Iron based bimetallic nanoparticles to activate peroxygens

• Bimetallic systems are more effective than a monometallic system.
• A lower degradation rate was observed for H2O2 compared to HSO5- or S2O82-.
• A metal bridged complex is likely formed in the activated H2O2 system.
• Peroxygen dose or mass of bimetallic zero valent nanoparticles present are key.

Recently, metal nanoparticles have been used to generate highly reactive free radicals from peroxygens to treat hazardous organic compounds. A novel method of treating trichloroethylene (TCE) was applied using bimetallic zero valent nanoparticles (BZVNs) and peroxygens. In the investigation of nine different BZVNs as activators, the highest TCE oxidation was achieved by nano-Pd–Fe0 and nano-Zn–Fe0 in the activated persulfate system, nano-Co–Fe0 in the activated peroxymonosulfate system, and nano-Ag–Fe0 in the activated hydrogen peroxide system. In all three systems, increasing the dosage of metal nanoparticles and peroxygens increased the oxidation of TCE. We also found that BZVNs are promising activators for hydrogen peroxide, persulfate, and peroxymonosulfate compared to monometallic zero valent nanoparticles. For example, the TCE reaction rate constant by nano-Ag–Fe0 activated H2O2 is 9- to 18-fold higher than that for nano-Fe0 activated H2O2. The activated H2O2 system showed a much lower TCE oxidation rate compared to either activated persulfate or activated peroxymonosulfate, suggesting that a bridged group complex is formed between the activators and H2O2, causing a lower TCE oxidation rate.