The excessive usage and emissions of triclosan (TCS) pose a serious threat to aquatic environments. Iron-based bimetallic particles (Pd/Fe, Ni/Fe, and Cu/Fe, etc.) were widely used for the degradation of chlorophenol pollutants. This study proposed a novel synthesis method for the preparation of Ni/Fe bimetallic particles (Ni-Fe bm ) by ball milling microscale zero valent iron ZVI (mZVI) and NiSO 4 . Ball-milling conditions such as ball-milling time, ball-milling speed and ball-to-powder ratio were optimized to prepare high activity Ni-Fe bm bimetallic particles. During the ball-milling process, Ni 2+ was reduced to Ni 0 and formed a coupled structure with ZVI. The amount of Ni 0 on ZVI significantly affected the activity of Ni-Fe bm bimetallic particles. The highest activity Ni-Fe bm bimetallic particles with Ni/Fe ratio of 0.03 were synthesized under optimized conditions, which could remove 86.56% of TCS (10 μM) in aerobic aqueous solution within 60 min. In addition, higher particle dosage, lower pH condition and higher reaction temperature were more conducive for TCS degradation. The higher corrosion current and lower electron transfer impedance of Ni-Fe bm bimetallic particles were the main reasons for its high activity. The hydrogen atom (•H) on the surface of Ni-Fe bm bimetallic particles was mainly contributed to the removal of TCS, as reductive transformation products of TCS were detected by LC-TOF-MS. Notably, a small amount of oxidation products were discovered. The total dechlorination rate of TCS was calculated to be 39.67%. After eight reaction cycles, the residual Ni-Fe bm bimetallic particles could still degrade 28.34% of TCS within 6 h. Low Ni 2+ leaching during reaction indicated that Ni-Fe bm bimetallic particles did not pose potential environmental risks. The prepared environmental-friendly Ni-Fe bm bimetallic particles with high activity have great potential in the degradation of other chlorinated organic compounds in wastewater.
Multiple reactive intermediates have been proposed to be involved in peroxydisulfate (PDS) activation by zerovalent iron (ZVI), including sulfate radical (SO 4 ·− ) produced via iron-oxide shell mediated electron transfer, ferryl ion species (Fe(IV)) formed from Fe(II)-PDS interaction, and hydroxyl radical ( · OH) generated by ZVI aerobic oxygenation. In this study, evolution of the relative role of these intermediates in microscale and nanoscale ZVI (mZVI vs. nZVI) activated PDS processes is comparatively investigated by using a methyl phenyl sulfoxide (PMSO) probe that selectively reacts with Fe(IV) to produce methyl phenyl sulfone (PMSO 2 ). Interestingly, during PMSO transformation by mZVI/PDS process, yields of PMSO 2 (η(PMSO 2 )) exhibit three-stage behavior that they first increase to a maximum (∼80% but lower than 100%) (Stage I) and then plateau for a period (Stage II) followed by a decrease phase (Stage III). Accordingly, the relative role of Fe(IV) in PMSO transformation is unceasingly improved in Stage I and subsequently reaches equilibrium with that of free radicals in Stage II, while it finally decreases in Stage III. Similar η(PMSO 2 ) evolution trends are obtained in nZVI/PDS process, except that the η(PMSO 2 ) increase in Stage I is negligible, possibly due to the exceptional fast nZVI dissolution. It was further clarified by tert -butyl alcohol scavenging assay that, in addition to Fe(IV), the free radical involved in Stages I and II is SO 4 ·− , while · OH was dominant in Stage III. Moreover, studies on O 2 effect reveal that ZVI aerobic oxygenation participates in mZVI corrosion during the entire process, while it is only involved in nZVI corrosion when PDS content is reduced to a low concentration, indicating that the reactivities of PDS and O 2 are similar in mZVI corrosion, but differ greatly in nZVI corrosion. Additionally, effects of reactant dose and pH on η(PMSO 2 ) evolution are also explored. Dynamics of the relative role of different reactive oxidants should be taken into account in further applications of ZVI/PDS in situ chemical remediation technology considering their different chemistries.
危险品化学品经营许可证（带存储）