Selectivity of the Cd2+/Ca2+ exchange on modified rice hull silica.
The rice hull ash is composed by 94% of SiO2, an agricultural waste that can be recovered and purified by a depolymerization reaction yielding an organo-silicic gel. The purpose of this paper is to show that this silica can be used to fix Cd2+ from aqueous solution. The pH of hydrolysis of the organo-silicic gel is the main factor modifying the distribution between the solid and the solution. The contact time between the Cd2+ solution and the solid was studied to optimize the sorption conditions. The equilibrium measurements were performed after 40 hours at room temperature. The competition with Ca2+ ions in the solutions was also studied in order to evaluate the selectivity of the Cd2+ fixation. It was found that the rice hull ash has a higher capacity to fix Cd2+ than the rice hull derivatives.
Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, México D. F., Mexico.
Norma A
NA
Sánchez-Flores
Marcos
M
Solache
M Teresa
MT
Olguín
José J
JJ
Fripiat
Graciela
G
Pacheco-Malagón
José M
JM
Saniger
Silvia
S
Bulbulian
D000327:Adsorption; D002104:Cadmium / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D012275:Oryza / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013997:Time Factors; D014865:Waste Disposal, Fluid; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry
D014874:Water Pollutants, Chemical; D002104:Cadmium; D014867:Water; D012822:Silicon Dioxide; D002118:Calcium