Presence Of Organic Compounds Research Articles

Ammonium ion removal from aqueous solutions in the presence of organic compounds, using biochar from banana leaves. Competitive isotherm models

BackgroundIndustrial, e.g. food industrial and domestic wastewaters contain huge amount of compounds causing eutrophication, and should be removed with high cost during wastewater treatment. However, these compounds could be utilized as fertilizers too. Biochar can remove a wide range of pollutants from water, such as ammonium, which can be found in relatively high concentration in dairy wastewaters. However, adsorption performance may be affected by the presence of other wastewater pollutants. Thus, this study aims to determine the efficiency of biochar as an adsorbent of ammonium in aqueous solutions in the presence of some selected organic compounds of typical dairy wastewaters such as bovine serum albumin (BSA), lactose, and acetic acid. Methods: The biochar was produced from banana leaves at 300 °C, modified with NaOH, and characterized by Scanning Electron Microscope – Energy Dispersive X-Ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectra (FTIR) analysis, and specific surface area measurements. Batch experiments were carried out to investigate the ammonium adsorption capacity and the ion competitive adsorption mechanism. Significant Findings: Results show that the surface structure of the biochar derived from banana leaves is different from other biochars previously studied; although the specific surface area is not very considerable and despite having nitrogen within the elemental composition, the biochar studied is capable of adsorbing 2.60 mg NH4+/m2, the highest ammonium removal in 2 hours occurs at pH 9 and 500 mg biochar dose. Langmuir model in the monolayer phase analysis fits better for all scenarios and the maximum NH4+ adsorption capacity was 0.97 mg/g without organic compounds. In the multilayer adsorption phase, the isotherm model that best fits the data obtained is the Harkins-Jura model without organic compounds. The presence of organic compounds in the aqueous solution significantly impacts the adsorption of ammonium by biochar since it improves the adsorption capacity (1.132 mg/g BSA, 0.975 mg/g lactose, and 1.874 mg/g acetic acid). The Aranovich-Donohue isotherm model fitted the data obtained during ion competitive adsorption experiments well.

Deciphering the seasonal dynamics of microplastic morphotypes and associated co-contaminants along the northwest coast of India

In the present study, the northwest coast of India, bordering the Arabian Sea, was selected to evaluate the microplastic (MP) abundance. This is the first study to emphasize the effects of different seasons on MP distribution. The collected MPs were dried, segregated, and evaluated based on their morphotype, size, color, and polymer type. A total of 1756.6, 7326.6, and 202 particles/kg of sand were estimated in the pre-monsoon, monsoon and post-monsoon seasons, respectively, with a dominance of polypropylene (PP) type of plastic in the pre-monsoon and high-density polyethylene (HDPE) in monsoon and post-monsoon seasons. HDPE and PP collected MPs during the monsoon season were further characterized for associated contaminants. Metal absorbance was detected using SEM-EDX mapping and ICP-MS. The presence of organic compounds (OCs) was analyzed using GC-MS. MPs exhibit distinct associations with metals, among which the HDPE pellet morphotype exhibits a higher range of metal adsorption. Total 61 different OCs were associated with MPs. The HDPE pellets contained the highest amounts of hydrophobic organic compounds. PP pellets were found to contain triglycerides, fatty aldehydes, and alkaloids, along with HOCs. Among morphotypes, pellet forms of MPs were found to adsorb more contaminants. These co-contaminants infiltrate the study area through sewage runoff and shoreline debris deposition, subsequently interacting with MPs. Furthermore, the MP diversity was studied by employing the MP diversity integrated index, which suggests that most of the MP diversity was observed in the pre-monsoon period. The pollution load index employed an MP risk assessment, which presented a low degree of MP contamination. In contrast, the polymer hazard index was calculated as 21650.3 in post-monsoon, placing the area under the extreme danger category. It is evident from the data that the types of MP is more important than their number. Thus, MP morphotypes have importance in the adsorption of co-contaminants.

Phototrophic Fe(II) oxidation by Rhodopseudomonas palustris TIE-1 in organic and Fe(II)-rich conditions.

