Oxidants

EXAMPLE 5

The antioxidant potential of Extracts 1-3 and 6-9 was analyzed using a kit by Oxford Biomedical Research, P.O. Box 522, Oxford MI 48371. This colorimetric microplate assay allows comparison of each Extract 1-3 and 6-9 to a standard to determine the total copper reducing equivalents. Generally the assay was performed by preparing the standards, and allowing dilution buffer, copper solution and stop solution to equilibrate to room temperature for about 30 minutes prior to running the assay. Both Extracts 1-3 and 6-9 samples and standards were diluted 1:40 in the provided dilution buffer (e.g. 15 mL serum+585 mL buffer). Next, 200 mL of diluted Extract samples or standards were placed in each well. The plate was read at 490 nanometers (nm) for a reference measurement. Then 50 mL of Cu++ solution was added to each well and incubated about 3 minutes at room temperature. 50 mL of stop solution was added and the plate read a second time at 490 nm.

The data in Table 15 demonstrates the antioxidant potential of each of Extracts 1-3 and 6-9 at two different concentrations. The data further explains the effectiveness of extracts against damaging oxidant or ROS events (above discussed) generated during in vitro processing of reproductive cells.

Example 2

In a reaction bottle, p-cyanoaniline (59 mg, 0.5 mmol), catalyst (28 mg, 0.05 mmol), di-tert-butyl peroxide (138 μL, 0.75 mmol), and toluene (7 mL) were added sequentially. The reaction was carried out at 120° C. for 24 hours. After the reaction was complete, the reaction mixture was cooled to room temperature. The product was purified by column chromatography eluting with ethyl acetate/petroleum ether with a volume ratio of 1:50, a yield of 88%.

When iron bromide (10 mol %) was used as the catalyst, the yield was only 8%. When tert-butyl hydroperoxide (1.5 times) was used as the oxidizing agent, the yield was only 22%.

The product was dissolved in CDCl₃ (ca. 0.4 mL), sealed, and characterized on a Unity Inova-400 NMR apparatus at room temperature: ¹H NMR (400 MHz, CDCl₃, TMS): 7.38-7.28 (m, 7H), 6.58-6.55 (m, 2H), 4.73 (s, 1H), 4.35 (s, 2H) ppm.

Example 3

Optimum dosage of reagent may increase the efficiency of leaching. First, at certain concentrations, the reagent may form an insoluble complex with the metal ion of interest and precipitate. For example, Tu can form an insoluble complex with Cu(I) ions at a 3:1 molar ratio. A precipitation test was performed to examine the concentration range at which Cu-Tu complex precipitation may occur. 20 mL of Cu solution was divided into several identical portions followed by the addition of various Tu dosage (i.e. 0 to 60 mM). The solution was stirred for 24 hours, and the Cu remaining in the solution phase was analyzed by AAS. The results are shown in FIG. 17, plotted as the percentage of Cu remaining.

Second, heap leaching of metal sulfides is based on a bioleaching mechanism, an excessive amount of reagent may be detrimental to bioleaching microbes. For example, bacteria commonly used for bioleaching, such as Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, have very slow growth in a solution containing 10 mM Tu, and cannot survive at 100 mM Tu.

Third, with respect to Tu specifically, ferric reacts with Tu and converts it to FDS (see Hydrometallurgy 28, 381-397 (1992)). Although the reaction is reversible under certain conditions, a high concentration of FDS tends to decompose irreversibly into cyanamide and elemental sulfur (see J Chromatogr 368, 444-449).
2Tu+2Fe³⁺↔FDS+2Fe²⁺+2H⁺FDS→Tu+cyanimide+S

Therefore, over-addition of Tu in the lixiviant may cause the loss of Fe³⁺ and Tu due to oxidation and decomposition. The irreversible decomposition of FDS has been observed when adding 4 mM of Tu into a 40 mM ferric sulfate solution at pH 1.8.

To further investigate the effect of Tu dosage on copper extraction, stirred reactor tests were performed using 1 g of synthetic chalcopyrite in 1.9 L of 40 mM ferric sulfate solution at pH 1.8 with various initial Tu concentrations. The treatments were run for 172 hours to approach maximum extraction. The results are presented in FIG. 18, and shows that, for 1 g of chalcopyrite, higher Tu dosage results in faster leaching kinetics among the Tu concentrations tested.

For Tu dosages of 5 mM and under, the initial 40 mM ferric sulfate solution can be considered as a sufficient supply of oxidant. However, for higher dosages such as 10 mM and 20 mM of Tu, extra ferric (in 1:1 ratio with Tu) had to be added to the solution to allow the oxidation of Tu to FDS. For 10 mM Tu, an extra 10 mM of Fe³⁺ was added at time zero. For 20 mM Tu, an extra 20 mM of Fe³⁺ was added at 72 hours, which led to the continuation of extraction as shown in FIG. 18.

The Tu dosage vs. Cu extraction at 172 hours is plotted in FIG. 19. An initial Tu dosage up to 5 mM appears to have the most pronounced effect on the dissolution of Cu.

As indicated above, in previous shakeflask tests with acidic solutions (pH 1.8) containing various concentrations of Fe³⁺ and Cu²⁺ ions, slight precipitation occurred upon the addition of 4 mM of Tu due to the decomposition of FDS. Accordingly, concentrations of Tu concentration below 4 mM may avoid such precipitation. A series of shakeflask tests were performed on solutions containing initial concentrations of 2 mM Tu and various concentrations in a matrix containing Fe³⁺ (0-100 mM) and Cu²⁺ (0-50 mM) in order to identify concentration ranges of [Fe³⁺] and [Cu²⁺] that do not result in Cu complex precipitation. The results showed that no precipitation and no loss of Cu from the solution phase resulted using 2 mM of Tu in this wide range of Fe and Cu matrix concentrations.