芦苇硫酸盐浆的氯化反应(一)

本实验研究了芦苇硫酸盐浆在多段漂氯化段的化学反应中,氧化反应和取代反应的比率,和芦苇氯化木素的溶出特点。实验结果表明,氧化反应对于木素的降解溶出具有决定性的作用。但是,增加氧化反应应避免浆的平均聚合度的剧烈下降。 芦苇硫酸盐浆中木素在氯化时,表现出比硫酸盐木浆木素易氧化、易溶出的特点。芦苇氯化木素中羟基对木素的溶出,尤其是水溶出具有重要意义。 芦苇氯化浆中Klason木素和芦苇二氧六环氯化木素的红外光谱结果,和芦苇二氧六环氯化木素用凝胶色谱法测定的分子量和分子量分布的结果表明,随着耗氯量增加,氯化木素的氧化降解程度增大。当耗氯量较低时,氯与木素进行的氧化反应,以木素中各类醚键的氧化性断裂为主要形式;当耗氯量较高时,木素中苯环结构及其反应产物的氧化破坏居于主要地位。 由于芦苇氯化浆的热水处理脱有机结合氯和脱木素的效果较好,可以考虑用热水处理代替碱处理。     

采用厌氧-好氧生物处理制浆和造纸工厂废水

木材制浆和造纸工厂采用化学品蒸煮和漂白方法,以除去纤维原料中木素和其它有色化合物。由于使用氯基化学品漂白纸浆,产生的木素降解产物中包括各种氯化有机衍生物,这些含氯有机物具有毒性,并使废水处理发生困难。目前,木材制浆和造纸工厂通常采用化学凝聚沉淀法、氧化曝气塘、活性污泥以及厌氧处理方法处理漂白废水。德国DalamanSEKA制浆和造纸工厂,试验了漂白纸浆产生的氯化有机物对厌氧菌的毒害作用,应用上流式污泥返回床(厌氧)与活性污泥(好氧)处理废水。结果表明:在试验条件下,废水中氯化有机物对厌氧菌没有产生抑制作用。应用厌氧/…     

利用光催化剂、太阳照射对造纸工厂废水进行解毒

德国航空空间研究中心科技人员研究了利用光催化剂例如TiO2、太阳照射处理造纸工厂废水。对废水中有机氯化物进行解毒。在处理制浆和造纸工厂废水过程中，生物聚合物木素的降解是个难题，采用光催化剂TiO2和太阳照射方法处理含木素的造纸废水，对于分解废水中具有毒性的有机氯化物是有效和经济的。     

光催化氧化-生物降解直接耦合处理桉木化机浆废水的研究

本研究探讨了桉木化机浆厌氧废水催化脱毒-微生物协同增效和Fenton高级氧化处理性能,对光催化氧化-生物降解直接耦合法（ICPB）处理桉木化机浆厌氧废水效率、微生物菌落结构和机理进行了研究。结果表明,桉木化机浆废水的生化处理效果较差;ICPB法中光催化氧化和微生物降解具有良好的协同作用,可显著提高桉木化机浆废水好氧处理效果并降低深度处理过程中Fenton试剂用药量,好氧处理过程中废水COD_Cr去除率由46.7%提高至74.3%;ICPB体系中微生物的多样性和丰富度增加,降解芳香族化合物的优势菌种显著增加。     

超声-絮凝技术处理造纸废水的研究

各种工业废水中，造纸工业用水量大，排放的污染物多，对环境造成了极大的危害。目前，国内外造纸废水的治理技术大多以混凝沉淀和生物处理为主，此外还有超滤、电解、光催化氧化，化学还原、冷冻结晶、超声空化法等。但对于我国来说，后几种处理技术大多处于试验研究阶段，而生化法则具有对含有大量难降解的木素及有毒的氯化木素降解产物处理效率很低的缺点，受到限制。     

研究证实氧漂段优于生物处理车间

为了减少硫酸盐浆厂的污染,比较经济的方法是设置一氧漂阶段,而不是建立一个生物处理车间。就氯化木素而论,选择氧漂阶段使一个日产500吨的浆厂处理每吨氯化木质素减少费用115美元。选择生物处理车间要求厂方每年付出几乎200万美元,但完全没有减少任何氯化木质素。     

