Polymeric adsorbent for the removal of organic and inorganic pollutants from aqueous solution

Abstract

Apart from the use of conducting polyaniline as electronic materials, in the present work, neutral and charged polyaniline are utilized as the effective adsorbents for their possible application in removing organic dyestuff, such as methylene blue, procion red and inorganic species, viz., nickel chloride from their aqueous solutions. 1 • charged while the other two matrices seem to be either neutral or negatively charged. UV-Vis and IR spectroscopy studies yielded useful qualitative information on the treated polymer matrices. The strong absorption maxima observed in the ultraviolet region may be attributed to the inter band transition; the other intense band in the visible region probably results from the transition between the mid-gap states. From the IR spectra, band characteristics confirmed the differences between the treated polyaniline matrices. The electrical conductivity measurements also provide strong evidence regarding the difference of the electrical properties of the treated polymer. The acid treated polymer shows a conductivity of "'1 Scm-I while the distilled water and base treated samples show conductivity of 10-6 and 10-7 Scm-I, respectively. Surface morphology obtained by SEM provides very interesting results. The acid treated polyaniline seems to consist of agglomerates and stacked over the surface to make a big deposit. On the other hand, distilled water and base treated matrices show granular morphologies. The grain aggregates to a short-pillar like body in the morphology of distilled water treated 2 polyaniline while in the base treated one, the grains are collected to a body like a broken brick-shaped showing definite size and sharp edges. The polyaniline matrices thus treated were used as adsorbent and found to be adsorbed the dyestuffs, methylene blue and procion red from their aqueous solutions at various pH. The removal of dyes was monitored spectroscopically by measuring the change of absorbance at their corresponding ""max. The molar absorption co-efficients of methylene blue and procion red were found to be 59600 L mol-! cm-! at 661 nm and 8518 L mol-! cm-! at 535 nm, respectively. The cationic dye, methylene blue shows a significant adsorption on the base treated polyaniline (negatively charged), while procion red, a negative dye, found to be adsorbed preferentially on the positively charged acid treated polymer. The adsorption isotherms for both methylene blue and procion red seem to follow Langmuir isotherm. However, the inorganic salt, nickel chloride adsorption seems to be very low both on neutral and charged polyaniline matrices suggesting a different mechanism for the adsorption on the polymeric matrices employed.