Abatement of phosphorus- and lead-induced environmental risks by means of apatite ore mine tailings

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Mining of phosphorus (P) and lead (Pb) ores increases their amounts in biogeochemical cycles and, consequently, their environmental risks. Phosphorus is an important nutrient, but P loading from sewage waters and agricultural activities to watercourses may result in eutrophication, a process eventually detrimental to aquatic ecosystems. Lead, on the other hand, poses a direct risk of intoxication to all living organisms. In addition to technical applications, Pb is used in pellets and shots on shooting ranges, which accounts for a large source of Pb loading to the environment. Prevention and abatement of detrimental impacts of P and Pb require large-scale, cost-effective techniques that do not compromise the environment.

This thesis was undertaken to investigate the potential of tailings from apatite ore beneficiation at the Siilinjärvi phosphate mine, Finland, in the dephosphorization of sewage and in the remediation of metal-contaminated areas. The material is a mixture of minerals, mainly phlogopite [KMg3(Si3Al)O10(OH)2] and calcite (CaCO3), accompanied by apatite [Ca5(PO4)3F] residues. Based on the versatile chemical properties, this geomaterial was hypothesized to act as a sorbent for P and Pb, rendering the tailings a potential agent for environmental remediation. A part of the original tailings material was artificially weathered by treating with a strong acid to create reaction-active aluminium (Al) and iron (Fe) (hydr)oxide sites. Some of the acidified material was further subjected to partial neutralization by treating with a strong base to precipitate any metals dissolved from the mineral structure during the acidification. Furthermore, all of the tailings materials were sieved into two particle-size fractions somewhat differing in their mineralogical composition and investigated as separate amendments.

The ability of the tailings to retain P and Pb from aqueous solutions as well as the tailings-induced changes in the Pb retention capacity of a mineral soil were studied by means of an isotherm technique. A sequential fractionation procedure was undertaken to investigate (a) the distribution of inherent and added P between various chemical pools in the tailings and (b) the tailings-induced changes in the distribution of Pb between various chemical pools in a mineral soil artificially contaminated with Pb as well as in an organic shooting range soil contaminated with pellet-derived Pb. Because the toxicity of dissolved Pb depends on its chemical speciation, the tailings-induces changes in the chemical speciation of water-extractable Pb in contaminated shooting range soil was tested separately by means of a cation exchange resin.

The tailings retained both P and Pb efficiently. The removal of soluble P was primarily due to specific sorption by Al and Fe (hydr)oxides and possibly to retention to calcite. Lead sorption by the untreated tailings was a combination of various sorption mechanisms taking place simultaneously, primarily through precipitation and surface complexation. All tailings materials increased the Pb sorption capacity of a mineral soil and transferred Pb from the NH4NO3-extractable pool to the more strongly bound forms. In a contaminated shooting range soil, the pellets were found to undergo continuous weathering processes that released Pb into the soil. Amending the soil with the untreated tailings (a) reduced the solubility of the pellet-derived Pb through the formation of sparingly soluble fluorpyromorphite and cerussite, (b) reduced the bioavailability of Pb by transferring it from the water-soluble and NH4NO3-extractable pools into the NaOH-extractable one and (c) transferred the most toxic cationic Pb species to the less toxic non-cationic form.

The results suggest that the tailings may serve as an agent for dephosphorization of sewage and for Pb immobilization in polluted soil. The sorption properties of the material may be further optimized by chemical and physical pre-treatments. At present, the tailings material represents an uneconomic fraction of the ore deposit, but its components may render it a natural, environmentally sound and cost-effective remediation agent.
Original languageEnglish
Place of PublicationHelsinki
Publisher
Print ISBNs978-952-10-8772-1
Electronic ISBNs978-952-10-8773-8
Publication statusPublished - 2013
MoE publication typeG5 Doctoral dissertation (article)

