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CO2 system containing soluble metal ions
ABSTRACTS
531
INVESTIGATION EFFECT
OF THE CARBONATE
IN CEMENT
DOPED
WITH
METAL IONS AND THE CA(OH)2/CO2 SYSTEM CONTAINING SOLUBLE METAL IONS tl. G. McWhinney and J. R. Williams Prairie View A & M University, Prairie View, Texas 77446
The continued use of cementitous materials, be it ordinary Portland cement, flyash, clays, polymer modified cement, blast furnace slags, or high-alumina and high-lime content cements, poses several unanswered questions. These questions range from the status of the physical integrity to the chemical stability of the solidified cementitous admixtures. The problems are further exacerbated by our lack of knowledge on the speciation of the waste form and the complexity of the solidification media. Over the past five years a tremendous amount of information has surfaced about the chemistry of hazardous metal ions in simple waste forms. This ongoing study provides the following information: 1) There is an enhanced carbonate effect in Portland cement doped with Pb, Hg, Cr, Zn, and Cd, especially in the early stages of hydration; 2) chromium does not exist as a measurable quantity (20 wt.% doping) on the surface of cement grains, but rather as a specie within the cement grains. It would seem that there is a substitution of Cr 3+ ions for Al 3+ ions. Chemical speciation and carbonate quantitation on simple admixture systems will be extended to the studies of systems containing complex metal ion mixtures. Analogs of the Double Shell Slurry Feed (DSSF) will be prepared for both Portland cement and cement grouts. Rigorous characterization by X-Ray Photoelectron Spectroscopy, total carbonate determination by alkimetry, and SEM elemental mapping will be utilized in elucidating solidification and stabilization mechanisms of complex salts in cement and grouts. LONG-TERM PREDICTIONS
OF LEAD, CADMIUM IN
SOLIDIFIED/STABILIZED
DEHALOGENATION AND PCBS WITH ELEVATED THERMAL HEATING
OF PESTICIDES SOLID BASES AT
TEMPERATURES: VERSUS
MICROWAVE
Charles U. Pittman, Jr. and Clifford E. George
LEACHING
AND CHROMIUM
Cr, Pb, As), emission control dust/sludge from steel electric furnaces (K061, Cr, Pb, Cd), wastewater treatment sludges from lead-based initiating compounds (K046,Pb), metal finishing sludges (F006, Cd, Cr, Pb, Ni, and As), distillation tar (K022, Cr, Ni), and wood-preserving sludges(K001, Pb). An effective treatment process for these wastes can be accomplished by using Portland cement (OPC) as the solidification/stabilization (S/S) binder. Additives included with OPC can influence the effectiveness of the process, but the chemistry and especially the long-term behavior of such systems still is not well understood. To gain a more comprehensive understanding of the ability of the solid matrix to confine wastes over long periods of time, several different leaching techniques have been developed, including upflow columns, buffer solutions, and batch leaching procedures. Our goals for the near future are to continue ongoing studies of mixed-metal systems (lead, chromium, cadmium) with chemical binders and additives (phosphates, sulfates, sulfides) and to develop a long-term leaching model based on Fick's law of diffusion to predict the fate of these metals in simulated landfill situations. Batch leaching results of Pb-OPC samples indicate that the diffusion coefficients vary widely depending on sample size. The addition of phosphate can greatly decrease leachability ofOPC S/S systems, especially for lead. Recent results from diffusion experiments show that metal concentrations in the leachant increase and then decrease with time. This phenomena indicates the complexity of the systems and implies that a mechanism exists in which the metals dissolve and then reprecipitate in the cement matrix.
