Development of a robust method for Cd(II) ions analysis using CeO2- and CeO2-Cu-BTC-based electrochemical sensors.

Simple and sensitive electrochemical sensors were fabricated from cerium oxide (CeO2) and copper-benzene tricarboxylic acid-modified cerium oxide (CeO2-Cu-BTC) materials for differential pulse voltammetric analysis of toxic cadmium (Cd) ions in aqueous solutions. The materials were prepared by hydrothermal method and structurally characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray (SEM-EDX), thermogravimetric analysis (TGA), and X-ray diffraction analysis (XRD). The CeO2-modified carbon paste electrode (CeCPE) and the CeO2-Cu-BTC-modified carbon paste electrode (CeBCPE) were electrochemically characterized by their cyclic voltammetry and electrochemical impedance study in standard K3[Fe(CN)6] single-electron redox process. Their electrochemical surface areas, electrode surface coverages, and charge transfer resistances were calculated to be 1.46 cm2, 2.338 × 10-5 mol∙cm-2, and 2790 Ω and 5.48 cm2, 2.476 × 10-5 mol∙cm-2, and 1254.65 Ω for CeCPE and CeBCPE, respectively. These fabricated electrodes were used as electrochemical sensors for cadmium ion estimation by optimizing the experimental parameters through differential pulse voltammetry. The optimized conditions included 10% modifier for CeCPE and 5% modifier for CeBCPE in 0.12 M HCl solution of pH 5 as supporting electrolyte at - 1.2 V deposition for 30 s in 0.01 to 10 mg L-1 linear cadmium solution range. Under these conditions, the limit of quantification (LOQ) of 0.368 mg L-1 and 0.005 mg L-1 was calculated for CeCPE and CeBCPE electrodes, respectively. The limit of detection (LOD) was calculated to be 0.121 mg L-1 and 0.002 mg L-1 for CeCPE and CeBCPE, respectively. All the experimental results indicated that electrodes fabricated from CeO2-Cu-BTC show better performance as compared to CeO2-based electrodes. Both these types of electrochemical sensors presented good repeatability and performance in the presence of interfering ions as well. From these findings, it can also be inferred that these electrochemical sensors can provide a simple and very sensitive method for approximation of toxic cadmium ions in aqueous solutions.

Structural, Optical, and Magnetic Properties of Pure and Ni-Fe-Codoped Zinc Oxide Nanoparticles Synthesized by a Sol-Gel Autocombustion Method.

Pure and Ni-Fe-codoped Zn1 - 2xNixFexO (x = 0.01, 0.02, 0.03, and 0.04) nanoparticles were effectively synthesized using a sol-gel autocombustion procedure. The structural, optical, morphological, and magnetic properties were determined by using X-ray diffraction (XRD), ultraviolet-visible (UV-vis), scanning electron microscopy, and vibrating sample magnetometer techniques. The XRD confirmed the purity of the hexagonal wurtzite crystal structure. XRD analysis further indicated that Fe and Ni successfully substituted the lattice site of Zn and generated a single-phase Zn1-2xNixFexO magnetic oxide. In addition, a significant morphological change was observed with an increase in the dopant concentration by using high-resolution scanning electron microscopy. The UV-vis spectroscopy analysis indicated the redshift in the optical band gap with increasing dopant concentration signifying a progressive decrease in the optical band gap. The vibrating sample magnetometer analysis revealed that the doped samples exhibited ferromagnetic properties at room temperature with an increase in the dopant concentration. Dopant concentration was confirmed by using energy-dispersive X-ray spectroscopy. The current results provide a vital method to improve the magnetic properties of ZnO nanoparticles, which may get significant attention from researchers in the field of magnetic semiconductors.

Mesoporous Silica (MCM-41) Containing Dispersed Palladium Nanoparticles as Catalyst for Dehydrogenation, Methanolysis, and Reduction Reactions.

Generating highly dispersed metal NPs of the desired size on surfaces such as porous silica is challenging due to wettability issues. Here, we report highly active and well-dispersed Pd incorporated mesoporous MCM-41 (Pd@MCM) using a facile impregnation via a molecular approach based on hydrogen bonding interaction of a palladium ß-diketone complex with surface silanol groups of mesoporous silica. Controlled thermal treatment of so obtained materials in air, argon, and hydrogen provided the catalysts characterized by electron microscopy, nitrogen physisorption, X-ray diffraction and spectroscopy. Gratifyingly, our catalyst provided the lowest ever activation energy (14.3 kJ/mol) reported in literature for dehydrogenation of NaBH4 . Moreover, the rate constant (7×10-3  s-1 ) for the reduction of 4-nitrophenol outperformed the activity of commercial Pd/C (4×10-3  s-1 ) and Pd/Al2 O3 (5×10-3  s-1 ) catalysts.

