Utilization of Laser Induced Breakdown Spectroscopy (LIBS) to Detect the Heavy Metals and their Concentrations in Dairy Products Waste Water

Abstract

In this work, Laser Induced Breakdown Spectroscopy (LIBS) has been used to investigate, and calculate the concentrations, of heavy metals in waste water collected from dairy products processing plants in Khartoum state during the period from 2013 to 2015. Five industrial waste water samples, collected from diary product plants, were used as study samples. The breakdown of the samples was induced by focusing a pulsed Nd: YAG laser at 532 nm, 2Hz Rpetion Rate, pulse duration of 10 ns, with pulse energies: 30, 60, 80, and 100 mJ, respectively. The emission spectra of the samples plasma were collected via optical fiber and analyzed by Ocean Optics LIBS 4000- spectrometer. The recorded spectra of the samples were analyzed using NIST data. The analysis of the spectra showed considerable amounts of neutral atoms like Na, Co, Cu, Fe, Cs, Hg, Pr, Cr, Fe, Ti elements in addition to the ions: (Co+1 , Cu+1, Cs+1 ,Fe+1 , Ba+2 , Cr+1 , Mg+2, and Mn+1 ions. The concentrations of some heavy metals (Fe, Hg, Cr, Ti, Mn, Mg) were calculated using the calibration curves based on the emission spectra of known concentrations of the some elements. At 30 mJ, (Fe, Hg, Cr, Ti, Mn) were appeared with different concentrations, while Cr, Hg, and Ti were appeared with high concentrations in the five samples, where Ti had the highest concentration. At 60 mJ, the element of (Fe, Cr, Ti, Mg) were appeared with low concentrations relative to the concentrations of the same metals at 30 mJ, It can be concluded that LIBS technique proved to be, fast accurate technique in the detection of heavy metals and determine its concentrations in liquid samples. A portable LIBS system for online analysis of contaminated sites with heavy metals can be recommended for improvement of the environment and controlling the pollution at industrial areas. Also the study recommended the establishment of a correlation between the laser power density and the ionization energy for each element.