KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS

The kinetics for the sorption of molybdate and phosphate by four Chilean Andisols have been determined. About 55%o of the molybdate and 61% of the phosphate was sorbed in the first 0.5 h, after which sorption slowly increased, reaching 90%o for molybdate and 97% for phosphate after 72 h. At the same...

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Autores principales:	Vistoso G,Erika Marina, Bolán,Nanthi S, Theng,Benny K. G, Mora,María de la Luz
Lenguaje:	English
Publicado:	Sociedad Chilena de la Ciencia del Suelo 2009
Materias:	Al- and Fe-oxide Chilean Andisols kinetic model molybdate and phosphate
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-27912009000100005
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spelling	oai:scielo:S0718-279120090001000052009-06-26KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLSVistoso G,Erika MarinaBolán,Nanthi STheng,Benny K. GMora,María de la Luz Al- and Fe-oxide Chilean Andisols kinetic model molybdate and phosphate The kinetics for the sorption of molybdate and phosphate by four Chilean Andisols have been determined. About 55%o of the molybdate and 61% of the phosphate was sorbed in the first 0.5 h, after which sorption slowly increased, reaching 90%o for molybdate and 97% for phosphate after 72 h. At the same time, OH¯ ions were released into the external solution, raising its pH by 0.85 units for molybdate and by 0.65 units in the case of phosphate. These observations indicated that both anions were sorpbed by a ligand exchange mechanims. Among the five kinetic models examined (),Table, 2 the Elovich equation gave the best fit of the experimental data (R² = 0.93 to 0.97, standard error = 0.35 to 0.94). The sorption rate constant (α) for both anions was related to the organic matter (OM) content of the soils, especially the content of Al- and Fe-humus complexes. The α values for molybdate were 2.24x10(15) mmol kg-1 h-1 for the Vilcun soil (15% OM), 2.49 x10(12) mmol kg-1 h-1 for the Pemehue soil (16% OM), 8.76x10(10) mmol kg- h-1 for the Osorno soil (20% OM), and 3.11x10(7) mmol kg-1 h-1 for the Piedras Negras soil (24% OM). The corresponding values for phosphate were 3.89x10(7), 5.21x10¹ , 3.11 x10(12) and 1.08x10(16) mmol kg-1 h-1. The desorption rate constant (β) for the four soils (in the above order) ranged from 0.47 to 0.28 for molybdate, and 0.22 to 0.39 mmol kg-1 h-1 for phosphate. The results suggest that the mineralogical composition and organic matter content of the Andisols control the kinetics for the sorption of both molybdate and phosphate. Molybdate appeared to have a high affinity for Fe- and Al-oxides, while phosphate was largely sorbed to Fe-and Al-humus complexes.info:eu-repo/semantics/openAccessSociedad Chilena de la Ciencia del SueloRevista de la ciencia del suelo y nutrición vegetal v.9 n.1 20092009-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-27912009000100005en10.4067/S0718-27912009000100005
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Al- and Fe-oxide Chilean Andisols kinetic model molybdate and phosphate
spellingShingle	Al- and Fe-oxide Chilean Andisols kinetic model molybdate and phosphate Vistoso G,Erika Marina Bolán,Nanthi S Theng,Benny K. G Mora,María de la Luz KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS
description	The kinetics for the sorption of molybdate and phosphate by four Chilean Andisols have been determined. About 55%o of the molybdate and 61% of the phosphate was sorbed in the first 0.5 h, after which sorption slowly increased, reaching 90%o for molybdate and 97% for phosphate after 72 h. At the same time, OH¯ ions were released into the external solution, raising its pH by 0.85 units for molybdate and by 0.65 units in the case of phosphate. These observations indicated that both anions were sorpbed by a ligand exchange mechanims. Among the five kinetic models examined (),Table, 2 the Elovich equation gave the best fit of the experimental data (R² = 0.93 to 0.97, standard error = 0.35 to 0.94). The sorption rate constant (α) for both anions was related to the organic matter (OM) content of the soils, especially the content of Al- and Fe-humus complexes. The α values for molybdate were 2.24x10(15) mmol kg-1 h-1 for the Vilcun soil (15% OM), 2.49 x10(12) mmol kg-1 h-1 for the Pemehue soil (16% OM), 8.76x10(10) mmol kg- h-1 for the Osorno soil (20% OM), and 3.11x10(7) mmol kg-1 h-1 for the Piedras Negras soil (24% OM). The corresponding values for phosphate were 3.89x10(7), 5.21x10¹ , 3.11 x10(12) and 1.08x10(16) mmol kg-1 h-1. The desorption rate constant (β) for the four soils (in the above order) ranged from 0.47 to 0.28 for molybdate, and 0.22 to 0.39 mmol kg-1 h-1 for phosphate. The results suggest that the mineralogical composition and organic matter content of the Andisols control the kinetics for the sorption of both molybdate and phosphate. Molybdate appeared to have a high affinity for Fe- and Al-oxides, while phosphate was largely sorbed to Fe-and Al-humus complexes.
author	Vistoso G,Erika Marina Bolán,Nanthi S Theng,Benny K. G Mora,María de la Luz
author_facet	Vistoso G,Erika Marina Bolán,Nanthi S Theng,Benny K. G Mora,María de la Luz
author_sort	Vistoso G,Erika Marina
title	KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS
title_short	KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS
title_full	KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS
title_fullStr	KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS
title_full_unstemmed	KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS
title_sort	kinetics of molybdate and phosphate sorption by some chilean andisols
publisher	Sociedad Chilena de la Ciencia del Suelo
publishDate	2009
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-27912009000100005
work_keys_str_mv	AT vistosogerikamarina kineticsofmolybdateandphosphatesorptionbysomechileanandisols AT bolannanthis kineticsofmolybdateandphosphatesorptionbysomechileanandisols AT thengbennykg kineticsofmolybdateandphosphatesorptionbysomechileanandisols AT moramariadelaluz kineticsofmolybdateandphosphatesorptionbysomechileanandisols
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KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS

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