Recycling and reuse of waste from electricity distribution networks as reinforcement agents in polymeric composites

Of the waste generated from electricity distribution networks, wooden posts treated with chromated copper arsenate (CCA) and ceramic insulators make up the majority of the materials for which no effective recycling scheme has been developed. This study aims to recycle and reuse this waste as reinforcement elements in polymer composites and hybrid composites, promoting an ecologically and economically viable alternative for the disposal of this waste. The CCA wooden posts were cut, crushed and recycled via acid leaching using 0.2 and 0.4 N H₂SO₄ in triplicate at 70 °C and then washed and dried. The ceramic insulators were fragmented in a hydraulic press and separated by particle size using a vibrating sieve. The composites were mixed in a twin-screw extruder and injected into the test specimens, which were subjected to physical, mechanical, thermal and morphological characterization. The results indicate that the acid treatment most effective for removing heavy metals in the wood utilizes 0.4 N H₂SO₄. However, the composites made from wood treated with 0.2 N H₂SO₄ exhibited the highest mechanical properties of the composites, whereas the use of a ceramic insulator produces composites with better thermal stability and impact strength. This study is part of the research and development project of ANEEL (Agência Nacional de Energia Elétrica) and funded by CPFL (Companhia Paulista de Força e Luz).     

Outdoor Weathering Evaluation of Carbon-Black-Filled, Biodegradable Copolyester as Substitute for Traditionally Used, Carbon-Black-Filled, Nonbiodegradable, High-Density Polyethylene Mulch Films

Carbon-black-filled, biodegradable, copolyester mulch film (Eastar®, or EA, Tennessee Eastman, Kingsport, TN) and commercial carbon-black-filled, high-density polyethylene (HDPE) mulch film were exposed for 12 weeks to commercial vegetable crop growing conditions by being placed directly on irrigated soil in the field of the University of Tennessee Alcoa Highway State Agriculture Experiment Station (Knoxville, TN) and by being placed on a plywood exposure rack as described by the American Society of Testing and Materials (ASTM) Standard Test Method 1435: Outdoor Weathering of Plastics. Mechanical properties and weather information were collected in order to evaluate the feasibility of using the newly developed biodegradable EA mulch film to replace the nonbiodegradable HDPE mulch film. Results indicate that the EA mulch film exhibited favorable tensile strength and elongation-at-break during outdoor exposure rack testing and outdoor, in-field, placed directly on the soil, exposure testing, suggesting biodegradable EA could be a substitute for the HDPE nonbiodegradable material.     

城市垃圾填埋场覆膜内的甲烷及恶臭物质特征研究

卫生填埋是常用的固体废弃物处置方法。部分填埋场对已经封场和暂时不填埋垃圾的区域覆盖高密度聚乙烯膜(HDPE),便于雨水分流、减少垃圾渗滤液产生量。通过在华北地区某城市生活垃圾卫生填埋场设置采样点,监测分析了HDPE覆膜内积聚的甲烷及恶臭物质的浓度和成分,研究在不同季节、填埋时间产生的甲烷及恶臭物质特征。结果表明:填埋场覆膜内甲烷的平均浓度为15.6%;硫化物、胺类以及恶臭浓度分别为153.9 mg/m3,16.0 mg/m3以及4 322 OU。主要的恶臭物质为硫化氢和氨。总挥发性有机物的浓度为0~147.2 mg/m3,苯系物、烷烃和烯烃是挥发性有机物的主要成分。恶臭浓度与硫化物、胺类浓度具有明显的相关性。环境温度、垃圾填埋龄和填埋量对甲烷及恶臭物质的产生与释放有明显影响。夏季甲烷及恶臭浓度分别达到81.2%和20 943 OU,明显高于其他季节。随着垃圾填埋龄和填埋量的增加,恶臭物质的浓度和成分均发生显著变化。     

Optimization of the recovery of plastics for recycling by density media separation cyclones

Material recovery processes are presented as the optimum option for recycling plastic wastes as a means of recovering hydrocarbon resources. There exist a large variety of automated material recovery processes for recycling of such wastes but each with significant limitations. Of these, the separation based on differences in densities is advocated as the optimum process either for producing recycled products or preparing wastes for subsequent recovery processing.Density separation processes based on cyclone type density media separation (DMS) is presented as an important, potential method for increasing plastics recycling process capacities. It is demonstrated to have the capacity to separate a significantly larger range of particle sizes than those presently processed industrially. The mathematical relationship for the prediction of quality of typical LARCODEMS type density media separations by particle size and density as expressed by the Ecart Probable is presented.A proposed device configuration is presented for density media separation to optimize the recovery and purity of both density fractions produced. It is also suggested that to be economically viable, a large scale of operation is required for industrial plastics recycling operations recovering and producing a number of different plastics with a purity to be used as a substitute for virgin material.     

