Thermal cracking of waste printed wiring boards for mechanical recycling by using residual steam preprocessing

Mechanical waste-processing methods, which combine crushing and separation processes for the recovery of valuable materials, have been widely applied in waste printed wiring board (PWB) treatment. However, both the high impact toughness and the tensile and flexural strengths of whole PWB with a laminated structure result in great energy consumption and severe abrasion of the cutters during multi-level crushing. In addition, the high temperatures occurring in continual crushing probably cause the decomposition of the polymer matrix. A thermal-crack method using residual steam as the heating medium has been developed to pre-treat waste PWBs. This treatment reduces the mechanical strength in order to improve the recovery rate of valuable materials in subsequent mechanical recycling. The changes of the PWBs’ macro-mechanical properties were studied to evaluate thermal expansion impacts associated with changes in temperature, and the dynamic dislocation micro-structures were observed to identify the fracture mechanism. The results showed that thermal cracking with steam at the temperature of 500 K can effectively attenuate the mechanical properties of waste PWBs, by reducing the impact, tensile and flexural strengths respectively, by 59.2%, 49.3% and 51.4%, compared to untreated PWB. Thermal expansion can also facilitate the separation of copper from glass fiber by reducing peel resistance by 95.4% at 500 K. It was revealed that the flexural fracture was a transverse cracking caused by concentrated stress when the heating temperature was less than 500 K, and shifted to a vertical cracking after exceeding 500 K.     

夏季太湖蓝藻水华暴发与臭氧污染的关联性

夏季受东南季风、湖流等因素影响,太湖蓝藻向西北部水域集聚,该区域平均藻密度可高达1×109个/L以上,其中蓝藻集中堆积的近湖岸区域藻类密度更高,蓝藻在不同生命阶段释放的藻源性VOCs的成分谱和产生量有较大差异,其中烯烃和有机胺反应活性较强。蓝藻水华高发期太湖西岸非甲烷总烃的浓度约为常州市区的3.3倍,日变化趋势符合蓝藻代谢规律。太湖西部蓝藻水华、湖西区的非甲烷总烃浓度和臭氧污染程度时空变化规律表明:太湖西部(宜兴)是整个流域臭氧污染最严重的区域,其臭氧污染的形成与太湖蓝藻水华暴发有关联性。     

煤层注水降低综采工作面煤尘浓度的研究

在深入研究官地矿９＃ 煤渗透特性的基础上,提出动压预注水的煤层注水方案与参数,并在官地矿进行了工业性试验,取得了降低综采工作面煤尘浓度６０％ 以上的明显效果。它对我国煤矿有效实施煤层注水、降低工作面粉尘浓度具有实际指导意义     

城市污水处理厂建设中节省投资措施

以某污水处理厂工程建设为例，从不同的角度提出在污水处理厂建设过程中节省投资的一些措施。     

我国废钢加工装备发展现状与展望

以绿色经济和循环经济的重大需求为背景,系统阐述了废钢加工装备的现状与发展,详细介绍了废钢加工装备的种类与用途,分析并总结了废钢加工装备的应用现状,指出了废钢加工装备以及废钢加工行业的发展方向。     

Preparation and Characterization of Collagens from the Skin of Northern Snakehead (<Emphasis Type="Italic">Channa argus)</Emphasis>

Channa argus, a type of snakehead fish native to China, is a popular food fish in certain Asian countries but is a known destructive invasive species in the US. In this study, the two collagens, i.e. acid-soluble collagen (ASC) and pepsin-solubilized collagen (PSC), were obtained from C. argus skin. The yield of ASC was 28.0% and that of PSC was 16.8% on the dry bases. The collagens were identified as the collagen of type I by SDS–PAGE patterns. The Tds were approximately 27.0?°C. Similar ultraviolet spectra of both collagens were observed. Fourier Transform infrared spectra indicated PSC structure had a little change due to the loss of terminal domains by pepsin digestion. The results of XRD proved that the two collagens retained their helical structures. The results suggest that the collagens isolated from C. argus can potentially be alternative sources of vertebrate collagens for use in the food and other industries.     

爆炸焊接的安全评估和安全防护措施

根据爆炸焊接的装药特点,对爆炸焊接炸药的使用、爆炸产生的地震波、毒气、噪音等的安全性进行了分析,给出了定量的计算公式,同时还针对不同的爆破危害,提出了相应的安全防护措施     

北京市典型土著沉水植物对水体中硝酸盐和正磷酸盐的耐受性研究

以北京市3种典型土著沉水植物轮叶黑藻、狐尾藻和金鱼藻为研究对象,构建模拟水生生态系统,研究3种沉水植物对水体中NO₃^-和PO₄^3-的耐受性并确定其耐受范围.同时,对植物体内过氧化氢酶、丙二醛、叶绿素和蛋白质4种指标进行检测.结果表明,轮叶黑藻对NO₃^-具有较强的耐受性,耐受浓度可达8 mg·L^-1,金鱼藻和狐尾藻次之,耐受浓度为3~5 mg·L^-1;狐尾藻对PO₄^3-的耐受性最差,耐受浓度约为0.2 mg·L^-1,轮叶黑藻和金鱼藻的耐受性相当,当PO₄^3-浓度达到0.4 mg·L^-1时开始出现显著胁迫.因此,在本研究的实验条件下,当水体NO₃^-浓度<5 mg·L^-1、PO₄^3-浓度<0.2 mg·L^-1时,建议3种沉水植物同时种植;当NO₃^-浓度>5 mg·L^-1时,建议种植轮叶黑藻;当PO₄^3-浓度为0.2~0.4 mg·L^-1时,建议种植轮叶黑藻和金鱼藻.研究结果可为北京市再生水补给河湖水库的水生态修复及其沉水植物群落的构建提供一定的理论指导.     

Phosphorus adsorption by functionalized biochar: a review

Environmental Chemistry Letters - Phosphorus is essential element for agricultural production, yet phosphorus ore resources are non-renewable and become depleted. Moreover, phosphate release from...     

工业点源大气污染扩散空间信息系统

开发了一个基于高斯扩散的大气污染扩散空间信息系统,用于模拟工业点源污染对区域大气质量的影响。该工业点源污染模型包括工业点源数据库、扩散参数、气象条件和大气质量评价4个主要数据库。用该模型计算上海市主要工业区的SO2排放,结果表明,该模型为模拟SO2污染扩散提供了一个有效便捷的方法。