Degradation of chlortetracycline using nano micro-electrolysis materials with loading copper

Fe/Au galvanic nanocells to generate self-sustained Fenton reactions without additives at neutral pH

The generation of reactive oxygen species (ROS) via the Fenton reaction has received significant attention for widespread applications. This reaction can be triggered by zero-valent metal nanoparticles by converting externally added H2O2 into hydroxyl radicals (˙OH) in acidic media. To avoid the addition of external additives or energy supply, developing self-sustained catalytic systems enabling onsite production of H2O2 at a neutral pH is crucial. Here, we present novel galvanic nanocells (GNCs) based on metallic Fe/Au bilayers on arrays of nanoporous silica nanostructures for the generation of self-sustained Fenton reactions. These GNCs exploit the large electrochemical potential difference between the Fe and Au layers to enable direct H2O2 production and efficient release of Fe2+ in water at neutral pH, thereby triggering the Fenton reaction. Additionally, the GNCs promote Fe2+/Fe3+ circulation and minimize side reactions that passivate the iron surface to enhance their reactivity. The capability to directly trigger the Fenton reaction in water at pH 7 is demonstrated by the fast degradation and mineralization of organic pollutants, by using tiny amounts of catalyst. The self-generated H2O2 and its transformation into ˙OH in a neutral environment provide a promising route not only in environmental remediation but also to produce therapeutic ROS and address the limitations of Fenton catalytic nanostructures.

Natural pyrite-stimulative periodate activation: efficiency and mechanism study

Natural pyrite (NP) is an alternative catalyst for wastewater purification via advanced oxidation processes (AOPs). However, the activation performance and mechanism of periodate (PI) by NP have not yet been revealed. Herein, this work examines the activation performance of NP towards PI and its application in the degradation of antibiotic wastewater. Interestingly, 95.69% of chlortetracycline (CTC) was degraded by NP within 20 min via PI activation. Besides, NP shows effective degradation of various pollutants such as rhodamine B (65.81%), sulfamethoxazole (89.04%), and sodium butylxanthate (99.77%) within 20 min. The active species quenching experiment suggested that the active species ∙ OH ,IO 3 ∙ , 1O2 and the active complex of PI bonded with NP surface participated in CTC degradation. In addition, Fe(II) on NP surface is the main active site for PI activation, while Sn2- species accelerates the reduction of Fe(III) to Fe(II) and promotes sustained PI activation. This work provides new ideas for the application of NP in environmental pollution control.

Review in application of blast furnace dust in wastewater treatment: material preparation, integrated process, and mechanism

Blast furnace dust (BFD) is the solid powder and particulate matter produced by dust removal process in ironmaking industry. The element composition of BFD is complex, and a direct return to sintering will lead to heavy metal enrichment and blast furnace lining corrosion. In recent years, the application of BFD in wastewater treatment has attracted widespread attention. Based on the mechanisms of action of BFD in wastewater, this paper discusses in detail the application of BFD in iron-carbon micro-electrolysis, biological enhancement, adsorption, flocculation, and Fenton/Fenton-like reactions. Iron oxides and carbon in BFD are key substances. Thus, BFD has great potential as a raw material in wastewater treatment, and the waste utilization of BFD can be realized. However, the difference in elements and composition of BFD limits its large-scale application. We can classify BFD according to different proportions of elements. In the future, it is necessary to focus on the service life of BFD in water and whether it shall bring secondary pollution to water.

Characteristic analysis of s-Fe/Cu two-component micro-electrolysis materials and degradation of dye wastewater

Micro-electrolysis is a pretreatment technology for difficult-to-biodegrade wastewater. In this study, a chemical displacement method was used to load copper on the surface of sponge iron (s-Fe), and then it was mixed with activated carbon and other components to obtain a multi-element micro-electrolytic filler (OMEF). Through BET, SEM, XRD, XPS, and FT-IR characterization and analysis, OMEF was proved to have a specific surface area of 88.374 m²/g, C-C, C-O, C = O, O-C = O, and other functional groups and Fe₃C, MnO₂ and other active materials. The removal mechanism of organic pollutants in wastewater by OMEF could be due to the galvanic reaction, direct reduction of Fe, oxidation of Fe, catalytic oxidation of Cu and Mn, and co-precipitation of adsorption. The coupling of the micro-electrolysis and biological methods proved that OMEF had excellent application efficiency. The results indicated that the COD removal rates of OMEF and commercial fillers reached 88.39% and 48.02%, respectively, and the B/C reached 0.74 and 0.3. OMEF showed a better performance. The reusability of the OMEF filler was measured to ensure that the B/C was maintained at around 0.5 during 5 cycles. Kinetic analysis showed that the degradation data of methyl orange (MO) and the removal data of COD obeyed pseudo-second-order kinetics. Moreover, it can further broaden the pH range of treated wastewater and increase the oxidation rate. This new strategy has brought potential enlightenment for the development of high-efficiency wastewater pretreatment using new micro-electrolysis materials. The excellent performance of OMEF micro-electrolytic filler in pretreatment indicated its potential for industrial application.

