Photocatalytic and biomedical investigation of green synthesized NiONPs: Toxicities and degradation pathways of Congo red dye

In this study the biomedical and catalytic ability of green synthesized nickel Oxide nanoparticles (NiONPs) was investigated. The extract of medicinal plant Tribulus terrestris were used to synthesized NiONPs. The as-synthesized NiONPs were in nano scale and were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Energy Dispersive X-ray spectroscopy (EDX). The synthesis of NiONPs was ensured with surface Plasmon resonance (SPR) at 425 nm and the strong EDX. The effect of different concentrations of plant extract on the size of NiONPs was evaluated. The HRTEM results showed particle size between 60 - 90 nm. The study showed that lesser the extract concentration, more spherical and small sized particles were obtained without aggregation. The biological applications of NiONPs were evaluated against different fungal species like Asper gillusflavus, Asper gillusfumigatus, Asper gillusniger and standard medicine Terbinafine. A. niger, A. flavus and A. fumigatus exhibited 57, 63 and 52 % inhibition compared with inhibition of the reference medicine which is 98, 100 and 100%. NiONPs have been shown to be more effective against gram-positive bacteria than gram-negative bacteria like E. Coli 9(±0.7) and S. aureus13 (±0.8). Moreover, antioxidant properties of the as-synthesized NiONPs were evaluated with 2, 2 diphenyl-1-picrylhydrazyl) (DPPH). The catalytic ability of green synthesized of NiONP was investigated for the degradation of Congo red dye (CR) as a hazardous environmentally contaminations in water. The biosynthesized NiONPs were found to be active catalytic for the degradation toxic dyes like CR. the catalytic activity of NiONPs can be explained by its small size compared with balk material. Mechanisms for CR degradation have been proposed. The Ecotoxicity of CR and components derived from dye was investigated with Ecological Structure Activity Relationship (ECOSAR) program

Operando Visualization of Produced Water Treatment by Electrocoagulation

Electrocoagulation (EC) involves the in-situ generation of metal hydroxide coagulant by the dissolution of the sacrificial metal anode and formation of hydroxyl ions at the cathode. Previous studies have shown that pH is a critical factor that directly affects the EC performance as the metal dissolution, the ionic speciation and equilibrium species, and metal hydroxide solubility are governed by the pH. In the present study, a combination of pH-sensitive fluorescent dyes, with different pKa, together with laser scanning confocal microscopy (LSCM), was employed to visualize the interfacial pH changes of EC in-operando. Quantification of interfacial pH in a wide pH range from ~1.5 to 8.5 with a high spatiotemporal resolution was achieved. The sucessful application of the method in EC provided new insights into the reaction mechanisms such as metal dissolution and gas evolution. The dynamics of the pH boundary layer within a few hundred microns of the electrode surface was monitored, and the effect of current density and flow rate was investigated. Furthermore, coupling the method for in-operando monitoring of interfacial pH with reflectance microscopy provided valuable information on the impact of operating conditions such as current type (DC or PR), current density, electrode material (iron or aluminum), the buffer capacity of the solution, and PR intervals (5 s to 60 s) on the interfacial pH, the morphology of electrode surface and formation of sludge. The interfacial pH in PR-EC oscillates in response to the changes in the direction of current flow, and is a function of the PR interval, and the buffer capacity of the solution. For both electrode materials, shear caused by hydrogen evolution contributes to removing the fouling layer off the electrode surface. Applying a current density of 16 mA cm?2 and 60 s PR intervals was found to reduce the amount of fouling for iron and aluminum electrodes while maintaining or improving the performance of the EC process and the lifetime of electrodes.Finally, the impact of the operating conditions on the sludge properties was investigated. The network strength of the sludge formed during EC treatment was studied using a rheometer. The sludge strength network is an essential factor for the separation steps after electrocoagulation. A weak network strength can lead to poor solid-liquid separation in settling tanks or blockage of flow channels in the filtration process. The network strength of the EC sludge formed with iron electrodes was found to be higher than that obtained with aluminum electrodes. When PR with 60 s intervals was used, a 70% increase in the sludge network strength was achieved with aluminum electrodes, while a similar network strength to DC was observed with iron electrodes. Although PR-EC was effective for removing the fouling layer from the electrode surface and enhancing the mechanical properties of the sludge, the frequency of PR should be chosen carefully based on the electrode material and the solution chemistry, in particular the type of contaminants and the buffer capacity. The present study provides valuable insights into implementing in-operando techniques to probe the dynamics of reaction involved in the electrocoagulation process and can readily be extended to other electrochemical systems

Sonochemical synthesis and characterization of Ho-Cu-O nanostructures and their application as photocatalyst for degradation of water-soluble organic pollutants under UV light

Water pollutants have been a significant concern in recent years. It is essential to use advanced materials that effectively reduce these pollutants. This work introduces Ho2Cu2O5/Ho2O3 nanocomposites as a novel catalyst for photodegradation of various water-soluble organic pollutants. First, Ho2Cu2O5/Ho2O3 nanocomposites were prepared via a simple and fast ultrasonic-assisted route. The chemical and morphological features of the as-synthesized sample were determined using VSM, FTIR, XRD, EDS, SEM, and TEM analysis. Also, the optical bandgaps and pore diameter were determined to be 3.1, 3.6 eV, and 12.74 nm via ultraviolet–visible diffuse reflectance spectroscopy and Brunauer-Emmett-Teller (BET) for Ho2Cu2O5 and Ho2O3, respectively. The findings revealed that the prepared nanocomposite could act as a photocatalyst for removing various organic pollutants from water. 93.01% and 92% of Eriochrome black T (ECBT) and Acid yellow (AY) were degraded under UV irradiation at optimum conditions after 120 min (0.03 g of photocatalyst and 10 ppm of pollutants). The kinetics of the ECBT removal was studied through the Langmuir-Hinshelwood model, and the apparent rate of the pseudo-first-order reaction (k = 0.03465 min−1) was obtained. The use of different scavengers made it clear that formation •O2– species were primarily responsible for the photodegradation of pollutants