Simultaneous Nitrite Resourcing and Mercury Ion Removal Using MXene-Anchored Goethite Heterogeneous Fenton Composite

Abstract

The integrated system of gas-phase advanced oxidation process combined with sulfite-based wet absorption process is a desirable method for simultaneous removal of SO2, NO, and Hg0, but due to the enrichment of nitrite and Hg2+, resourcing harmless wastewater is still a challenge. To tackle this problem, this study fabricated a bifunctional β-FeOOH@MXene heterogeneous Fenton material, of which the crystalline phase, morphology, structure, and composition were revealed by using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy–energy dispersive x-ray spectroscopy, and transmission electron microscopy. It exhibits excellent performance on nitrite oxidation (99.5%) and Hg2+ removal (99.7%) and can maintain stable outstanding ability after 13 cycles, with superior Hg2+ adsorption capacity (395 mg/g) and ultralow Fe leaching loss (<0.018 wt %). The synergism between MXene and β-FeOOH appears as follows: (i) MXene, as an inductive agent, directionally converted Fe2O3 into β-FeOOH in the hydrothermal method and greatly reduced its monomer size; (ii) the introduced Ti­(III)/Ti­(II) accelerated the regeneration of Fe­(II) via rapid electron transfer, thereby improving the heterogeneous Fenton reaction; and (iii) MXene strongly immobilized β-FeOOH to greatly inhibit Fe-leaching. HO•, •O2 ––, and 1O2 were the main radicals identified by electron spin resonance. Radical quenching tests showed their contributions to NO2 – oxidation in the descending order HO• > 1O2 > •O2 –. Quantum chemical calculations revealed that •OH-induced oxidation of NO2 – or HNO2 was the primary reaction path. Density functional theory calculations combined with X-ray photoelectron spectroscopy and Raman characterizations displayed the Hg2+ removal mechanism, with Hg2Cl2, HgCl2, and HgO as the main byproducts. This novel material provides a new strategy for resourcing harmless wastewater containing nitrite and Hg2+.

Electrosorption, Desorption, and Oxidation of Perfluoroalkyl Carboxylic Acids (PFCAs) via MXene-Based Electrocatalytic Membranes

“…Moreover, MXenes with −Cl, −Br, −I, −BrI, and −ClBrI terminations exhibited different affinities toward intercalated cations . In environmental applications, MXenes and MXene-based materials have been used as adsorbents − and antibacterial agents , to remove water pollutants and pathogens. MXenes garner strong covalent and electrostatic interactions with many pollutants due to their rich surface functionalities and charged surface.…”

Flow-through heterogeneous electro-Fenton based on Co-CNT/Ti3C2TX membrane for improved tetracycline removal in wide pH ranges

“…The layered structure contains rich functional groups and is easy to adsorb, which provides a better and more effective auxiliary means for wastewater treatment. 44 Some researchers used the characteristics of electrode materials to combine the adsorption process with EF technology, which solved the problem of effectively removing acetamiprid from wastewater. 45 Therefore, the preparation of thin and porous conductive membrane electrodes is very important for the universality and efficiency of wastewater treatment.…”