Ultrasound assisted extraction of Maxilon Red GRL dye from water samples using cobalt ferrite nanoparticles loaded on activated carbon as sorbent: Optimization and modeling

In this research, a selective, simple and rapid ultrasound assisted dispersive solid-phase micro-microextraction (UA-DSPME) was developed using cobalt ferrite nanoparticles loaded on activated carbon (CoFe₂O₄-NPs-AC) as an efficient sorbent for the preconcentration and determination of Maxilon Red GRL (MR-GRL) dye. The properties of sorbent are characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Vibrating sample magnetometers (VSM), Fourier transform infrared spectroscopy (FTIR), Particle size distribution (PSD) and Scanning Electron Microscope (SEM) techniques. The factors affecting on the determination of MR-GRL dye were investigated and optimized by central composite design (CCD) and artificial neural networks based on genetic algorithm (ANN-GA). CCD and ANN-GA were used for optimization. Using ANN-GA, optimum conditions were set at 6.70, 1.2 mg, 5.5 min and 174 μL for pH, sorbent amount, sonication time and volume of eluent, respectively. Under the optimized conditions obtained from ANN-GA, the method exhibited a linear dynamic range of 30–3000 ng mL⁻¹ with a detection limit of 5.70 ng mL⁻¹. The preconcentration factor and enrichment factor were 57.47 and 93.54, respectively with relative standard deviations (RSDs) less than 4.0% (N = 6). The interference effect of some ions and dyes was also investigated and the results show a good selectivity for this method. Finally, the method was successfully applied to the preconcentration and determination of Maxilon Red GRL in water and wastewater samples.     

Rapid ultrasound-assisted magnetic microextraction of gallic acid from urine,plasma and water samples by HKUST-1-MOF-Fe3O4-GA-MIP-NPs: UV–vis detection and optimization study

Magnetite (Fe₃O₄ nanoparticles (NPs)) HKUST-1 metal organic framework (MOF) composite as a support was used for surface imprinting of gallic acid imprinted polymer (HKUST-1-MOF-Fe₃O₄-GA-MIP) using vinyltrimethoxysilane (VTMOS) as the cross-linker. Subsequently, HKUST-1-MOF-Fe₃O₄-NPs-GA-MIP characterized by FT-IR, XRD and FE-SEM analysis and applied for fast and selective and sensitive ultrasound assisted dispersive magnetic solid phase microextraction of gallic acid (GA) by UV–Vis (UA-DMSPME-UV-Vis) detection method. Plackett–Burman design (PBD) and central composite design (CCD) according to desirability function (DF) indicate the significant variables among the extraction factors vortex (mixing) time (min), sonication time (min), temperature (°C), eluent volume (L), pH and HKUST-1-MOF-Fe₃O₄-NPs-GA-MIP mass (mg) and their contribution on the response. Optimum conditions and values correspond to pH, HKUST-1-MOF-Fe₃O₄-NPs-GA-MIP mass, sonication time and the eluent volume were set as follow 3.0, 1.6 mg, 4.0 min and 180 μL, respectively. The average recovery (ER%) of GA was 98.13% with desirability of 0.997, while the present method has best operational performance like wide linear range 8–6000 ng mL⁻¹ with a Limit of detection (LOD) of 1.377 ng mL⁻¹, limit of quantification (LOQ) 4.591 ng mL⁻¹ and precision (<3.50% RSD). The recovery of GA in urine, human plasma and water samples within the range of 92.3–100.6% that strongly support high applicability of present method for real samples analysis, which candidate this method as promise for further application.     

