Multi-walled Carbon Nanotubes Catalysts Research Articles

Influence of TiO2 coverage on activity and stability of Pd-TiO2/MWCNT-supported catalysts used in direct formic acid fuel cells

Pd and TiO2 supported on functionalized multiwall carbon nanotubes (f-MWCNTs) catalysts were investigated in formic acid electrooxidation reaction in direct formic acid fuel cell. TiO2 (5–60 wt.% loading) on f-MWCNTs was deposited using microwave-assisted hydrothermal method. 20 wt.% of Pd was deposited on TiO2/f-MWCNTs by reduction of palladium (II) chloride salt with sodium borohydride. Catalysts’ structure and composition were characterized by XRD, STEM, HR-TEM, TGA, XPS/XAES (Pd, Ti, O spectra features, density of valence states, Auger parameters). Average crystallite size of Pd and TiO2 from XRD (3–4 nm) agrees with those by HR-TEM (3–5 nm). Low TiO2 coverages (below 32wt.%) show smaller crystallites due to increased surface hydrophilicity, higher amount of TiO2 oxygen vacancies with attached Pd nanoparticles, increased density of valence states of strong Pd–TiO2 interface. In contrary, the higher coverages indicate lower amount of Pd–O–Ti, Ti–O–C, Pd–O–C interfaces, with electron charge transfer from TiO2 to f-MWCNTs, and to Pd. Catalysts activity (40–106 mWmgPd−1) and stability (5–240 h) are enhanced at low TiO2 coverages (4–8 wt.%) due to a strong Pd-TiO2 interface on oxygen vacancies, improved electron transport and a high active surface area. Oscillatory self-cleaning mechanism of Pd is due to oxidation by -OH groups (TiO2, f-MWCNTs), and hydrogen and CO spillover.

Catalytic Partial Oxidation of Methane to Methanol over Fe2O3/MWCNTs

The catalytic partial oxidation of methane (CPOM) to methanol has been regarded as a promising approach for methane utilization, despite that the conversion remains a formidable challenge in the perspective of catalysts. A novel catalyst system of multi-wall carbon nanotubes (MWCNTs) that supported Fe2O3 with existing I2, consisting of non-noble metal and working in weak acid at an ambient temperature, was investigated for CPOM. MWCNTs supported the Fe2O3 catalyst, which was prepared by the impregnation method and characterized via HRTEM, XRD, XPS, FT-IR, and BET techniques. The characterization results reveal that, as a non-noble metal catalyst, the Fe2O3/MWCNTs catalyst had a good catalytic performance and stability in the CPOM. With the variation of reaction pressure and the dosage of Fe2O3/MWCNTs, the catalyst system obtained the highest methane conversion rate of 7.41% and methanol selectivity of 86.3%, which is analogous to that of the equivalently strong acid catalyst system. The I2-Fe2O3/MWCNTs catalyst system has great potential in the application of CPOM under mild, environmentally benign conditions, such as non-noble metal requirement, ambient temperature, and weak acid. The reaction mechanism was discussed.

Bimetallic RuNi Electrocatalyst Coated MWCNTs Cathode for an Efficient and Stable Li-CO2 and Li-CO2 Mars Batteries Performance with Low Overpotential.

Rechargeable lithium-CO2 (Li-CO2 ) batteries are an attractive energy storage technology that can reduce fossil fuel usage and limit the adverse environmental impact of CO2 emissions. However, the high charge overpotential, unstable cycling, and incomplete understanding of the electrochemical process limit its advancement for practical applications. Herein, we develop a Li-CO2 battery by designing a bimetallic ruthenium-nickel catalyst onto multi-walled carbon nanotubes (RuNi/MWCNTs) catalyst as cathode by solvothermal method, which exhibits a lower overpotential of 1.15 V and a discharge capacity of 15,165 mAh g-1 with outstanding coulombic efficiency of 97.4 %. The battery can also operate at high rates and have a stable cycle of more than 80 cycles at a current density of 200 mA g-1 with a fixed 500 mAh g-1 capacity. Furthermore, Mars exploration is made feasible with the Li-CO2 Mars battery composed of the RuNi/MWCNTs as cathode catalyst, which performs very similarly to that of pure CO2 atmosphere. This approach may simplify the process of developing high-performance Li-CO2 batteries to achieve carbon negativity on Earth and for future interplanetary Mars missions.

