2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 5
Presentation Time: 8:00 AM-6:00 PM

Sorption of Cu2+, Pb2+, Cr3+, Zn2+, Hg2+, Ni2+, Ag+, Mn2+, Cd2+ and NH4+ by Clinoptilolite Tuff and Montmorillonite Clay and Their Ca-Enriched Types

ABATAL, Mohamed1, DE PABLO, Liberto1, CHAVEZ, Lourdes2, GARCIA, Tania1, CRUZ, Carmina2 and COVARRUBIAS, Banjamin2, (1)Instituto de Geologia, Universidad Nacional A. de Mexico, Ciudad Universitaria, Mexico D.F, 04510, Mexico, (2)Facultad de Quimica, Universidad Nacional A. de Mexico, Ciudad Universitaria, Mexico D.F, 04510, Mexico, liberto@servidor.unam.mx

Sorption of heavy metals and NH4+ by clinoptilolite tuff from Oaxaca, Mexico, containing 55 % clinoptilolite, CEC 1.07 meq/g, adsorbs from 0.1 N solutions Cr3+ 0.121 mg/g, Ni2+ 0.147, Cu2+ 0.603, Mn2+ 0.990, Zn2+ 1.045, Hg2+ 1.303, Cd2+ 1.855, NH4+ 5.742, Pb2+ 10.877 and Ag+ 17.366 mg/g. Adsorption by Ca2+-exchanged tuff increases to Cr3+ 2.507 mg/g, Ni2+ 4.609, Cu2+ 6.545, Mn2+ 5.274, Zn2+ 5.608, Hg2+ 21.965, Cd2+ 13.600, NH4+ 13.464, Pb2+ 25.795 and Ag+ 41.691 mg/g. Selectivity Ag+>NH4+>Pb2+>Cd2+>Hg2+>Cu2+>Mn2+>Zn2+>Cr3+>Ni2+. Sorption from cation+Ca2+ solutions 0.1 to 0.005 N follows the Langmuir model establishing maximum sorptions by the natural tuff of Cr3+ 3.180 mg/g, Ni2+ 4.135, Cu2+ 5.282, Mn2+ 2.802, Zn2+ 4.282, Cd2+ 5.302 and Pb2+ 18.336 mg/g, selectivity Pb2+>Cd2+>Cu2+>Zn2+>Ni2+>Cr3+>Mn2+. Ca-saturation improves sorption of Cu2+ by 7.08 %, Pb2+ 8.60 % and Ni2+ 25.66 % but reduces Cr3+ by 19.87 %, Zn2+ 1.33 %, Mn2+ 44.61 % and Cd2+ 40.11%. Cation and Ca2+ are adsorbed simultaneously at levels below the CEC of the tuff without precipitation of hydroxy complexes. Ca2+ does not limit the adsorption of cation, rather it eases and stabilizes their sorption.

Sorption by clay containing 85 % montmorillonite, CEC 0.69 meq/g adsorbs from 0.1 N solutions less than 1 meq/g of Ba2+, Mn2+, K+ and Cd2+, between 1.409-1.559 meq/g of Ag2+ and Ni2+, 3.293-3.730 meq/g of Pb2+ and Hg2+, Cu2+ 4.341 meq/g, Cr3+ 4.117 meq/g and Zn2+ 4.104 meq/g. Selectivity Cu2+>Cr3+>Zn2+>Hg2+>Pb2+>Ni2+>Ag2+>Ba2+>Mn2+>K+>Cd2+. Maximum sorptions from 0.1 N solutions of cation + Ca2+ by montmorillonite are Hg 31.74 mg/g, Zn2+ 20.84, K+ 14.48, Cd2+ 9.86, Ni2+ 8.27, Ba2+ 6.59 and Mn2+ 3.82 mg/g; by Ca2+-exchanged montmorillonite they are Zn2+ 39.61 mg/g, K+ 16.62, Ba2+ 14.61, Ni2+ 11.98 and Cd2+ 11.35 mg/g. Cr3+, Cu2+ and Pb2+ precipitate and immobilize leaving solutions free of metal but enriched in Ca2+ desorbed from the clay.