Efficient, fast and robust degradation of chlortetracycline in wastewater catalyzed by recombinant Arthromyces ramosus peroxidase

Chlortetracycline (CTC), a widely used antibiotic, is recalcitrant and ubiquitous in the environment. Enzymatic degradation of CTC is an economical and efficient bioremediation method. In this work, recombinant Arthromyces ramosus peroxidase (rARP) at a concentration of 3.13 × 10^-9 M was used to catalyze rapid degradation of CTC in water. The second-order rate constants of rARP showed up to 62-fold catalytic efficiency of horseradish peroxidase (HRP) toward CTC. The degradation half-life of CTC at the concentrations of 2 and 40 mg L^-1 in wastewater under the rARP catalysis was, respectively, 5.3 and 5.7 min at 25 °C, and 2.7 and 3.1 min at 40 °C, which were up to 15-fold and 111-fold faster than HRP and laccase, respectively, but use of 3 % the amount of rARP as HRP. rARP catalyzed degradation of CTC at 2-40 mg L^-1 in wastewater completed in 20-24 min, and its catalytic efficiency varied within only 2-fold at 25-40 °C. rARP showed only 2-3-fold discrepancy of catalytic efficiency among pH 5.0, 7.5 and 9.0. CTC under rARP catalysis underwent demethylation and oxidation to form nontoxic N-dedimethyl-9-hydroxy-CTC. The high catalytic efficiency of rARP agreed with a short distance between rARP's δN-His⁵⁶ and CTC's dimethylamine N as indicated by docking simulation. rARP is a useful enzyme for CTC bioremediation.

Performance of high temperature phase-stable high entropy oxide (MgCuMnCoFe)O x in catalytic wet air oxidation of chloroquine phosphate

With the continuous spread of COVID-19, the water pollution problems caused by the abuse of chloroquine phosphate (CQP) as an antiviral drug have attracted wide attention. The cubic Fm-3m spinel high entropy oxide (HEO)-(MgCuMnCoFe)O _x was prepared by coprecipitation method as the catalytic wet air oxidation (CWAO) catalyst to treat CQP simulated wastewater. Through electron spin resonance (ESR) analysis, HEO will stimulate the production of superoxide radical (·O₂ ^-) and hydroxyl radical (·OH) in the wet air oxidation (WAO) process, which accelerates the degradation and mineralization of CQP. Through response surface method (RSM) optimization, the optimal degradation conditions of CQP in CWAO were proposed: initial oxygen pressure of 15 bar, catalyst dosage of 1.4 g/L and temperature of 230 °C. The advantages of HEO in CWAO were analyzed by principal component analysis (PCA). The degradation mechanism of CQP in CWAO by (MgCuMnCoFe)O _x were explored. This work provides a new idea for the rapid development of HEO in the field of environmental catalysis.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10853-022-07271-z.

New insights into iron/nickel-carbon ternary micro-electrolysis toward 4-nitrochlorobenzene removal: Enhancing reduction and unveiling removal mechanisms

