Electrochemical Determination of Famotidine in Real Samples Using rGO/Cu2O Nanocomposite Modified Carbon Paste Electrode

Here, we developed a sensitive electrochemical sensor for famotidine (FAT) using Cu2O nanoparticles and reduced graphene oxide (rGO) as a sensing platform. The Cu2O nanoparticles and rGO were synthesized through a simple process and characterized by versatile analytical methods. The prepared Cu2O nanoparticles and rGO were taken to modify the carbon paste electrode (Cu2O/rGO/CPE) and developed for the electrochemical analysis of the FAT at pH 6.0. Cu2O/rGO/CPE showed superior electrocatalytic activity for detecting FAT, attributed to the high surface area of rGO and the electrocatalytic properties of Cu2O nanoparticles. The designed FAT sensor exhibited two linear ranges from 0.1-3 µM and 3-50 µM with a detection limit of 0.08 µM (S/N=3) using a differential pulse voltammetry. The proposed sensor also showed a repeatable and stable response over one month with negligible interference from usual organic and inorganic species. The sensor was also validated measuring FAT in real samples (urine, serum and pharmaceutical tablet) with good recovery values from 99.6 to 110.9%.

Enhanced Photocatalytic Performance in Chromium(VI) Reduction and Dye Degradation using Sn3O4/SnS2 Nanocomposite and Mechanism Insight

Detection of residual organic and inorganic species in water bodies including drinking water has led to developing strategies for their removal. Here we report a very efficient method of photoreduction of Cr (VI) and photodegradation of methylene blue dye in aqueous medium using Z-scheme heterojunction based Sn3O4/SnS2 solar photocatalyst. The photocatalyst is synthesized by hydrothermal route and it is thoroughly characterized in terms of its structural, compositional, morphological and optical properties. About 100 % of Cr (VI) reduction in 60 min and 99.6 % of methylene blue degradation in 90 min is achieve under sunlight exposure at a photocatalytic rate of 0.066 min-1 and 0.043 min-1, respectively. The total organic carbon estimation of the post-degradation reaction medium corresponded to 85.1 % (MB) mineralization. The photocatalytic degradation is attributed to in-situ generation of reactive oxygen species (ROS) e.g., superoxide radicals, hydroxide radicals, and the role of ROS towards reduction and degradation of Cr (VI) and MB respectively, is confirmed from ROS scavenging studies. The dye degradation mechanism has been discussed by analyzing the degradation products via UPLC-Q-Tof-MS. The photocatalytic degradation of methylene blue by Sn3O4/SnS2 nanocomposites is significantly enhanced as compared to SnS2 photocatalyst, attributed to Z-scheme heterojunction and the charge carrier mobility.

Recent Advances in the Oxone-Mediated Synthesis of Heterocyclic Compounds

Oxone is a commercially available oxidant, composed of a mixture of three inorganic species, being the potassium peroxymonosulfate (KHSO5) the reactive one. Over the past few decades, this cheap and environmentally friendly oxidant has become becoming a powerful tool in organic synthesis, being extensively employed to mediate the construction of a plethora of important compounds. This review summarizes the recent advances in the Oxone-mediated synthesis of N-, O- and chalcogen-containing heterocyclic compounds, through a wide diversity of reactions, starting from several kinds of substrate, highlighting the main synthetic differences, advantages, the scope and limitations.

Spatiotemporal Variation on Water Quality and Trophic State of a Tropical Urban Reservoir: A Case Study of the Lake Paranoá-DF, Brazil

Nutrient enrichment and eutrophication are among the main problems that lead to the deterioration of water quality in lakes and reservoirs. In this study, spatial and temporal variations in the concentrations of organic and inorganic species of nitrogen and phosphorus in the water column of Lake Paranoá-DF (Brazil) were evaluated between 2016 and 2017. Seasonality was the main factor in the variations in concentrations of the investigated parameters. Additionally, we found differences in behavior for different nutrients and other variables that indicate different main sources of each nutrient as well as different biogeochemical processes predominating in each season. For example, the electrical conductivity (EC), dissolved silicon, PO43−, and NO3− showed mean concentrations significantly higher in the rainy season, indicating greater inputs in these periods (which is in part related to increasing soil leaching and runoff). Agricultural activities were the main source of NO3− and wastewater treatment plants (WWTP) proved to be the main source of nutrients, mainly NH4+ and all forms of phosphorus. These two allochthonous sources are also the determining factors of the trophic state and the degradation of the water quality of Lake Paranoá. The lake is in the transition process from a mesotrophic to a eutrophic condition.

