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 Research Papers (Abstracts)

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Research Papers (Abstracts)

A Study of the Use of Ti (IV) as a Coagulant

 David A. White, Radu Rautiu and S. Amornraksa

submitted 2000.
This paper investigates the use of titanium as a coagulant for the treatment of a series of synthetically produced water types. An extensive literature review on this relatively novel field is also included. Chocolate milkshake powder was added to these to produce a sewage simulant for the coagulation tests. Four different waters were used. These were Thames tap water, supplied by Thames Water plc., distilled water, synthetic saline water and synthetic mine drainage water. Tests were carried out using a titanium sulphate solution and comparison tests were run in parallel using a ferric coagulant. Settled volume and final turbidity were the main parameters that were measured. Titanium was found to be an effective coagulant for all four of the water types studied. Ferric flocs were not able to remove particulate matter from distilled or mine water, though they were slightly better than titanium for the other two waters.

Evaluation of the Effect of Temperature on Potassium Clinoptilolite Ion Exchange

 David A. White, Andreas Nattkemper and Radu Rautiu

Nuclear Technology , vol.127, August 1999, 212-217
Ion exchange on a potassium-exchanged natural zeolite at various temperatures is examined. The ions studied were cesium and cobalt, and the contact temperatures were 25, 60 and 100°C. The main focus of the work was to examine the use of natural zeolite as a direct means for the removal of radioactive contaminants. It was found that cesium was more selectively sorbed than cobalt and that higher amounts of both cations were taken up as the temperature of contact increased. The raw data could be correlated usingg a Brunauer-Emmett-Teller - type isotherm. The ion exchange equilibrium constants and activity of the sorbing ion on the zeolite were used in correlating the data. An Arrhenius behavior was suggested.

Adsorption of Phenolic Compounds from Water by Surfactant-Modified Pillared Clays

 Ratanawan Wilbulswas, David A. White, and Radu Rautiu

Trans. I. Chem E., vol. 77, Part B, March 1999, 88-92

An organophilic pillared clay-based adsorbent was prepared by incorporating a cationic surfactant, hexadecyl -trimethyl ammonium (HDTMA) during the synthesis of conventional aluminium pillared clays. A specific amount of HDTMA was desired to occupy the cation exchange sites of the precursor clay. The presence of the HDTMA surfactant enhanced the adsorption ability of the clays toward phenolic compounds from aqueous systems. Adsorption experiments were carried out using a batch equilibration technique to investigate the removal of three toxic phenol compounds- phenol, 3-monochlorophenol and 3,5-dichlorophenol - by the surfactant-modified pillared clays. Comparative adsorption experiments were also conducted with Montmorillonite, the starting clay, as a reference material. The experimental results demonstrate the feasibility of utilising surfactant-modified pillared clays as an adsorbent for removing phenol and chlorinated phenols from water.

The adsorption affinity decreased in the following sequence: 3.4 dichlorophenol > 3-monochlorophenol > phenol. The Langmuir model was used to analyse the adsorption equilibria and calculate the adsorption capacity of phenolic compounds on these surfactant-modified pillared clays, S-PILCs.

 Removal of humic substances by aluminium-based pillared clays

 Ratanawan Wilbulswas, David A White, Radu Rautiu

Environmental Technology , vol19 (6), 1998, pp. 627-632
This paper deals with the synthesis and use of alumina-pillared clays, Al-PILCs, for water treatment in removing humic substances. Al-PILCs represent a new class of adsorbents with an increased potential for the removal of colour generating compounds such as 'humic' and 'fulvic acids'. High content Al-PILCs were synthesised. Various thermal treatment conditions, 453K and 673K, and the effect of ultrasonic treatment during the preparation of Al-PILCs were also explored. Comparative adsorption experiments were conducted with Montmorillonite, as the starting clay as a reference material, and several different batches of Al-PILCs. Adsorption of 'humic acid' from both distilled and tap water were studied. A maximum adsorption capacity of 23.4 mg g(-1) of 'humic acid' on Al-PILCs was obtained with PILC-O-453 which represents Al-PILCs treated at 453K. Al-PILCs are more effective at removing 'humic acid' from tap water especially at high 'humic acid' concentrations. The adsorption process is described by Langmuir-type isotherms. It is shown by these experiments that Al-PILCs represents a valuable adsorbent for the removal of colour-generating compounds such as 'humic acid'.