Mixed phase nanoarchitectonics of NiS@SnS@Ni3Sn2S2 as a tetrafunctional catalyst for dye-sensitized solar cells, supercapacitors, and water splitting applications

The development of low-cost, high-efficiency multifunctional electrocatalysts is an ongoing concern, and it is critical for future energy-related devices. Mixed-phase NiS@SnS@Ni3Sn2S2 nanostructures are synthesized by facile microwave approach and are used as an electrocatalyst for the reduction of tri-iodide to iodide (I3−/I−) in dye-sensitized solar cells (DSSCs), asymmetric supercapacitors, and overall water-splitting applications. Further, the performances have been improved by adding multi-walled carbon nanotubes (MWCNT). For assessing the crystalline structure, phase, size, shape, porosity, and composition, several analytical tools are employed. The electrochemical outcomes show that NiS@SnS@Ni3Sn2S2/MWCNT counter electrode assisted DSSC cell delivered the highest efficiency of 6.0 % and found to be an efficient electrode for supercapacitors, evidencing a large specific capacitance (766 F g−1 at 1 A g−1), an outstanding energy density of 85.2 W h kg−1 at an ultra-high-power density of 3600 W kg−1 and cycling stability (94 % after 10,000 cycles at 15 A g−1). Furthermore, the optimized NiS@SnS@Ni3Sn2S2/MWCNT catalyst demonstrates better oxygen and hydrogen evolution reaction. The combination of different phases and shapes in the catalysts can provide a synergistic effect as well as good surface active sites along with a carrier transfer path, resulting in efficient I3− reduction, higher specific capacitance and energy density, superior cycling stability, and low over-potential, thus making NiS@SnS@Ni3Sn2S2/MWCNT hybrid as an efficient tetrafunctional electrocatalyst for energy gadgets.

NiS/MoS2 Anchored Multiwall Carbon Nanotube Electrocatalyst for Hydrogen Generation and Energy Storage Applications

AbstractAlthough sulfide‐based materials are known to be efficient catalysts for oxygen evolution reactions (OER), hydrogen evolution reactions (HER), and supercapacitor applications, improving the catalytic activity of sulfide materials for both electrochemical water splitting and supercapacitors remains a challenging problem. Here, an easy and one‐step integrated methodology is implemented to develop NiS/MoS2 anchored multiwall carbon nanotubes (MWCNT/NiS/MoS2) catalysts that can effectively and robustly catalyze both the HER and OER. The MWCNT/NiS/MoS2 hybrid composite offers the lowest overpotential of 201 mV and 193 mV to achieve a current density of 10 mA/cm2 and −10 mA/cm2 with a small Tafel slope of 58 mV/dec 41 mV/dec for OER and HER, respectively, in alkaline and acidic conditions. The obtained multi‐walled carbon nanotubes anchored with intertwined NiS/MoS2 have a significant number of active sites and defects throughout the structure. The hybrid composite electrode delivered a specific capacitance of >371.45 F/g at 2 A/g in a two‐electrode system, along with high energy density of 51.63 Wh/kg (ED) along with the power density (PD) of 953.63 W/kg, and good capacitance retention ∼82% after 2000 cycles. Therefore, a tandem electron transfer mechanism between NiS and MoS2 (MoS2→NiS) is believed to have an electrical synergistic effect that promotes both HER and OER activity. This research opens a new path for the construction of multi‐component, cheap electrocatalysts that are highly effective for overall water splitting and energy storage applications.

Switching the locus of oxygen reduction and evolution reactions between spinel active phase and carbon carrier upon heteroatoms doping