Rhodopseudomonas palustris TIE-1 grows photoautotrophically with Fe(II) as an electron donor and photoheterotrophically with a variety of organic substrates. However, it is unclear whether R. palustris TIE-1 conducts Fe(II) oxidation in conditions where organic substrates and Fe(II) are available simultaneously. In addition, the effect of organic co-substrates on Fe(II) oxidation rates or the identity of Fe(III) minerals formed is unknown. We incubated R. palustris TIE-1 with 2 mM Fe(II), amended with 0.6 mM organic co-substrate, and in the presence/absence of CO2 . We found that in the absence of CO2 , only the organic co-substrates acetate, lactate and pyruvate, but not Fe(II), were consumed. When CO2 was present, Fe(II) and all organic substrates were consumed. Acetate, butyrate and pyruvate were consumed before Fe(II) oxidation commenced, whereas lactate and glucose were consumed at the same time as Fe(II) oxidation proceeded. Lactate, pyruvate and glucose increased the Fe(II) oxidation rate significantly (by up to threefold in the case of lactate). 57 Fe Mössbauer spectroscopy revealed that short-range ordered Fe(III) oxyhydroxides were formed under all conditions. This study demonstrates phototrophic Fe(II) oxidation proceeds even in the presence of organic compounds, and that the simultaneous oxidation of organic substrates can stimulate Fe(II) oxidation.

Pore Fluid Dielectric Constant Effect on Geotechnical and Geo-Environmental Properties of Smectite and Kaolinite

ABSTRACT Organic compounds pose significant environmental concerns, including groundwater contamination. Clays are commonly used as liners to prevent contaminant permeation into the groundwater tables, necessitating an understanding of clay’s behavior in the presence of organic compounds. The presence of organic contaminants results in changes in the dielectric constant of pore fluid, which influences the interparticle energies and double layer thickness in the soil-pore fluid system. This study aims to elucidate the mechanisms of these changes by examining the response of smectite and kaolinite to variations in the dielectric constant. Experimental tests, including Atterberg limits, unconfined compression strength, water adsorption, sedimentation, pH, and XRD, were performed on clay samples at different concentrations of water-isopropyl alcohol mixtures. Results indicate that smectite exhibits higher Atterberg limits and water adsorption capacity compared to kaolinite. Smectite also shows more pronounced changes in response to decreasing dielectric constant. Conversely, changes in kaolinite’s behavior were attributed to variations in pore fluid viscosity and dipole moment. These findings emphasize the importance of considering viscosity and dipole moment alongside dielectric constant in predicting kaolinite behavior. Overall, this study enhances the understanding of how variations in pore fluid dielectric constant affect the geotechnical and geo-environmental behavior of smectite and kaolinite.

Controls on Mineral Formation in High pH Fluids From the Lost City Hydrothermal Field

AbstractAlthough the serpentinite‐hosted Lost City hydrothermal field (LCHF) was discovered more than 20 years ago, it remains unclear whether and how the presence of microbes affects the mineralogy and textures of the hydrothermal chimney structures. Most chimneys have flow textures comprised of mineral walls bounding paleo‐channels, which are preserved in inactive vent structures to a varying degree. Brucite lines the internal part of these channels, while aragonite dominates the exterior. Calcite is also present locally, mostly associated with brucite. Based on a combination of microscopic and geochemical analyses, we interpret brucite, calcite, and aragonite as primary minerals that precipitate abiotically from mixing seawater and hydrothermal fluids. We also observed local brucite precipitation on microbial filaments and, in some cases, microbial filaments may affect the growth direction of brucite crystals. Brucite is more fluorescent than carbonate minerals, possibly indicating the presence of organic compounds. Our results point to brucite as an important substrate for microbial life in alkaline hydrothermal systems.

