Biodegradation of sodium linear alkylbenzenesulfonates evaluated with a soil perfusion method

In order to explain biodegradation behavior of sodium alkylbenzenesulfonate (LAS) in the soil environment, a soil perfusion method has been applied. This method is one of continuous enrichment cultures with soil. The degree of degradation of LAS was evaluated by measuring the amount of ferroin reagent active substances (FRAS) instead of methylene blue active substances (MBAS) and/or of total organic carbon (TOC) in the perfusion fluid. The biodegradation of LAS started after adsorption onto soils. At high LAS concentrations, the biodegradation occurred after some lag phase, but further added LAS was degraded readily without a lag phase. These results of biodegradation are in good agreement with those obtained from the biodegradation tests on river water and activated sludge, and reproducible results were obtained for the soil perfusion with the same soil. This proves the soil perfusion method to be a useful method for evaluation of biodegradation in the soil environment.     

Aquatic environmental monitoring of detergent surfactants

Since 1998, Japan Soap and Detergent Association has been continuously evaluating the concentrations of four surfactants used in household detergents and fabric conditioners in river surface water: linear alkylbenzene sulfonate (LAS), polyoxyethylene alkyl ether (AE), alkyldimethylamine oxide (AO) and dialkyl dimethylammonium chloride (DADMAC) in Japanese urban rivers, in order to assess the risks of surfactants on aquatic organisms. Surfactant concentrations in the river water in June and September were found to be lower than those in March and December, the season where water temperature is lower, suggesting that the rates of biodegradation in environmental water differ depending on the water temperature. All the measured surfactant concentrations were below the reported predicted no-effect concentration (PNEC) and have been decreasing year by year; suggesting that surfactant risk on aquatic organisms in Japanese rivers is low under current conditions.     

Biodegradation of synthetic detergents evaluation by community trials: I. Linear alkylbenzene sulphonates

The biodegradability of a number of linear alkylbenzene sulfonates (LAS) has been evaluated by field trials with a trickling filter sewage plant serving a small community. All the LAS material examined showed a satisfactory order of biodegradability. In all the LAS materials examined, aeration of the sewage effluent resulted in further biodegradation to a degree corresponding to 96% to 99% degradation of the LAS present in the settled sewage. The results of laboratory scale biodegradation tests are largely in agreement with those obtained in the field trials. However, with tests of the simple open bottle type, such as the test of the U.K. Standing Technical Committee on Synthetic Detergents, misleading indications of low biodegradability may sometimes be obtained on products of higher molecular weight. Such products do not appear to acclimatize sufficiently rapidly to bacteria under the conditions of the open-bottle test. Under practical sewage treatment conditions, or with tests which simulate these, a high order of biodegradation is obtained. There were only minor differences in biodegradability between an LAS derived from paraffins and those derived from cracked wax olefins.     

Use of certain alcohol ethoxylates to maintain protease stability in the presence of anionic surfactants

Anionic surfactants, including linear alkylbenzene sulfonate (LAS), are known to decrease the stability of detergent proteases, possibly by hastening autoproteolytic processes. Thus, protease shelf life in enzyme-containing, heavy-duty liquid laundry detergents (HDL) is typically maintained by adding stabilizers, by limiting the level of interfering anionics, or by utilizing more compatible anionics, such as alcohol ethoxysulfates (AES). This study examines the stability of Savinase^® detergent protease in HDL formulations based on LAS and containing different alcohol ethoxylates (AE) for protection against protease inactivation. Dose response curves demonstrated that all commonly used anionic surfactants except AES promote loss of protease activity. In HDL formulations with equal percentage compositions of LAS and AE, the structure of the selected AE was found to have a profound influence on protease stability. Inclusion of AE with chain length ≥C₁₄ and ethoxylate levels >70% resulted in greater protease stability. HDL containing LAS and these protective AE could be formulated to achieve protease stability matching those of simulated commercial products. Unlike polyhydric stabilizers, the AE by themselves confer no additional stability to the protease. It is more likely that the stabilizing effect of the “protective” AE is due to decreased availability of LAS to the protease.     

Kinetics and practical significance of biodegradation of linear alkylbenzene sulfonate in the environment

This paper reviews the kinetics of biodegradation of linear alkylbenzene sulfonate (LAS) in engineered (wastewater treatment) and natural environment systems, focusing on work conducted in our environmental laboratories over the past 10–15 yr. Biodegradation studies were conducted in laboratory microcosms in which pure-chainlength [¹⁴C]-ring-labeled LAS homologs were used to allow complete mineralization to be assessed. In general, biodegradation rates for a series of LAS homologs (C10–C14) were comparable to each other and to values for naturally occurring materials such as sugars and fatty acids. Half-lives for LAS mineralization ranged from 1–2 d in aerobic and anaerobic sewage sludges, river water and sediments, to 1–3 wk in surface and subsurface soils and estuarine environments. The half-life for LAS degradation in different environmental compartments, relative to its residence time in these compartments, makes biodegradation a practically significant removal mechanism in a broad range of aquatic, benthic and terrestrial habitats.     

