title: Adsorption of Ba2+ by Ca-exchange clinoptilolite tuff and montmorillonite clay.
abstract: The adsorption of barium by Ca-exchanged clinoptilolite and montmorillonite is presented. The kinetics of adsorption of Ba(2+) were evaluated contacting 1g portion of each adsorber with 100mL 0.1N BaCl(2) for 200 h. Adsorption by Ca-clinoptilolite is defined by second-order kinetics of rate constant K(v) 8.232 x 10(-2) g mg(-1)h(-1) and maximum removal of 71.885 mg g(-1). It is a two-stage process initiated by a rapid uptake of Ba(2+) followed by more moderate kinetics. The adsorption isotherms were determined contacting 0.2g of each adsorber with 10 mL 0.1-0.005N BaCl(2)+CaCl(2) solution, Ba(2+)/Ca(2+) ratio 1, for periods of 7 days for the tuff and 2 days for the clay. The equilibrium adsorption is described by the Langmuir model, of equilibrium constant K 0.0151 L mg(-1) and maximum adsorption of 15.29 mg g(-1). The adsorption of Ba(2+) by Ca-exchanged montmorillonite also follows a second-order reaction of rate constant K(v) 3.179 x 10(-2) g mg(-1)h(-1), and calculated separation of 36.74 mg g(-1); the Langmuir isotherm is defined by the constant K 0.034 L mg(-1) and maximum adsorption of 15.29 mg g(-1). X-ray diffraction shows that the exchange of Ba(2+) modifies the d(001) of Ca-montmorillonite from 15.4 to 12.4A.
authors.affiliation: Facultad de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, 04510 México, DF, Mexico. marilu@servidor.unam.mx
authors.forename: M L
authors.initials: ML
authors.lastname: Chávez
authors.forename: L
authors.initials: L
authors.lastname: de Pablo
authors.forename: T A
authors.initials: TA
authors.lastname: García
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates; D001464:Barium / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D000077215:Clay; D006358:Hot Temperature; D007700:Kinetics; D013696:Temperature; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D014874:Water Pollutants, Chemical; C083175:clinoptilolite; D001546:Bentonite; D017641:Zeolites; D001464:Barium; D002118:Calcium; D000077215:Clay