Article: Desilication of calcined pulverised fly ash and use of silicate solution to prepare a mesoporous silica adsorbent for heavy metals in acid mine drainage Journal: International Journal of Environmental Technology and Management (IJETM) 2019 Vol.22 No.2/3 pp.155 - 176 Abstract: Mesoporous silica (MCM41) adsorbent was prepared from silicate solution produced from silica leaching of calcined pulverised fly ash. MCM41 was used for the removal of heavy metals and neutralisation of acid mine drainage. Silica leaching was optimised using two level full factorial and 13 run central composite rotable uniform design with five centre points. A pH of 7 produced the most pure MCM41 with an external surface area of 98,000 m2m-3. A 4% m/v solid loading of MCM41 could remove 95.5%, 97.3% and 99.6% of Ni, Cu and Fe respectively. The adsorption process was found to fit the Langmuir isotherm and pseudo second order kinetics. The Gibbs free energy of adsorption for all metals was below-20 kJ/mol for all metals. The enthalpy for Fe, Cu and Ni removal were 19.97 kJ/mol, 21.40 kJ/mol and 16.44 kJ/mol respectively and thus endothermic. The significance of the research was that silica could be leached from calcined pulverised fly ash and MCM41 can be used as an adsorbent for heavy metals in acid mine drainage treatment. Inderscience Publishers - linking academia, business and industry through research

Title: Desilication of calcined pulverised fly ash and use of silicate solution to prepare a mesoporous silica adsorbent for heavy metals in acid mine drainage

Authors: Thabo Falayi; Freeman Ntuli; Felix Ndubisi Okonta

Addresses: Department of Civil Engineering Science, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Johannesburg, South Africa; Department of Chemical Engineering, Malawi University of Science and Technology, P.O. Box 5196, Limbe, Blantyre, Malawi ' Department of Chemical Engineering, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, Johannesburg, South Africa ' Department of Civil Engineering Science, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Johannesburg, South Africa

Abstract: Mesoporous silica (MCM41) adsorbent was prepared from silicate solution produced from silica leaching of calcined pulverised fly ash. MCM41 was used for the removal of heavy metals and neutralisation of acid mine drainage. Silica leaching was optimised using two level full factorial and 13 run central composite rotable uniform design with five centre points. A pH of 7 produced the most pure MCM41 with an external surface area of 98,000 m²m^-3. A 4% m/v solid loading of MCM41 could remove 95.5%, 97.3% and 99.6% of Ni, Cu and Fe respectively. The adsorption process was found to fit the Langmuir isotherm and pseudo second order kinetics. The Gibbs free energy of adsorption for all metals was below-20 kJ/mol for all metals. The enthalpy for Fe, Cu and Ni removal were 19.97 kJ/mol, 21.40 kJ/mol and 16.44 kJ/mol respectively and thus endothermic. The significance of the research was that silica could be leached from calcined pulverised fly ash and MCM41 can be used as an adsorbent for heavy metals in acid mine drainage treatment.

Keywords: pulverised fly ash; PFA; MCM41; leaching; central composite rotable uniform design; adsorption; Langmuir isotherm; pseudo second order kinetics; full factorial design; acid mine drainage; metal loading.

DOI: 10.1504/IJETM.2019.102202

International Journal of Environmental Technology and Management, 2019 Vol.22 No.2/3, pp.155 - 176

Accepted: 02 Jun 2019
Published online: 10 Sep 2019 *

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Title: Desilication of calcined pulverised fly ash and use of silicate solution to prepare a mesoporous silica adsorbent for heavy metals in acid mine drainage

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