394-12 Competitive Sorption and Displacement of Arsenate by Phosphate On An Aluminum Mining by-Product.



Wednesday, October 19, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

Enio Costa1, Luiz-Roberto Guilherme2, Guilherme Lopes2, Jose Lima2 and Nilton Curi2, (1)Federal University of Lavras, Lavras, Brazil
(2)Federal University of Lavras, Lavras, MG, BRAZIL
Antagonistic effects between competing ions are important when evaluating a by-product as a potential adsorbent and, or soil amendment. This work aimed to assess: i)  mono- and multielement adsorption and desorption of P and As on an aluminum mining by-product; and, ii) the displacement of previously adsorbed arsenate by phosphate added at increasing doses in solution. For adsorption, 0.3 g of the adsorbent were suspended in 20 mL of 30 mmol L-1 NaCl, which had its pH adjusted to 5.5 with the addition of predetermined amounts of 1 mol L-1 HCl and 1 mol L-1 NaOH. After adjusting the pH, phosphate and arsenate were added as H3PO4 and Na2HAsO4.7H2O in single and mix solutions with initial concentrations of 0.67 mmol L-1 (adsorbent:solution rate of 1:100) After 72h of reaction, samples were centrifuged and the supernatant collected for As and P analyses. The remaining residue was reacted with 30 mL of 30 mmol L-1 NaCl to promote desorption of previously adsorbed elements. To evaluate the displacement of arsenate by phosphate, we add 30 mL of a 30 mmol L-1 NaCl containing phosphate in the following concentrations: 0, 0.007, 0.014, 0.1, 1.0, and 2.0 mmol L-1. The competition between phosphate and arsenate reduced the adsorbed concentration by 3 and 23%, respectively when comparing single versus mix systems. On the other hand, this competition increased phosphate desorption up to 4 fold and arsenate up to 2 fold. The ratio mmol kg-1 of adsorbed phosphate/mmol kg-1 of desorbed arsenate decreased upon increasing the concentration of P in the displacement solution (2.3±1.1 and 0.98±0.03 for solutions containing 0.007 and 0.014 mmol L-1 of phosphate, respectively). Sponsored by CAPES, CNPq, and FAPEMIG.
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