Effects of electrolytes and curing on freezing of ferric hydroxide sludge
Journal
Colloids and Surfaces A: Physicochemical and Engineering Aspects
Journal Volume
162
Journal Issue
1-3
Pages
285-288
Date Issued
2000
Author(s)
Jean D.S.
Abstract
This work elucidates how the electrolytes and curing time affect freezing and thawing treatment of ferric hydroxide sludge. The sludge is frozen at a freezing temperature of -16.5 ¢XC with addition of one of the following four electrolytes: sodium sulfate (Na2SO4), potassium nitrate (KNO3), sodium nitrate (NaNO3) and sodium chloride (NaCl). Although the eutectic temperatures for the former two and latter two electrolytes are higher than and lower than the freezing temperature, respectively, improvements of sludge filterability and settleability are independent of the electrolyte species as well as the additional amount. Differential scanning calorimetry (DSC) tests imply that ferric hydroxide particles might suppress the formation of salt/water eutectic, leading to a negligible effect of electrolyte species. On the other hand, curing of 2-24 h profoundly affects sludge performance, indicating the incorporation of mass transfer limitation into the moisture transfer.This work elucidates how the electrolytes and curing time affect freezing and thawing treatment of ferric hydroxide sludge. The sludge is frozen at a freezing temperature of -16.5¢XC with addition of one of the following four electrolytes: sodium sulfate (Na2SO4), potassium nitrate (KNO3), sodium nitrate (NaNO3) and sodium chloride (NaCl). Although the eutectic temperatures for the former two and latter two electrolytes are higher than and lower than the freezing temperature, respectively, improvements of sludge filterability and settleability are independent of the electrolyte species as well as the additional amount. Differential scanning calorimetry (DSC) tests imply that ferric hydroxide particles might suppress the formation of salt/water eutectic, leading to a negligible effect of electrolyte species. On the other hand, curing of 2-24 h profoundly affects sludge performance, indicating the incorporation of mass transfer limitation into the moisture transfer. Copyright (C) 2000 Elsevier Science B.V.
Subjects
Dewaterability
Electrolyte
Eutectic formation
Ferric hydroxide
Freezing
Type
journal article