Multi-walled carbon nanotubes (MWCNTs) doped with nitrogen and sulfur atoms and with deposited manganese–cobalt spinel catalysts were studied to reveal the role of active centers in the oxygen reduction and evolution reactions (ORR and OER) in alkaline media. Commercial MWCNTs were oxidized by boiling in concentrated nitric acid and then double-doped with N and S heteroatoms using thiourea precursor. Manganese-cobalt spinels supported on the MWCNTs were synthesized by a microwave-assisted solvothermal route. The catalysts were comprehensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and X-ray fluorescence spectroscopy. The deposited mixed spinel active phase consists of well-dispersed nanocrystals with sizes in the range of 5–8 nm. The electrocatalytic activities of the synthesized catalysts in ORR (the onset potential and the number of transferred electrons) and OER (the overpotential required to reach the 10 mA cm−2 current density) were examined in alkaline media by rotating ring-disc electrode (RRDE) and rotating disc electrode (RDE) techniques, respectively. It was found that N and S doped MWCNT catalysts exhibit high activity in ORR with Eonset = 0.890 ± 0.013 V, and a number of electrons exchanged n = 3.83 ± 0.03, which remained essentially the same, within experimental error, upon spinel deposition. The addition of the spinel phase does not improve the electrocatalytic properties. The advantage of the dispersed spinel active phase was observed in OER, the activity of these samples was comparable to that of the RuO2 benchmark catalyst. In the case of ORR, the observed reactivity was accounted for by the incorporation of nitrogen and sulfur to the MWCNTs, whereas for OER the locus of the active centers is moved towards the manganese-cobalt spinel nanocrystals dispersed on the carbon nanotubes matrix. Functionalization of the latter with N and S atoms is then catalytically redundant.

A “Special” Solvent to Prepare Alloyed Pd2Ni1 Nanoclusters on a MWCNT Catalyst for Enhanced Electrocatalytic Oxidation of Formic Acid

Herein, an electrocatalyst with Pd2Ni1 nanoclusters, supporting multiwalled carbon nanotubes (MWCNTs) (referred to Pd2Ni1/CNTs), was fabricated with deep eutectic solvents (DES), which simultaneously served as reducing agent, dispersant, and solvent. The mass activity of the catalyst for formic acid oxidation reaction (FAOR) was increased nearly four times compared to a Pd/C catalyst. The excellent catalytic activity of Pd2Ni1/CNTs was ascribed to the special nanocluster structure and appropriate Ni doping, which changed the electron configuration of Pd to reduce the d-band and to produce a Pd-Ni bond as a new active sites. These newly added Ni sites obtained more OH- to release more effective active sites by interacting with the intermediate produced in the first step of FAOR. Hence, this study provides a new method for preparing a Pd-Ni catalyst with high catalytic performance.

Precisely tuning the electronic structure of ordered PtFe alloy supported on multi-walled carbon nanotubes for enhanced methanol oxidation

The ordered intermetallic compounds have attracted significant attention due to their higher electrocatalytic activity and stability. In this study, the ordered PtFe intermetallic nanoparticles (NPs) with different feeding molar ratios of Pt and Fe supported on multi-walled carbon nanotubes (MWCNTs) have been successfully synthesized via co-engineering of the surface composition and electronic structure. Benefitting from the appropriate electronic interactions between Pt and Fe atoms, the high ordered degree of PtFe alloy and the strong interaction between PtFe intermetallic NPs and MWCNTs, the Pt1Fe2.5/MWCNTs catalyst with appropriate surface composition displays better activity, stability, and anti-CO poisoning capability in methanol oxidation as compared to the commercial Pt/C catalyst. Specifically, the mass and specific activity of the Pt1Fe2.5/MWCNTs catalyst is 1.01 mA.ug−1Pt and 1.85 mA.cm−2, which are enhanced by 5.31 and 6.85 times relative to the values of commercial Pt/C catalyst, respectively. Moreover, the CO oxidation on the surface of the Pt1Fe2.5/MWCNTs catalyst (0.703 V) starts earlier than on the commercial Pt/C catalyst (0.801 V). The demonstrated strategy provides new insight into the preparation of Pt-based catalysts with controllable surface composition and high catalytic performance.

Pd3Co1 Alloy Nanocluster on the MWCNT Catalyst for Efficient Formic Acid Electro-Oxidation

In this study, the Pd3Co1 alloy nanocluster from a multiwalled carbon nanotube (MWCTN) catalyst was fabricated in deep eutectic solvents (DESs) (referred to Pd3Co1/CNTs). The catalyst shows a better mass activity towards the formic acid oxidation reaction (FAOR) (2410.1 mA mgPd-1), a better anti-CO toxicity (0.36 V) than Pd/CNTs and commercial Pd/C. The improved performance of Pd3Co1/CNTs is attributed to appropriate Co doping, which changed the electronic state around the Pd atom, lowered the d-band of Pd, formed a new Pd-Co bond act at the active sites, affected the adsorption of the toxic intermediates and weakened the dissolution of Pd; moreover, with the assistance of DES, the obtained ultrafine Pd3Co1 nanoalloy exposes more active sites to enhance the dehydrogenation process of the FAOR. The study shows a new way to construct a high-performance Pd-alloy catalyst for the direct formic acid fuel cell.

