Mg/Al LDH enhances sulfate removal and clarification of AMD wastewater in precipitation processes
Maziarz, Paulina; Matusik, Jakub; Leiviskä, Tiina (2019-07-23)
Maziarz, P., Matusik, J., & Leiviskä, T. (2019). Mg/Al LDH Enhances Sulfate removal and Clarification of AMD Wastewater in Precipitation Processes. Materials, 12(14), 2334. https://doi.org/10.3390/ma12142334
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe2019080223414
Tiivistelmä
Abstract
The sulfate removal from acid mine drainage (AMD) water (initial concentration: 5301 mg/L) was investigated by precipitation and/or adsorption using calcium hydroxide (Ca(OH)2) and synthetic layered double hydroxide (LDH) of the Mg/Al type. The exclusive use of LDH efficiently removed sulfates (64.2% reduction); however, alteration of its structure was observed due to low pH. The use of Ca(OH)2 in different doses calculated in relation to gypsum stoichiometry allowed to achieve an 86% removal of sulfates. Depending on the equilibrium pH, gypsum or ettringite were the main identified phases. The two-step removal, involving the use of Ca(OH)2 followed by LDH, was less efficient than the use of the Ca(OH)2/LDH mixture when the stoichiometric amount of Ca(OH)2 in relation to gypsum was applied. The application of mixture resulted in a fast pH increase, which prevented destruction of the LDH structure. Most importantly, the use of mixture significantly reduced the sludge volume and enhanced its settling velocity.
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