Journal of Water and Environmental Nanotechnology
Volume:7 Issue: 2, Spring 2022

Butachlor is a herbicide that belongs to the acetanilide family. It is widely used as a granule-based post-emergence herbicide on rice in India. As a result of the ongoing usage of these synthetic substances, soil fertility and soil organisms are declining. Differential pulse voltammetry was used to determine butachlor herbicide in soil samples with a modified glassy carbon electrode voltammetric sensor with palladium-supported multiwalled carbon nanotubes (Pd@MWCNTs). Scanning electron microscopy, energy dispersive x-ray spectroscopy, and X-ray diffraction spectroscopy were used to investigate the morphology of Pd@MWCNTs, while cyclic and differential pulse techniques were used to investigate the voltammetric properties. The butachlor herbicide under voltammetric investigation involves irreversible, two-electron reduction based on the protonation of the carbonyl group (>C=O). The voltammetric method was developed for the determination of butachlor in phosphate buffer solution at pH 6.0 as a supporting electrolyte. A good linear response to butachlor in the concentration ranging from 0.10 μg⸳mL−1 to 32.0 μg⸳mL−1 was observed, and a limit of detection of 0.044 μg⸳mL−1 was obtained with the calculation based on signal/noise=3. The suggested method was efficaciously applied for the detection of butachlor in soil samples.

Fe3O4/ ZnO/Ag magnetic nanocomposite was synthesized for the first time and its ability was evaluated for photocatalytic degradation of albumin in aqueous solutions under UV-A light. The resulting nanoparticles were then characterized using X-ray diffraction (XRD), scanning electron microscopy (FESEM), vibration magnetometer (VSM), and Fourier infrared (FTIR). The effects of some parameters such as pH, initial albumin concentration, catalyst concentration, and temperature were also investigated in the photodegradation of albumin. The results showed that the maximum removal of albumin was obtained at pH 9, catalyst concentration of 0. 5 g/l, initial albumin concentration of 150 mg/l, and room temperature in 90 min. Under the optimum conditions, the total amount of organic carbon (TOC) was 56%. Kinetic degradation experiments followed the pseudo-first-order kinetic model with a constant rate (k) of 0.0255 min-1. Therefore, due to the high performance of Fe3O4/ ZnO/Ag magnetic nanocomposite in the degradation of albumin as well as its easy synthesis and separation with an external magnetic field, it can be used as a suitable and environmentally friendly catalyst for the degradation of organic and resistant pollutants in the wastewater.

ZnO, single-doped (Co-ZnO, Cu-ZnO), and co-doped ZnO ((Co, Cu)/ZnO) were effectively synthesized by the citrate gel combustion technique. The samples were characterized by UV-visible diffuse reflectance spectroscopy (UV-vis-DRS), Fourier transforms infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence spectroscopy (PL). The average particle size was 30.33 nm as calculated from XRD patterns for (Co, Cu)/ZnO. UV-Vis absorption spectrum indicates that the co-doped ZnO exhibits increased visible light absorption compared to the undoped one.  The photoluminescence spectroscopy shows that the separation efficiency of photo-induced electrons and hole is enhanced by the co-doping strategy. (Co, Cu)/ZnO nanoparticles demonstrated a strong visible light response and high photocatalytic activity for Rhodamine B (RhB) degradation under irradiation by visible light (400-500 nm). The visible-light photocatalytic activity of the prepared  (Co, Cu)/ZnO may come about because of the incorporation of Co, Cu atoms in ZnO, photo-induced electron-hole pairs and extended the spectral response to the visible region. The antibacterial and antifungal activities of ZnO, Co-ZnO, Cu-ZnO, and (Co, Cu)/ZnO were studied respectively with Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative) ( bacterial strain) and  Aspergillus flavus, Candida albicans (fungal strain). The (Co, Cu)/ZnO enhanced the antimicrobial activity.

Water pollution is one of the serious main global concerns that affect humans and numerous people die due to various diseases caused by contaminated water because of the toxic and carcinogenic nature of dyes in effluents.  It is essential to develop an efficient and effective method for wastewater treatment using a highly active and reusable catalyst. Herein we report heterogeneous catalyst MgZrO3@Fe2O3@ZnO nanoparticles by sol-gel approach. They were characterized by UV-visible diffused reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive x-ray analysis (EDAX), and High-resolution transmission electron microscopy (HRTEM) and selected area diffraction. This characterization confirmed the structure of MgZrO3@Fe2O3@ZnO and also confirmed excellent photocatalytic activity for the decolorization of Nigrosin dye under ambient conditions. The 96±0.5 % degradation was observed within 60 min using 20 ppm Nigrosin dye solution with 0.2 g of MgZrO3@Fe2O3@ZnO core-shell nanoparticles. A mechanistic approach for photodegradation of dye was established by Liquid chromatography-mass spectrometry (LCMS) with the identification of numerous smaller fragment molecule

The photocatalytic degradation of methyl orange and Congo red dye was performed under the illumination of visible light (Philips 250Watt) as a source of photons. The complete distraction of the aromatic ring was ascertained by UV spectroscopic analysis. A decrease in dye concentration and an increase in the concentration of CO2 indicate dye mineralization. The behavior of this reaction was pseudo-first-order and the maximum photodecolorization efficiency was ~85.16% for Methyl orange and ~ 95.40 for Congo red in 120-150 min. at 30oC.

