Reasons why the ORP value cannot be reduced in the ultrafiltration system
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During the maintenance period some time ago, no chemicals were used for cleaning; only pure water was used for cleaning. Since then, the ORP value has remained high, around 263 (our target range is ±200). The hardness of the soft water used earlier was less than 0.01, and the data from the reverse osmosis system have also been normal. I would like to ask the experts what could be the cause of this
Re-calibrate it using a saturated solution of quinone and hydroquinone; if the ORP values remain normal in both cases, the problem may lie with the instrument itself.
A high ORP value indicates the presence of oxidizing ions or substances, and the specific cause in this case should be identified. Re-calibration cannot reduce the ORP in water. If the incoming water has been disinfected with chlorine or ozone, it is likely the effect of these oxidants.
Water hardness has no direct relationship with ORP; hardness reflects the concentration of calcium and magnesium ions in water, while the ORP value indicates the amount of oxidizing substances present in the water.
This has already been calibrated. . It still doesn’t work
In the previous steps, we only add flocculants and carry out brine regeneration; there’s nothing else
Is this closely related to dissolved oxygen?
Abstract: By analyzing the concept of redox potential, the calculation methods and measurement principles of redox potential are discussed. The use and calibration principles of digital ORP meters are explained in the form of chemical reaction equations. Explanations on usage methods and precautions are provided in conjunction with practical applications. In particular, the physical significance of the redox potential in environmental testing was analyzed and explained. Keywords: redox potential; environmental protection; determination; calibration Chinese Library Classification Number: TH183.3 Document Code: A 0 Introduction In environmental monitoring, redox potential (ORP) is an important indicator of the environmental conditions of a medium (including soil, water, culture media, etc.). For complex environmental systems, understanding the concept of redox potential, as well as its calculation and measurement principles, is essential for comprehending the reaction mechanisms of reactive agents in the environment. The most advanced instrument for measuring redox potential at present is the digital display ORP meter. However, their instruction manuals generally only provide information on usage and calibration methods, without explaining their structure or the principles behind calibration. To this end, this paper provides a detailed analysis of the structure and calibration principle of digital ORP meters. 1 Basic concepts of ORP: The essence of redox reactions is the transfer of electrons. The greater a substance’s tendency to accept electrons, the stronger its oxidizing power; such a substance is therefore a strong oxidizing agent. Conversely, a substance with a greater tendency to give up electrons is a strong reducing agent. Therefore, the strength of an oxidizing (reducing) agent can be compared by measuring the extent of its tendency to accept (or donate) electrons, which can be determined by assessing the potential difference between the electrode formed by the redox couple and a reference electrode. It is specified that the potential of the standard hydrogen electrode (NHE) is zero at any temperature; therefore, by measuring the potential difference between an electrode composed of a redox couple and the standard hydrogen electrode in a galvanic cell, and eliminating the junction potential, the electrode potential of that redox couple is obtained, which is also known as ORP. When there is a reversible redox couple in a solution, its redox half-reaction is expressed as Ox + ne = Red (1). The value of ORP follows the Nernst equation: EOx/Red = E0 Ox/Red + (0.059/n)lg(AOx/ARed) (2). Here, EOx/Red represents the electrode potential of the Ox/Red couple, which is essentially ORP; Ox denotes the oxidized state, while Red denotes the reduced state. E0 Ox/Red is the standard electrode potential of the Ox/Red couple, and it depends only on the nature of the couple and the temperature. AOx and ARed are the activities of the oxidized and reduced states respectively (activity = activity coefficient × concentration), and n is the number of electrons transferred in the half-reaction. In actual solutions, the ionic strength is often high. Moreover, when the composition of the solution changes or side reactions occur, the forms in which the oxidized and reduced states of the redox pair exist also tend to change, thereby causing variations in the electrode potential. Therefore, the conditional electrode potential is commonly used for calculations: EOx/Red = E0’Ox/Red + (0.059/n)lg(cOx/cRed). In equation (3), E0’Ox/Red represents the conditional electrode potential of the Ox/Red couple, and it is influenced by the nature of the couple, temperature, ionic strength, acidity, and side reactions