Copper Aluminate Research Articles

Enhanced photodegradation of organic dyes using copper and zinc aluminate nanophotocatalysts

This study aims to enhance the photocatalytic efficiency of CuxZn1-xAl2O4 (x = 0.0, 0.2, 0.4, 0.6, and 0.8) nanophotocatalysts synthesized via a sol-gel self-combustion method. Rietveld analysis confirmed the formation of single-phase spinels with a face-centered cubic structure and Fd-3m space group symmetry, while electron density distribution analysis supported the ionic character of bonding within the material. Subsequent UV–visible spectroscopy revealed that the addition of Cu(II) reduced the band gap from 4.66 eV to 2.54 eV, facilitating enhanced light absorption. Consequently, the catalyst with x = 0.8 deteriorated 95 % of methyl orange (MO) and 93 % of rhodamine-B (RhB) in 120 min of visible light irradiation, following a pseudo-first-order kinetic model. The Cu0.8Zn0.2Al2O4 sample demonstrated significant reusability and stability, with degradation rates of 93–79 % for RhB and 95–81 % for MO after four cycles. Scavenging studies indicated that photoexcited holes (h), hydroxyl radicals (OH•), and superoxide radicals (O₂•⁻) were key factors in the degradation process. This study presents an improved approach for enhancing the photodegradation performance of the Cu0.8Zn0.2Al2O4 catalyst for pharmaceutical and wastewater treatment applications.

Electrochemical and photoluminescence properties of Ce3+ doped copper aluminate nanoparticles

In this communication, for the first of its kind, CuAl2O4 doped with Ce3+ (1-9 mol %) are syn- thesized by solution combustion method using Aloe Vera gel as a reducing agent. The as-formed sample was calcined at 500° C for 3 hours, followed by characterization. The addition of dopants to the copper aluminate matrix didn't alter the crystal structure of the host matrix. Bragg reflec- tions confirm the formation of the cubic phase and also absence of other impurities. The surface morphology consists of nanorods arranged one above the other. The estimated crystallite size was found to decrease from 12 to 9 nm whereas, the direct energy band gap increases from 2.84 to 3.02 eV with an increase in dopant concentration. Under λex = 305 nm excitation, photoluminescence (PL) emission spectra have a high intense peak at 553 nm along with a less intense peak at 472 nm. The peak at 553 nm can be attributed to the existence of oxygen vacancies which arise due to the transition of an electron from the 2D3/2→2F7/2 of Ce3+, however, the peak observed at 472 nm results from the transition of ionized oxygen vacancies (VO) to the valence band caused by the 2D3/2→2F5/2 transition. The CIE coordinates lie well within the green region with 5758 K aver- age CCT. Further, Cyclic voltammetry analysis was conducted to investigate oxidation and redox peaks, while electrochemical impedance spectroscopy provided insights into ion transport kinetics. Specific capacitance values ranging from 29 to 59 F/g were obtained for CuAl2O4:Ce(1-9 mol %) NPs. These findings suggest potential applications for the synthesized material in areas such as display technology as a green nano phosphor and energy storage materials.

Effect of Sm3+ concentration on reddish orange photoluminescence and electrochemical properties of copper aluminate nanoparticles for display and supercapacitor applications

In this report, a novel synthesis method for Sm3+-doped copper aluminate nanoparticles (1–9 mol %) is presented, utilizing Ocimumsanctum leaves extract as a reducing agent through the solution combustion method, followed by calcination at 600 °C for 3 h. The resulting cubic spinel structure, validated by Bragg reflections, demonstrates a decrease in crystallite size and a direct energy band gap correlated with increasing dopant concentration. The morphology exhibits irregularly shaped nanoparticles and hexagonal shaped nanoplates. On deconvolution, three peaks situated at 579, 590 and 600 nm. The emission peak observed at 579 and 590/600 nm can be attributed to transitions from excited level G5/24 to its lower lying levels, H5/26, H7/26 respectively, with noticeable concentration quenching at 7 mol %. CIE and CCT coordinates affirm the red emission of Sm3+ within the host lattice, suggesting potential applications in residential and hospital settings. Cyclic voltammetry analysis provides insights into redox reactions, electrode kinetics, and electrochemical behavior. Electrochemical Impedance Spectroscopy (EIS) elucidates ion transport kinetics, while Galvanostatic Charge–Discharge (GCD) analysis determines supercapacitance values ranging from 53.89 F/g with increasing dopant concentrations. This material exhibits promise for applications in energy storage and display technology.

