Aqueous and Surface Chemistry of Calcium - Metal Hydroxides in High pH Environments

1996 ◽  
Vol 432 ◽  
Author(s):  
David L. Cocke ◽  
M. Yousuf ◽  
A. Mollah ◽  
Thomas R. Hess ◽  
Tien-Chih Lin
Keyword(s):  
Water System ◽  
Empirical Method ◽  
Ion Concentration ◽  
Early Hydration ◽  
High Ph ◽  
Sequential Structure ◽  
Zinc Cadmium ◽  
Pitzer Parameters ◽  
Calcium Metal ◽  
Cadmium And Lead

AbstractMixed hydroxides of calcium, zinc, cadmium and lead have been recently identified in the high pH environments of hydrating cement. FTIR, XRD, SEM, and SPM have been used to characterize these systems. A chemical equilibrium model of the early hydration of a zinc-doped cement/water system, Na-K-Ca-Zn-H-SO4-OH-Zn(OH)2-Zn(OH)3-Zn(OH)4-H2O, has been developed to better understand the mechanism of the surface formation of calcium hydroxyzincate (CHZ). The model is based on Pitzer's semi-empirical method for calculation of ion-activity coefficients at high ionic strength. The Pitzer parameters for Na+-Zn2+,Na+-Zn2+- and have been evaluated, and the results successfully predict the equilibria (solubilities) of Na2SO4-ZnSO4-H2O, NaOH-Zn(OH)2-H2O and KOH-ZnO-H2O systems. The chemical model clearly demonstrates that the formation of CHZ on the calcium-silicahydrate (C-S-H) surface is critically controlled by the Ca2+ ion concentration as well as pH of the pore water system. The results of this study suggest that the growth of CHZ is preceded by surface complex formation. Sequential charge control and sequential structure development have been used to discuss the surface selectivity of these compounds and their control of cement hydration.

Ethylenediamine-N,N′-diacetic acid complexes with divalent manganese, zinc, cadmium, and lead: a thermodynamic study

1979 ◽  
Vol 57 (1) ◽  
pp. 113-118 ◽  
Author(s):  
R. J. Gualtieri ◽  
W. A. E. McBryde ◽  
H. K. J. Powell
Keyword(s):  
Protonation Constants ◽  
Thermodynamic Study ◽  
Diacetic Acid ◽  
Calorimetric Data ◽  
Nmr Studies ◽  
Aqueous Acid ◽  
Manganese Zinc ◽  
Proton Dissociation ◽  
Zinc Cadmium ◽  
Cadmium And Lead

The four protonation constants are reported for the dianion of ethylenediamine-N,N′-diacetic acid(H2L),25°C, I = 0.10 M(KNO3), (log ki = 9.60, 6.51, 2.12, 1.3). log K(potentiometric) and ΔH(calorimetric) data are reported for the formation of the complexes [ML], M = Mn2+, Zn2+, Cd2+, and Pb2+ (log K = 6.87, 10.99, 9.16, and 10.66; ΔH = −2.9, −24.4, −16.7, and −28.0 kJ mol−1 respectively). The complexes [ZnL] and [PbL] undergo (aqua) proton dissociation reactions, [Formula: see text] log KD = −10.56 and −11.02, ΔHD = +60.7 and +38.5 kJ mol−1, respectively. Potentiometric and nmr studies indicate that the ligand undergoes a slow (metal catalysed) hydrolysis or rearrangement in aqueous acid.

scholarly journals A Study into the Localized Corrosion of Magnesium Alloy Magnox Al-80

CORROSION ◽  
10.5006/3574 ◽  
2020 ◽  
Author(s):  
Ronald Clark ◽  
James Humpage ◽  
Robert Burrows ◽  
Hugh Godfrey ◽  
Mustufa Sagir ◽  
...  
Keyword(s):  
Passive Film ◽  
Ph Dependence ◽  
Chloride Concentration ◽  
Ion Concentration ◽  
Localized Corrosion ◽  
High Concentration ◽  
Transfer Resistance ◽  
High Ph ◽  
Intact Surface ◽  
Chloride Concentrations

