Decomposition Of Molecules Research Articles

Automated Measurement of Electrogenerated Redox Species Degradation Using Multiplexed Interdigitated Electrode Arrays.

Characterizing the decomposition of electrogenerated species in solution is essential for applications involving electrosynthesis, homogeneous electrocatalysis, and energy storage with redox flow batteries. In this work, we present an automated, multiplexed, and highly robust platform for determining the rate constant of chemical reaction steps following electron transfer, known as the EC mechanism. We developed a generation-collection methodology based on microfabricated interdigitated electrode arrays (IDAs) with variable gap widths on a single device. Using a combination of finite-element simulations and statistical analysis of experimental data, our results show that the natural logarithm of collection efficiency is linear with respect to gap width, and this quantitative analysis is used to determine the decomposition rate constant of the electrogenerated species (k c). The integrated IDA method is used in a series of experiments to measure k c values between ∼0.01 and 100 s-1 in aqueous and nonaqueous solvents and at concentrations as high as 0.5 M of the redox-active species, conditions that are challenging to address using standard methods based on conventional macroelectrodes. The versatility of our approach allows for characterization of a wide range of reactions including intermolecular cyclization, hydrolysis, and the decomposition of candidate molecules for redox flow batteries at variable concentration and water content. Overall, this new experimental platform presents a straightforward automated method to assess the degradation of redox species in solution with sufficient flexibility to enable high-throughput workflows.

Macroscale superdurable superlubricity achieved in lubricant oil via operando tribochemical formation of fullerene-like carbon

Friction and wear are ubiquitous in moving mechanical assemblies, causing energy and equipment loss and producing harmful emissions. Mitigation efforts have long relied on oil-based lubricants, but challenges remain in achieving concurrent ultralow friction and wear without oil additives. Here, we demonstrate that a dual-phase TiB2-MoS2 film lubricated by oil without additives exhibits superdurable superlubricity characterized by a vanishingly small friction coefficient (0.007) and ultralow wear rate (10−9 mm3N−1m−1) maintained in lubricants over an unprecedentedly long sliding distance without performance deterioration. We identify a tribochemical route for the decomposition of oil molecules catalytically activated by the TiB2-MoS2 film, leading to operando formation of fullerene-like carbon that leads to diminished friction. First-principles calculations unveil strong stress responses of a TiB2 structural framework under wear strains, offering insights into the ultralow wear rate. These findings showcase a promising strategy to develop high-performance superlubricating materials that meet stringent conditions for demanding applications.

Eutectic Electrolytes with Doubly‐Bound Water for High‐Stability Zinc Anodes

AbstractThe aqueous zinc‐ion battery has the advantages of environmental friendliness, safety, and reliability, which is expected to be used for large‐scale energy storage. However, due to the high activity of water, the hydrogen evolution reaction (HER) easily occurs on the surface of the zinc anode during the charge–discharge process, which is accompanied by corrosion, by‐products, and dendrite formation. Herein, a new‐type eutectic electrolyte consisting of ZnCl2, tetramethylurea (TMU), and H2O with the optimal molar ratio of 1:3:1 (ZT‐1) is developed for the high‐stability zinc anodes. The H2O in this system is doubly bound through the coordination with Zn2+ and the hydrogen bonding with TMU, thus leading to the greatly inhibited activity of H2O. In addition, the H2O and TMU are successively stripped during the desolvation process of ZnCl2(TMU)(H2O), followed by the deposition of [ZnCl2] at the zinc interface. In this way, the tendency of HER, corrosion, dendrites, and by‐products induced by the decomposition of H2O molecules at the zinc interface is minimized, enabling a much more stable plating/stripping process of Zn2+. Consequently, the Zn//Zn symmetric cell can stably cycle for >2000 h, while the Zn//Cu half cell can stably cycle 800 times with an average Coulombic efficiency of 99.5%.