Operando X-Ray Diffraction Studies of Co Oxide Model Catalysts during Alcohol Oxidation and Oxygen Evolution Reaction

Green energy technology involving hydrogen generation requires developing catalyst materials of commercial viability, good stability and high reactivity for the electrochemical water splitting. Transition-metal oxides such as Co3O4 are among the best precious-metal-free electrode materials for the anodic oxygen evolution reaction (OER) in alkaline electrolysis [1]. Moreover, these spinel-type transition metal oxides are an important class of catalysts for the selective oxidation of organic compounds. Previous in situ and operando surface X-ray diffraction studies of epitaxial Co oxide films by our group showed pronounced changes in the near-surface structure of these catalysts. In particular, a sub-nm CoOx(OH)y skin layer starts forming in the pre-OER potential range which is accompanied by a volume change of the Co3O4 lattice [2]. In a more recent work, where we systematically explored the relationship between the effective thickness of this skin layer and the OER activity, we found clear evidence that the entire skin layer serves as a three-dimensional reactive zone for the OER [3]. Since the skin layer formation already starts several 100 mV negative of the onset of the OER, it is not induced by the catalytic reaction itself, but rather reflects the oxides’ electrochemistry, and may thus be expected also for other electrocatalytic processes, especially other electrocatalytic oxidation reactions which occur in a similar potential range. These oxide materials are not only of interest for OER, but also for the electrochemical oxidation of other compounds, such as alcohols [4]. However, data on the oxides’ structure in the presence of organic compounds does not exist at present. Obtaining such data is of great interest for understanding the mutual influence of oxide-electrolyte interface structure and electrocatalytic activity. In addition, the vast majority of publications on Co oxide oxidation processes, in particular all in situ and operando studies, have been performed up to now at room temperature only, and, thus, the catalytic performance of these materials at higher temperatures remains unknown. As electrolyzers and industrial (electro-) catalytic processes typically operate at elevated temperatures, such data are of considerable interest. Here, we present results of first potential-dependent structural studies of epitaxial Co3O4(111) and CoOOH(001) films electrodeposited on Au(111) single crystal substrates during ethylene glycol oxidation (EG Ox) in 0.1 M NaOH solution and compare those with the behavior found on the same samples in EG-free electrolyte. Ethylene glycol oxidation is a highly suitable reaction for such studies, as it occurs at potentials prior to the onset of the OER [4]. The samples were investigated as a function of electrode potential and temperature by operando surface X-ray diffraction at beamline P23 of PETRA III, DESY. The EG Ox was studied by successively increasing the EG concentration from 0 to 0.1, 0.5 and 2 M, which allows direct quantitative comparison of the potential-dependent structural changes. These studies of the oxides’ structure and electrochemical reactivity were performed at different temperatures in the range of 25 - 70°C. In all cases significant skin layer formation and accompanying changes in the oxide lattice strain were observed. The structural data are correlated with the results of cyclic voltammetry and optical reflectivity measurements that were recorded in parallel with the X-ray diffraction measurements. Together, they provide insights into the potential-dependent evolution of the skin layer thickness and strain and into the stability of the oxides in dependence of EG concentration and temperature. First results indicate that at elevated temperatures larger skin layer thicknesses and strain changes occur. Furthermore, the structural properties recover completely upon cooling back down to room temperature, suggesting that these effects are highly reversible. In the presence of EG, the reversible skin layer formation and changes in the Co3O4 bulk lattice were also observed, even though these structural changes appear to be less pronounced under alcohol oxidation conditions, especially at higher EG concentration. These studies will contribute to an in-depth understanding of the near surface structure of these Co oxide thin films during liquid phase oxidation catalysis, which is a prerequisite for the design of new, abundant and superior catalysts based on transition metal oxides for catalytic selective oxidation processes.We acknowledge financial support by the Deutsche Forschungsgemeinschaft via special research area TRR 247, project B10 (project no. 388390466).[1] A. Bergmann et al., Nature Catalysis 2018, 1, 711 - 719[2] F. Reikowski et al., ACS Catal. 2019, 9, 3811 - 3821[3] T. Wiegmann et al., ACS Catal. 2022 [4] S. N. Sun et al, J. Electrochem. Soc. 2016, 163, H99

Uranium in Fluorite, a Case Study: The La Azul Fluorspar Deposit, Taxco, Guerrero, Mexico