One-Step Multi-Doping Process for Producing Effective Zinc Oxide Nanofibers to Remove Industrial Pollutants Using Sunlight

Doping processes for optical materials are one of the driving forces for developing efficient and clean technologies for decontamination of aquatic effluents through lowering their band gap energy to become effective in sunlight. The current study has used a non-conventional technique for doping zinc oxide by multi metals, non-metals and organic dyes through a one-step process. In this trend, Zn-Al nanolayered structures have been used as hosts for building host–guest interactions. Organic dyes that have inorganic species of iron, nitrogen and sulfur have been used as guests in the intercalation reactions of Zn-Al layered double hydroxides. By intercalating green dyes, organic–inorganic nanohybrids were formed as nanolayered structures with expanding interlayered spacing to 2.1 nm. By changing the concentration of green dyes and thermal treatment, series of nanofibers and nanoplates of zinc oxides were formed and doped by aluminum, iron and sulfur in addition to colored species. The optical properties of the multi-doped zinc oxide indicated that it became suitable for solar applications because its band gap energy decreased from 3.30 eV to 2.80 eV. The experimental and kinetic results of the multi-doped zinc oxide concluded that the colored pollutants were effectively removed during 50 min of sunlight irradiation.

Insight into PM_2.5 sources by applying positive matrix factorization (PMF) at urban and rural sites of Beijing

This study presents the source apportionment of PM2.5 performed by positive matrix factorization (PMF) on data presented here which were collected at urban (Institute of Atmospheric Physics – IAP) and rural (Pinggu – PG) sites in Beijing as part of the Atmospheric Pollution and Human Health in a Chinese megacity (APHH-Beijing) field campaigns. The campaigns were carried out from 9 November to 11 December 2016 and from 22 May to 24 June 2017. The PMF analysis included both organic and inorganic species, and a seven-factor output provided the most reasonable solution for the PM2.5 source apportionment. These factors are interpreted as traffic emissions, biomass burning, road dust, soil dust, coal combustion, oil combustion, and secondary inorganics. Major contributors to PM2.5 mass were secondary inorganics (IAP: 22 %; PG: 24 %), biomass burning (IAP: 36 %; PG: 30 %), and coal combustion (IAP: 20 %; PG: 21 %) sources during the winter period at both sites. Secondary inorganics (48 %), road dust (20 %), and coal combustion (17 %) showed the highest contribution during summer at PG, while PM2.5 particles were mainly composed of soil dust (35 %) and secondary inorganics (40 %) at IAP. Despite this, factors that were resolved based on metal signatures were not fully resolved and indicate a mixing of two or more sources. PMF results were also compared with sources resolved from another receptor model (i.e. chemical mass balance – CMB) and PMF performed on other measurements (i.e. online and offline aerosol mass spectrometry, AMS) and showed good agreement for some but not all sources. The biomass burning factor in PMF may contain aged aerosols as a good correlation was observed between biomass burning and oxygenated fractions (r2= 0.6–0.7) from AMS. The PMF failed to resolve some sources identified by the CMB and AMS and appears to overestimate the dust sources. A comparison with earlier PMF source apportionment studies from the Beijing area highlights the very divergent findings from application of this method.

INNOVATIVE COMPOSITE SORBENTS FOR ORGANIC AND INORGANIC POLLUTANTS REMOVAL FROM AQUEOUS SOLUTIONS IN LANDFILL LEACHATES

The study reveals the development of appropriate innovative sorbents based on clay material for arsenic and p-nitrophenol sorption using iron oxy-hydroxide and surfactant modification. Natural and manufactured clay were chosen for comparison of modification efficiency to obtain the best sorption results for As (V) and p-nitrophenol. Obtained results indicate that modification of clay with iron compounds and various surfactants significantly improve the sorption capacity of newly developed materials used for sorption of inorganic and organic compounds from aqueous solutions in landfill leachates.Natural clay minerals have received a lot of attention as potential sorbents, because of their abundance, cost-effectiveness, high sorption and ion-exchange properties [1]. Clay minerals can be modified using different approaches to obtain innovative materials for application as sorbents in the removal of inorganic and organic pollutants from leachates, wastewater, groundwater and soil [2, 3]. Modification with surfactants improves hydrophobization needed if interaction with low polarity organic molecules is necessary, but chemical modification with inorganic species, e.g., hydrated iron supports the physical improvement of sorption and ion exchange process in order to benefit the treatment of media from inorganic pollutants [4]. Materials achieved better properties for specific remedial applications regarding heavy metals and metalloids, prepared organoclays from hydrophilic montmorillonite by intercalating cationic or nonionic surfactants can interact with organic molecules of differing polarity and serve as immobilizers for organic molecules and toxicants, e.g., phenols and NOCs. Further studies will reveal improved properties to benefit landfill leachate treatment, wastewater engineering and environmental remediation industries.

