Oxidation reduction potential ORP

Ozone can be analyzed by titrimetry, direct and colorimetric spectrometry, amperometry, oxidation—reduction potential (ORP), chemiluminescence, calorimetry, thermal conductivity, and isothermal pressure change on decomposition. The last three methods ate not frequently employed. Proper measurement of ozone in water requites an awareness of its reactivity, instabiUty, volatility, and the potential effect of interfering substances. To eliminate interferences, ozone sometimes is sparged out of solution by using an inert gas for analysis in the gas phase or on reabsorption in a clean solution. Historically, the most common analytical procedure has been the iodometric method in which gaseous ozone is absorbed by aqueous KI. 

Hexavalent chromium wastes resulting from rinsewater and the concentrated acid bleed accumulate in the chromium waste sump [T-20], The chromium wastes are then pumped into the chromium treatment module [T-21] for reduction to the trivalent form. This pump is activated only if the oxidation-reduction potential (ORP) and pH are at the proper levels and if the level in the chromium wastewater sump [T-20] is sufficiently high. 

Soil samples were collected along a traverse over the Honerat kimberlite and extended off the kimberlite approximately 75 m SE and 225 m NW from the pipe s centre (Fig. 1). Although it is common practice to collect samples from upper B-horizon soil (Levinson 1980 Bajc 1998 Mann et al. 2005) our samples were collected from C-horizon soil because GAGI samplers were placed at a depth of 60 cm (well below the B horizon). Within 8 hours of sampling, a portion of each soil sample was mixed with Milli-Q water (1 1) to create a slurry. The values of pH and oxidation-reduction potential (ORP) were determined in each slurry. Ammonia acetate leach of the soil samples were performed at Acme Analytical Laboratories, Vancouver, where 20 ml of ammonium acetate was mixed with 1 g soil sample and elements were determined by inductively coupled plasma-mass spectrometry. The GAGI samplers installed at Unknown were placed in piezometers and submerged in water at a depth of approximately 1 m below ground surface. 

Oxidation-Reduction Potential Oxidation-reduction potential (ORP) is measured by an ORP probe, which is effective to monitor the redox potential of a bioreactor operated under microaerobic conditions that cannot be successfully measured by a DO probe. The measurements of redox are sometimes influenced by changes in the pH and mineral concentrations of a culture broth. 

Cooling systems are dynamic and therefore need various control and monitoring systems. Among them are systems for injection of acid or specialty chemicals, real-time monitoring and recording of the water treatment program performance, and the control of pH, TDS, oxidation reduction potential (ORP), suspended solids (SS), etc. 

We use water quality indicators, such as pH, temperature, conductivity (specific conductance), dissolved oxygen, oxidation-reduction potential (ORP), and turbidity, as groundwater well stabilization parameters. Stable values of three consecutive measurements of these parameters are considered an indication of a stabilized well. 

The electrochemical analyzers are another important family of liquid analyzers. They include potentiometric, wherein an electric potential is measured and the solution remains unchanged conductive, in which a minute current is measured but the system is essentially unchanged and amperometric, in which a chemical reaction occurs during the course of the measurement. Potentiometric analyzers can measure the presence of dissolved ionized solids in a solution. These measurements include pH, oxidation-reduction potential (ORP), and ion-selective electrodes (ISEs) or probes. 

Trick J. K., Stuart M., and Reeder S. describe the tools available to the field sampler for the collection of groundwater samples, methods of on-site water quality analysis, and the appropriate preservation and handling ofsamples. The authors discuss the merits of different purge methodologies and show how on-site measurements such as pH, specific electrical conductance (SEC), oxidation—reduction potential (ORP), dissolved oxygen (DO), temperature, and alkalinity can be used to provide a check on subsequent laboratory analyses. Techniques for the preservation and analysis of samples and quality assurance and quality control are also presented. 

The need for oxidants can be determined by measuring the oxidation reduction potential (ORP) of the water to be treated. If the ORP measures above negative 170 millivolts, Filox can be used without the use of additional oxidants. Lower than negative 170 millivolts will require additional oxidants. Air, hypochlorite, hydrogen peroxide, ozone, and potassium permanganate are all suitable oxidants to use with Filox. Note that weaker oxidants, such as air and hypochlorite will be sufficient for most applications. 

Chlorine residual concentrations of the water upstream and downstream of the dechloramination chemical feed points were measured using a Hach Chlorine Pocket Colorimeter. Temperature, dissolved oxygen (DO), pH, and oxidation-reduction potential (ORP) were also measured during the field study. 

Eh is often confused with the closely related redox potential or oxidation-reduction potential (ORP) measurement. ORP is measured by placing a redox electrode into water or sediment the redox electrode is a piece of metallic platinum, which acquires a more negative potential with respect to its reference electrode under reducing conditions where electron activities are higher. ORP is the voltage measured between this redox electrode and a reference electrode placed in the same environment. It provides a useful, approximate characterization of redox conditions in the aquatic environment, although it... 

In field applications, evidence of enhanced reduction of Cr(VI) by a DC electric field was first reported in 1987 by Banarjee et al (1987) at a Superfund site in Corvallis, Oregon. Later, controlled laboratory experiments of kaolinite clay injected with Fe(II) showed that an externally applied electric field caused an additional cathodic current that drive forth the reduction of Cr(VI) in clay (Pamukcu, Weeks, and Wittle, 2004). These transformations were characterized as to have benefited the capacitive changes on the clay surfaces. The results in these experiments showed that the system oxidation-reduction potential (ORP) increased by a positive shift from the standard solution ORP in the presence of the clay medium and the induced electrical field. Rgure 2.13 shows the ORP measurements plotted against the reaction quotient of the Nemst relation, where the data is categorized by pH. Under anoxic conditions and acidic environments, Fe(II) can be the dominant reductant of Cr(VI), as given by the following redox reaction ... 

Ensuring by adjustment of the pH and control of the oxidation-reduction potential (ORP) that it is not further oxidized to bromate, the bromine is air-stripped from the solution. In commercial operation [194], this process lowers bromide levels from 50 ppm to less than 0.5 ppm. Figure 7.91 is a schematic of the process. Heating the brine to a higher temperature (>65°C) helps to remove the low concentration of bromine there will also be chlorine present in the offgas. 

Flow controllers set the rates of both streams, one being under flow-ratio control. In principle, either caustic soda or dilution water can be the master stream, with the other following it to maintain the ratio. Blending is controlled by a feedforward system, ultimately reset by the product concentration or density. Feedback from caustic concentration measurement (usually by density) could be used for final adjustment, but the concentration of the hypochlorite solution is the more important variable. The simple flow-ratio controller mentioned here can be replaced by a multi-stream version that allows use of other streams in addition to the principal 50% NaOH and dilution water. A cooler downstream of the mixing point removes the heat of dilution. The standard design is a titanium plate exchanger, which can also provide turbulence to complete the mixing process. Chlorine joins the diluted caustic in the reactor. Its rate of addition is controlled by an oxidation-reduction potential (ORP) instrument. The reaction mass recirculates from a collection tank around the system to reduce the increase of temperature across the reactor and to promote turbulence. The net production is removed from the tank, normally under level control. 

Chlorination is usually measured by oxidation-reduction potential (ORP). The sensing electrode directly contacts the solution, therefore it responds much faster than pH electrodes. It is also much more mechanically robust. ORP measures the reduction of hypochlorite by the following reaction ... 

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