CENTRO DE TECNOLOGIA DE RECURSOS MINERALES Y CERAMICA
Unidad Ejecutora - UE
Use of modified hydroxy aluminium bentonite for chromium II removal from solutions
C. VOLZONE; L.B. GARRIDO
JOURNAL OF ENVIRONMENTAL MANAGEMENT
The retention of chromium(III) from a 2000 ppm chromium basic sulfate and tannery waste solution at pH 4.5 using modified hydroxy-aluminum bentonites (OH-Al bentonites) as adsorbents was studied. OH-Al bentonite was prepared by mixing clay with a hydrolyzed commercial chlorohydroxy Al solution. The modified Al bentonites were obtained by (a) a treatment with 0.5M sodium chloride and (b) a treatment with a Na-hexametaphosphate solution (HMP) after adding sodium chloride. The effect of heating the adsorbents at 100, 500, 700 and 800 ºC on Cr retention as a function of time was also analyzed. Cr retention by modified OH-Al bentonite with HMP increased with time (up to 100 mgCr/g) where modified OH-Al bentonite was twice that of untreated bentonite. The relatively high uptake of metal from the salt solution by modified OH-Al bentonite treated at 800 ºC, in which a complete interlayer collapse occurred, indicated the importance of the contribution of external surface sites to the retention capacity. The maximum Cr uptake from a water waste was 24 mg/g, due to interferences and different chromium species in the industrial solution.