Fe3O4/hydroxyapatite/graphene quantum dots as a novel nano-sorbent for preconcentration of copper residue in Thai food ingredients: Optimization of ultrasound-assisted magnetic solid phase extraction

Fe₃O₄/hydroxyapatite/graphene quantum dots (Fe₃O₄/HAP/GQDs) nanocomposite was synthesized and used as a novel magnetic adsorbent. This nanocomposite was characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetization property. The Fe₃O₄/HAP/GQDs was applied to pre-concentrate copper residues in Thai food ingredients (so-called “Tom Yum Kung”) prior to determination by inductively coupled plasma-atomic emission spectrometry. Based on ultrasound-assisted extraction optimization, various parameters affecting the magnetic solid-phase extraction, such as solution pH, amount of magnetic nanoparticles, adsorption and desorption time, and type of elution solvent and its concentration were evaluated. Under optimal conditions, the linear range was 0.05–1500 ng mL⁻¹ (R² > 0.999), limit of detection was 0.58 ng mL⁻¹, and limit of quantification was 1.94 ng mL⁻¹. The precision, expressed as the relative standard deviation of the calibration curve slope (n = 5), for intra-day and inter-day analyses was 0.87% and 4.47%, respectively. The recovery study of Cu for real samples was ranged between 83.5% and 104.8%. This approach gave the enrichment factor of 39.2, which guarantees trace analysis of Cu residues. Therefore, Fe₃O₄/HAP/GQDs can be a potential and suitable candidate for the pre-concentration and separation of Cu from food samples. It can easily be reused after treatment with deionized water.     

Ultrasonic assisted dispersive solid-phase microextraction of Eriochrome Cyanine R from water sample on ultrasonically synthesized lead (II) dioxide nanoparticles loaded on activated carbon: Experimental design methodology

The present research focus on designing an appropriate dispersive solid-phase microextraction (UA-DSPME) for preconcentration and determination of Eriochrome Cyanine R (ECR) in aqueous solutions with aid of sonication using lead (II) dioxide nanoparticles loaded on activated carbon (PbO-NPs-AC). This material was fully identified with XRD and SEM. Influence of pH, amounts of sorbent, type and volume of eluent, and sonication time on response properties were investigated and optimized by central composite design (CCD) combined with surface response methodology using STATISTICA. Among different solvents, dimethyl sulfoxide (DMSO) was selected as an efficient eluent, which its combination by present nanoparticles and application of ultrasound waves led to enhancement in mass transfer. The predicted maximum extraction (100%) under the optimum conditions of the process variables viz. pH 4.5, eluent 200 μL, adsorbent dosage 2.5 mg and 5 min sonication was close to the experimental value (99.50%). at optimum conditions some experimental features like wide 5–2000 ng mL⁻¹ ECR, low detection limit (0.43 ng mL⁻¹, S/N = 3:1) and good repeatability and reproducibility (relative standard deviation, <5.5%, n = 12) indicate versatility in successful applicability of present method for real sample analysis. Investigation of accuracy by spiking known concentration of ECR over 200–600 ng mL⁻¹ gave mean recoveries from 94.850% to 101.42% under optimal conditions. The procedure was also applied for the pre-concentration and subsequent determination of ECR in tap and waste waters.     

Optimization of ultrasound-assisted dispersive solid-phase microextraction based on nanoparticles followed by spectrophotometry for the simultaneous determination of dyes using experimental design

A simple, low cost and ultrasensitive method for the simultaneous preconcentration and determination of trace amount of auramine-O and malachite green in aqueous media following accumulation on novel and lower toxicity nanomaterials by ultrasound-assisted dispersive solid phase micro-extraction (UA-DSPME) procedure combined with spectrophotometric has been described. The Mn doped ZnS nanoparticles loaded on activated carbon were characterized by Field emission scanning electron microscopy (FE-SEM), particle size distribution, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analyses and subsequently were used as green and efficient material for dyes accumulation. Contribution of experimental variables such as ultrasonic time, ultrasonic temperature, adsorbent mass, vortex time, ionic strength, pH and elution volume were optimized through experimental design, and while the preconcentrated analytes were efficiently eluted by acetone. Preliminary Plackett–Burman design was applied for selection of most significant factors and giving useful information about their main and interaction part of significant variables like ultrasonic time, adsorbent mass, elution volume and pH were obtained by central composite design combined with response surface analysis and optimum experimental conditions was set at pH of 8.0, 1.2 mg of adsorbent, 150 μL eluent and 3.7 min sonication. Under optimized conditions, the average recoveries (five replicates) for two dyes (spiked at 500.0 ng mL⁻¹) changes in the range of 92.80–97.70% with acceptable RSD% less than 4.0% over a linear range of 3.0–5000.0 ng mL⁻¹ for the AO and MG in water samples with regression coefficients (R²) of 0.9975 and 0.9977, respectively. Acceptable limits of detection of 0.91 and 0.61 ng mL⁻¹ for AO and MG, respectively and high accuracy and repeatability are unique advantages of present method to improve the figures of merit for their accurate determination at trace level in complicated materials.     

