Patented process gives sludge a second chance

Researchers at the Illinois Institute of Technology have developed and patented a process by which sludge from municipal waste water or paper mills can be turned into activated carbon, an ingredient used by manufacturing plants to remove toxic chemicals such as NOX (oxides of nitrogen) from their emissions.

'Activated carbon is used by virtually every manufacturing plant to remove NOX in order to comply with the 1990 Clean Air Act Amendment,' said Nasrin Khalili, assistant professor of chemical & environmental engineering. 'We have come up with a way to turn toxic paper mill sludge into something manufacturers (including paper mills) need.'

Sludge from manufacturing plants needs to be specially treated and dried before it can be deposited into landfills, which is an expensive process.

Khalili turns the sludge into activated carbon - a catalyst that can help remove toxic by-products of combustion, from smokestack emissions.

Currently, activated carbon is pressed into a wafer-like filter that is fitted into the smokestack. As emissions pass through the filter on their way out, NOX is removed.

'But the process isn't very efficient. The NOX isn't in contact with the activated carbon for very long as it passes through the filter,' said Khalili. 'I am working on developing a method where the activated carbon is introduced into the smokestack as an aerosol. That way, the emissions will interact with the activated carbon during their entire trip through the smokestack instead of just at one point.'

Khalili is said to have tested her activated carbon against a commercially produced equivalent and found that her product works better with a NOX removal capability of 66 percent to 94 percent.

Khalili is currently working on combining IIT Carbon with bacteria that metabolises NOX to produce a biocatalytic activated carbon.