Flocculants—an Ecofriendly Approach

Although water-soluble synthetic polymers find wide applications as flocculants, the potential problem associated with their use is lack of biodegradability and high cost. Polysaccharides owing to their distinctive features like ability to undergo different chemical reactions, biodegradability and sustainability inspire hope to obtain effective, economical viable and safe substitute of the synthetic flocculants. In this regard, chemical modification of Cassia tora and guar gum was carried out through different substitution and grafting reactions. The modified products were tested against kaolin under laboratory conditions vis-a-vis polyacrylamide based synthetic flocculant.     

Degradation of Commercial Biodegradable Packages under Real Composting and Ambient Exposure Conditions

The use of long-lasting polymers as packaging materials for short lived applications is not entirely justified. Plastic packaging materials are often soiled due to foodstuffs and other biological substances, making physical recycling of these materials impractical and normally unwanted. Hence, there is an increasing demand for biodegradable packaging materials which could be easily renewable. Use of biopolymer based packaging materials allows consideration of eliminating issues such as landfilling, sorting and reprocessing through taking advantage of their unique functionality, that is compostability. Composting allows disposal of biodegradable packages and is not as energy intensive compared to sorting and reprocessing for recycling, although it requires more energy than landfilling. The aim of this work was to study the degradation of three commercially available biodegradable packages made of poly (ld-lactide) (PLA) under real compost conditions and under ambient exposure by visual inspection, gel permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. A novel technique to study the degradability of these packages and to track the degradation rate under real compost conditions was used. The packages were subjected to composting for 30 days, and the degradation of the physical properties was measured at 1, 2, 4, 6, 9, 15 and 30 days. PLA packages made of 96% l-lactide exhibited lower degradation than PLA packages made of 94% l-lactide, mainly due to their highly ordered structure, therefore, higher crystallinity. The degradation rate changed as the initial crystallinity and the l-lactide content of the packages varied. Temperature, relative humidity, and pH of the compost pile played an important role in the total degradation of the packages. A first order degradation of the molecular weight as a function of time was observed for the three packages.     

醇类助溶剂去除砂土中多氯联苯作用机制

醇类助溶剂单一使用及复配表面活性剂使用去除砂土中多氯联苯(PCBs)的关键是增溶和降低界面张力.通过降低界面张力实验和振荡增溶实验分析了醇类助溶剂单一使用对多氯联苯界面张力的降低作用和增溶作用,以及醇类复配Triton X-100使用时醇对Triton X-100降低界面张力和增溶PCBs的影响.结果表明,醇-PCBs油的界面张力与醇浓度、醇含碳原子数均呈负相关,甲醇、乙醇、异丙醇的最佳解吸浓度分别为70%、55%、40%,最佳解吸效率达90%以上;Triton X-100-PCBs油界面张力与Triton X-100浓度呈负相关,Triton X-100浓度低于3 000 mg/L时复配10%乙醇、10%异丙醇比单一Triton X-100振荡洗脱效率低,Triton X-100浓度在3 000～7 500 mg/L时3组差异不大,Triton X-100浓度为10 000 mg/L时单一、10%乙醇、10%异丙醇TritonX-100溶液解吸效率分别为80.9%、90.36%、89.36%.表明醇类单一使用对降低界面张力与增溶均有很好的效果,但需要其体积分数达40%以上;醇类复配Triton X-100时醇的存在弱化了Triton X-100增溶和降低界面张力的作用,乙醇与异丙醇弱化作用差异性不大,当Triton X-100浓度高于3 000 mg/L时,弱化作用不显著.     

微乳液和混合表面活性剂对甲苯的增溶作用

以Tween系列非离子型表面活性剂及助表面活性剂组成的混合表面活性剂溶液作为增溶试剂,增溶吸收难溶有机物甲苯。结果表明,当表面活性剂浓度大于临界胶束浓度(CMC)时增溶效果显著,甲苯的表观溶解度与表面活性剂浓度呈线性关系,且随着表面活性剂浓度的增加而增大,增溶曲线在CMC处出现折点;微乳液较单一表面活性剂溶液对挥发性有机物甲苯的增溶能力更强,增溶比更大;添加助表面活性剂可以不同程度的提高表面活性剂溶液的增溶能力,其规律为:正丁胺正丁醇正丁酸;温度对微乳液及混合表面活性剂溶液的增溶作用有很大的影响,且低温条件更有利于增溶吸收挥发性有机物甲苯。非离子型微乳液是一种良好的增效试剂,在挥发性有机废气污染治理中具有较好的应用前景。     

不同组分鼠李糖脂的胶束性质及其对三氯生的增溶作用

测定了铜绿假单胞杆菌诱变株MIG-N146产鼠李糖脂粗提物（RL-CE）及经柱层析分离纯化得到的单糖脂（RL-F1）和双糖脂（RL-F2）的表面性能及胶束性质,并通过溶解平衡实验考察了这3种组分对极性疏水物质三氯生的增溶作用.结果表明,RL-CE、RL-F1、RL-F2的临界胶束浓度CMC值分别为60.31、43.82...     