Novel synthesis of nanocomposite for the extraction of Sildenafil Citrate (Viagra) from water and urine samples: Process screening and optimization

A sensitive analytical method is investigated to concentrate and determine trace level of Sildenafil Citrate (SLC) present in water and urine samples. The method is based on a sample treatment using dispersive solid-phase micro-extraction (DSPME) with laboratory-made Mn@ CuS/ZnS nanocomposite loaded on activated carbon (Mn@ CuS/ZnS-NCs-AC) as a sorbent for the target analyte. The efficiency was enhanced by ultrasound-assisted (UA) with dispersive nanocomposite solid-phase micro-extraction (UA-DNSPME). Four significant variables affecting SLC recovery like; pH, eluent volume, sonication time and adsorbent mass were selected by the Plackett-Burman design (PBD) experiments. These selected factors were optimized by the central composite design (CCD) to maximize extraction of SLC. The results exhibited that the optimum conditions for maximizing extraction of SLC were 6.0 pH, 300 μL eluent (acetonitrile) volume, 10 mg of adsorbent and 6 min sonication time. Under optimized conditions, virtuous linearity of SLC was ranged from 30 to 4000 ng mL⁻¹ with R² of 0.99. The limit of detection (LOD) was 2.50 ng mL⁻¹ and the recoveries at two spiked levels were ranged from 97.37 to 103.21% with the relative standard deviation (RSD) less than 4.50% (n = 15). The enhancement factor (EF) was 81.91. The results show that the combination UAE with DNSPME is a suitable method for the determination of SLC in water and urine samples.     

Ultrasound assisted combined molecularly imprinted polymer for selective extraction of nicotinamide in human urine and milk samples: Spectrophotometric determination and optimization study

Ultrasound-assisted dispersive solid phase microextraction followed by UV–vis spectrophotometer (UA-DSPME-UV–vis) was designed for extraction and preconcentration of nicotinamide (vitamin B₃) by HKUST-1 metal organic framework (MOF) based molecularly imprinted polymer (MIP). This new material was characterized by FTIR and FE-SEM techniques. The preliminary Plackett–Burman design was used for screening and subsequently the central composite design justifies significant terms and possible construction of mathematical equation which give the individual and cooperative contribution of variables like HKUST-1-MOF-NA-MIP mass, sonication time, temperature, eluent volume, pH and vortex time. Accordingly the optimum condition was set as: 2.0 mg HKUST-1-MOF-NA-MIP, 200 μL eluent and 5.0 min sonication time in center points other variables were determined as the best conditions to reach the maximum recovery of the analyte. The UA-DSPME-UV–vis method performances like excellent linearity (LR), limits of detection (LOD), limits of quantification of 10–5000 μg L⁻¹ with R² of 0.99, LOD (1.96 ng mL⁻¹), LOQ (6.53 μg L⁻¹), respectively show successful and accurate applicability of the present method for monitoring analytes with within- and between-day precision of 0.96–3.38%. The average absolute recoveries of the nicotinamide extracted from the urine, milk and water samples were 95.85–101.27%.     

