RESUMO
The present study aims to prepare waste water caltrop (Trapanatans L.) epicarp (WCS)-based adsorbents such as raw WCS (WCS-Raw), citric acid-grafted WCS (WCS-CA), acrylamide-grafted WCS (WCS-AM), and calcined WCS (WCS-Si) for Ni(II) removal from aqueous solution in batch adsorption process. The physical and chemical properties of the prepared adsorbents were investigated by different characterization techniques such as scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, nitrogen adsorption-desorption analyses, and pH at the Point of Zero Charge (pHpzc) in order to assess the suitability and effectiveness of the adsorbents for the removal of Ni(II) by understanding their surface morphology, chemical composition, porosity, and surface charge properties. The experimental Ni(II) adsorption data followed both the Langmuir isotherm and the pseudo-second-order kinetic model suggesting the adsorption process on the prepared adsorbents is well-described by these models. The modified adsorbents WCS-CA, WCS-AM, and WCS-Si exhibited a maximum adsorption capacity of 52.08, 40.32, and 158.73 mg/g, respectively, while WCS-Raw had a capacity of 29.06 mg/g. The thermodynamic study revealed that the adsorption process was feasible, spontaneous, and endothermic. The desorption study demonstrated that the adsorbents could be reused for multiple cycles with minimal loss of activity. The present work evidenced the potential practical applicability and sustainability of the WCS-based adsorbents as promising adsorbents in treating and removing Ni(II) from wastewater.
RESUMO
A novel electrochemical (EC) chlorobenzene (CBZ) sensor was fabricated using a ternary oxide RuO2/ZnO/TiO2 nanocomposite (NC)-decorated glassy carbon electrode (GCE). The nanoparticles (NPs) were synthesized by a wet-chemical method and characterized by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and ultraviolet-visible (UV-vis) spectroscopy. The synthesized RuO2/ZnO/TiO2 NC was layered as thin film on a GCE with Nafion (5% suspension in ethanol) adhesive, and the as-prepared sensor was subjected to CBZ analysis using an electrochemical approach. The calibration of the proposed CBZ sensor was executed with a linear relation of current versus concentration of CBZs known as the calibration curve. The sensitivity (32.02 µA µM-1 cm-2) of the CBZ sensor was calculated from the slope of the calibration curve by considering the active surface area of the GCE (0.0316 cm2). The lower detection limit (LD; 98.70 ± 4.90 pM) was also calculated at a signal-to-noise ratio of 3. Besides these, the response current followed a linear relationship with the concentration of chlorobenzene and the linear dynamic range (LDR) was denoted in the range of 0.1 nM to 1.0 µM. Moreover, the CBZ sensor was found to exhibit good reproducibility, reliability, stability, and fast response time. Finally, the sensing mechanism was also discussed with the energy-band theory of ternary doped semiconductor materials. The sensing activity of the proposed sensor was significantly enhanced due to the combined result of depletion layer formation at the heterojunction of RuO2/ZnO/TiO2 NCs as well as the activity of RuO2 NPs as oxidation catalysts. The proposed CBZ sensor probe based on ternary oxide RuO2/ZnO/TiO2 NCs was developed with significant analytical parameters for practical application in monitoring the environmental pollutants of CBZs for the safety of environmental fields on a large scale.