Uranium can be found in the Earth’s crust in different reservoirs, with igneous rocks being the primary source of this element from which many types of secondary deposits are formed. Fluorspar deposits generally do not contain uranium, but in some cases, fluorite can carry both uranium in solid solutions and inclusions of uranium minerals. We studied the concentration (ICP-MS), composition (electronic microprobe), and spatial distribution (microscopy and auto-radiography) of elemental uranium and uranium minerals at different scales (microscopy and auto-radiography in fluorite from the La Azul fluorspar deposit (Taxco, Mexico) to assess the origin of uranium and its significance in this ore deposit. Auto-radiography images with the CR-39 detector were found to be impressive in their ability to elucidate uranium distribution at the millimeter scale. The limit between the solid solution of elemental uranium in natural fluorite and the appearance of uranium oxides as inclusions appeared to be between 20 μg g−1 and 40 μg g−1 bulk uranium concentration in this fluorspar ore. The maximum concentration of U in fluorite from the La Azul deposit was about 100 μg g−1. Using Raman spectroscopy and microprobe analysis, we identified the micro-inclusions of uranium minerals as uraninite (of the pitchblende variety); its composition suggested a hydrothermal origin for this fluorspar deposit. We also calculated a chemical age that can be compared with the previously published regional geology and isotopic (U-Th-Sm)/He ages in fluorite. Micro-thermometric studies of fluid inclusions were carried out in different samples of uranium-rich fluorite to identify the nature and origin of the mineralizing fluid and the precipitation mechanisms of uranium minerals. We concluded that the uranium-rich fluorite precipitated in the initial phases of mineralization from a reducing fluid, with low salinity (<8% NaCl eq.) and an intermediate temperature (110–230 °C), and that the presence of organic compounds and sulfides (mainly pyrite) favored the simultaneous precipitation of uraninite (pitchblende variety) and fluorite.

Zinc oxide nanorod/rutin modified electrode for the detection of Thiourea in real samples

In this work, a novel electrochemical detection strategy was developed based on a metal-organic framework of zinc oxide nanorod nanoparticles and rutin for selective screening of Thiourea as toxic chemicals. The zinc oxide nanorod were synthesized by following direct chemical precipitation methods and characterized by X-ray diffraction and X-ray photoelectron spectroscopy analysis. The surface of modified electrodes was also characterized by field emission scanning electron microscopes, energy-dispersive X-ray spectroscopy, and attenuated total reflectance flourier transform infrared spectroscopy. Furthermore, the electrochemical activity of the developed sensor was tested by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The modified electrode showed outstanding electro-catalytic activity towards the detection of Thiourea in phosphate buffer saline at a high pH level of 12.0. The proposed sensor showed a linear range of linearity in a concentration ranging from 5.0 × 10−6 - 900 × 10−6 molL−1 and a detection limit of 2.0 × 10−6 molL−1. Moreover, the selectivity of the developed electrochemical sensor was investigated for the detection of Thiourea in the presence of organic compounds and a group of anions. Furthermore, the proposed strategy demonstrated an excellent recovery value in the spiked farmland water and fruit juice sample.

Determining heavy metal concentrations and physicochemical properties in wastewater

Wastewaters are frequently harmful to both the environment and human health since they are both directly and indirectly released into surface waters. The aim of this study was to determine physicochemical properties and to assess the levels of heavy metals in wastewater. Wastewater samples were collected from Koka and Mojo from the Oromia region, Ethiopia. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used to determine the concentration of these heavy metals. The conductivity of wastewater obtained from the Mojo and Koka sites ranged from 1141.33 to 1498.32µS/cm and 1066.33 to 1243.72µS/cm, respectively. The maximum and minimum BOD effluent from Mojo and Koka sites were 1044.78mg/L and 794.73mg/L, and 883.00mg/L and 772.67mg/L, respectively. The COD value was found to range between 1466.08mg/L and 1615.38mg/L in the Mojo area and 1352.65mg/L to 1530.83mg/L in the Koka area, respectively. High BOD levels are a sign of contamination and could indicate a lack of oxygen for living things. In every one of the sample sites, it exceeds the recommended level. High COD levels suggest hazardous conditions and the presence of organic compounds that are resistant to biological processes. The maximum TDS of the effluents, which is more than the recommended limit, were found to be 2417.08mg/L and 2317.06mg/L in Mojo and Koka areas, respectively. Overall concentrations of heavy metals (As, Pb, B, Zn, Cd Hg, Cu, Ni, Co, Fe, Mn and Cr) in mg/L were found to be in the permissible range except for mercury (Hg). The wastewater had heavy metal Hg that was higher than the limits advised by the WHO and US EPA. The studies’ findings imply that the effluents are harmful by nature and need considerable treatment before being released into the ecosystem on land.