活性炭负载铈催化臭氧处理桉木制浆废水

通过浸渍法在活性炭(AC)上负载铈(Ce)制备了催化剂(Ce-AC),并用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和比表面积分析仪(BET)对制备的催化剂进行表征,研究了该催化剂催化臭氧处理桉木制浆废水对CODCr和色度的去除效果。结果表明,Ce以CeO_2晶型的形式负载在AC上;Ce负载量为1.0%时,Ce-AC催化臭氧处理桉木制浆废水效果最好;当反应30 min时,废水的色度和CODCr去除率达到95%和55%,分别比单独臭氧氧化过程提高10个和18个百分点,比AC催化臭氧氧化过程提高5个和12个百分点;Ce-AC催化臭氧处理桉木制浆废水极大地提高了对废水CODCr的去除率。动力学分析表明,单独臭氧氧化及AC、Ce-AC催化臭氧处理制浆废水的过程中,CODCr降解的反应符合表观二级动力学方程,负载的Ce提高了反应的动力学速率常数。     

乙醇溶解芦苇木素的氧化及对染料废水的吸附研究

制浆黑液中木素的回收再利用对资源的有效利用、环境保护有重要意义。本实验以芦苇为原料,首先提取乙醇制浆废液中的溶解木素,纯化后再经过双氧水氧化提高对亚甲基蓝染料废水的吸附效果。首先在单因素实验的基础上,确定氧化温度为70℃,以固液比、保温时间、双氧水浓度为变量,利用中心组合-响应面法,以氧化得率和木素对亚甲基蓝的吸附量为参考依据,得到双氧水氧化木素吸附染料废水的最佳条件为保温时间120min,双氧水浓度20%,固液比1:20,最佳条件下木素对亚甲基蓝的吸附量为42.68mg/g,而未氧化的木素吸附量仅为18 mg/g。其次,绘制氧化后木素对染料废水的吸附曲线,发现该吸附曲线符合朗格缪尔吸附等温曲线,通过吸附曲线得到最佳条件下氧化木素对亚甲基蓝的最大吸附量为142.86mg/g,大于文献参考值,该木素可大规模应用于染料废水的处理。     

纸浆漂白过程污染的控制

现代漂白技术是用不同药剂分别在一系列的工序(或称段)中逐步完成的,使用的主要药剂多为含氯化合物(如液氯、次氯酸盐、二氧化氯等)。因此在化学浆的漂白过程中排水总是含有大量的有机氯化物,主要为氯化邻苯二酚,氯化愈创木酚和氯化香草醛。这些氯化物可能是二氯化物,也可能是三氯或四氯化物。漂白过程中木素的氯化氧化降解是产生氯代酚类化合物的主要原因。这种有机氯化物比未氯化的有机物更不易被生物所降解,而且易于在生物体中积累而达到有害程度。本文仅就CEH三段漂白来谈点污染控制方法。     

电芬顿氧化法处理染料废水的研究进展

文章综述了电芬顿法处理印染废水的基本原理,分析了电极材料、不同类型芬顿反应器对染料废水脱色率的影响,电芬顿法作为一类高级氧化技术,是处理染料废水的有效方法。双氧水(H2O2)是在包含支持电解质的酸性溶液中通过电化学法还原溶解氧制备的,这个氧化过程产生的羟基自由基(·OH)可以与废水中的有机污染物反应产生二氧化碳和水。另外,对阴极材料的优化不仅可以提高(·OH)/(或H2O2)的产率,而且可以节约染料废水的处理成本。因此,通过选择性研究,电芬顿法处理染料废水是经济可行的。     

Electrochemical oxidation of hydroquinone, resorcinol, and catechol on boron-doped diamond anodes

The electrochemical oxidation of aqueous wastes polluted with hydroquinone, resorcinol, or catechol on boron-doped diamond electrodes has been studied. The complete mineralization of the organic waste has been obtained independently of the nature of each isomer. No aromatic intermediates were found during the treatment, and solely aliphatic intermediates (carboxylic acids C4 and C2, mainly) were detected in the three cases. Although as from the bulk electrolyses study no differences in the electrochemical oxidation of dihydroxybenzenes seem to exist, different voltammetric behavior between resorcinol and the other two isomers was obtained in the voltammetric study. Catechol and hydroquinone have a reversible quinonic form, and a cathodic reduction peak appears in their voltammograms. The characterization of the first steps in the electrochemical oxidation of the three dihydroxybenzenes showed the formation of a larger number of intermediates in the oxidation of catechol, although no carbon dioxide was detected in its oxidation. Conversely, the oxidation of resorcinol and hydroquinone lead to the formation of important concentrations of carbon dioxide. The nondetection of aromatic intermediates, even if small quantities of charge are passed, confirms that the oxidation must be carried out directly on the electrode surface or by hydroxyl radicals generated by decomposition of water.     

A comparative study of hard and softwood lignins alterations during treatment in dioxane-water-HCl agent

The objective of the presented contribution was a study of the lignin alterations occurring in the process of the acidolytic delignification of chosen representatives of soft and hard wood species (maple and spruce) in dioxane-water-HCl mixture. All lignin samples were characterised by yield or recovery, molecular weights, as well as by GLC data of corresponding nitrobenzene oxidation products. In order to obtain more information about condensation and degradative reactions of lignin under conditions of acidolytic treatment a simulation of the process of lignin isolation was performed, too. Samples of dioxane lignins obtained after 90 min. of isolation at 82.5 and 98 °C were therefore recooked during 360 min. under identical conditions as applied in the lignin isolations. Concentrations of lignin in the reaction mixture were 1 and 10% thus approximately corresponding the lignin concentration inside and outside of the wood meal during the lignin isolation. The obtained experimental data point out the course of both degradative and condensation reactions. Maple wood lignin undergo deeper degradation than those of spruce under the same reaction conditions. The decreased yields of lignin oxidation products with the time of acidolytic treatment and after recooking hint at the formation of new linkages among building units of lignin thus modifying its macromolecules. The intensity of occurring alterations of examined lignins is not only dependent of time and temperature, but also of the concentration of lignin.     

Electrochemical inactivation of triclosan with boron doped diamond film electrodes

This research investigated an electrochemical method for inactivating contaminated stockpiles of the biocidal agent, triclosan. The goal of the electrolysis was to produce products that were amenable to treatment in conventional activated sludge treatment systems. Triclosan oxidation in electrochemical cells with boron doped diamond (BDD) film anodes was investigated in aqueous solutions at a pH value of 12. Chronoamperometry experiments showed that direct oxidation of triclosan occurred at potentials below those for H2O, Cl-, or OH- oxidation. Measurable rates of triclosan oxidation began at potentials above 0.4 V with respect to the standard hydrogen electrode (SHE), while potentials of 0.5, 1.3, and 1.8 V were required to obtain measurable oxidation rates of H2O, Cl-, and OH-, respectively. At anode potentials below 2 V, the dominant electrode reaction involved direct triclosan oxidation, while indirect oxidation was the dominant pathway at higher potentials. However, cyclic voltammetry experiments showed that direct oxidation of triclosan resulted in the formation of a passivating film on the electrode that could only be removed by oxidation at potentials above 3 V. Direct triclosan oxidation showed a very weak potential dependence, suggesting that its oxidation was limited by chemical dependent factors rather than by an outer-sphere electron transfer reaction. Organic triclosan oxidation products consisted primarily of chlorinated acetic acids and chlorinated phenolic compounds. Although the byproducts of triclosan oxidation became increasingly less reactive with increasing electrolysis time, triclosan could be completely oxidized to CO2 at current densities above 2 mA/cm2. Microtox testing indicated that residual triclosan accounted for nearly all the toxicity in the treated water, despite the fact that chlorinated byproduct concentrations were significantly higher than those of triclosan itself.     

