Removal of tridecane dicarboxylic acid in water by nanoscale Fe0/Cu0 bimetallic composites

Efficient activation of persulfate by copper-coated nano zero-valent iron for degradation of nitrogenous disinfection by-products: The key role of Cu

The essential shortcoming of rapid passivation deactivation limits the efficient application of nano zero-valent iron (nZVI) in eliminating disinfection byproducts from drinking water. Copper-coated nano zero-valent iron (Cu-nZVI) bimetallic composites were synthesized to efficiently activate persulfate (PS) to remove nitrosopyrrolidine (NPYR). By introducing Cu-coated coatings, nZVI is protected from direct contact with PS; thus, Cu-nZVI appears to activate PS efficiently and stably without rapid deactivation. Compared with plain nZVI, the constructed Cu-nZVI/PS system significantly increased the removal efficiency for NPYR from 76.3 % to 94.3 % at a pH of 7.0. The Cu-nZVI composites achieved a synergetic effect on the degradation of NPYR by regulating PS activation and reactive oxygen species (ROS) formation, promoting Fe2+/Fe3+ cycling with the Cu-nZVI surface and accelerating the electron transport capacity. The bursting tests and electron paramagnetic resonance (EPR) tests confirmed that multiple types of ROS coexisted in the Cu-nZVI/PS system. Furthermore, vulnerable sites and degradation pathways on the NPYR molecule were predicted by density functional theory (DFT) calculations. Toxicity predictions revealed decreased biotoxicity of NPYR and its intermediates. The NPYR removal efficiency decreased slightly to 81.1 % after 30 days of ageing, which demonstrates the excellent potential of the composites for realistic applications.

Persulfate activation by nanoscale zero-valent iron supported by modified blast furnace slag for degradation of phenol wastewater

Nano-zero valent iron (nZVI) was anchored and dispersed on the surface of acid-modified blast furnace slag (mBFS) through the liquid phase reduction method. The synthesized nZVI@mBFS composite exhibited remarkable ability to degrade phenol when used in conjunction with persulfate (PDS), 97.8% phenol could be eliminated in 30 min. All the anions like SO42-, HCO3-, H2PO4-, and CO32- were detrimental to the phenol degradation in nZVI@mBFS system. Moreover, electron paramagnetic resonance (EPR) analysis and radical scavenging tests confirmed that SO4•-, •OH and •O2- were the principal reactive oxygen species (ROSs) generated during the reaction process. The potential degradation pathways were also deduced based on the results obtained from gas chromatograph-mass spectrometer (GC-MS) analysis. Collectively, this study holds substantial significance in regards to recycling industrial solid wastes, devising efficient persulfate-activated materials, and treating wastewater.

Recent advances in bimetallic nanoscale zero-valent iron composite for water decontamination: Synthesis, modification and mechanisms

The environmental pollution of water is one of the problems that have plagued human society. The bimetallic nanoscale zero-valent iron (BnZVI) technology has increased wide attention owing to its high performance for water treatment and soil remediation. In recent years, the BnZVI technology based on the development of nZVI has been further developed. The material chemistry, synthesis methods, and immobilization or surface stabilization of bimetals are discussed. Further, the data of BnZVI (Fe/Ni, Fe/Cu, Fe/Pd) articles that have been studied more frequently in the last decade are summarized in terms of the types of contaminants and the number of research literatures on the same contaminants. Five contaminants including trichloroethylene (TCE), Decabromodi-phenyl Ether (BDE209), chromium (Cr(VI)), nitrate and 2,4-dichlorophenol (2,4-DCP) were selected for in-depth discussion on their influencing factors and removal or degradation mechanisms. Herein, comprehensive views towards mechanisms of BnZVI applications including adsorption, hydrodehalogenation and reduction are provided. Particularly, some ambiguous concepts about formation of micro progenitor cell, production of hydrogen radicals (H·) and H2 and the electron transfer are highlighted. Besides, in-depth discussion of selectivity for N2 from nitrates and co-precipitation of chromium are emphasized. The difference of BnZVI is also discussed.

Polyacrylate stabilized ZVI/Cu bimetallic nanoparticles for removal of hexavalent chromium from wastewater

In this work, a magnetic core-shell composite zero-valent iron/copper-polyacrylate (ZVI/Cu-PAA) was synthesized by a simple liquid-phase reduction process and used for hexavalent chromium Cr(VI) removal from wastewater. The optimization experiments show that the optimal dosages of polyacrylate and Cu are 7.00 wt% and 8.25 wt%, respectively. The maximum adsorption capacity and removal rate of Cr(VI) by ZVI/Cu-PAA reached 106.12 mg g^-1 and 99.05% at pH 5.5, respectively. Furthermore, the presence of coexisting ions such as Ca²⁺, Mg²⁺, Na⁺, and NO₃^- had no significant effect on its Cr(VI) removal performance. The excellent performance of ZVI/Cu-PAA is attributed to that the modification of polyacrylate can not only give more active sites but also inhibit agglomeration of nano-metallic particles, while Cu doping promotes the electron generation and transformation of Fe(III)/Fe(II) and Cu(II)/Cu(I) redox cycles. This makes ZVI/Cu-PAA has rich active sites and excellent stability, and has broad application prospects in the remediation of Cr (VI) polluted wastewater. The magnetic core-shell composite ZVI/Cu-PAA has excellent Cr (VI) removal performance because of its rich active sites and high electron transformation efficiency.

