Ling Tana, Thomas Ray Jonesb, Jordan Poitrasb, Jianping Xiea, Xinxing Liua, Gordon Southamb
Palladium nanoparticles (PdNPs) can catalyse a range of reductive chemical reactions transforming both organic and inorganic environmental pollutants. PdNPs that ranged from < 2 to 2–40 nm were synthesized using chemical methods, and bacterial biomass with/without chemical ﬁxatives. PdNP formation was enhanced by adsorption of Pd(II) to bacterial biomass, followed by ﬁxation with formate or glutaraldehyde. TEM-SAED analyses conﬁrmed that the cell associated PdNPs were polycrystalline with a face-centered cubic structure. Chemically formed PdNPs possessed a higher Pd(0):Pd(II) ratio and produced structurally similar nanoparticles as the biotic systems. These PdNPs were employed to catalyze two, reductive chemical reactions, transforming 4-nitrophenol (4-NP) and hexavalent chromium [Cr(VI)], into 4-aminophenol and Cr(IV), respectively. In the reduction of 4NP, the catalytic performance was directly proportional to PdNP surface area, i.e., the smallest PdNPs in formatePdCH34 cells had the fastest rate of reaction. The mass of Pd(0) as PdNPs was the main contributor to Cr(VI) reduction; the chemically synthesized PdNPs showed the highest removal eﬃciency with 96% at 20 min. The use of glutaraldehyde enhanced the reduction of Pd(II) and promoted PdNPs formation, i.e., creating an artefact of ﬁxation; however, this treatment also enhanced the catalytic performance of these PdNPs.