Efficient removal of chloroform in groundwater by polyethylene glycol-stabilized Fe/Ni nanoparticles

Chloroform is an harmful chlorinated hydrocarbon which is hardly degraded using actual dechlorination methods. Alternatively, carboxymethyl cellulose/zero-valent iron appears promising to degrade chlorinated hydrocarbons in water, yet actually carboxymethyl cellulose cannot inhibit the oxidation and sedimentation of iron ions under alkaline condition. Here, polyethylene glycol, a green and low-cost non-ionic polymer, was used as a stabilizer to synthesize polyethylene glycol-stabilized Fe/Ni nanoparticles (PEG-Fe/Ni) for removing chloroform from water in a wide range of pH, from 3 to 11. PEG-Fe/Ni was prepared by a stepwise liquid-phase chemical reduction, then added into groundwater to remove chloroform. Results show that polyethylene glycol can both reduce the particle size from 106.9 to 79.6 nm and prevent the oxidation and sedimentation of iron ions under alkaline condition. The removal efficiency of chloroform increased from 86.3 to 100% at pH 6 in the presence of polyethylene glycol, and slightly decreased to 95.4% at pH 11. The calculated rate constant (k) indicates that chloroform removal follows pseudo-first-order kinetics. Furthermore, the PEG-Fe/Ni also removed chloroform from real groundwater at pH 8 with an efficiency of 90.1% in 4 h, which is higher than that for Fe/Ni nanoparticles, of 41.7%.