Cu-Fe embedded cross-linked 3D hydrogel for enhanced reductive removal of Cr(VI): Characterization, performance, and mechanisms

Porous hydrogel, as a high-efficiency adsorbent for heavy metals, suffers the drawbacks of the use of expensive and toxic reagents during the process of preparation, further limiting its application ranges. Besides, the heavy metals couldn't be transformed into nontoxic species, which leads to the environmental pollution risk. Herein, a three-dimensionally (3D) structured Cu-Fe embedded cross-linked cellulose hydrogel (nFeCu-CH) was innovatively fabricated by a novel self-assembly and in-situ reduction method, which exhibited exceptionally enhanced adsorption-reduction property towards Cr(VI) wastewater. The results of degradation experiment exhibited that the removal reaction followed Langmuir-Hinshelwood first order kinetic model and the degradation rate constant decreased with solution pH and initial Cr(VI) concentration, while increased with nFeCu-CH dosage and temperature. Regeneration studies demonstrated that more than 88% of Cr(VI) was removed by nFeCu-CH even after five times of cycling. nFeCu-CH exhibited excellent reductive activity, which had a close connection with the superiority of 3D crosslinked architectures and bimetallic synergistic effect. And 97.1% of Cr(VI) could be removed when nFeCu-CH dosage was 9.5 g/L, pH was 5, initial concentration of Cr(VI) was 20 mg/L and temperature was 303 K. Combined with cellulose hydrogel not only could provide additional active sites, but also could restrain the crystallite growth and agglomeration of nano-metallic particles, leading to the promotion of Cr(VI) removal. In addition, coating with Cu facilitated the generation and transformation of electrons according to the continuous redox cycles of Fe(III)/Fe(II) and Cu(II)/Cu(I), leading to the further improvement of the reductivity of nFeCu-CH. Multiple interaction mechanisms including adsorption, reduction and co-precipitation between nFeCu-CH and Cr(VI) were realized. The current work suggested that nFeCu-CH with highly reactive sites, excellent stability and recyclability was considered as an potential material for remediation of Cr(VI) contaminated wastewater.

Nanoscale Fe0/Cu0 bimetallic catalysts for Fenton-like oxidation of the mixture of nuclear-grade cationic and anionic exchange resins

Spent resins generated from the nuclear industrial processes are still difficult to be treated and disposed. Fenton-like processes have great application potential in the treatment of spent resins, but the Fenton reaction mechanisms and resin degradation pathways remain challenging. In this study, nanoscale Fe⁰/Cu⁰ bimetallic catalysts were prepared and characterized for the Fenton-like degradation of the mixture of cationic and anionic resins. High catalytic property of Fe⁰/Cu⁰ bimetallic nanoparticles activated by H₂O₂ was evaluated, according to the effects of various nanoparticles, temperature, catalyst amount, H₂O₂ concentration and the mixing ratio of cationic and anionic resins. Combined the shape and color changes of mixed resins with the experimental and calculated characterization results, different degradation difficulty of cationic and anionic resins and their degradation mechanisms were studied. According to the density functional theory calculations of the optimized resin molecules with the Fe⁰/Cu⁰ catalyst, the mechanisms of Fenton-like reactions and the degradation of mixed resins through the synergistic effect of Fe and Cu species were proposed. The comprehensive Fenton-like reactions and degradation mechanisms provide new insights to advance the treatment of spent resins and organic polymers by Fenton-like processes.

The removal mechanism of nitrobenzene by the Cu-Fe/Carbon material under different aeration conditions

Zero-valent Cu-Fe bimetallic porous carbon materials were successfully applied to remediate organic wastewater. In this work, we successfully recycled the layered double hydroxides (LDHs) adsorbed with Orange II (OII) to form a zero-valent Cu-Fe bimetallic porous carbon material (CuFe/Carbon). The characterization results showed that CuFe/Carbon was a zero-valent Cu-Fe bimetallic porous graphene-like carbon material. In the course of the experiment, we found that aeration condition had a great influence on the activity of CuFe/Carbon. The removal efficiency of nitrobenzene (NB) was 100 % in nitrogen system and 48 % in air system. The active species of O₂^- and OH was formed under air condition, while there was no active species under nitrogen condition. NB was reduced to aniline directly under nitrogen condition. We proposed there were reduction and oxidation mechanisms under different aeration conditions. This work mainly investigated the conversion process of a novel material under different reaction conditions, which provided theoretical support for the removal of organic matters.

Effects of green synthesis, magnetization, and regeneration on ciprofloxacin removal by bimetallic nZVI/Cu composites and insights of degradation mechanism

In this study, nanoscale zerovalent iron (nZVI) with copper (Cu) bimetallic particles, whichare applied for degradation of Ciprofloxacin (CIP) under weak magnetic field (WMF), were synthesized using green tea extracts (GT-nZVI/Cu). The surface morphology and physicochemical properties of the novel catalytic materials were characterized. It was found that GT-nZVI was more stable and performed better in oxidation resistance than the nZVI synthesized by traditional chemical methods. Besides, the catalytic reactivity of GT-nZVI/Cu was measured with and without WMF, it is obvious from the experimental results the performance of GT-nZVI/Cu system was enhanced significantly with WMF. Moreover, WMF still had a certain effect even after being removed, which is called remanence effect. The mass spectrometry (MS) was utilized to analyze the degradation products of CIP, and the contribution of adsorption and Fenton/Fenton-like oxidation of GT-nZVI/Cu during CIP removal process was further evaluated. It was found that as the removal process progressed, the contribution ratio of Fenton/Fenton-like oxidation rose rapidly and exceeded adsorption after 20 min. Eventually, attempts have been made to regenerate GT-nZVI/Cu, in which physical recovery (ultrasonic) was the main route, and the CIP removal rate decreased as the regeneration times increased. This research provides new insights into the green synthesis and regeneration of nZVI and is expected to realize the practical application of nZVI.