Exogenous ferrous ion dosing allows depassivation of aged zerovalent iron (ZVI) for industrial wastewater treatment, while sustaining the persistent existence of Fe(II) species for continuous depassivation throughout decontamination remains challenging. To tackle this dilemma, pre-oxidized microscale ZVI (poZVI bm ) is proposed via ball milling with peroxydisulfate (PDS) solids, for tailoring an “continuous self-driven depassivation” scenario with Fe 0 /Fe(II) symbiosis. The poZVI bm exhibits a 4.4 ∼ 19.0 times higher equilibrated adsorption capacity for hexavalent chromium (Cr(VI)) than the referenced ball milled ZVI (ZVI bm ) and other benchmarked mZVI composites (e.g. oxalated ZVI bm , sulfidized ZVI bm , and nanoscale ZVI), following a chemisorption-reduction process. It also demonstrates a 4.5 ∼ 18.7 folds faster surface area-normalized removal rate for nitrobenzene (NB) than all these counterparts, mediated by reductive transformation. Cr(VI) removal and NB reduction depend on the dissolved and surface-sorbed Fe(II), respectively, which can be optimized by regulating pre-oxidation degree of poZVI bm . The “continuous self-driven depassivation” of poZVI bm starts with the local microenvironment acidification due to the adsorption of abundant dissolvable Fe(II) over surface-located Fe(III), which drives continuous dissolution of Fe 0 core to create more reactive Fe(II), and therefore repeats the above procedure. Owing to wide pH adaptability (pH 3 ∼ 9) and impressive corrosion behavior of poZVI bm , these findings inspire the intimate integration of Fe 0 /Fe(II) component for high-efficient remediation of multicomponent industrial wastewater.
Kai Yu,Xiuqiong Yang,Mao Wan,Haowen Jiang,Penghui Shao,Liming Yang,Hui Shi,Xubiao Luo
This study, for the first time, evaluates a novel method for the desorption of contaminants from soil that uses the heat generated by zero-valent iron (ZVI) under low-frequency electromagnetic fields (EMF), and elucidates the specific effects of soil pH upon the process. It was found that the temperature of soil mixed with ZVI could reach up to ∼60 °C within 20 min under the applied EMF, and after 60 min the residual fraction of m-xylene in soil decreased by 86.4% compared to no-ZVI soil. The most efficient desorption of m-xylene occurred at a soil of pH 5. Desorption was related to the net heating capacity of the ZVI particles, which was defined by pH-dependent formation of surface corrosion products. The preservation of metal iron and formation of Fe(II) species was favored for heat generation. Soil pH also affected m-xylene retention and the local thermal conduction from ZVI to m-xylene by regulating the surface properties of fulvic acid and ZVI. This study provides valuable information regarding the impact of pH on the thermal desorption of soil contaminants by ZVI coupled with EMF and illustrates the potential of the method in the remediation of contaminated sites.
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