Correction to "Adsorption of Methyl Orange from an Aqueous Solution onto a BPPO-Based Anion Exchange Membrane".

[This corrects the article DOI: 10.1021/acsomega.2c03148.].

Adsorption of Methyl Orange from an Aqueous Solution onto a BPPO-Based Anion Exchange Membrane.

In this research, the development of a novel brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO)-based homogeneous anion exchange membrane (AEM) via the solution casting method was reported. Fourier transform infrared spectroscopy was used to confirm the successful development of the BPPO-based AEM. The prepared AEM showed excellent thermal stability. It exhibited an ion exchange capacity of 2.66 mg/g, a water uptake (W R) of 68%, and a linear swelling ratio of 31%. Methyl orange (MO), an anionic dye, was used as a model pollutant to evaluate the ion exchange ability of the membrane. The adsorption capacity of MO increased with the increase in contact time, membrane dosage (adsorbent), temperature, and pH while declined with the increase in initial concentration of MO in an aqueous solution and molarity of NaCl. Adsorption isotherm study showed that adsorption of MO was fitted well to the Freundlich adsorption isotherm because the value of the correlation coefficient (R 2 = 0.974) was close to unity. Adsorption kinetics study showed that adsorption of MO fitted well to the pseudo-second-order kinetic model. Adsorption thermodynamics evaluation represented that adsorption of MO was an endothermic (ΔH° = 18.72 kJ/mol) and spontaneous process. The AEM presented a maximum adsorption capacity of 18 mg/g. Moreover, the regeneration of the prepared membrane confirmed its ability to be utilized for three consecutive cycles. The developed BPPO-based AEM was an outstanding candidate for adsorption of MO from an aqueous solution.

SPEEK and SPPO Blended Membranes for Proton Exchange Membrane Fuel Cells.

In fuel cell applications, the proton exchange membrane (PEM) is the major component where the balance among dimensional stability, proton conductivity, and durability is a long-term trail. In this research, a series of blended SPEEK/SPPO membranes were designed by varying the amounts of sulfonated poly(ether ether ketone) (SPEEK) into sulfonated poly(phenylene) oxide (SPPO) for fuel cell application. Fourier transform infrared spectroscopy (FTIR) was used to confirm the successful synthesis of the blended membranes. Morphological features of the fabricated membranes were characterized by using scanning electron microscopy (SEM). Results showed that these membranes exhibited homogeneous structures. The fabricated blended membranes SPEEK/SPPO showed ion exchange capacity (IEC) of 1.23 to 2.0 mmol/g, water uptake (WR) of 22.92 to 64.57% and membrane swelling (MS) of 7.53 to 25.49%. The proton conductivity of these blended membranes was measured at different temperature. The proton conductivity and chemical stability of the prepared membranes were compared with commercial membrane Nafion 117 (Sigma-Aldrich, St. Louis, Missouri, United States) under same experimental conditions. The proton conductivity of the fabricated membranes increased by enhancing the amount of SPPO into the membrane matrix. Moreover, the proton conductivity of the fabricated membranes was investigated as a function of temperature. Results demonstrated that these membranes are good for applications in proton exchange membrane fuel cell (PEMFC).

Determination of Blood Calcium and Lead Concentrations in Osteoporotic and Osteopenic Patients in Pakistan.

Osteoporosis is the leading cause of deformity and bones fracture all over the world and has some relationship with the blood concentrations of calcium and lead. Therefore, in the current study, the blood samples of 58 control and 56 clinically diagnosed osteoporotic and osteopenic patients were taken from different hospitals in Pakistan and analyzed for calcium and lead concentrations using atomic absorption spectrometry. In female control samples, the mean calcium value was found to be 98.53 ± 4.81 µg/mL, and in male control samples, the mean blood calcium level was found to be 121.33 ± 7.27 µg/mL. In female control samples, the mean lead value was found to be 0.133 ± 0.005 µg/mL, and in male control samples, the mean lead level was found to be 0.183 ± 0.008 µg/mL. All the male and female control samples showed a mean value of calcium of 115.63 ± 5.2 µg/mL and a mean value of lead of 0.153 ± 0.007 µg/mL. In osteoporotic female patients, the decline in the mean calcium value was found to be 34.93 ± 1.9 µg/mL, and in male patients, the decrease in the mean calcium level was found to be 47.73 ± 2.5 µg/mL. The increase in the mean value of lead in osteoporotic females was 4.13 ± 0.22 µg/mL, whereas in male patients, the increase in the mean lead value was 0.95 ± 0.07 µg/mL. All the male and female patients showed a decrease in the mean value of calcium of 41.43 ± 2.2 µg/mL and an increase in the mean value of Pb of 3.63 ± 0.16 µg/mL.