The sorption of anionic species on hydrous tin dioxide 

 David A White and Radu Rautiu

 Chemical Engineering Journal , Vol.66, No.2, 1997, pp.85-89
This paper describes the anion exchange properties of hydrous tin dioxide and of a composite silica-tin dioxide. The anions studied were fluoride, iodide, iodate and antimonate. Some isotherm data have been obtained and have been correlated with the Langmuir isotherm in which the coefficient in the denominator is negative. Generally speaking the uptake of anions drops as the pH of the contacting solution rises. The balance of evidence would seem to indicate that the process is classical ion exchange. The extent of the pH range over which this occurs is surprising and contradicts classical notions of hydrous oxide ion exchange theory. 

The sorption of cationic species on hydrous tin dioxide 

Radu Rautiu and David A White 

 Solvent Extraction and Ion Exchange , Vol.14, No.4, 1996, pp.721-738
This paper discusses some recent research work into the sorption of cations both hydrolysable and those that are not, on to a hydrous tin oxide and a silica-tin ion exchanger. The ions studied are mostly those that might be encountered in a radioactive waste streams; such as the non-hydrolysable ions Sr++ and Cs+, hydrolysable species such as Co++ and Eu3+ and complexes such as Ru(NO)(3+). Complete isotherm data have been generated for some of the ions considered. These can be correlated by a 'Langmuir' isotherm for quite a wide range of solution pH. From this data the oxide capacity for the ion can be determined. Uptake of soluble cationic species always increases with solution pH. However for most metallic cations the exchangers are able to adsorb anionic species by the complex formation at low solution pH. Elution of the ions with acid and a complexing agent such as EDTA is also considered. Finally 'synergistic effects', when mixtures of cations are contacted with the exchangers are considered. 

Clay minerals as sorbents for nuclear reactor activation products 

 Solomon A Adeleye, Radu Rautiu, David A White, Peter G Clay

 Journal of Materials Science , Vol.30, No.3, 1995, pp.583-586
A comparison is presented of cobalt and chromium uptake on different clays. It is shown that clay minerals are good adsorbents for cobalt and chromium in waste effluents. The sorption of cobalt and chromium on the clays studied was by ion exchange and surface complex formation, respectively. In addition, the percentage of either cobalt or chromium removed in a mixed solution environment is higher than the individual adsorption in single-component experiments. This proves a synergistic mechanism. The optimum uptake of each metal ion from mixed species was achieved by montmorillonite clay in the calcium form. 

 The use of zeta-potential measurements in inorganic ion exchange studies

 Radu Rautiu, David A White, Solomon A Adeleye, Laurie Adkins

 Hydrometallurgy , Vol.35, No.3, 1994, pp.361-374
A compendium of results of the apparent zeta potential measurements for finely divided organic and inorganic ion exchangers is given. Potassium nitrate solution proved to be an inert electrolyte and the zeta potential (z) is constant with pH variation for the ion exchangers measured. Generally zeta is positive for anion exchange and negative for cation exchange. Zeolite data and results for electrolytes containing ions other than potassium or nitrate are, however, somewhat anomalous and need further investigation. 

Physical-chemical study of a thermal water for the recovery of useful elements 

 R. Kuzman-Anton, M. Parlea, R. Rautiu, M. Geanta

Revista de Chimie (Bucharest) , 1989, Vol.40, No.3, pp.259-261

(in Romanian with English Abstract)

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