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Carol J. Lind

Publications and source records attributed to Carol J. Lind.

10 recordsLinked to original sources
USGS2002

Hausmannite (Mn 3 O 4 ) conversion to manganite (γ-MnOOH) in dilute oxalate solution

Oxalic acid retards the alteration of Mn3O4 to γ-MnOOH during aging at pH 7.4 ?? 0.2 in well-aerated, abiotic suspensions that contain 4.4 ?? 10-3 M total Mn. In solutions of 1.25 ?? 10-3 M oxalate and greater, about 15% of the initial Mn3O4 altered to ??-MnOOH by day 10, and in solutions of 6.7 ?? 10-4 M oxalate, about 45% altered to ??-MnOOH by day 67. Although precipitation continued through day 365, the degree of conversion remained the same as at day 10 and day 67, respectively. In oxalate-free suspensions, the conversion was about 80% complete by day 67 and 100% by day 109. Oxalate complexed most of the dissolved divalent Mn, lowered the free Mn(II) and MnSO40 concentrations, but increased the total dissolved Mn. Steric hindrance of surface reactions by a suggested manganese oxalate layer on the Mn3O4 surface may explain the blockage of the oxidation cycle.

Environmental Science & Technology↗
USGS1998

In-situ alteration of minerals by acidic ground water resulting from mining activities: Preliminary evaluation of method

The chemical composition of the Cu-mining-related acidic ground water (pH ∼ 3.5 to near neutral) in Pinal Creek Basin, Arizona has been monitored since 1980. In-situ experiments are planned using alluvial sediments placed in the ground-water flow path to measure changes in mineral and chemical composition and changes in dissolution rates of subsurface alluvial sediments. The test results should help refine developed models of predicted chemical changes in ground-water composition and models of streamflow. For the preliminary test, sediment from the depth of the well screen of a newly drilled well was installed in three wells, the source well (pH 4.96) and two up-gradient wells (pHs 4.27 and 4.00). The sediment was placed in woven macrofilters, fastened in series to polyvinyl chloride (PVC) pipes, and hung at the screened level of each well. After interacting with the slowly moving ground water for 48 days, the test sediments were removed for analysis. There was no evidence that any of the materials used were biologically or chemically degraded or that the porosity of the filters was diminished by ferric hydroxide precipitation. These materials included 21-μm-pore (21PEMF) and 67-μm-pore polyester and the 174-μm-pore fluorocarbon Spectra/mesh macrofilters containing the in-situ sediment, the polypropylene (PP) macrofilter support structures, and the Nylon (NY) monofilament line used to attach the samples to the PVC pipe. Based on chemical and mineral composition and on particle-size distribution of the sediment before and after ground-water exposure, the 21PEMF macrofilter was chosen as the most suitable macrofilter for the long-term in-situ experiment. Tests also showed that the PP support structures and the NY monofilament line were sufficiently durable for this experiment.

Arizona↗
USGS1991

Coprecipitation mechanisms and products in manganese oxidation in the presence of cadmium

Manganese oxidation products were precipitated in an aerated open-aqueous system where a continuous influx of mixed Mn 2+ and Cd 2+ solution was supplied and pH was maintained with an automated pH-stat adding dilute NaOH. X-ray diffraction and electron diffraction identified the solids produced as mixtures of Cd 2 Mn 3 4+ O 8 , Mn 2+ 2 Mn 4+ 3 O 8 , MnO 2 (ramsdellite), and CdCO 3 . Mean oxidation numbers of the total precipitated Mn as great as 3.6 were reached during titrations. During subsequent aging in solution, oxidation numbers between 3.8 and 3.9 were reached in some precipitates in less than 40 days. Conditional oxidation rate constants calculated from a crystal-growth equation applied to titration data showed the overall precipitation rate, without considering manganese oxidation state in the precipitate, was increased by a factor of ~4 to ~7 when the mole ratio (Cd/Mn + Cd) of cadmium in the feed solution was 0.40 compared with rate constants for hausmannite (Mn 2+ Mn 2 3+ O 4 precipitation under similar conditions but without accessory metals. Kinetic experiments were made to test effects of various Cd/Mn + Cd mole ratios and rates of addition of the feed solution, different temperatures from 5.0 to 35°C, and pH from 8.0 to 9.0. Oxidation rates were slower when the Cd mole ratio was less than 0.40. The rate increased by a factor of ~10 when pH was raised one-half unit. The effect of temperature on the rate constants was also substantial, but the meaning of this is uncertain because the rate of formation of Mn 4+ oxide in the absence of Cd or other accessory metals was too slow to be measurable in titration experiments. The increased rate of Mn 4+ oxide formation in the presence of Cd 2+ can be ascribed to the formation of a labile adsorbed intermediate, CdMn 2 O 4 Int , an analog of hausmannite, formed on precipitate surfaces at the beginning of the oxidation process. The increased lability of this structure, resulting from coordination-chemical behavior of Cd 2+ during the titration, causes a rapid second-stage rearrangement and facilitates disproportionation of the Mn 3+ ions. The Mn 2+ ions thus released provide a positive feedback mechanism that couples the two steps of the conversion of Mn 2+ to Mn 4+ more closely than is possible when other metal ions besides manganese are not present. During aging of precipitates in contact with solutions, proportions of Cd 2 Mn 3 O 8 and MnO 2 increased at the expense of other precipitate components.

