ISSN:
1040-0397
Keywords:
Chemical oxygen demand
;
Coulometry
;
Chromium
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The chemical oxygen demand (COD) of solutions containing various organic compounds is calculated from the net faradaic charge (Qnet) estimated for the total electrolytic oxidation of CrIII generated during oxidative degradation of the organic compounds in acidic media containing excess CrVI. Values of Qnet for conversion of CrIII to CrVI are estimated from the linearized chronoamperometric data plotted as In {itat, t} vs. t. This procedure is preferred over determinations of Qnet from the total integrals of itot over the entire electrolysis period because of large errors that can result from uncertainty in the background current (ibkg) for t → ∞. The proposed coulometric procedure offers the benefit that reagent solutions can be reused, thereby minimizing the need for disposal of wastes containing toxic CrVI. This procedure was applied in a single digest solution for consecutive determinations of COD. Average COD values for potassium acid phthalate and glucose were 103.8% (s - 6.0, N - 10) and 100.2% (s - 4.2, N - 11), respectively, based on the theoretical degradation to CO2. In comparison for these same samples, an EPA approved method, based on colorimetric determination of CrIII, gave COD values of 101.4% (S - 1.4, N - 5) and 100.1% (s - 1.4, N - 5) of the theoretical. Statistical tests indicate no significant difference in the COD values determined for these compounds using the coulometric and EPA methods.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/elan.1140090403
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