Speciation of Cr (III) and Cr (VI) in Industrial Waste Water using Biphasic Extraction and Determination by LIBS

Abstract

An aqueous, biphasic one step separation method for Cr (III) and Cr (VI) is presented in this paper. Optimization of different parameters like pH, volume of solvent etc. in the extraction experiments are carried out using standard solutions of Cr (VI) and Cr (III). Extraction efficiency for chromium species using biphasic technique is calculated by performing quantitative analysis of chromium using Laser Induced Breakdown Spectroscopy (LIBS). After biphasic extraction, LIBS spectra of (NH₄)₂SO₄ containing Cr are recorded by depositing and drying 20 µL of this solution on Whatman filter paper (No. 542). Quantitative analysis of LIBS spectra are performed using Cr emission line at 425.4 nm. Optimum extraction (about 90 %) of Cr (VI) is found at pH 4 and solvent volume 4mL. The optimized methodology is then used for determination of total Cr and Cr (VI) in waste water collected from leather tanning industries of Kanpur City, India.