Corrosion Resistance of Steel S355MC in Crude Glycerol

Corrosion is the degradation of materials in oxidizing environments. In aqueous solutions, it is initiated by the surface reaction of the metallic material with the surrounding electrolyte. The corrosion rate of metals can be significantly reduced by the presence of organic compounds. Crude glycerol is an organic by-product of biodiesel, soap, and fatty acid production. It is produced in substantial amounts through transesterification. Crude glycerol contains several impurities and has low economic value. Its disposal in the environment is unwanted and potential applications need to be explored. In the present short communication, steel corrosion in crude glycerol has been investigated for the first time. The corrosion behavior of low-alloy structural steel S355MC in non-purified crude glycerol was studied by electrochemical methods. The results were compared with the use of tap water. The open-circuit potential (OCP) of S355MC in crude glycerol was more negative compared with that of tap water. The OCP was stable over time, indicating the rapid passivation of the steel substrate. The corrosion resistance was further studied by electrode polarization. On the polarization curve of S355MC in crude glycerol, a wide passivation region was found. Furthermore, the corrosion rate was 2.2 times smaller compared with that of tap water. The surface exposed to tap water was significantly degraded by red rust. The surface of S355MC after exposure to crude glycerol, on the other hand, was less affected by corrosion and covered with a protective layer. The results demonstrate a significant corrosion-inhibiting activity of crude glycerol that could be utilized in various technologies.

Photocatalytic degradation of multi-organo-sulfur industrial wastewater using TiO2 produced from modified sulfate process

This study focuses on the photocatalytic degradation of industrial wastewater containing organic pollutants using modified sulfate process derived-titanium dioxide (mspd-TiO2). The mspd-TiO2 is duly characterized and compared with commercially available Degussa P-25 TiO2. The industrial effluent is assayed for pollutants and is found to have high sulfur content (S = 11.37 ± 0.15 %) and the presence of organic compounds. The powder studied, mspd-TiO2, demonstrated a desirable efficiency in treating the industrial wastewater, as the COD value decreased from 7680 mg/l to 320 mg/l after degradation. Sulfur Black and Acid Orange 7, both of which are in the industrial effluent, are degraded using mspd-TiO2. The efficiency of mspd-TiO2 in degrading the pollutants is 80 ± 3 % for Sulfur Black and 72 ± 3 % for Acid Orange7 within 2 h. This is achieved at a loading of 150 g/l TiO2 at pH 5 (k = 0.0125 ± 0.002 min−1). Results indicate that the catalyst remained structurally stable after degradation. The mspd-TiO2 exhibited decreased activity during the reusability test due to loss of activation sites, particle aggregation, and mass loss. Overall, significant degradation of the pollutants is observed. This study demonstrates the potential of mspd-TiO2 for efficient and cost-effective treatment of industrial wastewater containing complex sulfur-containing organic pollutants.

Sorption of lead on cementitious materials in presence of organics

Commercial cementitious material, hydrated cement pastes of type CEM I and CEM III, and a synthetic cementitious phase CSH (calcium-silicate-hydrates) with a Ca/Si ratio equal to 1.0, 1.2, and 1.4 were used in the study of lead sorption. Kinetic and equilibrium experiments were performed under different conditions, namely liquid to solid phase ratio and the presence of organic compounds (EDTA, phthalate). The duration of equilibrium experiments was determined based on kinetic experiments, 1 week for calcium-silicate-hydrates and 3 weeks for hydrated cement paste. Equilibrium experiments were evaluated using the distribution ratio Rd and sorption isotherms. For both hydrated cement pastes, Rd’s in the range 102–103 L kg−1 were found while for calcium-silicate-hydrates the distribution ratio values were an order of magnitude higher under comparable conditions. The difference in the studied cementitious materials was also manifested in the shape of the sorption isotherm, while the behavior of calcium-silicate-hydrates can be fitted linearly and therefore by the Kd-model, for hydrated cement paste as more complex cement material it is necessary to use a non-linear isotherm description. The effect of organic matter, represented here by EDTA and phthalate, described by the sorption reduction factor SRF was more apparent for calcium-silicate-hydrates, where its value was always higher than one and reached up to 500. On the contrary, for hydrated cement paste CEM I and CEM III, all determined SRFs were less than 1.

