Analysis of cyanide in mining waters
Mousavi, Asra (2018)
Diplomityö
2018
School of Engineering Science, Kemiantekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
http://urn.fi/URN:NBN:fi-fe2018121450893
http://urn.fi/URN:NBN:fi-fe2018121450893
Tiivistelmä
Cyanide, as a chemical compound, can be found in the effluents of numerous industries, particularly mining. The toxicity and concentration control of cyanide during gold and silver extractions necessitate the precise detection and determination of this compound. Therefore, this topic has been the focus of finding and then comparing experimentally the different available methods for analyzing cyanide.
In the theory part, numerous cyanide compounds in mining effluents were studied. Then, different analysis methods including titration, distillation, flow injection analysis, applying the alkaline solution of picric acid, ion selective electrode, and chromatographic methods were described. In the experimental part, silver nitrate titration as the most commonly applied methods in the gold extraction industry was selected to determine free cyanide concentrations in aqueous solutions.
In the experimental part, two series of experiments were conducted. In the first series, potassium iodide in the presence of ammonium hydroxide was used as an indicator. In the second sets of experiments, p-dimethylaminobenzylidene rhodanine was applied as the indicator. In both sets of the experiments, silver nitrate solution was utilized as the titrant for the determination of free cyanide concentration in the sodium cyanide solutions.
The results showed that the optimum sample volume for the analysis is 5 ml, and p-dimethylaminobenzylidene is the most reliable indicator. In addition, in the case of using this indicator, 0.00125 mol/liter silver nitrate is the most suitable concentration of the titrant for the analysis of cyanide in solutions containing 50-100 ppm free cyanide. Furthermore, 0.000125 mol/liter silver nitrate is the most suitable concentration of the titrant in solutions containing 1-10 ppm free cyanide.
Finally, the data were applied for the determination of free cyanide concentration in a synthetic mine water. According to the results, by using silver nitrate as the titrant and p-dimethylaminobenzylidene rhodanine as the indicator, it is feasible to determine the minimum concentration of 10 ppm free cyanide in the synthetic mine water. Also, the results showed that the presence of 1000 ppm sulfate, 10 ppm nitrate, 15 ppm ammonium, and 100 ppm chloride in the mine water did not cause significant interference.
In the theory part, numerous cyanide compounds in mining effluents were studied. Then, different analysis methods including titration, distillation, flow injection analysis, applying the alkaline solution of picric acid, ion selective electrode, and chromatographic methods were described. In the experimental part, silver nitrate titration as the most commonly applied methods in the gold extraction industry was selected to determine free cyanide concentrations in aqueous solutions.
In the experimental part, two series of experiments were conducted. In the first series, potassium iodide in the presence of ammonium hydroxide was used as an indicator. In the second sets of experiments, p-dimethylaminobenzylidene rhodanine was applied as the indicator. In both sets of the experiments, silver nitrate solution was utilized as the titrant for the determination of free cyanide concentration in the sodium cyanide solutions.
The results showed that the optimum sample volume for the analysis is 5 ml, and p-dimethylaminobenzylidene is the most reliable indicator. In addition, in the case of using this indicator, 0.00125 mol/liter silver nitrate is the most suitable concentration of the titrant for the analysis of cyanide in solutions containing 50-100 ppm free cyanide. Furthermore, 0.000125 mol/liter silver nitrate is the most suitable concentration of the titrant in solutions containing 1-10 ppm free cyanide.
Finally, the data were applied for the determination of free cyanide concentration in a synthetic mine water. According to the results, by using silver nitrate as the titrant and p-dimethylaminobenzylidene rhodanine as the indicator, it is feasible to determine the minimum concentration of 10 ppm free cyanide in the synthetic mine water. Also, the results showed that the presence of 1000 ppm sulfate, 10 ppm nitrate, 15 ppm ammonium, and 100 ppm chloride in the mine water did not cause significant interference.