Application of modificated magnetic nanomaterial for optimization of ultrasound-enhanced removal of Pb2+ ions from aqueous solution under experimental design: Investigation of kinetic and isotherm

Magnetic γ-Fe₂O₃ nanoparticles modificated by bis(5-bromosalicylidene)-1,3-propandiamine (M-γ-Fe₂O₃-NPs-BBSPN) and characterized by field emission scanning electron microscopy (FE-SEM), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). This modified compound as novel adsorbent was applied for the ultrasound-assisted removal of Pb²⁺ ion in combination with flame atomic absorption spectroscopy (FAAS). The influences of the effective parameters including initial Pb²⁺ ion concentration, pH, adsorbent mass and ultrasound time were optimized by central composite design (CCD). Maximum removal percentage of Pb²⁺ ion which obtained at 25 mg L⁻¹ of Pb²⁺, 25 mg of adsorbent and 4 min mixing with sonication at pH 6.0. The precision of the equation obtained by CCD was confirmed by the analysis of variance and calculation of correlation coefficient relating the predicted and the experimental values of removal percentage of Pb²⁺ ion. The kinetic and isotherm of ultrasound-assisted removal of Pb²⁺ ion was well described by second-order kinetic and Langmuir isotherm model with maximum adsorption capacity of 163.57 mg g⁻¹.     

Comparative study on ultrasonic assisted adsorption of dyes from single system onto Fe3O4 magnetite nanoparticles loaded on activated carbon: Experimental design methodology

The present study the ultrasound assisted adsorption of dyes in single system onto Fe₃O₄ magnetite nanoparticles loaded on activated carbon (Fe₃O₄-MNPs-AC) was described following characterization and identification of this adsorbent by conventional techniques likes field emission scanning electron microscopy, transmission electron microscopy, particle-size distribution, X-ray diffraction and Fourier transform infrared spectroscopy. A central composite design in conjunction with a response surface methodology according to f-test and t-test for recognition and judgment about significant term led to construction of quadratic model which represent relation among responses and effective terms. This model has unique ability to predict adsorption data behavior over a large space around central and optimum point. Accordingly Optimum conditions for well and quantitative removal of present dyes was obtained best operation and conditions: initial SY, MB and EB dyes concentration of 15, 15 and 25 mg L⁻¹, 4.0, 6.0 and 5.0 of pH, 360, 360 and 240 s sonication time and 0.04, 0.03 and 0.032 g of Fe₃O₄-MNPs-AC. Replication of similar experiment (N = 5) guide that average removal percentage of SY, MB and EB were found to be 96.63 ± 2.86%, 98.12 ± 1.67% and 99.65 ± 1.21% respectively. Good agreement and closeness of Predicted and experimental result and high adsorption capacity of dyes in short time strongly confirm high suitability of present method for waste water treatment, while easy separation of present nanoparticle and its good regeneration all support good applicability of Fe₃O₄-MNPs-AC for waste water treatment. The kinetic study can be represented by combination of pseudo second-order and intraparticle diffusion. The obtained maximum adsorption capacities correspond to Langmuir as best model for representation of experimental data correspond to dyes adsorption onto Fe₃O₄-MNPs-AC were 76.37, 78.76 and 102.00 mg g⁻¹ for SY, MB and EB, respectively. In addition, the performance comparison of ultrasound-assisted, magnetic stirrer assisted and vortex assisted adsorption methods demonstrates that ultrasound is an effective and good choice for facilitation of adsorption process via. Compromise of simple and facile diffusion.     

Synthesis of nanocomposites of iron oxide/gold (Fe3O4/Au) loaded on activated carbon and their application in water treatment by using sonochemistry: Optimization study

This paper focuses on the finding best operational conditions using response surface methodology (RSM) for Rhodamine123 (R123) and Disulfine blue (DSB) dyes removal by ultrasound assisted adsorption onto Au-Fe₃O₄ nanoparticles loaded on activated carbon (Au-Fe₃O₄ NPs-AC). The influences of variables such as initial R123 (X₁) and DSB concentration (X₂), pH (X₃), adsorbent mass (X₄) and sonication time (X₅) on their removal were investigated by small central composite design (CCD) under response surface methodology. The significant variables and the possible interactions among variables were investigated and estimated accordingly. The best conditions were set as: 4 min, 4.0, 0.025 g, 13.5 and 26.5 mg L⁻¹ for sonication time, pH, adsorbent weight, initial R123 and DSB concentration, respectively. At above conditions, the adsorption equilibrium and kinetic follow the Langmuir isotherm and pseudo-second-order kinetic model, respectively. The maximum monolayer capacity (Q_max) of 71.46 and 76.38 mg g⁻¹ for R123 and DSB show sufficiency of model for well presentation of experimental data.     

