Efficient reductive dechlorination of monochloroacetic acid by sulfite/UV process

Most halogenated organic compounds (HOCs) are toxic and persistent, and their efficient destruction is currently a challenge. Here, we proposed a sulfite/UV (253.7 nm) process to eliminate HOCs. Monochloroacetic acid (MCAA) was selected as the target compound and was degraded rapidly in the sulfite/UV process. The degradation kinetics were accelerated proportionally to the increased sulfite concentration, while the significant enhancement by increasing pH only occurred in a pH range of 6.0-8.7. The degradation proceeded via a reductive dechlorination mechanism induced by hydrated electron (e(aq)(-)), and complete dechlorination was readily achieved with almost all the chlorine atoms in MCAA released as chloride ions. Mass balance (C and Cl) studies showed that acetate, succinate, sulfoacetate, and chloride ions were the major products, and a degradation pathway was proposed. The dual roles of pH were not only to regulate the S(IV) species distribution but also to control the interconversion between e(aq)(-) and H(?). Effective quantum efficiency (Φ) for the formation of e(aq)(-) in the process was determined to be 0.116 ± 0.002 mol/einstein. The present study may provide a promising alternative for complete dehalogenation of most HOCs and reductive detoxification of numerous toxicants.     

Degradation of tert-butyl alcohol in dilute aqueous solution by an O3/UV process

This paper describes the degradation of tert-butyl alcohol (TBA) in dilute aqueous solution by an O3/UV process. The degradation process was investigated experimentally in a semi-batch reactor under various operational conditions, i.e., ozone gas (O3) dosage, UV light intensity, and water quality in terms of varying bicarbonate concentration. TBA was oxidized rapidly in the O3/UV system, and acetone, hydroxy-iso-butyraldehyde, and formaldehyde were identified as primary intermediates, whereas pyruvaldehyde and acetic, formic, pyruvic, and oxalic acids were generated as a result of further oxidation process. A good organic carbon balance was obtained, indicating that most reaction intermediates have been identified and quantified.     

紫外/过氧化氢法制备葡萄糖酸的研究

研究了紫外辐射下利用过氧化氢氧化葡萄糖转化为葡萄糖酸的工艺。结果表明:采用紫外灯照射葡萄糖溶液,并通空气和流加过氧化氢,可快速将葡萄糖转化成葡萄糖酸。研究发现,葡萄糖与过氧化氢摩尔比、反应温度、反应时间、葡萄糖溶液质量体积分数等影响葡萄糖酸产率。通过正交实验,得到最佳工艺条件为:葡萄糖与过氧化氢摩尔比1:3,反应温度50℃,反应时间6h,葡萄糖溶液质量体积分数0.25g/mL;在此反应条件下,葡萄糖酸产率为78.26%。     

纸浆漂白过程中草酸的形成、危害及控制

随着制浆造纸工业的不断发展以及人们环保意识的不断提高,传统的含氯漂白工艺开始逐渐被无元素氯漂白（ECF）、全无氯漂白（TCF）等绿色漂白工艺取代。但是在绿色漂白过程中产生的草酸一直困扰着企业科技人员。本文介绍了纸浆漂白过程中草酸的形成、来源,草酸结垢对漂白设备的危害,以及对草酸及其危害的有效控制。     

以三苯甲烷染料酸性品红作探针检测罐头肉中的痕量Hg

建立了检测肉罐头中有毒重金属元素Hg的酸性品红共振光散射法,研究了共振光散射的光谱特征、适宜反应条件、共存物质的影响及反应机理。在pH 6.56的Tris-盐酸缓冲介质中,溴代十六烷基吡啶增敏酸性品红并与Hg(Ⅱ)结合生成三元复合物,使体系的共振光散射(RLS)显著增强并产生新的RLS光谱,在最大共振散射峰附近,Hg(Ⅱ)的质量浓度在0.005~0.40 mg/L与体系的共振光散射增强强度的绝对值│ΔIRLS│呈线性关系,定量限为0.032 mg/kg。方法简便、灵敏,加标回收率为98.5%~102%,相对标准偏差RSD(n=5)为2.0%~2.5%。适于罐头类肉食中Hg的测定。     

