Industrial Wastewater Treatment Using Dolomite And Dolomitic Sorbents

  • Julie-Anne Hanna

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

1.1 - The incentive behind this study
It was said of Lough Ree in Ireland that; “The Lake of kings becomes the sump of Ireland” the Irish Times suggested that this severe eutrophic problem was due to “ 50-60 tonnes of phosphates and 10 tonnes of nitrates finding their way into the lake annually”, (Irish Times, 26/08/99). The impending introduction of the Nitrate Directive and the exiting eutrophic problems in over 100 lakes/reservoirs calls for investigation into a cost effective solution or treatment of this problem. The introduction of the Nitrate Directive will have a greater impact in Northern Ireland than the rest of the UK because of the geological layout of the waterways, having an impact not only on industrial and agricultural, but also municipal discharges.
Dolomite was investigated as a treatment for eutrophic water as it had received considerable research attention in recent years because of its abundance and relative value. Dolomite was readily available from an open mine in Co. Fermanagh where it was available in two particle size ranges; grit, (2-0.09mm) and powder, (250-1microns) supplied by Acheson and Glover. The research was expanded to cover other effluent problems within Ireland, including dye effluent from the carpet and textile industry, effluent containing phenol and phenolic compounds in the chemical industry and effluent containing metals in the ship building and repair industry.

1.2 - The objectives for this study
In this work dolomite was investigated as a possible treatment for wastewater due to its ability to absorb certain pollutants from aqueous solution.
Dolomite is a double carbonate of calcium and magnesium, it is a compound rather than a mixture of calcite and magnesite. Dolomite has a chemical formula of CaCO3.MgCO3 with a molecular weight of 184.4 and a specific gravity of 2.84g/cm3. Theoretically, pure dolomite contains 45.7% MgCO3 and 54.3% CaCO3.. Its hardness is 3.5 – 4.0 on Moh’s scale and its crystal system is rhombohedral, which can be seen in Figure 1.1, (Anani, 1984). Pure dolomitic limestone has 30.4% CaO, 21.8% MgO, and 47.8% CO2. Impurities such as silica, chert, clay, shale, feldspar, etc, are usually associated with the dolomitic limestone.




Calcium
Magnesium
Carbonate


Figure 1.1: Dolomite structure
The objectives of the research are as follows:
1. Investigation of the physical and chemical properties of the material and the effect of charring, chapter 5.
2. Investigation of the optimum char time, removal mechanism for the removal reactive dye from aqueous solution and compare the findings with activated carbon, (F400), magnesium oxide and calcium carbonate. To determine the mechanism for the pollutant removal and finally to describe the removal behaviour using mathematical models, where appropriate, Chapter 6.
3. Investigation of the optimum char time, removal mechanism for the removal phosphate from aqueous solution and compare the findings with activated carbon, (F400), magnesium oxide and calcium carbonate. To determine the mechanism for the pollutant removal and finally to describe the removal behaviour using mathematical models, where appropriate, Chapter 7.
4. Investigation of the optimum char time, removal mechanism for the removal nitrate from aqueous solution and compare the findings with activated carbon, (F400), magnesium oxide and calcium carbonate. To determine the mechanism for the pollutant removal and finally to describe the removal behaviour using mathematical models, where appropriate, Chapter 8.
5. Investigation of the optimum char time, removal mechanism for the removal tri-butyl tin from aqueous solution and compare the findings with activated carbon, (F400), magnesium oxide and calcium carbonate. To determine the mechanism for the pollutant removal and finally to describe the removal behaviour using mathematical models, where appropriate, Chapter 9.
6. Investigation of the optimum char time, removal mechanism for the removal phenol from aqueous solution and compare the findings with activated carbon, (F400), magnesium oxide and calcium carbonate. To determine the mechanism for the pollutant removal and finally to describe the removal behaviour using mathematical models, where appropriate, Chapter 10.




Date of AwardJul 2006
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorGavin Walker (Supervisor) & Stephen Allen (Supervisor)

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