About half the corn harvest — stalks, leaves, husks, and cobs — remains as waste after the kernels have been stripped from the cobs. These leftovers, known as corn stover, have few commercial or industrial uses aside from burning. Researchers developed an energy-efficient way to put corn stover back into the economy by transforming it into activated carbon for use in water treatment.
Activated carbon, also called activated charcoal, is charred biological material that has been treated to create millions of microscopic pores that increase how much the material can absorb. It has many industrial uses, the most common of which is for filtering pollutants out of drinking water.
The researchers compared methods for producing activated carbon from charred corn stover and found that processing the biomass with hot compressed water — a process known as hydrothermal carbonization — produced activated carbon that absorbed 98 percent of the water pollutant vanillin.
Hydrothermal carbonization created a biochar with higher surface area and larger pores when compared to slow pyrolysis — a process where corn stover is charred at increasing temperatures over a long period of time. When the researchers filtered water into which vanillin had been added through the activated carbon, its combination of larger surface area and bigger pores enabled the carbon to absorb more vanillin.
Finding applications for resources such as corn stover could help combat climate change.