Effect of adsorption of non-protolyzable anions on goethite (alpha-FeOOH) mobility
THE PROCESSES OCCURRING AT THE SOLID-WATER INTERFACE ARE IMPORTANT CONTROLS ON THE MOBILITY OF MANY INORGANIC IONS IN THE ENVIRONMENT. ANION ADSORPTION ON IRON HYDROXIDE USUALLY DECREASES THE PARTICLE MOBILITY AND MAKES THE PARTICLE SURFACE LESS POSITIVE. HOWEVER, FOR SOME NON-PROTOLYZABLE ANIONS LIKE FLUORIDE AND ARSENITE, THE ADSORPTION HAS ALMOST NO EFFECT ON SURFACE CHARGE. THIS BEHAVIOR IS INCONSISTENT WITH THE COMMONLY USED MODELS FOR ANION ADSORPTION. THE FOCUS OF THIS STUDY IS TO GAIN FURTHER UNDERSTANDING INTO WHY THIS OCCURS. ADSORPTION EXPERIMENTS WERE CONDUCTED AT DIFFERENT PH, INITIAL ADSORBATE CONCENTRATION, SOLIDS SOLUTION RATIO AND IONIC STRENGTH. THE EFFECT OF FLUORIDE ADSORPTION AND ARSENITE ADSORPTION (TO A LESS EXTENT) ON ZETA POTENTIAL WAS INVESTIGATED, ALONG WITH THE CONCURRENT HYDROXYL ION RELEASE AND INERT ION (NITRATE) DESORPTION. RESULTS SHOW A COMPLEX COMBINATION OF SURFACE REACTIONS. NEITHER THE TRADITIONAL 1-PKA NOR 2-PKA MODELS CAN PROVIDE EFFECT
goethite, non-protolyzable anions, particle mobility, zeta potential, surface complexation model, surface precipitation model
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