Analysis of sulfur reaction towards the formation of iron sulfide in groundwater
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Date
2019-07
Authors
Nurul Farahain Binti Md Yusof
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Abstract
Groundwater sources have always been known as the secondary water source in Malaysia. In USM Engineering Campus, there is groundwater resource which has the potential that may developed for irrigation water use. However, contaminations in the groundwater is a major problem that is needed to overcome. This project investigated about the formation of iron sulfide, FeS due to the alteration of distinct colour from yellowish green to black and later then to rustic red, which included the study of the occurrence and the fast reaction of FeS through groundwater characterization and the relationship between the occurrence of FeS and hydrogen sulfide, H2S to analyze the behaviour of the compounds in the groundwater. Characterization of groundwater have been carried out using multiple different testings such as ICP-OES, DSC, FESEM-EDX and XRD analysis, as well as precipitation titration with strong oxidizing agent. From the results, the groundwater is considered saline with the salinity of 5.1 ppt, in addition to the high concentrations of salt compounds found present from the result of ICP-OES, XRD analysis and FESEM-EDX. The salinity occurred due to the seawater intrusion from the estuary into the groundwater aquifer. Besides that, it has been found that FeS undergone a sequence of phase transformation (amorphous FeS → mackinawite → troilite → pyrrhotite → pyrite) owing to the combination of high oxidation, pH and temperature, proving that the black precipitate present in the groundwater indeed represent the reaction of FeS. Furthermore, S2- ion in FeS is easily detached from Fe2+ ion due its sensitiveness to the presence of oxygen which increased the rate of oxidation and also by the presence of chlorine which act as the catalyst in accelerating the reaction and destabilizing in sustaining the FeS form.