Robert A. Griffin

Effect of pH on adsorption of chromium from landfill‐leachate by clay minerals

Abstract Adsorption of Cr(VI) and Cr(III) species by kaolinite and montmorillonite clay minerals was found to be highly dependent upon the pH of the clay suspensions and the physical‐chemical properties of the clay minerals. Adsorption of Cr(VI) decreased as pH increased and the HCrO4 ‐ ion was the Cr(VI) species predominantly adsorbed. More Cr(VI) was adsorbed from leachate solutions than from pure K2CrO4 solutions. The adsorption of Cr(III) increased as the pH of the suspensions increased. About 30 to 300 times more Cr(III) than Cr(VI) was adsorbed by both clays and the amounts of Cr(III) adsorbed corresponded to cation exchange‐adsorption of hydrolyzed Cr(III) species. The adsorption of Cr(III) is 3% to 14% lower in leachate than in pure Cr(NO3)3 solutions. The results of the study suggest that landfill disposal of Cr(VI) wastes represents a potential pollution hazard due to its high mobility in earth materials and that safe disposal may require conversion of Cr(VI) in the wastes to Cr(III).

Effect of pH on adsorption of copper, zinc, and cadmium from landfill leachate by clay minerals

Abstract The removal (exchange‐adsorption plus precipitation) of Cu, Zn, and Cd from a municipal landfill leachate by kaolinite and montmorillonite was found to be dependent upon the pH and the ionic strength of the leachate. Sorption increased with increasing pH values and with increasing concentration of heavy metals. Montmorillonite sorbed approximately five times more heavy metal from solution than kaolinite. Precipitation contributed significantly to removal of Cu, Zn, and Cd from leachate above pH 6. The removal versus pH data (pH range 2 to 8) were used to construct adsorption isotherms at several pH values. Leachate isotherms were constructed at pH 5.0 and compared with pure aqueous solution isotherms for the same pH. The amount of adsorption at pH 5.0 from leachate was significantly lower than that from pure nitrate salt solutions because of competition from the other cations present in the leachate. Migration of heavy‐metal ions through clay materials is predicted to be much greater in landfill ...

Solubility of polychlorinated biphenyls and capacitor fluid in water

Abstract A quantitative method to determine the solubility of polychlorinated biphenyls (PCBs) and used capacitor fluid in water was developed employing high-resolution glass capillary-column gas chromatography. The responses of the electron capture detector to mono-, di-, tri- and tetra-chlorobiphenyls and an internal standard were used to estimate the solubility of the PCBs. Results of the rate of dissolution of Aroclor 1242 and used capacitor fluid in water indicated that a period of five months was required to reach equilibrium. The water-solubile fractions of Aroclor 1242 and used capacitor fluid (Aroclor 1242-impregnated) were found to be identical. Certain isomers of the mono-, di- and poly-biphenyls in Aroclor 1242 were relatively soluble and were identified as 2-mono-, 2,4′-di-, 2,5.2′-tri-, 2.3,2′-tri-, 2,5.4′-tri-, 2,5.2′,5′-tetra-, 2,4.2′,5′-tetra-, 2,4.2′,4′-tetra-, 2,3.2′,5′-tetra- and 2,4.3′,4′-tetra-chlorobiphenyl. In general, the water-soluble fractions of the PCB mixtures were richer in the lower chlorinated isomers than the original PCB mixtures. The solubilities of Aroclor 1016, 1221, 1242, and 1254 were 906. 3516, 703 and ∼70μg1 −1 , respectively, whereas the solubility of the used capacitor fluid was the same as that of Aroclor 1242.

Mössbauer spectroscopic studies of the mineralogical changes in coal as a function of cleaning, pyrolysis, combustion and coalconversion processes

Abstract The mineralogical changes in a Perry County, Illinois coal from the Herrin (No. 6) Member due to cleaning, pyrolysis, combustion, and coal-conversion processes were studied. Mossbauer spectroscopy was used in tandem with X-ray diffraction to follow the changes in the forms of iron originally present in the coal resulting from processing. The chemistry of the pyrite conversion is less complex than expected. Iron does not become uniformly distributed in all possible minerals but tends to form simple products. Pyrrhotites along with spinel and hydrated ferrous sulphates are the primary mineral products found in coat liquefaction and pyrolysis process residues; while mullite, ferrous silicates and the iron oxides (hematite, geothite and magnetite) are the most abundant mineral products found in Lurgi gasification and power plant fly ashes. The detailed distribution of iron, however, is dependent upon conditions in the particular process equipment in which the coal is used and the conversion process in which it is used.

Adsorption of water‐soluble polychlorinated biphenyl aroclor 1242 and used capacitor fluid by soil materials and coal chars

Abstract Adsorption of the water‐soluble PCBs Aroclor 1242 and a used capacitor fluid (impregnated with Aroclor 1242) by five earth materials and their low‐temperature ashes were studied under constant‐temperature laboratory conditions. The five earth materials studied were medium‐temperature coal char (MTC), high‐temperature coal char (HTC), Catlin soil (CS), montmorillonite clay (MC), and Ottawa silica sand (OS). Adsorption followed the series MTC > HTC > CS > MC > OS. There were no significant differences between adsorption of the Aroclor 1242 and the used capacitor fluid by any of the five earth materials. A simple linear relation described the adsorption of PCBs from aqueous solution by the earth materials and yielded an adsorption constant (K) unique to each adsorbent. Very highly significant (.001 level) linear correlations were found for K as a function of total organic carbon (TOC.), the coefficient of determination, r 2 equals 0.87; K as a function of the surface area measured with carbon dioxid...