Fabrication of AuNPs/MWCNTS/Chitosan Nanocomposite for the Electrochemical Aptasensing of Cadmium in Water

Cadmium (Cd2+) is one of the most toxic heavy metals causing serious health problems; thus, designing accurate analytical methods for monitoring such pollutants is highly urgent. Herein, we report a label-free electrochemical aptasensor for cadmium detection in water. For this, a nanocomposite combining the advantages of gold nanoparticles (AuNPs), carbon nanotubes (CNTs) and chitosan (Cs) was constructed and used as immobilization support for the cadmium aptamer. First, the surface of a glassy carbon electrode (GCE) was modified with CNTs-CS. Then, AuNPs were deposited on CNTs-CS/GCE using chrono-amperometry. Finally, the immobilization of the amino-modified Cd-aptamer was achieved via glutaraldehyde cross-linking. The different synthesis steps of the AuNPs/CNTs/CS nano assembly were characterized by cyclic voltammetry (CV). Electrochemical impedance spectroscopy (EIS) was employed for cadmium determination. The proposed biosensor exhibited excellent performances for cadmium detection at a low applied potential (−0.5 V) with a high sensitivity (1.2 KΩ·M−1), a detection limit of 0.02 pM and a wide linear range (10−13–10−4 M). Moreover, the aptasensor showed a good selectivity against the interfering ions: Pb2+; Hg2+ and Zn2+. Our electrochemical biosensor provides a simple and sensitive approach for Cd2+ detection in aqueous solutions, with promising applications in the monitoring of trace amounts of heavy metals in real samples.

Engineering of Calcium Alginate- PANI@Sawdust Wood hydrogel Bio-beads for the Removal of the Sulfonate Groups-Containing Orange G dye from Aqueous Solution

The aim of this work is to investigate the adsorption performance of orange G (OG) dye from aqueous solutions employing PANI@sawdust biocomposite enrobed by calcium-alginate biobeads (Alg-PANI@SD). The as-prepared adsorbent was characterized by scanning-electron-microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and Fourier transforms infrared (FT-IR) spectroscopy, and used to remove Orange G dye from water. batch tests were performed as a function of adsorbent dosage, pH, contact time, interfering ions and initial OG dye concentration. Experimental results show that the kinetic model of pseudo-first-order (PFO) and Freundlich isotherm provided a good fitting of the whole experimental data. The results revealed that the as-prepared tricomposite Alg-PANI@SD, has the potential to be applied as a low-cost adsorbent for the adsorption of OG dye from aqueous media.

Kinetics, Isotherms and Adsorption–Desorption Behavior of Phosphorus from Aqueous Solution Using Zirconium–Iron and Iron Modified Biosolid Biochars

Excessive discharge of phosphorus (P) to aquatic ecosystems can lead to unpleasant eutrophication phenomenon. Removal and recovery of P is challenging due to low C/N ratios in wastewater, hence the development of efficient removal and recovery of P strategies is essential. In this study, zirconium–iron (Zr–FeBC) and iron modified (Fe–BC) biosolid biochars were examined to investigate their capacity for the removal of P by batch experiments. The influence of solution pH, biochar dose, initial P concentration, ionic strength, interfering ions and temperature were also studied to evaluate the P adsorption performance of biochars. The P experimental data were best described with pseudo-second order kinetics and the Freundlich isotherm model. The maximum P adsorption capacities were reached to 33.33 and 25.71 mg g−1 for 24 h by Zr–FeBC and Fe-BC at pH 5 and 4, respectively. Desorption studies were performed to investigate the reusability, cost-effectiveness and stability of the adsorbents Zr–FeBC and Fe-BC. The adsorption–desorption study suggests that both examined biochars have considerable potentiality as adsorbent candidates in removing as well as recovery of P from wastewaters. Results also reveal that the regenerated Zr–FeBC and Fe–BC could be utilized repetitively in seven adsorption–desorption cycles using NaOH as a desorbing agent, which greatly reduces the P-removal cost from wastewaters. Thus, P enriched biochar could potentially be used as fertilizer in the agriculture sector.

Manufacturing of a New Selective Membrane Electrode for Neomycin Sulfate and its Estimation by Potentiometric Method

The research aims to prepare a new ionic membrane selective electrode for NYM Neomycin based on tungstophosphoric acid (TPA), Poly Vinyl Chloride (PVC) and DPPH (Di-Butyl Phthalate). It was found that the electrode is sensitive to concentrations ranging between (1 x 10-1-1 x 10-5) mol/L, and it gave a Nernstian response of (29.7 mV/decade) and a correlation coefficient (r) of (0.9939). The factors affecting the response of the electrode were studied, as it was found that the best concentration of the internal filling solution was (1 x 10-3) mol/L, and that the best pH range in which the electrode worked was between (3.5-1.5) and the best Nernstian response at pH (pH = 2.5) The effect of temperature was also studied, as it was found that the best temperature was (25°C) and the response time of the electrode was between (20-40) seconds. It was also found that the chronological age of the electrode was (25) days. The selectivity coefficient (Ki,jpot) was calculated in the presence of negative and positively charged interfering ions.

Synthesis, Characterization, and Application of Chalcone Derivatives as Chemosensors for Cyanide Anions

Research Background: The extreme toxicity of cyanide ions to living organisms encourages the researcher to develop new chemosensors for their sensitive and selective detection. Among various classes of chemosensors, chalcones are believed to be a promising candidate for designing new chemosensors for anions due to easy modification in its skeleton and conjugation system. Research Gap and Problem Statement: Despite having various medical applications and properties, the recognition ability of chalcone derivatives is not widely explored. The traditional methods known for the sensing of cyanide ions are ion chromatography or cyanide selective electrodes. However, these methods need skilled operators and are found to be expensive and time-consuming. Also, the available methods for detection of cyanide ions are not suitable for on-site monitoring and show interference from other competitive anions such as fluoride, acetate, and hydroxide ions. Hence, this encouraged us to explore the chalcone derivatives as chemical sensors that are capable of detecting the cyanide ions in presence of competitive anions such as fluoride, acetate, and hydroxide ions. Objectives of the study: The development of new chalcone analogs (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6), which are particularly important for the future development of chemosensors for the detection of cyanide ions in presence of various interfering ions such as fluoride, acetate, and hydroxide ions. Methods: The sensing behavior of chalcone derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) have been investigated toward various anions (CN-, F-, Cl-, Br-, NO3-, SO42-, PO42-, OH-, OAc-) using UV-vis spectroscopy. Interestingly, among various anions tested, derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) function as highly selective chemosensors for the detection of cyanide ions. Results: We have synthesized two chalcone based derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) with simple condensation reaction for the detection of cyanide ions. The various results indicated the quick response of (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) toward cyanide anions. These two chalcone derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) showed not only spectral change with selectivity but also showed sensitivity for the detection of cyanide anions. The developed chalcone derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) detect cyanide ions in presence of various interfering ions such as fluoride, acetate, and hydroxide ions. The chemosensors (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) for the detection of cyanide ions are particularly smart due to their real-time analysis, simplicity, and low cost in comparison to other closely related processes such as fluorescence. Conclusion: The sensitivity studies show the high reactivity of derivative 1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) as compared to (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6). The detection limit for derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) was 1.2 µM and 300 µM, respectively. The results of (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) for cyanide detection were satisfying and suggesting their potential application for cyanide detection. Future direction: Further research of this field is to develop water soluble chalcone based probes, which show emission in the Near Infra-Red (NIR) region to provide favorable conditions for biological applications.

Arsenic and Fluoride in Groundwater, Prevalence and Alternative Removal Approach

Contamination of drinking water by arsenic and fluoride is a global problem, as more than 300 million people in more than 100 countries have been affected by their presence. These elements are considered the most serious contaminants in drinking water and their removal is a worldwide concern. Therefore, the evaluation of three alternative approaches—electrocoagulation, adsorption by biomaterials, and adsorption by metal oxide magnetic nanoparticles (MNPs)—was performed for arsenic and fluoride removal from groundwater. Arsenic removal from synthetic and groundwater (well water) was accomplished with the three processes; meanwhile, fluoride removal from groundwater was only reported by two methods. The results indicate that an electrocoagulation process is a good option for As (>97%) and F (>90%) removal in co-occurrence; however, the operational conditions for the removal of both pollutants must be driven by those used for fluoride removal. As (80–83%) and F (>90%) removal with the biomaterials was also successful, even when the application objective was fluoride removal. Finally, MNPs (Co and Mn) were designed and applied only for arsenic removal and reached >95%. Factors such as the pH, the presence of interfering ions, and the initial concentration of the contaminants are decisive in the treatment process’s efficiency.

Removal of Zirconium (Zr) from Aqueous Solution by Polymer Enhanced Ultrafiltration

Although the world output of zirconium has been declining, increasing zirconium consumption cannot compete with this situation. For this reason, removal and recovery of zirconium become important. This work is focused on the removal of Zirconium (as ZrO22+) ions from an aqueous solution using polymer-enhanced ultrafiltration (PEUF) techniques with water-soluble Poly (sodium-p-styrene sulfonate, SSS) sorbent. The negatively charged sulfonic acid groups in the polymer interact with positively charged ZrO22+ cation thereby enabling the efficient removal of ZrO22+through ultrafiltration. The effect of polymer: zirconium mole ratio, initial solution pH, and the presence of interfering ions on the removal of zirconium was investigated. The obtained results demonstrated that ZrO22+ can be removed from the aqueous solution by the PEUF technique with more than 99% efficiency at pH ≥ 2 using polymer: Zr molar ratio of 5:1. The presence of interfering ions did not affect the percent removal of ZrO22+.

Capacitance Electrochemical pH Sensor Based on Different Hafnium Dioxide (HfO2) Thicknesses

Over the past years, to achieve better sensing performance, hafnium dioxide (HfO2) has been studied as an ion-sensitive layer. In this work, thin layers of hafnium dioxide (HfO2) were used as pH-sensitive membranes and were deposited by atomic layer deposition (ALD) process onto an electrolytic-insulating-semiconductor structure Al/Si/SiO2/HfO2 for the realization of a pH sensor. The thicknesses of the layer of the HfO2 studied in this work was 15, 19.5 and 39.9 nm. HfO2 thickness was controlled by ALD during the fabrication process. The sensitivity toward H+ was clearly higher when compared to other interfering ions such as potassium K+, lithium Li+, and sodium Na+ ions. Mott−Schottky and electrochemical impedance spectroscopy (EIS) analyses were used to characterise and to investigate the pH sensitivity. This was recorded by Mott–Schottky at 54.5, 51.1 and 49.2 mV/pH and by EIS at 5.86 p[H−1], 10.63 p[H−1], 12.72 p[H−1] for 15, 19.5 and 30 nm thickness of HfO2 ions sensitive layer, respectively. The developed pH sensor was highly sensitive and selective for H+ ions for the three thicknesses, 15, 19.5 and 39.9 nm, of HfO2-sensitive layer when compared to the other previously mentioned interferences. However, the pH sensor performances were better with 15 nm HfO2 thickness for the Mott–Schottky technique, whilst for EIS analyses, the pH sensors were more sensitive at 39.9 nm HfO2 thickness.

Study of the influence of interfering ions of heavy metals and various sample preparation on the determination of mercury impurity in protamine sulfate by stripping voltammetry

Aim. To determine the content of mercury in protamine sulfate samples with different sample preparation. To study the effect of interfering ions on the content of mercury impurity in protamine sulfate by stripping voltammetry (SV). Materials and methods. We used a solution for injection of protamine sulfate, batches 515091, 514062, 514111; for sample preparation — various options for dilution and precipitation. Dilution was carried out with bidistilled water, and the precipitation of proteins — with sodium tungstate in 2 options. Mercury impurities were determined by the SV method. Results. The mercury content in protamine sulfate samples was 0.000417 ± 0.00140 and 0.000420 ± 0.00152 mg/l when diluted with water 1 : 2 and 1 : 1 respectively and 0.000462 ± 0.00131 and 0.000459 ± 0.00121 when precipitated with tungstate in options 1 and 2 respectively. With the addition of an interfering ion, for example, Cu2+, the content of mercury in the medicinal product was 0.000606 ± 0.00015, 0.000452 ± 0.00013 and 0.0004212 ± 0.00011 mg/l for protamine sulfate batches 514062, 515091 and 514111 respectively, which does not exceed the values determined by the product specification. The addition of Pb2+, Fe2+, Zn2+, Cu2+, and Cd2+ ions also had no effect on the determination of the mercury content in protamine sulfate samples. Conclusion. To determine the mercury impurity in the protamine sulfate, special sample preparation is not required. Ions of Cu2+, Pb2+, Fe2+, Cd2+, Zn2+ do not affect the result of determining the mercury content in protamine sulfate samples by the SV method, which indicates a high selectivity of the method used.