Coffee is a delicious beverage, with an ever expanding market throughout the world. Wastewaters, though also ever expanding throughout the world, are by far not so attractive or valuable… yet. Processing of coffee cherries leads to at least two solid waste materials and at least two different wastewaters, depending on the version of the process. Proper management of these wastewaters can be difficult and expensive, either due to enormous volumes or to the high concentrations more common in the modern processes. Valorization options of these wastewaters will help generate value, employment and better environmental care in coffee producing countries. Hydrothermal carbonization is one of these options. In this work, coffee wastewater hydrochars were prepared by hydrothermal carbonization of the wastewater containing the cherry mucilage. Silver nitrate in millimolar concentrations was added and tested as a catalyst and as a nanoparticle generator as well, capable of providing as the end product an hydrochar with antimicrobial properties. The hydrochars with and without silver, were characterized by particle size distribution, presence of silver nanostructures and antibacterial effects; the latter were compared to silver nanoparticles. The antimicrobial properties against Escherichia coli were assessed by the determination of the minimum inhibitory concentration (MICs) and minimum bactericidal concentrations (MBCs) methods. A good antibacterial performance was discovered, which results convenient for its use as adsorbent in water and gas purification. Though eventual specific catalytic uses are likely, they are beyond the scope of this work.

Hydrothermal carbonization of coffee wastewater as a way to obtain fine sized particles with antimicrobial properties

251st National Meeting (2016)

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