Biosensor for the evaluation of biochemical oxygen demand using photocatalytic pretreatment (original) (raw)
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Development of photocatalytic biosensor for the evaluation of biochemical oxygen demand
Biosensors and Bioelectronics, 2005
The photocatalytic biosensor of flow system using semiconductor TiO 2 was developed to evaluate biochemical oxygen demand (BOD) levels in river water. Photocatalysis of sample was carried out in a photoreactor with TiO 2 and a 6 W black-light blue fluorescent tube as light source. Sample from a photoreactor outlet was measured by an oxygen electrode with a biofilm. The sensor response of photocatalytic biosensor was between 5 and 10 min depending on concentration of biochemical in the samples. At BOD of 1 mg l −1 , the sensor response increased 1.33-fold in comparison with that without photocatalysis. The degradation of tannic acid and humic acid with photocatalysis were 51.8 and 38.4%, respectively. Gum arabic and linear alkylbenzene sulfonate (LAS) were degraded a little, but gave the responses of more than double to the sensor. Free radicals yielded by photocatalysis in a photoreactor did not affect the sensor response because their lifetime is extremely short. Fairly good correlation (r = 0.983) between the sensor method and the conventional method was obtained for test samples. This biosensor using photocatalytic pretreatment improved the sensitivity.
Development of a Direct Photoelectrochemical Method for Determination of Chemical Oxygen Demand
Analytical Chemistry, 2004
A novel rapid methodology for the determination of chemical oxygen demand (COD) based on photoelectrochemical oxidative degradation principle (PECOD) was proposed and experimentally validated. With this new method, the extent of degradation of dissolved organic matter in a water sample is measured simply by directly quantifying the extent of electron transfer at a TiO 2 nanoporous film electrode during an exhaustive photoelectrocatalytic degradation of organic matter in a thin layer photoelectrochemical cell. The PECOD method demonstrated in this work is a direct and absolute method. It does not require the use of standard for calibration. The method, in principle, measures the theoretical COD value due to the extraordinary high oxidation efficiency and accuracy of charge measurement. This new approach overcomes many of the current problems associated with existing oxygen demand techniques (e.g., the matrix effect, one of the serious practical problems that most rapid COD methods suffered because of the insufficient oxidation efficiency). The PECOD method overcomes the matrix effect by employing a highly effective photoelectrochemical system that is capable of fully oxidizing a wide spectrum of organics in the water sample. The method was successfully applied to determine the COD of a range of synthetic and real samples. Excellent agreement with a standard dichromate method was achieved. The practical detection limit of 0.2 mg L-1 COD with the linear range of 0-200 mg L-1 was also achieved. The PECOD method is a method that is environmentally friendly, robust, rapid, and easily automated. It requires only 1-5 min to complete an assay and consumes very limited reagent (electrolyte only).
Rapid Determination Of Biochemical Oxygen Demand
2009
Biochemical Oxygen Demand (BOD) is a measure of the oxygen used in bacteria mediated oxidation of organic substances in water and wastewater. Theoretically an infinite time is required for complete biochemical oxidation of organic matter, but the measurement is made over 5-days at 20 0C or 3-days at 27 0C test period with or without dilution. Researchers have worked to further reduce the time of measurement. The objective of this paper is to review advancement made in BOD measurement primarily to minimize the time and negate the measurement difficulties. Survey of literature review in four such techniques namely BOD-BARTTM, Biosensors, Ferricyanidemediated approach, luminous bacterial immobilized chip method. Basic principle, method of determination, data validation and their advantage and disadvantages have been incorporated of each of the methods. In the BOD-BARTTM method the time lag is calculated for the system to change from oxidative to reductive state. BIOSENSORS are the biol...
Electrochemical Determination of Chemical Oxygen Demand Using Ti/TiO 2 Electrode
To overcome the shortcomings of the conventional potassium dichromate method (PDM) for monitoring chemical oxygen demand (COD) of waters, many efforts have been made on developing quick and environment-friendly techniques. Among all alternatives, electrochemical (EC) techniques are very competitive due to their relatively simple devices and quickness. A number of electrodes have been fabricated to investigate electrochemical determination of COD. However, little work has been reported on TiO 2 based electrode for this purpose. In the present work, Ti/TiO 2 electrode was simply prepared by anodic oxidation of pure titanium. Aqueous solutions of potassium hydrogen phthalate and phenol were electrolyzed by chronocoulometry in a three-electrode system with Ti/TiO 2 as working electrode (anode). Organic compounds were electrochemically oxidized on Ti/TiO 2 electrode by hydroxyl radicals and the released electrons were recorded and transferred to currents. The electric currents were proportional to the COD values of the water samples being investigated. Based on data of COD values and corresponding currents, a linear regression equation was obtained for a certain kind of waste water. With the regression equation, current of an unknown water sample was transferred to its COD value. Conditions for the presented EC method were set up as cell voltage 2.0V v.s. SCE and pH 7.0. The linear range of COD was of about 25~530 mg/L. COD values of real waste water samples were measured by Ti/TiO 2 electrode and the relative errors were all in the range of 8% compared with data determined by conventional PDM. The electrochemicalmethodology was successfully applied to evaluate COD in waste water..
