Foamed-Fe0 via phase interface polishing by ultrasound to activate persulfate for treating triphenylmethane derivative

The novel process via the foamed zero-valent-iron (Fe0f) activating persulfate (PS) in ultrasound (US) system for the first time was employed to treat tpmFG (a triphenylmethane derivative) as the a model compound of oxidative products of hair colorants which can pose potential threats to human and ecosystem health. The novel mathematical models involving the degradation momentum (ε) and the apparent ratio of integral concentration movement (rapp) were applied to describe the degradation process. The effects of different factors and the optimization by response surface methodology (RSM) for tpmFG removal were evaluated based on the above models. The anions, cations (except Cu2+), and organic matter (e.g. humic acid (HA), or excess ethylene diamine tetraacetic acid (EDTA)) had the inhibiting effect on removing tpmFG. The possible tpmFG decomposition pathway (hydroxylation, carbonylation demethylation deamination, and ring-open) was proposed by using GC/MS and HPLC-MS. Comparing with Fe0f-PS system, the results of XRD, SEM, and contact angle confirmed that US made the corrosive surface of Fe0f suffer polishing to expose more fresh Fe0 source, which was also verified by the simulation via the acoustic-piezoelectric interaction by the numerical simulation. By economic comparison with other US-based processes, the US/Fe0f-PS system with EE/O 12.4 kW h m−3 and total cost value 2.28$ m−3 showed good performance of cost saving. The degradation mechanism with US polishing to promote Fe0/FeII/FeIII circle converting for PS activation was proposed.