Regulation of tourmaline-mediated Fenton-like system by biochar: Free radical pathway to non-free radical pathway

In-situ structural modification on spinel oxide to achieve efficient removal of refractory organics: Triple optimisation of degradation performance

Spinel oxide has attracted interest in wastewater treatment, owing to its visible light (VIS) adsorption properties and bimetallic synergism. However, owing to the inefficient separation of photogenerated carriers and poor redox property, there is an urgent need to develop appropriate modification strategies to address these bottlenecks. This study aimed to develop CuFe2O4/CuFeSx (CFO/CFSx) heterojunction with oxygen vacancies (OVs) via an in-situ structural modification to trigger the generation of more radicals with low oxidant consumption for the efficient degradation of refractory organics. This customized heterojunction improved the light-trapping ability and photoelectrons utilisation, promoting the reduction of metal valence by photoelectrons to enhance the activation of peroxymonosulfate (PMS). Meanwhile, OVs also provided more active sites to activate PMS to generate superoxide radicals (O2-), which were further converted to hydroxyl radicals (OH) to ensure considerable oxidation capability. Notably, Sulfur-mediated metal valence reduction boosted the cycle of Cu(I)/Cu(II) and Fe(II)/Fe(III), guaranteeing the regeneration of the active sites. Triple optimisation of the modified spinel oxide presented a striking oxidant utilisation efficiency with a substantial increase in the concentration of radicals. This study provides a simple and reliable reference for designing high-performance CuFe2O4 (CFO) photocatalysts for environmental remediation.

A Critical Review on the Biochar-mediated Formation of Reactive Species: Detection Methods, Transformation Mechanisms and Environmental Implications

In recent years, studies on the degradation of environmental contaminants by sulfate radicals (SO4•-) and hydroxyl radicals (•OH) based advanced oxidation processes (AOPs) have garnered increasing attention. Notably, biochar, which can activate chemical oxidants to produce reactive species, has been increasingly employed to enhance the removal of the contaminants in AOPs. Nevertheless, a systematic understanding of the biochar-mediated reactive species is still lacking in contaminants remediation during environmental applications. This review outlines the identification and determination methods of reactive species induced by biochar, the underlying reaction mechanisms, and their contaminant removal efficacy in AOPs systems. Multiple factors, such as the characteristics of biochar/chemical oxidants, the nature of the target contaminants, and some soil active constituents can affect the generation, diffusion, and transformation of a wide range of reactive species. This review systematically compares two reaction pathways, free radical mechanisms and non-free radical mechanisms. Environmental applications are emerging from the controlled generation of reactive species through biochar-mediated processes, as comprehensively discussed.

Activity and recyclability enhancement of pH-dependent Fe0@BC-mediated heterogeneous sodium percarbonate (SPC)-reducing agents (RA) system

Dyes pose great threats to the aquatic environment and human health. Fe0-based Fenton-like systems have been widely employed for the degradation of organic dyes. However, the regulation of degradability and recyclability was still unclear. In this study, Rhodamine B (RhB) was served as the model pollutant, hydroxylamine hydrochloride was selected as the RA, the natural photocatalysis system demonstrated stable operation. RA, as performance enhancement agent, was firstly reported in micro/nano-Zero-Valent Iron@Biochar (m/nZVI@BC) based SPC-RA system. Carrier size-fractionated m/nZVI@BC was fabricated by one-step carbothermal method. As a result, RA synergistically interacted with SPC, and the reaction time reduced from 15 min to 4 min. In the 0.010 g m/nZVI@BC-mediated SPC-RA system, over 95% of RhB (100 mg·L-1, 1041.667 mg·g-1) was successfully degraded. The maximum degradation ability could still exceed 1g·g-1 via 5 times repeated applications. Meanwhile, the loss of degradability, caused by halving SPC concentration could be compensated by RA dosage measurement. The entire degradation process was predominantly dominated by free radicals (•OH> 1O2> •O2-> •CO3-). Reactive oxidizing species (ROSs) were primarily excited by α-Fe0, Fe3C and N sites of biochar (BC). Light and BC carrier dedicated slight influence. These discoveries shed a light on the activity and recyclability regulation of catalytic material, aligning with the principles of green chemistry and cleaner production. This study demonstrates a novel approach to efficient management of solid waste disposal, reuse of waste biomass, advanced treatment of dye-containing wastewater, pollution control in aquatic environments.