AbstractPoly(1-methylpyrrol-2-ylsquaraine) (PMPS) particles are a fine blue-black insoluble powder. Scanning electron microscopy (SEM) pictures reveal that the PMPS particles are microspheres with diameters ranging from 1.3 - 4 micrometers (distribution
peaking at 1.9 micrometers). The absorption capacity values of PMPS particles were studied for a large majority of the elements in the periodic table in order to establish a pattern or trend in absorption. The elements specifically targeted at the beginning of the research were the biological elements vital to sustain life and the heavy metals that pose a threat to the environment via pollution and poisoning.
Fifty-four elements were investigated in total and all absorbed in varying amounts ranging from 0.01 mmol/g for caesium up to 5.66 mmol/g for phosphorous. It was found that varying the initial elemental compound, temperature and solvent concentrations vastly altered the amount of element absorbed. The majority of elements absorbed best when dissolved in hot concentrated hydrochloric acid at 50oC, some preferred cold conditions
(4oC) and/or a neutral solvent (water). The freshness of the elemental compound had a huge impact on the absorption capacities, i.e. new compounds absorbed much better than old stock. A comparison between chloride salts and the hydroxides of Group 1 alkali metals revealed that the hydroxides absorbed much better than the salts, sometimes with more than a ten-fold increase.
Release profiles were studied for PMPS particles containing eleven different elements when subjected to an aqueous medium. The study focused on some of the elements that are commonly utilised in industry and also the soft acids and bases primarily because they had some of the highest sorption values and the fact that the majority are known to be particularly toxic to man. The amount of ions released varied enormously ranging from 0% release for selenium up to 83% for arsenic. It was interesting to observe that arsenic had the highest percentage release despite having the lowest sorption uptake and selenium had the lowest (zero) percentage release despite having one of the highest sorption uptakes. Analysis of the release data revealed that there appears to be two types of profile emerging. In the first type of profile the metallic ions leached out of the PMPS particles slowly over a period of time until equilibrium was reached whereupon no more
ions were released. This happened for the arsenic, copper, lead, mercury, cadmium, silver and gold ions. In the second type of profile all of the free ions were released as soon as water was added, in the first 2 mL aliquot. This happened for the manganese, sodium and caesium ions. It would appear that the ions that have the gradual release profile are the heavier ions on the right hand side of the periodic table, which also means that they are
soft acids or bases. The ions that have the second type of profile, where release was achieved in the first aliquot are situated on the left hand side of the periodic table and were all found to be hard acids.
Over-coating studies using PMPS particles containing copper and sodium were separately investigated. The results revealed that PMPS-Cu particles when overcoated with a polymer do appear to have a slow release profile.
|Date of Award||2008|
|Supervisor||Daniel Lynch (Supervisor), Mark Bateman (Supervisor) & Alan Newman (Supervisor)|