New Continuous Metals Monitor Reveals Opportunities for Environmental Improvement Envirotech Online

A new technology for continuous metal monitoring was recently trialled in a river at a talc production plant in central Finland. The trial was conducted to assess the feasibility of avoiding the need to sample and analyze large numbers of environmental water samples. “The results were extremely enlightening,” explains Jari Sirviö, development engineer at Elementis, the plant’s owner. “Fortunately, a heavy rain event occurred during the short trial and we found a rapid increase and subsequent decrease in nickel concentration that closely followed the rain. This strong correlation 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 achieved with continuous monitoring.”

It is common practice worldwide to monitor metal concentrations through sampling for laboratory analysis, and the plant had previously taken samples three times a week. The continuous and automated monitor, on the other hand, takes a measurement every 5 minutes, 24/7. “Laboratory analysis would not have been able to demonstrate the correlation between rainfall and nickel concentration,” Jari explains. “We are pleased to see that this new monitoring technology can provide greater insight into the factors that influence water quality, so that we can continuously improve our environmental performance.”

The new monitoring technology uses Micro-Discharge Optical Emission Spectroscopy (μDOES®) and was supplied by the Finnish company Sensmet.

Elementis is a specialized chemical company with more than 1,300 employees at more than 24 locations around the world. The company focuses on distinctive, high-quality solutions and products to improve performance and sustainability for customers in the personal care and product performance markets. The Elementis plant in Sotkamo produces talc based on market demand, and nickel concentrate as a by-product.

Talc is one of the softest minerals and, with its sheet-like and hydrophobic properties, adds value to a range of industrial products including paper, paints and coatings, polyester putties, plastics, ceramics, food and fertilisers.

Nickel is used in a wide range of industrial applications, such as the manufacture of stainless steel. However, its importance has increased in recent years as part of rechargeable batteries, for example in electric vehicles.

Elementis continually strives to design better products that use fewer resources and cause less pollution. In addition, the company has identified water management, waste minimization and ecological impact as material issues within its sustainability strategy.

In 2021, a water treatment plant was built at the Sotkamo plant, using lime to raise the pH of the site’s wastewater and remove contaminants such as metals. In accordance with an environmental permit, together with Finnish environmental legislation, high-quality process monitoring ensures that the receiving environment is not polluted by the discharge, and includes an upper limit for nickel in the receiving river water of 0.034 mg/l.

In the period immediately after the installation of the neutralization installation, a large number of laboratory samples were taken to optimize the installation. This prompted Elementis employees to investigate the possibility of continuous analysis, which led to the trial with the µDOES® analyzer from Sensmet.

Sensmet’s Micro-Discharge Optical Emission Spectroscopy, µDOES®, enables the multi-metal real-time analysis of aqueous samples. In addition to nickel monitoring, the technology can also be used to monitor elements such as lithium, sodium, cobalt, manganese, nickel, copper and more.

The patented µDOES® technology is based on atomic emission spectroscopy. A micro-discharge (electric spark) is created directly in the aqueous sample, causing a microscopic volume of the liquid around the spark to be heated by a flash to 10,000 °C. Molecules in the microdischarge 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. The µDOES® measures this atomic emission spectrum to derive quantitative analyzes of the sample, display measurements locally, and transfer data to the DCS and user database as necessary.

The µDOES® analyzer has given Sotkamo staff new insights into the factors affecting nickel levels, allowing for the development of mitigation measures. “Sensmet’s continuous monitoring technology has provided a real light bulb moment for us,” explains Jari Sirviö. “Now that we know the correlation between rainfall and nickel concentration, we can explore a range of options that can be used to reduce nickel levels, and with continued monitoring we will be in a better position to evaluate the results.”

In recent years there has been a global trend towards greater use of continuous environmental monitoring. “This has been made possible by technological advances,” explains Sensmet CEO Dr. Toni Laurila out. “However, as this trial has shown, continuous monitoring delivers a range of other important benefits, which together further improve environmental protection.”

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