The spinel-based pliable thermoelectric device for room temperature application

Copper aluminate is a p-type semiconductor material with moderate thermoelectric behavior. In contrast, for the first-time electron-enriched cobalt was introduced as a dopant to accelerate the thermoelectric performance of the spinel CuAl2O4. The spinel phase was confirmed by XRD analysis, and the band agreed with Cu–O–Al bond at 790 cm−1 from FT-IR spectra. SEM and TEM analysis established the morphology of cubic CuAl2O4 and spherical cobalt. Depending on the dopant concentration, the Co2+ ion successfully resided in the position of Cu2+ in the spinel CuAl2O4. From the Tauc plot, a bandgap reduction from 2.1 eV to 1.01 eV was detected, which is accountable for outstanding enhancement in the thermoelectric behavior of the material. We have effectively fabricated the flexible undoped and cobalt-doped Copper aluminate, Cu1-xCoxAl2O4 (x = 0, 0.02, 0.04, 0.06, and 0.08) on the fabric substrate. 8 % (x = 0.08) cobalt doped over copper aluminate were designated the more charge carriers of −6.84 × 1016 cm−3, promoting high electrical conductivity to reach a maximum of 1.02 Scm−1. In particular, the power factor of 114.92 μWm−1K−2 was achieved for Cu0.92Co0.08Al2O4 at 300 K. Our results thus indicate that the cobalt-doped CuAl2O4-coated fabrics are promising semiconducting candidates for flexible wearable thermoelectric applications. The maximum output voltage of 2.4 mV was achieved for the fabricated p-type CuAl2O4 and n-type Cu0.94Co0.06Al2O4 thermoelectric device at ΔT = 2.7 K.

Optical CuAl2O4 used as photocatalyst for IC dye degradation

ABSTRACT The nanocrystalline copper aluminate (CuAl2O4) has been successfully synthesized by a simple, economical, and environmentally friendly solid-state mechanochemical (MCH) method. The prepared sample was characterized by a variety of suitable methods employed, including scanning electron microscopy (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), Fourier transform infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRD). The material's average particle size was 55 nm and stoichiometric. CuAl2O4 has been found to exhibit potent photocatalytic activity toward indigo carmine (IC) when subjected to UV light. Under UV radiation, 10 mg CuAl2O4 leads to 99 ± 1% degradation of an 8 ppm IC dye solution among 2 ppm, 4 ppm, 6 ppm, 8 ppm, and 10 ppm in 25 min. In addition, a prospective liquid chromatography-mass spectrometry (LC-MS) technique is identified in the current work, which provides potential routes for the photocatalytic breakdown of IC. Even after five consecutive cycles, the photocatalyst showed remarkable reusability and stability.

Selective reduction of NO by CO using copper-aluminum oxides from hydrotalcite-type precursors: Study of chemical species and thermal stability

The objective of this work was to analyze the influence of Al on copper catalysts, regarding thermal stability and performance during NO reduction by CO. Two copper-based catalysts were prepared by precipitation and subsequent calcination at 600 °C, with and without aluminum in their composition (CuAl-HT-c and Cu-p). The precursor CuAl-HT was synthesized to obtain a hydrotalcite structure. The catalysts obtained after calcination of the precursors were characterized by N2 physisorption, TPR, N2O titration, in situ XRD and in situ XANES. They showed good catalytic performance, however with Cu-p being the most active but with larger formation of N2O (important greenhouse gas). In this catalyst, the interaction between the adsorbed NO molecules is facilitated, probably due to the higher concentration of Cu+.Regarding the aged catalysts, Cu-p was deactivated due to sintering, which is attributed to the lack of aluminum. CuAl-HT-c-900 had its performance improved during aging, either because the reduction of NO by CO is a structure-sensitive reaction for this catalyst (and the increase in particle size after aging is related to larger activity), or because of the presence of copper aluminate, which can also improve activity and selectivity.

