Low Levels Of Cyanide Research Articles

Gold recovery from cyanide-starved glycine solutions in the presence of Cu using a molecularly imprinted resin (IXOS-AuC)

The synergistic leaching system using glycine as the main lixiviant with low levels of cyanide as a catalyst has been shown to be an effective approach to leach gold‑copper ores and concentrates, allowing the consumption of cyanide to be remarkably reduced. The recovery of gold from the synthetic cyanide-starved glycine leachate in the presence of copper has been investigated using. It was found that the adsorbed copper was mostly cuprous cyanide. The effects of [CN−]:[CuT] and [Gly]: [CuT] molar ratios were not significant on the adsorption of gold and copper using IXOS-AuC resin. The gold recovery increased, while the copper recovery decreased with the increasing initial gold concentration. The equilibrium and kinetics studies were undertaken, and the experimental adsorption equilibrium and rate data showed an excellent fit using the Freundlich isotherm and pseudo-second-order models respectively. Elution tests showed that the loaded copper can be selectively pre-eluted over gold by 0.4 M NaCN at pH 11.5. Gold can be effectively eluted by either acidic thiourea or alkaline thiocyanate. The multi-cycle adsorption/elution tests showed that the resin can be effectively regenerated by both acidic thiourea and alkaline thiocyanate, with an insignificant decrease in adsorption and elution efficiency over 3 adsorption/elution cycles. From SEM analysis, the change of surface morphology of the resin was not significant after adsorption and the adsorption/elution cycles.

Nutritional Composition and Acute Toxicity Potentials of Archontophoenix tukeri and Adonidia merrilli Kernels

Archontophoenix tukeri and Adonidia merrilli are exotic species widely grown in Nigeria as ornamental palms. In this study, the kernels of A. tukeri and A. merrilli were subjected to amino acids, fatty acids, proximate, anti-nutrients and mineral element analyses, in addition to acute toxicity evaluation. Glutamic acid (11.30 and 5.33 g/100 g) and leucine (5.9 and 4.2 g/100 g) were the most abundant essential and non-essential amino acids; the fatty acids profile revealed three major fatty acids: palmitic acid (20.14 and 11.27%), oleic acid (61.83 and 25.78%) and linoleic acid (13.05 and 55.26%); low linolenic acid levels were also observed (˂1%) with 75.87 and 81.98% total unsaturated fatty acids in A. tukeri and A. merrilli respectively. Carbohydrate (85.73% and 90.15%) and oxalate contents (1927.2 and 2072.4 mg/100 g) were relatively high, while low levels of cyanide (12.05 and 65.45 mg/100 g), phytates (6.32 and 2.53 mg/100 g) and tannins (35.36 and 20.16 mg/100 g) were observed. A. tukeri indicated higher Ca, Cu, Fe, Zn, Mg, Mn and Na contents. The anti-nutrient-mineral ratios were computed and compared with critical values. Acute toxicity of A. tukeri and A. merrilli was 866.03 mg/Kg. These palms contain vital nutritional components, and with proper processing could serve as potential products for both human and animal nutrition.

Effect of carbon on the solubility of nitrogen in slag

Abstract The effect of carbon on nitrogen solubility in slag was investigated for the ternary CaO–MgO–SiO2 and the quaternary Al2O3–CaO–MgO–SiO2 slag systems at 1873 K under controlled oxygen and nitrogen potentials. Gas–slag equilibration experiments were conducted using molybdenum and graphite crucibles. In the absence of carbon, the nitrogen solubility was very low. The presence of carbon greatly increased the nitrogen solubility in slag. The total nitrogen content was found to increase with SiO2 and MgO concentration for the carbon saturated slags. Low levels of cyanide were found by wet chemistry with considerable uncertainty. The results analyzed by different methods ruled out cyanide formation being the main reason for the large increase in nitrogen solubility in the presence of pure carbon.

Reactivity of red palm oil and cyanide ion: implications for the cyanogen content of palm oil-treated gari.