Biodegradation of nonionic ethoxylates

The biodegradation of alcohol ethoxylates (AE) and alkylphenol ethoxylates (APE) is reviewed. Biodegradation test methods, ranging from laboratory tests to full-scale waste treatment plant studies are described for these surfactants. A comparison is made between primary and ultimate biodegradability criteria and the limitations of the various analytical methods used in these determinations are discussed. The most recently published data suggest sewage bacteria degrade AE by a mechanism which is different from that by which APE degrades. The use of radiolabeled surfactants to elicit more detailed information about the biodegradation mechanisms of AE is described. The role of biodegradation on the impact of surfactants released to the environment is assessed, and future environmental concerns for nonionics are considered.     

The behaviour of LAS in the environment

During the last few years a considerable amount of information about the biodegradation of linear alkylbenzene sulfonates (LASs) in real environmental situations has been made available. This paper reviews the existing LAS concentrations found today in the environment, using specific analytical techniques for this surfactant, as well as its mineralization and fate in compartments such as sludge amended soils. LAS is totally decomposed into carbon dioxide, water and inorganic sulfate without formation of stable metabolites, and no accumulation has been detected in the compartments studied. The highest degree of biodegradation (>95%) takes place in the processes (sewers and sewage treatment plants) showing the shortest half lives (1–10 h).     

Biodegradability of linear alkylbenzene sulfonates subjected to wet air oxidation

Shake flask experiments were conducted to determine the biodegradability of aqueous linear alkylbenzene sulfonate (LAS) and LAS (1600 mg dm^?3) subjected to wet air oxidation (WAO), to assess the suitability of WAO as a pre‐treatment for biological degradation. The effects of WAO temperature (180–240 °C) and the concentration of the orthophosphoric acid catalyst (0–1.0 mol dm^?3) were investigated. Results showed that a higher WAO temperature increased the biodegradability of the WAO effluent. This was due to a greater removal of both recalcitrant sulfonated organics and organic concentration (TOC and COD). Conversely, greater orthophosphoric acid concentrations decreased the biodegradability of the WAO effluents. This was because the higher acid concentration increased the ionic strength and changed the WAO intermediate and product distribution, inhibiting microbial action. Nevertheless, the effluents from both variations of WAO were still more biodegradable than LAS at equivalent concentrations. However, since higher WAO temperatures can substantially increase capital costs, future work should focus on developing a WAO catalyst that both desulfonates and mildly oxidises LAS at moderate temperatures (200 °C). © 2002 Society of Chemical Industry     

Residual strength estimation of CFRP laminates subjected to impact at different velocities and temperatures

This paper demonstrates the results of an experimental study on cross ply carbon/epoxy composite laminates fabricated from high temperature hardener HT972 subjected to impact loading at different velocities and temperatures. The carbon fiber reinforced plastic (CFRP) samples were impacted at velocities 1.5 m/s and 2.5 m/s, each at a temperature level of 30°C, 60°C, 90°C, and 120°C. The impact response of the material towards various velocities and temperatures was determined using impact parameters like peak force, absorbed energy, maximum deflection, and rebound velocity. Result reveals that the velocity and temperature play a significant role in the impact response of the material. The variation in the trend of Flexural After Impact (FAI) strength of composite laminates at different velocities and temperatures was determined using FAI test and these results were further correlated with impact results. The dominating failure modes affecting the residual strength of the samples were found using acoustic emission (AE) monitoring. POLYM. COMPOS., 38:2182–2191, 2017. © 2015 Society of Plastics Engineers     

Prediction of the fate of detergent chemicals during sewage treatment

Consideration of a conventional growth model for the activated sludge sewage treatment process has resulted in the development of an improved method for assessing the biodegradability of chemicals. The model indicates the importance of sludge retention time (SRT) and temperature on the treatment efficiency and suggests a need to control and examine the effect of both parameters on the biodegradation of materials. The effect of SRT and temperature is illustrated by data for the nutrification of ammonia and the biodegradation of alcohol- and alkylphenol-ethoxylates, LAS and nitrilotriacetic acid. The results illustrate the predictive power of the technique in obtaining results in the laboratory which are consistent with data reported from studies involving full scale treatment plants.     

