http://orcid.org/0000-0003-4108-0775
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ABSTRACT
We report the sensing behavior of liquid–liquid extraction of nickel(II), which has been selectively determined from contaminated water samples by a simple UV-visible spectrophotometer. The method is based on synergistic extraction of nickel(II) by 1-(2ˊ,4ˊ-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2ˊ,4ˊ-dinitro APTPT] with pyridine. Nickel(II) reacts with 2ˊ,4ˊ-dinitro APTPT and forms a green-colored complex at pH 9.2. In addition, the Ni(II) ions were detected with the naked eye with the ligand. The absorbance of the coloured complex was measured at 660 nm and the colored complex is stable for more than 48 h even in the presence of other competing ions. The system obeyed Beer’s law in the concentration range of 5–50 μg mL−1 of nickel(II) and the optimum range evaluated by Ringbom’s plot method is 10–40 μg mL−1 with an excellent linearity and a correlation coefficient of 0.999. The molar absorptivity and Sandell’s sensitivity of the extractive species were found to be 1.64 × 103 dm3 mol−1 cm−1 and 0.0585 μg cm−2 in the presence of pyridine, and 7.4 × 102 dm3 mol−1 cm−1 and 0.78 μg cm−2 in the absence of pyridine, respectively. The composition of nickel(II)-2ˊ,4ˊ-dinitro APTPT-pyridine was established by the slope ratio method, the mole ratio method and Job’s method of continuous variation. It was found that the metal:ligand:synergent (M:L:Sy) ratio is 1:2:2. To assess the precision and accuracy of the developed method, determinations were carried out at n = 5. The relative standard deviation of all measurements does not exceed 0.16%. Excellent selectivity was found towards the Ni(II) ion due to a specific complex formation between the Ni(II) ion and the organic ligand. In the extraction of Ni(II), several affecting factors, including the solution pH, ligand concentration, equilibrium time, initial Ni(II) ion concentration and foreign ions, were investigated and the applicability of the method was checked by the analysis of synthetic mixtures and alloys. The developed method was successfully used for the determination of nickel(II) from waste water effluents from the foundry region and the nickel plating industry (Kolhapur city). The results obtained by the developed method were also confirmed by AAS. We claimed from this study that Ni(II) could be successfully determined by the spectrophotometric method developed in the current work. The present work is obviously much simpler than the conventional method comprising multistep processes.
Acknowledgements
One of the authors, Ganesh S. Kamble, is highly thankful to Professor (Dr) S. Kannan, Discipline of Inorganic Materials and Catalysis, Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India, for constant encouragement, and also thankful to Kolhapur Institute of Technology, College of Engineering, Kolhapur, Maharashtra. We are grateful to UGC-SAP and DST-FIST, Department of Chemistry, Shivaji University, Kolhapur.