High chloroform removal using tannic acid to promote the activation of persulfate with Fe/Ni nanoparticles

Chloroform is a toxic and persistent solvent that cannot be effectively removed from the environment by actual remediation methods. Chloroform removal using persulfate activated by iron nanoparticles has been tested but is limited by chloroform inertness and nanoparticle inactivation in the real environment. Here we hypothesized that tannic acid could improve the activation of persulfate with Fe/Ni nanoparticles. We studied the influence of tannic acid/Fe ratio, persulfate concentration, initial pH, temperature, inorganic anions and natural organic matters on chloroform removal. We found that tannic acid-Fe/Ni-persulfate system with 1.65 mol% of tannic acid-Fe and 3.2 mM of persulfate yielded about 87–97% chloroform removal in the 2.9–10.7 pH range. Electron paramagnetic resonance and radical quenching experiments revealed that SO4•− and •OH were primarily responsible for chloroform removal. High removal is probably due to Fe-tannic acid chelation that prevents the precipitation of iron hydroxide on Fe/Ni nanoparticles, thus preserving active sites.