Optimization of H_CO_2 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-HNO_3 mixtures. The difference (#DELTA# pressure) between the pressure recorded during sample-HNO_3 heating and the corresponding vapor pressure of the pure reagent had been calculated as a function of temperature. Only concentrated HNO_3 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 HNO_3 with H_CO_2 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.