Phosphorescence and Tarnish Resistance Properties of Copper with Strontium Aluminate Addition

The purpose of this research is to examine the effect of strontium aluminate (SrAl2O4) in copper samples on phosphorescence and tarnish resistance properties. The samples were fabricated by powder metallurgy using the compression moulding technique and then sintered in argon atmosphere. Phosphorescence, hardness, microstructure and tarnish resistance were studied. In the process of the compression moulding, the samples contain 100, 90, 80 and 70 percent of copper powder, by weight, with the addition of 0, 10, 20 and 30 percent of strontium aluminate, by weight, respectively. Polyvinyl alcohol (PVA) was used as a binder and mixed with copper and strontium aluminate powder to produce the green specimens using a hydraulic machine. Then, the green samples were sintered at 900 °C for one hour. After sintering, PVA was eliminated and the samples became denser. It was found that the hardness of the sample without strontium aluminate (30.5 HV) is higher than that of the sample with 10% of strontium aluminate addition (12.84 HV). Furthermore, copper samples containing strontium aluminate were fluorescent under ultraviolet at 517 nm. The sample with the largest amount of strontium aluminate (70Cu-30SrAl2O4) has higher phosphorescence than 90Cu-10SrAl2O4. In sulphur atmosphere, the tarnish resistance was found to be improved when strontium aluminate was added into copper. The colour difference (DE*) of 100Cu, which has no strontium aluminate, was 6.42 and higher than that of 90Cu-10SrAl2O4 (DE*= 3.5), 80Cu-20SrAl2O4 (DE*= 1.37), and 70Cu-30SrAl2O4 (DE*= 0.49), when testing in sulphur atmosphere for 30 min. 70Cu-30SrAl2O4, containing the highest amount of strontium aluminate, has the least colour changing on its surface resulting in the resistance in tarnishing.

Nanodiamond (ND)-Based ND@CuAl2O4@Fe3O4 electrochemical sensor for Tofacitinib detection: A unified approach to integrate experimental data with DFT and molecular docking

Tofacitinib (TOF) is gaining recognition as a potent therapeutic agent for a variety of autoimmune disorders, including rheumatoid arthritis and psoriasis. Ensuring precise drug concentration control during treatment necessitates a rapid and sensitive detection method. This study introduces a novel electrochemical sensor employing a composite of nanodiamond (ND), copper aluminate spinel oxide (CuAl2O4), and iron (II, III) oxide (Fe3O4) as modified materials for efficient TOF detection. Extensive analyses using physicochemical and electrochemical techniques were carried out to characterize the morphological, structural, and electrochemical properties of the ND@CuAl2O4@Fe3O4 composite. Thereafter, various voltammetric methods were utilized to evaluate the electrochemical behavior of the ND@CuAl2O4@Fe3O4-modified glassy carbon electrode (GCE) concerning TOF determination. The fabricated electrode showcased superior performance in electrochemical TOF detection in a buffered solution (pH = 5), achieving a remarkably low detection limit of 7.8 nM and a linear response from 0.05 μM to 13.21 μM. Furthermore, applying the modified electrode as an electrochemical sensor exhibited exceptional selectivity, stability, and practicality in determining TOF in pharmaceutical and biological samples. Alongside the sensor development, this study conducted a thorough investigation using Density Functional Theory (DFT) for the geometry optimization of TOF and the TOF-ND complex. Consequently performed molecular docking studies using Janus Kinase 1 (JAK1) (PDB ID: 3EYG) and JAK3 (PDB ID: 3LXK) indicated higher interaction of the TOF-ND conjugate with the JAKs, reflected by binding energies of −12.9 kcal/mol and −11.7 kcal/mol for JAK1 and JAK3 respectively, compared to −7.0 kcal/mol and −6.9 kcal/mol for TOF alone. These findings illustrate the potential of the ND-based ND@CuAl2O4@Fe3O4 composite as a proficient sensing material for TOF detection and the merits of DFT in providing a detailed understanding of the interactions at play. This pioneering research holds promise for real-time TOF monitoring, which will advance personalized treatment strategies and improve therapeutic outcomes for patients with autoimmune disorders.

