Mg/Al LDH Enhances Sulfate removal and Clarification of AMD Wastewater in Precipitation Processes.

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.

SUBMITTER: Maziarz P 

PROVIDER: S-EPMC6679161 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature