Shabnam Shahida

A novel MoS ₂ -incorporated sulfonated polystyrene composite (MOSP) is developed for the selective removal of rhodamine B (RhB) from aqueous solutions.

A sulfonated polystyrene resin-supported tungsten oxide (SO ₃ -PSWO) was synthesized and evaluated for its efficiency in removing lead (Pb ²⁺ ) from aqueous solutions.

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. Graphical Abstract

In this study, we engineered a sub-70 nm nanocomposite of ZnO/Zn₂TiO₄ using a low-temperature solution-phase method with titanium isopropoxide and zinc acetate as precursors, and isopropyl alcohol and water as solvents. The investigation focused on nanocomposite growth by varying precursor and surfactant concentrations and their efficiency within different pH ranges. All three ZnO/Zn₂TiO₄ nanocomposites exhibited hexagonal wurtzite ZnO and Zn₂TiO₄ structures. The crystallite size in these nanocomposites ranged from 39.50 nm to 62.67 nm for ZnO and 21.24 nm to 26.15 nm for Zn₂TiO₄. Morphological observations using FESEM revealed the formation of dispersed cotton packet-like nanocomposites with sizes ranging from 18 to 350 nm. FTIR analysis showed peaks indicative of Ti–O and Zn–O bond formation, and EDX spectrum confirmed the presence of Ti, O, and Zn. UV spectrums and photocatalytic investigations confirmed the successful formation of ZnO/Zn₂TiO₄ nanocomposites with notable photocatalytic degradation efficiency for methylene blue dye under various conditions. These findings suggest the potential applicability of the synthesized nanocomposites for environmental pollutant degradation.

In this work, we report the engineering of a sub-70 nm nanocomposite of ZnO/Zn2TiO4 using a low-temperature solution-phase method. Titanium isopropoxide and zinc acetate were used as precursors, and isopropyl alcohol and water were used as solvents. The investigation focused on the growth of nanocomposites by varying the concentrations of precursors and surfactants, as well as their efficiency within different pH ranges. All three ZnO/Zn2TiO4 nanocomposites consist of hexagonal wurtzite ZnO and Zn2TiO4 structures in the three nanocomposites. The crystallite size in three ZnO/Zn2TiO4 nanocomposites, with a hexagonal wurtzite ZnO structure, were measured to be 62.67, 40.34, and 39.50 nm. The crystallite size values in three ZnO/Zn2TiO4 nanocomposites were 26.15 nm, 25.36 nm, and 21.24 nm, respectively, with Zn2TiO4. Morphological observations, conducted using FESEM, reveal the formation of three ZnO/Zn2TiO4 nanocomposites across the entire sample. These nanocomposites resemble dispersed cotton packets, with sizes ranging from 18 to 350 nm. Peaks in the range of 610-1250cm-1 are attributed to Ti-O bond formation and peak located at 1350-1450 cm-1 are attributed to Zn-O bond formation. Also, EDX spectrum reveals peaks for various sample components such as Ti, O and Zn. UV spectrums confirmed the formation of three nanocomposite of ZnO/Zn2TiO4 as showing two peaks for each sample. Photocatalytic investigation carried out by analyzing the UV-Visible absorption spectra of methylene blue dye on the surface of ZnO/Zn2TiO4 nanocomposites, dye degradation at various irradiation time intervals, dye degradation at varied catalyst concentrations and the influence of pH on dye-degradation. Furthermore, the said nanocomposites were used to degrade environmental pollutant (Methylene blue dye). Different sets of experiments were conducted under ambient conditions which show an excellent photo catalytic degradation efficiency.