印染废水的厌氧/好氧/混凝沉淀/臭氧处理

采用中试规模(3 m3/d)悬浮生物滤池A/O/混凝沉淀/O3组合工艺,对纱线印染企业二沉池出水进行深度处理,考察稳定运行条件下,COD、色度和铁离子的去除效果以及处理出水对产品质量的影响。试验结果表明:进水COD、色度、铁离子分别为127 mg/L,532倍和0.24 mg/L时,相应的出水指标为51 mg/L,4倍和0.055 mg/L。在不影响产品质量的条件下,回用率可达50%左右。     

Catalytic determination of traces of oxalic acid in vegetables and water samples using a novel optode

A new optode has been introduced for determination of oxalic acid. The optode sensing reagent is Victoria blue 4R which is immobilized on triacetylcellulose membrane. This reagent could be oxidized by dichromate in acidic media resulting in decoloration of the membrane. Oxalic acid has a strong catalytic effect on this reaction. The difference in absorbance of the immobilized form of Victoria blue 4R at 615 nm between uncatalyzed and catalyzed reactions (ΔA) is directly proportional to the concentration of oxalic acid. Oxalic acid can be determined in the concentration range of 2–180 μg ml⁻¹. The effect of different possible interfering species has been examined and was shown that the optode has a very good selectivity. The optode has been applied for the determination of oxalic acid in different real samples such as spinach, beet root, mushroom and river water with excellent recoveries.     

Inactivation of Escherichia coli in orange juice using ozone

This research investigated the efficacy of gaseous ozone for the inactivation of Escherichia coli ATCC 25922 and NCTC 12900 strains in orange juice. Orange juice inoculated with E. coli (10⁶ CFU mL^− 1) as a challenge microorganism was treated with ozone at 75–78 µg mL^− 1 for different time periods (0–18 min). The efficacy of ozone for inactivation of both strains of E. coli was evaluated as a function of different juice types: model orange juice, fresh unfiltered juice, juice without pulp, and juice filtered through 500 µm or 1 mm sieves. Fast inactivation rates for total reduction of E. coli were achieved in model orange juice (60 s) and in juice with low pulp content (6 min). However, in unfiltered juice inactivation was achieved after 15–18 min. This indicated that juice organic matter interferes with antibacterial activity of gaseous ozone. The effect of prior acid (pH 5.0) exposure of E. coli strains on the inactivation efficacy of ozone treatment was also investigated. There was a strain effect observed, where prior acid exposure resulted in higher inactivation times in some cases by comparison with the control cells. However, the overarching influence on inactivation efficacy of ozone was related to the pulp content. Generally, the applied gaseous ozone treatment of orange juice resulted in a population reduction of 5 log cycles.

Industrial relevance

To facilitate the preservation of unstable nutrients many juice processors have investigated alternatives to thermal pasteurisation, including un-pasteurised short shelf life juices with high retail value. This trend has continued within the European Union. However within the US recent regulations by the FDA have required processors to achieve a 5-log reduction in the numbers of the most resistant pathogens in their finished products. Pathogenic E. coli may survive in acid environments such as fruit juices for long periods. This study demonstrates that the use of ozone as a non-thermal technology is effective for inactivation of E. coli and acid exposed E. coli in orange juice. Information on the design of the ozone treatment for inactivation of E. coli which results into safe juice products is also among the main outputs of this work. Ozone auto-decomposition makes this technology safe for fruit juice processing.     

破乳-混凝-光催化化学氧化法处理废切削液新工艺

先硝酸破乳,再用聚合硫酸铁(PFS)和阳离子聚丙烯酰胺(PAM)复合处理废切削液,当pH为8.0,PFS和PAM的用量分别是1 800mg.L-1和8mg.L-1时混凝效果较好.混凝上清液用UV/H2O2/Fe2 系统氧化,当pH=3,分4次加入H2O2,紫外照射6.5h,结果令人满意.采用该工艺处理废切削液,其COD去除率为99.5%,脱色率100%,出水达到了国家《污水综合排放标准》(GB-8987-1996)一级标准.     

