Kinetics of limestone neutralization of acid waters.

Barton, Paul; Vatanatham, Terdthai

doi:10.1021/es60159a019

Cited by 18 publications

(22 citation statements)

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“…Calcitic limestone (greater than 90% calcite, CaCO 3 ) is by far the most common alkalinity-generating material used in passive treatment. In general, limestone dissolution is self-buffering, providing a pH of about 8 (Barton and Vatanatham, 1976;Rose, 1999), making it is essentially impossible to over treat the ARD. Due to the rapid autooxidation of ferrous iron and low solubility of ferric iron at near-neutral pH, the presence of oxygen and ferric iron in ARD results in the armoring and passivation of limestone.…”

Section: Introductionmentioning

confidence: 99%

Passive Treatment of Low-Ph, Ferric Iron-Dominated Acid Rock Drainage in a Vertical Flow Wetland I: Acidity Neutralization and Alkalinity Generation

Thomas¹,

Romanek²

2002

JASMR

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Abstract. Passive treatment of acid rock drainage (ARD) is typically limited by the chemistry of the ARD. Anaerobic, ferrous iron-dominated ARD can be treated directly with limestone in an anoxic limestone drain (ALD), but alkalinity generation is limited because the high pH (5 -6) reduces limestone solubility. Oxygenated, ferrous iron-dominated ARD cannot be treated directly with limestone due to the potential for armoring by iron oxyhydroxide precipitates. Vertical flow wetlands that rely on biological processes are typically employed. Reducing and alkalinity producing systems (RAPS) are one type of VFW that requires biological pretreatment of ARD to remove oxygen. The biological pretreatment typically adds alkalinity to the ARD, limiting the alkalinity generated in the RAPS via limestone dissolution by lower the solubility of limestone. The low pH (< 3) of oxygenated, ferric iron-dominated ARD is prohibitive to the biological processes typically required for effective passive treatment. In this study, highly oxidized (i.e., 99% Fe 3+ ), low-pH (2.4), ARD is treated with a VFW system amended with fine-grained (1.2 mm) limestonebuffered organic substrate (LBOS). Nearly 100% of the influent acidity (averaged >1300 mg·L -1 ) is neutralized in the LBOS with an average 600 mg·L -1 of additional alkalinity measured in the effluent; total alkalinity generated in the LBOS averages > 1800 mg·L -1. Limestone dissolution accounts for 80 -95% of the total alkalinity generated in the system. Limestone dissolution is very rapid and occurs in a thin (2 -5 cm) dissolution front that advances as the limestone is depleted. Armoring due to iron oxyhydroxide precipitates apparently does not limit limestone dissolution, as limestone consumption above the dissolution front is nearly complete with greater than 85% of the limestone removed; limestone below the front is apparently unaffected. Sizing recommendations are made based on the influent acidity load and the volume of limestone in the LBOS.Additional Key Words: limestone-buffered organic substrate, limestone dissolution, armoring, biological oxidation of organic matter, anaerobic wetland 1

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Section: Introductionmentioning

confidence: 99%

Passive Treatment of Low-Ph, Ferric Iron-Dominated Acid Rock Drainage in a Vertical Flow Wetland I: Acidity Neutralization and Alkalinity Generation

Thomas¹,

Romanek²

2002

JASMR

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“…This hypothesis is supported by theory since it is well known that heterogeneous (bulk) nucleation rates increase far faster than secondary (growth) rates with increasing supersaturation [10]. Also, Barton and Vatanatham (1976) [13], who quantified the kinetics of the gypsum precipitation reaction, showed that gypsum precipitation in the bulk solution proceeds faster as temperature increases. Smith and Sweet (1971) [14] also found that gypsum precipitation in bulk solution was "too rapid" to study at 90 °C.…”

