Occupational exposures to particulate matter and PM2.5-associated polycyclic aromatic hydrocarbons at the Agbogbloshie waste recycling site in Ghana.

Electronic waste (e-waste) disposal and recycling activities such as burning and smelting can emit particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and other pollutants that expose workers and nearby communities. At informal e-waste recycling facilities, both emission controls and protective measures for workers are absent. This study characterizes personal exposures (breathing zone) of PM and PAHs of e-waste workers at the large Agbogbloshie e-waste site in Accra, Ghana. We collected gravimetric and optical measurements of PM2.5 and PM10 using shift samples for workers and for an age- and gender-matched reference population. PM2.5 filters were analyzed for 26 PAHs using gas chromatography/mass spectroscopy. Among e-waste workers, PM2.5 and PM10 concentrations were 99 ± 56 and 218 ± 158 µg/m3 (median ± interquartile range, optical measurements), respectively; these levels were 78 and 57% higher, respectively, than levels measured at a fixed site that was centrally located at the waste site. In the reference community, breathing zone PM2.5 and PM10 levels were lower, 49 ± 20 and 131 ± 108 µg/m3, respectively, and the fraction of coarse PM was larger. We detected all 26 target PAHs, of which naphthalene and phenanthrene were the most abundant. PAH concentrations were weakly correlated to PM levels, but PAH abundances, representing the fraction of PAH mass to the total PM2.5 mass collected, were strongly and inversely correlated to PM levels, suggesting multiple and different sources of PAHs and PM that affected exposures. Both PM and PAH levels were elevated for workers performing burning and dismantling, and both exceeded standards or risk-based guidelines, e.g., lifetime excess cancer risks for several PAHs were in the 10-4 to 10-6 range, indicating the need to reduce emissions as well as provide respiratory protection. The study emphasizes the importance of using personal and shift samples to accurately characterize worker exposure.

Treated rice husk as a recyclable sorbent for the removal of microcystins from water.

Microcystins (MCs) appear during harmful algal blooms (HABs) in water sources worldwide, and represent a threat for humans and animals ingesting or inhaling MCs from the environment. Herein, treated rice husk (RH) was tested as a recyclable sorbent for removal of six MCs (MC-RR, MC-LR, MC-YR, MC-LA, MC-LF, and MC-LW) from water. RH was refluxed with hydrochloric acid and heated to 250 °C to produce the sorbent material. Twenty milligrams of treated RH removed >95% of the MCs from a 30 mL solution containing 25 µg/L of each MC. The adsorption of MCs onto RH follows the Freundlich isotherm model (R2 ≥ 0.9612) and pseudo-second-order kinetics (R2 ≥ 0.9996). More than 90% of MCs were removed within 5 min, and >95% were removed at equilibrium (in <40 min). Performance of the RH sorbent was evaluated by removing MCs from Lake Erie water collected during an algal bloom in 2017. The total concentration (extracellular plus intracellular) of six tested MCs in lake water ranged from 3.7 to 13,605.9 µg/L, and removal of MCs by treated RH ranged from 100.0% to 71.8%, respectively. The removal capacity of RH for the six MCs from the lake water sample containing 13,605.9 µg/L of MCs was 586 µg per g of treated RH. After being used to extract MCs, the RH was heated to 560 °C to produce silica nanoparticles. Therefore, treated RH enables rapid and efficient removal of MCs from water and it can be recycled for use as a raw material. Overall, treated RH can contribute to mitigation of environmental and health effects caused by MCs and reduce concerns for toxic waste disposal.

Solid-phase microextraction of heavy metals in natural water with a polypyrrole/carbon nanotube/1, 10-phenanthroline composite sorbent material.

A simple and sensitive method for simultaneous microextraction and determination of heavy metals using a new direct immersion solid-phase microextraction (DI-SPME) sorbent material combined with inductively coupled plasma mass spectrometry (ICP-MS) was investigated. In this method, sorbent coating composites were prepared by simultaneous electropolymerization of pyrrole on pencil lead in the presence of carbon nanotubes (CNTs) and different metal chelating ligands. Among the coatings evaluated, a polypyrrole coating with entrapped CNTs and the chelator 1, 10 phenanthroline allowed the determination of silver, cadmium, cobalt, iron, nickel, lead, and zinc. Parameters influencing microextraction efficiency including pH, extraction time, and desorption time were optimized. The linear dynamic ranges were 1-1000 µg L-1 for Ag, 1-750 µg L-1 for Cd, Pb, and Zn, and 1-500 µg L-1 for Co, Fe, and Ni with limits of detection of 0.012-0.163 µg L-1 and limits of quantification of 0.039-0.542 µg L-1. The relative standard deviations (RSDs, n = 5) ranged from 1.85% to 5.01%. The effect of inorganic interferences on the determination of the heavy metals also was examined and finally, the method was successfully applied for the determination of heavy metals in real water samples.