WASTES
J. Dale Ortego Department o f Chemistry, Lamar University, Beaumont, TX 77710
Several industrial processes generate wastes composed of mixtures of inorganic toxic metals. A few of the responsible industries, with their respective waste codes and the toxic metals involved, are: dissolved air floatation float from the petroleum industry (K048-52,
Mississippi State University, Mississzppi State, MS 39762
The dehaiogenation of waste pesticides and PCBs will be studied in the presence of excess solid bases such as CaO, CaO/CaP3, MgO, CaO/MgO, and CaO/NaOH at temperatures from 150°C to about 400°C. Model pesticides such as Mirex and Dieldrin and model PCBs will be individually reacted with solid CaO, or the other solid bases (or their mixtures). These reactions will be carried out with defined amounts of water present in closed reactors at various pressures at specific temperatures. The loss of halogen from the substrates
531
INVESTIGATION EFFECT
OF THE CARBONATE
IN CEMENT
DOPED
WITH
METAL IONS AND THE CA(OH)2/CO2 SYSTEM CONTAINING SOLUBLE METAL IONS tl. G. McWhinney and J. R. Williams Prairie View A & M University, Prairie View, Texas 77446
The continued use of cementitous materials, be it ordinary Portland cement, flyash, clays, polymer modified cement, blast furnace slags, or high-alumina and high-lime content cements, poses several unanswered questions. These questions range from the status of the physical integrity to the chemical stability of the solidified cementitous admixtures. The problems are further exacerbated by our lack of knowledge on the speciation of the waste form and the complexity of the solidification media. Over the past five years a tremendous amount of information has surfaced about the chemistry of hazardous metal ions in simple waste forms. This ongoing study provides the following information: 1) There is an enhanced carbonate effect in Portland cement doped with Pb, Hg, Cr, Zn, and Cd, especially in the early stages of hydration; 2) chromium does not exist as a measurable quantity (20 wt.% doping) on the surface of cement grains, but rather as a specie within the cement grains. It would seem that there is a substitution of Cr 3+ ions for Al 3+ ions. Chemical speciation and carbonate quantitation on simple admixture systems will be extended to the studies of systems containing complex metal ion mixtures. Analogs of the Double Shell Slurry Feed (DSSF) will be prepared for both Portland cement and cement grouts. Rigorous characterization by X-Ray Photoelectron Spectroscopy, total carbonate determination by alkimetry, and SEM elemental mapping will be utilized in elucidating solidification and stabilization mechanisms of complex salts in cement and grouts. LONG-TERM PREDICTIONS
OF LEAD, CADMIUM IN
SOLIDIFIED/STABILIZED
DEHALOGENATION AND PCBS WITH ELEVATED THERMAL HEATING
OF PESTICIDES SOLID BASES AT
TEMPERATURES: VERSUS
MICROWAVE
Charles U. Pittman, Jr. and Clifford E. George
LEACHING
AND CHROMIUM
Cr, Pb, As), emission control dust/sludge from steel electric furnaces (K061, Cr, Pb, Cd), wastewater treatment sludges from lead-based initiating compounds (K046,Pb), metal finishing sludges (F006, Cd, Cr, Pb, Ni, and As), distillation tar (K022, Cr, Ni), and wood-preserving sludges(K001, Pb). An effective treatment process for these wastes can be accomplished by using Portland cement (OPC) as the solidification/stabilization (S/S) binder. Additives included with OPC can influence the effectiveness of the process, but the chemistry and especially the long-term behavior of such systems still is not well understood. To gain a more comprehensive understanding of the ability of the solid matrix to confine wastes over long periods of time, several different leaching techniques have been developed, including upflow columns, buffer solutions, and batch leaching procedures. Our goals for the near future are to continue ongoing studies of mixed-metal systems (lead, chromium, cadmium) with chemical binders and additives (phosphates, sulfates, sulfides) and to develop a long-term leaching model based on Fick's law of diffusion to predict the fate of these metals in simulated landfill situations. Batch leaching results of Pb-OPC samples indicate that the diffusion coefficients vary widely depending on sample size. The addition of phosphate can greatly decrease leachability ofOPC S/S systems, especially for lead. Recent results from diffusion experiments show that metal concentrations in the leachant increase and then decrease with time. This phenomena indicates the complexity of the systems and implies that a mechanism exists in which the metals dissolve and then reprecipitate in the cement matrix.
WASTES
J. Dale Ortego Department o f Chemistry, Lamar University, Beaumont, TX 77710
Several industrial processes generate wastes composed of mixtures of inorganic toxic metals. A few of the responsible industries, with their respective waste codes and the toxic metals involved, are: dissolved air floatation float from the petroleum industry (K048-52,
Mississippi State University, Mississzppi State, MS 39762
The dehaiogenation of waste pesticides and PCBs will be studied in the presence of excess solid bases such as CaO, CaO/CaP3, MgO, CaO/MgO, and CaO/NaOH at temperatures from 150°C to about 400°C. Model pesticides such as Mirex and Dieldrin and model PCBs will be individually reacted with solid CaO, or the other solid bases (or their mixtures). These reactions will be carried out with defined amounts of water present in closed reactors at various pressures at specific temperatures. The loss of halogen from the substrates