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Improved dewaterability of iron oxide dispersions: the role of polymeric flocculant type, pH and shear
Author(s) -
McGuire Melanie J.,
AddaiMensah Jonas,
Bremmell Kristen E.
Publication year - 2008
Publication title -
asia‐pacific journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.348
H-Index - 35
eISSN - 1932-2143
pISSN - 1932-2135
DOI - 10.1002/apj.112
Subject(s) - flocculation , cationic polymerization , polymer , dewatering , chemical engineering , chemistry , copolymer , settling , materials science , polymer chemistry , organic chemistry , environmental engineering , geology , geotechnical engineering , engineering
Substantial amounts of recyclable water are trapped in mineral waste tailings dams annually due to less than effective dewatering processes. To address this, a study has been conducted of the flocculation performance of four high molecular weight (>5 × 10 6 Da) polyacrylamides, non‐ionic homopolymer (PAM N), anionic carboxylate substituted copolymer (PAM A), anionic sulfonate substituted copolymer (PAM S), and cationic trimethyl amino ethyl substituted copolymer (PAM C), on the dewaterability of iron oxide suspensions as a function of pH. Significant polymer structure‐mediated and pH‐dependent trends were observed. Upon flocculation with up to 500 g polymer/t solid, settling rates in the range of 3–100 m/h were observed, along with sediment solid loading in the range 35–40 wt%. Settling rates varied depending on polymeric flocculant type, and were higher for anionic and cationic polymers than for non‐ionic polymers. Settling was most efficient at and below the iso‐electric point (iep, pH 8.5). Polymer structure type did not have any noticeable impact on the extent of pulp consolidation. Moderate shear significantly improved the consolidation (55 wt% solid) of pre‐sedimented pulps. For the selection of a flocculant, a polymer that displayed an opposite charge to that of the particles appeared to provide improved flocculation and dewatering performance. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.