Mechanisms of hydroxyl radicals production from pyrite oxidation by hydrogen peroxide: Surface versus aqueous reactions

A Highly Stable Metal–Organic Framework-Engineered FeS2/C Nanocatalyst for Heterogeneous Electro-Fenton Treatment: Validation in Wastewater at Mild pH

“…In particular, the Fe(II)-S peak appeared at 720.2 eV, which is closed either to 719.8 eV 60 or 720.0 eV. 59 In the high resolution S 2p of Figure 2b, the peak for S 2p3/2 appeared at 162.9 eV, in good agreement with that reported for S2 2at 162.7 eV 29 and 162.2 eV. 60 The presence of this sulfide was confirmed in the S 2p1/2 region, since the experimental peak at 163.9 eV matched very well with the expected signal at 164.0 eV.…”

“…29 This confirms the presence of pyrite FeS2 as the only sulfide on the surface, since there was no peak at 708.9 eV that would correspond to Fe2S3. 29 FeS2 was accompanied by residual Fe2O3, displaying a peak at 711.3 eV that matched perfectly with that expected for the Fe(III)-O bond. 59 The two peaks detected in the Fe 2p3/2 region were confirmed in the Fe 2p1/2 region.…”

The principle of detailed balancing, the iron-catalyzed disproportionation of hydrogen peroxide, and the Fenton reaction

“…There are many publications that include this pair of reactions in the proposed mechanism, assigning second-order kinetics to both steps. 19,30,31,60,[69][70][71][72][73][74][75][76][77][81][82][83][86][87][88][89]91,92,94,96,[136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152][153][154] The H + in the second step is bracketed to indicate that it is required for the stoichiometry but does not appear in the rate law. This reaction pair corresponds to a reversible equilibrium, but it violates the principle of detailed balancing because the rate expressions in the forward and reverse directions are second order, which disagrees with the form of the equilibrium expression.…”

“…However, the ratio of the forward and reverse rate constants disagrees by a factor of 14 with the conditional equilibrium constant given in section 2.5. 145 Conditional kinetics is also used in several publications where the above pair of reactions are modified by replacing Fe 3+ and Fe 2+ by Fe(III) and Fe(II). In one of these Farias et al 2009 used conditional kinetics for both steps, even though the second step was shown as having H+ as a reactant.…”

Degradation of Rhodamine B in Wastewater by Iron-Loaded Attapulgite Particle Heterogeneous Fenton Catalyst

“…On the other hand, the concentration of •OH was inversely proportional to the concentration of [OH − ], and the formation of •OH was inhibited when the pH of the reaction solution was too low [51]. The conversion balance between Fe III and Fe II on the catalyst surface was destroyed, affecting the catalytic reaction [52], and the specific reaction mechanism remains to be explored. Nevertheless, the particle catalyst prepared in this study solved the problem of pH limitation of the traditional homogeneous or heterogeneous system very well [53] and still had a good decolorization effect under alkaline conditions, which was conducive to the extensive application of the heterogeneous Fenton system.…”