Optimization of H2O2 action in sewage-sludge microwave digestion using Delta pressure vs. temperature and pressure vs. time graphs

摘要

In a previous study (Microchem. J. 59 (1998) 246-257) a systematic approach had been developed to optimize the experimental conditions applied during microwave-assisted mineralization of sewage-sludge samples. An innovative elaboration of data acquired by real-time monitoring of temperature and pressure inside a closed vessel heated by microwave radiation had been performed to determine thermodynamic and kinetic behavior of sample-HNO3 mixtures. The difference (Delta pressure) between the pressure recorded during sample-HNO3 heating and the corresponding vapor pressure of the pure reagent had been calculated as a function of temperature. Only concentrated HNO3 had been chosen as a digesting reagent to reduce the complexity of the observations to a single power-absorbing component. In this work the performance of other digesting reagents prepared by mixing HNO3 with H2O2 was tested. Results obtained by examining Delta pressure vs. temperature graphs were compared with treatment efficiencies determined by measuring total-organic-carbon variation as well as heavy-metal recovery in the digests. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 9]