Dispersion of hydrophobic magnetic nanoparticles using ultarsonic-assisted in combination with coacervative microextraction for the simultaneous preconcentration and determination of tricyclic antidepressant drugs in biological fluids

A two-step sample preparation technique based on dispersive micro solid-phase extraction combined with coacervative microextraction is presented for preconcentration and determination of tricyclic antidepressant drugs in biological samples. An important feature of the method is the application of hydrophobic magnetic nanoparticles, which in combination with coacervative microextraction method enables development of rapid and efficient extraction procedure in order to achievement of a high extraction efficiency. Simultaneous optimization by experimental design lead to improvement of method with low cost which supply useful information about interaction among variables. Under the optimized conditions, a linear range of 5–1000 ng mL⁻¹ with detection limits from 0.51 to 1.4 ng mL⁻¹ were obtained for target analytes. The method was successfully used for the determination of analytes in biological fluids (plasma and urine) with relative recoveries in the range of 89–105% (RSDs < 3.5%).     

Ultrasound-promoted dispersive micro solid-phase extraction of trace anti-hypertensive drugs from biological matrices using a sonochemically synthesized conductive polymer nanocomposite

In this work, a rapid and efficient procedure named ultrasound meliorated dispersive micro solid-phase extraction followed by high performance liquid chromatography-ultra violet detection (US-D-μSPE-HPLC-UV) was developed for the pre-concentration of the main trace anti-hypertensive drugs in complex matrices. The basis of this procedure was a polypyrrole-sodium dodecylbenzenesulfonate/zinc oxide (PPy-DBSNa/ZnO) nanocomposite. It was readily synthesized by the impressive way of in situ sonochemical oxidative polymerization in the presence of some additives such as FeCl₃ and DBSNa, ultimately leading to the effective coating of PPy on the ZnO nanoparticle cores. Characterization of the proposed nanosorbent was performed by different techniques such as FESEM, XRD,EDX, and TGA, confirming the high quality and proper physico-chemical properties of the proposed sorbent. In order to better investigate the input variables, the central composite design (CCD) combined with the desirability function (DF) was utilized. The enriched optimum conditions consisted of the initial pH value of 11.8, 15 mg of the PPy-DBSNa/ZnO nanocomposite, a sonication time of 4.6 min, and 100 μL of methanol, resulting in maximum responses at a relatively low extraction time with a logical DF. Under the optimum conditions, good linearity (5–5000, 2.5–3500, and 2.5–3000 ng mL⁻¹ for metoprolol, propranolol, and carvedilol, respectively, with the correlation of determinations (R²s) higher than 0.99), low limits of detection (LODs) (0.8–1.5 ng mL⁻¹), proper repeatabilities (relative standard deviation values (RSDs) below 6.3%, n = 3), reasonable enrichment factors (EFs) (60–72), and good extraction recoveries (ERs) (higher than %75) were obtainable. These appropriate validations corroborated a good effectiveness of ultrasonic waves in the achievement of a supreme solid phase as well as a facile and efficient microextraction of the low therapeutic concentrations in human plasma and urine samples.     

