Phosphidation of microscale zero-valent iron (P-mZVI) for enhanced dechlorination of trichloroethylene

Microscale zero-valent iron (mZVI) has a great application potential in the remediation of chlorinated organic compounds contaminated groundwater. However, the dechlorination of trichloroethylene (TCE) with mZVI often leads to the formation of toxic incomplete dechlorination products. Herein, ferrophosphorus, a byproduct of phosphorus production, has been used to modify mZVI through ball milling to get P-doped mZVI (P-mZVI). The XRD, SEM and XPS results indicated the uniform distribution of FePx species in mZVI. The phosphidation significantly promoted the dechlorination of TCE by mZVI with the degradation rate increased from 0.0073 h-1 to 0.0146 h-1. Tafel tests revealed the P-mZVI was more susceptible to water corrosion than mZVI due to primary cell effect. The cyclic voltammetry results indicated the formation of atomic hydrogen (H*) in the P-mZVI system, and H* could diffuse into the lattice of Fe0 to form H*abs. Owing to the strong reducing capability of H*, the dechlorination pathway of TCE was mainly hydrogenolysis, favoring the formation of C2H4 while almost no C2H2. The XPS results indicated that phosphorus existed as phosphate after dechlorination. Considering that phosphate is an essential nutrient for microorganism growth, the dechlorination products of P-mZVI may boost the metabolism of ingenious microbiota.

Automated summary

Phosphorus-doped microscale zero-valent iron (P-mZVI) was prepared using ball milling, which significantly enhanced the dechlorination of trichloroethylene (TCE). The degradation rate of TCE doubled with P-mZVI, and the dechlorination pathway shifted towards hydrogenolysis, producing non-toxic products such as cyclohexene and phosphate. These products can potentially stimulate the growth and metabolism of microorganisms.