Magnesium (Mg) non-oxidizing alloy, known as Magnox, was historically used as a fuel cladding material for the first-generation of carbon dioxide (CO<sub>2</sub>) gas-cooled nuclear reactors in the UK. Waste Magnox is currently stored in cooling ponds, pending final disposal. The corrosion resistance of Mg and its alloys is relatively poor, compared to modern cladding materials such as zirconium (Zr) alloys, so it is important to have a knowledge of the chloride concentration/pH dependence on breakdown and localized corrosion characteristics prior to waste retrievals taking place. Our results show that Magnox exhibits passivity in high pH solutions, with charge transfer resistance and passive film thicknesses showing an increase with immersion time. When chloride is added to the system the higher pH maintains Magnox passivity, as shown through a combination of potentiodynamic and time-lapse/post corrosion imaging experiments. Potentiodynamic polarization of Magnox reveals a -229 mV<sup>-decade</sup> linear dependence of breakdown potential with chloride ion concentration. The use of the scanning vibrating electrode technique (SVET) enabled the localized corrosion characteristics to be followed. At high pH where Magnox is passive, at low chloride concentrations, the anodes which form predominantly couple to the visually intact surface in the vicinity of the anode. The high pH however means that visually intact Magnox in the vicinity of the anode is less prone to breakdown, restricting anode propagation such that they remain largely static. In high chloride concentrations the higher conductivity means that the anode and cathode can couple over greater distances and so propagation along the surface can occur at a much faster rate, with the visually intact surface acting as a distributed cathode. In addition, the chloride anion itself, when present at high concentration will play a role in rapid passive film dissolution, enabling rapid anode propagation.

scholarly journals Environmental Impacts of an Old Mine Tailings Deposit – Metal Concentrations and Water Pathways

1987 ◽  
Vol 18 (4-5) ◽  
pp. 301-312 ◽  
Author(s):  
P. Sandén ◽  
S. Karlsson ◽  
U. Lohm
Keyword(s):  
Environmental Impacts ◽  
Mine Tailings ◽  
Water Bodies ◽  
Contaminated Water ◽  
Surrounding Area ◽  
Metal Concentrations ◽  
Principal Source ◽  
Zinc Cadmium ◽  
Copper Zinc ◽  
Cadmium And Lead

Variations in metal concentrations in a heavily polluted stream receiving acidic leachates from an old mine tailings deposit are analysed from a hydrological perspective. From an extensive data material, collected during three years, the variations in concentrations of four metals (copper, zinc, cadmium and lead) are discussed. The deposit is the principal source for these metals in the watershed. The variation in metal concentrations in the vicinity of the deposit can to a large extent be explained by simple dilution of contaminated water with uncontaminated water from the surrounding area. Further downstream the deposit, other processes become increasingly important for the metal concentrations in the water bodies.

Copper substitution alone and in the presence of chromium, zinc, cadmium and lead in goethite (α-FeOOH)

Clay Minerals ◽  
2009 ◽  
Vol 44 (3) ◽  
pp. 293-310 ◽  
Author(s):  
N. Kaur ◽  
B. Singh ◽  
B. J. Kennedy
Keyword(s):  
Dissolution Rate ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
General Sequence ◽  
Cell Parameters ◽  
Molar Ratios ◽  
Zinc Cadmium ◽  
Cadmium And Lead ◽  
Copper Substitution

AbstractA series of Cu-substituted goethites, single and co-substituted with Cr, Zn, Cd and/or Pb was prepared, having molar ratios equal to 2.00, 3.33 and 5.00 mol%. All the samples contained only goethite, except Cu-, (Cu,Zn)- and (Cu,Pb)-samples synthesized at 5.00 mol% where hematite was also formed. The presence of Cr/Cd suppressed the hematite-forming effects of Cu. The general sequence of metal entry into the single-metal-substituted goethites was Zn = Cr > Cd > Cu > Pb and in di- (5.00 mol%) and tri- (3.33 mol%) metal-substituted goethites was Cu > Zn > Cd > Cr >> Pb. Cu incorporation increased all the unit-cell parameters in single-metal-substituted goethite, and these parameters increased in combination with other metals as follows: Cd > Zn > Cr > Pb in the multimetal-substituted goethites. The Cu-substituted goethite dissolved faster than pure goethite. Co substitutions of Cr/Pb reduced the dissolution rate (kFe), while substitutions of Cd/Zn increased kFe.