Comparative Study on Carbon Erosion of Nickel Alloys in the Presence of Organic Compounds under Various Reaction Conditions.

The processes of carbon erosion of nickel alloys during the catalytic pyrolysis of organic compounds with the formation of carbon nanofibers in a flow-through reactor as well as under reaction conditions in a close volume (Reactions under Autogenic Pressure at Elevated Temperature, RAPET) were studied. The efficiency of the ferromagnetic resonance method to monitor the appearance of catalytically active nickel particles in these processes has been shown. As found, the interaction of bulk Ni-Cr alloy with the reaction medium containing halogenated hydrocarbons (1,2-dichloroethane, 1-iodobutane, 1-bromobutane) results in the appearance of ferromagnetic particles of similar dimensions (~200-300 nm). In the cases of hexachlorobenzene and hexafluorobenzene, the presence of a hydrogen source (hexamethylbenzene) in the reaction mixture was shown to be highly required. The microdispersed samples of Ni-Cu and Ni-Mo alloys were prepared by mechanochemical alloying of powders and by reductive thermolysis of salts-precursors, accordingly. Their interaction with polymers (polyethylene and polyvinyl chloride) under RAPET conditions and with ethylene and 1,2-dichloroethane in a flow-through reactor are comparatively studied as well. According to microscopic data, the morphology of the formed carbon nanofibers is affected by the alloy composition and by the nature of the used organic substrate.

Cellulose degradation products and high ionic strength enhance the retardation of strontium in hydrated cement paste

The present concept for the disposal of some low- and all intermediate-level radioactive waste in the United Kingdom involves grouting with cement in steel drums and placement in a geological facility. The vaults would then be backfilled with low strength, high porosity cement-based materials designed to promote a pervasive, alkaline environment in which many of the radioactive species present are sparingly soluble. This work investigates the interaction of strontium with such a backfill under both diffusive and advective conditions given the potential significance of the fission product 90Sr. An important characteristic of the United Kingdom waste inventory is the abundance of organic compounds, including cellulosic materials; consequently, the experiments were repeated with products of alkaline cellulose degradation. Additional experiments were performed at high ionic strength simulating anticipated changes in the salinity of the groundwater. The effective diffusivity (De) of strontium in the absence of the organic compounds ranged between 5.5 × 10−11 and 8.5 × 10−11 m2 s−1, with a distribution coefficient (Rd) of between 2.8 × 10−3 and 3.1 × 10−3 m3 kg−1. The presence of organic compounds and/or an increase of ionic strength enhanced the retardation of strontium. The results indicate that the retention of strontium by hydrated cement paste occurs via a reversible ion exchange mechanism rather than mineralisation and is promoted by decalcification of the calcium silicate hydrate phases.

Effects of vegetables and fruit with varying physical damage, fungal infection, and soil contamination on stability of aqueous ozone

The application of aqueous solutions of ozone for surface disinfection is an effective novel green technology with a potential for replacing the use of persistent chemicals in postharvest treatments. However, successful disinfection requires certain levels of ozone to be maintained throughout the process. The decay rates of aqueous ozone were found to vary with the presence of different fruit and vegetables commodities (apples, carrots, onions, celeriac, and pears). Pure aqueous ozone had a half-life of 3200 s, whereas the half-life of ozone was found to range with increasing cross-cut areas between 2177 and 291 s for apples, 573 and 345 s for carrots, 541 and 113 s for onions, 2800 and 253 s for pears, and 362 and 165 s for celeriac. With soil particles present, the ozone half-life dropped to 59 s for celeriac. Parallel measurements reported strong to moderate effect of soil particles (51–626 s, 10 g soil/L ozonated water), and naturally occurring fungi (850–2294 s, 0.25 g fungi mix/L ozonated water) on ozone half-life. In summary, presence of organic compounds, notably by damaged commodities, increase ozone decay and illustrate the need to correctly identify important ozone-depleting parameters, which is crucial for understanding the efficiency of ozone-based washing systems.

