ADSORPTION OF LEAD(II) ON THE GOETHITE SURFACE - VOLTAMMETRIC EVALUATION OF SURFACE COMPLEXATION PARAMETERS

被引:70
作者
MULLER, B
SIGG, L
机构
[1] FED INST WATER RESOURCES,CH-8600 DUBENDORF,SWITZERLAND
[2] WATER POLLUT CONTROL,CH-8600 DUBENDORF,SWITZERLAND
关键词
D O I
10.1016/0021-9797(92)90187-Q
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The adsorption of Pb(II) to the goethite surface was investigated in dilute solutions in the pH range 6.6-8.2. Increments of goethite suspension were added to dilute (2.41 × 10-7M) Pb(II) solutions at constant pH in a titration procedure. Differential pulse anodic stripping voltammetry (DPASV) was used to determine the concentration of free, nonadsorbed Pb(II) in goethite suspensions without prior separation of the solution and solid phases. This procedure permits achievement of high adsorption density at relatively low total metal concentrations and correction for adsorption losses to the reaction vessel. Surface reaction parameters were obtained using different methods of interpretation of the experimental data. Surface complex formation constants for monodentate and bidentate surface complexes are FeOOH + Pb+2 ⇄ FeOOPb++H+, log KS1= -0.52, 2 FeOOH + Pb+2 ⇄(FeOO)2Pb+2H+, log βS2= -6.27 kg dm3 Intrinsic acidity constants obtained from acid-base titrations are, respectively, log Kal5 = -6.7, and log Ka25 = -9.0; the exchangeable H+ of the goethite surface was determined as 0.135 mole/kg. The Pb(II) adsorption capacity of the goethite is 5.6 × 10-2 mole/kg (3.8 × 10-6 mole/m2). The average ligand number was found to be 1.25 and constant throughout the concentration range of adsorption. The determined surface reaction parameters describe the effect of changes in pH and solution composition on Pb(II) binding and give a consistent and comprehensive thermodynamic description of the adsorption process within variations of Pb(II) concentration and particles by factors of 3000 and 1000, respectively. The methods developed here can readily be applied to the determination of adsorption parameters of natural particulate matter. © 1992.
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页码:517 / 532
页数:16
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