Hydrogen production from methane via liquid phase microwave plasma: A deoxidation strategy

In this paper, in order to improve hydrogen production, the effect of dissolved oxygen (DO) on methane (CH4) reforming was studied by liquid phase microwave discharge firstly. DO was reduced by deducing pressure and gas replacement, and the reaction mechanism was researched by radical detection. It was revealed that reducing DO can improve hydrogen (H2) yield and H2 selectivity and energy efficiency of hydrogen production. When microwave power was 900 W and the DO was decreased from 4.82 mg/L to 0.65 mg/L, the production and selectivity of H2 increased by 21.3 % and 22.6 % respectively, and the energy efficiency of hydrogen production increased by 33.1 %. Through the study on the characteristics of discharge radicals, it was concluded that ∙H extraction and ∙H coupling reaction and ∙OH oxidation ∙CHX are the main ways to produce hydrogen. The existence of DO affects the formation of H2 by limiting the decomposition of water molecules. In addition, the reduction of DO can improve the stability of discharge. These results indicate that reducing the DO can be a simple, effective and energy conservation method to increase the selectivity of target products in the liquid phase discharge reforming of CH4.

A DFT study on N2O oxidation and methanol synthesis over Bi4O6: single-site catalytic model of α-Bi2Mo3O12.

Catalytic conversion of methane to methanol is one of the most promising processes for effective natural gas resource utilization. In this work, Bi4O6-catalyzed oxidation of methane to methanol with N2O as an oxidizing reactant has been investigated by DFT calculation. For the overall reaction mechanism of three N2O molecules on Bi4O6 catalyst, two catalytic cycles were proposed. Cycle 1 involved the consecutive decomposition of the first two N2O molecules. Cycle 2 corresponded to the decomposition of the third N2O molecule. The activation barriers of the first and second N2O decomposition were computed to be 27.6 and 35.0kcal/mol, respectively. The third N2O decomposition in cycle 2 required 36.1kcal/mol activation barriers. Thus, cycle 1 was the main catalytic cycle for N2O as the cycle required lower in barriers than those of the other. Oxidation of methane to methanol on Bi4O7 and Bi4O8 catalysts was supposed to be a two-step mechanism consisting of H3C-H bond breaking and CH3-OH formation. The activation energies of the two steps were 32.7, 41.1, and 21.6, 17.2kcal/mol for Bi4O7 and Bi4O8, respectively. Thus, methane oxidation over Bi4O8 was found to be more energetically favorable than those of Bi4O7, in which C-H bond breaking is the RDS. The present catalyst could be a promising material for the oxidation of methane to methanol. In summary, the single-site catalytic model study would be beneficial for guiding and searching for potential catalysts in heterogeneously catalyzed N2O decomposition and methanol synthesis as green as possible. However, theoretical investigation of this kind of catalyst's extended model system must be taken into account.

(Invited) Flexocatalysis of Single Pt Atoms Loaded Graphitic Carbon Nitride (g-C3N4)

Single-atom catalyst as an advanced co-catalyst shows promising potential in energy fields such as water splitting, degradation of pollutants, chemical conversion field, etc. It takes advantage of increased active sites and sub-nanometer size effects with electron confinement by reducing the size of supported noble metals; furthermore, a single-atom catalyst maximizes the atomic efficiency of metals and provides a low atomic coordination number for the active center. In this work, we discovered that the isolated single atoms (SAs) stabilized by the support of g-C3N4 as named by SA-Pt/g-C3N4. Single-atom catalyst is synthesized by anchoring Pt atoms in graphitic carbon nitride (g-C3N4) with different Pt-loading [0.01wt% to 1wt% H₂PtCl₆·(H₂O)₆]. Under flexocatalytic process, the k rate constant of the SA-Pt/g-C3N4 with 0.01wt% of Pt is 3×10-3 s-1 for decomposition of dye molecules, which is 2 times the pristine g-C3N4. In addition, the flexocatalytic hydrogen evolution of SA-Pt/g-C3N4 provides H2 production, reaching nearly 125 μmolgh-1, which is 312% of the pristine g-C3N4 (~40 μmolgh-1). The working mechanism of flexocatalytic activity suggests the mechanical strain-induced flexoelectric potential (flexopotential) and proceeding with redox's electrochemical reaction. In addition, the single-atom act as a critical role in attracting electrons to accelerate the reaction process. The single-atom catalyst of 2D materials is highly potential for applying in water splitting and degradation of pollutants through the flexocatalytic process.

