Sensmet says its transportable µDOES analyser can provide real-time, simultaneous quantification of dissolved metal concentrations such as nickel, cobalt, lithium, manganese and copper in hydrometallurgical processes and mining waters. Its cloud solution allows users to follow measurement results and trends in real-time using any device of choice. (Photo: Sensmet)
A new continuous metals monitoring technology was recently used by a Finnish talc producer to evaluate the potential for avoiding a need to analyze large numbers of process-plant discharge water samples from a nearby water source.
The Elementis-owned plant at Sotkamo in central Finland produces talc as well as nickel concentrate as a by-product. A water treatment plant was built at Sotkamo in 2021 to raise the pH of site wastewater and remove contaminants such as metals. The plant conducts regular sample monitoring of its wastewater discharge into a nearby river to ensure compliance with regulatory and environmental policies.
During the period immediately after installation of the treatment plant, a large number of laboratory samples were taken as plant performance was optimized. This prompted Elementis staff to investigate the possibility of continuous analysis. Previously, the company had taken samples three times per week. In contrast, the recently tested continuous and automated monitor took measurements every five minutes, around the clock. The new monitoring technology employs Micro-Discharge Optical Emission Spectroscopy (µDOES), and was supplied by the Finnish company Sensmet.
“The results were extremely enlightening,” explained Jari Sirviö, development engineer for Elementis. “A heavy rainfall event occurred during the brief trial, and we discovered a rapid increase, and subsequent decrease, in nickel concentration that closely followed the rain. This strong collect between rainfall and nickel provides an important insight into the behavior of nickel, and raises a number of important questions. It also highlights the enormous benefits that can be gained from continuous monitoring.”
Sensmet’s µDOES technology enables the multi-metal real-time analysis of aqueous samples. In addition to nickel monitoring, the technology can also be used to monitor for lithium, sodium, cobalt, manganese, nickel, copper and more.
The patented technology is based on atomic emission spectroscopy. A micro-discharge, or electric spark, is created directly inside the aqueous sample, causing a microscopic volume of the fluid surrounding the spark to be flash-heated to 10,000°C. Molecules in the micro-discharge are dissociated into atoms, which are excited to their respective higher electronic states. Upon returning to their ground state, these atoms release their excess energy by emitting light at their characteristic wavelengths. µDOES measures this atomic emission spectrum to derive quantitative analysis of
the sample, displaying measurements locally and transferring data to the user’s DCS and database as needed.
According to Sensmet, the µDOES analyzer has provided the Sotkamo staff with new insights into the factors affecting nickel levels, which enables the development of mitigation measures. “Sensmet’s continuous monitoring technology has delivered a real lightbulb moment for us,” according to Jari Sirviö. “Now that we know about the correlation between rainfall and nickel concentration, we can investigate a range of options that could be employed to lower nickel levels, and with continuous monitoring we will be in a better position to evaluate the results.”