Enhanced visible-light photocatalytic remediation of atrazine over CuAl2O4-modified BaSnO3 nanoplatelets synthesized by sol-gel route

Photocatalytic remediation of organic pollutants employing semiconducting nanocomposites is a capable, green, and feasible approach. In this work, the photocatalytic mineralization of emerging atrazine herbicide (AtZ) is realized utilizing sol-gel-prepared barium stannate (BaSnO3) nanoplatelets that are impregnated with copper aluminate (CuAl2O4) nanoparticles for the first time. The formed CuAl2O4/BaSnO3 p-n heterojunctions signified mesostructured texture with surface areas of 173–192 m2 g1 and 7.94 nm of pore diameter. The light harvesting in the visible regime is improved thanks to the controllable addition of CuAl2O4 at 15.0–20.0 wt% reducing the bandgap to 2.66 eV. The photocatalytic mineralization of AtZ has been achieved over 2.0 gL1 15% CuAl2O4/BaSnO3 at an initial rate of 20.0 µM min–1 within 40 min. Also, this optimized photocatalyst can be reused five times with 97% of its first-time use. The superb performance of CuAl2O4/BaSnO3 is attributed to the efficient p-n heterojunction formation and improved visible-light harvesting that allows superior charge transfer toward the photooxidation process.

Kinetics study of the selective hydrogenation of furfural to furfuryl alcohol over CuAl2O4 spinel catalyst

The catalytic hydrogenation of furfural is an important process that produce value-added furfural derivatives, especially furfuryl alcohol. In this work, the kinetics of the catalytic furfural hydrogenation over copper aluminate spinel (CuAl2O4) was studied in a batch-type reactor under various reaction parameters including the stirring speed, initial furfural concentration, H2 pressure, and reaction temperature. The CuAl2O4 catalyst showed excellent performance in furfuryl alcohol production as the furfural conversion could reach 100% and the furfuryl alcohol yield was >98%. The furfural concentration and the reaction temperature were found to significantly impact on the reaction rate, while other parameters showed less contributions leading to a flexible operation window. It was determined that the reaction rate expression followed the equation r = kCfurfural0.335 with the apparent activation energy of 44.6 kJ/mol. The developed kinetic model for hydrogenation of furfural to furfuryl alcohol were in good agreement with the experimental results. The kinetic model presented here could be useful for process design and scale-up of the hydrogenation reactor in the industrial application.

Synthesis and visible-light photocatalytic property of spinel CuAl2O4 for vehicle emissions.

Photodegradation of vehicle emissions is a promising approach for dealing with atmospheric pollution in road tunnels. In this research, copper aluminate nanoparticles (CuAl2O4) were prepared by the sol-gel method using copper nitrate, aluminum nitrate, and citric acid as precursor materials. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectroscopy to validate their structure, surface morphology, and optical properties, respectively. The XRD and SEM results confirm that the CuAl2O4 powder has a particle size of 20-37nm and exhibits a spinel-type structure. The upper limit of the stimulation wavelength in the UV-Vis diffuse reflectance spectrum is located at 725nm with a band gap (Eg) of about 1.50eV, which is suitable for effective visible-light degradation. Photocatalytic performance of the CuAl2O4 nanoparticles was analyzed by investigating the effects of light source, calcination temperature, and catalyst loading amount on the degradation of vehicle emissions (CO, HC, and NO). Best results were obtained under fluorescent light irradiation by CuAl2O4 nanoparticles calcined at 700°C. The optimum catalyst amount for decomposing CO, HC, and NO were determined as 0.5g, 0.5g, and 2g, respectively. Overall, the photocatalytic performance study verifies that spinel CuAl2O4 photocatalyst is a valuable material for next-generation technologies aimed at reducing harmful emissions from vehicles.