Combustion mechanisms of core–shell structured aluminized explosives under oxygen atmosphere: Reactive molecular dynamics simulations

We constructed four aluminized explosive nanoparticles (NPs) with core–shell structure, in which the explosives CL-20, HMX, RDX, and TATB serve as a core and the aluminum acts as a shell. The combustion processes of the aluminized explosive NPs under oxygen atmosphere at 2500 K were simulated by reactive molecular dynamics. The Al shells underwent a process of melting-diffusion–reaction-aggregation, which began from the initial surface shell to the block. O2 rarely directly participated in the initial decomposition of the explosive molecules and mainly reacted with the intermediates and free radicals. A large number of the solid aluminized substances generated during the combustion. The AlmOn clusters are the main component of solid aluminized substances, in which the Al and O atoms at the edge will react with C, the H and N atoms, while the AlmCn and AlmNn clusters distributed sporadically. The AlmOn cluster in the TATB@AlO NP has a block structure, while the others have sphere-shaped structures. This work may provide a theoretical basis for understanding the combustion mechanisms of the aluminized explosives.

Stable Dendrite-Free High-Voltage Lithium Metal Batteries Enabled by Localized High Concentration Fluoroethylene Carbonate Based Electrolytes

Lithium-metal anode has been considered as the Holy Grail anode to achieve high-energy-storage batteries. However, significant challenges still exist in developing the highly stable electrolytes for Li-metal anodes and high-voltage cathodes. In this work, a localized high-concentration electrolyte (LHCE, 1.48 M FEC/EMC/HFE-LiDFOB) is proposed to realize stable dendrite-free cycling with excellent ca. 85% capacity retention and >99.5% Coulombic efficiency (CE) in LiNi0.6Co0.2Mn0.2O2 (NCM622) batteries at 0.5 C after 150 cycles. The cycling stability is largely improved, which can be associated with the formation of the robust solid electrolyte interphase layer on Li-metal anode owing to the preferential decomposition of LiDFOB salt and fluoroethylene carbonate solvent molecules. This study greatly expands knowledge of LHCE and provides a perspective of electrolyte design to achieve high-energy-density LMBs.

Surface Film Formation from Sodium Polysulfide Decomposition on Sodium-Metal Anode Surface

Room-temperature sodium–sulfur batteries are being considered as an alternative next generation of energy storage devices to replace lithium–sulfur batteries due to lower costs of Na metal while keeping a high theoretical capacity. A comprehensive understanding of polysulfide decomposition mechanisms and passivation film formation on the Na–metal surface has challenged the development of this metal–sulfur chemistry. Here, using first-principles modeling, we study the adsorption of sodium polysulfide (NaPS) molecules on the Na-metal surface and investigate the Na2S film formation from soluble NaPS decomposition in the presence of different electrolyte solvents (i.e., EC, PC, and EC/PC mixture). We find that NaPS molecules strongly interact with the Na-metal surface via Na–S bonds, leading to charge migration from the metal to the adsorbates. Such strong adsorption precedes a complete spontaneous electron-transfer decomposition of NaPS to form an amorphous Na2S film on the anode surface. The reduction reaction mechanisms are identified for each electrolyte, suggesting that polysulfides are completely decomposed in a short time. The energetic properties suggest that the first and second steps in the reaction of NaPS decomposition in the mixture solvent are thermodynamically uphill. The decomposed S atoms from NaPS can insert into the Na slab, leading to Na2S formation. The decomposition of multiple NaPS molecules reveals that the reduction of further NaPS on the surface after the first one is sluggish and incomplete because of the passivating nature of the nascent Na2S film, while NaPS far from the surface remains in the electrolyte phase forming a soluble NaPS cluster dissolved in the solvent.

High-Pressure-Resistant Flexible Seven-in-One Microsensor Embedded in High-Pressure Proton Exchange Membrane Water Electrolyzer for Real-Time Microscopic Measurement

The high-pressure proton exchange membrane water electrolyzer (PEMWE) used for hydrogen production requires a high-operating voltage, which easily accelerates the decomposition of hydrogen molecules, resulting in the aging or failure of the high-pressure PEMWE. As the high-pressure PEMWE ages internally, uneven flow distribution can lead to large temperature differences, reduced current density, flow plate corrosion, and carbon paper cracking. In this study, a new type of micro hydrogen sensor is developed with integrated flexible seven-in-one (voltage; current; temperature; humidity; flow; pressure; and hydrogen) microsensors.