Lab-scale continuous flow studies for comparative biosorption of cadmium (II) on untreated and xanthated Ficus religiosa biomass.

The present studies report the use of an ecofriendly biomass Ficus religiosa in untreated (UFR) and xanthate treated (XFR) forms for the Cd (II) ions removal in a fixed bed column. FTIR, SEM-EDS, BET surface area, and elemental analysis (CHNS) techniques were used to characterize the biosorbents. The acquired data supported FTIR findings regarding the nature of functional groups present in the materials. Packed bed continuous flow studies explored the effects of various parameters such as Cd (II) ion concentration (100 mg/L-300 mg/L), bed heights (5 cm-30 cm), pH (3-5), at a constant linear flow rate (~1.13 cm/min). The obtained S-shaped breakthrough curves indicated the efficiency of the packed bed for the Cd (II) removal. Breakthrough time and exhaust times increased (67.5 min-390 min and 292.5 min-1852.5 min) (97.5 min-442.5 min and 345 min-1920 min) for unmodified and modified respectively with bed heights. The BDST, Thomas, and Yoon-Nelson models were used to evaluate the experimental results. The Yoon-Nelson model describes the breakthrough data more efficiently compared to other models. Under similar conditions, the modified material exhibited 400% increased capacity (55.20 mg/g) than that of unmodified material (13.33 mg/g). Thus, xanthate modification significantly enhanced the capacity for Cd (II) ions from aqueous solutions. PRACTITIONER POINTS: Xanthate modification of Ficus religiosa is an environmentally friendly process. Modified and unmodified materials were utilized for Cd (II) removal in fixed bed column process which is industrially viable process. Low inlet Cd (II) concentration at pH 5 and higher bed height favored the continuous flow process at fixed flow rate. Modification caused an increase of about 400% in the capacity of material.

Structural and biological investigation of biogenically synthesized titanium dioxide nanoparticles: Calcination and characterization.

The antimicrobial drug resistance is increasing with the passage of time due to wide and improper use of broad spectrum drugs and the demand of the new drug increases day by day. The present study was planned to encounter this problem by synthesizing titanium dioxide nanoparticles (TiO2 NPs) by an eco-friendly route using Cannabis sativa leaves extract. The synthesized TiO2 NPs were calcined at 100, 300, 600, and 900°C in a muffle furnace. The crystallographic parameters were studied by X-ray diffraction and the phase transition occurred above 600°C. The surface morphology of the synthesized samples was studied by transmission electron microscopy (TEM), and scanning electron microscopy (SEM) and the particle size was measured through the ImageJ software. The elemental composition and purity of all the samples were studied by performing energy dispersive X-ray (EDX). All the synthesized TiO2 NPs were tested for their antimicrobial effect against Gram-positive and Gram-negative bacteria using the agar well diffusion method. The activity was found higher against Gram-negative bacteria and compared to Gram-positive bacteria.

Synthesis of DMEA-Grafted Anion Exchange Membrane for Adsorptive Discharge of Methyl Orange from Wastewaters.

This manuscript describes the synthesis of dimethylethanolamine (DMEA)-grafted anion exchange membrane (AEM) by incorporating dimethylethanolamine as ion-exchange content into the polymer matrix via the solution casting method. The synthesis of the DMEA-grafted AEM was demonstrated by Fourier transform infrared (FTIR) spectroscopy. The prepared DMEA-grafted AEM exhibited higher thermal stability, homogeneous morphology, water uptake (WR) of 115%, and an ion exchange capacity (IEC) of 2.70 meq/g. It was used for the adsorptive removal of methyl orange (MO) from an aqueous solution via batch processing. The effect of several operating factors, including contact time, membrane dosage, initial concentration of aqueous dye solution, and temperature on the percentage discharge of MO and adsorption capacity, was evaluated. Experimental data for adsorption of MO onto the DMEA-grafted AEM was analyzed with two parameter and three parameter nonlinear adsorption isotherm models but fitted best using a nonlinear Freundlich isotherm. Adsorption kinetics were studied by using several models, and attained results showed that experimental data fitted well to pseudo-second-order kinetics. A thermodynamic study showed that adsorption of MO onto the prepared DMEA-grafted AEM was an endothermic process. Moreover, it was a feasible and spontaneous process.

Chemical Composition and Bioactivities of Essential Oil from Leaves of Syzygium cumini (L.) Skeels Native to Punjab, Pakistan.

