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A Novel Integrated Treatment Systems For Coal Wastewaters Quarterly Report June 2 1992 September 1 1992
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Book Synopsis A Novel, Integrated Treatment Systems for Coal Wastewaters. Quarterly Report, June 2, 1992--September 1, 1992 by :
Download or read book A Novel, Integrated Treatment Systems for Coal Wastewaters. Quarterly Report, June 2, 1992--September 1, 1992 written by and published by . This book was released on 1992 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 heavy metals present in coal conversion wastewaters. Hec-CBDA-DT, a modified hectorite containing a mixed bilayer of a cationic (CBDA) and a diamine (DT) type surfactants, was shown to adsorb simultaneously heavy metals such as Cu{sup 2+} and Cd{sup 2+} and toxic organics such as chlorophenols. The pH dependence of the adsorption of chlorophenols on Hec-CBDA-DT suggested hydrophobic partitioning, counterion adsorption and hydrogen-bond interaction of the phenolate ions with the surface diamine groups as the possible mechanisms of sorption. Adsorption of Cu{sup 2+} by Hec-CBDA-DT was shown to be only slightly affected by a large excess of counterions, thus indicating that Cu{sup 2+} adsorbed specifically to the surface. A second type of modified clay, Hec-CBDA-Palmitic Acid (Hec-CBDA-PA) adsorbed both Cu{sup 2+} and Cd{sup 2+} strongly. However, the pH optima for adsorption were 6.0 and 8.0 respectively in the case of Cu{sup 2+} and Cd{sup 2+}. It is inferred that the mechanisms of adsorption of these two metal ions to Hec-CBDA-PA are different, specific and counterion binding respectively in the case of Cu and Cd ions.
Book Synopsis A Novel, Integrated Treatment System for Coal Wastewaters. Quarterly Report, September 2, 1992--December 1, 1992 by :
Download or read book A Novel, Integrated Treatment System for Coal Wastewaters. Quarterly Report, September 2, 1992--December 1, 1992 written by and published by . This book was released on 1992 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 wastewaters. Hec-CBDA-DT, (HCDT), a modified hectorite containing a mixed bilayer of a cationic (CBDA) and a dismine (DT) type surfactants, has been shown to adsorb Cr (VI) strongly at PH below 5.0. A second kind of a modified clay, montmorillonite-DT, (MONT-DT), in which the protonated form of the diamine is directly attached to the negative sites of clay surface, has also been found to adsorb CR(VI) as strongly as Hec-CBDA-DT at a pH of 4.5. The adsorption of Cr (VI) onto these two modified-clays is strongly inhibited by an increase in the ionic strength of the medium. It is inferred that the main mechanism of adsorption of CR(VI) onto these two clay complexes is of the counterion. Preliminary data on the partitioning of phenanthrene, a three-ringed polyaromatic hydrocarbon (PAH), reveal that organic carbon located on the external surfaces of clay complexes is more effective in partitioning nonionic, toxic organic compounds.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Novel Integrated Treatment System for Coal Wastewaters. Quarterly Report, March 2, 1992--June 1, 1992 by :
Download or read book A Novel Integrated Treatment System for Coal Wastewaters. Quarterly Report, March 2, 1992--June 1, 1992 written by and published by . This book was released on 1992 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 heavy metals present in coal conversion wastewaters. To remove and recover heavy metals from wastewaters, four different types of surfactant-clay complexes have been prepared using hectored or montmorillonite as the base clays. The adsorbent is prepared by first coating the clay surface, upto a monolayer, with a cationic surfactant, CBDA, to which an amine, (DT), or a carboxylic acid (Palmitic acid, PA) is anchored using hydrophobic effect to form a mixed bilayer. Such an arrangement is expected to locate the functional groups in metal adsorption at the solid-solution interface. Complexes based on hectored are shown to adsorb Cu{sup 2+} ions more strongly than the ones based on montmorillonite. The rate of adsorption of Cu{sup 2+} ions is quite rapid and the adsorbed amount levels off in less than 2 hrs. The optimum pH for metal adsorption is around 6.5 and the amount of metal adsorbed declines sharply on the lower pH side of the pH optimum, suggesting that removal and recovery of adsorbed metal ions can be effected by a slight pH shift.
Book Synopsis A Novel, Integrated Treatment System for Coal Wastewaters. Quarterly Report, December 2, 1992--March 1, 1993 by :
Download or read book A Novel, Integrated Treatment System for Coal Wastewaters. Quarterly Report, December 2, 1992--March 1, 1993 written by and published by . This book was released on 1993 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 wastewaters. 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. Increasing concentrations of NaCl reduce the affinity of CU(II) adsorption onto HCPA. For example, the binding constants for CU(II) adsorption onto HCPA at pH 6.0 are 88 and 35 mM−1 at 20 and 200 mM NaCl respectively. The saturation binding capacity is also observed to decrease from 0.25 to 0.12 mmoles Cu(II)/g adsorbent in the same ionic strength range. Spectral properties of Cu(II)-DT complex have been examined. Our previous results had shown that DT, an alkyl diamine, binds Cu(II) strongly at pH 7.4, but very weakly at pH 3.0. The formation of Cu(II)-DT complex at pH 7.4 produces an intense blue color and spectral measurements at 626 mn reveal a stoichiometric ratio of 3:1 for the DT-Cu(II) complex. [beta]-naphthoic acid, a organic acid (pKa = 4.17), has been used to probe the pH dependent surface charge of montmorillonite-DT (MONT-DT) complex. Our results indicate that bulk of the surface diamines are de-protonated above pH 9.0.