土工膜渗漏定位方法研究

对偶极子法电极形状和外形尺寸以及其他影响定位的因素进行了深入研究.结果表明:偶极子的检测电压与偶极子的外形尺寸关系不大.偶极子检测电压最大值出现在偶极子中心与漏洞的距离等于偶极子间距的1/2处,并且偶极子的间距越大,检测电压越高.偶极子下沿距离HDPE膜越近,检测电压变化越明显.在多漏洞的情况下,当偶极子的间距小于漏洞间距时,2个漏洞都能被检测出来;当2个漏洞间距小于偶极子间距时,将可能漏检1个漏洞.膜上供电电极的位置对漏洞定位有一定的影响,在测量时应尽可能将供电电极远离测量区.      

电学渗漏检测在防渗土工膜完整性检测中的应用

简述了垃圾填埋场防渗土工膜由于施工造成的破坏情况,通过对目前国外几种垃圾填埋场防渗漏检测方法的比较,指出了电学法是较好的检测方法。利用电学渗漏检测技术对国内某市危险废物安全填埋场防渗土工膜完整性进行了检测,结果表明:利用电学渗漏检测技术对防渗土工膜进行完整性检测具有灵敏度高,检测完全的优点。     

人工合成衬层渗漏检测高压直流电法漏洞电流模型

建立了填埋场渗漏检测高压直流电法漏洞电流模型．将单衬层填埋场看作水平方向为无穷大的3层均匀介质，上层为垃圾层，中间层为人工合成衬层，下层为土壤层．漏洞电流对周围空间电势分布的影响被等效为位于电流流人端的负电流源和位于电流流出端的正电流源对周围空间电势分布的影响膜上漏洞检测通过偶极子法试验、膜下漏洞检测通过电极栅格法试验，结果表明用所建模型计算的理论值与实测值吻合较好．     

聚酯(PET)废塑料分离回收方法研究

日常用的饮料瓶是聚酯和高密度聚乙烯为原是制成的,因而聚酯废塑料瓶是数量较多和回收价值高的一种塑料,本研究首先对聚酯废料瓶进行破碎,然后采用气流分选,清洗净化和水浮选组合工艺进行ＰＥＴ和ＨＤＰＥ及塑纸的分离回收。ＰＥＴ和ＨＤＰＥ的回收率分别为９７％和９５％,同时通过清洗净化可使回收的ＰＥＴ纯度达９６％以上,该ＰＥＴ是一种用途广的优良塑料原料。     

Effect of Decalin Solvent on the Thermal Degradation of HDPE

The thermal cracking of HDPE in presence of different amounts of decalin was studied and compared with the reaction carried out in the absence of solvent. The decalin favours the mass and heat transfer during the reaction. In addition, it modifies the thermal degradation mechanism, which facilitates the formation of specific products. The use of decalin substantially increases the C₅–C₃₂ yield in comparison with the solventless reaction. In all cases, linear hydrocarbons such as n-paraffins, α-olefins and α,ω-dienes were detected. Increasing the decalin/plastic ratio led to enhanced α-olefin and n-paraffins yields, but the increase was more significant in the case of α-olefins, which are valuable compounds useful as raw chemicals. A reaction mechanism was proposed to explain the results obtained in presence of decalin. In these reactions, intramolecular radical transfer, secondary radical β-scission and hydrogen transfer from both decalin to intermediate radicals and from the polymer chain to regenerate the decalin play a significant role in determining the plastic conversion and the relative amounts of each product.     

有机污染物在HDPE膜-膨润土复合防污帷幕中的一维扩散解析解

HDPE膜-膨润土复合防污帷幕被认为是目前最为安全有效的地下污染源阻隔技术之一.针对帷幕底部嵌入不透水层和帷幕下游地下水较为活跃的工况,推导了有机污染物在HDPE膜-膨润土复合防污帷幕三层结构中的一维扩散解析解.利用本文的解析解分析了HDPE膜-膨润土复合帷幕对亲水性和疏水性两类有机污染物的阻隔效果.分析结果表明:由于亲水性有机物与HDPE膜间的分配系数低,该复合防污帷幕对其阻隔效果显著优于具有高分配系数的疏水性有机物.对于疏水性有机物,可通过增大复合帷幕中膨润土的阻滞因子和帷幕厚度来改善其阻隔效果;膨润土的阻滞因子增大10倍且帷幕厚由0.6m增大为1.0m,改进后复合帷幕对疏水性有机物的阻隔效果可达到原帷幕对低分配系数亲水性有机物的阻隔水平.工程实践中可通过对HDPE膜进行表面处理以降低其分配系数或膨润土改性以增大其阻滞因子等措施来增强该复合帷幕的阻隔效果.