The impact of lower quality water on soiling removal from photovoltaic panels

Soiling, bird droppings, and dust accumulation on the surface of photovoltaic cells, can reduce the solar energy absorption and produce power losses. In solar plants where soiling is a problem, the use of low quality water in lieu of typically used demineralized water could conserve fresh water. Soiling was studied in a group of 264 photovoltaic panels, facing due south with a tilt angle of 32°, located at the West Yard of the City of Las Vegas, Nevada. The panels were grouped into six independent sections and each section was manually washed eight times during 302 days using different cleaning methods. The results show that dust did not seem to have a great effect on the system performance, with the control group experiencing only a 1.88% reduction in mean efficiency due to dust accumulation. Washing with distilled water recovered the mean normalized system efficiency approximately 1.32%, followed by treated wastewater (0.92%), treated wastewater with surfactant (0.73%), vacuum cleaner (0.27%), and groundwater (0.24%). The dust composition analysis indicated the dust particles identified on the surface of the photovoltaic panels were the same from the ground or caused by the light vehicular traffic. Pyrolysis-GC/MS identified that the presence of organic compounds on the surface of the PV panels was related to the local suspended soil, pollen, and vaporized cooking oils. The dissolved minerals in the wastewater and in the groundwater, at this location, negatively impact the performance of the system and can be considered an inefficient cleaning method.

Design and modeling of diazinon degradation in hydrous matrix by Ni-doped ZnO nanorods under ultrasonic irradiation: process optimization using RSM (CCD), kinetic study, reaction pathway, mineralization, and toxicity assessment.

In first, the Ni-doped ZnO nanorods used as an appeal sonocatalyst was synthesized through co-precipitation method. Afterwards, the crystalline structure, functional groups, surface morphology, and elemental composition were characterized by a set of analysis. Removal of diazinon ((DZ) as a renowned pesticide) was investigated using sonocatalytic performance of US/Ni-doped ZnO system. In this empirical study, response surface methodology (RSM) based central composite design (CCD) was applied for optimization of operational factors. Under the optimum conditions such as initial pH = 5, initial DZ concentration = 15mg L-1, sonocatalyst dosage = 1g L-1, and in the presence of organic compounds (oxalic acid, humic acid, and folic acid) = 3mg L-1, the sonocatalytic degradation of DZ after 15min was 82.29%. The F-value (6.64) and P-value (< 0.0001) for DZ degradation in the quadratic model imply the proposed model was significant. A-factor (pH) considers as a prominent factor owing to having the highest F-value. In addition, the sonocatalytic data in this study exhibited valid fitting for the first order kinetic model (R2 > 0.98). After six consecutive cycles, the Ni-doped ZnO nanorods could be recyclable for sonocatalytic degradation of DZ. The five main compounds produced during the US/Ni-doped ZnO embracing 2-isopropyl-6-methyl-4-pyrimidinol (IMP), diethyl phosphonate, diazoxon, hydroxyldiazinon, and diazinon methyl ketone are formed in the path of DZ degradation. OFAT style also revealed 99.99% of DZ degradation with 73.26% of mineralization rate in optimum status. The Ni-doped ZnO presented agreeable sonocatalytic facility in the refinement of real water and wastewater matrix. Finally, the results of toxicity evaluation (Daphnia magna) in the sonocatalytic degradation of DZ (by US/Ni-doped ZnO system) showed that the toxicity of the DZ solution lessened under US waves (LC50 and TU 48h equal to 36.472 and 2.741 volume percent, respectively).