Zinc concentrations in juvenile flatfish

1979 ◽  
Vol 59 (3) ◽  
pp. 761-775 ◽  
Author(s):  
N. J. Milner
Keyword(s):  
Sea Water ◽  
Chemical Properties ◽  
Estuarine Fish ◽  
Physico Chemical ◽  
Zinc Cadmium ◽  
Iron And Zinc ◽  
Lead Levels ◽  
Zinc Concentrations ◽  
High Concentrations ◽  
Cadmium And Lead

In most demersal and some pelagic marine fish O- and I-group stages are found on inshore nursery grounds which are often situated in coastal indentations and estuarieswhere flushing rates are low and the build up of persistent pollutants can be correspondingly high. Their movements are restricted, only leaving the nursery areas towards the end of their second year (Lockwood, 1974; Riley, 1973). This, coupled with the fact that juveniles may be more susceptible than adults to pollutants, makes them particularly vulnerable to the potential hazards of inshore pollution.The physico-chemical properties of most trace metals, however, generally preclude their occurrence at high concentrations in sea water itself. Instead, most of the metal is transferred to the particulate phase of the water mass and to sedimentary reservoirs (Renfro, 1973) so that concentrations of metals in sea water very rarely reach levels which are known to be acutely toxic to fish. The main risk from direct effects of metals lies in poisoning resulting from internal accumulation.Little information is available on metal concentrations occurring in young fish. Hardisty et al. (1974) and Hardisty, Kartar & Sainsbury (1974) have examined zinc, cadmium and lead levels in O-group and older flounders from the Bristol Channel. Andersen, Dommasnes & Hesthagen (1973) found high concentrations of zinc in O- and I-group herring and sprat from Oslo Fjord, Cross & Brooks (1973) reported on manganese, iron and zinc concentrations in juvenile estuarine fish. Pentreath (1973 b) has reported on zinc concentrations in the organs of I-group plaice.

Heavy metal adsorption changes of EAF steel slag after phosphorus adsorption

2012 ◽  
Vol 65 (9) ◽  
pp. 1570-1576 ◽  
Author(s):  
Guanling Song ◽  
Lijing Cao ◽  
Xiao Chen ◽  
Wenhua Hou ◽  
Qunhui Wang
Keyword(s):  
Heavy Metal ◽  
Metal Ion ◽  
Steel Slag ◽  
Ion Concentration ◽  
Metal Adsorption ◽  
Heavy Metal Ion ◽  
Heavy Metal Adsorption ◽  
Isothermal Adsorption ◽  
Phosphorus Adsorption ◽  
Cadmium And Lead

A kind of electric arc furnace (EAF) steel slag was phosphated, and its isothermal and dynamic adsorptions of copper, cadmium, and lead ions were measured to determine if heavy metal adsorption changes after phosphorus adsorption. The surface area increased greatly after the slag was phosphated. Isothermal adsorption experiments showed that the theoretical Qmax of the EAF steel slag on Cu2+, Cd2+, and Pb2+ improved 59, 50, and 89% respectively after it was phosphated. Dynamic adsorption results showed that the greatest adsorption capacities of unit volume of Cu2+, Cd2+, and Pb2+ were 2.2, 1.8, and 1.8 times that of the column packed with original EAF steel slag when the column was packed with phosphate EAF steel slag at the same heavy metal ion concentration. The breakthrough time, the exhaustion time and elution efficiency of the column also increased when the column was packed with phosphated EAF steel slag compared with that packed with original EAF steel slag. Phosphorus adsorption could further improve the heavy metal ion adsorption of the EAF steel slag.