2006
A COD measurement by a photocatalytic oxidation method using nano-TiO 2 film was investigated. K 2 Cr 2 O 7 was added into the solution to enhance the efficiency of photocatalytic degradation, and simultaneously K 2 Cr 2 O 7 was reduced to Cr(III) by photogenerated electrons, which were adsorbed on the surface of TiO 2. The measuring principle was based on direct determination of Cr(III) concentration which was proportional to the COD value. Under the optimized experiment condition, the application range was 20-500 mg l −1 , and the detection limit was 20 mg l −1. The immobilization of photocatalyst on the supports could not only solve the problem of low recovery of the catalyst and hard separation from the solution, but also overcome its shortcoming of poor stability. Applied this method to the determination of real samples, it was found to be rapid and environmentally friendly. Additionally, the method proposed above for determination of COD was in excellent correspondence with values obtained by using the conventional method.
Biosensors and Bioelectronics, 2007
The stopped-flow system with an ozonizer was developed to estimate low biochemical oxygen demand (BOD) in rivers. Rivers contain many biopersistent organic compounds such as humic acid, lignin, and gum arabic. Free radicals generated by self-decomposition of ozone were used as powerful oxidants to split organic compounds. Ozonysis of the samples was carried out by 42.4 g N −1 m −3 ozone for 3 min at pH 7.0. Artificial wastewater (AWW) solutions were employed as standard solutions for the calibrations of the BOD sensor. At a BOD of 1 mg l −1 , the sensor response after ozonation was 1.6-fold higher than that before ozonation. The response time of the BOD sensor was only 5 min, being independent of the concentrations, and the lower detection limit was 0.5 mg l −1 BOD. The degradations of lignin and tannic acid by ozonation were 54.1 and 42.3%, respectively. In the biosensor responses by ozonation, lignin, gum arabic, and surfactant increased by double or more compared with previous responses. BOD in rivers was estimated using the stopped-flow system. Environmental samples pretreated with ozone gave high responses to the biosensor that were similar to those of the conventional BOD 5 method. Accordingly, a good correlation between the sensor and the conventional BOD 5 was obtained (r = 0.989). The system has to evolve the highly sensitive BOD determination.
Development of highly sensitive BOD sensor and its evaluation using preozonation
Analytica Chimica Acta, 1999
A highly sensitive microbial sensor for biochemical oxygen demand (BOD) is described based on preozonation of refractory organic compounds in river waters. The hydroxyl radical generated by ozone decomposition was used as oxidant to split up organic compounds. Arti®cial wastewater (AWW) solutions were employed as standard solutions for the calibrations of the BOD sensor. The degree of degradation of organic compounds after ozonation of humic acid, lignin, tannic acid, gum arabic and surfactants were investigated as total organic carbon (TOC) reduction rates. The ozonation of AWW solutions was carried out by 42.4 g N À1 m À3 ozone for 3 min at pH 7.0. TOC reduction rates of humic acid and tannic acid were 22% and 18%, respectively, but gum arabic showed extremely low values. The sensor response to 1 mg l À1 BOD after ozonation was twice than that before ozonation. A typical response time of the BOD sensor was ca. 5 min, and the 3' lower detection limit was 0.2 mg l À1 BOD. BOD values estimated by the biosensor correlated well with those determined by the conventional BOD 5 method.
Development of a Photometric Method to Measure Molecular Oxygen in Water
Analytical Sciences, 2021
A photometric method to determine molecular oxygen in water was developed. When manganese(II) is oxidized by oxygen under alkaline conditions, the presence of polyphosphate can prevent precipitation due to a coacervate reaction. The oxidized manganese later dissolves in acid to form a pink Mn(III) species, which has a stable UV/vis spectrum. Monitoring of the oxygen concentration based on the absorbance of the pink Mn(III) species at 517 nm showed a strong correlation with both the Winkler method and an optical sensor. As a result, the present method can measure not only dissolved oxygen, but also fine bubbles oxygen in in the water sample with high reliability (0-26 mg dm-3 , r 2 = 0.9995). During this process, no significant interference from nitrite or metal ions was observed. The accuracy of the measurement was steady at high temperatures of the water samples (≤ 363 K).
Optical fiber biosensor for the determination of low biochemical oxygen demand
Biosensors and Bioelectronics, 2000
An optical fiber biosensor was developed for the evaluation of low Biochemical Oxygen Demand (BOD) values in river waters. Artificial wastewater (AWW) solution was employed as standards for the calibration of the BOD sensor. The response time of the sensor was 15 min, and the optimal BOD response was observed at 30°C, pH 7.0. A linear relationship was obtained between the output voltage and BOD 5 values, and the range of determination was 1 -10 mg 1 − 1 BOD. The sensor response was almost not influenced by chloride ion up to 1000 mg 1 − 1 , and also not affected by heavy metal ions (Fe 3 + , CU 2 + , Mn 2 + , Cr 3 + , Zn 2 + ). The BOD of river waters was estimated by using the optical fiber biosensor, and good correlation between the sensor and BOD 5 test was obtained (r 2 = 0.971).