The current study aimed to synthesize nanoparticles of Zinc oxide (ZnO) using the extract of Acalypha indica leaves and their photocatalyst degradation and antibacterial properties were also measured. The biosynthesized nanoparticles were analyzed using XRD, UV-visible, FT-IR, and SEM with EDAX, DLS, PL, and Zeta potential analysis. The synthesized nanoparticles had a mean size of 16 nm measured by XRD which was highly pure, and their spherical shape was confirmed by SEM. The UV-visible confirmed that ZnO nanoparticles have a direct band gap energy is 3.34 eV. The measured zeta size and potential of synthesized nanoparticles were 46 nm and -27 mV, respectively, determined by the DLS technique can be considered moderately stable colloidal solutions. The FT-IR analysis confirmed the presence of functional groups in the leaf extract and the ZnO nanoparticles. The biosynthesized ZnO nanoparticles have a homogeneous spherical morphology and the average particle is 35 nm. The PL analyses performed on synthesized nanoparticles showed a sharp blue band at 362 nm, which was attributed to the defects of structure in ZnO crystals. During natural sunlight illumination, ZnO nanoparticles demonstrated notable degradation of the dye methyl blue (MB). At 90 min of illumination, the degradation efficiency achieved was 96 %. Antibacterial properties were observed for synthesized nanoparticles against four bacterial strains, including Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The highest zone of inhibition was observed against Escherichia coli (25.2 mm). Overall, these studies indicate that Acalypha indica is a good sell for planting, and has the greatest chance of being used to develop nanoparticles for protection against environmental pollution and human health.

The presence of various hazardous toxins such as Phenols, phthalates, pesticides, dyes, heavy metals, pharmaceutical waste, etc, is continuously increasing into the water bodies from different agricultural, industrial and domestic practices, which have brought the toxicity level to an alarming height. Often, these toxic compounds are quite stable in nature and the removal or degradation of these compounds is quite challenging, which further poses a significant threat to the environment. When it comes to enhance the efficiency of water purification and decontamination process, SnO2 nanoparticles offer great potential owing to their low concentration and large surface area. Over the past few years, SnO2 nanoparticles as a photocatalyst has garnered huge interest from the researcher community towards the photo-degradation of toxic pollutants present in the water bodies. Among various metal oxides, particularly SnO2 has been emerged as the most versatile material for doping of different transition metals due to its plethora of applications such as photocatalysis, energy harnessing, sensors, solar cells and optoelectronic devices. The pure and doped SnO2 has prominent significance due to its phenomenal catalytic and physicochemical properties such as chemically stable, inexpensive and non-toxic. This review explores and summarizes the progress of first and second transition metal series doping in SnO2 for its coherent application towards the degradation of water pollutants. We have emphasized the effect of different transition metal dopants used in the growth of SnO2 nanoparticles on the basis of their synthesis technique, source of irradiation used, nature of contaminations removed and obtained photodegradation efficiency.

TiO2-based nanomaterials are very effective for water and air purification and act as good antibacterial agents due to their unique physicochemical properties. TiO2 is a promising nanocatalyst because of its non-toxicity, chemical stability, and low cost. The wide band gap and rapid electron-hole recombination limit its performance which can be overcome by doping with metals and non-metal ions. Metal doping improves the trapping of electrons to inhibit electron-hole recombination and non-metal doping reduces the bandgap of TiO2. These doped TiO2 materials can be synthesized by different routes like the Sol-gel method, hydrothermal method, precipitation method, impregnation method, etc. Among these, the Sol-gel method is reported as the best and most accurate for the synthesis of TiO2 particles in the nano scale range. Because it allows the incorporation of dopant ions at the molecular level with homogeneity and high chemical purity. The structural, morphological, and optical properties of as-synthesized TiO2 nanocatalysts can be well characterized by XRD, SEM, EDX, FT-IR, UV Vis-DRS, TEM, BET, and PL. In this review article, we would like to discuss the advantage of the Sol-gel method over other preparative methods of TiO2 nanomaterials and experimental techniques related to their characterization.