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Sorption and Intraparticle Diffusion of Fluorescent Dyes with Consolidated Aquifer Media
Author(s) -
Sabatini David A.
Publication year - 2000
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.2000.tb02700.x
Subject(s) - sorption , tortuosity , diffusion , particle size , adsorption , chemistry , particle (ecology) , chemical engineering , porous medium , sulforhodamine b , porosity , materials science , analytical chemistry (journal) , mineralogy , thermodynamics , chromatography , geology , organic chemistry , physics , oceanography , engineering , biochemistry , cytotoxicity , in vitro
Sorption of two fluorescent dyes (fluorescein and sulforhodamine B) was evaluated with two oppositely charged, consolidated aquifer materials (sandstone and limestone). Fluorescein, which has an anionic carboxylic group, experienced negligible sorption onto negatively charged sandstone and sorbed much less than sulforhodamine B, with its two sulfonic groups, onto positively charged limestone. The cationic charge on sulforhodamine B caused it to adsorb onto negatively charged sandstone. These results validate and extend previous research with pure mineral surfaces (alumina and silica). Sorption kinetic rates decreased with increasing particle size, which is consistent with diffusion‐limited intraparticle sorption. Tortuosity factors were determined by fitting a diffusion ‐limited intraparticle sorption model to kinetic data for one particle size (all other parameters being determined independently). This tortuosity factor, which was consistent with Archie's law‐based estimates and other independently determined parameters, was subsequently used to predict kinetic adsorption results for a second particle size. Close agreement between experimental data and model predictions corroborated intraparticle diffusion‐limited sorption as an important process. Diffusion‐limited sorption can impact dye transport in unconsolidated grains having internal porosity or consolidated or fractured media having dual porosity. These results thus demonstrate the importance of understanding both the equilibrium and kinetics of dye sorption when designing and interpreting tracer studies.