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Corrosion Behaviour of a Carbon Steel Valve in a Microbial Environment
Published in A. K. Tiller, C. A. C. Sequeira, Microbial Corrosion, 2021
J. C. Danko, C. D. Lundin, N. J. E. Dowling, W. Hester
Chloride concentration in the deposits on the walls of the pipe samples sent were determined using potentiometric titration with silver nitrate solution and a silver/ silver chloride electrode system. During titration a Sycopel voltmeter was used to measure the change in potential between the two electrodes. The sample was dissolved by heating at 50°C for 1 h, and then 20 mL were added to 0.01M HNO3. The AgNO3 is added in increments and the open-circuit potential is recorded each time. The end point of the titration is that point at which the greatest change in voltage has occurred. Results are found in Table 4.
Potentiometry
Published in Ernő Pungor, A Practical Guide to Instrumental Analysis, 2020
Potentiometric methods belong to two major types: Direct potentiometry. Direct measurements of concentrations or activities. In this case the ion activity or ion concentration is determined by means of a calibration curve or the standard addition technique.Indirect potentiometry or potentiometric titration. The component to be determined is titrated with a suitable titrant and the indicator electrode is used to follow the changes in potential in the course of the titration.
Electrochemical Composition Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Michael J. Schöning, Arshak Poghossian, Olaf Glück, Marion Thust
Potentiometric Titration: Potentiometric titration can be applied in the fields of acid–base, precipitation, complex formation, and redox reactions. Therefore, the ISE is used in combination with a reference electrode in order to establish the EP in a titration curve. A typical S-shaped potentiometric titration curve, where the electrode potential is plotted versus the reagent volume (titrant), is given in Figure 55.20a. The titrant is added to the initial solution that is stirred, and the ISE records the potential value at equilibrium. The EP (endpoint) of the reaction is reached when a sudden change in the potential of the ISE occurs. The midpoint in the curve (i.e., the steeply rising portion) is termed endpoint or inflection point. It can be evaluated by analytical methods, namely, the first- and second-derivative curves (Figure 55.20b and c). The first-derivative curve gives the potential change per unit change in volume of reagent and depicts the endpoint at the maximum of the inflection point. The second-derivative curve is zero where ∆E/∆V reaches its maximum. The greater the slope at the endpoint, the smaller should be the volume increment in order to reduce titration errors.
Biosorption of methylene blue and eriochrome black T onto the brown macroalgae Fucus vesiculosus: equilibrium, kinetics, thermodynamics and optimization
Published in Environmental Technology, 2021
Yuri Abner Rocha Lebron, Victor Rezende Moreira, Lucilaine Valéria de Souza Santos
The bioadsorbent was characterized in terms of its morphology and composition with the aid of the following techniques. ATR-FTIR (Shimadzu IRAffinity-1) analyses were performed between 750 and 4000 cm−1, before and after the biosorption process, both on the same background, using 20 scans and a resolution of 4 scans per second. Size, morphology and bioadsorbent surface composition were complemented by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), (JEOL JSM IT300). Thermogravimetric analyses were performed in aluminium crucible with N2 flow of 50 mL·min−1 and a heating rate of 10 °C·min−1 (Shimadzu DTG-60H). The bioadsorbent zero point charge was determined by potentiometric titration. Thus, 750 mg of the bioadsorbent was added to 50 mL of 0.03 mol·L−1 KNO3 solution and kept under constant agitation in an orbital shaker (Marconi MA420) (250 rpm) for approximately 24 h, or until there was no further pH variation. Then, 50 µL of KOH 1 mol·L−1 was added to the medium in order to ensure that the active sites were deprotonated before proceeding to the titration step, which consisted in the addition of 0.05 mL of 0.1 mol·L−1 HNO3 under constant agitation [21]. The pH variation as a function of the HNO3 addition was recorded and the potentiometric curves obtained. First and second derivative transformation was applied to better identify the inflection point.
Effect and mechanism of modification treatment on ammonium and phosphate removal by ferric-modified zeolite
Published in Environmental Technology, 2019
Lin Gao, Chenyi Zhang, Yi Sun, Chuanming Ma
The point of zero charge (pHpzc), CEC and the content of exchangeable Fe3+ cation (Feex) in zeolite framework were also determined. The pHpzc was determined by employing the method described by Kragović et al. [19]. And, CEC was obtained by the potentiometric titration method [20]. Feex was calculated by adopting the ammonium acetate method. 0.2 g sample was mixed with 20 mL 1 mol/L ammonium acetate with pH adjusted to 7, centrifuged at 4000 rpm for 10 min and then filtered using a 0.45-μm filter membrane. The procedure was replicated three to five times until free from Ca2+ cation (checked by K–B mixed indicator). All filtrate was collected and Fe3+ was determined by flame atomic absorption spectrometry (AAS, Hitachi-Z2000 series, Japan).
Nitric Acid Extraction into a TODGA Solvent Modified with 1-Octanol
Published in Solvent Extraction and Ion Exchange, 2019
David Woodhead, Fiona McLachlan, Robin Taylor, Udo Müllich, Andreas Geist, Andreas Wilden, Giuseppe Modolo
The aqueous phase was nitric acid (0.1–9 mol/L), and the organic phase was TODGA (0.05–0.4 mol/L) in Exxsol D80 or TODGA (0.05–0.3 mol/L) + octanol (5 v/v%) in TPH or Exxsol D80. Additional experiments with aqueous phase ≈2.8 mol/L HNO3, organic phase TODGA (0.1–0.3 mol/L) + octanol (5–50 v/v%) were undertaken. Equal volumes of aqueous and organic phases were contacted on an orbital shaker (2500/min) for 15 min (it was previously verified that equilibrium had been attained within several minutes) at 20 ± 0.5°C, 22 ± 1°C, or ambient (≈20–25°C), depending on which of the labs involved performed the experiments. Following centrifugation, organic-phase aliquots were stripped into water (A/O = 1–4). Nitric acid concentrations were determined by duplicate potentiometric titration with NaOH (0.02–0.1 mol/L).