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

Abstract

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 highermore » 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.« less

Authors:
;
Publication Date:
Research Org.:
Michigan Univ., Ann Arbor, MI (United States). Dept. of Chemical Engineering
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10178689
Report Number(s):
DOE/PC/91295-T7
ON: DE93040627
DOE Contract Number:
FG22-91PC91295
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: [1993]
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; COAL GASIFICATION PLANTS; WASTE WATER; COAL LIQUEFACTION PLANTS; WATER TREATMENT; PROGRESS REPORT; COPPER; ADSORPTION; DESORPTION; PH VALUE; SURFACTANTS; CARBOXYLIC ACIDS; MATERIALS RECOVERY; CHROMIUM; CATIONS; CLAYS; REMOVAL; 010800; WASTE MANAGEMENT

Citation Formats

Wang, H.Y., and Srinivasan, K.R. A novel, integrated treatment system for coal waste waters. Quarterly report, March 2, 1993--June 1, 1993. United States: N. p., 1993. Web. doi:10.2172/10178689.
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Wang, H.Y., & Srinivasan, K.R. A novel, integrated treatment system for coal waste waters. Quarterly report, March 2, 1993--June 1, 1993. United States. doi:10.2172/10178689.
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Wang, H.Y., and Srinivasan, K.R. Wed . "A novel, integrated treatment system for coal waste waters. Quarterly report, March 2, 1993--June 1, 1993". United States. doi:10.2172/10178689. https://www.osti.gov/servlets/purl/10178689.
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@article{osti_10178689,
title = {A novel, integrated treatment system for coal waste waters. Quarterly report, March 2, 1993--June 1, 1993},
author = {Wang, H.Y. and Srinivasan, K.R.},
abstractNote = {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.},
doi = {10.2172/10178689},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Sep 01 00:00:00 EDT 1993},
month = {Wed Sep 01 00:00:00 EDT 1993}
}
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Technical Report:
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DOI:  10.2172/10178689
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  • ;
    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. Acid-base titration of Duomeen-T (DT), a diamine surfactant, that has been used in this study to modify smectite surfaces to form smectite-DT complexes has been undertaken. In aqueous medium containing 5% by volume iso propyl alcohol (IPA), DT shows a broad distribution of pKa with a mean value of 7.55. This finding suggests that DTmore » is a much weaker base than a typical diamine and helps explain the fact that Cu(II) adsorbs specifically onto DT with maximal affinity in the pH range 7.2--7.5. Electrokinetic sonic amplitude (ESA) measurements on DT-smectite complexes also reveal that the mean pKa of the adsorbed DT is around 7.0. This finding supports our earlier observations that Cu(II) and Cd(II) cations bind strongly through specific interaction to DT-smectite surface in the pH range 7.0--8.0. Our results also show that DT is fully protonated at pH 4.5, and it is at this pH that Cr(VI) is maximally adsorbed as counterions to the DT-smectite surface. These and our earlier results provide a firm basis to conclude that a heterogeneous mixture of diamine surfactants can be used to adsorb and desorb cationic and anionic heavy metals from their respective aqueous solutions as a function of the solution pH.« less

  • ;
    One of the specific aims of the study has been to remove and recover cationic and anionic heavy metals from aqueous solutions using modified-clay adsorbents developed in this study. To this end, hectorite-CBDA-DT (HCDT), one of the adsorbents the authors have so far prepared, has been used in a multi-step adsorption/desorption process. Briefly, the multi-step adsorption/desorption process involves initially contacting the adsorbent with a solution of heavy metal ion (Cu(II) or Cr(VI)) at a pH which corresponds to maximal adsorption of the respective metal ion (7.4 or 8.8 for Cu(II) and 3.5--4.0 for Cr(VI)). Desorption of adsorbed metal ion ismore » effected by adjusting the solution pH to a value at which the respective metal ion is optimally desorbed (3.0 for Cu(II) and 10.0 for Cr(VI)). Multi-step involves cycling the same adsorbent through the two pH values repeatedly. Results indicate that, for Cu(II) ions, HCDT can be used at least 5 times and the loss of adsorption (removal) and desorption (recovery) efficiency is only 15% of the initial value. Further, the overall mass balance of the Cu(II) system is 95%. However, with Cr(VI), the same adsorbent loses more than 40% of its potency after 4 cycles. Further, the overall mass balance averages to only 75% in the case of Cr(VI) removal and recovery. It is believed that differences in the operational performance in the two cases can be attributed to different adsorption mechanisms: surface chelate formation (dependent only on local pH) and counter ion binding (responsive to local pH and ionic strength) respectively in the case of Cu(II) and Cr(VI).« less

