As anthropogenic black carbon, biochar can be engineered to possess high specific surface area, high pore volume, and other properties necessary for various applications. There has been much research to date on the application of biochar as a sorbent for remediating metallic and organic pollutant–impacted environments. In contrast, fewer studies have explored the use of biochar for drinking water and irrigation water purification. In this study, we used biochar as a support medium for silver nanoparticles, with the aim of producing an antimicrobial medium suitable for disinfecting irrigation water. Electron storage capacity (ESC), an important property of black carbon to mediate redox reactions, suggests a new mechanism for amending biochar for tailored applications. We recently quantified that Soil Reef biochar (SRB) possesses a considerable ESC and subsequently demonstrated that ESC is constant and fully reversible for a given pair of reductant and oxidant. Based on the reduction potentials of SRB (-0.43 to 0.80 V vs. SHE) and Ag+ (+0.80 V vs. SHE), we hypothesized that Ag+ can be reduced via the ESC and stored within biochar as elemental Ag(0). The microscopy results confirmed that silver deposited on the exterior as well as the interior of SRB, mostly as Ag(0) nanoparticles. Silver loading to the SRB was pH-dependent and can be as high as 30% at pH 8. We further evaluated the disinfection ability of nanosilver-amended SRB in batch reactors using E. coli TVS 353 as a model microorganism. With 0.1 g of nanosilver-amended SRB, six log removal of E. coli was achieved within 50 min. This study is the first application of biochar’s ESC for microbial inactivation and suggests the potential of biochar as a sorption and disinfection medium for water treatment.

Biochar as a nanosilver support medium for water disinfection

2019 Fall National Meeting

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