Synthesis of magnetic γ-Fe2O3-based nanomaterial for ultrasonic assisted dyes adsorption: Modeling and optimization

γ-Fe₂O₃ nanoparticles were synthesized and loaded on activated carbon. The prepared nanomaterial was characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The γ-Fe₂O₃ nanoparticle-loaded activated carbon (γ-Fe₂O₃-NPs-AC) was used as novel adsorbent for the ultrasonic-assisted removal of methylene blue (MB) and malachite green (MG). Response surface methodology and artificial neural network were applied to model and optimize the adsorption of the MB and MG in their individual and binary solutions followed by the investigation on adsorption isotherm and kinetics. The individual effects of parameters such as pH, mass of adsorbent, ultrasonication time as well as MB and MG concentrations in addition to the effects of their possible interactions on the adsorption process were investigated. The numerical optimization revealed that the optimum adsorption (>99.5% for each dye) is obtained at 0.02 g, 15 mg L⁻¹, 4 min and 7.0 corresponding to the adsorbent mass, each dye concentration, sonication time and pH, respectively. The Freundlich, Langmuir, Temkin and Dubinin–Radushkevich isotherms were studied. The Langmuir was found to be most applicable isotherm which predicted maximum monolayer adsorption capacities of 195.55 and 207.04 mg g⁻¹ for the adsorption of MB and MG, respectively. The pseudo-second order model was found to be applicable for the adsorption kinetics. Blank experiments (without any adsorbent) were run to investigate the possible degradation of the dyes studied in presence of ultrasonication. No dyes degradation was observed.     

Sono-assisted preparation of highly-efficient peroxidase-like Fe3O4 magnetic nanoparticles for catalytic removal of organic pollutants with H2O2

Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) with much improved peroxidase-like activity were successfully prepared through an advanced reverse co-precipitation method under the assistance of ultrasound irradiation. The characterizations with XRD, BET and SEM indicated that the ultrasound irradiation in the preparation induced the production of Fe₃O₄ MNPs possessing smaller particle sizes (16.5 nm), greater BET surface area (82.5 m² g^?1) and much higher dispersibility in water. The particle sizes, BET surface area, chemical composition and then catalytic property of the Fe₃O₄ MNPs could be tailored by adjusting the initial concentration of ammonia water and the molar ratio of Fe²⁺/Fe³⁺ during the preparation process. The H₂O₂-activating ability of Fe₃O₄ MNPs was evaluated by using Rhodamine B (RhB) as a model compound of organic pollutants to be degraded. At pH 5.4 and temperature 40 °C, the sonochemically synthesized Fe₃O₄ MNPs were observed to be able to activate H₂O₂ and remove ca. 90% of RhB (0.02 mmol L^?1) in 60 min with a apparent rate constant of 0.034 min^?1 for the RhB degradation, being 12.6 folds of that (0.0027 min^?1) over the Fe₃O₄ MNPs prepared via a conventional reverse co-precipitation method. The mechanisms of the peroxidase-like catalysis with Fe₃O₄ MNPs were discussed to develop more efficient novel catalysts.     

Phase stability and oxygen non-stoichiometry of SrCo0.8Fe0.2O3−δ measured by in situ neutron diffraction

The phase stability, oxygen stoichiometry and expansion properties of SrCo_0.8Fe_0.2O_3−δ (SCF) were determined by in situ neutron diffraction between 873 and 1173 K and oxygen partial pressures of 5 × 10^− 4 to 1 atm. At a pO₂ of 1 atm, SCF adopts a cubic perovskite structure, space group Pm3¯m, across the whole temperature range investigated. At a pO₂ of 10^− 1 atm, a two-phase region exists below 922 K, where the cubic perovskite phase coexists with a vacancy ordered brownmillerite phase, Sr₂Co_1.6Fe_0.4O₅, space group Icmm. A pure brownmillerite phase is present at pO₂ of 10^− 2 and 5 × 10^− 4 atm below 1020 K. Above 1020 K, the brownmillerite phase transforms to cubic perovskite through a two-phase region with no brownmillerite structure observed above 1064 K. Large distortion of the BO₆ (B = Co, Fe) octahedra is present in the brownmillerite structure with apical bond lengths of 2.2974(4) Å and equatorial bond lengths of 1.9737(3) Å at 1021 K and a pO₂ of 10^− 2 atm. SCF is highly oxygen deficient with a maximum oxygen stoichiometry, 3 − δ, measured in this study of 2.58(2) at 873 K and a pO₂ of 1 atm and a minimum of 2.33(2) at 1173 K and a pO₂ of 5 × 10^− 4 atm. Significant differences in lattice volume and expansion behavior between the brownmillerite and cubic perovskite phases suggest potential difficulties in thermal cycling of SrCo_0.8Fe_0.2O_3−δ membranes.     