Solid-phase extraction, quantification, and selective determination of microcystins in water with a gold-polypyrrole nanocomposite sorbent material.

A novel sorbent material, gold-polypyrrole (Au-PPy) nanocomposite-coated silica, is described for the efficient solid-phase extraction (SPE) of six common microcystins (MCs) well below the recommended United States EPA and World Health Organization (WHO) guidelines. With the optimized SPE protocol, samples spiked with MCs were determined at ng/L concentrations by liquid chromatography-mass spectrometry (LC-MS) in different aqueous sample matrices, including HPLC-grade, tap, and lake water. The average recoveries for all MCs tested in the three water matrices ranged from 94.1-103.2% with relative standard deviations (RSDs) of 1.6-5.4%, which indicated excellent extraction efficiency and reproducibility. Limits of detection (LODs) and limits of quantification (LOQs) for all MCs in both tap and lake water samples were determined to be ≤1.5 ng/L and 5.0 ng/L, respectively. The Au-PPy nanocomposite-coated sorbent material was reusable for at least three independent MC extractions with a single SPE cartridge in the concentration range of 10-500 ng/L. Importantly, off-column selective separation at the sample preparation and preconcentration stage between more hydrophilic and more hydrophobic MCs was achieved by sequential elution through changes in the solvent composition and SPE bed size. Therefore, the Au-PPy nanocomposite-coated silica sorbent is a promising new material for the quantification of MC variants in water samples.

Electropolymerized Pyrrole-Based Conductive Polymeric Ionic Liquids and Their Application for Solid-Phase Microextraction.

Pyrrole was covalently bonded to 1-methyl and 1-benzylimidazolium ionic liquids (ILs) via an N-substituted alkyl linkage to prepare electropolymerizable IL monomers with excellent thermal stability. The methylimidazolium IL, [pyrrole-C6MIm]+, was then electropolymerized on macro- and microelectrode materials to form conductive polymeric IL (CPIL)-modified surfaces. Electrochemical characterization of a 1.6 mm diameter Pt disk electrode modified with poly[pyrrole-C6MIm]+ demonstrated a selective uptake for an anionic redox probe while rejecting a cationic redox probe. Furthermore, electropolymerization of [pyrrole-C6MIm]+ doped with single-walled carbon nanotubes (SWNT) on 125 µm platinum wires produced 42 µm thick poly[pyrrole-C6MIm]+/SWNT films compared to 17 µm in the absence of SWNT and 5 µm for the previously reported poly[thiophene-C6MIm]+ coatings. The poly[pyrrole-C6MIm]+/SWNT films were prepared with reproducible thicknesses as well as thermal properties sufficient for high-temperature applications, such as solid-phase microextraction (SPME) with gas chromatographic analysis. The utilization of the CPIL sorbent materials in SPME experiments provided excellent extraction efficiencies and selectivity toward organic aromatic analytes. The CPIL sorbent coatings also yielded outstanding fiber-to-fiber reproducibility on the basis of extraction efficiencies and improved response for a range of analytes relative to commercial 100 µm poly(dimethylsiloxane) fibers when normalized for differences in film thickness. Poly[pyrrole-C6MIm]+ CPIL coatings doped with SWNT are therefore promising new sorbent materials for SPME analyses.

Conductive polymeric ionic liquids for electroanalysis and solid-phase microextraction.

Three novel electropolymerizable thiophene-based ionic liquids (ILs) were synthesized and characterized as potential candidates for developing selective extraction media for chemical analysis. Electropolymerization of the bis[(trifluoromethyl)sulfonyl]imide ([NTf2](-)) analogs successfully produced uniform polymeric thin-films on macro- and microelectrode substrates from both vinyl and methylimidazolium IL monomer derivatives. The resultant conducting polymer IL (CPIL) films were characterized by electrochemical methods and found to exhibit attractive behavior towards anionic species while simultaneously providing an exclusion barrier toward cationic species. Thermogravimetric analysis of the thiophene-based IL monomers established a high thermal stability, particularly for the methylimidazolium IL, which was stable until temperatures above 350 °C. Subsequently, the methylimidazolium IL was polymerized on 125 µm platinum wires and utilized for the first time as a sorbent coating for headspace solid-phase microextraction (HS-SPME). The sorbent coating was easily prepared in a reproducible manner, provided high thermal stability, and allowed for the gas chromatographic analysis of polar analytes. The normalized response of the poly[thioph-C6MIm][NTf2]-based sorbent coating exhibited higher extraction efficiency compared to an 85 µm polyacrylate fiber and excellent fiber-to-fiber reproducibility. Therefore, the electropolymerizable thiophene-based ILs were found to be viable new materials for the preparation of sorbent coatings for HS-SPME.