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dc.contributor.author Pretorius, PJ en_US
dc.contributor.author Linder, PW en_US
dc.date.accessioned 2007-02-06T13:36:09Z en_US
dc.date.accessioned 2007-06-07T10:01:43Z
dc.date.available 2007-02-06T13:36:09Z en_US
dc.date.available 2007-06-07T10:01:43Z
dc.date.copyright en_US
dc.date.issued 2001-07 en_US
dc.identifier.citation Pretorius, PJ and Linder, PW. 2001. The adsorption characteristics of delta-manganese dioxide: a collection of diffuse double layer constants for the adsorption of H+, Cu2+, Ni2+, Zn2+, Cd2+ and Pb2+. Applied Geochemistry, vol. 16, 10 September, pp 1067-1082 en_US
dc.identifier.issn 0883-2927 en_US
dc.identifier.uri http://hdl.handle.net/10204/1555 en_US
dc.identifier.uri http://hdl.handle.net/10204/1555
dc.description.abstract Thermodynamic data for all fate-determining processes are needed in order to predict the fate and transport of metals in natural systems. The surface complexation properties of a synthetic MnO2, delta -MnO2, have accordingly been investigated using glass electrode potentiometry. Experimental data were interpreted according to the surface complexation model in conjunction with the diffuse double layer model of the solid/solution interface. Adsorption constants were determined using the non-linear optimisation program FITEQL. Surface complexation parameters determined in this way were validated against results obtained from the literature. Best fits of alkalimetric titration data were obtained with a 2-site, 3 surface-species model of the delta -MnO2 surface. Site concentrations of 2.23 x 10(-3) mol g (-1) and 7.66 x 10(-4) mol g (-1) were obtained. Corresponding logarithms of formation constants for the postulated surface species are -1.27 (=XO-), -5.99 (=YO-) and 3.52 (=YOH2+) at I = 0.1 M. The surface speciation of delta -MnO2 is dominated by =XO- over the pit range investigated. Metal adsorption was modelled with surface species of the type =XOM+, =XOMOH, =YOM+, =YOMOH (M = Cu, Ni, Zn, Cd and Pb) and =XOM2OH2+ (M = Pb). For Cu, Ni and Zn, titration data could be modelled with =XOM+, =XOMOH, =YOM+ and =YOMOH, whereas for Cd, =XOM+ and =YOM+ were sufficient. Lead data were best modelled by assuming the dinuclear species =XOM2OH2+ to be the only surface species to form. Adsorption constants determined for Ni, Cu and Zn follow the Irving-Williams sequence. The model suggests an adsorption order of (Pb, Cu) > (Ni, Zn) > Cd. The discrepancy between model predictions and published adsorption results is similar to the variability observed in experimental results from different laboratories. en_US
dc.format.extent 388868 bytes en_US
dc.format.mimetype application/pdf en_US
dc.language.iso en en_US
dc.publisher Pergamon-Elsevier Science Ltd en_US
dc.rights Copyright: 2001 Pergamon-Elsevier Science Ltd en_US
dc.source en_US
dc.subject Glass electrode potentiometry en_US
dc.subject Dinuclear species en_US
dc.subject Potentiometric titrations en_US
dc.subject Applied Geochemistry en_US
dc.title Adsorption characteristics of delta-manganese dioxide: a collection of diffuse double layer constants for the adsorption of H+, Cu2+, Ni2+, Zn2+, Cd2+ and Pb2+ en_US
dc.type Article en_US


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