Aspects of protonation and deprotonation of humic scid durface on molecular conformation

Journal of the Brazilian Chemical Society

Universidade de Brasília, Brasília, Brazil¹  Prado, Alexandre G. S.¹  Pertusatti, Jonas¹  Nunes, Alécio R.¹ 

关键词: humic acid;    pH;    surface charge density;    conformation;   

DOI  :  10.1590/S0103-50532011000800011

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

The surface charge densities for humic acids (HAs) were determined by simultaneous potentiometric and conductimetric titrations. It was also observed the pH influence on molecular conformation by UV-Vis spectroscopy measurements and scanning electron microscopy (SEM) images. The surface charge densities are approximately zero at the pH range 3.5 to 6.0 for all samples. The pH influence on molecular condensation level was observed by the determination of the β index from Doty and Steiner equation. High values of β were obtained at acid region indicating a condensed conformation due to weak attractive interactions whereas around the neutral region the repulsive intramolecular forces take place leading to an extended conformation of humic molecules. Moreover, at very alkaline region, the charge density on molecule surface is more negative, increasing repulsion and dispersion of the particles and also takes place formation of micelle-like structure because of the amphyphylic feature of HA samples.

【 授权许可】

Unknown