Journal of Water and Environmental Nanotechnology
Volume:6 Issue: 3, Summer 2021

Here in the present study, we report the synthesis of ZnO nanoparticles, ZnO/CuO(3%), ZnO/CuO(5%), and ZnO/CuO(10%), nanocomposites using simple precipitation method with variation of CuO content and the activities of prepared samples were investigated for degradation of Brilliant Cresyl Blue (BCB) dye under visible light conditions in aqueous solutions. The structural, morphology, optical and compositional characteristics of fabricated samples were characterized by using Fourier Transform Infra-Red (FTIR) Spectroscopy, Field Emission Scanning Electron Microscopy combine electron dispersive spectroscopy (FESEM-EDS) and UV-vis spectroscopy. FESEM images show that ZnO nanoparticles are polygon like shape structure while ZnO/CuO have polygon and sheet shape structures. XRD patterns reflect the high crystalinity and purity of samples. The optical band gap values determined from optical absorption method indicate that band gap energy decreased with increase of CuO content in ZnO. The catalytic efficiency of the ZnO/CuO hybrid nanocomposite was observed to be higher than the ZnO nanoparticles under similar reaction conditions, 97.30% of Brilliant Cresyl Blue (BCB) dye was degraded after 100 min of irradiation of visible light radiation using the ZnO/CuO(5%) hybrid nanocomposite. The higher efficiency of ZnO/CuO compare to ZnO may be due to increased surface area and decreased band gap energy. The kinetic study of the photoctalytic degradation displayed that hybrid ZnO/CuO degrdaded dye with high rate constant k (34.88x10-3 min -1) compare to ZnO (k, 7.00x10-3 min-1). The optimization of reaction conditions of photodegradation process were attained by the variation in reaction factors such as pH, dye concentration, catalyst amount, and reaction time.

Removal of heavy metals from waste water is a need of the hour. Titanium dioxide (TiO2) nanoparticles were functionalized using succinic anhydride (SA) and adsorption of copper (II) on SA functionalized TiO2 nanoparticles (TiOSA) was carried out. The adsorption of Cu (II) on TiOSA was estimated with respect to pH, contact time and adsorbent dose. The study confirms the best removal of Cu (II) using the said adsorbent is at pH 8. The Cu (II) concentration can be reduced to less than 1.1 mg/L at contact time of 180 min with initial 15 mg/L Cu (II) concentration using adsorbent dose of 0.6 g/50 mL. The study reveals that the adsorption process preferably follows the Langmuir isotherm model. Also, the thermodynamic parameters like entropy change (∆S°), enthalpy change (∆H°) and free energy change (∆G°) were calculated for the adsorption process. The pseudo-second order kinetic model was found to be better fitted to the adsorption.

We report an Environmental-friendly method for the synthesis of Au-Ag alloy nanoparticles (ANPs) by using Anethum graveolens fresh leaf extract as a reducing and stabilizing agent. The precursor solutions of Au (HAuCl4: 3H2O), Ag (AgNO3) and leaf extract were mixed by varying molar ratios and heated with continuous stirring at 70℃ for an hour leads a formation of Au-Ag ANPs with different atomic compositions. The periodic observation of colour changes indicated the formation of Au-Ag ANPs and got confirmed by the measurement of UV-Vis spectroscopy. The synthesized Au-Ag ANPs were characterized for morphological and elemental composition using Transmission Electron Microscopy (TEM) in conventional and scanning TEM (STEM) mode. The TEM image analysis shows that the synthesized Au-Ag ANPs were found to be in spherical shape with a broad size distribution with a mean size of 23 ± 18 nm. The energy dispersive X-ray (EDX) spectrometry in the STEM mode confirms the formation of Au-Ag ANPs . To show that these biosynthesized Au-Ag ANPs can be used as SERS (Surface Enhanced Raman Scattering) substrates, we carried out SERS studies using Crystal Violet (CV) and Rhodamine 6G (R6G) as test molecules by using 514.5 nm laser excitation wavelength. The detection level achieved was 50µM of CV and R6G, which would lead to exploring biosensing applications.

Paper industries will be using a different kind of dyes for producing various kinds of paper. Rhodamine–B (Rh-B) dye is one of the major sources of color effluents from textile and paper dyeing industries, and they cause long-term effects for on an aquatic environment. So this work mainly focused on the synthesis of carbon nanoparticles from neem leaves, characterization and its adsorption and photocatalytic action against Rh-B dye. In this study, Carbon nanoparticles (C NPs) from neem leaves were synthesized for adsorption and photo catalytic degradation of Rh-B dye used in paper industries. The synthesized carbon NPs were characterized by the powder X-Ray Diffraction and Scanning Electron Microscopy. The adsorption and photocatalytic properties of Ccarbon NPs were examined for 1 hour by studying the degradation of the Rh-B dye at every 5 minutes time interval through UV-Visible spectrophotometer. The results obtained shown that carbonC NPs acts as better adsorbents than as photo catalysts.