The ternary micro-electrolysis material iron/nickel-carbon (Fe/Ni-AC) with enhanced reducibility was constructed by introducing the trace transition metal Ni based on the iron/carbon (Fe/AC) system and used for the removal of 4-nitrochlorobenzene (4-NCB) in solution. The composition and structures of the Fe/Ni-AC were analyzed by various characterizations to estimate its feasibility as reductants for pollutants. The removal efficiency of 4-NCB by Fe/Ni-AC was considerably greater than that of Fe/AC and iron/nickel (Fe/Ni) binary systems. This was mainly due to the enhanced reducibility of 4-NCB by the synergism between anode and double-cathode in the ternary micro-electrolysis system (MES). In the Fe/Ni-AC ternary MES, zero-iron (Fe⁰) served as anode involved in the formation of galvanic couples with activated carbon (AC) and zero-nickel (Ni⁰), respectively, where AC and Ni⁰ functioned as double-cathode, thereby promoting the electron transfer and the corrosion of Fe⁰. The cathodic and catalytic effects of Ni⁰ that existed simultaneously could not only facilitate the corrosion of Fe⁰ but also catalyze H₂ to form active hydrogen (H*), which was responsible for 4-NCB transformation. Besides, AC acted as a supporter which could offer the reaction interface for in-situ reduction, and at the same time provide interconnection space for electrons and H₂ to transfer from Fe⁰ to the surface of Ni⁰. The results suggest that a double-cathode of Ni⁰ and AC could drive much more electrons, Fe²⁺ and H*, thus serving as effective reductants for 4-NCB reduction.

A novel scheme for the utilization of Cu slag flotation tailings in preparing internal electrolysis materials to degrade printing and dyeing wastewater

About 60 million tons of Fe-rich Cu slag (IRCS) are generated annually worldwide during Cu slag flotation and cause irreversible water and soil pollution. Current research provides an environmentally friendly technology, the preparation of internal electrolysis materials (IEMs) through the carbothermal reduction of IRCS, for the degradation of printing and dyeing wastewater. XRD and SEM-EDS indicated that carbothermal reduction could promote the conversion of fayalite to zero-valent iron (ZVI), and ZVI could effectively form IEM with residual carbon. The degradation capacity of IEM for methylene blue (MB) was remarkably improved compared with raw IRCS after roasting for 60 min at 1100 °C with 35% anthracite dosage. MB degradation efficiency improved by increasing the IEM dosage and reaction temperature and decreasing the MB concentration and solution pH. FTIR, XRD, SEM-EDS, and XPS all detected the formation of Fe oxide or Fe hydroxide. UV-vis and TOC demonstrated that the characteristic groups of MB were destroyed and resulted in the mineralization of MB. MB degradation could be attributed to the Fe²⁺, [H], and ·OH produced by the galvanic reaction induced by IEM. Overall, this study offers theoretical guidance in the treatment of printing and dyeing wastewater and the reuse of IRCS.

Iron-carbon microelectrolysis for wastewater remediation: Preparation, performance and interaction mechanisms

Rapid industrialization and urbanization have produced a lot of hazardous substances in water and wastewater, which has turned into a crucial issue to the environment and the public health. Recently, iron carbon microelectrolysis (IC-ME) has attracted extensive attention in environmental remediation due to its low costs and excellent performance. Nevertheless, there is still a lack of a more systematic review on IC-ME preparation methods, their performance, and the interaction mechanisms of IC-ME in the remediation of wastewater. Herein, this work summarizes the synthetic methods, application of IC-ME materials, and the mechanism of pollutant removal by IC-ME. A variety approaches have been applied to prepare IC-ME materials, and the preparation methods and conditions have a certain influence on the properties of IC-ME materials, thus affecting the performance of pollutant removal. The mechanisms of IC-ME for contaminants removal are very complex, including adsorption, coprecipitation, reduction, surface complexation, and oxidation. Moreover, research vacant fields and problems that existed in the application of IC-ME are proposed. At last, the problems to be addressed to adapt IC to future applications are introduced. This paper reviews and prospects IC-ME wastewater remediation technology, which provides a reference for further scientific research and engineering applications.

Enhanced reactivity and electron selectivity of GAC-Fe-Cu ternary micro-electrolysis system toward p-chloronitrobenzene under oxic conditions

A novel GAC-Fe-Cu ternary micro-electrolysis system was synthesized for the removal of p-chloronitrobenzene (p-CNB) under oxic conditions. p-CNB could be efficiently removed by GAC-Fe-Cu at a wide initial pH range of 1.0-9.0. In particular, the p-CNB removal efficiency of 96.96 % was obtained at initial pH of 7.2, and the degradation (44.96 %) was the major removal pathway. Additionally, reduction and oxidation simultaneously contributed to the degradation of p-CNB. The results indicated that OH was the prime reactive species under acidic conditions while O₂^- dominated the degradation of p-CNB under neutral conditions. Reduction reaction was remarkably enhanced in the presence of dissolved oxygen and the iron corrosion could be accelerated by in-situ generated H₂O₂. Furthermore, XPS analysis of GAC-Fe-Cu revealed the surface-mediated electron transfer and oxidant generation process. The excellent degradation efficiency of p-CNB at initial pH of 7.2 was attributed to the enhanced electron selectivity of GAC-Fe-Cu as well as the high selectivity of near-surface generated O₂^- toward p-CNB and its intermediate products.

