Porous carbonaceous adsorbent materials possessing weakly acidic surface functional groups have been evaluated for the selective removal of heavy metals from aqueous solutions. Active carbons derived from both agricultural products (KAU carbons) and polymeric resin (CKC carbon) have been oxidised by hot air or nitric acid to produce samples with different degrees of surface oxidation. A novel phosphorus-containing carbonaceous sorbent (PGP-P) has been prepared by pyrolysis of phosphorylated phenol-formaldehyde resin. Surface modifications have been carried out to introduce various acidic functional groups capable of selective heavy metal binding. The properties of these sorbents have been compared to those of commercially available polymeric carboxylic resin C 104 (Purolite) and oxidised Filtrasorb 400 (Chemviron). Investigation into the physical structure of the adsorbents using microscopy and nitrogen sorption at liquid nitrogen temperatures showed that the porous structure is adversely affected by carbon oxidation. The surface area and pore volume decrease as the degree of surface oxidation increases. The low surface area and pore volume of PGP-P was attributed to the presence of phosphorus-containing functional groups which protect the surface from excessive burn-off. The surface functionality of the sorbcnts was determined by FT-IR, NMR and X-ray photoelectron spectroscopy. Relatively high concentrations of different weakly acidic functional groups were detected on the surface of the materials studied. The ion-exchange properties of the sorbents were assessed by acid-base titration techniques and electrophoretic mobility measurements. Oxidation of carbons with hot air resulted in a greater proportion of relatively weaker type surface functionality (i.e. phenolic) whereas nitric acid modification produced a higher concentration of relatively stronger carboxylic groups. Electrophoretic mobility measurements suggested that the carbon surface is negatively charged within the range of pH values studied. pH titration results demonstrated relatively greater surface acidity of active carbons compared to carboxylic resin. Active carbons were successfully applied for the selective removal of radionuclides. The materials showed excellent decontamination factors for a-, b- and y emitters. This was attributed to the presence of mineral admixtures and humic acids in carbons as well as the surface functional groups. Repeated cycles of lead sorption/elution indicated that the metal capacities of the carbon-packed mini-columns were reduced but reached a steady level after 3-4 cycles.

Thesis (M.S. - Soil, Water and Environmental Science)--University of Arizona. / Includes bibliographical references (leaves 107-111).

Thesis (Ph. D.)--University of California, Davis, 1971. / Includes bibliographical references (leaves 131-146).

Thesis (M. Sc.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on June 18, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering, Department of Civil and Environmental Engineering, University of Alberta. Includes bibliographical references.

Heavy metals have been detected in aquatic and terrestrial environment around the Paducah Gaseous Diffusion Plant (PGDP). However, little is known regarding their accumulation and associated effects in turtles inhabiting aquatic ecosystems near the PGDP. The current study was initiated to evaluate accumulation of heavy metals and its associated effects in aquatic turtle species and to determine species composition and abundance in ponds near the PGDP. A total of 382 turtles composed of 6 species were captured at 6 ponds during 2007 and 2008. Red-eared slider turtles (Trachemys scripta elegans) were the most abundant species (81.2% of the total number of turtles captured), and the abundance and densities ranged from 12 to 88 turtles and from 39 to 122 turtles/ha among study ponds, respectively. Only Cu concentrations in liver tissue differed among ponds, which may be associated with the age of one study pond. However, a gradient of increasing concentrations from ponds upstream to ponds midstream and downstream of the PGDP was observed for Pb and Hg in liver. Copper and Hg were detected in red-eared slider eggs. Copper concentrations in eggs were positively correlated with female Cu concentrations in kidney. Metal concentrations in turtle tissues and sediment were lower than previously reported concentrations associated with adverse effects. Total white blood cell counts, ratios of heterophils to lymphocytes, numbers of lymphocytes and eosinophils, and T-cell mediated immunity were correlated with metal concentrations. Hematocrits were not correlated with any metal concentrations in any tissues. Hemoparasites were observed in 40.7% of the red-eared slider turtles studied. Concentrations of heavy metals in turtle tissues, eggs, and sediment measured in the current study were low, and are not thought to be adversely affecting aquatic turtles near the PGDP. Although some hematological and immunological indices were correlated with some metal concentrations, further studies are needed to determine if these effects are associated with metal exposure, with hemoparasites, or other contaminants or disease.

No description available.

