Metal Borides as Excellent Co-Catalysts for Boosted and Long-Lasting Fenton-like Reaction: Dual Co-Catalytic Centers of Metal and Boron

Abstract

The continuous electron supply for oxidant decomposition-induced reactive oxygen species (ROS) generation is the main contributor for the long-standing micropollutant oxidation in the iron-based advanced oxidation processes (AOPs). Herein, as a new class of co-catalysts, metal borides with dual active sites and preeminent conductive performance can effectively overcome the inherent drawback of Fenton-like reactions by steadily donating electrons to inactive Fe­(III). Among the metal borides, tungsten boride (WB) exhibits a significant co-catalytic performance run ahead of common heterogeneous co-catalysts and exceptionally high stability. Based on qualitative and semi-quantitative tests, the hydroxyl radical, sulfate radical, and iron­(IV)-oxo complex are all produced in the WB/Fe­(III)/PDS system and Fe­(IV)-induced methyl phenyl sulfoxide decomposition is up to 72%. Moreover, the production efficiency of ROS and relative proportions of radical and nonradical pathways change with various experimental conditions (dosages of PDS, WB, and solution pH) and water matrices. The rate-determining step of Fe­(II) regeneration is greatly accelerated resulting from the synergetic effect between exposed metallic reactive sites and nonmetallic boron with reductive properties of WB. In addition, the self-dissolution of surface tungsten oxide and boron oxide leads to a renovated surface for sustainable Fe­(III) reduction in long-term operations. Our discovery provides an efficient and sustainable strategy in the field of enhanced AOPs for water remediation.

Were Persulfate-Based Advanced Oxidation Processes Really Understood? Basic Concepts, Cognitive Biases, and Experimental Details

“…The other five or two kinds of hydroxylated isomers induced by COU or BA had almost no fluorescence. Especially when using COU or TA in SO 4 •– -involved systems, researchers − might conclude that the generation of hydroxylation products was only indicative of HO • presence, but SO 4 •– contribution should be considered as well. BA might also be oxidized into decarboxylation products (phenol, catechol, and hydroquinone (HQ)) and/or aromatic organosulfur compounds besides hydroxylation products by SO 4 •– , which might be distinguished from that by HO • .…”

“…Reactive high-valent metal-oxo complexes (RHVMOC, e.g., Fe­(IV) ,,− (usually represent Fe IV O 2+ in Fe 2+ or Fe 3+ systems, and Fe IV O 4 4– or Fe IV O 3 2– in ferrate systems), Fe­(IV)-ligand, , Fe­(V), , Co­(IV), ,, Ni­(IV)-ligand, Cu­(III), , Cu­(III)-ligand, or Mn­(V)-ligand, , in solution; Fe IV O, Fe V O, − Co IV O, ,, Ni &+ O, Ni IV O, Cu III -oxo, ,,, Mn IV -oxo, or Mn V -oxo, on catalysts surface) are also very significant and usually overlooked nonradicals in PS-AOPs (Figure c).…”

“… Later, Dong et al concluded that both Fe­(IV) and SO 4 •– were formed at pH = 3.0–6.5 in the Fe 2+ /PDS system or Fe 2+ /PMS system . Fe­(IV) in solution might be stemmed from (i) Fe 2+ systems, (ii) Fe 3+ and metal boride systems, (iii) Fe 3+ and ligand systems, , or (iv) ferrate systems . In the ferrate systems, Fe­(V) (Fe V O 4 3– ) might also be generated in solution, and possessed relatively higher reactivity than Fe­(IV) .…”

Enhanced Fe(ii)/Fe(iii) cycle by boron enabled efficient Cr(vi) removal with microscale zero-valent iron

“…21,22 Moreover, many boron-containing compounds were also developed to improve the efficiency of the iron cycle. 23–29…”

New Insights into Photo-Fenton Chemistry: The Overlooked Role of Excited IronIII Species

“…In recent decades, as one of the most importantly reversible Fe III /Fe II redox processes, the iron-mediated Fenton technique has rapidly advanced in both basic research and scale-up applications for water decontamination (Table S1). However, the issue of sluggish dynamics of Fe II generation still limits the practical applications of Fenton technique (eqs and , Text S1 and Figure S1). − F e ( I I ) + H 2 O 2 → F e ( I I I ) + • O H + normalO normalH − goodbreak0em3em⁣ k = 80 .25em normalM − 1 .25em s − 1 F e ( I I I ) + H 2 O 2 → F e ( I I ) + normalH normalO 2 • + H + goodbreak0em1em⁣ k = 9.1 × 10 …”