A Review: TiO2 based photoelectrocatalytic chemical oxygen demand sensors and their usage in industrial applications

• PeCOD is a well-established method for the determination of chemical oxygen demand in water. • The design and optimized operation of an industrial TiO 2 based PeCOD device is discussed for the first time. • Photocatalytic systems generally rely on cycling between samples and calibration stages, requiring high stability and repeatability. The increase in global population, industrialization and need for water security has fostered a demand for novel technologies related to water treatment and purification. The oxygen demand of a given water matrix can provide useful information on the presence of organic compounds within a sample and can inform decisions on water use and treatment. Traditional oxygen demand measures are time consuming and require the use of harmful reagents. TiO 2 -based photoelectrochemical oxygen demand (PeCOD) methods offer a faster, more efficient, and accurate alternative to traditional analysis processes. These methods use TiO 2 -mediated photoelectrocatalysis (PEC) to oxidize organic contaminants. This paper reviews the recent synthesis methods of TiO 2 nanomaterials with respect to electrode preparation in COD sensors, fundamentals of TiO 2 photo/photo-electro-catalysis, TiO 2 based PeCOD sensors, and PeCOD sensor system cell design. PEC combines photocatalysis with electrochemical methods, which result in improved photocatalytic performance in a variety of applications. TiO 2 based PeCOD sensors are promising due to their intrinsic low cost, non-toxicity, chemical stability, and availability in sensing applications. Here in this paper, an innovative PeCOD sensor system cell design system is demonstrated. This review paper aims to provide a scientific and technical overview of TiO 2 PeCOD sensor systems implementable for large-scale environmental, soil, and gas sensing applications.

Effective removal of organics from Bayer liquor through combined sonolysis and ozonation: Kinetics and mechanism

The presence of organic compounds in the waste liquor is of serious environmental concern that has plagued the development of alumina industry (Bayer Process). The present work attempts to develop a green and efficient process for removal of organics utilizing combined effect of sonolysis and ozonation (US/O3). The effects of reaction duration, ozone concentration and ultrasonic power are assessed for sonolysis (US), ozonation (O3) and combination of sonolysis and ozonation (US/O3). The optimal conditions for US/O3 treatment system is identified to be a reaction duration of 7 h, ozone concentration of 7.65 g/h, and ultrasonic power of 600 W. The total organic carbon (TOC) removal and decolorization are 60.13% and 87.1%, respectively. The process can be scaled-up to industrial scale, which could potentially serve to be a convenient, safe and sustainable alternative to the exisiting treatment technologies. Additionally, the treated waste water can be reused contributing to an improvement in the overall economics.

Assessment of Bilge Water Degradation by Isolated Citrobacter sp. and Two Indigenous Strains and Identification of Organic Content by GC-MS

Bilge water is oily saline wastewater accumulated on the hull at the bottom of a vessel, generated from leakage from pipes and engines and wash-down freshwater containing cleaning solvents. The present study focused on isolating microorganisms from oil-contaminated sites and indigenous species from raw bilge water and assessment of their ability to biodegrade bilge water. Using phenanthrene as a carbon source Citrobacter species was isolated from oil-contaminated sites and its optimum growth condition was found. The results indicated significant tolerance of the bacterium which presented great biodegradation ability for the tested carbon source. At high salinity (33 g L−1 of NaCl), sufficient phenathrene removal was achieved (81%), whereas variation of pH from 5 to 10 did not affected the survival of the microorganism. Regarding the effect of temperature and nutrients, Citrobacter sp. was better adapted at 30 °C, while lack of nutrients presented a negative impact on its growth. Halomonas and Exiguobacterium sp. were isolated from real bilge water using phenanthrene and phenol as a carbon source. The isolated strains independently exposed to high and low range bilge water pointed out around 83% and 53% chemical oxygen demand (COD) removal, respectively. Analysis of untreated bilge water by gas chromatography-mass spectrometry (GC-MS) was carried out, and the results confirmed the presence of organic compounds having a high similarity with Heptane, N-hexadecanoic acid, Methyl isobutyl Ketone and 1-butoxy-2-propanol. Chromatographic analysis of treated bilge water after exposure to isolated strains indicated the existence of new compounds. These metabolites presented high similarity with N-hexadecanoic, methyl ester, N-hexadecanoic and Octadecanoic acid methyl ester.