Synthesis of stabilized iron nanoparticles from acid mine drainage and Rooibos tea for application as a Fenton-like catalyst

Intensive mining activities generate toxic acid mine drainage (AMD) effluents containing a high concentration of metals, including iron. The chemical synthesis of iron nanoparticles from this waste could lead to further environmental concerns. Therefore, the green synthesis of nanoparticles using plants has gained significant interest because of several benefits, including being eco-friendly. The current study reports a novel approach involving the synthesis of stabilized iron nanoparticles from AMD using rooibos tea extract. An aqueous solution of rooibos tea was prepared and titrated with AMD to reduce Fe2+/Fe3+. The samples synthesized under optimum conditions were characterized by TEM, XRD, FTIR, UV−Vis, and EDS. The results revealed that the nanoparticles had an average particle size of 36 nm with a spherical shape. These particles showed promising application as a Fentonlike catalyst for the degradation of textile dye (orange II sodium salt) with a removal efficiency of 94% within 30 min. Thus, the stabilized iron nanoparticles synthesized here performed in higher ranges than the currently reported Fenton-like catalysts regarding dye removal efficiency and reaction time

Synthesis of bimetallic FeMn nanoparticles using rooibos tea extract: characterization and application

Bimetallic FeMn nanoparticles based on a ferromanganese wad were successfully synthesized employing an entirely green approach. South African rooibos tea (RTea) extract was used as an environmentally friendly reducing and capping agent for preparing the Fe and Mn nanoparticles (nFeMn). The obtained nFeMn suspension and freeze-dried RTea capped nFeMn powder were characterized using several techniques. Elemental analysis conducted using XRF combined with ICP analysis revealed a metallic loading of 1.08 wt% of Fe and 0.25 wt% of Mn. The ultraviolet–visible spectroscopy (UV–vis) showed a broad shoulder in the UV region where the peaks of RTea and FeMn are located, implying bond formation during the reaction between RTea polyphenols and nFeMn. TEM analysis depicted a core–shell architecture for the nFeMn with an average size of 20 nm while the FTIR revealed that specific peaks observed in the spectrum of RTea extract were visible on that of the nFeMn powder, indicating the capping of nFeMn particles by the RTea extract. Finally, the reactivity of nFeMn powder as a Fenton-like reagent was probed for the decoloration of methylene blue (MB) from an aqueous solution. Fenton-like oxidation of MB followed a pseudo-first-order reaction kinetics with a rate constant of 0.23 A− 1 min− 1. The results showed that nFeMn removed MB dye with an efficiency of over 95% in the MB concentration range of 50–250 mg/L. Overall, the finding herein is unique because we directly used readily available raw material as a source of metals and a safe, practical reagent to prepare bimetallic FeMn nanoparticles that can be used to remove the color from dye wastewater, thus, creating a circular green process

Examining Metal Contents in Primary and Secondhand Aerosols Released by Electronic Cigarettes

The usage of electronic cigarettes (ECs) has surged since their invention two decades ago. However, to date, the health effects of EC aerosol exposure are still not well understood because of insufficient data on the chemical composition of EC aerosols and the corresponding evidence of health risks upon exposure. Herein, we quantified the metals in primary and secondhand aerosols generated by three brands of ECs. By combining aerosol filter sampling and inductively coupled plasma mass spectrometry (ICP-MS), we assessed the mass of metals as a function of EC flavoring, nicotine concentration, device power, puff duration, and aging of the devices. The masses of Cr, Cu, Mn, Ni, Cu, and Zn were consistently high across all brands in the primary and secondhand aerosols, some of which were above the regulated maximum daily intake amount, especially for Cr and Ni with mass (nanograms per 10 puffs) emitted at 117 ± 54 and 50 ± 24 (JUUL), 125 ± 77 and 219 ± 203 (VOOPOO), and 33 ± 10 and 27 ± 2 (Vapor4Life). Our analysis indicates that the metals are predominantly released from the EC liquid, potentially through mechanisms such as bubble bursting or the vaporization of metal-organic compounds. High metal contents were also observed in simulated secondhand aerosols, generally 80-90% of those in primary aerosols. Our findings provide a more detailed understanding of the metal emission characteristics of EC for assessing its health effects and policymakin

A filter-based system mimicking the particle deposition and penetration in human respiratory system for secondhand smoke generation and characterization

Secondhand smoke endangers both the environment and the health of nonsmokers. Due to the scarcity of repeatable data generated by human subjects, a system capable of generating representative secondhand smoke is essential for studying smoke properties. This work presents the design and validation of a filter-based system that could mimic the particle deposition and penetration in human respiratory system for secondhand smoke generation and characterization. Guided by our study on characterizing size-dependent filtration efficiency of common materials, we identified three filter media that generate similar particle deposition efficiencies compared to different regions of the human respiratory system over a wide submicron size range. We demonstrated the performance of the proposed filter-based system using various operating conditions. Additionally, we compared the properties of secondhand smoke particles to those of primary smoke particles. The difference in aerosol deposition efficiencies between the filter-based system and the International Commission on Radiological Protection (ICRP) model was less than 10% in the size range of 30 to 500 nm. High concentrations of metals were detected in the secondhand smoke. The contents of Ni and Cr generated from the secondhand electronic cigarettes are at least 20 and 5 times above the regulated daily maximum intake amount. Given the agreement in aerosol respiratory deposition between the filter-based system and the ICRP model, such a system can facilitate laboratory studies of secondhand smoke due to its simple structure, high repeatability, and ease of control while remaining free of human subjects

