Shas V. Mattigod

Improved method for estimating the standard free energies of formation (ΔGf,298.150) of smectites

Abstract Two alternative empirical methods were developed for estimating the standard free energies of formation of layer silicate minerals with cation exchange capacity due to isomorphous substitutions. These methods involve the summation of either hydroxide or oxide components to form the desired smectite mineral similarly to a method developed by Nriagu, but differ in that (1) no ad hoc ‘calibrations’ are necessary for the ΔG f,298.15 0 values of alkali hydroxides and (2) a three-parameter equation is used for the correction factor, with the charge on the mineral due to isomorphous substitutions and the ionic radius and charge on the exchangeable cation taken as independent variables. A comparison between experimental and estimated ΔG f,298.15 0 values indicated that one of the methods (that involving the summation of hydroxide components) was significantly better than all other methods in predicting ΔG f,298.15 0 values of smectites while at the same time requiring no ad hoc thermochemical assumptions.

Effect of iron-pair formation on boron adsorption by kaolinite

Boron adsorption on 2-0.2-µm size fractions of kaolinite at 25° ± 2°C at pH values between 6.0 and 10.5 was studied. The kaolinite sample was pretreated to remove any surface oxide and hydroxide coatings. The initial concentrations of boron in solution ranged between 2 and 10 mg/liter with either KClO4 or Ca(ClO4)2 as background electrolyte at constant ionic strength of 0.09 ± 0.01 mole/liter. Boron speciation in equilibrium solutions was calculated by using the chemical equilibrium computer program GEOCHEM. The adsorption of boron on kaolinite in either medium showed similar dependence on pH and initial boron concentrations. Boron adsorption at higher pHs was noticeably higher in Ca(ClO4)2 medium as compared to KClO4 medium. These differences were attributed to the formation and adsorption of CaB(OH4)+ ion-pair species.

Ideal behavior in Na (super +) -trace metal cation exchange on Camp Berteau montmorillonite

The conditions under which an exchanger phase will behave as an ideal mixture are established from thermodynamic principles. It is shown that, if a stoichiometric cation-exchange reaction is reversible, the exchanger phase will exhibit ideal behavior if the Vanselow selectivity coefficient is independent of the exchanger composition. This criterion is applied to some recently published data for Na+-trace metal cation exchange on Camp Berteau montmorillonite. An analysis of the data suggests that, so long as the exchange process is reversible, Na+-trace metal cation exchange produces an exchanger phase that behaves as an ideal mixture.РезюмеИсходя из термодинамических принципов, были установлены условия, при которых обменная фаза ведет себя как идеальная смесь. Показано, что если стехиометрическая реакция катионного обмена является обратимой, обменная фаза прявляает свойства идеальной смеси при условии, что коэффициент селективности Ванселоу является независимым от обменного состава. Этот критерий применим к некоторым недавно опубликованным данным, касающимся катионного обмена рассеяанных металлов с Na+ в монтмориллоните Кэмп Бертеау. Анализ Данных показал, что до тех пор пока процесс является обратимым, в результате катионного обмена Na+ с рассеянными металлами образуется обменная фаза, которая ведет себя как идеальная смесь.ResümeeDie Bedingungen, unter denen sich eine Austauschphase wie eine ideale Mischung verhält, werden aus thermodynamischen Prinzipien aufgestellt. Es wird gezeigt, daß, wenn eine stöchiometrische Kationenaustauschreaktion umkehrbar ist, die austauschphase ideales Verhalten zeigt, falls der Vanselow Selektivitätskoeffizient unabhängig von der Zusammensetzung der Austauschers ist. Dies Kriterium wird auf einige, vor kurzem veröffentlichte Daten für Na+-Spurenmetallkationen- austausch mit Camp Berteau Montmorillonit angewendet. Eine Analyse der Daten schlägt vor, daß solange wie der Austauschvorgang umkehrbar ist, Na+-Spurenmetallkationenaustausch eine Austauschphase produziert, die sich wie eine ideale Mischung verhält.RésuméLes conditions sous lesquelles une phase d’échange se comportera comme un mélange idéal sont établies à partir de principes thermodynamiques. Il peut être démontré que si une réaction stoichiométrique d’échange de cation est réversible, la phase d’échange montrera un comportement idéal si le coefficient de sélectivité Vanselow est indépendant de la composition de l’élément échangeur. Ce critère est appliqué à des données récemment publiées concernant l’échange de cation du métal traceur-Na+ sur de la montmorillonite Camp Berteau. Une analyse des données suggère que, tant que la processus d’échange est réversible, l’échange de cation du métal traceur-Na+ produit une phase d’échange se comportant comme un mélange idéal.

Scheme for density separation and identification of compound forms in size-fractionated fly ash

Abstract A scheme has been developed for the separation of compounds in size-fractionated fly ash by linear density gradients. Minor crystalline components such as calcium ferrite, haematite, magnetite, MgO, barite, anhydrite, rutile and mica were identified in addition to the major compounds mullite, quartz and CaO in a fly ash of pulverized subbituminous coal from western USA. The utility of the scheme in identifying minor crystalline components in fly ash has been demonstrated.

Adsorption of molybdate anion (MoO 4 (super 2-) ) by sodium-saturated kaolinite

Adsorption of Mo(VI) on 2-0.2-μm size fraction of sodium-saturated kaolinite at 25 ± 2°C and at a constant pH of 7.00 ± 0.05 was studied. The kaolinite sample was pretreated to remove any surface oxide and hydroxide coatings. The initial concentrations of Mo in solution ranged from 1 to 11 mg/liter in a NaClO4 background electrolyte at a constant ionic strength of 0.09 ± 0.01. Calculations of speciation using the GEOCHEM computer program indicated that under experimental conditions Mo(VI) was mainly in the MoO42− form. The experimental conditions were also shown to fulfill the requirements for applying the Langmuir equation in interpreting adsorption data. The Langmuir parameter for the adsorption maximum, n°, and the affinity parameter,

Chemical Modeling of Trace Metal Equilibria in Contaminated Soil Solutions Using the Computer Program GEOCHEM

K_{MoO_{4^{2-}}-ClO_{4^{-}}}

Estimated Association Constants for Some Complexes of Trace Metals With Inorganic Ligands

KMoO42−−ClO4− were computed to be 3.33 × 10−4 mole/ mole of adsorbent and 5.969 × 105, respectively. The large affinity parameter indicated that the Na-saturated kaolinite surface has a very high affinity for MoO42− ions relative to ClO4− ions.РезюмеИсследовалась адсорбция Mo(VI) на фракции размером 2-0,2 μм каолинита, насыщен-ного натрием при температуре 25 ± 2°C и при постоянной величине рН равной 7,00 ± 0,05. Образец каолинита обработывался так, чтобы удалить все окисные и гидроокисные поверх-ностные покрытия. Начаьные концентрации Мо в растворе распределялись от 1 до 11 мг/литр в электролите NaClO4 при постоянной ионовой силе равной 0,09 ± 0,01. Вычисления количества новых вилов при помощи програмы ГЭОХЕМ указывали на то, что в этих экспериментальных условиях Mo(VI) находился в основном в форме MoO22−. Показано, что экспериментальные условия выполняли необходимые условия для использования уравнения Лангмюра для интерпретации данных адсорбции. Параметр Лангмюра для максимума адсорбции, n0, и параметр подобия,