In the current study, magnetic oxide nanoparticle-impregnated tea waste (TW-Fe₃O₄) is employed as an adsorbent to remove phosphate ions (PO₄³⁻) from an aqueous solution. By utilizing a variety of analytical methods, the TW-Fe₃O₄ nano-adsorbent was characterized by FE-SEM, TEM, EDX, BET, FTIR and XRD. The FE-SEM of TW-Fe₃O₄ demonstrated the adsorbent’s granular morphology with a variety of magnetic nanoparticle sizes and shapes. The XRD of TW-Fe₃O₄ showed two diffraction peaks at 2θ values 30.9° and 35.4°, which are in correspondence with the diffraction pattern of magnetite. The synthesis of a TW-Fe₃O₄ adsorbent with a greater surface area and porosity was demonstrated by BET analysis. Numerous adsorption factors like initial concentration of PO₄³⁻ ion, pH of the medium, contact time, temperature and adsorbent dose were optimized for phosphate removal. The maximum removal of 92% was achieved by using the adsorbent dose of 1.2 g at 323 K (pH 5). Pseudo-second-order and intra-particle diffusion models were fitted to the sorption kinetic, whereas adsorption isotherm data were found well fitted to Freundlich and Dubinin–Radushkevich (D-R) models. The highest adsorption capacity of TW-Fe₃O₄ towards phosphate ions was 226.8 mg/g, which is significantly higher than other reported bio-adsorbents. According to thermodynamic data, phosphate adsorption at the solid–liquid interface was of an endothermic and spontaneous nature and characterized by enhanced inevitability.

Oxytetracycline impregnated XAD-4 resin was prepared and then used for the online preconcentration of zirconium (IV) from aqueous solution. HCl was used for the elution of zirconium from the complex retained on XAD-4 resin. Arsenazo-III solution was used as chromogenic reagent for the spectrophotometric determination of eluted zirconium (IV) ions. The developed system showed greater sensitivity and selectivity as compared to many reported methods. The current study achieved a detection limit of 0.47 and 0.10 µgL⁻¹, preconcentration factor of 52 and 247 and sample throughput of 40 and 10 samples per hour for concentration range from 10 to 60 µg L⁻¹ (60s preconcentration time) and from 2 to 12 µgL⁻¹ (300s preconcentration time) respectively. The method was successfully applied for the determination of Zirconium (IV) from spiked water and IAEA-soil sample.

The groundwater is one of the biggest natural resources for providing drinking water to millions of people all around the globe. However, the presence of large amount of arsenic(V) in water causes serious health hazards to the consumers which necessitates the development of cost-effective remediation. The CuO/TiO2 nanocomposites were prepared by the precipitation-deposition method for the removal of the arsenate ion (AsO43-) from water. The prepared samples were characterized by powder X-ray diffraction, Fourier transform infrared, and scanning electron microscopy to examine crystallite size and structure, material purity, textural features, morphology, and surface area. The effect of different operating parameters such as pH, contact time, initial concentration of arsenic(V) and nanocomposite dose on the removal rate of arsenic(V) was examined to optimize the adsorption performance of the CuO/TiO2 nanocomposite. In addition, the adsorption mechanism was studied by employing Langmuir and Freundlich adsorption isotherms to gain better understanding of the adsorption mechanism. The Freundlich adsorption isotherm fits well with the experimental data and the maximum adsorption capacity of the Langmuir model was found to be 90 mg/g for arsenic(V). The CuO/TiO2 nanocomposite shows remarkable adsorption performance for the treatment of arsenic(V) contaminated water samples. This study provides a cost-effective solution for the safe use of groundwater contaminated with arsenic.

Environmental pollution caused by heavy metal ions has become a major health problem across the world. In this study, a selective colorimetric sensor based on starch functionalized silver nanoparticles (St-Ag NPs) for rapid detection of Hg²⁺ in real samples was developed. The environmentally friendly green approach was utilized to synthesize starch functionalized silver nanoparticles (St-AgNPs). A multi-technique approach involving UV-Vis absorption spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) was used for the characterization of St-Ag NPs. These starch functionalized AgNPs were tested for the detection of heavy metals at 25 °C. The screening process revealed clear changes in the AgNPs color and absorption intensity only in the presence of Hg²⁺ due to the redox reaction between Ag⁰ and Hg²⁺. The color and absorption intensity of nanoparticles remain unchanged in the presence of all the other tested metals ion. The proposed method has strong selectivity and sensitivity to Hg²⁺ ions, with a detection limit of 1 ppm revealed by UV-visible spectrophotometry. The proposed procedure was found to be successful for the detection of Hg²⁺ in real samples of tap water.