Iron oxide is a crucial hydrophilic mineral in the minerals, metals and materials industries. Colloidal iron oxide dispersions have proven difficult to dewater to high solid-loading during routine hydometallurgical processes. Despite this, there are a limited number of studies integrating interfacial chemistry, flocculation and dewatering behaviour of iron oxide in the literature. / In this study, fundamental investigations of the principles underpinning hematite pulp dewatering behaviour were examined to determine the effectiveness of four polyacrylamide ploymers (home-polymer, PAM N, anionic carboxylate substituted copolymer, PAM A, anionic sulphonate substituted copolymer, PAM S, and cationic trimethyl amino ethyl substituted copolymer, PAM C) as flocculants and four metal salts, Mn(NO), MnSO, and MnC1and KSO) as coagulants. Effects of flocculant structure type and concentration, metal salt type and pH on the surface chemistry, pulp rheology and the dewaterability of dispersions were considered. Experiments were conducted at the isoelectric point (iep-pH 8.5), below (pH 6) and above (pH 11) the iep of the hematite to investigate particle charge effect in the presence and absence of the coagulants and/or flocculants. / Investigations into the polymer adsorption mechanisms conducted using infrared spectroscopy found PAM A to chemically adsorb onto hematite particles via bidentate chelation on either side of the iep, and via monodentate chelation at the iep. These bonding mechanisms were found to influence the pulp particle interactions (rheology) and hence dewatering behaviour. Hydrogen bonding also occurred between PAM A and PAM N and the hematite particles. Spectroscopic evidence was also provided, for the first time, of the partial hydrolysis of non-ionic polyacrylamide at high pH. / Flocculation in general was found to be most effective when the polymer was of similar charge to the hematite particles. Settling rates of over 100 m/h were achieved at and below the iep after flocculation with the charged polymers, whilst consolidation was generally unaffected by flocculation at any pH. Bridging mechanisms between polymers of similar charge to the particles was most effective. Electrostatic and charge patch flocculation mechanisms prevailing between oppositely charged polymer and hematite particles provided less-improved dewatering. / Surface chemistry was greatly influenced by the anionic polymers at and below the iep of hematite. Addition of sulphate ions caused pronounced particle surface charge suppression with significant zeta potential reduction below the iep. The sulphate ion also facilitated PAM A adsorption above the iep which led to a significant improvement in settling rate. Dewatering of flocculated pulps was more efficient at and below the iep of hematite, with the negatively charged dispersion at high pH generally comprising a turbid supernatant. Manganese salts in synergy with PAM A significantly enhanced settling rates at and below the iep, however, the effect was subtle when compared to the addition of the sulphate ion. Application of mechanical shear to the pre-sedimented pulps produced outstanding improvement in particle consolidation, with up to 20 wt% increase in solid loading observed. / Thesis (PhDApSc(MineralsandMaterials))--University of South Australia, 2008.
| Identifer | oai:union.ndltd.org:ADTP/266996 |
| Creators | McGuire, Melanie Jane. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | copyright under review |
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