Engineered and natural nanoparticles are ubiquitous in the earth environments. Adsorption of nanoparticles on minerals has fundamental implications to many environmental and geochemical processes. We studied the adsorption of negatively and positively charged gold nanoparticles (AuNPs) on natural, synthetic and As-bearing pyrite samples. Almost no adsorption of negatively charged AuNPs was found on pure pyrite due to high electrostatic repulsion between AuNPs and pyrite. In contrast, positively charged AuNPs could be easily adsorbed on pyrite surface because of electrostatic attraction. The oxidation of pyrite surface enhanced the adsorption of negatively charged AuNPs, since the oxidized pyrite surface became positively charged. The incorporation of As into pyrite structure facilitated the adsorption of negatively charged AuNPs, which is likely due to the formation of charge-assisted hydrogen bonds between As-bearing pyrite and AuNPs.

Adsorption of gold nanoparticles on pyrite surfaces

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