Linear alkylbenzene

Linear alkylbenzene (LAB) was introduced in the mid-1960s as a raw material for cleaning products. Since then, continuing and explosive research on its biodegradation and on its environmental and human toxicity has been performed. The efficiency of linear alkylbenzene sulfonate as surfactant is clearly established, and it is one of the safest and most cost-effective products in widespread commercial use. The aim of the present paper is to survey the most important developments and understandings of the chemistry of LAB production and of its physical and environmental properties. The expected consequence of this analytical survey is to envisage the continuous challenges for the detergents industry in catalytic production of LAB, better control of selectivity, replacement of corrosive and mineral liquid acid catalyst by heterogeneous acid catalyst and the maintenance of competitiveness of LAB with respect to natural alcohols.     

Cometabolic transformation of linear alkylbenzenesulphonates by methanotrophs

Cometabolic transformation of commercial linear alkylbenzenesulphonates (LAS) and pure congeners of 2-[4-(sulphophenyl)]nonan (2C₉LAS) and 2-[4-(sulphophenyl)]decan (2C₁₀LAS) was studied by using a mixed methanotrophic-heterotrophic culture MM1 and a pure culture of type II methanotroph (strain CSC1), isolated from culture MM1. Cultures were grown in shake flasks under conditions promoting expression of the soluble methane monooxygenase (sMMO). Both the mixed culture MM1 and the pure culture CSC1 were capable of transforming LAS with or without methane as the natural substrate. Experiments performed without methane (resting cells) showed faster cometabolic transformation of LAS congeners with longer alkyl side-chains. Both 2C₉LAS and 2C₁₀LAS congeners were transformed significantly faster at 30°C, although the optimum temperature for the growth of mixed culture MM1 was 20°C. Simultaneous methane oxidation and LAS transformation, and their mutual competitive inhibition, indicated the involvement of the MMO enzyme system and possible methanotrophic activity in the initiation of cometabolic LAS transformation. The capability of two heterotrophic species to transform sulphophenyldecanoic acid suggests possible heterotrophic activity in further LAS transformation (β-oxidation). Faster LAS transformation by mixed culture MM1 than by pure culture CSC1 suggested that methanotrophic-heterotrophic interactions are important for transformation of the complex LAS molecule.     

Imaging the Detergency of Single Cotton Fibers with Confocal Microscopy: the Effect of Surfactants and Lipases

Detergency mechanisms of lipids from single cotton fibers were visualized by means of confocal laser scanning microscopy (CLSM). Fibers were soiled with different types of lipids: olive oil, lard and tri-C₁₀, and subsequently stained with the fluorescent probe Nile Red. A surfactant composition of 300 μM C₁₂E₆/LAS (1:2 mol%) was used to mimic the surfactants used in a common washing solution. It was evident from the captured image series that the different kinds of soiling were removed by different mechanisms by the surfactants, depending on the fluidity of the lipid. Roll-up was the main mechanism when removing olive oil, whereas emulsification (necking) and/or solubilization were observed in the removal of lard and tri-C₁₀. Only 20–25% of the olive oil remained after treatment with surfactants, which was much less compared to the solid fats where roughly 50% remained at end of treatment. The effect of adding lipases to the detergent formulation was clearly seen, both by an apparently higher rate of removal of olive oil but also using double injection when removing lard. A first injection of only surfactants removed a certain part of the lard as emulsion droplets stuck onto the fiber. A second injection of both lipases and surfactants was able to remove some of the preformed emulsion particles and reduce the overall remaining lard content on the cotton fiber.

粉末活性炭应急处理模拟突发LAS污染源水试验研究

论文考察了粉末活性炭预吸附对模拟突发阴离子表面活性剂(LAS)污染源水的应急处理效果,利用烧杯实验研究了粉末活性炭的炭种、投加量、吸附时间、混凝剂种类以及投加量对粉末活性炭预吸附消除LAS的影响。进行了为期约一个月,处理规模为4m3/h的中试试验,考察了常规处理对含LAS源水的处理效果,优化了活性炭投加点,并且探寻了粉末活性炭预吸附对模拟突发LAS污染源水的处理能力。烧杯实验结果表明木质活性炭对LAS的去除效果优于煤质活性炭,优化的投加量为30mg/L,吸附时间30min以上。活性炭吸附后投加混凝剂(PAC)20mg/L可达最佳效果。中试结果表明常规处理对含LAS源水处理效果差,滤后去除率低于5%。活性炭投加点宜设在常规处理前端,接触时间45min。采用粉末活性炭预吸附应急处理突发LAS污染源水,在LAS超标6倍以下,滤前出水可达标。粉末活性炭预吸附应急技术可行性高,处理费用仅0.0255元/m3,为可能突发的水源LAS污染事故应急处理提供了技术支持。     