Improving fatty acid methyl ester production yield in a lipase-catalyzed process using waste frying oils as feedstock

The application of waste frying oil (WFO) mixed with rapeseed oil as a feedstock for the effective production of fatty acid methyl esters (FAME) in a lipase-catalyzed process was investigated. The response surface methodology (RSM) was used to optimize the interaction of four variables: the percentage of WFO in the mixed feedstock, the methanol-to-oil ratio, the dosage of Novozym 435 as a catalyst and the temperature. Furthermore, the addition of methanol to the reaction mixture in a second step after 8 h was shown to effectively diminish enzyme inhibition. Using this technique, the model predicted the optimal conditions that would reach 100% FAME, including a methanol-to-oil molar ratio of 3.8:1, 100% (wt) WFO, 15% (wt) Novozym 435 and incubation at 44.5 °C for 12 h with agitation at 200 rpm, and verification experiments confirmed the validity of the model. According to the model, the addition of WFO increased FAME production yield, which is largely due to its higher contents of monoacylglycerols, diacylglycerols and free fatty acids (in comparison to rapeseed oil), which are more available substrates for the enzymatic catalysis. Therefore, the replacement of rapeseed oil with WFO in Novozym 435-catalyzed processes could diminish biodiesel production costs since it is a less expensive feedstock that increases the production yield and could be a potential alternative for FAME production on an industrial scale.     

Decontamination of powdery and granular foods using Continuous Wave UV radiation in a dynamic process

The purpose of this study was to investigate the potential of Continuous Wave UV radiation, applied in a dynamic process, to reduce Enterobacteriaceae counts in powdery and granular foods. Several food matrices were inoculated with a test strain (Escherichia coli LMG 8063) and radiated for 1 h with UV (254 nm, 2.88 mW/cm²). The particles were constantly homogenized under the UV source. Depending on the food matrix, reductions of 0.7–4.8 log cycles were obtained. For meringue chunks, a storage period of 20 h after inoculation prior to UV treatment caused a smaller reduction of the test strain (2.7 log cycles) than when radiation was applied immediately after inoculation (4.8 log cycles). Different initial contamination levels were tested. Higher inoculation levels tended to yield lower reductions. The results demonstrate that Continuous Wave UV radiation can be applied for microbial decontamination of specific powdery and granular food products under continuous homogenization.     

Citric acid crystallization process in dense phase using vibrated bed

This study evaluated mass yield, in crystallization of citric acid on a vibrated bed, using a large seed population (dense phase). A stainless steel crystallizer, jacketed and trunk-conical shaped was used in the crystallization experiments. The shaking system consisted of two perforated disks coupled to a mobile axle, which was connected to an eccentric. A central composite design (CCD) was used considering three independent variables: supersaturation level, dimensionless vibration number, and crystallization time, while the seed population (100,000 U) and operation temperature (55 °C) were fixed. Optimization of the experimental data obtained in the CCD was done finding the condition of maximum yield, 164.7%, which was experimentally tested and resulted in yield of 187.7%. An experimental simulation of serial crystallizers was studied, obtaining 166.9% yield, which was effective for obtaining crystals of greater final dimension.     

甲酸/过氧甲酸脱木素及制浆工艺研究进展

甲酸法制浆作为一种具有巨大发展潜力的有机溶剂制浆方法,引起了研究人员的广泛关注。本文主要阐述了甲酸法制浆的特点、反应机理及几种典型甲酸法制浆工艺的研究进展,并对甲酸法制浆在生物质精炼平台的构建方面作了展望。     

Preparative purification of rebaudioside A from aqueous extracts using chromatography: a process idea

An innovative chromatographic process idea for preparative purification of rebaudioside A from aqueous extracts of Stevia rebaudiana Bertoni leaves is developed. The process can handle high concentrated aqueous extracts, needs less equipment and has a lower solvent consumption compared to the state-of-the-art purification process of rebaudioside A. The innovative process consists of a cascade of three preparative chromatographic columns. The first column separates steviol glycosides from the plant matrix using water as eluent in reversed phase mode. The fraction of steviol glycosides is then concentrated on a second column which works as a capture column with a more non-polar adsorbent. The last column separates rebaudioside A from steviol glycoside under normal phase conditions using a mixture of acetonitrile and water as eluent. With a total yield of 97.5?±?1.5?% and a purity of 97.1?±?1.5?% the process fulfills the legal requirements for the purity of rebaudioside A.     

