Metall-Recycling mittels Biohydrometallurgie

Biohydrometallurgy as a section of hydrometallurgy uses specific metabolic capabilities of microorganisms for metal extraction. Biomining is the application of bioleaching for metal extraction from sulfide ores. For recycling, i.e., metal extraction from waste and industrial residues, there are no biohydrometallurgical technologies yet, but promising laboratory studies on metal extraction from solids. In this review article, these are summarized, and perspectives are shown.     

废塑料资源化高值利用的产业发展

近年来,伴随着塑料消费量爆发式增长,废塑料引发的一系列环境问题逐渐得到人们的关注。由于其难降解性以及含有大量高分子聚合物,废塑料的资源化回收利用成为技术研发的热点。本文简述了废塑料带来的资源环境问题,分析了目前废塑料资源化利用产业的发展现状。分别从基建、能源燃料、织物服装、高科技、炼钢等方面,讨论了废塑料高值化回收利用的相关技术和未来发展前景。     

废弃光伏面板资源化利用的技术进展

近年来,太阳能光伏装机量呈现指数型增长,废弃光伏面板的资源环境问题日益凸显。本文通过调研太阳能光伏面板的废弃、回收管理和资源化利用等相关技术问题,综述了废弃光伏面板的资源化利用价值、环境和健康风险;讨论了废弃光伏面板资源化利用的几种处理工艺,包括物理工艺、热处理工艺、化学工艺和复合工艺等;指出了废弃光伏面板资源化利用具有的发展前景。     

高分子材料的循环利用

概述了近年来与环境治理的有关的一个重要主题－高分子材料循环利用的发展状况的新型循环技术，同时对高分子材料循环存在的问题，将来的发展趋势和前景作了讨论。     

The effect of recycled plastic aggregate on chemico-physical and functional properties of composite mortars

In this paper the interaction mechanism between recycled plastic aggregates and lime matrix in composite mortars was investigated by means of thermal, morphological and Fourier Transform Infrared Spectroscopy (FTIR) analyses. In order to assess the fire behavior of the composite mortars, a cone calorimeter method was adopted. The plastic aggregate, mainly made of polyolefin and polyethylene terephthalate, is obtained from an industrial waste, through a process that provides a plasticization and densification by extrusion of plastic waste. Several composite mortars were prepared by replacing silica powder with 10%, 15% and 20% of recycled aggregate. Experimental results attest that, even if the filler was not chemically modified, there is a good chemical interaction between the plastic aggregate and mortar, involving a reduction of the negative effects on physical and functional properties of the mortar composites, such as thermal degradation and fire resistance. In fact all the specimens showed a scarce sensitivity to flashover, and can be classified as low risk materials.     

Carbon-Dioxide-Based Microsortation of Postconsumer Polyolefins and its Effect on Polyolefin Properties

Postconsumer polyolefin flake has been sorted using liquid carbon dioxide as a float-sink medium. This separation of PP and LDPE from HDPE was conducted at ambient temperature and a pressure that yielded a CO₂ specific gravity of 0.955, causing the HDPE to sink and the LDPE and PP to float. Although this process provided a high-purity (99+%) HDPE product stream, the effect of immersing the plastics in liquid carbon dioxide at these conditions was not previously measured. Therefore, six HDPE samples, two LDPE samples, and five PP samples were exposed to high-pressure carbon dioxide for 20 min. After this exposure, the polyolefins did not foam when the carbon dioxide was rapidly vented from the vessel. The weight reduction averaged 0.17%, which was attributed to the dissolution of low-molecular-weight additives or contaminants present on the surface of the plastics. No significant change in the melting point or latent heat of melting was observed, indicating that the degree of crystallinity was not affected by the exposure to carbon dioxide. No reduction was observed in the temperature at which the onset of thermal degradation occurred, because of the low solubility and degree of extraction of thermal stabilizers during the immersion in carbon dioxide. These results indicated that no deleterious effects on the polyolefin properties were associated with this separation technique.     

