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Methods for Water Analysis
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
Digestion can be done in an Erlenmeyer flask or a beaker, on a hotplate. A measure of 50–100 mL of the sample is mixed with acid and boiled down to the lowest volume possible, without allowing it to dry. Portions of concentrated acid are added, and heating continues until the sample is clear and light in color, at which point digestion is considered complete. The sample is then cooled, diluted to volume, and is ready for analysis. The use of microwave digestion gives more reproducible results, because temperature and digestion times are automatically controlled by a user-defined program. Microwave digestion has the additional advantage that it takes place in a sealed container, with the vented fumes being directed to a scrubber. This eliminates corrosive acid fumes in the laboratory hood, and prevents contamination of the samples by airborne dust.
Measurement of Pollutant Distribution, Toxicity, and Effectiveness of Emerging Soil Remediation Techniques
Published in Donald L. Wise, Debra J. Trantolo, Edward J. Cichon, Hilary I. Inyang, Ulrich Stottmeister, Remediation Engineering of Contaminated Soils, 2000
K. Bundy, F. Mowat, P. Taverna, M. Shettlemore
When assays of organic compounds are needed, specimens are sent to an analytical laboratory at Tulane (the Coordinated Instrumentation Facility, CIF). The CIF laboratory analyzes the organic content using accelerated solvent extraction with dichloromethane and acetone followed by hexane exchange and GC/MS measurement. In this manner 65 organic compounds (including 25 PAHs) can be detected, including 18 compounds found in Bayou Trepagnier (see the Test Sites section) that represent most of the major classes of organic pollutants in this waterway. To complement the organic analysis of these specimens, we have the CIF perform inorganic analyses for a suite of 10 heavy metals, including As,Cd,Cr,Cu,Pb, and Zn. For inorganic analyses, microwave digestion is performed according to U.S. EPA method SW-846 3052, "Microwave Assisted Acid Digestion of Siliceous and Organically Based Matrices." This technique is used for digestion of siliceous and other complex matrices including soils, sediments, and sludges. Figure 4 provides an overview of the different extraction and analytical methods used in the research reported here.
Emerging role of organic acids in leaching of valuable metals from refinery-spent hydroprocessing catalysts, and potential techno-economic challenges: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Ashish Pathak, Mari Vinoba, Richa Kothari
Besides removing the contaminant deposited metals, almost complete recovery of valuable metals from a decoked spent catalyst was obtained using the EDTA leaching at a higher temperature (50 °C). It was reported that under these conditions,>97.0% of the Ni, V, and Mo can be leached out within 6 h of leaching. Moreover, the used EDTA can be easily recovered through dechelation using H2SO4 (pH = 1). Under these acidic conditions, the metal-EDTA complex is broken and EDTA is recovered as H4EDTA in the solid form. The EDTA recovery as high as 95.0% can be achieved, which makes this process highly economical (Al-Sheeha et al., 2013). Although the above studies using EDTA were found to be highly effective, these studies were conducted using conventional leaching which takes long reaction time (4–24 h). It has been reported that the reaction rate can be further improved using microwave digestion. The use of microwave digestion with EDTA can result in leaching of about 80.0% Ni within just 4 cycles of 60.0 seconds (total 4 mins reaction). Moreover, the yield of Al can be minimized (<4.00%). In comparison, the leaching yield of Ni was only 40.0% in the conventional water bath even after 8 h of leaching period (Pinto & Soares, 2013a, 2013b).