  • ; ;
    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. A specific goal of the study is to remove and recover cationic and anionic heavy metals from aqueous solutions and coal conversion waste waters using modified-clay adsorbents developed in this study. To this end, a multi-step adsorption/desorption process has been carried out with hectorite-CBDA-DT (HCDT) as the adsorbent and Cr(VI) as the adsorbate. Adsorption was carried out at pH 4.0 in 0.02 M buffer, while desorptionmore » was effected at the same pH and in the same buffer with either 0.5 M NaCl or 0.02 M Na{sub 2}SO{sub 4} as the desorbates. Multi-step involves cycling the same adsorbent through these two sets of operating conditions with a washing step after each adsorption/desorption sequence. The authors results indicate that, during the first two cycles, the potency of the adsorbent remains unchanged, but it diminishes after the third and the fourth cycles. The total decrease in potency is, however, only 15% even after 4 cycles of adsorption/desorption. Addition of 20% isopropyl alcohol (IPA) to the reaction medium, however, diminishes the potency even more after 4 cycles of adsorption and desorption. Both the desorbates yielded identical results, and the overall mass balance on Cr(VI) was between 95 and 102%. Continuous leaching experiments on HCDT revealed that DT bound to HCDT is mobilized to the extent of only 10% after 44 hrs in aqueous medium while in 20% IPA-water mixtures the extent of dissolution of DT from the surface is close to 16%. Thus, the loss of potency of HCDT is attributed partly to the loss of DT from the surface and partly to the incomplete washing of the adsorbent between each adsorption/desorption step.« less

  • ;
    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. Adsorption of {beta}-naphthoic acid (NA) onto hectorite-CBDA containing different amounts of adsorbed CBDA is pH dependent, stronger at pH 4.5 and much weaker at pH 8.6. Partitioning into the hydrophobic patches of hectorite-CBDA and binding as counter ion to CBDA bilayers appear to be the dominant mechanisms of adsorption of NA to hectorite-CBDA. Anionic CR(VI)more » adsorbs very weakly to MONT-DT at pH 8.5 and this result verifies our earlier finding that the positive surface charge on MONT-DT decreases with increasing pH above pH 7.0. Potentiometric titrations of DT in water-isopropyl alcohol (EPA) binary solutions containing different volume fractions of IPA reveal that the pKa of DT is 7.6 {+-} 0.1 independent of EPA volume fraction. It is also shown that DT forms emulsions at pH lower than 4.0 and these emulsions tend to break up as pH is raised above 6.5. The formation of DT emulsions is reversible with respect to pH, but the process appears to be slow with a time constant of about 30 minutes.« less

  • ;
    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. A specific goal of the study is to remove and recover cationic and anionic heavy metals from aqueous solutions and coal conversion waste waters using modified-clay adsorbents developed in this study. We have carried out multi-step adsorption/desorption studies with these adsorbents which indicate that modified-smectites can be repeatedly used up to 5 times with less than 15% loss in their potency. Thus, it would appear thatmore » the DT coatings on DT-modified clays are quite stable. Continuous leaching experiments have been undertaken to verify the stability of adsorbed DT on DT-modified smectites, HCDT and MONT-DT. Potentiometric titrations and ESA measurements at different time intervals have been used respectively to determine the surface charge density and the sign of surface charge of DT-modified smectites. Our results show that, even after 44 hours of continuous leaching of DT-modified smectites by deionized water, the surface charge density as measured by pH titration is lower by less than 10% of its initial value. Further more, the surface charge remains positive in the pH range of 9.5-3.0. These results are in agreement with our earlier results based on Ninhydrin assay and organic carbon analysis of the same DT-modified smectites.« less