Transport behavior and deposition kinetics of humic acid under acidic conditions in porous media

Yamashita, Yuji*; Tanaka, Tadao ; Adachi, Yasuhisa*

Transport behavior of humic acid was studied from the aspects of colloidal stability. Deposition kinetics of purified Aldrich humic acid was investigated over a wide range of monovalent and divalent electrolyte concentrations at pH 3.0 by using packed-bed technique. Spherical glass beads with diameters of 0.2 mm were utilized as model collectors. Breakthrough curves of humic acid were measured with UV-VIS spectrophotometer. The values of C/C0 (C and C0 are the effluent and influent concentrations of humic acid, respectively) decreased with increasing electrolyte concentrations. Experimental collision efficiencies were determined from measured single collector efficiencies. The results are presented as stability curves, which is the logarithm of the collision efficiency as a function of the logarithm of salt concentration. Stability curves of humic acid obviously showed favorable and unfavorable regimes and critical deposition concentration in the presence of both electrolytes. As a consequence, it is indicated that transport behavior of humic acid is primarily controlled by electrostatic interaction between humic acids and collectors.