Preparation of Fe-loaded needle coke particle electrodes and utilisation in three-dimensional electro-Fenton oxidation of coking wastewater

Novel iron-loaded needle coke spherical electrodes were fabricated for the first time using the sintering method. With DSA as the anode, nickel foam as the cathode and the spherical electrodes as the particle electrodes, a three-dimensional (3D) electro-Fenton system was constructed to treat coking wastewater. Using the chemical oxygen demand (COD) removal efficiency of coking wastewater as an indicator of electrode performance, the optimal conditions for particle electrode preparation were determined by single-factor experiments as consisting of a 4:1 catalyst-to-binder ratio, Fe2+ loading for the preparation of the particle electrodes of 2.5%, a particle size of 5.5 ± 0.5 mm, and a sintering temperature of 400 °C. Response surface methodology was applied to model and optimise the 3D electro-Fenton process for treating coking wastewater. Under the optimal conditions of an electrode spacing of 5 cm, applied voltage of 11.15 V, initial pH of 2.62, and particle electrode dosing of 12.23 g L−1, the removal rates of COD, NH3–N, NO3−–N, total nitrogen, colour, and UV254 were 87.5%, 100%, 72.2%, 84.8%, 95%, and 72.4%, respectively. Spectral analysis revealed that the 3D electro-Fenton system strongly degraded coking wastewater, causing decomposition of large molecules of organic compounds and residuals primarily consisting of olefins and alkanes. Because the prepared particle electrodes exhibited stable physical and chemical structure, they have great potential for engineering applications due to their resistance to water flow erosion, stable catalytic reaction activity, and reusability.

Enhancing the surface polarization effect via Ni/NiMoOx heterojunction architecture for urea-assisted hydrogen generation

Electrocatalytic urea oxidation (UOR) has attracted significant interest as a promising anodic half-reaction to replace sluggish oxygen evolution reaction (OER) toward water splitting. However, the activation and decomposition of urea molecule maintains a challenge during electrocatalytic process because of its 6e− oxidation procedure. Herein, Ni nanoparticles decorated NiMoOx nanorod (Ni/NiMoOx) electrocatalyst with abundant heterojunction interfaces is fabricated and the density functional theory (DFT) calculation testifies that the interfaces are favorable for enhancing the conductivity and modulating the surface polarization of Ni/NiMoOx, thus improving its UOR’s activity. The Ni/NiMoOx performs superb electrocatalytic capacities toward UOR with a potential of 1.355 V (vs RHE) at 20 mA cm−2, and HER with an overpotential of 98 mV at 10 mA cm−2. A hybrid two-electrode water splitting cell is further assembled via applying the Ni/NiMoOx as both anodic and cathodic electrodes with presence of 0.33 M urea, delivering 50 mA cm−2 at voltage of 1.589 V. The findings help to provide a reliable strategy for rational reconstruction of Ni based metal oxide with rich interfaces for diverse electrocatalytic reactions.

Optimal ratio of hydrogen and carbon in steel, providing a minimum level of steel sorting at a metallurgical plant

The level of sorting of steel at a metallurgical enterprise depends significantly on the content of carbon and hydrogen in the steel. The task of the work was to determine the optimal ratios of the concentrations of these elements, providing a minimum level of sorting of continuously cast billets and sheets. The increase in carbon and hydrogen in the steel of the tundish prevents the formation of nonmetallic inclusions, reduces the oxidizing ability of H2O and reduces the sorting of steel by such defects as "captivity" and "bubble-swelling". It is shown that these defects are related to each other and are formed by the same chemical reactions of decomposition of water molecules by deoxidizing elements contained in the metal, such as Al, Si, Mn. In high-carbon steels, in order to reduce the number of "ultrasound defects", "network cracks" and breaks in the crust of a continuously cast billet, it is necessary to reduce the [H] content in the tundish metal. This is due to the fact that segregation processes develop during casting with the participation of dissolved carbon and hydrogen, followed by the release of H2 from sections of the steel supersaturated with hydrogen. It was found that in order to reduce the level of sorting at the enterprise and improve the quality of cast steel, it is necessary to ensure the optimal ratio of carbon and hydrogen in the metal at the tundish stage in accordance with the equation: [H, ppm] = -68.782 ∙ [% C] + 15.962. This equation is valid for low-alloy steels with a carbon content of 0.13 to 0.22%. For [C] < 0.13%, the recommended concentration of [H] is 7 ppm, and for [C] > 0.22%, the lowest possible hydrogen content in the steel should be.