Fields of Science

  • 1172 Environmental sciences

Cite this

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title = "Abatement of phosphorus- and lead-induced environmental risks by means of apatite ore mine tailings",
abstract = "Mining of phosphorus (P) and lead (Pb) ores increases their amounts in biogeochemical cycles and, consequently, their environmental risks. Phosphorus is an important nutrient, but P loading from sewage waters and agricultural activities to watercourses may result in eutrophication, a process eventually detrimental to aquatic ecosystems. Lead, on the other hand, poses a direct risk of intoxication to all living organisms. In addition to technical applications, Pb is used in pellets and shots on shooting ranges, which accounts for a large source of Pb loading to the environment. Prevention and abatement of detrimental impacts of P and Pb require large-scale, cost-effective techniques that do not compromise the environment. This thesis was undertaken to investigate the potential of tailings from apatite ore beneficiation at the Siilinj{\"a}rvi phosphate mine, Finland, in the dephosphorization of sewage and in the remediation of metal-contaminated areas. The material is a mixture of minerals, mainly phlogopite [KMg3(Si3Al)O10(OH)2] and calcite (CaCO3), accompanied by apatite [Ca5(PO4)3F] residues. Based on the versatile chemical properties, this geomaterial was hypothesized to act as a sorbent for P and Pb, rendering the tailings a potential agent for environmental remediation. A part of the original tailings material was artificially weathered by treating with a strong acid to create reaction-active aluminium (Al) and iron (Fe) (hydr)oxide sites. Some of the acidified material was further subjected to partial neutralization by treating with a strong base to precipitate any metals dissolved from the mineral structure during the acidification. Furthermore, all of the tailings materials were sieved into two particle-size fractions somewhat differing in their mineralogical composition and investigated as separate amendments. The ability of the tailings to retain P and Pb from aqueous solutions as well as the tailings-induced changes in the Pb retention capacity of a mineral soil were studied by means of an isotherm technique. A sequential fractionation procedure was undertaken to investigate (a) the distribution of inherent and added P between various chemical pools in the tailings and (b) the tailings-induced changes in the distribution of Pb between various chemical pools in a mineral soil artificially contaminated with Pb as well as in an organic shooting range soil contaminated with pellet-derived Pb. Because the toxicity of dissolved Pb depends on its chemical speciation, the tailings-induces changes in the chemical speciation of water-extractable Pb in contaminated shooting range soil was tested separately by means of a cation exchange resin.The tailings retained both P and Pb efficiently. The removal of soluble P was primarily due to specific sorption by Al and Fe (hydr)oxides and possibly to retention to calcite. Lead sorption by the untreated tailings was a combination of various sorption mechanisms taking place simultaneously, primarily through precipitation and surface complexation. All tailings materials increased the Pb sorption capacity of a mineral soil and transferred Pb from the NH4NO3-extractable pool to the more strongly bound forms. In a contaminated shooting range soil, the pellets were found to undergo continuous weathering processes that released Pb into the soil. Amending the soil with the untreated tailings (a) reduced the solubility of the pellet-derived Pb through the formation of sparingly soluble fluorpyromorphite and cerussite, (b) reduced the bioavailability of Pb by transferring it from the water-soluble and NH4NO3-extractable pools into the NaOH-extractable one and (c) transferred the most toxic cationic Pb species to the less toxic non-cationic form.The results suggest that the tailings may serve as an agent for dephosphorization of sewage and for Pb immobilization in polluted soil. The sorption properties of the material may be further optimized by chemical and physical pre-treatments. At present, the tailings material represents an uneconomic fraction of the ore deposit, but its components may render it a natural, environmentally sound and cost-effective remediation agent.",
keywords = "1172 Environmental sciences",
author = "Salla Ven{\"a}l{\"a}inen",
year = "2013",
language = "English",
isbn = "978-952-10-8772-1",
series = "Pro Terra",
publisher = "Helsingin yliopisto",
number = "63",
address = "Finland",

}

Abatement of phosphorus- and lead-induced environmental risks by means of apatite ore mine tailings. / Venäläinen, Salla.

Helsinki : Helsingin yliopisto, 2013. 72 p.

Research output: ThesisDoctoral ThesisCollection of Articles

TY - THES

T1 - Abatement of phosphorus- and lead-induced environmental risks by means of apatite ore mine tailings

AU - Venäläinen, Salla

PY - 2013

Y1 - 2013

N2 - Mining of phosphorus (P) and lead (Pb) ores increases their amounts in biogeochemical cycles and, consequently, their environmental risks. Phosphorus is an important nutrient, but P loading from sewage waters and agricultural activities to watercourses may result in eutrophication, a process eventually detrimental to aquatic ecosystems. Lead, on the other hand, poses a direct risk of intoxication to all living organisms. In addition to technical applications, Pb is used in pellets and shots on shooting ranges, which accounts for a large source of Pb loading to the environment. Prevention and abatement of detrimental impacts of P and Pb require large-scale, cost-effective techniques that do not compromise the environment. This thesis was undertaken to investigate the potential of tailings from apatite ore beneficiation at the Siilinjärvi phosphate mine, Finland, in the dephosphorization of sewage and in the remediation of metal-contaminated areas. The material is a mixture of minerals, mainly phlogopite [KMg3(Si3Al)O10(OH)2] and calcite (CaCO3), accompanied by apatite [Ca5(PO4)3F] residues. Based on the versatile chemical properties, this geomaterial was hypothesized to act as a sorbent for P and Pb, rendering the tailings a potential agent for environmental remediation. A part of the original tailings material was artificially weathered by treating with a strong acid to create reaction-active aluminium (Al) and iron (Fe) (hydr)oxide sites. Some of the acidified material was further subjected to partial neutralization by treating with a strong base to precipitate any metals dissolved from the mineral structure during the acidification. Furthermore, all of the tailings materials were sieved into two particle-size fractions somewhat differing in their mineralogical composition and investigated as separate amendments. The ability of the tailings to retain P and Pb from aqueous solutions as well as the tailings-induced changes in the Pb retention capacity of a mineral soil were studied by means of an isotherm technique. A sequential fractionation procedure was undertaken to investigate (a) the distribution of inherent and added P between various chemical pools in the tailings and (b) the tailings-induced changes in the distribution of Pb between various chemical pools in a mineral soil artificially contaminated with Pb as well as in an organic shooting range soil contaminated with pellet-derived Pb. Because the toxicity of dissolved Pb depends on its chemical speciation, the tailings-induces changes in the chemical speciation of water-extractable Pb in contaminated shooting range soil was tested separately by means of a cation exchange resin.The tailings retained both P and Pb efficiently. The removal of soluble P was primarily due to specific sorption by Al and Fe (hydr)oxides and possibly to retention to calcite. Lead sorption by the untreated tailings was a combination of various sorption mechanisms taking place simultaneously, primarily through precipitation and surface complexation. All tailings materials increased the Pb sorption capacity of a mineral soil and transferred Pb from the NH4NO3-extractable pool to the more strongly bound forms. In a contaminated shooting range soil, the pellets were found to undergo continuous weathering processes that released Pb into the soil. Amending the soil with the untreated tailings (a) reduced the solubility of the pellet-derived Pb through the formation of sparingly soluble fluorpyromorphite and cerussite, (b) reduced the bioavailability of Pb by transferring it from the water-soluble and NH4NO3-extractable pools into the NaOH-extractable one and (c) transferred the most toxic cationic Pb species to the less toxic non-cationic form.The results suggest that the tailings may serve as an agent for dephosphorization of sewage and for Pb immobilization in polluted soil. The sorption properties of the material may be further optimized by chemical and physical pre-treatments. At present, the tailings material represents an uneconomic fraction of the ore deposit, but its components may render it a natural, environmentally sound and cost-effective remediation agent.

