Troca ionica, calorimetria, analise termica e microbiologica aplicadas ao latossolo roxo

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

The adsorption/ionic exchange process on the heterogeneous surface of red latosol soil (LR) showed the adsorption order Pb >Cd >Zn. However, the opposite was observed for cerrado soil. The kinetics of adsorption/desorption in red latosol soil with the cation index Ca showed a maximum desorption of 37.5%. When it was saturated with Ca and exchanged with Pb, the index cation is found in solution. The ionic exchange process employing LR, as a function of temperature (K), indicated the sequence of adsorption: 298K: Pb >Cu >Cd >Hg ~ Ca >Zn >Na; 305K: Pb >Cd >Hg ~ Ca >Cu >Zn >Na; 315K: Pb>Cu and 323K: Pb>Cd >Hg >Zn >Cu >Ca >Na. The increase in temperature is followed by an enhancement of the ionic exchange from which thermodynamic values were calculated for the Langmuir equation (DHL) and the proposed Rawat method (DHR). These both gave exothermic values for Cu >Pb >Cd, and endothermic values for Zn >Na >Ca >Hg; and Na ~ Ca >Zn >Hg, respectively. The variation in DG values indicated expontaneous processes. The pH measured on the solution after the ionic exchange processes gave the order: 295K: Ca >Pb >Cd >Zn >Cu >Na >Hg; 305K: Cu ~Ca >Pb >Zn ~ Cd >Hg >Na; 315K: Cu >Pb e 323K: Ca >Zn >Pb ~Na>Cu >Hg >Cd. The microbiological activity was followed through microcalorimetry, using degradation of a mixture of glucose and ammonium sulfate (1:1) which varied from 2.0 to 10.0 mg in 1.50 g of LR and 53% humidity. This gave thermal effects of 2000 to 2500 kJ/mol. The results of degradation are in the 71 to 89 % range at 250 h. Variation of humidity gave enthalpic values of 2500 kJ/mol (53 and 38%) and 2100 kJ/mol (20%). At 53% humidity aerobic and anaerobic microorganisms cultures develop. Variable amounts of herbicides (1.0 to 8.0 mg) gave enthalpic values of 2500 (paraquat), 1500 (diquat) and 2500 to 900 kJ/mol (fosfamidon). The bacterias and fungi extracted from LR were inoculated in soil with nutrients. The enthalpic values showed for bacteria (1st) in extracted soil medium 2100 kJ moI, fungi in BDA 700 to 1000 kJ moI, mixture of bacterias 800 kJ moI and bacteria (2nd) in B king media 400 kJ moI. The evolution of CO2 gives the order: soil plus glucose >soil plus bacteria (1st) >soil plus bacteria (2nd) >fungi ~ 1st plus 2nd bacteria ~ soil without glucose. The thermal stability of soil components was followed by thermogravimetry and differential scanning calorimetry. The humic acids extracted from soils were compared with a commercial one. The argon atmosphere gave a slow decomposition compared with synthetic air. Samples of LR from sugar cane cultivation after firing presented small differences in comparation to the original soil

ASSUNTO(S)

calorimetria microorganismo do solo troca ionica solos - analise

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