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A novel, integrated treatment system for coal waste waters. Quarterly report, March 2, 1993--June 1, 1993

Description: The aims of this study are to develop, characterize and optimize a novel treatment scheme that would be effective simultaneously against the toxic organics and the heavy metals present in coal conversion waste waters. In this report, the following findings have been reported and discussed. Hec-CBDA-PA, (HCPA), a modified hectorite containing a mixed bilayer of a cationic (CBDA) and a long chain carboxylic acid (palmitic acid, PA) type surfactants, has been shown to adsorb Cu (II) strongly at pH 6.0 and quantitatively desorb the Cu(II) ions at pH 3.0. The overall mass balance of the adsorption/desorption cycle was quantified and it was found to be between 95 and 107%. Thus, a reversible, batch-wise scheme for the removal and recovery of a cationic heavy metal has been demonstrated. Future plans include repeated operation of the adsorption/desorption cycle. Adsorption of Cr(VI) onto HCDT and MONT-DT at pH 4.5 in presence and in the absence of a potentially competing organic ligand, {beta}-naphthoic acid (NA), shows a limited amount of inhibition of Cr(VI) adsorption by NA. Further, the limiting adsorption density of CR(VI) on the two adsorbents was found to be nearly the same (2.5 - 3.0 mmoles/g), and this value was considerably higher the surface concentration of DT (0.72 and 1.44 mmoles of DT/g adsorbent in the case of HCDT and MONT-DT respectively), which is the active component in the adsorption process. The excess adsorption is postulated to arise from the oxidation of surface organic carbon by CR(VI) and the precipitation of CR(III) as its hydroxide at pH 4.5. Adsorption of NA onto HCDT and MONT-DT as a function of pH in the 4.5 - 9.0 range shows that anion exchange and hydrophobic partitioning are the two dominant mechanisms of NA adsorption onto modified-clays.
Date: September 1, 1993
Creator: Wang, H. Y. & Srinivasan, K. R.