Thermal Stability Analysis of Cellulose From Sago Fiber Waste (Metroxylon sago)

Sago pulp is a lignocellulosic waste rich in cellulose, so that it can be used optimally as a source of carbon and cellulose. Fixed carbon can be obtained maximally by determining the carbonization temperature. This research aims to determine the temperature of the cellulose sample starting to decompose and the energy required at the time of decomposition. The process of extracting cellulose from sago fiber waste uses NaOH alkalinization for delignification, bleaching with H2O2, and hydrolysis with HCl. Identification of lignin in sago fiber is known by the appearance of the C=O group in the wave region of 1734.01 cm-1 with strong intensity; after extraction, no peak number was found in the extracted cellulose FTIR spectrum. TGA analysis of cellulose underwent two stages of mass change, the first stage of decomposition of water molecules at a temperature of 47°C-203°C obtained a mass decrease of 5.69%, and the second stage of decomposition at a temperature of 287°C-397°C obtained a mass decrease of 58.95%. DSC analysis obtained two thermal properties of physical changes contained in two endothermic peaks, the first peak of water evaporation which required energy of 28,1120 J/g, and the second peak of decomposition, which required energy of 9.6188 J/g.

Theoretical insight into the reaction mechanism of ammonia dehydrogenation on iron-based clusters

Ammonia (NH3) molecule decomposition is a promising approach for H2 production with COx-free. Density functional theory (DFT) calculations are employed to investigate the NH3 molecule stepwise dehydrogenation on Fe6M (M = Fe, Mo, Ni, and Co) clusters. The stability of these clusters has been investigated, and the result shows that the stability of Fe-based clusters is enhanced with doping of other metals. The catalytic activity of metal clusters for ammonia decomposition is systematically investigated by analyzing the adsorption property and reaction barriers. NH3 prefers to bind to the atop metal atom through the N end, which is agreement with the electrostatic potential analysis. Moreover, the adsorption energies of NH3 are related to the d-band center of Fe-based clusters. The reaction energy barriers show that the last dehydrogenation step (NH* + * ⇌ N* + H*) is the rate-determining step for most investigated clusters. The overall dehydrogenation process is exothermic reaction, and by comparing the rate-determining step, the Fe6Mo(l) and the Fe6Ni(l) clusters can efficiently promote the NH3 dissociation reaction.

Synergistic degradation of methylene blue by laser cavitation and activated carbon fiber

Methylene blue is widely used, but highly toxic and difficult to be degraded. In this paper, a new method of synergistic degradation of methylene blue by laser cavitation and activated carbon fiber is proposed. This paper theoretically studies the synergistic degradation effect, including radical oxidation effect, shock wave breakdown effect and activated carbon fiber surface adsorption effect. The deep degradation of methylene blue was studied experimentally, and the key influencing factors were analyzed. The results show that: the reason why methylene blue can be degraded is because of the oxidation effect of hydroxyl radicals, thermal decomposition and adsorption of molecules on the surface of carbon fibers. The main factors affecting the degradation rate of methylene blue solution are laser energy and initial concentration of solution. The degradation rate increased by 37.4% with the increase of laser energy (12–48 mJ) and decreased by 2.6% with the increase of initial concentration (0.01–0.05 mg/ml). The maximum degradation rate (93%) of methylene blue solution was reached at 48 mJ and 0.01 mg/ml for 30 min. Compared with the traditional adsorption degradation of carbon fibers, the degradation rate of the synergistic degradation of methylene blue solution by laser cavitation and activated carbon fibers can be increased by about 80% in a short time (30 min).

Rectified SiC-Fe2O3 heterostructures for high efficient activation and degradation of sulfur hexafluoride in air atmosphere

Sulfur hexafluoride (SF6) has a global warming potential of 23,900 CO2 equivalent during 100 years and is the strongest greenhouse gas. Therefore, it is essential to develop a degradation method for SF6. The space charge region in heterojunctions can form charged active sites, thus facilitating the absorption and decomposition of SF6 molecules. Herein, rectified SiC-Fe2O3 heterostructures were designed and in-situ generated from SiC-FeOOH composites during the thermal degradation of SF6. The heterostructures can completely decompose 2 vol% SF6 in air atmosphere at 700 °C, and have a higher initial degradation ratio of 93.6% and a degradation amount of 99.0 mL g−1. Detailed characterizations reveal that electron donor SiC can facilitate the absorption of SF6 molecules via electrostatic attraction, and the electron acceptor Fe2O3 can offer electrons to SF6 molecules to break S-F bonds. The concept of such heterostructures makes it possible to deal with large-scale leaks of low-concentration SF6.

