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Detlef R.U. Knappe

Bio: Detlef R.U. Knappe is an academic researcher from North Carolina State University. The author has contributed to research in topics: Adsorption & Activated carbon. The author has an hindex of 33, co-authored 78 publications receiving 6220 citations. Previous affiliations of Detlef R.U. Knappe include University of North Carolina at Chapel Hill.


Papers
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Journal ArticleDOI
TL;DR: Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride, and PCBs could transfer from contaminated plastics to streaked shearwater chicks.
Abstract: Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2′-bis(p-chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g–1 to µg g–1. Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub µg l–1 to mg l–1 and were correlated with the level of economic development.

2,114 citations

Journal ArticleDOI
01 Jan 2002-Carbon
TL;DR: In this article, a matrix of activated carbon fibers with three activation levels and four surface chemistry levels was used to evaluate pore structure and surface chemistry effects, and three granular activated carbons (GACs) were studied.

630 citations

Journal ArticleDOI
TL;DR: In this article, the authors report the presence of PFECAs in the Cape Fear River watershed, their fate in water treatment processes, and their adsorbability on powdered activated carbon (PAC).
Abstract: Long-chain per- and polyfluoroalkyl substances (PFASs) are being replaced by short-chain PFASs and fluorinated alternatives. For ten legacy PFASs and seven recently discovered perfluoroalkyl ether carboxylic acids (PFECAs), we report (1) their occurrence in the Cape Fear River (CFR) watershed, (2) their fate in water treatment processes, and (3) their adsorbability on powdered activated carbon (PAC). In the headwater region of the CFR basin, PFECAs were not detected in raw water of a drinking water treatment plant (DWTP), but concentrations of legacy PFASs were high. The U.S. Environmental Protection Agency’s lifetime health advisory level (70 ng/L) for perfluorooctanesulfonic acid and perfluorooctanoic acid (PFOA) was exceeded on 57 of 127 sampling days. In raw water of a DWTP downstream of a PFAS manufacturer, the mean concentration of perfluoro-2-propoxypropanoic acid (PFPrOPrA), a replacement for PFOA, was 631 ng/L (n = 37). Six other PFECAs were detected, with three exhibiting chromatographic peak ar...

410 citations

Journal ArticleDOI
TL;DR: The rate-limiting process of intraparticle surface diffusion for arsenate adsorption by porous iron oxides appears analogous to organic compound adsorbed by activated carbon despite differences in adsorbent mechanisms.

348 citations

Journal ArticleDOI
TL;DR: A comparison of adsorption isotherm data collected in the presence and absence of NOM showed that percent reductions of single-solute TCE and MTBE adsorptive capacities that resulted from the presence of co-adsorbing NOM were not strongly affected by the chemical characteristics of activated carbons.

287 citations


Cited by
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Journal ArticleDOI
TL;DR: Global plastics production and the accumulation of plastic waste are documented, showing that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing and that the average size of plastic particles in the environment seems to be decreasing.
Abstract: One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic...

4,044 citations

Journal ArticleDOI
TL;DR: Ingestion of microplastics has been demonstrated in a range of marine organisms, a process which may facilitate the transfer of chemical additives or hydrophobic waterborne pollutants to biota.

3,643 citations

Journal ArticleDOI
TL;DR: Strong acids and bases seem to be the best desorbing agents to produce arsenic concentrates, and some commercial adsorbents which include resins, gels, silica, treated silica tested for arsenic removal come out to be superior.

3,168 citations

Journal ArticleDOI
TL;DR: This review of 68 studies compares the methodologies used for the identification and quantification of microplastics from the marine environment and suggests standardized sampling procedures which allow the spatiotemporal comparison ofmicroplastic abundance across marine environments.
Abstract: This review of 68 studies compares the methodologies used for the identification and quantification of microplastics from the marine environment. Three main sampling strategies were identified: selective, volume-reduced, and bulk sampling. Most sediment samples came from sandy beaches at the high tide line, and most seawater samples were taken at the sea surface using neuston nets. Four steps were distinguished during sample processing: density separation, filtration, sieving, and visual sorting of microplastics. Visual sorting was one of the most commonly used methods for the identification of microplastics (using type, shape, degradation stage, and color as criteria). Chemical and physical characteristics (e.g., specific density) were also used. The most reliable method to identify the chemical composition of microplastics is by infrared spectroscopy. Most studies reported that plastic fragments were polyethylene and polypropylene polymers. Units commonly used for abundance estimates are “items per m2” ...

3,119 citations

Journal ArticleDOI
10 Dec 2014-PLOS ONE
TL;DR: The total number of plastic particles and their weight floating in the world's oceans is estimated from 24 expeditions across all five sub-tropical gyres, costal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows and visual survey transects of large plastic debris.
Abstract: Plastic pollution is ubiquitous throughout the marine environment, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere and remote regions. Here we report an estimate of the total number of plastic particles and their weight floating in the world’s oceans from 24 expeditions (2007–2013) across all five sub-tropical gyres, costal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows (N5680) and visual survey transects of large plastic debris (N5891). Using an oceanographic model of floating debris dispersal calibrated by our data, and correcting for wind-driven vertical mixing, we estimate a minimum of 5.25 trillion particles weighing 268,940 tons. When comparing between four size classes, two microplastic ,4.75 mm and meso- and macroplastic .4.75 mm, a tremendous loss of microplastics is observed from the sea surface compared to expected rates of fragmentation, suggesting there are mechanisms at play that remove ,4.75 mm plastic particles from the ocean surface.

3,091 citations