Revealing the Effect of Surface Composition on Multiwalled Carbon Nanotubes Supported Pt-Fe Alloy Electrocatalysts for Methanol Oxidation Performance.

The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1 Fe3 @NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt ) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt ). Furthermore, the CO oxidation initial potential of Pt1 Fe3 @NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1 Fe3 @NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field.

Fe-CONTAINING CARBON NANOTUBES AS CATALYSTS IN THE AEROBIC OXIDATION REACTIONS OF DECALIN AND TETRADECANE

This article studies the catalytic activity of multi-walled carbon nanotubes (MWCNTs) in the oxidation reactions of aliphatic and polycyclic hydrocarbons is studied. In order to determine the catalytic activity, MWCNTs catalysts containing 22.8% Fe each were used. Catalyst samples were synthesized from propane gas under optimal conditions determined by CVD method. The experiments were performed at 5 different temperatures (60, 80, 100, 120, 1400C) for 2 hours. No significant change in the oxidation reaction of both hydrocarbons was observed at relatively low temperatures. In the oxidation of decalin, when the reaction temperature rises to 1200C and 1400C, oxidation has already taken place, and the rate of the reaction is directly proportional to the increase in temperature. The same trend can be seen in the oxidation reaction of tetradecane at MWCNTs with temperatures of 120 and 1400C. However, unlike decalin, the MWCNTs sample in tetradecane oxidation showed optimal catalytic performance at 1200C. However, at these temperatures, where oxidation occurs, the oxidation of decalin and tetradecane in an environment without a catalyst is almost non-existent

Application of multi-wall carbon nanotubes supported l-proline in continuous flow catalysis

l-proline on multi-wall carbon nanotubes (l-proline/MWCNTs) catalysts doped with suitable auxiliary support materials are successfully applied in the continuous flow catalytic syntheses, including Aldol reaction, Mannich reaction and Knoevenagel condensation reaction. With the advantages of easy operation, high efficiency and excellent stability, this method is promising in large-scale synthesis.

A novel and active ruthenium based supported multiwalled carbon nanotube tungsten nanoalloy catalyst for sodium borohydride hydrolysis

At present, a novel and active catalyst, RuW/MWCNT catalyst, was successfully synthesized to complete the hydrolysis reaction of sodium borohydride (NaBH4). The activity of Ru catalyst was increased by adding tungsten (W) to ruthenium (Ru) on multi-walled carbon nanotube (MWCNT) support. Surface characterization of the catalyst was performed with scanning electron microscope (SEM-EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmissing electron microscope (TEM) analysis methods. SEM-EDX revealed that RuW (95:5) catalyst metal ratio was obtained at desired nominal ratio. XRD characterization revealed that W addittion to the Ru structure increased its activity by forming an alloy. W addition Ru altered the electronic structure of the Ru. Parameters affecting the hydrolysis performance of RuW/MWCNT catalyst such as temperature, amount of catalyst, NaBH4 concentration and sodium hydroxide (NaOH) concentration were investigated. Adding NaOH to the reaction vessel reduced the activity of the RuW/MWCNT catalyst. From the hydrolysis measurements, the activation energy of RuW(95–5)/MWCNT catalyst was found to be 16.327 kjmol−1, the reaction order as 0.61 and the initial rate as 95,841,4 mL H2gcatmin−1. The stability of the RuW/MWCNT catalyst was tested using 5 times and it was observed that this novel RuW/MWCNT catalyst could complete the hydrolysis reaction despite repeated use.