High surface area monodispersed Fe3O4 nanoparticles alone and on physical exfoliated graphite for improved supercapacitors

Highly conductive, unsophisticated and easy to be obtained physical exfoliated graphite (PHG) supporting well dispersed magnetite, Fe₃O₄/PHG nanocomposite, has been prepared by a one-step chemical strategy and physico-chemical characterized. The nanocomposite, favoured by the a-polar nanoparticles (NPs) capping, results in a self-assembled monolayer of monodispersed Fe₃O₄, covering perfectly the hydrophobic surfaces of PHG. The nanocomposite as an electrode material was fabricated into a supercapacitor and characterized by cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. It shows, after a suitable annealing, significant electrochemical properties (capacitance value of 787 F/g at 0.5 A g⁻¹ and a Fe₃O₄/PHG weight ratio of 0.31) and good cycling stability (retention 91% after 30,000 cycles). Highly monodispersed very fine Fe₃O₄ NPs, covered by organic chains, have been also synthesized. The high surface area Fe₃O₄ NPs, after washing to leave a low content of organic chains able to avoid aggregation without excessively affecting the electrical properties of the material, exhibit remarkable pseudocapacitive activities, including the highest specific capacitance over reported for Fe₃O₄ (300 F/g at 0.5 A g⁻¹).     

Ultrasonic assisted-Fenton-like degradation of nitrobenzene at neutral pH using nanosized oxides of Fe and Cu

Ultrasonic-assisted heterogeneous Fenton reaction was used for degradation of nitrobenzene (NB) at neutral pH conditions. Nano-sized oxides of α-Fe₂O₃ and CuO were prepared, characterized and tested in degradation of NB (10 mg L⁻¹) under sonication of 20 kHz at 25 °C. Complete degradation of NB was effected at pH 7 in presence of 10 mM H₂O₂ after 10 min of sonication in presence of α-Fe₂O₃ (1.0 g L⁻¹), (k = 0.58 min⁻¹) and after 25 min in case of CuO (k = 0.126 min⁻¹). α-Fe₂O₃ showed also effective degradation under the conditions of 0.1 g L⁻¹ oxide and 5.0 mM of H₂O₂, even though with a lower rate constant (0.346 min⁻¹). Sonication plays a major role in enhancing the production of hydroxyl radicals in presence of solid oxides. Hydroxyl radicals-degradation pathway is suggested and adopted to explain the differences noted in rate constants recorded on using different oxides.     

Screening and optimization of highly effective ultrasound-assisted simultaneous adsorption of cationic dyes onto Mn-doped Fe3O4-nanoparticle-loaded activated carbon