Fish bioassays of linear alkylate sulfonates (LAS) and intermediate biodegradation products

Linear alkylate sulfonates (LAS) are relatively toxic to fish when tested under static conditions by standard bioassay techniques, the median tolerance limit (TL_m) being around 3 mg/liter and 0.6 mg/liter for the C₁₂ and C₁₄ homologs, respectively. However, these materials are so readily degraded by bacterial attack that bluegill fingerlings live with no trouble in effluents from laboratory continuous flow activated sludge units being fed 100 mg/liter or more of either product. No effects on the fish were noticeable in exposures of 96 hr or more, except for slight alterations in the microscopic appearance of the gill tissue. Thus, the removal of the LAS by biodegradation is paralleled by the removal of toxicity and there is no indication that toxic intermediates accumulate during the biodegradation process. This conclusion is substantiated by the observation of a much lower degree of toxicity (TL_m 75 mg/liter) for sulfophenylundecanoic acid disodium salt (mixed isomers), synthesized as a model of an intermediate degradation product. Characterization, gas chromatography and methylene blue analysis of this product are also discussed.     

Chain extension and mechanical properties of unsaturated aliphatic copolyesters based on poly(L‐lactic acid)

Chain extension of poly(L ‐lactic acid) (PLLA) with unsaturated groups (PLBM) was attempted using benzoyl peroxide (BPO) and the resulting variation in molecular weight and mechanical properties was explored. Bulk copolymerization of L ‐lactic acid (LA)/1,4‐butanediol (BD)/maleic acid (MA) (100/1/1) isomerized some of the cis‐structured maleate units into trans‐structured fumarate units. The optically active LA promoted isomerization during the condensation polymerization. Chain extension of PLBM with BPO did not bring about a discernible increase in the molecular weight when the chain extension was carried out in various solvents with different radical abstraction abilities. In contrast, the hot pressing of PLBM containing BPO increased the molecular weight and sometimes produced chloroform‐insoluble gels depending on the BPO concentration and temperature. The chain extension at low temperatures increased the flexibility of PLBM considerably. However, PLBM lost the flexibility precipitously as the chain‐extension temperature increased above 120°C. The biodegradation rate of PLBM was much slower than that of PLLA. The biodegradation rate was further lowered by the chain extension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1802–1807, 2003     

Low temperature fracture behaviour and AE characteristics of autoclaved aerated concrete(AAC)

For a quantitative understanding of freezing damage on Autoclaved Aerated Concrete(AAC) and fiber reinforced AAC(i.e., RAAC), the influence of water and temperature (R.T. ∼ −20°C) on those materials have been studied by the investigation of AE characteristics, the fracture mechanics J-integral test and SEM observation. Furthermore, using the AE frequency analysis based on the frequency energy density distribution ratio (EDDR), the micro-fracture process for various test conditions has been interpreted.The AE activities and fracture toughness showed a large difference depending on the water content and temperature. All the AE events emitted during the fracture toughness tests could be classified into 6 groups. Also, the AE sources were considered paying particular attention to the micro-crack formation, the friction of inter-matrix and the fiber breaking behaviors at fracture. Noting that the AE is emitted during the drying process, the drying shrinkage damage was discussed.     

Acoustic emission studies of low thermal expansion aluminum-titanate ceramics strengthened by compounding mullite

Mullite (Mu) with high strength was compounded into aluminum-titanate (AT) ceramics with low thermal expansion to increase their strength. For the AT–Mu system composites, thermal contraction and expansion and acoustic emission (AE) event count rate were measured during cooling using the AE technique and the characteristics of AT–Mu composites were evaluated. The expansion due to microcracking in the range of AE count peak temperatures to room temperature was obtained and the crack volume was estimated from the expansion by cracking. A linear relation with a very high correlation (r = 0.993) was observed between bending strength and crack volume at room temperature. From the linear plot, the bending strength at crack-free temperature in the best AT–Mu composite was shown to be 130 MP.     

烷基苯磺酸钠／烷基二苯醚双磺酸盐复配体系的洗涤性能研究

主要考察了烷基苯磺酸钠（LAS）与十六烷基二苯醚双磺酸盐（D8390）复配体系在不同复配比、不同浓度、不同水硬度、不同温度条件下对不同种类污布的洗涤能力。结果表明：（1）对于碳黑、皮脂两种污布,单独D8390的洗涤能力不及LAs,LAS／D8390复配体系在w（LAS）：w（D8390）=8：2—7：3范围内洗涤能力最高;（2）对于蛋白污布,单独D8390的洗涤能力明显高于LAS,且在两者复配体系中,随着D8390含量的增加,洗涤能力先快速增大,在w（LAS）：W（D8390）=3：7时达到最高点,之后略降低。（3）在W（LAS）：W（D8390）=7：3的复配体系中,活性物总质量浓度在0．10％-0．20％范围内,质量浓度对碳黑、皮脂两种污布的洗涤能力影响不明显,但随着浓度的降低,对蛋白污布的洗涤能力明显降低;（4）采用LAS与D8390进行复配,可以明显改善体系在高硬度、低温下的洗涤能力。     