Tuning surface composition of multiwalled carbon nanotubes supported Pt-Co bimetallic nanoparticles for boosting methanol oxidation catalysis

Developing catalysts with high performance and low cost for methanol oxidation reaction (MOR) is the key to promoting the industrialization of direct methanol fuel cells (DMFCs). In this work, multiwalled carbon nanotubes (MWCNTs) supported PtCo alloys catalysts with improved MOR properties and anti-CO poisoning ability are successfully prepared by integrating low temperature adsorption and high temperature reduction method. The Pt1Co3@NC/MWCNTs sample with moderate Co2+ feeding content (0.81 mA/ugPt) achieves a factor of 1.93 enhancement in MOR mass activity compared to the commercial Pt/C catalyst (0.42 mA/ugPt). In addition, the Pt1Co3@NC/MWCNTs sample displays a lower CO oxidation onset potential respect to pristine Pt/C catalyst (0.74 V vs. 0.82 V). Scuh improvement of MOR activity, durability and anti-CO poisoning ability of the Pt1Co3@NC/MWCNTs catalyst is ascribed to the moderate surface compositions, optimal electronic interaction between PtCo alloys and MWCNTs, and the protection of N-doped carbon (NC) shells. This study provides a new direction to decrease the utilization of platinum and improve the MOR activity, stability and anti-CO poisoning ability of electrocatalysts which will be potential in design and fabrication of the highly efficient electrocatalysts for DMFCs applications.

Novel GaPtMnP Alloy Based Anodic Electrocatalyst with Excellent Catalytic Features for Direct Ethanol Fuel Cells

AbstractAlthough considerable effort has been devoted to developing bifunctional electrocatalysts with enhanced atomic utilization in ethanol fuel cells, significant progress in this field has been hindered by notable drawbacks of the electrocatalysts, such as low stability, poor activity, and inefficient repeatability for multiple startup and shutdown cycles. Considering these issues herein, a novel nanosized GaPtMnP alloy anchored on N‐doped multiwall carbon nanotubes (MWCNTs) is developed. The average size of the spherical GaPtMnP alloy nanoparticles is ≈3.5 nm. The atomic structure and d‐band shift of Pt in the GaPtMnP alloy are demonstrated using state‐of‐the‐art density functional theory calculations. Cyclic voltammetry analysis revealed that GaPtMnP/N‐MWCNT delivered high mass and specific activities of 9.16 A mgPt−1 and 10.4 mA cm−2, respectively, in 0.3 m H2SO4 + 0.5 m ethanol, values that are ≈13‐ and 8‐fold higher than the corresponding values for Pt/C. In addition, it exhibits long‐term stability and durability even after 3000 cycles. A single cell based on the GaPtMnP/N‐MWCNT anodic electrocatalyst exhibits a peak power density of 86.64 mW cm−2, which is approximately fourfold higher than that of Pt/C at 70 °C. Furthermore, the performance of a fuel cell comprising the GaPtMnP/N‐MWCNT catalyst remained constant even after multiple startup–shutdown cycles.

Oxidized multiwalled nanotubes as efficient carbocatalyst for the general synthesis of azines

The carbocatalytic synthesis of azines (N-N linked diimines) by mild-oxidized multiwalled carbon nanotubes catalyst (oxMWNT) is presented. The material, just with a 5 %wt. loading, is able to carry out a smooth room-temperature metal-free condensation of aldehydes and hydrazine, without external additives, to obtain a wide library of symmetric and also asymmetric azines in excellent yields, even in gram scale, with an excellent selectivity for aromatic substrates. This methodology allows the synthesis of azines with application in nonlinear optics, and the organic materials and biological active compounds crafting. oxMWNT catalysed the reaction in just 3 h with full recyclability upon the recovery of the catalyst. In addition, due to the inherent oxMWNT oxidative capacity in the presence of nitric acid, we have also developed the one-pot synthesis of azines starting from alcohols.

Palladium nanoparticles supported on multı-walled carbon nanotube (MWCNT) for the catalytic hexavalent chromium reduction

Chromium (VI) is widely accepted as an acute toxic contaminant in living ecosystems, while the trivalent Chromium form (III) is thought to be an important element for living beings. This study showed that zero palladium (Pd0) metal nanoparticles supported onto a multi-walled carbon nanotube (MWCNT) catalyst (Pd@MWCNT) effectively catalyzed the reduction reaction of Chromium (VI) to Chromium (III) using HCOOH (formic acid) as a reducing agent. The catalyst (Pd@MWCNT) was prepared reproducibly in the aqueous mixture at room conditions through the impregnation-reduction technique and identified using some analytical characterization techniques (HRTEM, DR/UV–vis, TEM-EDX, TEM, XPS, ICP-OES, and P-XRD). The results of the characterization studies show that the palladium(0) nanoparticles (demean = 2.20 ± 0.25 nm) are very well dispersed onto the MWCNT support material surface. The stability and activity of catalytic performance of Pd(0) metal nanoparticles were investigated in the reactions of Chromium (VI) to Chromium (III) in HCOOH solution. The results show that the Pd@MWCNT catalyst exhibited excellent activity (TOF = 281 mol Cr2O72−/mol Pd min), even after 5 times of reuse (<86%) in the reduction reaction of Chromium (VI) to Chromium (III) at 298K. In addition, this study includes very rich kinetic data depending on [Pd@MWCNT], [HCOOH], [HCOONa], [Cr2O72−] concentrations and temperature parameters to determine the nature of the reduction rate and activation parameters of Cr(VI) catalyzed by Pd@MWCNT nanocatalyst in the formic acid medium as a reducing agent.

