Neutralisation of Acid Water in the Chemical Industry with Limestone

Plessis, P. du; Maree, J. P.

doi:10.2166/wst.1994.0389

Cited by 6 publications

(5 citation statements)

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“…The fluidised-bed limestone neutralisation process has been developed to neutralise free acid and remove Fe (II) and Al (III) concomitantly (Maree et al 1992;du Plessis and Maree 1994;Maree and du Plessis 1994;Maree 1994;Maree et al 1996 a,b). Previous studies showed that:…”

Section: Introductionmentioning

confidence: 99%

Neutralizing Coal Mine Effluent with Limestone to Decrease Metals and Sulphate Concentrations

Maree¹,

Beer²,

Strydom³

et al. 2004

Mine Water and the Environment

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This paper describes pilot scale tests of a novel process for the neutralisation of acidic mine water. Leachate from a waste coal dump was neutralised with limestone, and iron, aluminium, and sulphate were removed. Specific aspects studied were: the process configuration; the rates of iron oxidation, limestone neutralisation, and gypsum crystallisation; the chemical composition of the effluents before and after treatment; the efficiency of limestone utilisation; and the sludge solids content. The acidity was decreased from 12,000 to 300 mg/L (as CaCO 3 ), sulphate from 15,000 to 2,600 mg/L, iron from 5,000 to 10 mg/L, aluminium from 100 to 5 mg/L, while the pH increased from 2.2 to 7.0. Reaction times of 2.0 and 4.5 h were required under continuous and batch operations respectively for the removal of 4 g/L Fe (II). The iron oxidation rate was found to be a function of the Fe (II), hydroxide, oxygen, and suspended solids (SS) concentrations. The optimum SS concentration for iron oxidation in a fluidised-bed reactor was 190 g/L. Up-flow velocity had no influence on the rate of iron oxidation in the range 5 to 45 m/h. Sludge with a high solids content of 55% (m/v) was produced. This is high compared to the typical 20% achieved with the high density sludge process using lime. It was determined that neutralisation costs could be reduced significantly with an integrated iron oxidation and limestone neutralisation process because limestone is less expensive than lime, and a high-solids-content sludge is produced. Full scale implementation followed this study.

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Section: Introductionmentioning

confidence: 99%

Neutralizing Coal Mine Effluent with Limestone to Decrease Metals and Sulphate Concentrations

Maree¹,

Beer²,

Strydom³

et al. 2004

Mine Water and the Environment

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“…Biooxidation employs microorganisms, such as, Acidithiobacilli species in the oxidation of the sulphide minerals in the concentrate at pH between 1.2 and 1.8 at temperature between 42 and 45 o C. Upon completion of biotransformation of the sulphide concentrate, liquid and solid separation is carried out in a counter current decantation (CCD) circuit. The effluent generated is, therefore, laden with arsenic, sulphate and other base metals ions and these ions must be removed from the effluent before impoundment in any resipotory (Du Plessis and Maree, 1994). The removal of arsenic in a form that is stable is important because arsenic is carcinogenic and can be mobilised into the geoenvironment.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the neutalisation reaction is very fast, a situation that results in formation of unstable precipitate such as calcium arsenate (Pantuzzo and Ciminelli, 2010;Zhu et al, 2006;Swash and Monhemius, 1994). To reduce the reaction rate, calcium carbonate has been used in addition to lime in a-two stage neutralisation process of the bio- (Hamester et al, 2012, Bologo et al, 2009Maree and du Plessis, 1994).…”

Section: Introductionmentioning

confidence: 99%

Characterisation of Oyster Shell for Neutralisation of Bio-leached Effluent

Gordon

Asiam

2016

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Characterisation studies of Oyster Shell (Mercenera mercenera) collected from coastal towns of Ghana and its neutralising effect on bio-leached effluent has been studied using XRF, XRD, Zeta Meter, BET and SEM/EDX. The study confirmed that OS contains high calcium equivalent to about 54% CaO. The OS consists mainly of aragonite (96.1%) and calcite (2.6%) which are carbonates hence OS can be used to neutralise any acid solution. OS is very hard to mill as it has high Bond work index of 48.54 kWh/t. The Zeta Potential analysis indicates that OS will not be stable below pH of 3 and above pH of 10. Therefore OS powder dissolved and raised the pH of bio-leached effluent from pH 1.85 to 6.0 in 30 minutes. The arsenic removal increased with increasing OS concentration. The morphological study revealed that the surfaces of the reacting particles were coated with precipitates like FeAsO4 at pH of 4.5. Consequently, surface area of reacting powder increased from 4.15 m2/g to 75.46 m2/g. In a similar manner, the D50 decreased from 16.69 µm to 7.77 µm for the reacting particles at pH 4.5. Particle size distribution at pH 7.0 showed that the D50 of the OS material increased to 9.23 µm which can be due to coating of precipitates like CaSO4 on the reacting particles during acid neutralisation. Mobile arsenic extracted from the precipitate averaged 6.42 mg/L as against the EPA maximum allowable concentration of 5.0 mg/L indicating that the precipitate formed is fairly stable. Keywords: Effluent, Neutralisation, Oyster Shells, Characterisation, Work Index

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“…Its main advantage over lime is its lower price, and the production of smaller sludge (6). Its main advantage over lime is its lower price, and the production of smaller sludge (6).…”

Section: Introductionmentioning

confidence: 99%

Treatment of Highly Polluted Groundwater by Novel Iron Removal Process

Sim

Kang

Lee

et al. 2001

Journal of Environmental Science and Health, Part A

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The removal of ferrous iron (Fe(II)) in groundwater has been generally achieved by simple aeration, or the addition of an oxidizing agent. Aeration has been shown to be very efficient in insolubilization ferrous iron at a pH level greater than 6.5. In this study, pH was maintained over 6.5 using limestone granules under constant aeration to oxidize ferrous iron in groundwater in a limestone packed column. A sedimentation unit coupled with a membrane filtration was also developed to precipitate and filtrate the oxidized ferric compound simultaneously. Several bench-scale studies, including the effects of the limestone granule sizes, amounts and hydraulic retention time on iron removal in the limestone packed column were investigated. It was found that 550 g/L of the 7-8 mesh size limestone granules, and 20 min of hydraulic retention time in the limestone packed column, were necessary for the sufficient oxidation of 40 mg/L of iron(II) in groundwater. Long-term operation was successfully achieved in contaminated waters by removing the iron deposits on the surface of the limestone granule by continuous aeration from the bottom of the column. Periodic reverse flow helped to remove caking and fouling of membrane surface caused by the continuous filtration. Recycling of the treated water from the membrane right after reverse flow operation made possible an admissible limit of iron concentration of the treated water for drinking. The pilot-scale process was constructed and has been tested in the rural area of Korea.

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Neutralisation of Acid Water in the Chemical Industry with Limestone

Cited by 6 publications

References 0 publications

Neutralizing Coal Mine Effluent with Limestone to Decrease Metals and Sulphate Concentrations

Neutralizing Coal Mine Effluent with Limestone to Decrease Metals and Sulphate Concentrations

Characterisation of Oyster Shell for Neutralisation of Bio-leached Effluent

Treatment of Highly Polluted Groundwater by Novel Iron Removal Process

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