Essence of photoelectric colorimetric assays of alcoholic methyl red dye solution in the purification of azo dye-contaminated waste-water

Abstract

The aim of the present research is: to determine the wavelength of maximum absorption of white light by
alcoholic methyl red dye solution, to construct/plot the standard concentration calibration curve of the
alcoholic methyl red dye solution, to find the Beer-Lambert’s concentration limits of alcoholic methyl red
dye solution and to determine unknown concentrations of alcoholic methyl red dye in waste water samples,
in a simulation model experiment. The wavelength of maximum absorption (1.18), of white light by 0.01%
w/v alcoholic methyl red dye solution (pKa: 4.76, 25°C) was determined by photoelectric colorimetric
technique and is in the range of 470-529 nm. A serial dilution of a 0.01% alcoholic methyl red dye stock
solution, was prepared and used in constructing a standard concentration calibration curve, whose
equation is A470-529 nm = 320C% w/v. The Beer-Lambert’s constant and Beer-Lambert’s concentration limits of
alcoholic methyl red dye solution are 320 (% w/v. cm)-1
and 0.0025% w/v, respectively. The results observed
of the simulation model experiment, indicate that the simulated treated-waste water samples of
concentrations of alcoholic methyl red dye: 0.0012 ± 0.0002, 0.00047 ± 0.0001 and 0.0003125 ± 0.0001, were
significantly lower (p<0.05) than a given standard limit low of 0.00125 ± 0.00001% w/v (mean ± standard
error, % w/v) of alcoholic methyl red dye solution and thus were purified with an efficiency >90%. The
photoelectric colorimetric assay is efficient for use in purification steps of azo dye-contaminated waste water.