Co-operative harmless treatment and neutralization utilization process research of LPG spent caustic coupled chloroaluminate ionic liquid spent catalysts

In the petrochemical industry, due to strong acids and toxic heavy metals, chloroaluminate ionic liquid spent catalysts pose a potential environmental risk. Given the strong alkalinity and high pollution load, the treatment step for liquefied petroleum gas (LPG) spent caustic requires adding acid, resulting in significant acid consumption and the risk of secondary pollution. According to the characteristics of these two types of solid waste, the coupling process of LPG spent caustic and chloraluminate ionic liquid waste catalyst is proposed with the goal of resource and harmlessness. The LPG spent caustic and the chloroaluminate ionic liquid spent catalyst are pretreated by precipitation-flocculation and hydrolysis, respectively, after which they are neutralized. The main factors in the pretreatment and neutralization process are systematically examined. Under optimum circumstances, 98 % of the sulfide from LPG spent caustic was removed, 86.8 % of the chemical oxygen requirement was removed, and the oil content in the treated solution was 10 mg/L. The hydrolysis reaction was milder when the hydrolysis media was mixed with the chloroaluminate ionic liquid spent catalyst at a volume ratio of 40:1. By changing the hydrolysis medium, it was confirmed that the neutralizing solution containing sodium chloride had an inhibitory effect on the reaction when reused in the hydrolysis reaction of the spent catalyst. The treated LPG SC and the acidic hydrolysate were neutralized at a volume ratio of 14.8:100.The pH after the reaction was 7, and the recoveries of aluminum and copper ions were 99.99 % and 93.36 %, respectively. The precipitates were calcined at high temperatures, and the characterization of the calcined products confirmed the formation of copper aluminate spinel by XRD, FT-IR, and SEM-EDS. The COD, sulfide, and oil indicators in the neutralization solution meet the tertiary effluent discharge standards of China's National Comprehensive Effluent Discharge Standard (GB 8978-1996). The process eliminates the risk of high sulfide and COD from the LPG SC and recovers the spent catalyst's metal resources. In addition, the whole process has no additional added acid or alkali. A new approach to disposing of these two hazardous wastes (LPG SC and chloroaluminate ionic liquid spent catalysts) for the petrochemical industry is offered.

Red emission of copper aluminate synthesized via chemical and bio-mediated routes.

For the first time, copper aluminate nanoparticles (NPs) are synthesized by a combustion method using urea as a fuel (CAOU) and Ocimum sanctum (tulsi) extract as a reducing agent (CAOT). The Bragg reflections of the as-formed product confirm the formation of a cubic phase with Fd3̄m space group. The crystallite size, crystallinity and other structural parameters are discussed. The surface morphology of CAOU is agglomerated in nature whereas that of CAOT is hexagonal in shape. The smaller crystallite size CAOT NPs show a higher energy band gap. The photoluminescence (PL) analysis excited at 302 nm shows that the CIE coordinates fall in the red region. The oxygen defects are mainly responsible for the PL emission. The CCT coordinates confirm that both CAOU and CAOT NPs can find an application in warm light emitting diodes.

Electrochemical DNA aptamer platform based on CuAlO2/rGO-TEPA@AuPt nanocomposites for dopamine detection

Dopamine (DA) is a neurotransmitter that plays an important role in the central nervous system and has a significant impact on an individual's attention, mood, and cognition. Therefore, real-time monitoring of DA levels could play a key role in the management and treatment of many psychiatric diseases. Herein, we report the development of a sensitive and selective electrochemical aptamer immunosensor for detection of DA. DNA aptamers are used as model protein biomarkers to avoid the effects of interfering substances and to analyze the performance of immunosensors. Copper aluminate (CuAlO2)/reduced graphene oxide-tetraethy lenepentamine (rGO-TEPA) and gold-platinum bimetallic nanoparticles (AuPtNPs) were utilized as modifiers for the sensor fabrication. Notably, rGO-TEPA in the composite was able to induce excess oxygen to CuAlO2, resulting in a strong promotion between CuAlO2 and rGO-TEPA, significantly improving the electron transfer on the immunosensor surface. The bimetallic AuPtNPs would provid more attachment sites for the aptamers, and further improved the sensitivity of the biosensor. Under optimized experimental conditions, the constructed immunosensor was capable of real-time monitoring capabilities within a concentration range of 0.05 nM–10 μM, with a detection limit of 0.017 nM at S/N = 3, highlighting its potential for health management and clinical diagnosis applications.