Exchange adsorption of Cu²⁺ , Pb²⁺ and Zn²⁺ for Na on Wyoming mont-morillonite, in chloride and nitrate electrolyte solutions less than 10⁻³ M total heavy metal concentration, can be modelled with a simple equilibrium ion-exchange reaction: Me²⁺ + 2 Na{Mont} = Me{Mont}₂ + 2 Na⁺ where Me. and Mont represent a given heavy metal and montmorillonite. Equilibrium constants for this reaction are equal for Cu²⁺ and Zn²⁺ at 3.0 ± 1, slightly less than that for Pb²⁺ at 5.0 ± 1, and comparable to constants calculated for monopositive exchange of K⁺ for Na⁺ (3.0 ± 1) and H⁺ for Na⁺ (2.5 ± .5). Above 10⁻³ M total metal concentration, heavy metal exchange for Na is complicated by variable total Na exchange capacity and by apparent anionic interferences. CuCl₂ and ZnCl₂ electrolyte solutions are more effective Na exchangers at 0.1 M than Cu(NO₃)₂, Pb(NO₃)₂, KC1 or HC1 solutions at the same concentration. Retardation factors of Cu, Pb and Zn spots eluted across thin layers of Na-montmorillonite (supported by silica gel) by aqueous NaCl and NaNO₃ solutions of 0.05 to 3.0 M concentration suggest, when interpreted with a rudimentary ion-exchange mass transfer model, that metals migrate mainly as monopositive species—perhaps as monohydroxo-complexes within the clay micelle. Precipitation of Pb chloride or hydroxy-chloride is indicated by multiple Pb spots on NaCl-eluted chromatograms. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The evidence of heavy metal build up in the aquatic environment near sewage treatment plant outfalls around Vancouver,coupled with the generally held theory that secondary treatment is not required in this area, leads to the conclusion that a treatment method is required that is primarily aimed at heavy metal removal. In this study, jar tests were performed to evaluate the heavy metal removal efficiency of the lime-magnesium coagulation process. Five heavy metals (Cr³⁺ , Cu²⁺ , Pb²⁺ , Ni²⁺ and Zn²⁺ ) were all tested at initial concentrations of .5, 2.5 and 5.0 mg/1 individually and in combination. The experiments were performed on prechlorinated primary effluent and raw sewage at the natural alkalinity levels (120-130 mg/1 as CaCO₃), and some work was done at elevated alkalinity (190-200 mg/1). The need for filtration in the process was also researched. Results of the study indicated that the heavy metal removal efficiency was enhanced by the presence of Mg²⁺ at a given lime dosage for all of the heavy metals except nickel. A comparison indicated that intermediate lime treatment (220 mg/1) coupled with 33 mg/1 Mg²⁺ might be a more attractive process than just straight high lime treatment (400 mg/1). / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

No description available.

Thesis (M.Sc.) -- University of Limpopo, 2005 / Six aerobic bacterial strains [GM 10(1), GM 10 (2), GM 14, GM 15, GM 16 and GM 17] were isolated from an antimony mine in South Africa. Heavy-metal resistance and biosorptive capacities of the isolates were studied. Three of the isolates (GM 15, GM 16 and GM 17) showed different degrees of resistance to antimony and arsenic oxyanions in TYG media. The most resistant isolate GM 16 showed 90 % resistance, followed by GM 17 showing 60 % resistance and GM 15 was least resistant showing 58 % resistance to 80 mM arsenate (AsO4 3-). GM 15 also showed 90 % resistance whereas isolates GM 16 and GM 17 showed 80 % and 45 % resistance respectively to 20 mM antimonate (SbO4 3-). Arsenite (AsO2 -) was the most toxic oxyanion to all the isolates. Media composition influenced the degrees of resistance of the isolates to some divalent metal ions (Zn2+, Ni2+, Co2+, Cu2+ and Cd2+). Higher resistances were found in MH than in TYG media. All the isolates could tolerate up to 5 mM of the divalent metal ions in MH media, but in TYG media, they could only survive at concentrations below 1 mM. Also, from the toxicity studies, high MICs were observed in MH media than TRIS-buffered mineral salt media. Zn2+ was the most tolerated metal by all the isolates while Co2+ was toxic to the isolates. The biosorptive capacities of the isolates were studied in MH medium containing different concentrations of the metal ions, and the residual metal ions were determined using atomic absorption spectroscopy. GM 16 was effective in the removal of Cu2+ and Cd2+ from the contaminated medium. It was capable of removing 65 % of Cu2+ and 48 % of Cd2+ when the initial concentrations were 100 mg/l, whereas GM 15 was found to be effective in the biosorption of Ni2+ from the aqueous solutions. It was capable of removing 44 % of Ni2+ when the initial concentration was 50 mg/l. GM 17 could only remove 20 % of Cu2+ or Cd2+. These observations indicated that GM 16 could be used for bioremediation of xvi Cu2+ and Cd2+ ions from Cu2+ and Cd2+-contaminated aqueous environment, whereas GM 15 could be used for bioremediation of Ni2+. / National Research Foundation and the University of the North Research Unit