Absorption of picoliter droplets by thin porous substrates

Absorption of picoliter (pL) droplets into porous substrates is studied experimentally and numerically. In the case of pL droplets, major phenomena involved in the interaction between droplet and porous media develop at different time scales: spreading and wetting at microseconds, absorption and wicking at milliseconds, and evaporation at seconds. Therefore, one can decouple these processes to minimize the complexity of the study. A high‐speed imaging system capable of 1 million frames per second is used to visualize individual droplets impacting, spreading, and imbibing on substrates. To simulate droplet dynamics, the governing equations for flow outside and inside porous media are proposed and solved using an in‐house developed computational fluid dynamics solver. The simulation results are in good agreement with the experimental data. The effect of drop impact velocity and fluid properties on final dot shape in the porous substrates is investigated through a series of parametric numerical studies. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1690–1703, 2017     

A large‐scale double‐stage‐screw 3D printer for fused deposition of plastic pellets

Fused deposition molding (FDM) is the most popular technology in the fields of three‐dimensional printing, but it is hard to use a variety of plastic materials due to the limitation of filament form of material. Using plastic pellets as printing materials gives advantages in cost, processing speed, and available materials. In this work, a large‐scale double‐screw FDM three‐dimensional printer based on plastic pellets has been designed. It is capable of printing large plastic products at a low cost and high speed. Using ABS + 10%GF as printing material, this work is first focused on the effects of the pressure and speed of the metering screw on the flowrate of melt. The equation for the relationship of these three parameters was established as well. Based on this equation, the effects of melt flow, printing speed, and layer thickness on the width of fused filament were investigated with experiments. Furthermore, the effects of printing spacing between fused filaments on surface accuracy and bonding strength were also explored. By printing models, it was revealed that the designed printer is able to print products with plastic pellets. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45147.     

Synthesis of magnetically separable core–shell structured Ni<Subscript>x</Subscript>Fe<Subscript>1−x</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>@TiO<Subscript>2</Subscript> nanoparticles photocatalysts for the degradation of organic dyes

In this paper, the core–shell structured NiFe₂O₄@TiO₂ nanoparticles and nanochains as photocatalysts were successfully prepared through hydrothermal and hydrolysis method. The as-prepared core–shell structure was composed of a magnetic NiFe₂O₄ core and photocatalytic titanium oxide coating shell. SEM and TEM images characterized the morphology of NiFe₂O₄@TiO₂ nanoparticles. Moreover, the results of XRD patterns proved that the TiO₂ coating shell consisted of anatase. The VSM measurements showed that the saturation magnetization values of NiFe₂O₄ and NiFe₂O₄@TiO₂ nanoparticles was 65 and 53 emu/g, respectively. The photocatalyst of NiFe₂O₄@TiO₂ nanoparticles exhibited the outstanding recyclable performance for RhB. And, the photo_degradation ration of maintained 69 % after the photocatalyst experienced ten photocatalysis experiments, which is better than that of Fe₃O₄@TiO₂ photocatalysts.     

复配混凝剂强化处理生活污水试验研究

择优选取对TP及COD去除效果均较优的3种混凝剂AlCl_3、FeCl_3、Fe_2(SO_4)_3,以依次投加的方式进行复配,考察了复配混凝剂对生活污水中TP和COD的去除效果及影响因素。研究结果表明,当复配混凝剂按m(AlCl_3)∶m(FeCl_3)∶m〔Fe_2(SO_4)〕=5∶6∶7投加时,对污染物的去除效果最好;pH是影响污染物去除效果的关键因素;在最佳配比条件下,当复配混凝剂投加量为160 mg/L时,出水TP可达0.402 mg/L,达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级A标准,COD去除率比单一混凝剂高12.9%~20.1%。     

焦化废水膜法组合深度处理工艺设计与应用

针对煤化工企业焦化废水的二级生化出水可生化性差、含盐量与COD高,以及废水中包含多环芳香族化合物、脂肪族化合物等难生物降解污染物的特点,采用Fenton氧化+电渗析+超滤+反渗透膜法组合深度处理工艺对废水进行处理。运行结果表明,产水水质达到并优于《工业循环冷却水处理设计规范》(GB 50050—2007)中再生水水质要求,产水可作为厂区生产补充新水使用,废水回收率稳定达到75%。采用Fenton氧化与电渗析粗脱盐技术相结合的强化预处理设施,可以有效缓解反渗透装置的膜污染,延长反渗透膜的清洗周期至3个月。     

催化裂化干气乙烯回收利用技术研究进展

催化裂化干气中含有乙烯,其回收和利用问题已成为现今的研究热点。文章阐述了国内外催化裂化干气乙烯回收利用技术现状和最新进展,为更好得实现催化裂化干气的回收利用,应加强催化裂化粗乙烯利用工艺的开发研究。     

电解锰渣的理化特性与物相转变研究

电解锰渣是电解锰过程中产生的酸性固体滤渣,含有大量有害物质,会引发了严重的水土和环境污染。采用粒度仪、XRF、XRD、DSC-DTG/TG和SEM等,本实验测试了锰渣的理化特性、化学成分、矿物组成、物相转变和组织形貌。结果发现,锰渣颗粒细小,形貌不规则,含水率高。锰渣主要由石英(SiO_2)和石膏(CaSO_4·2H_2O)组成,其化学成分主要为SiO_2、Al_2O_3、CaO、MgO、Fe_2O_3和残留MnO等氧化物。加热时,锰渣脱水和气体排放严重,其中的二水硫酸钙发生物相转变以及分解为SO_3气体,造成二次污染,在1091.7℃时,锰渣则完全熔化成玻璃相。     

一种具有核-壳结构水性改性醇酸的工业化合成工艺

本文介绍了一种已工业化具有核-壳结构丙烯酸环氧改性的水性醇酸树脂合成的新工艺,该产品合成包括加压反应合成亲水丙烯酸壳结构;疏水环氧改性醇酸核结构;核壳键合反应;水分散体的制备共四个阶段。合成的产品油度约为50%左右,具有耐水性优异、光泽高、干燥速度快、防锈性能好等诸多优点,具有很好的市场前景。     

反硝化墙去除地下水硝酸盐研究进展

地下水硝酸盐污染越来越来越严重,过量摄入硝酸盐严重危害人类和家畜健康。反硝化墙是一种建造简单、无需管理维护的地下水硝酸盐原位修复技术。本文总结了反硝化墙对地下水中硝酸盐的去除效果、填充碳源种类、使用寿命及不利影响。     

国内城市埋地管道泄漏事故案例分析及预防

近几年,国内城市埋地管道泄漏事故频发,导致重大的人员伤亡和财产损失。本文搜集了2005~2014年国内城市的埋地管道泄漏事故,分析了埋地管道泄漏事故类型及发生原因。结果表明:约50%的埋地管道事故为燃气管道泄漏事故。工业管道和热力管道事故更容易引发人员伤亡。城市埋地管道泄漏的主要原因是外部人为因素而非技术原因,尤其是第三方施工。针对性提出了3种埋地管道泄漏预防措施。