [COD] t heoreticai was obtained.
- Equation 1.6 The applicability of Equation 1.6 was examined using a GGA synthetic sample.
- the GGA synthetic sample is a mixture of glucose and glutamic acid, which has typically has been used as a standard test solution for BOD analysis.
- Equation 1.6 the steady-state photocurrent, i ss , is directly proportional to the sample [COD] (see Figure 1.4b).
- D composite diffusion coefficient
- a COD calibration standard can only be selected by experimental means. Two essential criteria should be satisfied by the selected calibration standard: (i) the calibration standard should possess an equiivalent D value to the original sample and (ii), it can be fully oxidized. These criteria reflect the experimental observation that the added calibration standard causes a steady-state photocurrent change which follows the same slope of the original sample.
- the applied potential bias serves the function of collecting the electrons made available by the interfacial photocatalytic reactions. 100% photoelectron collection efficiency (Postulate (iv) - see Analytical Signal Quantification section) can be achieved only when the applied potential bias is sufficient.
- Figure 5B shows the effect of potential bias on both i ss and i blank . It reveals that both / ss and kian k becomes constant when the applied potential bias is more positive than -0.05V vs Ag/AgCI indicating 100% photoelectron collection efficiency.
- a standard potential bias of +0.30V vs Ag/AgCI was selected.
- a solution pH range from 3 to 10 is preferred. This pH range is suitable for most of the environmental samples (pH 3-10) that can be used without the needs for pH adjustment.
- Figure 7 shows the correlation between the experimental COD values and standard COD values.
- the standard COD value was determined with the conventional COD method (dichromate method). Where valid, the Pearson Correlation coefficient was used as a measure of the intensity of association between the values obtained from the photoelectrochemical COD method and the conventional COD method.
- the slope of the graph was 1.02. This near unity slope indicates that both methods were accurately measuring the same COD value. Given a 95% confidence interval, this slope was between 0.96 and 1.11 , which implies a 95% confidence level that the true slope lies between these two values.
- this invention provides an improved method and a probe for use in conducting non-exhaustive COD analyses of water samples.
- Those skilled in the art will realize that this invention may be implemented in embodiments other than those described without departing from the core teachings of the invention.
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002672645A CA2672645A1 (en) | 2006-12-22 | 2007-12-21 | Improved water analysis |
AU2007336706A AU2007336706B2 (en) | 2006-12-22 | 2007-12-21 | Improved water analysis |
US12/520,227 US20110073495A1 (en) | 2006-12-22 | 2007-12-21 | Water analysis |
EP07845425A EP2095108A1 (en) | 2006-12-22 | 2007-12-21 | Improved water analysis |
BRPI0721046-9A BRPI0721046A2 (en) | 2006-12-22 | 2007-12-21 | IMPROVED WATER ANALYSIS |
JP2009541696A JP2010513874A (en) | 2006-12-22 | 2007-12-21 | Improved water quality analysis |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2006907134 | 2006-12-22 | ||
AU2006907134A AU2006907134A0 (en) | 2006-12-22 | Improved water Analysis | |
AU200607134 | 2006-12-22 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2008077191A1 true WO2008077191A1 (en) | 2008-07-03 |
WO2008077191A8 WO2008077191A8 (en) | 2009-12-03 |
Family
ID=39562033
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/AU2007/001987 WO2008077191A1 (en) | 2006-12-22 | 2007-12-21 | Improved water analysis |