Section: Effect Of Phmentioning

confidence: 65%

Gypsum Scale Formation in Continuous Neutralization Reactors

Adams¹,

Papangelakis²

2000

Canadian Metallurgical Quarterly

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An experimental study was carried out to determine the rate and extent of scale formation of gypsum (calcium sulphate dihydrate) on stainless steel surfaces in a continuous hydrometallurgical sulphuric acid-calcium carbonate partial neutralization reactor. The purpose of the study was to determine the effects of pH, temperature, residence time, presence of metal sulphates (Fe, Al, and Ni), addition of surfactants and addition of gypsum seed on scale growth. The rate of scale formation was found to be reduced by lower temperatures, longer residence times and the presence of nickel. pH had no significant effect. The effect of these variables on the rate of scale formation was related to the degree of gypsum supersaturation. Scale reduction through the addition of sulphonated anionic surfactants was found to be effective only under certain conditions. However, gypsum seeding was found to be an effective method of scale reduction. Scale was reduced by 50% or more at a seed concentration of 10 g/L.

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“…Wentzler and Aplan (1972) found that for rapidly rotating disks in which surface coatings were swept oft; calcite dissolution rate actually increased in NazS04 and Fez(S04)J solutions. Barton and Vatanatham (1976) found rates of dissolution were affected by Fe and Al, though most of the effect they observed appears to be due to buffering of pH by Fe and Al precipitation.…”

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confidence: 86%

CHEMISTRY AND KINETICS OF CALCITE DISSOLUfION IN PASSIVE TREATMENT SYSTEMS

Rose¹

1999

ASMR

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Abstract. Reaction of calcite with AMD is a key remediation process in anoxic limestone drains, SAPS, and many wetlands, but predictions of effluent quality are currently based mainly on rules of thumb and prior experience. The PHREEQC computer program (Parkhurst, 1995) can be used to calculate the progress of this and similar reactions, and aid in understanding, design and evaluation of these systems.Simulations of the simple cubitainer tests ofWatzlaf and Hedin (1993) showed good agreement with the cubitainer results and with the ALO effluent they represented. Simulations with varying pH and P CO2 in starting solutions show that alkalinities exceeding 50 mg!L in effluent can be produced only by influent AMO with pH less than 3.5 and/or P CO2 exceeding about 10-2 atm, and only by relatively close approach to equilibrium, suggesting that adequate retention times can be crucial.Evaluation of observed influent and effluent waters in ALO's (Hedin and Watzlaf, 1994) shows that most are affected by inflows between the sampled inflow and outflow points and cannot be usefully simulated. The observed effluent at many ALO's producing high alkalinities requires oxidation and precipitation of Fe and/or Al within the drains, to generate additional H+ that will cause added calcite dissolution. For a few well constrained ALD's, the calculated alkalinities are similar to the observed chemistry, though with significant scatter. At SAPS units, simulation can be used to evaluate the effects of sulfate reduction as well as calcite dissolution.At pH values less than 5, calcite dissolution rates are strongly influenced by transport parameters such as flow velocity. Estimated calcite dissolution rates from ALD's and column experiments indicate little change in rate with pH, in contrast to published data for well stirred lab experiments. The dissolution rate is affected by concentration of S0 4 , Fe, Al, Ca, P, and other trace solutes. The optimum contact time and sizing of ALO's will be dependent on these and possibly other parameters. Additional experiments are needed to evaluate these dependencies.

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Kinetics of limestone neutralization of acid waters.

Abstract: In the article, "Kinetics of Limestone Neutralization of Acid Waters" [Environ. Sci. Technoi., 10, 262-6 (1976)], by Paul Barton* and Terdthai Vatanatham, the following corrections

Cited by 18 publications

References 0 publications

Passive Treatment of Low-Ph, Ferric Iron-Dominated Acid Rock Drainage in a Vertical Flow Wetland I: Acidity Neutralization and Alkalinity Generation

Passive Treatment of Low-Ph, Ferric Iron-Dominated Acid Rock Drainage in a Vertical Flow Wetland I: Acidity Neutralization and Alkalinity Generation

Gypsum Scale Formation in Continuous Neutralization Reactors

CHEMISTRY AND KINETICS OF CALCITE DISSOLUfION IN PASSIVE TREATMENT SYSTEMS

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