AuPt Nanoparticles/ Multi-Walled carbon nanotubes catalyst as high active and stable oxygen reduction catalyst for Al-Air batteries

A series of AuPt nanoparticles supported on multi-walled carbon nanotubes (AuxPt/MWNTs) catalysts with ultrafine distribution (d ≈ 3.0 nm) were synthesized for Al-air battery cathode to enhance the oxygen reduction reaction. Among them, Au0.67Pt/MWNTs catalyst with metal loading of 10.2 wt% (Au:4.1 wt%, Pt:6.1 wt%) exhibited a superior ORR catalytic activity and competitive durability to 20 wt% Pt/C catalyst. When applied as Al-air battery, appropriate increasing Au loading encourage better battery performance. Au1.68Pt/MWNTs with 8.95 wt% of Au and as little as 5.3 wt% Pt content exhibit larger specific capacity (921 mAh g−1) and power density (146.8 mW cm−2) as well as better durability than 20 wt% Pt/C catalyst when it is assembled as cathode in Al-air battery.

Nanocomposites of Multi-walled Carbon Nanotubes and Titanium dioxide (MWCNTs/TiO2) as affective counter electrode materials for Platinum-free Dye-Sensitized Solar Cells (DSSCs)

Platinum is commonly used as a catalyst to regenerate the redox mediator in Dye-Sensitized Solar Cells (DSSCs). This work intends to replace the expensive and rare platinum with conventional and economical materials. Nanocomposites of Multi-walled Carbon Nanotubes (MWCNTs) and TiO2 can be used as active catalyst materials for the counter-electrode of DSSC. In these composites, MWCNTs provide catalytic properties, and TiO2 acts as a binder. The interaction between MWCNTs and TiO2 has been investigated by Transmission Electron Microscopy (TEM). It has been observed that DSSCs photovoltaic performance significantly depends on the concentration of MWCNTs in nanocomposites. The amount of MWCNTs has been optimized for the best performance of DSSC. The solar cell assembled with 4%MWCNTs catalyst material showed an efficiency of 8.81%, comparable to Pt-based device (9.40%), fabricated under analogous environment.

Magnetite-Based Catalyst in the Catalytic Wet Peroxide Oxidation for Different Aqueous Matrices Spiked with Naproxen–Diclofenac Mixture

Magnetite supported on multiwalled carbon nanotubes catalysts were synthesized by co-precipitation and hydrothermal treatment. The magnetic catalysts were characterized by X-ray diffraction, Fourier-transform infrared spectrometry, thermogravimetric analysis and N2 physisorption. The catalysts were then tested for their ability to remove diclofenac (DCF) and naproxen (NAP) from an aqueous solution at different conditions (pH, temperature, and hydrogen peroxide) to determine the optimum conditions for chemical oxidation. The optimization of the process parameters was conducted using response surface methodology (RSM) coupled with Box–Behnken design (BBD). By RSM–BBD methodology, the optimal parameters (1.75 mM H2O2 dosage, 70 °C and pH 6.5) were determined, and the removal percentages of NAP and DCF were 19 and 54%, respectively. The NAP–DCF degradation by catalytic wet peroxide oxidation (CWPO) was caused by •OH radicals. In CWPO of mixed drug solutions, DCF and NAP showed competitive oxidation. Hydrophobic interactions played an important role during the CWPO process. On the other hand, the magnetic catalyst reduced its activity after the second cycle of reuse. In addition, proof of concept and disinfection tests performed at the operating conditions showed results following the complexity of the water matrices. In this sense, the magnetic catalyst in CWPO has adequate potential to treat water contaminated with NAP–DCF mixtures.