Abstract
A simple cloud point extraction protocol has been proposed for the quantification of sulfide at trace level. The method is based on the reduction of iron (III) to iron (II) by the sulfide and the subsequent complexation of metal ion with nitroso-R salt in alkaline medium. The resulting green-colored complex was extracted through cloud point formation using cationic surfactant, that is, cetylpyridinium chloride, and the obtained surfactant phase was homogenized by ethanol before its absorbance measurement at 710 nm. The reaction variables like metal ion, ligand, surfactant concentration, and medium pH on the cloud point extraction of the metal-ligand complex have been optimized. The interference effect of the common anions and cations was studied. The proposed method has been successfully applied to quantify the trace level sulfide in the leachate samples of the landfill and water samples from bore wells and ponds. The validity of the proposed method has been studied by spiking the samples with known quantities of sulfide as well as comparing with the results obtained by the standard method.
Highlights
Sulfide is one of the most essential parameter in monitoring the water quality due to its high toxicity for aquatic life
Though the Fe (II)-nitroso-R salt complex is water soluble, it has been successfully extracted into surfactant rich phase, and it can be explained through the following mechanism
When the concentration of surfactant is lower than the critical micelle concentration (CMC), only slightly soluble ion associates can form between anionic ligand and surfactant monomers causing turbidity [14]
Summary
Sulfide is one of the most essential parameter in monitoring the water quality due to its high toxicity for aquatic life. Monitoring of aqueous sulfide is one of the important parameters in industrial effluents as the discharges containing sulfide cause the contamination. The treatment of such water generally involves aeration, chlorination or flocculation, and other processes [4]. We are reporting the use of cationic surfactant, that is, cetylpyridinium chloride (CPC), as a sensitizing agent to quantify trace level sulfide by its reaction with ferric iron and its subsequent complexation of reduced ferrous iron with nitroso-R salt to form a green-colored complex. The method has been applied for the quantification of dissolved sulfide in the leachate, bore well, and pond water samples, and the results obtained by the proposed method are in good agreement with the standard methylene blue method [21]
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