基于工艺过程分析的废旧塑料再生利用污染源研究

在分析废旧塑料再生利用工艺过程的基础上,确定了废塑料综合利用工艺的产污节点,并通过物流平衡和水平衡计算,得出了总的产排污量,为环境保护措施提供重要依据,以实现保护环境和资源合理再生利用。     

Determination of traces of fluorine,chlorine, bromine,cadmium and lead in plastic materials

This paper describes the quantitative determination of F, Cl, Br, Cd and Pb in plastic materials. The concentration of the elements Cl, Br, Cd and Pb is first semiquantitatively measured by X‐ray fluorescence spectrometry (XRF) directly in the solid sample with a detection limit of approximately 10 μg/g. Afterwards, F and any of the other elements which exceed the limit values for materials which are disposable without special precautions are measured after the digestion of the material. The samples are digested either under pressure in an oxygen atmosphere for F, Cl and Br or under pressure with nitric acid for Cd and Pb. The digestion converts the halides to the anions which are measured potentiometrically (F^‐, Br^‐) or with ion chromatography (Cl^‐). Cd and Pb are measured by graphite furnace atomic absorption spectrometry (GF‐AAS). The determination limits achieved are 20 μg/g for F and Br, 250 μg/g for Cl, 0.01 μg/g for Cd and 0.2 μg/g for Pb, all below the limit values set by current regulations in Switzerland.     

Microtox assay to determine the toxicity of degradation products from degradable plastics

Six types of starch-polyethylene degradable plastics were evaluated for the release of water-soluble toxic compounds under accelerated degradation conditions. A plastic strip (2.5×15.2 cm) was placed in a 250-ml Erlenmeyer flask with 100 ml of ASTM type I water with or without trace element solutions and shaken at 65°C and 110 rpm for 20 weeks in replicates of two. High temperature was used to accelerate the oxidative degradation of polyethylene. Plastic degradation was measured by loss of tensile strength, percentage elongation, strain energy, and weight-average molecular weight. The most rapid period of polyethylene thermal degradation was complete for most materials by day 28. Ten-milliliter aqueous samples were removed from each flask at days 1, 7, 28, 56, 84, and 140 (water volumes were maintained at 100 ml with fresh type I water), filtered through glass filters, then evaluated by using the Microtox Toxicity Analyzer (Microbics Corporation, Carlsbad, CA). No water-soluble toxic compounds were detected during the period of rapid film degradation. Toxicity was observed at day 28 for one film and at day 84 for all films, which could possibly correlate with the release of small oxidative compounds such as formaldehyde and acetaldehyde. Because of the sensitivity of this assay, positive results must be confirmed by otherin vitro studies.Journal Paper No. J-14851 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Projects No. 2889 and 0178.     

Degradation studies of novel degradable starch-polyethylene plastics containing oxidized polyethylene and prooxidant

Linear low-density polyethylene films were prepared that contained native corn starch (7, 14, or 28%), low or high molecular weight oxidized polyethylene (15%), and a prooxidant mixture (18% POLYCLEAN II) that contains manganese and vegetable oil. For each mixture all components were first mixed at high temperatures in a twin-screw extruder and pelletized. The pellets were cast into films using a single-screw extruder. Oxidized-polyethylene addition did not impair the transparency and thickness of the films and did not reduce the percentage elongation, whereas significant reductions in film mechanical properties were observed. Thermal and photodegradation properties of each film were evaluated by 70°C forced-air oven treatment (20 days), by high-temperature, high-humidity treatment in a steam chamber (20 days), and by exposure to ultraviolet light (365 nm; 4 weeks). Changes in the mechanical properties of the films were determined by an Instron Universal Test Machine; in the carbonyl index, Fourier transform infrared spectroscopy; and in molecular weight, by high-temperature gel-permeation chromatography (HT-GPC). The addition of oxidized polyethylene, especially high molecular weight oxidized polyethylene, and up to 14% starch to the films significantly increased the rate of thermal and photodegradation.Journal Paper No. J-15363 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 0178 and 2889.     

The power of environmental norms: marine plastic pollution and the politics of microbeads

Emerging environmental norms gain strength and diffuse more quickly when scientific evidence of harm is consolidating, when activism is intensifying, and when political and corporate resistance is relatively weak. The anti-microbead norm – that plastic microbeads should be removed from personal care products – has been gaining global influence since 2012; witness the upsurge in anti-microbead activism, public concern, voluntary corporate phasedowns and governmental bans. By 2018, the world was on track to eliminate microbeads from ‘rinse-off’ products within a decade, reducing microplastics flowing into oceans by 1–2%. This confirms the power of environmental norms, but how and why this phaseout is occurring – unequally across jurisdictions, with firms creating loopholes, missing deadlines and limiting the scope of reforms – also reveals innate weaknesses of bottom-up, ad hoc norm diffusion as a way of improving marine governance. These weaknesses are heightened when economic stakes are high, solutions are complex and costly, authority is fragmented across jurisdictions and corporate resistance is strong.     

Toward maximizing the recycling rate in a Sapporo waste plastics liquefaction plant

Sapporo Plastics Recycling Co., Ltd., (SPR) started its commercial operation of waste plastics liquefaction in 2000. At first only hydrocarbon oil was reclaimed, this being derived from the waste plastics liquefaction process under the Japanese Containers and Packaging Recycling Law. Presently, thermal degradation residue and hydrochloric acid are being produced as by-products in addition to the hydrocarbon oil. As a result, the SPR plastics liquefaction plant has achieved a high reclamation rate of 96%, and 93% of the recycled products have been reused in Hokkaido, where SPR is located. The technical problems caused by corrosion and clogging have been solved. Chemical Feedstock Recycling & Other Innovative Recycling Techniques 6     

废塑料的回收利用及降解塑料的生产现状

介绍了废塑料的再生利用，热分解回收低分子化合物和焚烧回收热能的技术，并对国内降解塑料的生产现状进行了评述。     

Preliminary Studies on Converting Agricultural Waste into Biodegradable Plastics,Part I: Corn Distillers’ Dry Grain

Distillers dry grain (DDG) was derivatized either by carboxymethylation, glutaration, maleiation, phthallation, or succination in order to produce anionic materials suitable for complexation with soy protein isolate. Infrared spectroscopy confirmed that derivatization of DDG by all reagents was successful. Blending of derivatized anionic products with soy protein resulted in instant precipitation of gels. The gels were centrifuged, molded, and dried into solid pellets with tensile strengths as high as 1.67MPa, suggesting that these materials could be promising as biodegradable structural materials. Infrared spectroscopy suggested the possibility of complexes forming between soy protein isolate and each of the derivatized DDG samples.     

Recyling of plastic wastes via pyrolysis

Pyrolysis for the simultaneous generation of oils and gases can be convenient to obtain hydrocarbons and even to recover crude petrochemicals or to generate energy from waste plastics. A Gray–King apparatus has been used to pyrolyze waste polyethylene (PE), polystyrene (PS), both separately and with different compositions. Thermogravimetric analysis of waste plastics indicated the critical temperatures, which should be effective for pyrolysis. The chosen heating rate was low in order to achieve higher liquid yields. The results showed that waste PS yielded higher liquid, and waste PE yielded higher gaseous products. The dominant liquid product of PS waste was styrene whereas for waste PE, prophenylbenzene was the dominant pyrolysis product.