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J A Finch

Publications and source records attributed to J A Finch.

4 recordsLinked to original sources
PubMed2005

Measurement of thickness and composition of a solvent film on a bubble.

Solvent-coated air bubbles in the air-assisted solvent extraction (AASX) process achieve the dual role of high solvent specific surface area and ease of phase separation. The properties and thickness of the solvent film control the process. As an approach to the study, the layer interferometry (in the UV-vis region) and FT-IR spectroscopy were used to measure the time dependent thickness and chemical composition, respectively, of a film formed by blowing an air bubble in kerosene-based solvents. The film was stabilized by the presence of 1.5 ppm silicone oil, as employed in AASX. The film appears to comprise two layers; an outer layer of almost constant thickness and an inner layer which decreased in thickness with time. The latter is considered relevant to AASX. Generally, the initial thickness was approximately 3 microm which decreased over several minutes to a final rupture thickness of 500 nm. The initial thickness is of the order determined indirectly. The chemical composition of the layer did not change with time.

Air↗
PubMed2005

Processing of metallurgical residues by flotation - bench-scale studies on two industrial products.

Resource recovery from two metallurgical residues by flotation was investigated applying an electrostatic model to select initial conditions. The first, a sulphation roast/water leach residue, was processed to float lead sulphate, comparing dodecylamine and xanthate collectors. From the second, a neutralization residue, gypsum, was recovered by reverse flotation of ferric hydroxide, comparing oleate and sulphonate collectors. In both cases, further upgrading by acid leaching was considered.

Amines↗
PubMed2003

Aggregation of sphalerite: role of zinc ions.

Sphalerite from six sources is shown to aggregate at ca. pH 7-9, confirmed by different techniques (settling velocity, suspension analysis, and optical microscopy). This does not correlate with the isoelectric point, which is consistently < pH 6. A similar observation was made by Healy and Jellet [J. Colloid Interface Sci. 24 (1967) 41-46] for ZnO (and reconfirmed here), who suggested Zn hydrolysis products were responsible. The hypothesis is tested using chalcopyrite and silica suspensions in the presence of Zn ions. It is found that aggregation occurs over the same pH range, 7-9. Solution and surface analysis (extraction by EDTA) shows sphalerite released sufficient Zn ions to promote aggregation. The pH range 7-9 corresponds to hydroxide formation, suggesting this is the species responsible. Aggregation of sphalerite due to the polymerization/flocculation action of zinc hydroxide is proposed.

Journal Article↗