Adsorption of sodium lauryl sulfate onto arsenic-bearing ferrihydrite.
Ferrihydrite is an excellent adsorbent for binding trace toxic contaminants such as arsenic, and precipitate flotation of the arsenic-bearing ferrihydrite has been studied. Anionic surfactants such as sodium lauryl sulfate (SLS) and sodium oleate (NaOL) are suitable collectors for the flotation. The adsorption of SLS both alone and after the subsequent addition of NaOL on these precipitates at pH 4-5 was measured. It has been shown that the synergistic effect of the two surfactants on flotation is dependent on their addition order. The presence of NaOL before SLS in the conditioning stage can prevent the adsorption of SLS because of the electrostatic shielding of adsorption sites on the precipitates. The post addition of NaOL to the SLS-bearing precipitates can promote the flocculation of the precipitates and enhance entrainment of SLS for better flotation. The SLS adsorption data fit better with the modified Frumkin isotherm than the Langmuir isotherm. Thermodynamic parameters (-delta Gads0,delta Hads0, and delta Sads0) have been derived from the analysis of the adsorption isotherms. The results suggest that the adsorption of SLS on AFH is physical and exothermic.
ANSTO, Lucas Heights Science & Technology Centre, Private Mail Bag 1, Menai NSW 2234, Australia. chq@ansto.gov.au
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D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D011232:Chemical Precipitation; D005290:Ferric Compounds; D005293:Ferritins / Q000737:chemistry*; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D019301:Oleic Acid / Q000737:chemistry; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D018508:Water Purification / Q000379:methods
D005290:Ferric Compounds; D013501:Surface-Active Agents; D019301:Oleic Acid; D012967:Sodium Dodecyl Sulfate; C013173:osteum; C092844:ferric oxyhydroxide; D005293:Ferritins; D001151:Arsenic