Service Distance and Ratio-Based Location-Allocation Models for Siting Recycling Depots

Siting appropriate locations for placing recycling depots is essential for promoting an efficient recycling program. This study develops three optimization models to facilitate siting analysis for district-based, district open, and nondistrict situations. An enhanced model to improve drawbacks of locating recycling depots that mainly serve residents in adjacent districts using the district open model is also proposed. Three factors of service distance, local service ratio, and service ratios for different distance ranges are used to compare the effectiveness of alternatives obtained from different models. A case study involving 16 city districts is implemented to demonstrate the applicability of the proposed models. Findings show that the district-based alternatives have best overall service distance and service ratio, but with a poor local service ratio. The enhanced model obtains alternatives that achieve good local service ratio with acceptable service distance and service ratios for different distance ranges.     

Characterization of polypropylene–polyethylene blends made of waste materials with compatibilizer and nano-filler

Waste polypropylene and polyethylene were blended by a twin-screw extruder with two compatibilizers (PE-g-MAH and EPDM) and an additive (O-MMT). The mechanical properties were measured firstly. By adding O-MMT, the tensile strength showed a decline while the impact strength made a promotion. The phase morphology was observed by scanning electron microscopy (SEM) to explore the fracture toughness of blends. The blend with EPDM had a better compatibilization than PE-g-MAH. X-ray diffraction was used to investigate the crystallization behavior and the result showed no change by blending. Moreover, further measurements such as thermogravimetric (TGA) and differential scanning calorimetry (DSC) were taken to show the thermal stability and crystallization temperature of the blend. Additionally, the storage modulus and loss modulus are measured by dynamic mechanical analysis (DMA), the presence of O-MMT caused the increases of the storage modulus and loss modulus.     

Mechanical Stabilization of Cemented Soil–Fly Ash Mixtures with Recycled Plastic Strips

An experimental investigation was undertaken to evaluate the mechanical behavior of a soil–cement–fly ash composite, reinforced with recycled plastic strips (high-density polyethylene) that were obtained from postconsumer milk and water containers. The primary motivation for the study was to investigate the innovative reuse of several candidate waste materials in geotechnical and pavement applications. The specific objectives of the research were: (1) to evaluate the compressive, split tensile, and flexural strength characteristics of the material, and (2) to determine the effectiveness of recycled plastic strips in enhancing the toughness characteristics of the composite. Since cement-stabilized materials are weak in tension, the main focus of the experimental program was to conduct a series of specially instrumented split tensile and flexural tests on mixes containing various amounts of cement, fly ash, and plastic strips. For a meaningful comparison of test results, all specimens were prepared at a constant dry density. The standard ASTM C496 procedure for split tensile test was slightly modified by attaching two horizontal linear variable differential transformers (LVDTs) to measure the diametral deformation of the specimen due to compressive loading in an orthogonal direction. This modification enabled the evaluation of the postpeak toughness behavior of the composite. For some specimens, a strain gauge was attached to the middle of the face perpendicular to the loading plane in order to correlate the results with the one found using the LVDTs. All tests were performed with a 90 kN universal testing machine with deformation control. Experimental data show that the soil–cement matrix stabilized with 4% to 10% by weight of fly ash and reinforced with 0.25% to 0.5% (by weight) plastic strips (having lengths of 19 mm or 38 mm) can achieve a maximum compressive strength of 7000 kPa, a split tensile strength of 1000 kPa, and a flexural strength of 1200 kPa. These ranges in strength values are suitable for a high-quality stabilized base course for a highway pavement. To quantify the reinforcing effects in the postpeak region, a dimensionless toughness index is proposed. It is found that the use of fiber reinforcement significantly increases the postpeak load carrying capacity of the mix and thus the fracture energy. It is concluded that the lean cementitious mix containing recycled materials offer a lot of promise as an alternative material for civil engineering construction.     

矿产品消费分析

人类社会生产所需的物质和能量只能从自然界取得，矿业提供了这些物质和能量的绝大部分。第二产业从物理学角度可划分为物质改造和能量转换两种类型，评价资源利用效率，前者用“物耗”和“能耗”指标，后者宜用“能量转换效率”指标。能源矿产品消费和矿物能源消费要加以区别。物质改变在一定条件下可逆，节约物质资源要靠发展循环经济；能量转化不可逆，节约矿物能源要靠开发替代资源。