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Title: Iron and manganese speciation and method development for the analysis of water from processing plants
Author: Sanin, Rugaya
ISNI:       0000 0004 8506 5152
Awarding Body: Liverpool John Moores University
Current Institution: Liverpool John Moores University
Date of Award: 2020
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Iron (Fe) has been indicated as the main cause of discoloration in drinking water. This normally takes the form of a yellow coloration. It is also known that manganese (Mn) can also lead to a similar yellow colour in solution. Hence, it is important to identify the source of discolouration in drinking water. To minimise the effect of these elements, the prescribed concentrations in drinking water have been set at 0.2 mg/L for Fe and 0.05 mg/L for Mn by the drinking water inspectorate (DWI-UK). The aim of this work was to optimise and validate different analytical methods for the determination of Fe and Mn simultaneously in water samples. It was also a purpose of the work to develop a robust methodology that would allow greater understanding of Fe and Mn speciation at different stages of water treatment and its relationship with governmental limits. The first two methods that were developed were inductively coupled plasma optical emission spectroscopy ICP-OES and inductively coupled plasma mass spectrometry ICP-MS. These two methods were validated using a standard reference material (SRM) and good accuracy was achieved with spiked addition methods. Further,The results showed good relative standard deviation (RSD) < 5%, linearity R2 > 0.996), with spiked recovery between 95-105%. The limit of detection (LoD) and limit of quantification (LoQ) were found to 5 ng/mL and 12 ng/mL for Fe and 1.2 ng/mL and 6.7 ng/mL for Mn, respectively, using the optimum conditions for ICP-OES; and 0.6 ng/mL and 0.3 ng/mL, respectively, for ICP-MS using collision reaction cell (CCT) mode. United Utilities (UU) water was taken from, eight different locations and at different treatment stages: Huntington water, Fishmoore water, Wayho water, Wybesley water, Sweet loves water, Oswestry and Sutton Hall. The samples were analysed to determine Fe and Mn levels using the developed ICP methods. These samples were analysed using an internal standard method and it was found to be good for the determination to minimise variation in the results obtained from the two ICP methods. The analytical method speciation was developed using cation exchange high performance chromatography ICP-MS (HPLC-ICP-MS) and this was optimized and validated for Fe and Mn species in the water processing samples. The soluble species forms of Fe3+ and Mn2+ were analysed using a chromatogram, the calibration graphs of both Fe and Mn had very good linearity (R2 = 0.9995 and 0.9999 for Fe and Mn species, respectively) in the range of 5 ng/mL to 1 μg/mL respectively. The percent recoveries were 95-105% with a RSD of < 5% and spiked recoveries for both species were in the same range as the % recoveries. For the method, species were separated in three minutes with the cation-exchange capability of the IonPAC column CG5 ion pack and through using a guard column. The results showed that both Fe3+ and Mn2+ appeared at high concentrations during the addition of the coagulants in the water processing plant and the concentration was less at the final stages of the treatment. The HPLC-ICP-MS method indicates the benefit of using a Mn removal stage in the treatment works to ensure that less than 200 μg/L and 50 μg/L of soluble Fe and Mn are obtained in the final water supply.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: QD Chemistry ; RM Therapeutics. Pharmacology ; RV Botanic, Thomsonian, and eclectic medicine