Elsevier

Microchemical Journal

Volume 59, Issue 2, June 1998, Pages 246-257
Microchemical Journal

Regular Article
Sewage Sludge Microwave Digestion Procedure Optimized by Temperature and Pressure Analysis,☆☆

https://doi.org/10.1006/mchj.1998.1613Get rights and content

Abstract

An investigation of the treating process within a closed vessel is reported. The decomposition behavior of a sample–acid mixture was studied by means of pressure (P)-versus-temperature (T) profiles. Adopting the slope variation of pressure as an indicator of the outcome of decomposition of the sample, the corresponding recorded temperature should be expected to be the specific temperature for rapid decomposition of a given organic matrix. Preliminary results obtained on acidified samples (concentrated nitric acid and sludge–HNO3mixture) exposed to 800 W of power showed that the pressure curve of the acidified sample coincides with that obtained for the pure reagent until the organic matrix begins to decompose. In fact, the pressure within the vessel containing the acidified sample is a combination of the partial pressure of HNO3and the pressures of the gaseous products arising during digestion. At temperatures greater than 160°C the nitric vapor pressure masks the additional pressure due to the reaction gases. Chemical analysis of digests from the four microwave programs considered provided interesting results for solid residue and total organic carbon in soluble and insoluble fractions.

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This article is part of a special section devoted to the Eighth Hungarian–Italian Symposium on Spectrochemistry.

☆☆

R. Gay

2

To whom correspondence should be addressed.

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