AB - Mining of phosphorus (P) and lead (Pb) ores increases their amounts in biogeochemical cycles and, consequently, their environmental risks. Phosphorus is an important nutrient, but P loading from sewage waters and agricultural activities to watercourses may result in eutrophication, a process eventually detrimental to aquatic ecosystems. Lead, on the other hand, poses a direct risk of intoxication to all living organisms. In addition to technical applications, Pb is used in pellets and shots on shooting ranges, which accounts for a large source of Pb loading to the environment. Prevention and abatement of detrimental impacts of P and Pb require large-scale, cost-effective techniques that do not compromise the environment. This thesis was undertaken to investigate the potential of tailings from apatite ore beneficiation at the Siilinjärvi phosphate mine, Finland, in the dephosphorization of sewage and in the remediation of metal-contaminated areas. The material is a mixture of minerals, mainly phlogopite [KMg3(Si3Al)O10(OH)2] and calcite (CaCO3), accompanied by apatite [Ca5(PO4)3F] residues. Based on the versatile chemical properties, this geomaterial was hypothesized to act as a sorbent for P and Pb, rendering the tailings a potential agent for environmental remediation. A part of the original tailings material was artificially weathered by treating with a strong acid to create reaction-active aluminium (Al) and iron (Fe) (hydr)oxide sites. Some of the acidified material was further subjected to partial neutralization by treating with a strong base to precipitate any metals dissolved from the mineral structure during the acidification. Furthermore, all of the tailings materials were sieved into two particle-size fractions somewhat differing in their mineralogical composition and investigated as separate amendments. The ability of the tailings to retain P and Pb from aqueous solutions as well as the tailings-induced changes in the Pb retention capacity of a mineral soil were studied by means of an isotherm technique. A sequential fractionation procedure was undertaken to investigate (a) the distribution of inherent and added P between various chemical pools in the tailings and (b) the tailings-induced changes in the distribution of Pb between various chemical pools in a mineral soil artificially contaminated with Pb as well as in an organic shooting range soil contaminated with pellet-derived Pb. Because the toxicity of dissolved Pb depends on its chemical speciation, the tailings-induces changes in the chemical speciation of water-extractable Pb in contaminated shooting range soil was tested separately by means of a cation exchange resin.The tailings retained both P and Pb efficiently. The removal of soluble P was primarily due to specific sorption by Al and Fe (hydr)oxides and possibly to retention to calcite. Lead sorption by the untreated tailings was a combination of various sorption mechanisms taking place simultaneously, primarily through precipitation and surface complexation. All tailings materials increased the Pb sorption capacity of a mineral soil and transferred Pb from the NH4NO3-extractable pool to the more strongly bound forms. In a contaminated shooting range soil, the pellets were found to undergo continuous weathering processes that released Pb into the soil. Amending the soil with the untreated tailings (a) reduced the solubility of the pellet-derived Pb through the formation of sparingly soluble fluorpyromorphite and cerussite, (b) reduced the bioavailability of Pb by transferring it from the water-soluble and NH4NO3-extractable pools into the NaOH-extractable one and (c) transferred the most toxic cationic Pb species to the less toxic non-cationic form.The results suggest that the tailings may serve as an agent for dephosphorization of sewage and for Pb immobilization in polluted soil. The sorption properties of the material may be further optimized by chemical and physical pre-treatments. At present, the tailings material represents an uneconomic fraction of the ore deposit, but its components may render it a natural, environmentally sound and cost-effective remediation agent.

KW - 1172 Environmental sciences

M3 - Doctoral Thesis

SN - 978-952-10-8772-1

T3 - Pro Terra

PB - Helsingin yliopisto

CY - Helsinki

ER -