Insights

Challenges to silver nitrate titration in gold leaching

Aug 13, 2020 / by CyanoGuard

CyanoGuard_silver-nitrate-titration

Photo by Polina Tankilevitch from Pexels

Silver nitrate titration has been one of the most commonly used methods in measuring free cyanide in gold leaching processes. Image yourself as a mine operator, and your task is to measure how much free cyanide is in your leaching solution to control cyanide addition. Lacking alternatives, many mine operators automatically turn to silver nitrate titration as a standard approach.

The analysis involves using silver to form stable complexes with cyanide and having either potassium iodide or rhodanine as an indicator. Once all free cyanides have formed complexes with silver, the excess silver then reacts with the rhodanine indicator resulting in a colour change from yellow to salmon pink. The point in which this colour change occurs is also called the endpoint, which then allows the operator to calculate the amount of free cyanide in the sample based on the amount silver nitrate solution added to the sample before the endpoint. The determination of the endpoint is often highly debatable as it relies on the human eye. The colour sensitivity of human eye varies not only from person to person, but it also depends on the lighting conditions of the room. As such, to achieve reliable results often means making multiple manual titrations and averaging the measurement results while sieving out erroneous measurements. On average, each titration procedure takes 15-30 minutes, and that excludes time needed to clean and set up the titration apparatus and also prepare the sample.

Challenges to silver nitrate titration are not limited to the scenario described above. As such, we have developed a plug-and-play solution that can help mine operators get fast and reliable measurements for gold cyanidation. To fully understand how our solution enables users to mitigate every challenge in this process, we made a comparison table in the following:

Potential challenges

Silver nitrate titration

CyanoGuard

Time to result

4-6 hours

60 seconds

Result reliability

62%

94%

Result sensitivity

Not suitable for measurements below 10 ppm.

Our solution can measure down to 0.1 ppm.

Sample preparation

Sample preparation and filtration in the laboratory are always needed before making measurements.

No sample preparation or separate filtration step needed, filtration is done in-line while pressing the sample through the cartridge.

User bias and operator variability

Colour sensitivity of human eye varies not only from person to person, but it also depends on lighting conditions of the room.

Our device analyses the colour change and uses an AI-based algorithm to determine free cyanide. It also performs a blank measurement for every single “real” measurement, which serves as an additional way to minimize error and account for any sensor drift.

Human error

Potential sources of human errors include an incorrect reading of measurement, wrong formula and calculation and miswriting of the measurement.

We offer a fully digital process whereby all data is transmitted to our cloud platform automatically with the designated date and time of measurement, device ID and GPS location.

Interferences due to the presence of other metals and compounds

The presence of metals like copper, zinc, iron, nickel and silver can strongly distort measurements. Such interferences can also be caused by thiocyanate, carbonates or samples with pH below 12.

Presence of other metals does not interfere with results. The only potential interference is free sulfide, and this can be removed from the sample using precipitation with iron chloride before measurement.

To read more on how our solution can improve your cyanide measurement and monitoring process, download our brochure here. Or contact our sales team for a demo.

 

CyanoGuard

Written by CyanoGuard