Unerroric of control of mutual compliance of the efficiency of hydrogen engines of unmanned vehicles in the conditions of mass production

The issues related to the reliability of hydrogen engines of unmanned vehicles and increasing the efficiency of using hydrogen as fuel when using the method of its production during the decomposition of hydrogen-containing molecules of liquid-phase organic compounds in a plasma discharge under the action of intense ultrasonic exposure are considered. Experiments have shown that as a result of decomposition in the acoustoplasma discharge of liquid hydrocarbons, solid-phase carbon-containing products are formed, chemical transformations occur in the liquid phase and hydrogen-containing combustible gas is formed. Hydrogen-containing gas can be used as fuel immediately after synthesis, i.e. it does not require separation, since in addition to hydrogen it contains only impurities of CO2 and water vapor. The purpose of the study is to formalize the basic conditions for tightening the control of mutual compliance with the efficiency of hydrogen engines of the same series in the conditions of their mass production. Methods of mathematical statistics and hardware-software modeling were used in the study. The term “unerroric of quality mutual compliance control” is introduced to describe a set of hardware and software tools for such control. The principle of in-depth testing of the technical condition of such engines of one series is described in a multidimensional formulation of the quality control problem for three of their operating parameters at once. The conditions for increasing the mutual correspondence of the measured values of such parameters in the conditions of serial production of hydrogen engines are formalized.

Advanced Photocatalytic Treatment of Wastewater Using Immobilized Titanium Dioxide as a Photocatalyst in a Pilot-Scale Reactor: Process Intensification.

In many nations, particularly those experiencing water scarcity, novel approaches are being applied to clean wastewater. Heterogeneous photocatalysis is the most widely used of these approaches because it entails the decomposition of organic molecules into water and carbon dioxide, which is a more ecologically benign process. In our study, we studied the photocatalytic degradation process on the effluent flumequine. This treatment is made through a solar pilot reactor in the presence of immobilized titanium dioxide with three light intensities and two types of water as solvents. A variety of factors that might influence the rate of deterioration, such as flow rate, light intensity, and initial concentration, have been investigated. The maximal degradation of flumequine was achieved at more than 90% after 2.5 h under optimal conditions (an initial concentration of 5 mg/L, three lamp light intensities, and a flow rate of 29 L/h). By combining the oxidized agent H2O2 with this process, the photocatalytic activity was improved further to 97% under the same conditions. The mineralization of this product has also been tested using total organic carbon (TOC) analysis. A high mineralization rate has been recorded at around 50% for a high initial concentration (20 mg/L) at a flow rate of 126 L/h. The results demonstrated the highly effective removal of flumequine and the efficacy of this photocatalytic system.

Graphene oxide supported Fe3O4-MnO2 nanocomposites for adsorption and photocatalytic degradation of dyestuff: ultrasound effect, surfactants role and real sample analysis

ABSTRACT Present work demonstrates the synthesis, characterisation and application of a novel hybrid nanocomposite GO@Fe3O4-MnO2 for adsorption and catalytic degradation of dyestuff malachite green and tartrazine from wastewater. The nanocomposite GO@Fe3O4-MnO2 was characterised by FT-IR, XRD, SEM-EDS and pHzpc. Effects of various optimising parameters such as contact time, solution pH, surfactants, light, adsorbent dose, ultrasonication and coexisting ions were investigated. The removal efficiencies of malachite green and tartrazine were observed as high as 99.9% and 98% under direct sunlight, respectively. The adsorption kinetics follows the pseudo-second order model (R2 = 0.99) where k2 for malachite green and tartrazine were 0.0097 and 0.0011 g mg−1 min−1, respectively, that means adsorption was controlled by chemisorption. Equilibrium adsorption isotherm of these dyes was analysed in the context of Langmuir and Freundlich models, and the maximum adsorption capacity for Langmuir isotherm was found to be 8.0 and 5.1 mg g−1 for malachite green and tartrazine, respectively. The percentage removal was initially low, but when the ultrasound was irradiated, the removal percentage (96% for malachite green and 98% for tartrazine) was drastically increased because of the formation of highly active •H and •OH radicals in the water through the decomposition of water molecules by the formation of hot spots. On treatment with H2O2, advance oxidation processes were observed with high remediation percentage (99.5% for malachite green and 98% for tartrazine) of dye. The synthesised GO@Fe3O4-MnO2 was finally used for the treatment of dyes from real water samples. The used nanocomposite was separated using an external magnet and recycled with 0.1 N HCl or 0.1 N NaOH as desired.