Rapid decontamination of tetracycline hydrolysis product using electrochemical CNT filter: Mechanism, impacting factors and pathways

In this study, electrooxidation of the tetracycline hydrolysis products was investigated using a carbon nanotube (CNT) electrochemical filter and 4-epianhydrochlortetracycline (EACTC) as a model compound. Electrochemical filtration of 10 μmol L^-1 EACTC at a voltage of 2.5 V and a flow rate of 1.5 mL min^-1 (hydraulic residence time <3 s) provided an oxidation flux of 1251 ± 28 μmol h^-1 m^-2. Replacement of the Ti cathode with a CNT filter cathode increased the EACTC oxidative flux by 1.3 fold at a voltage of 2.5 V. The electrochemical filtration process is effective for the degradation of EACTC and the reduction of the antimicrobial activity based on liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) analysis and luminescent bacteria test. The high oxidation flux within 300 min (1212-1263 μmol h^-1 m^-2) and affordable cost (0.25 kWh m^-3) at a voltage of 2.5 V show the potential application of the electrochemical filtration system as a promising unit for EACTC degradation. These findings provided new insights into the rational design principles of novel continuous-flow filtration system aimed to efficiently remove hydrolysis products of the antibiotic tetracycline.

One-Step Synthesis of Metal-Modified Nanomagnetic Materials and Their Application in the Removal of Chlortetracycline

Magnetic nanomaterials are promising heterogeneous catalysts for environmental applications. According to X-ray diffraction, Brunauer-Emmett-Teller method, scanning electron microscopy, high-resolution transmission electron microscopy, and vibrating-sample magnetometer, a kind of copper-modified nanomagnetic material (Cu-nFe₃O₄) was successfully prepared by a one-step synthesis method. Among them, compared with the two-step synthesis method of Cu/Fe₃O₄ and Cu/nFe₃O₄, Cu-nFe₃O₄ has the best effect on chlortetracycline (CTC) removal. The batch study results indicate that the maximum removal of chlortetracycline is 99.0% at a dosage = 2.0 g L^-1, copper loading = 0.8 mM, and C ₀ = 100 mg L^-1 at the optimum conditions within 90 min. The effects of humic acids (HA), NO₃ ^-, Cl^-, CO₃ ^2-, and PO₄ ^3- on the CTC removal by Cu-nFe₃O₄ are also investigated. Repeated experiments were performed on the prepared Cu-nFe₃O₄, indicating that Cu-nFe₃O₄ has good recyclability. The kinetics of the Cu-nFe₃O₄ removal of CTC was investigated, indicating that the reaction conformed to the double constant model and the reaction is mainly dominated by a chemical reaction with physical adsorption. Finally, the mechanism of the CTC removal by Cu-nFe₃O₄ in a heterogeneous environment was clarified. This study aims to provide an experimental basis for the environmental application of Cu-nFe₃O₄.

Removal of chlortetracycline by nano- micro-electrolysis materials: Application and mechanism

Nano micro-electrolysis materials (nMETs) have been used to degrade refractory pollutants in batch experiments. The reasonable formation mechanism of nMETs was given through DMXY digital biomicroscopy. Based on the kinetic data of Chlortetracycline (CTC) removal by nMETs in batch experiments, combined with the binomial distribution equation of CTC reduction by nano materials an experimental-scale fluidized bed (ESFB) was designed. The effects of CTC removal performance, pH and iron ion concentration were investigated. Under pure CTC solution environment, the experimental data showed that the average removal rates of CTC by nMET and nano micro-electrolysis material with loading copper (Cu-nMET) are 90.0% and 95.7% in ESFB, respectively. In the presence of nitrate, although the consumption of two kinds of nano-materials increased, their removal efficiencies of pollutants have 2.2%, 0.2% increase compared with the nitrate-free ESFB. At the same time, the CTC degradation pathway and the enhanced removal mechanism by Cu-nMET was proposed. Through microelectrolysis reaction, complexation reaction and the active substances produced, the intermediate products can be degraded completely to NH₄⁺, CO₂, H₂O and so on. This study aims to provide a theoretical basis for the environmental application of nMETs.