The ultrasound-assisted simultaneous adsorption of brilliant green (BG) and malachite green (MG) onto Mn-doped Fe₃O₄ nanoparticle-loaded activated carbon (Mn-Fe₃O₄-NP-AC) as a novel adsorbent was investigated and analyzed using first derivative spectrophotometry. The adsorbent was characterized using FT-IR, FE-SEM, EDX and XRD. Plackett–Burman design was applied to reduce the total number of experiments and to optimize the ultrasound-assisted simultaneous adsorption procedure, where pH, adsorbent mass and sonication time (among six tested variables) were identified as the most significant factors. The effects of significant variables were further evaluated by a central composite design under response surface methodology. The significance of independent variables and their interactions was investigated by means of the analysis of variance (ANOVA) within 95% confidence level together with Pareto chart. Using this statistical tool, the optimized ultrasound-assisted simultaneous removal of basic dyes was obtained at 7.0, 0.02 g, 3 min for pH, adsorbent mass, and ultrasonication time, respectively. The maximum values of BG and MG uptake under these experimental conditions were found to be 99.50 and 99.00%, respectively. The adsorption process was found to be followed by the Langmuir isotherm and pseudo-second order model using equilibrium and kinetic studies, respectively. According to Langmuir isotherm model, the maximum adsorption capacities of the adsorbent were obtained to be 101.215 and 87.566 mg g⁻¹ for MG and BG, respectively. The value of apparent energy of adsorption obtained from non-linear Dubinin–Radushkevich model (4.348 and 4.337 kJ mol⁻¹ for MG and BG, respectively) suggested the physical adsorption of the dyes. The studies on the well regenerability of the adsorbent in addition to its high adsorption capacity make it promising for such adsorption applications.     

Advanced oxidation of Reactive Blue 181 solution: A comparison between Fenton and Sono-Fenton Process

In this work, the decolorization of C.I. Reactive Blue 181 (RB181), an anthraquinone dye, by Ultrasound and Fe²⁺ H₂O₂ processes was investigated. The effects of operating parameters, such as Fe²⁺ dosage, H₂O₂ dosage, pH value, reaction time and temperature were examined. Process optimisation [pH, ferrous ion (Fe²⁺), hydrogen peroxide (H₂O₂), and reaction time], kinetic studies and their comparison were carried out for both of the processes. The Sono-Fenton process was performed by indirect sonication in an ultrasonic water bath, which was operated at a fixed 35-kHz frequency. The optimum conditions were determined as [Fe²⁺] = 30 mg/L, [H₂O₂] = 50 mg/L and pH = 3 for the Fenton process and [Fe²⁺] = 10 mg/L, [H₂O₂] = 40 mg/L and pH = 3 for the Sono-Fenton process. The colour removals were 88% and 93.5% by the Fenton and Sono-Fenton processes, respectively. The highest decolorization was achieved by the Sono-Fenton process because of the production of some oxidising agents as a result of sonication. The paper also discussed kinetic parameters. The decolorization kinetic of RB181 followed pseudo-second-order reaction (Fenton study) and Behnajady kinetics (Sono-Fenton study).     

Conductivity and oxygen permeability of a novel oxide Pr2Ni0.8 − x Cu0.2FexO4 and its application to partial oxidation of CH4

Iron-doped Pr₂Ni_0.8Cu_0.2O₄ was studied as a new mixed electronic and oxide-ionic conductor for use as an oxygen-permeating membrane. An X-ray diffraction analysis suggested that a single phase K₂NiF₄-type structure was obtained in the composition range from x = 0 to 0.05 in Pr₂Ni_0.8 − xCu_0.2Fe_xO₄. It is considered that the doped Fe is partially substituted at the Ni position in Pr₂NiO₄. The prepared Pr₂NiO₄-based oxide exhibited a dominant hole conduction in the P_O2 range from 1 to 10^− 21 atm. The electrical conductivity of Pr₂Ni_0.8−xCu_0.2Fe_xO₄ is as high as 10² S cm^− 1 in the temperature range of 873–1223 K and it gradually decreased with the increasing amount of Fe substituted for Ni. The oxygen permeation rate was significantly enhanced by the Fe doping and it was found that the highest oxygen permeation rate (60 μmol min^− 1 cm^− 2) from air to He was achieved for x = 0.05 in Pr₂Ni_0.8 − xCu_0.2Fe_xO₄. Since the chemical stability of the Pr₂NiO₄-based oxide is high, Pr₂Ni_0.75Cu_0.2Fe_0.05O₄ can be used as the oxygen-separating membrane for the partial oxidation of CH₄. It was observed that the oxygen permeation rate was significantly improved by changing from He to CH₄ and the observed permeation rate reached a value of 225 μmol min^− 1 cm^− 2 at 1273 K for the CH₄ partial oxidation.