Influence of layer thickness, defect density, doping concentration, interface defects, work function, working temperature and reflecting coating on lead-free perovskite solar cell

Perovskite-based solar cells have made an impact in the photovoltaic industry by surpassing some of the established solar cell technologies, with power conversion efficiency (PCE) exceeding 23% already. Among them methylammonium lead tri iodide (MAPbI3) based perovskite solar cell (PSC) have been greatly focused upon. However, the toxic nature of lead (Pb) is a major area of concern in its wide spread applications. Nontoxic germanium (Ge) has emerged as an alternate to Pb in PSC due to its similar photovoltaic properties. In this work, numerical modelling of Ge based perovskite solar cell structure (FTO/TiO2/CH3NH3GeI3/Spiro-OMeTAD/Au) is performed using SCAPS software. A systematic approach is followed to investigate the effect of material thickness, doping concentration, work function, temperature, reflection and interface defect densities on the performance of PSC. Initially, all the cell parameters are optimized by keeping defect density constant. Once, the optimized structure is achieved the defect density is varied to investigate its effect on the cell performance. Finally, all the cell parameters are optimized at each defect density. Based on optimized simulation results, PCE of 17.74% is achieved with 15.77 mA/cm2 short-circuit current (JSC), 1.26 V open circuit voltage (VOC) and 88.64% fill factor (FF). Moreover, in the optimized cell structure Spiro-OMeTAD and gold (Au) are replaced with different copper (Cu) based hole transport layer (HTL) and anode materials respectively to study its effect on the cell performance. The best result is obtained with copper antimony sulfide (CuSbS2) and Copper Aluminate (CuAIO2) exhibiting PCE of 21.42% and 23.56% respectively.

Steam reforming of methanol over mesoporous Cu–Al spinel catalysts synthesized by mechanochemical method

Hydrogen production for fuel cells via on-board steam reforming of methanol is a promising approach. In this study, an ammonium carbonate-assisted mechanochemical procedure has been developed for Cu-based catalyst synthesis for SRM. Catalytic performance in SRM was evaluated in a fixed bed reactor at varied conditions, and physical and structure properties of the catalysts were characterized by N2 adsorption-desorption, N2O titration, SEM, H2-TPR, XRD and TG, etc. Mechanical milled samples exhibited a porous structure that differed from that of the catalyst prepared by conventional impregnation. The SRM activity was enhanced for the strong interaction between copper ions and the copper aluminate formed on the ball-milled catalysts. Cu1Zn3Al6 exhibited the worst in activity, which could be ascribed to the poor metal dispersion. Cu–Al spinel in the catalysts plays an important role in the catalytic stability, which has prevented Cu from quick sintering in SRM, and the ball-milled catalysts have exhibited a slight deactivation with the time-on-stream of 25 ​h.

Synthesis of CuAl2O4 Nanoparticle and Its Conversion to CuO Nanorods

The molten salt approach was used to convert CuAl2O4 nanoparticles to CuO nanorods in this study. Molten hydroxide (NaOH) synthesis was chosen over molten salts (NaCl/KCl) for removing aluminium oxide from copper aluminate at low temperatures. The molten salt process is environmentally beneficial. Polymeric precursors were used to make nanosized copper aluminates. Alginic acid polymer is used to gel aqueous solutions of copper acetate and aluminium nitrate, yielding precursor after further heating. The precursor provides 14 nm nanosized copper aluminates after being heated at 900°C for 5 hours. XRD, FTIR, SEM, and TEM were used to characterize the nanosized copper aluminate powder. Solid state mixing and solution technique were used to investigate molten hydroxide treatment of spinel CuAl2O4. The products of the reaction were identified using XRD. FTIR and SEM are also used to analyze the sample. Using UV-DRS absorbance spectrum analysis, the optical characteristics of CuAl2O4 and CuO nanorods were examined. Using the Tauc plot method, the band gaps of CuAl2O4 and CuO were calculated to be 4.3 and 3.93 eV.