Herbal medicines are widely used for the treatment of different types of diseases like skin and throat infections and other diseases in developing countries. Syzygium cumini (L.) Skeels fruit, leaves and bark were used for the remedies of different diseases anciently. The aim of the present study was to evaluate the chemical profile of Syzygium cumini leaves essential oil (EO) from Punjab, Pakistan. The essential oil was isolated using hydrodistillation technique and analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). Free radical scavenging capacity and antioxidant activity were assessed by using DPPH radical scavenging ability, inhibition of linoleic acid peroxidation, bleaching of ß-carotene in linoleic acid system and reducing power assays. Antimicrobial potential was assessed by disc diffusion assay and measurement of minimum inhibitory concentration (MIC) using resazurin microtiter-plate assay. The anti-heme biocrystallization activity of EO was also assessed. The major components (>3%) found in Syzygium cumini leaves EO were ß-farnesene (3.42 %), caryophyllenol (3.46 %), terpinen-4-ol (3.61 %), ß-myrcene (3.90 %), γ-cadinene (4.09 %), fenchol (4.22 %), cis-ß-ocimene (4.40 %) and 5-methyl-1,3,6-heptatriene (4.90 %). Excellent antioxidant, antimicrobial and weak antimalarial potential was observed. It can be concluded that Syzygium cumini leaves EO has potential application for food and pharmaceutical industries.

Erratum to "Titanium-based nanocomposite materials for arsenic removal from water: A review" [Heliyon 5 (5) (May 2019) e01577].

[This corrects the article DOI: 10.1016/j.heliyon.2019.e01577.].

Titanium-based nanocomposite materials for arsenic removal from water: A review.

Arsenic is highly carcinogenic element and less concentration of this chemical element makes natural water unsafe for human consumption. Versatile techniques including adsorption method have been established to remove the arsenic from water. However, adsorption is found to be one of effective method for the remediation of arsenic from contaminated water. Different types of natural adsorbents i.e. clays, waste materials, carbon based material have been studied widely for the adsorption of arsenic. Recently, nanotechnology is considered to be one of the best technology for waste water treatment. Therefore researchers have synthesized several types of nanoadsorbents and investigated them for the removal of various pollutants including arsenic from water. Now days, attention is paid on development of nanocomposite materials which are proven as competent arsenic adsorbent candidate as compared to other adsorbents due to dominant structural and surface features. Various metal/metal oxide based nanocomposites have been developed and studied for arsenic removal from aqueous media. It has been reported that TiO2 based nanocomposite exhibit stong affinity for both inorganic form of arsenic. Therefore, in this review numerous metal or metal oxide based titania nanocomposites i.e. TiO2-αFe2O3, NHITO, Ce-Ti oxide, Zr-TiO2, RGO-MFT etc. have been discussed in details for the water treatment containing arsenic. This review also presents an overview of low cost adsorbents, titania based nanoadsorbent and hybrid titania nanostructures for the removal of arsenic. In this review paper the particle size, surface area and adsorption efficiency of these titania based materials at different pH are also been presented in tabulated form. It provides the opportunity to choose best titania based nanocomposites for the treatment of arsenic polluted water.

Flow injection online spectrophotometric determination of uranium after preconcentration on XAD-4 resin impregnated with nalidixic acid.

In this work, spectrophotometer was used as a detector for the determination of uranium from water, biological, and ore samples with a flow injection system coupled with solid phase extraction. In order to promote the online preconcentration of uranium, a minicolumn packed with XAD-4 resin impregnated with nalidixic acid was utilized. The system operation was based on U(VI) ion retention at pH 6 in the minicolumn at flow rate of 15.2 mL min(-1). The uranium complex was removed from the resin by 0.1 mol dm(-3) HCl at flow rate of 3.2 mL min(-1) and was mixed with arsenazo III solution (0.05 % solution in 0.1 mol dm(-3) HCl, 3.2 mL min(-1)) and driven to flow through cell of spectrophotometer where its absorbance was measured at 651 nm. The influence of chemical (pH and HCl (as eluent and reagent medium) concentration) and flow (sample and eluent flow rate and preconcentration time) parameters that could affect the performance of the system as well as the possible interferents was investigated. At the optimum conditions for 60 s preconcentration time (15.2 mL of sample volume), the method presented a detection limit of 1.1 µg L(-1), a relative standard deviation (RSD) of 0.8 % at 100 µg L(-1), enrichment factor of 30, and a sample throughput of 42 h(-1), whereas for 300 s of the preconcentration time (76 mL of sample volume), a detection limit of 0.22 µg L(-1), a RSD of 1.32 % at 10 µg L(-1), enrichment factor of 150, and a sampling frequency of 11 h(-1) were reported.