Oxidative Degradation of Pharmaceutical Waste, Theophylline, from Natural Environment

The elimination of organic contaminants from natural resources is extremely important to ensure their (re-)usability. In this report, the degradation of a model pharmaceutical compound, theophylline, is compared between natural and laboratory-controlled environments. While the concentration of H2O2 variably affected the degradation efficiency (approximately from 8 to 20 min for complete degradation) in the photo-irradiation experiments, the inorganic compounds (NaNO3, KH2PO4 and ZnSO4) present in the medium seemed to affect the degradation by scavenging hydroxyl radicals (•OH). The end-product studies using high-resolution mass spectrometry (HRMS) ruled out the involvement of secondary radicals in the degradation mechanism. The quantitative calculation with the help of authentic standards pointed out the predominant role of hydroxylation pathways, especially in the initial stages. Although a noticeable decline in the degradation efficiency was observed in river water samples (complete degradation after 25 min with an approximately 20% total organic carbon (TOC) removal), appreciable TOC removal (70%) was eventually achieved after prolonged irradiation (1 h) and in the presence of additional H2O2 (5 times), revealing the potential of our technique. The results furnished in this report could be considered as a preliminary step for the construction of •OH-based wastewater treatment methodologies for the remediation of toxic pollutants from the real environment

Single-Particle Analysis of Atmospheric Aerosols: Applications of Raman Spectroscopy

Atmospheric aerosols, produced as a consequence of different anthropogenic and natural processes, impart significant control over the global energy budget, climate, and human–environmental health. Their size varies across the nano–micrometer scale. Based on their origin, they may be classified into primary or secondary aerosols. Biomass burning, incomplete combustion of fossil fuels, volcanic eruptions, and traffic-related and wind-driven suspensions contribute to primary aerosol emissions. In contrast, gas-to-particle conversion within the atmosphere leads to secondary particle production. The study of atmospheric aerosols is vital to the field of atmospheric research. The dynamic nature (highly variable concentration composition and size with space and time) of aerosols makes them difficult to investigate. Today, aerosol research involves the application of various spectrometric and spectroscopic techniques. The single-particle analysis of aerosols is yet a challenge. In this review, the merits and demerits of various offline and online techniques used for aerosol research are discussed in a nutshell. Mass spectrometric techniques fail in distinguishing certain species. However, Raman spectroscopy’s emergence for the compositional analysis of aerosols resolves most of the present characterization challenges. This review focuses on Raman spectroscopy applications, the merits of this technique, and its immense scope for the measurement of various types of aerosols and their properties. Surface-enhanced Raman spectroscopy (SERS) has an advantage over conventional micro-Raman spectroscopy (MRS). The review depicts the dominance of SERS, specifically in the context of the measurement of ambient atmospheric aerosols. This review discusses two important components, namely laboratory simulation and ambient aerosol studies

Advanced Oxidation Processes for Degradation of Water Pollutants—Ambivalent Impact of Carbonate Species: A Review

Advanced oxidation processes (AOPs) hold great promise in the removal of organic contaminants. Reactive oxygen species (ROS) produced in AOPs react with target pollutants to initially form several intermediate compounds that finally undergo complete mineralization. Such observations are reported, especially for laboratory-scale experiments performed in pure water. On the other hand, while considering real contaminated wastewater matrices, particularly industrial effluents, there are many co-existing ions. Carbonate ions are one of the major inorganic ions commonly existing in water resources. Hence, these ions have a significant impact on the respective water treatment processes. This review focused on the effect of carbonate ions on the degradation of pollutants in AOPs. In AOPs, carbonate radicals are formed by the scavenging reaction of the respective ions with ROS. The reactivity of these radicals towards the pollutant varies with respect to the structure and functionality. Therefore, depending on the functionalities of the contaminants, these ions show both positive and negative effects. Thus, this review aims to summarize the effects of carbonate species on the degradation of organic contaminants during AOPs and their environmental impacts. The carbonates enhanced the degradation of several emerging organic pollutants, including aniline, bisphenol A, rhodamine B, acid orange 7, naphthalene, and phenol derivatives. Carbonate presence was also revealed to have a positive contribution in cases of drug degradation, including sulfamethoxazole, propranolol, sulfamethazine, salbutamol, trimethoprim, azithromycin, naproxen, oxcarbazepine, and oxytetracycline

Single-Particle Analysis of Atmospheric Aerosols: Applications of Raman Spectroscopy

Atmospheric aerosols, produced as a consequence of different anthropogenic and natural processes, impart significant control over the global energy budget, climate, and human–environmental health. Their size varies across the nano–micrometer scale. Based on their origin, they may be classified into primary or secondary aerosols. Biomass burning, incomplete combustion of fossil fuels, volcanic eruptions, and traffic-related and wind-driven suspensions contribute to primary aerosol emissions. In contrast, gas-to-particle conversion within the atmosphere leads to secondary particle production. The study of atmospheric aerosols is vital to the field of atmospheric research. The dynamic nature (highly variable concentration composition and size with space and time) of aerosols makes them difficult to investigate. Today, aerosol research involves the application of various spectrometric and spectroscopic techniques. The single-particle analysis of aerosols is yet a challenge. In this review, the merits and demerits of various offline and online techniques used for aerosol research are discussed in a nutshell. Mass spectrometric techniques fail in distinguishing certain species. However, Raman spectroscopy’s emergence for the compositional analysis of aerosols resolves most of the present characterization challenges. This review focuses on Raman spectroscopy applications, the merits of this technique, and its immense scope for the measurement of various types of aerosols and their properties. Surface-enhanced Raman spectroscopy (SERS) has an advantage over conventional micro-Raman spectroscopy (MRS). The review depicts the dominance of SERS, specifically in the context of the measurement of ambient atmospheric aerosols. This review discusses two important components, namely laboratory simulation and ambient aerosol studies

Sustainable Polyelectrolyte Multilayer Surfaces: Possible Matrix for Salt/Dye Separation

The development of a sustainable membrane surface based on chitosan/poly­(acrylic acid) (CHI/PAA) multilayers suitable for applications in analytical separations is reported here. Bilayers are constructed on polyamide microfiltration membranes at a pH combination of 3/3 (CHI pH/PAA pH) through a layer by layer approach. A 12.5 bilayer yielded a thickness of 400 nm. Low pressure (10 psi) filtrations through a 5.5 bilayered membrane exhibited high flux (7 m³ m^–2 day^–1) and selectivity (NaCl/reactive black 5 (RB5) selectivity >8000). The selectivity and flux observed here are the highest reported to date for low pressure filtrations through membranes. The increase in flux with increasing feed salt concentration is correlated with morphological transformations. Salt content above 7500 ppm causes some perturbation of surface layers. The presence of RB5, a model dye in the feed, restores the surface to maintain sustainability. A skin layer as thin as 50 nm imparts a large separation window. An RB5 feed concentration of 500 ppm results in 98.64% rejection with a flux of 25.79 m³ m^–2 day^–1. The increase in flux with feed dye concentration supports the plasticizing action of RB5. The transport studies with large feed dye concentrations indicate that at a dye concentration of 500 ppm, the linear growing region (pre-exponential, 5.5 bilayer) itself provides a separation window similar to that of 100 ppm. At the same time, 1000 ppm requires a 9.5 bilayer that falls in the nonlinear growing region. Scanning electron microscopy images show the increase in porosity with respect to feed dye. Interesting morphologies that show the sustainable nature of the membrane surfaces along with the transport data of RB5 are presented