Country Status (10)
Country | Link |
---|---|
EP (1) | EP2095108A1 (en) |
JP (1) | JP2010513874A (en) |
KR (1) | KR20090101188A (en) |
CN (1) | CN101563602A (en) |
AU (1) | AU2007336706B2 (en) |
BR (1) | BRPI0721046A2 (en) |
CA (1) | CA2672645A1 (en) |
TW (1) | TW200842354A (en) |
WO (1) | WO2008077191A1 (en) |
ZA (1) | ZA200904290B (en) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102331447A (en) * | 2011-04-27 | 2012-01-25 | 河北先河环保科技股份有限公司 | Method and equipment for measuring chemical oxygen demand by photocatalytic oxidation process |
RU2555774C2 (en) * | 2013-11-28 | 2015-07-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Омский государственный университет им. Ф.М. Достоевского" | Water state indication method |
TWM496760U (en) * | 2014-11-05 | 2015-03-01 | Univ Chaoyang Technology | Chemical oxygen demand inspection device |
KR101639616B1 (en) * | 2014-12-15 | 2016-07-15 | 한국기계연구원 | Photo-electorde for tandem structure photoelectrochemical cell comprising metal ultra-thin layer and photoelectrochemical cell comprising the same |
CN105044180B (en) * | 2015-06-29 | 2017-11-17 | 江苏大学 | A kind of preparation method and purposes of heterojunction photovoltaic pole |
CN105116040B (en) * | 2015-08-25 | 2018-05-08 | 广西壮族自治区农业科学院农产品质量安全与检测技术研究所 | Optical electro-chemistry reaction tank |
CN105203527B (en) * | 2015-09-11 | 2018-03-23 | 山东师范大学 | The optical electro-chemistry detection means and its application method of a kind of double detection cells |
CN106970131B (en) * | 2017-03-28 | 2019-01-18 | 北京北大明德科技发展有限公司 | A kind of photoelectrocatalysis type water-soluble organic compound concentration sensor and preparation method |
CN108845004B (en) * | 2018-06-15 | 2020-10-13 | 浙江大学 | Photocurrent carbon dioxide sensor |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2004088305A1 (en) * | 2003-04-04 | 2004-10-14 | Aqua Diagnostic Pty Ltd | Photoelectrochemical determination of chemical oxygen demand |
-
2007
- 2007-12-21 CA CA002672645A patent/CA2672645A1/en not_active Abandoned
- 2007-12-21 KR KR1020097012739A patent/KR20090101188A/en not_active Application Discontinuation
- 2007-12-21 WO PCT/AU2007/001987 patent/WO2008077191A1/en active Application Filing
- 2007-12-21 CN CNA2007800472316A patent/CN101563602A/en active Pending
- 2007-12-21 TW TW096149356A patent/TW200842354A/en unknown
- 2007-12-21 BR BRPI0721046-9A patent/BRPI0721046A2/en not_active IP Right Cessation
- 2007-12-21 AU AU2007336706A patent/AU2007336706B2/en not_active Ceased
- 2007-12-21 JP JP2009541696A patent/JP2010513874A/en active Pending
- 2007-12-21 EP EP07845425A patent/EP2095108A1/en not_active Withdrawn
-
2009
- 2009-06-18 ZA ZA200904290A patent/ZA200904290B/en unknown
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2004088305A1 (en) * | 2003-04-04 | 2004-10-14 | Aqua Diagnostic Pty Ltd | Photoelectrochemical determination of chemical oxygen demand |
Non-Patent Citations (1)
Title |
---|
HUIJUN ZHAO ET AL.: "DEVELOPMENT OF A DIRECT PHOTOELECTROCHEMICAL METHOD FOR DETERMINATION OF CHEMICAL OXYGEN DEMAND", ANALYTICAL CHEMISTRY, vol. 76, no. 1, 1 January 2004 (2004-01-01), pages 155 - 160, XP001047456 * |
Also Published As
Publication number | Publication date |
---|---|
EP2095108A1 (en) | 2009-09-02 |
BRPI0721046A2 (en) | 2014-07-29 |
WO2008077191A8 (en) | 2009-12-03 |
CN101563602A (en) | 2009-10-21 |
AU2007336706B2 (en) | 2010-09-02 |
CA2672645A1 (en) | 2008-07-03 |
ZA200904290B (en) | 2010-04-28 |
JP2010513874A (en) | 2010-04-30 |
TW200842354A (en) | 2008-11-01 |
KR20090101188A (en) | 2009-09-24 |
AU2007336706A1 (en) | 2008-07-03 |
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