Research of New Thermoelectric Materials Based on Multicomponent Semiconductor Compounds

This paper presents the results of studies of new thermoelectric materials, obtained on the basis of multicomponent semiconductor compounds with a crystal structure of chalcopyrite and delafossite, by methods of nuclear magnetic resonance in a local field (63.65Cu NMR) and nuclear quadrupole resonance (63.65Cu NQR). The values of local magnetic fields at the location of the resonant copper nuclei and the parameters of nuclear quadrupole interactions in chalcopyrite (CuFeS2) and copper aluminate (CuAlO2) are determined. The search for new thermoelectric materials is caused by the low operating efficiency of industrial thermoelectric converters based on bismuth and lead tellurides, which have been used for half a century.

Simultaneous Oxidation and Sequestration of Arsenic(III) from Aqueous Solution by Copper Aluminate with Peroxymonosulfate: A Fast and Efficient Heterogeneous Process.

The major problem in arsenic (As(III)) removal using adsorbents is that the method is time-consuming and inefficient owing to the fact that most of the adsorbents are more effective for As(V). Herein, we report a new discovery regarding the significant simultaneous oxidation and sequestration of As(III) by a heterogeneous catalytic process of copper aluminate (CuAl2O4) coupled with peroxymonosulfate (PMS). Oxidation and adsorption promote each other. With the help of the active radicals, the As(III) removal efficiency can be increased from 59.4 to 99.2% in the presence of low concentrations of PMS (50 μM) and CuAl2O4 (300 mg/L) in solution. CuAl2O4/PMS can work effectively in a wide pH range (3.0–9.0). Other substances, such as nitrate, sulfate, chloride, carbonate, and humic acid, exert an insignificant effect on As(III) removal. Based on X-ray photoelectron spectroscopy (XPS) analysis, the exposed reductive copper active sites might drive the redox reaction of Cu(II)/Cu(I), which plays a key role in the decomposition of PMS and the oxidation of As(III). The exhausted CuAl2O4 could be refreshed for cycling runs with insignificant capacity loss by the combined regeneration strategy because of the stable spinel structure. According to all results, the CuAl2O4/PMS with favorable oxidation ability and stability could be employed as a promising candidate in real As(III)-contaminated groundwater treatment.

Manganese containing copper aluminate catalysts: Genesis of structures and active sites for hydrogenation of aldehydes

Copper aluminate spinel (CuO.CuAl2O4) is the favoured Cr-free substitute for the copper chromite catalyst (CuO.CuCr2O4) in the industrial hydrogenation of aldehydes. New insights in the catalytic mechanism were obtained by systematically studying the structure and activity of these catalysts including effects of manganese as a catalyst component. The hydrogenation of butyraldehyde to butanol was studied as a model reaction and the active structure was characterised using X-ray diffraction, temperature programmed reduction, N2O chemisorption, EXAFS and XANES, including in-situ investigations. The active catalyst is a reduced spinel lattice that is stabilised by protons, with copper metal nanoparticles grown upon its surface. Incorporation of Mn into the spinel lattice has a profound effect on the spinel structure. Mn stabilises the spinel towards reduction of CuII to Cu0 by occupation of tetrahedral sites with Mn cations, but also causes decreased catalytic activity. Structural data, combined with the effect on catalysis, indicate a predominantly interface-based reaction mechanism, involving both the spinel and copper nanoparticle surface in protonation and reduction of the aldehyde. The electron reservoir of the metallic copper particles is regenerated by the dissociative adsorption and oxidation of H2 on the metal surface. The generated protons are stored in the spinel phase, acting as proton reservoir. Cu(I) species located within the spinel and identified by XANES are probably not involved in the catalytic cycle.