基于劳伦多项式的LAS码构造及性能分析

对基于Hadamard矩阵的LA码和基于劳伦多项式(Laurent Polynomial)的LS码的生成及相关特性进行研究,从占空比、相关特性、零干扰窗长度、码字总数等方面仿真分析了LAS码的性能,并结合实际应用,理论分析了LAS-CDMA系统与传统CDMA系统的归一化容量,仿真比较了LAS码和Gold序列在准同步CDMA系统中的误码性能.仿真和理论分析表明:LAS码具有均匀的零干扰窗(Interference Free Window,IFW)特性;不同主码的互相关函数IFW附近存在较小的副峰,多址干扰较小;在准同步移动通信系统中,LAS-CDMA抗多址干扰性能明显优于传统CDMA系统,使用LAS码比使用Gold序列有更好的误码性能.     

复合混凝剂RX处理合成洗涤剂生产废水的研究

以硫酸亚铁、硫酸铝、硫酸镁、氯化钙、氢氧化钙、活性炭粉末和聚丙烯酰胺(PAM)等为原料合成了一种复合混凝剂RX,并将其用于处理合成洗涤剂生产废水.试验研究表明,RX对LAS和COD的去除效果较好,优于PAC和PFS,且用量少,费用低,出水水质好.其最佳处理条件为:pH为7～9,RX投加量150 mg/L,PAM投加量0...     

短切SiCf/LAS复合材料的显微结构与介电性能

采用热压烧结法制备出致密的短切SiC_f增强LAS玻璃陶瓷复合材料,并讨论保温时间与热压压力对复合材料介电性能的影响.结果表明,测试频率在8～12 GHz之间,复合材料复介电常数实部ε′由基体的7.6上升到10～100,虚部ε″由基体的0.34上升到40～160,介电损耗tgδ由基体的0.04上升到1～20,并具有明显的频散效应.随保温时间的延长或热压压力的提高,复合材料ε′增大,ε″与tgδ减小.此外,断口形貌的SEM观察表明,随保温时间的延长或热压压力的提高,复合材料界面层变厚.     

不同表面活性剂类型对铜绿微囊藻生长影响研究

通过以3种表面活性剂(AEO9、混合表面活性剂、LAS)和铜绿微囊藻(Microcystis aeruginosa)为研究对象,以表征铜绿微囊藻生长的参数OD650和Act.chl为观测指标,研究了不同浓度(0.05、0.5、5、10、20mg/L)的3种表面活性剂对铜绿微囊藻生长的影响。结果表明:AEO9、混合表面活性剂、LAS的所有浓度组的OD650、Act.Chl.值均随着胁迫时间的延长而增大,但总体而言,AEO9所有浓度组增长速率最大,混合表面活性剂浓度组次之,LAS浓度组最小。另外,该藻对AEO9、混合表面活性剂及LAS3种不同类型表面活性剂的最适生长浓度分别是20、10mg/L和5mg/L。     

Effect of linear alkylbenzene sulphonates (LAS) on the anaerobic digestion of sewage sludge

Batch anaerobic biodegradation tests with different alkylbenzene sulphonates (LAS) at increasing concentrations were performed in order to investigate the effect of LAS homologues on the anaerobic digestion process of sewage sludge. Addition of LAS homologues to the anaerobic digesters increased the biogas production at surfactant concentrations 5-10 g/kg dry sludge and gave rise to a partial or total inhibition of the methanogenic activity at higher surfactant loads. Therefore, at the usual LAS concentration range in sewage sludge, no adverse effects on the anaerobic digesters functioning of a wastewater treatment plant (WWTP) can be expected. The increase of biogas production at low surfactant concentrations was attributed to an increase of the bioavailability and subsequent biodegradation of organic pollutants associated with the sludge, promoted by the surfactant adsorption at the solid/liquid interface. When the available surfactant fraction in the aqueous phase instead of the nominal surfactant concentration was used to evaluate the toxicity of LAS homologues, a highly significant relationship between toxicity and alkyl chain length was obtained. Taking into account the homologue distribution of commercial LAS in the liquid phase of the anaerobic digesters of a WWTP, an EC(50) value of 14 mg/L can be considered for LAS toxicity on the anaerobic microorganisms.     

SiC_f/LAS玻璃陶瓷基复合材料的界面

:详细评述了SiCfLAS玻璃陶瓷基复合材料的界面。该界面是在热压过程中形成的,由富碳层或富碳层和碳化物层构成,这些界面层的存在导致了界面的弱结合。界面具有很好的热相容性。在惰性气氛或还原性气氛中,界面具有很好的热稳定性。在高温氧化性气氛中,界面层很快因氧化而消失,导致纤维与基体间的强结合,使材料发生脆断。