The stock solution of Cr(VI) ions (1000 mg/L) was prepared by
dissolving 2.8269 g of accurately weighed potassium dichromatein 1 L distilled water.Standard solutions of Cr(VI) ions concentration
range from 50 to 500 mg/L were obtained by dilution of the
stock solution. The initial pH of the experimental solutions was
adjusted to the desired value by adding 0.1 M H2SO4.