Red palm oil was tested for the reactivity of its components with CN-, and alkaline picrate as the color developing reagent. Palm oil components have a low-level absorbance at 490 nm which is reduced significantly (p< or =0.01) after reaction with CN-. Hydrolysis of palm oil components, and reaction of the hydrolysis products with CN- significantly increased the absorbance at 490 nm. In contrast, after reaction of palm oil with alkaline picrate, the absorbance at 490 nm is very high; this is reduced significantly by reaction with CN-, hydrolysis with 0.2 M NaOH, and reaction of the hydrolysis products with CN- before treatment with alkaline picrate. The results indicate that palm oil component(s) sequester CN- into a complex which may not be correctly estimated during cyanide quantification, resulting in the absence, or low levels of cyanide in palm oil-fried gari as earlier reported.

Nutritional and Toxicological Properties of Dika Fat (Irvingia gabonensis)

ABSTRACT The seeds of Irvingia gabonensis (African mango) contain 54 percent fat. Investigation indicates no unusual fatty acids, but the oil was rich in β-carotene, plant sterols, phospholipids, and saturated fatty acids. Toxicological studies indicated low levels of cyanide and gossypol, but no mycotoxins in the fat. The gum content of the seeds was also relatively high. This study is a strong recommendation for further assessment of the fat to establish suitability for use in the food and other allied industries.

Spectrophotometric method for the determination of total cyanide in wastewater samples

A sensitive spectrophotometric method is described for the detection of low cyanide levels in wastewaters. Wastewaters often contain sulphide and addition of lead carbonate is the recommended method for removal of sulphide interference. However, we have found that addition of lead carbonate is unsatisfactory. The addition of a stoicheiometric amount of lead to remove the sulphide interference, this amount being determined by titration with lead acetate using a redox electrode for end-point determination, is more satisfactory. The precision and recoveries (average 91%) obtained with this modified procedure were acceptable.

Direct Determination of Cyanide in Seawater

A rapid and precise method is presented for the direct determination of cyanide in otherwise unpolluted seawater using a cyanide ion-selective electrode. Although chloride interferes significantly at low cyanide levels its effect can be almost completely elmimiated by approproate selectivity corrections allowing determination of cyanide to less than 20 μg/1. The cyanide electrode can also be used for continuous monitoring at levels of interest in toxicological research.

Influence of aeration on hydrogen cyanide biosynthesis byPseudomonas aeruginosa

Batch cultures ofPseudomonas aeruginosa were able to produce only low levels of cyanide during logarithmic growth with adequate aeration. The reduction of aeration caused a rapid increase in the ability of such cultures to produce hydrogen cyanide. The immediacy and the magnitude of this response depended on the oxygen level, with a concentration of 4% in the aeration gas giving optimal results. The reestablishment of normal aeration resulted in a cessation of the increase of the culture's cyanogenic capacity. This effect appeared to be a combination of inactivation of the hydrogen cyanide synthase and repression of synthesis of this enzyme.

Changes in some chemical constituents during the fermentation of cassava tubers ( Manihot esculenta, Crantz)

Cassava tuber, Manihot esculenta, Crantz, was processed, after five days of fermentation, into ‘gari’ and ‘lafun’. The pH fell from 6·5 to 4·3 in the former. Titratable acidity increased during the course of fermentation. No cyanide residue was detected in gari by fluorimetry although low cyanide levels were detected in some samples of lafun. Thin layer chromatography (TLC) of extracts from gari confirmed the absence of cyanogenetic glycosides.

Biological role of xanthine oxidase and tetrazolium-reductase inhibitor.

The biochemical properties of tetrazolium reductase inhibitor (“reductase inhibitor”) from beef brain and liver were compared with superoxide dismutase (erythrocuprein) from beef erythrocytes, using xanthine oxidase and xanthine as a model system.In all assays the behavior of erythrocuprein and the reductase inhibitor was identical; it is concluded that the tetrazolium reductase inhibitor is a member of the superoxide dismutase class of enzymes. Its possible identity with other proteins of this group remains to be established.Xanthine dehydrogenase is activated by natural or synthetic detergents. These compounds eliminate the enzymatic action of both erythrocuprein and reductase inhibitor. Low levels of cyanide, which do not inhibit xanthine dehydrogenase block superoxide dismutase.The biological role of xanthine oxidase is discussed. We propose that an important function of xanthine oxidase is to provide an ubiquitous source of hydrogen peroxide and superoxide radicals which serve as oxidants for coupled biological oxidations.