Assessment of Heavy Metals Removal from Irrigation Water by Charcoal Using Laser Induced Breakdown Spectroscopy (LIBS)

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Charcoal filters were prepared from PVC pipes of D_out 90 mm, D_in 84 mm, L 100 cm provided with groove near bottom. Constant gravel depth of 20, 40, 60 and 80 cm was used as bed below the charcoal. Water containing heavy metals Cu⁺², Fe⁺², Cd⁺² and Pb⁺² of different concentrations 100, 200, 300 and 400 mg/L were used. In Combinations of charcoal with depths indicated above for charcoal and contact times 20, 40, 60, 80, 100 and 120 min were applied. Removal efficiency of the heavy metals were determined using laser Induced Breakdown Spectroscopy (LIBS), Q-switched Nd:YAG, Max. Energy 450 mJ, pulse duration 6ns, Rate 1-20 Hz. With respect to the effect of the contact time on the removal efficiency % the results illustrated that the more contact time produced more removal efficiency until reaching certain value Rmax, for each heavy metal after that a constant graph obtained this is due to an equilibrium condition which was reached at different times as following: the contact time needed to reach such equilibrium conditions for Fe, Cu, Pb were 40 min whereas for Cd was 20 min at 100 mg/L and 20 cm depth of charcoal. The filter combinations (FC) can be arranged in the following order FC₁ (400 mg/L, 80 cm and 120 min) > FC₂ (300 mg/L, 60 cm and 100 min > FC₃ (100 mg/L, 40 cm and 60 min) the removal efficiency values were 92.73, 86.70 and 79.20, respectively.