Using sonochemical reactor for degradation of LAS from effluent of wastewater treatment plant

Linear alkylbenzene sulfonates (LAS) are anionic surfactants, which are found in relatively high amounts in domestic and industrial wastewaters. The effectiveness of using sonochemical reactor for the degradation of LAS from effluent of wastewater treatment plant has been investigated. In this study, experiments of LAS solution were performed using methylene blue active substances (MBAS) method. The effectiveness of sonochemical reactor for LAS degradation is evaluated with emphasis on the effect of sonication time and initial LAS concentration. Experiments were carried out at initial concentrations of 0.2 mg/L, 0.5 mg/L, 0.8 mg/L and 1 mg/L, frequency of 130 kHz, acoustic power value of 400 W, temperature of 18-20 °C and pH value of 6.8-7. This study showed that LAS degradation was found to increase with increasing sonication time. In addition, as the concentration is increased, the LAS degradation rate decreases in the sonochemical reactor.     

Thermomechanical Mismatch in Ceramic-Fiber-Reinforced Glass-Ceramic Composites

The thermomechanical relationship between mullite and a lithium aluminosilicate (LAS) glass-ceramic has been studied by a technique of bimaterial dilatometry. The viscoelastic behavior of LAS was found to result in a temperature T rvsl below the glass-transformation temperature T_g at which the interfacial stresses between the materials undergo a reversal in sign. The effect of T rvsl on the high-temperature mechanical properties of mullite or SiC fiber-reinforced glass-ceramic composites is discussed. It is suggested that fiber clamping by the matrix at temperatures between T rvsl and T_g contributes to the brittle, high-temperature behavior of such composites.     

表面活性剂降解研究进展

简述了表面活性剂对环境的影响及其降解的发展概况，着重讨论了表面活性剂的各种生物降解的研究方法和特点，降解动力学，结构与降解性能间的关系，影响降解的环境因素及直链烷基苯磺酸盐（LAS），烷基硫酸盐（AS）等几类常见表面活性剂的生物降解机理。并对近年发展起来的表面活性剂光催化降解的研究方法，降解机理及降解动力学作了简要介绍。     

Spark Plasma Sintering of fine alpha-silicon nitride ceramics with LAS for spatial applications

Many space systems such as satellite mirrors and their supporting structures require to be made from very low-thermal expansion materials combining both high hydrostability and relatively high mechanical properties. In this study, we have applied the “composite concept” in order to explore the possibility of fabricating near zero thermal expansion silicon nitride based ceramics. Consequently, a negative thermal expansion material belonged to the lithium aluminosilicate family (LAS powder crystallized under de β-eucryptite structure) was introduced in an alpha-silicon nitride fine powder (5 and 20 vol% of LAS) and the resulting composite system was sintered by Spark Plasma Sintering (SPS) at 1400 and 1500 °C. In the case of 20 vol% LAS compositions, relatively well-densified ceramics (94.4% of the theoretical density) were produced without adding any further sintering additive. The addition of yttria and alumina oxides allowed enhancing the densification level up to 98.2% (20 vol% LAS compositions) or from 62.3% up to 96.7% of the theoretical density in 5 vol% LAS materials. Nevertheless, it was impossible to full consolidate silicon nitride/LAS composite ceramics at temperatures lower than the temperature at which β-eucryptite melts, even by using SPS technology. Moreover, because of the relatively low temperatures involved in SPS, the α to β-Si₃N₄ transformation was avoided, resulting in microstructures composed of fine equiaxed α-Si₃N₄ grains (<200 nm) and of a glassy phase. Even if the effect of having a very large negative thermal expansion material was lost during the sintering step (because of the β-eucryptite melting), ceramics containing only 20 vol% of LAS-based phase exhibited very interesting values as regards of mechanical properties (strength, hardness, toughness, and Young's modulus), thermal conductivity and thermal expansion coefficient. We discuss in this work why we are so interested in developing dense silicon nitride/LAS ceramics sintered without any further additive addition, even though β-eucryptite is melted during the process and the transformation to the β phase is avoided.     

木质素两性表面活性剂的合成及表面物化性能

以十二烷基二甲基叔胺、环氧氯丙烷为原料,合成了中间体(2,3-环氧丙基)十二烷基二甲基氯化铵(DMAC),再与磺化木质素(SL)酚羟基反应,合成了木质素两性表面活性剂LAS。通过正交实验确定了最佳合成条件:以丙酮为溶剂,n(SL)∶n(DMAC)=1∶1.1,反应时间3h,pH=12,反应温度55℃,产物中氮质量分数达2.25%。通过元素分析、傅立叶变换红外光谱、UV,确证了目的产物结构。测定产物的临界胶束质量浓度CMC为3g/L,γCMC为21.11mN/m,HLB值为10。表明所合成的木质素两性表面活性剂具有较高的表面活性。