Traceable PM2.5 and PM10 Calibration of Low-Cost Sensors with Ambient-like Aerosols Generated in the Laboratory

This work builds upon previous efforts at calibrating PM (particulate matter) monitors with ambient-like aerosols produced in the laboratory under well-controlled environmental conditions at the facility known as PALMA (Production of Ambient-like Model Aerosols). In this study, the sampling system of PALMA was equipped with commercial PM2.5 and PM10 impactors, designed according to the EN 12341:2014 standard, to select different aerosol size fractions for reference gravimetric measurements. Moreover, a metallic frame was mounted around the PM impactor to accommodate up to eight low-cost PM sensors. This sampling unit was placed at the bottom of the 2-meter-long aerosol homogenizer, right above the filter holder for the reference gravimetric measurements. As proof of principle, we used the upgraded PALMA facility to calibrate the new AirVisual Outdoor (IQAir, Goldach, Switzerland) and the SDS011 (InovaFitness, Jinan, China) low-cost PM sensors in a traceable manner against the reference gravimetric method according to the EN 12341 standard. This is the first time that PM2.5 and PM10 calibrations of low-cost sensors have been successfully carried out with complex ambient-like aerosols consisting of soot, inorganic species, secondary organic matter, and dust particles under controlled temperature and relative humidity.

Chemical Composition and Source Apportionment of Total Suspended Particulate in the Central Himalayan Region

The present study analyzes data from total suspended particulate (TSP) samples collected during 3 years (2005–2008) at Nainital, central Himalayas, India and analyzed for carbonaceous aerosols (organic carbon (OC) and elemental carbon (EC)) and inorganic species, focusing on the assessment of primary and secondary organic carbon contributions (POC, SOC, respectively) and on source apportionment by positive matrix factorization (PMF). An average TSP concentration of 69.6 ± 51.8 µg m−3 was found, exhibiting a pre-monsoon (March–May) maximum (92.9 ± 48.5 µg m−3) due to dust transport and forest fires and a monsoon (June–August) minimum due to atmospheric washout, while carbonaceous aerosols and inorganic species expressed a similar seasonality. The mean OC/EC ratio (8.0 ± 3.3) and the good correlations between OC, EC, and nss-K+ suggested that biomass burning (BB) was one of the major contributing factors to aerosols in Nainital. Using the EC tracer method, along with several approaches for the determination of the (OC/EC)pri ratio, the estimated SOC component accounted for ~25% (19.3–29.7%). Furthermore, TSP source apportionment via PMF allowed for a better understanding of the aerosol sources in the Central Himalayan region. The key aerosol sources over Nainital were BB (27%), secondary sulfate (20%), secondary nitrate (9%), mineral dust (34%), and long-range transported mixed marine aerosol (10%). The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analyses were also used to identify the probable regional source areas of resolved aerosol sources. The main source regions for aerosols in Nainital were the plains in northwest India and Pakistan, polluted cities like Delhi, the Thar Desert, and the Arabian Sea area. The outcomes of the present study are expected to elucidate the atmospheric chemistry, emission source origins, and transport pathways of aerosols over the central Himalayan region.

Oxidative Degradation of Tetracycline by Magnetite and Persulfate: Performance, Water Matrix Effect, and Reaction Mechanism

This study presents a strategy to remove tetracycline by using magnetite-activated persulfate. Magnetite (Fe3O4) was synthesized at high purity levels—as established via X-ray diffractometry, transmission electron microscopy, and N2 sorption analyses—and tetracycline was degraded within 60 min in the presence of both magnetite and persulfate (K2S2O8), while the use of either substance yielded limited degradation efficiency. The effects of magnetite and persulfate dosage, the initial concentration of tetracycline, and the initial pH on the oxidative degradation of tetracycline were interrogated. The results demonstrate that the efficiency of tetracycline removal increased in line with magnetite and persulfate dosage. However, the reaction rate increased only when increasing the magnetite dosage, not the persulfate dosage. This finding indicates that magnetite serves as a catalyst in converting persulfate species into sulfate radicals. Acidic conditions were favorable for tetracycline degradation. Moreover, the effects of using a water matrix were investigated by using wastewater treatment plant effluent. Comparably lower removal efficiencies were obtained in the effluent than in ultrapure water, most likely due to competitive reactions among the organic and inorganic species in the effluent. Increased concentrations of persulfate also enhanced removal efficiency in the effluent. The tetracycline degradation pathway through the magnetite/persulfate system was identified by using a liquid chromatograph-tandem mass spectrometer. Overall, this study demonstrates that heterogeneous Fenton reactions when using a mixture of magnetite and persulfate have a high potential to control micropollutants in wastewater.