Solubilization and degradation of perchloroethylene （PCE） in cationic and nonionic surfactant solutions

Solubilization of perchloroethylene (PCE) in a nonionic (Triton X-100) and a cationic (cetyltrimethylammonium bromide (CTAB)) surfactant solutions and the degradation of surfactant solubilized PCE using fine to nanosize Fe and bi-metallic Fe-Ni particles were investigated. Micelle partition coefficients (Km) and molar solubility ratio (MSR) for PCE in 10 g/L of surfactant solutions have been quantified and the solubility of PCE (100 mg/L in water) in the surfactant solutions increased by about ten fold. Of the two surfactants studied, Triton X-100 solubilized the higher amount of PCE per gram of surfactant. To degrade solubilized PCE, both iron and bimetallic Fe-Ni particles were used in continuously stirred batch reactors. The iron and bi-metallic particles were synthesized using the solution method and the particles were characterized using the SEM, EDS, TEM and XRD. The PCE solubilized up to 500 mg/L in both surfactant solutions were totally degraded at various rates by 200 g/L of bi-metallic Fe-Ni particles in less than 20 hr, which is the highest concentration of PCE degraded in the shortest time compared to data in the literature. The degradations of PCE solubilized in surfactant solutions were represented by nonlinear kinetic relationships which depended on the type of surfactant used for solubilizing the PCE.     

阴-非混合表面活性剂对DNAPLs的增溶作用

表面活性剂增溶修复是一种有效的土壤有机污染修复技术.采用静态平衡法比较研究了单一的阴离子表面活性剂十二烷基硫酸钠(SDS)和非离子表面活性剂聚氧乙烯失水山梨脂肪酸酯醇醚(TWSO)及其混合表面活性剂对3种氯代烃化合物氯苯(CB)、1,2-二氯苯(1,2-DCB)和三氯乙烯(TCE)的增溶作用.考察了无机盐离子Na 、M2 和Ca2 对增溶作用的影响,以期为土壤和地下水重非水相液体(DNAPLs)污染提供新的修复途径.结果表明,阴-非混合表面活性剂TW80-SDS对3种化合物的增溶效果明显强于单一的阴离子表面活性剂SDS,混合表面活性剂的临界胶束浓度(CMC)随着非离子表面活性剂质量分数的增加而降低,其增溶能力随着非离子表面活性剂质量分数的增加而增加,对污染物的增溶程度排序为:三氯乙烯＞氯苯＞1,2-二氯苯.表面活性剂在临界胶束浓度以上,对有机物的分配系数Kmc与有机物的辛醇-水分配系数Kow相当,而增溶比与有机物的水溶解度呈正相关,与Kow、kow、溶质的摩尔体积和表面活性剂的亲水-亲油平衡值HLB呈负相关.Na 、Mg2 和Ca2 能增大氯苯在表面活性剂中的表观溶解度,阴非离子表面活性剂SDS与TW80混合后能提高表面活性剂的抗硬水能力,提高增溶效率.     

表面活性剂增效修复土壤有机污染研究进展

系统评述了表面活性剂增效修复土壤有机污染的原理、研究现状及存在的问题.     

桑色素-吐温-20胶束增溶分光光度法测定微量铁

本文对铁（Ⅲ）与桑色素（Ｍｏｒｉｎ）的显色反应进行了研究。在非离子表面活性剂吐温－２０存在下，于ｐＨ４．１的邻苯二甲酸氢钾缓冲溶液中，铁（Ⅲ）与桑色素形成稳定的黄色配合物，其组成比为Ｆｅ（Ⅲ）∶Ｍｏｒｉｎ＝１∶３，最大吸收波长为４１８ｎｍ，表观摩尔吸光系数为６．６９×１０４Ｌ／ｍｏｌ·ｃｍ，铁（Ⅲ）浓度在０～１６μｇ／２５ｍｌ范围内符合比耳定律。方法简便、快速，选择性好。应用于环境水样和植物中微量铁的测定，结果满意。     

典型表面活性剂对焦化污泥中富集多环芳烃的解吸

焦化废水中的多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)由于其亲脂性极易转移至污泥相中,此过程成为微生物降解污泥中PAHs的传质受限步骤.基于表面活性剂解吸焦化污泥中富集的PAHs以利于微生物降解的构想,采用两种典型的表面活性剂—Triton X~(-1)00和十二烷基硫酸钠(Sodium Dodecyl Sulfate,SDS)来考察其对菲、芘和苯并[a]芘的增溶作用,对比了不同浓度的菲、芘和苯并[a]芘在焦化污泥上的吸附特征,探讨了表面活性剂对焦化污泥中富集多环芳烃的解吸行为.结果发现,表面活性剂对菲、芘和苯并[a]芘的增溶能力与三者的亲脂性存在负相关的关系,它们在焦化污泥上的吸附特征可用Freundlich等温吸附模型来描述,影响吸附容量的因素包括PAHs的亲脂性和焦化污泥的理化性质;SDS与Triton X~(-1)00共同作用时对芘和苯并[a]芘的增溶更明显;以两者混合质量计的1 g表面活性剂在16 d内可以解吸1.12mg的总PAHs.上述研究可以作为焦化污泥生物修复的增溶工艺中表面活性剂需求量计算的参考依据.