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Acid test: a novel method for recycling hazardous waste

EU support enables an innovative approach to recycling that returns cleaned acid in galvanisation factories, extracting valuable metals from it in the process.

Industrial Technologies

Galvanising iron and steel is a crucial step in protecting infrastructure from corrosion, moss, oil and even chewing gum. But adding this protective coating of zinc generates 1.8 billion litres of acidic waste every year in the EU. The ReCreo project aims to completely recycle this waste stream, generating useful metals in the process. Hot-dip galvanisation is a process in which iron or steel is immersed in molten zinc, causing a corrosion-resistant patina to form. At various stages, the metal being treated is dipped in hydrochloric acid to remove impurities and rust.

Waste acid

“In time, this acid becomes too saturated with dissolved iron and loses its effect,” explains Rami Niinikoski, ReCreo project officer. “When it reaches that stage, you have to take it to a hazardous waste treatment company, who will neutralise the acid and dispose of the sludge waste in landfill.” This results in the loss of both the dissolved metals and the acid, he says, as well as contributing to Europe’s waste problem. The ReCreo project explores a method to clean the acid, extracting valuable metal compounds in the process. “Our solution is regeneration by distillation; in the process the acid is purified, and we remove diluted metals in salt form, such as iron sulfate and zinc sulfate,” says Niinikoski. “The idea is to return the clean hydrochloric acid to the customer. That service is more valuable than the metals, although sulfates can be used in many industries, such as wastewater cleaning.”

High capacity

Currently, there exists no competing solution for treating the acidic wastes generated by galvanisation and circuit board manufacturing. Project host ChemBrot estimates the market for their process in Europe at EUR 250 million. A pilot plant built in Järvenpää, Finland can distil 2 million litres of waste annually, enough to serve all 14 of the country’s hot-dip galvanisation factories. “It’s a very effective way to reduce this waste,” adds Niinikoski. “We can treat all their waste and still have a little excess capacity.” If all goes well, ChemBrot hopes to divert 14 800 tonnes of metal and 74 million tonnes of hazardous waste from landfills by 2029 and draw over EUR 50 million in revenue in the process. The project was supported by the EU’s Horizon 2020 programme. “It was really good for us,” notes Niinikoski. “Our goal is to expand from Finland and for that you need investment; through this funding we found some potential partners.”

Agricultural application

This interest includes a fertiliser manufacturer that is hoping to add the iron and copper sulfates captured by ChemBrot to their products, and a galvanising factory that wishes to recycle their hydrochloric acid. Niinikoski has worked in the waste management industry for the past 15 years. “Back then it wasn’t such a hot topic as it is today, it was just trucks that came to take your things,” he explains. “Today the whole environmental industry and circular economy has become a really interesting area. Things are changing all the time and there are a lot of possibilities.”

Keywords

ReCreo, ChemBrot, hot-dip galvanisation, steel, iron, acid, waste, zinc, sulfates

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