The effect of hypochlorous acid on the filtration performance and bacterial decontamination of N95 filtering facemask respirators

•Numerous hospital disinfectants are known to affect N95 FFR filtration performance.•Hypochlorous acid spray does not affect N95 FFR material's filtration performance.•Soaking N95 FFRs in HOCl can achieve decontamination, but not HOCl spray. Stabilized hypochlorous acid (HOCl) is increasingly used as a hospital disinfectant and antiseptic, yet its effect on N95 filtration facemask respirators (FFR) is unknown. These FFRs could also contribute to fomite-based transmission of nosocomial infections if worn for extended use between patient rooms. Filtration performance of N95 FFR fabric swatches was assessed after various levels of HOCl exposure. N95 swatches were then contaminated with 108Escherichia coli or 108Staphylococci aureus and treated with HOCl solution, 70% ethyl alcohol, or normal saline. Surviving bacterial numbers were assessed by plate counts. The size-dependent filtration efficiency of HOCl-sprayed N95 FFR fabric ranged from 96% to 100%, showing no significant change. Flow resistance testing revealed almost no change compared to control. Submersion in HOCl, but not spraying, had an excellent bactericidal effect on contaminated swatches. The role of the outer hydrophobic layer of N95 FFRs is discussed regarding the effects of HOCl on filtration and bacterial decontamination. N95 material, sprayed with or briefly submerged in HOCl, maintained its filtration function. HOCl delivery by spray pump, however, would not accomplish decontamination of extended use FFRs between patient encounters. HOCl submersion of intact FFRs, contaminated with various hospital pathogens, is worth further study

Examining Metal Contents in Primary and Secondhand Aerosols Released by Electronic Cigarettes

The usage of electronic cigarettes (ECs) has surged since their invention two decades ago. However, to date, the health effects of EC aerosol exposure are still not well understood because of insufficient data on the chemical composition of EC aerosols and the corresponding evidence of health risks upon exposure. Herein, we quantified the metals in primary and secondhand aerosols generated by three brands of ECs. By combining aerosol filter sampling and inductively coupled plasma mass spectrometry (ICP-MS), we assessed the mass of metals as a function of EC flavoring, nicotine concentration, device power, puff duration, and aging of the devices. The masses of Cr, Cu, Mn, Ni, Cu, and Zn were consistently high across all brands in the primary and secondhand aerosols, some of which were above the regulated maximum daily intake amount, especially for Cr and Ni with mass (nanograms per 10 puffs) emitted at 117 ± 54 and 50 ± 24 (JUUL), 125 ± 77 and 219 ± 203 (VOOPOO), and 33 ± 10 and 27 ± 2 (Vapor4Life). Our analysis indicates that the metals are predominantly released from the EC liquid, potentially through mechanisms such as bubble bursting or the vaporization of metal-organic compounds. High metal contents were also observed in simulated secondhand aerosols, generally 80-90% of those in primary aerosols. Our findings provide a more detailed understanding of the metal emission characteristics of EC for assessing its health effects and policymakin

Examining the Oxidation States of Metals in Aerosols Emitted by Electronic Cigarettes

Electronic cigarettes (ECs) emit many toxic substances, including metals, that can pose a threat to users and the environment. The toxicity of the emitted metals depends on their oxidation states. Hence, this study examines the oxidation states of metals observed in EC aerosols. X-ray photoelectron spectroscopy analysis of the filters that collected EC aerosols identified the oxidation states of five primary metals (based on surface sample analysis), including chromium(III) (close to 100%) under low power setting while a noticeable amount of chromium(VI) (15%) at higher power settings of the EC, and copper(II) (100%), zinc(II) (100%), nickel(II) (100%), lead(II) (65%), and lead(IV) (35%) regardless of power settings. This observation indicates that the increased temperature due to higher power settings could alter the oxidation states of certain metals. We noted that many metals were in their lesser toxic states; however, inhaling these metals may still pose health risks.Electronic cigarettes (ECs) emit many toxic substances, including metals, that can pose a threat to users and the environment. The toxicity of the emitted metals depends on their oxidation states. Hence, this study examines the oxidation states of metals observed in EC aerosols. X-ray photoelectron spectroscopy analysis of the filters that collected EC aerosols identified the oxidation states of five primary metals (based on surface sample analysis), including chromium(III) (close to 100%) under low power setting while a noticeable amount of chromium(VI) (15%) at higher power settings of the EC, and copper(II) (100%), zinc(II) (100%), nickel(II) (100%), lead(II) (65%), and lead(IV) (35%) regardless of power settings. This observation indicates that the increased temperature due to higher power settings could alter the oxidation states of certain metals. We noted that many metals were in their lesser toxic states; however, inhaling these metals may still pose health risks