Effects of high pH solutions with large monovalent cation concentrations on cation exchange properties

Soil Research ◽  
1996 ◽  
Vol 34 (2) ◽  
pp. 229 ◽  
Author(s):  
RE Liefering ◽  
CDA Mclay
Keyword(s):  
Organic Matter ◽  
Cation Exchange ◽  
Negative Charge ◽  
Monovalent Cation ◽  
Exchange Capacity ◽  
Exchangeable Cations ◽  
Ion Concentration ◽  
Exchangeable Sodium ◽  
High Ph ◽  
Exchange Properties

Disposal of strongly alkaline industrial liquid wastes, which contain large monovalent cation concentrations, by means of land treatment systems is becoming increasingly common. This study investigated the effects of solutions with large monovalent cation concentrations and high pH on cation exchange properties in four New Zealand soils with different clay mineralogies. The soils were shaken with a range of concentrations (0–0.3 M) of NaOH, KOH, NaCl, and KCl. Cation exchange capacity (CEC) and exchangeable cations (Ca2+, Mg2+, K+, and Na+) were measured following shaking and washing procedures. Although the hydroxide solutions dissolved significant amounts of organic matter from all soils, there was still a net increase in CEC measured at all hydroxide concentrations. The magnitude of the CEC increase was dependent on hydroxide concentration. The increase in CEC is attributed to newly generated negative charge on surfaces which possess variable charge (i.e. pH dependent) characteristics such as edge sites of clay minerals, sesquioxides, and the undissolved organic matter remaining in the soil. In contrast to hydroxide solutions, no increase in CEC was measured in chloride-treated samples. Increases in the concentration of all treatment solutions resulted in increases in the exchangeable ion concentration of the index cation used in the treatment solution (either Na+ or K+) and decreases in concentration of the other three exchangeable cations. In general, higher exchangeable sodium percentage (ESP) values were measured in samples treated with NaOH than samples treated with NaCl at all concentrations. Similarly, higher exchangeable potassium percentage (EPP) was measured in samples treated with KOH than samples treated with KCl at all concentrations. The higher ESP and EPP values recorded when hydroxide solutions were used as treatments are attributed to the newly generated negative charges being counter-balanced by the monovalent index cation present in the treatment solution. It is suggested that existing equations commonly used to predict ESP and EPP values are unsuccessful for accurately predicting changes when soils are treated with hydroxide solutions, due to their inability to account for the newly generated exchange sites. The equations did, however, adequately predict the effects of both chloride solutions on ESP and EPP.

scholarly journals Eco-Efficient Biosorbent Based on Leucaena leucocephala Residues for the Simultaneous Removal of Pb(II) and Cd(II) Ions from Water System: Sorption and Mechanism

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
C. A. Cimá-Mukul ◽  
Youness Abdellaoui ◽  
Mohamed Abatal ◽  
Joel Vargas ◽  
Arlette A. Santiago ◽  
...  
Keyword(s):  
Leucaena Leucocephala ◽  
Metal Ion ◽  
Water System ◽  
Ion Concentration ◽  
Point Of Zero Charge ◽  
Southern Mexico ◽  
Lead And Cadmium ◽  
Biosorption Process ◽  
Monolayer Adsorption ◽  
Pseudo Second Order

Leucaena leucocephala is a potential source of polyphenols widely available in southern Mexico. This work highlights the extraction of polyphenols from Leucaena leucocephala leaves waste (LLEPs) and the evaluation of their efficiency to remove the single and multicomponent Pb(II) and Cd(II) metal ions from aqueous solutions. Batch test conditions were carried out to examine the effects of contact time, initial metal ion concentration, and adsorbent dosage on the biosorption process. The surface textures and the composition of the LLEP biosorbent was characterized using pH of point of zero charge (pHPZC), attenuated total reflectance Fourier transform infrared (ATR-FTIR), and matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry, respectively. Further analysis using ATR-FTIR after adsorption contact of biosorbent was also investigated. The highest Langmuir saturation monolayer adsorption capacity, qm, for the removal of Pb(II) by LLEPs was obtained as 25.51 and 21.55 mg/g in mono- and bimetal solutions, respectively. The pseudo-second-order model provided the best fit for the kinetic data obtained for the removal of Pb(II), Cd(II), and their mixture, and the k2 values depend on the adsorbent mass. This implied that the chemisorption process might be the mechanism of the solute ions-LLEPs interaction in this study. Furthermore, nearly 100% removal of lead and cadmium individually and 95% of their mixture was found using 0.9 g of LLEPs.

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