Geochimica et Cosmochimica Acta↗
USGS1989

Coprecipitation and redox reactions of manganese oxides with copper and nickel

Open-system, continuous-titration experiments have been done in which a slow flux of ∼0.02 molar solution of Mn 2+ chloride, nitrate, or perchlorate with Cu 2+ or Ni 2+ in lesser concentrations was introduced into an aerated reactor solution held at constant temperature and at constant pH by a pH-stat titrator that added dilute NaOH. The resulting mixtures of metal oxyhydroxides and their native solutions were aged for periods as long as 2 1/2 years. Fresh and aged precipitates were characterized by chemical analysis, oxidation state determinations, X-ray and electron diffraction, and electron microscopy. The precipitates can be described as mixtures of oxide and oxyhydroxide species, using concepts of equilibrium and nonequilibrium chemical thermodynamics. The metal-ion content of the aged precipitates in systems that contained copper is distributed among three principal components. One of these is a mixed oxide Cu 2 Mn 3 O 8 in which all Mn is in the 4+ oxidation state. A major component in all precipitates is feitknechtite, βMnOOH. These forms are supplemented by CuO or by birnessite or ramsdellite forms of MnO 2 where stoichiometry and thermodynamic calculations predict them. In systems that contained nickel and manganese, identifiable components included βMnOOH, Ni(OH) 2 , and the same two forms of MnO 2 . The oxidation number of the precipitated manganese increased during aging, and the pH of the supernatant solution decreased. The maximum Mn oxidation number observed was 3.55 in an Mn + Cu precipitate aged for 18 months. Concentrations of Cu 2+ and Ni 2+ generally decreased to values substantially below those predicted by oxide or hydroxide equilibrium. Scavenging effects of this type are common in natural aqueous systems.

Geochimica et Cosmochimica Acta↗
USGS1987

Synthesis and stability of hetaerolite, ZnMn2O4, at 25°C

A precipitate of nearly pure hetaerolite, ZnMn 2 O 4 , a spinel-structured analog of hausmannite, Mn 3 O 4 , was prepared by an irreversible wprecipitation of zinc with manganese at 25°C. The synthesis technique entailed constant slow addition of a dilute solution of Mn 2+ and Zn 2+ chlorides having a Mn/Zn ratio of 2:1 to a reaction vessel that initially contained distilled deionized water, maintained at a pH of 8.50 by addition of dilute NaOH by an automated pH stat, with continuous bubbling of CO 2 -free air. The solid was identified by means of X-ray diffraction and transmission electron microscopy and consisted of bipyramidal crystals generally less than 0.10 μm in diameter. Zn 2+ ions are able to substitute extensively for Mn 2+ ions that occupy tetrahedral sites in the hausmannite structure. Hetaerolite appears to be more stable than hausmannite with respect to spontaneous conversion to γMnOOH. The value of the standard free energy of formation of hetaerolite was estimated from the experimental data to be −289.4 ± 0.8 kcal per mole. Solids intermediate in composition between hetaerolite and hausmannite can be prepared by altering the Mn/Zn ratio in the feed solution.

Geochimica et Cosmochimica Acta↗
USGS1985

Thermodynamic stability of CoOOH and its coprecipitation with manganese

A precipitate of cobalt oxyhydroxides formed by bubbling oxygen through a dilute solution of Co(NO 3 ) 2 held at pH 9.0 and 25°C was aged for 23 months in contact with the original solution, with access to atmospheric oxygen. Co 3 O 4 and CoOOH were identified in the precipitate by X-ray diffraction. Chemical equilibria involving these solids were evaluated by measurements of solution pH and Co 2+ activities and by redox potential measurements and gave a ΔG coOOH 0 "> ΔGcoOOH0 of −92.3 ± 0.5 kcal/mole "> −92.3 ± 0.5 kcal/mole . This value and other thermodynamic data show relative feasibility of hypothetical reaction steps and changes in reaction paths during automated coprecipitation titrations and subsequent aging of a precipitate that finally contained βMnOOH, MnO 2 (birnessite) and CoOOH.

Geochimica et Cosmochimica Acta↗
USGS1974

Kaolinite synthesis at 25°C

The addition of quercetin, an organic flavone (C 15 H 10 O 7 ), to aqueous solutions containing silica and aluminum and adjusted to final p H's from 6.5 to 8.5 produced a 1 : 1 alumninosilicate precipitate which, after 6 to 16 months of aging in solution at 25°C, contained as much as 5 percent well-formed kaolinite plates. Similar solutions containing no organic material produced relatively amorphous precipitates with the same composition and stability (standard free energy of formation = -897±1 kilocalories per mole) but with substantially smaller amounts of crystaline material even after 2 years of aging.

Science↗
USGS1973

Chemical interactions of aluminum with aqueous silica at 25 degrees Celsius

Solutions containing from 10 -5 to 10 -2 moles per liter of aluminum and dissolved silica in various ratios were aged at pH levels between 4 and 10 at 25?C. A colloidal amorphous product having the composition of halloysite was produced in most solutions. It had a consistent and reversible equilibrium solubility equivalent to a standard free energy of formation of -8974 ? 1.0 kcal per mole for the formula A12Si2O5(OH)4. Some aging times were longer than 4 years, but most solutions gave consistent solubilities after only a few months of aging. Where silica concentrations were below about 10 -4 molar, microcrystalline gibbsite was formed below pH 6.0 and crystalline bayerite above pH 7.0, but only after much longer aging than was required for crystallization in silica-free solutions. Electron micrographs and diffraction patterns of the synthesized material indicate some crystallinity in the aluminosilicate, but no X-ray diffraction patterns could be obtained even in the material aged 4 years. Solubility relationships for solutions containing fluoride as well as silica and aluminum are explainable by using cryolite stabilities determined in previous work. Aluminum contents of 51 samples of water analyzed for other purposes are in reasonable agreement with the assumption of equilibrium with amorphous clay mineral species similar to the material synthesized in this work. Solubility calculations are summarized graphically for solutions of ionic strength of 0.01 and 0.10.

Water Supply Paper↗