%0 Journal Article
%T KINETICS OF MOLYBDATE AND PHOSPHATE SORPTION BY SOME CHILEAN ANDISOLS Cin谷tica de adsorci車n de molibdato y fosfato en algunos Andisoles chilenos
%A Erika Marina Vistoso G
%A Nanthi S Bol芍n
%A Benny K. G Theng
%A Mar赤a de la Luz Mora
%J Revista de la Ciencia del Suelo y Nutrici車n Vegetal
%D 2009
%I 
%X 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 (汐) for both anions was related to the organic matter (OM) content of the soils, especially the content of Al- and Fe-humus complexes. The 汐 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 (汕) 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. Se determinaron las cin谷ticas de adsorci車n de molibdato y fosfato en cuatro Andisoles Chilenos. Cerca del 55% del molibdato y 61% del fosfato fueron adsorbidos en las primeras 0,5 h; despu谷s la adsorci車n aument車 lentamente, donde se adsorbi車 aproximadamente el 90% del molibdato y el 97% del fosfato despu谷s de 72 h. Al mismo tiempo, aument車 la concentraci車n de iones OH‘ en la soluci車n de suelo, aumentando el pH en 0,85 unidades para molibdato y en 0,65 unidades en el caso de fosfato. Estas observaciones indican que ambos aniones son adsorbidos por el mecanismo de intercambio de ligandos. Entre los cinco modelos cin谷ticos examinados (Tabla 2), la ecuaci車n de Elovich mostr車 los mejores ajustes de los datos experimentales (R2 = 0,93 a 0,97; SE = 0,35 a 0,94). La velocidad de adsorci車n (汐), para ambos aniones, se relacion車 con el contenido de materia org芍nica (MO) de los suelos, especialme
%K Oxido de Al y Fe
%K andisoles chilenos
%K modelo cin谷tico
%K molibdato y fosfato
%K Al- and Fe-oxide
%K Chilean Andisols
%K kinetic model
%K molybdate and phosphate
%U http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-27912009000100005