Biochar — a charcoal-like substance made primarily from agricultural waste products — holds promise for removing emerging contaminants such as pharmaceuticals from treated wastewater.
That’s the conclusion of a team of researchers that conducted a novel study that evaluated and compared the ability of biochar derived from two common leftover agricultural materials — cotton gin waste and guayule bagasse — to adsorb three common pharmaceutical compounds from an aqueous solution. In adsorption, one material, like a pharmaceutical compound, sticks to the surface of another, like the solid biochar particle. Conversely, in absorption, one material is taken internally into another; for example, a sponge absorbs water.
Guayule, a shrub that grows in the arid Southwest, provided the waste for one of the biochars tested in the research. More properly called Parthenium argentatum, it has been cultivated as a source of rubber and latex. The plant is chopped to the ground and its branches mashed up to extract the latex. The dry, pulpy, fibrous residue that remains after stalks are crushed to extract the latex is called bagasse.
The research was innovative because it was the first to use cotton gin waste and guayule bagasse to produce biochar for the removal of emerging pharmaceuticals from water. Image: Penn State
The results are important, according to researcher Herschel Elliott, Penn State professor of agricultural and biological engineering, College of Agricultural Sciences, because they demonstrate the potential for biochar made from plentiful agricultural wastes — that otherwise must be disposed of — to serve as a low-cost additional treatment for reducing contaminants in treated wastewater used for irrigation.
“Most sewage treatment plants are currently not equipped to remove emerging contaminants such as pharmaceuticals, and if those toxic compounds can be removed by biochars, then wastewater can be recycled in irrigation systems,” he said. “That beneficial reuse is critical in regions such as the U.S. Southwest, where a lack of water hinders crop production.”
The pharmaceutical compounds used in the study to test whether the biochars would adsorb them from aqueous solution were: sulfapyridine, an antibacterial medication no longer prescribed for treatment of infections in humans but commonly used in veterinary medicine; docusate, widely used in medicines as a laxative and stool softener; and erythromycin, an antibiotic used to treat infections and acne.