Visual detection of melamine in raw milk using gold nanoparticles as colorimetric probe

We report the development of a simple and rapid colorimetric detection method for melamine in raw milk using gold nanoparticles as probe. This assay relies upon the distance-dependent optical properties of gold nanoparticles. In neutral media, melamine could rapidly induce the aggregation of gold nanoparticles, thereby resulting in red-to-blue (or purple) colour change. The concentration of melamine in raw milk can be determined by monitoring with the naked eye or a UV–vis spectrometer. The present limit of detection for melamine is 0.4 mg/L. The method is rather simple, and the whole process including sample pretreatment takes only 12 min at room temperature. The merits (such as simplicity, rapidity, low cost and visual colorimetry) make the proposed method specially useful for on-site screening melamine levels well below the current safety limit in raw milk.     

Preliminary investigation of the supply of chemical species to an aqueous solution using a hydrogen-oxygen flame

A new method of supplying radical species to aqueous solutions using a hydrogen-oxygen flame is investigated. When a hydrogen-oxygen flame is directed on the surface of an aqueous solution, hydroxyl radicals (*OH) produced in the flame are extracted into the aqueous phase. The presence of *OH in the aqueous solution was confirmed by electron paramagnetic resonance with spin trapping using 5,5-dimethyl-1-pyrroline-N-oxide. The extraction of *OH into the aqueous solution was monitored using a quantitative analysis of hydrogen peroxide (H2O2). The effects of the hydrogen and oxygen gas flow rates, hydrogen/oxygen ratio, and atmosphere on H2O2 formation were studied. When the hydrogen-oxygen flame blew on a phosphate buffer solution (pH 6.7) under an Ar atmosphere, the concentration of H2O2 increased with the blowing time of the flame and the flow rate of hydrogen gas. Under air, nitrate and nitrite ions were formed in the aqueous phase in addition to H2O2, and the H2O2 concentration was lower than that under argon. The application of this new method to an aqueous solution of Cu(II)-ethylenediaminetetraacetic acid (EDTA) caused a remarkable decrease in the concentration of Cu(II)-EDTA and total organic carbon.     

基于Weibull分布函数的杏鲍菇干燥过程模拟及理化性质分析

研究了不同温度(40,50,60℃)、不同切片厚度(4、7、10 mm)对杏鲍菇热泵干燥动力学、体积收缩率、复水动力学、干制品色泽和氨基酸含量的影响。结果表明,Weibull分布函数能很好模拟杏鲍菇的热泵干燥过程,尺度参数α随温度升高而减小,随切片厚度增加而增大,形状参数β均小于1。干燥初期,体积收缩率与水分含量的降低呈线性关系,水分含量降低到60%时,体积收缩至原体积的70%且变化不再明显。Page模型能很好模拟杏鲍菇的复水动力学。干燥温度50℃、切片厚度4、7 mm条件下的干制品色泽较好,较长的干燥时间和高温会使杏鲍菇色泽变差。低温条件下能够保留较高的氨基酸含量。研究结果可为热泵干燥技术在杏鲍菇干燥工业生产中的应用提供借鉴。     

酸性／活性染料同浆印花工艺研究

以230%活性金黄BPF、160%活性红BPF、150%活性深蓝BPF、100%酸性红B、100%酸性深兰5R、200%酸性橙67#、pH滑移剂Argashide VS、碳酸氢钠为原料,采用pH滑移和两段蒸化工艺进行酸性,活性染料同浆印花,通过正交实验研究了最佳工艺,并对同浆印花工艺和传统工艺印制产品的K/S值和色牢度进行了比较.结果表明,滑移剂2%、碳酸氢钠3%、初蒸温度65℃、次蒸温度95℃的工艺条件最有利于酸性和活性染料的发色.该工艺条件下印制产品的K/S值与传统印花相近,牢度基本不变.     

微波/化学法预处理羊毛的轧染工艺研究

采用微波与化学结合的方法对羊毛织物进行预处理, 同时采用派拉丁1∶1金属络合染料和兰纳素活性染料进行染色.就各种微波/化学法预处理提高羊毛染色效果的机理进行了探讨,研究了微波预处理时间和不同化学整理剂用量对羊毛织物白度、断裂强力和得色量K/S值的影响,对比分析了羊毛织物未经预处理和经微波/化学法预处理后染色的固着率、断裂强力和断裂伸长等数值,得出了各种微波/化学法预处理羊毛的最佳工艺.