Adsorption of aqueous Pb(II) and Cu(II) on a-quartz was determined as a function of time, system surface area, and chemical speciation. The experimental work also included the investigation of the adsorption behavior of the doubly charged major cations Ca(II) and Mg(II) as a function of pH. The biggest problem in the theoretical predictions of the adsorption behavior of Cu(II) was the lack of reliable data for the.
ADSORPTION OF Cu(II), Pb(II), Mg(II) AND Ca(II) ON rv-QUARTZ IN A CARBONATE-FREE SYSTEM. 1 Adsorption of Cu(II) and Pb(II) on a-quartz as a function of time, concentration of metal ions and surface area of the system. 2 Adsorption of Cu(II) and Pb(II) on rv.-quartz depending on the concentration of metals and.
Specific adsorption potential for a-quartz used for modeling the experimental systems with the James-Healy model. Locations of a metal ion in the bilayer of the Oxide-Water interface according to the James-Healy Model Free energies of adsorption of charged and uncharged Me(II) species on Fe(OH).
Equilibrium determination of Cu as a function of pH in the solution: CuT=10-6M, I=lo-3, carbonate-free. Speciation of Pb(II) in natural freshwater as a function of pH in the presence of 1. 4 Speciation of Co(II) in natural freshwater as a function of pH in the presence of l.
6 Zn(II) speciation in natural freshwaters as a function of pH in the presence of 1. 7 Distribution of Cd(II) in natural freshwaters as a function of pH in the presence of 1. Metal distribution in natural freshwaters in the presence of different amounts of aspartic acid.
2 (s) in fresh oxidizing waters with pH 7 as a function of surface area (ha/-t) in the presence and absence of citrates. 2 (s) in fresh oxidizing waters with pH 7 as a function of surface area (hat-t) in the presence and absence of citrates.
2 [Me(OSi=)
Schindler and Kamber (1968), Stumm, Huang, and Jenkins (1970), and Block and DeBruyn (1970a, 1970b) also observed the electrostatic influence of the charge groups on the departing protons. Lohman (1972) found that if one looks at the adsorption of the ions by the oxide/. The acidity constant of the surface OH groups must be corrected for the presence of the electric field.
35, and values for the acidity constant of the surface OH groups, corrected for the presence of an electric field (equation 2. 36). It can enhance adsorption due to surface affinity along with strong complexation with metal ions. If the amount of adsorption of a hydrolyzable metal ion is plotted as a function of pH, we see a very strong increase in adsorption at a given pH.
Consequently, the addition of either ligand decreases the adsorption by reducing the concentration of the free metal ion. The reported stability constants for each of the species differ by about three orders of magnitude. 2 S remaining after leaching from CuS by heavy use of the electrode (Blaedel and Dinwiddie (1974)).
7 and assuming the Nernstian behavior of the electrodes at the indicated pH values and Cu 2+ concentrations.
ADSORPTION OF Cu(II), Pb(II), Mg(II) AND Ca(II) ON a-QUARTZ IN A CARBONATE-FREE SYSTEM. 1 Adsorption of Cu(II) and Pb(II) on ex-Quartz as a function of time, metal ion concentration and system surface area. The rate of adsorption of metal ions is a function of both the surface (its chemical properties and physical structure) and the metal ion involved. 1968) observed a very rapid adsorption of the alkaline earth and the transition metal ions on o-Mn0.
Gadde and Laitinen (1974) reported a 3-h equilibration time between hydrous manganese oxide and Pb(II), Cd(II), Zn(II), and Tl(I). 1968) found that the final attainment of equilibrium was between manganese (II) manganite and Ni(II), Cu(II) and Co(II). The time required for the establishment of the equilibrium between Co(II) and quartz is 3 hours (Healy et al. In the present study it was found that the equilibration time between Cu(II) and Pb(II) and quartz is very fast .
2 Adsorption of Cu(II) and Pb(II) on a-Quartz as a function of metal concentration and system surface area. At equilibrium, the amount of adsorbed metal ion, at a fixed pH and ionic strength, is a function of the total concentration of the metal and the available surface area. 2 Adsorption of Cu(II), Pb(II), Mg(II) and Ca(II) on a-quartz as a function of pH and ionic strength.
The addition of more electrolyte at a constant pH results in the compression of the electrical doublet. In the forthcoming analyzes of the experimental systems, the discussions, unless otherwise stated, correspond to the calculations done with the James-Healy model. At both low and high pH values, changes in the ionic strength have no major influence on the adsorption of Cu(II) on Si0.
In terms of the ion exchange–surface complex formation model, a higher hydrolysis constant implies a shift in the equilibrium. In the pH range of normal Pb(II) adsorption on a-quartz, Pb(II) remains attached to the surface (Figure 5. 19b). Modeling of the adsorption behavior of Pb(II) in the presence of different amounts of citrate with the Ion-Exchange-Surface Complex Formation Model is shown in Figure 5 .
An increase in ionic strength results in a shift of the adsorption edge towards a higher pH. Therefore, in this chapter we study the adsorption of Pb(II) and Cu(II) on SiO2 in the presence of one of the most common ligands in natural waters: carbonate. In the James-Healy model, any species with zero charge can be readily adsorbed if given l:IG h 0 .
Modeling the experimental systems with the Ion Exchange-Surface Complex Formation Model turned out to be unsatisfactory in the case of Cu(II) adsorption on o:-quartz, because the model only considers the adsorption of free metal ions. The values for the chemical free energies of metal adsorption were either determined in the present study or taken from the results of. The equilibrium distributions of trace metals in oxic fresh water at pH 7 in the presence of 1.
8 Speciation of Hg(ll) in natural freshwater as a function of pH in the presence of 1.
The speciation of Fe(III), Ni(II) and Cd(II) is influenced by the presence of citrate at. The speciation of Pb(II) is affected by histidine only at concentrations of HIST>lOPbT, the most important effect being a decrease in the concentrations of Pb 2+ and Pb-C0. The effect of histidine on the speciation of Ni(II), Cd(II), Co(II), and Zn(II) becomes evident at concentrations of HIST>O.
HgCI
PbCO
CuOH
PbAOS 8 .0