Book Synopsis Government Reports Annual Index by :
Download or read book Government Reports Annual Index written by and published by . This book was released on 1994 with total page 1372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Government Reports Announcements & Index by :
Download or read book Government Reports Announcements & Index written by and published by . This book was released on 1994-10 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Novel, Integrated Treatment System for Coal Wastewaters. Quarterly Report, September 2, 1991--December 1, 1991 by :
Download or read book A Novel, Integrated Treatment System for Coal Wastewaters. Quarterly Report, September 2, 1991--December 1, 1991 written by and published by . This book was released on 1991 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first quarterly report of the above project. 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 inorganics present in coal conversion wastewaters. The initial phase of the work has been focused on the development of modified clays for use in the selective removal and recovery of heavy metals such as Cd, Cu, chromate and selenate. The results presented here show that a surfactant-modified clay adsorbs Cd strongly at a pH of 8.5 and poorly at pH 4.0. Further, the adsorption of Cd on modified clay is unaffected by the ionic strength of the medium. In the case of Cu, it has been shown that the metal forms a complex with alkyl diamines in aqueous solutions at a pH of 6.0 and does not bind to these surfactants at a lower pH of 3.0. These findings are a preliminary indication that the surface and solution chemistry of amine surfactants can be gainfully modified to adsorb and desorb cationic heavy metals.
Book Synopsis A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, June 2, 1993--September 1, 1993 by :
Download or read book A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, June 2, 1993--September 1, 1993 written by and published by . This book was released on 1993 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 DT 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.
Book Synopsis A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, September 2, 1993--December 1, 1993 by :
Download or read book A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, September 2, 1993--December 1, 1993 written by and published by . This book was released on 1993 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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) 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.
Book Synopsis A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, March 2, 1993--June 1, 1993 by :
Download or read book A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, March 2, 1993--June 1, 1993 written by and published by . This book was released on 1993 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, March 2, 1994--June 1, 1994 by :
Download or read book A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, March 2, 1994--June 1, 1994 written by and published by . This book was released on 1994 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 desorption was effected at the same pH and in the same buffer with either 0.5 M NaCl or 0.02 M Na2SO4 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.
Book Synopsis A Novel, Integrated Treatment System for Coal Wastewaters by :
Download or read book A Novel, Integrated Treatment System for Coal Wastewaters written by and published by . This book was released on 1991 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first quarterly report of the above project. 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 inorganics present in coal conversion wastewaters. The initial phase of the work has been focused on the development of modified clays for use in the selective removal and recovery of heavy metals such as Cd, Cu, chromate and selenate. The results presented here show that a surfactant-modified clay adsorbs Cd strongly at a pH of 8.5 and poorly at pH 4.0. Further, the adsorption of Cd on modified clay is unaffected by the ionic strength of the medium. In the case of Cu, it has been shown that the metal forms a complex with alkyl diamines in aqueous solutions at a pH of 6.0 and does not bind to these surfactants at a lower pH of 3.0. These findings are a preliminary indication that the surface and solution chemistry of amine surfactants can be gainfully modified to adsorb and desorb cationic heavy metals.
Book Synopsis A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, 2 December 1993--1 March 1994 by :
Download or read book A Novel, Integrated Treatment System for Coal Waste Waters. Quarterly Report, 2 December 1993--1 March 1994 written by and published by . This book was released on 1994 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 is 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).
Book Synopsis A Novel, Integrated Treatment System for Coal Waste Waters by :
Download or read book A Novel, Integrated Treatment System for Coal Waste Waters written by and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Novel, Integrated Treatment Systems for Coal Wastewaters by :
Download or read book A Novel, Integrated Treatment Systems for Coal Wastewaters written by and published by . This book was released on 1992 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 heavy metals present in coal conversion wastewaters. Hec-CBDA-DT, a modified hectorite containing a mixed bilayer of a cationic (CBDA) and a diamine (DT) type surfactants, was shown to adsorb simultaneously heavy metals such as Cu[sup 2+] and Cd[sup 2+] and toxic organics such as chlorophenols. The pH dependence of the adsorption of chlorophenols on Hec-CBDA-DT suggested hydrophobic partitioning, counterion adsorption and hydrogen-bond interaction of the phenolate ions with the surface diamine groups as the possible mechanisms of sorption. Adsorption of Cu[sup 2+] by Hec-CBDA-DT was shown to be only slightly affected by a large excess of counterions, thus indicating that Cu[sup 2+] adsorbed specifically to the surface. A second type of modified clay, Hec-CBDA-Palmitic Acid (Hec-CBDA-PA) adsorbed both Cu[sup 2+] and Cd[sup 2+] strongly. However, the pH optima for adsorption were 6.0 and 8.0 respectively in the case of Cu[sup 2+] and Cd[sup 2+]. It is inferred that the mechanisms of adsorption of these two metal ions to Hec-CBDA-PA are different, specific and counterion binding respectively in the case of Cu and Cd ions.
Book Synopsis A Novel, Integrated Treatment System for Coal Waste Waters by :
Download or read book A Novel, Integrated Treatment System for Coal Waste Waters written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
