Use of modified hydroxy-aluminum bentonites for chromium(III) removal from solutions.
The retention of chromium(III) from a 2,000 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 degrees C 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 mg Cr/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 degrees C, 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.
Volzone
Cristina
C
CETMIC, Centro de Tecnología de Recursos Minerales y Cerámica (CONICET-CIC), C.C. 49, Camino Centenario y 506, M.B. Gonnet, 1897 Provincia de Buenos Aires, Argentina. volzcris@netverk.com.ar
Beatriz Garrido
Liliana
L
D000535:Aluminum / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D002857:Chromium / Q000302:isolation & purification*; D006358:Hot Temperature; D007220:Industrial Waste; D012996:Solutions; D013633:Tanning; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D014961:X-Ray Diffraction
D007220:Industrial Waste; D012996:Solutions; D014874:Water Pollutants, Chemical; D002857:Chromium; D001546:Bentonite; D000535:Aluminum