Copper oxide nanoparticles are prepared adopting green synthesis route by using Aloe vera plant extract instead of synthetic and polymeric stabilizing agents in mild alkaline aqueous conditions. The synthesised CuO nanoparticles (CuO nps) are characterised by Powder XRD and HR-TEM measurements. Using the as –synthesized CuO nps and reduced graphene oxide (rGO), nanocomposites comprising CuO nps- rGO are prepared by hydrothermal and ultrasonic methods. Nano composites are characterized using Powder XRD, HR-TEM and FE-SEM data. The fabricated CuO nps - rGO nanocomposites are coated onto glassy carbon electrode (GCE) for facile detection and electro oxidation of water polluting dyes such as the Ponceau 4R (P4R) and Alizarin Red (AR) using cyclic voltammetry . Electro oxidation of the dyes occurred at appreciably lower oxidation potentials like 0.45 V and 0.6 V for P4R and AR respectively along with the decoloration of the dyes. The absorbance of the analyte dye solutions are measured at intervals of time of progress of electro oxidations. The overall first order rate coefficient values for dye degradations are found out from absorbance time variance data. The results indicate that CuO nps - rGO nanocomposites decorated GCE acted as an efficient electrode surface for sensing and degradation applications for the chosen dye solutions. P4R azo dye degradation response was found to be better than AR anthroquinon dyes.

Multifunctional Zirconia Nanorods performing photocatalysis, anti-bacterial and anti-fungal activities are presented in this article. Tetragonal Zirconia is synthesized by simple co-precipitation method. The synthesized Zirconia is characterized by various characterization methods such as XRD, SEM, EDX, UV-Vis, PL, VSM and TG/DTA analysis. Exploration of powder XRD pattern indicates tetragonal phase. SEM image illustrates rod-shaped morphology. UV-Vis spectra reveal that the synthesized catalyst has wide band gap of about 4.6eV. The emission peaks in the PL spectra reveal the presence of oxygen vacancies in the sample. Room Temperature Ferromagnetism (RTFM) is confirmed from VSM measurements. The performance of Zirconia nanorods in various applications such as photocatalysis, anti-bacterial and anti-fungal activities has been analyzed. t-ZrO2 photo catalyst degrades methylene blue dye with 80% removal efficiency in 180 minutes under UV light irradiation. t-ZrO2 obtained 28mm inhibition zone against Staphaureus for anti-bacterial assessment while Amikacin has 15mm inhibition and obtained 25mm inhibition zone against Candida Albicans for anti-fungal assessment while Nystatin has 20mm inhibition. t-ZrO2 shows superior inhibiting effect against both gram positive and gram negative bacterial pathogens. Owing to its high surface area it exhibits greatest inhibiting effect against fungal strain.

Recent developments in nanotechnology lead to draw scientist's interest in green synthesis nanoparticles because of their importance in all fields of sciences. This paper is an overview of Ag nanoparticles biosynthesis (AgNPs) by aerial part of Alcea rosea extract. Synthesis procedures were described, with no stabilizers or surfactants. The synthesized AR@AgNPs were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and UV-Vis analysis. The UV-Vis spectrum of AR@AgNPs shown a characteristic surface plasmon resonance (SPR) peak at 425 nm. Scanning electron microscope revealed spherical shaped with a diameter range of 10-30 nm. Energy dispersive X-ray spectroscopy analysis demonstrated the peak in silver region confirming presence of elemental silver. Evaluation of the antibacterial and antileishmanial activity of biosynthesized silver nanoparticles was performed. AR@AgNPs exhibit effective antibacterial activity against seven ATCC strains of bacteria and eight strains of drug-resistant bacteria. Also, their activity against leishmaniasis was studied on both promastigotes and amastigotes.

A sensory system was manufactured and tested to detect carcinogenic organochlorines, such as trihalomethanes (THM), in effluents produced by a biodigestion septic tank. Gold-coated interdigitated microelectrodes were coated with various nanostructured conducting polymers, single or mixed, under different conditions and configurations. Polymer films were assembled by the self-assembly technique and their impedance was analyzed in a frequency range from 1 Hz to 1 MHz. The results of the sensory system, analyzed by the PCA Main Component Analysis, allowed to identify the discrimination of the different samples tested. Good discrimination between sensors was also observed, when PCA's were obtained, in contamination experiments with standard solutions of total trihalomethanes (TTHM), obtaining a total variance (PC1 = 98.02%; PC2 = 1.98%) of the observations. The sensory system based on global selectivity using interdigitated electrode and nanostructured conducting polymers allowed the statistical discrimination of samples. The future expectation is to update the system and implement monitoring of nanostructured sensors based on the reuse of domestic effluents, mainly for agricultural applications or for other purposes, in a sustainable way.