Electrochemical oxidation as a final treatment of synthetic tannery wastewater

Vegetable tannery wastewaters contain high concentrations of organics and other chemicals that inhibit the activity of microorganisms during biological oxidations, so biorefractory organics that are not removed by biological treatment must be eliminated by a tertiary or advanced wastewater treatment. In this paper, the applicability of electrochemical oxidation as a tertiary treatment of a vegetable tannery wastewater was investigated by performing galvanostatic electrolysis using lead dioxide (Ti/PbO2) and mixed titanium and ruthenium oxide (Ti/TiRuO2) as anodes under different experimental conditions. The experimental results showed that both the electrodes performed complete mineralization of the wastewater. In particular, the oxidation took place on the PbO2 anode by direct electron transfer and indirect oxidation mediated by active chlorine, while it occurred on the Ti/TiRuO2 anode only by indirect oxidation. Furthermore, the Ti/PbO2 gave a somewhat higher oxidation rate than that observed for the Ti/TiRuO2 anode. Although the Ti/TiRuO2 required almost the same energy consumption for complete COD removal, it was more stable and did not release toxic ions, so it was the best candidate for industrial applications. With the Ti/TiRuO2 anode, the rate of tannery wastewater oxidation increased with the current density, pH, and temperature of the solution. These results strongly indicate that electrochemical methods can be applied effectively as a final treatment of vegetable tannery wastewater allowing the complete removal of COD, tannin, and ammonium and decolorization.     

Changes on Content,Structure and Surface Distribution of Lignin in Jute Fibers After Laccase Treatment

Effect of laccase treatment on the content, structure, and surface distribution of lignin in jute fibers were fundamentally investigated. Four percent lignin was removed from jute fibers via the laccase treatment. The residual lignin in the laccase-treated jute fibers showed increased molecular weights, which indicated polymerization between lignins on jute fibers. Meanwhile, the phenolic hydroxyl content in lignin decreased during the laccase oxidation accompanied by demethylation of methoxyl groups and generation of carbonyl groups. Due to the degradation and subsequent polymerization of lignin by laccase, the bulgy lignins on jute fiber surfaces were redistributed, which made the surface neat and glossy.     

A comparison of different chemical sanitizers for inactivating Escherichia coli O157:H7 and Listeria monocytogenes in solution and on apples, lettuce, strawberries, and cantaloupe

Ozone (3 ppm), chlorine dioxide (3 and 5 ppm), chlorinated trisodium phosphate (100- and 200-ppm chlorine), and peroxyacetic acid (80 ppm) were assessed for reduction of Escherichia coli O157:H7 and Listeria monocytogenes in an aqueous model system and on inoculated produce. Initially, sanitizer solutions were inoculated to contain approximately 10(6) CFU/ml of either pathogen, after which aliquots were removed at 15-s intervals over a period of 5 min and approximately plated to determine log reduction times. Produce was dip inoculated to contain approximately 10(6) E. coli O157:H7 or L. monocytogenes CFU/g, held overnight, submerged in each sanitizer solution for up to 5 min, and then examined for survivors. In the model system study, both pathogens decreased > 5 log following 2 to 5 min of exposure, with ozone being most effective (15 s), followed by chlorine dioxide (19 to 21 s), chlorinated trisodium phosphate (25 to 27 s), and peroxyacetic acid (70 to 75 s). On produce, ozone and chlorine dioxide (5 ppm) were most effective, reducing populations approximately 5.6 log, with chlorine dioxide (3 ppm) and chlorinated trisodium phosphate (200 ppm chlorine) resulting in maximum reductions of approximately 4.9 log. Peroxyacetic acid was the least effective sanitizer (approximately 4.4-log reductions). After treatment, produce samples were stored at 4 degrees C for 9 days and quantitatively examined for E. coli O157:H7, L. monocytogenes, mesophilic aerobic bacteria, yeasts, and molds. Populations of both pathogens remained relatively unchanged, whereas numbers of mesophilic bacteria increased 2 to 3 log during storage. Final mold and yeast populations were significantly higher than initial counts for chlorine dioxide- and ozone-treated produce. Using the nonextended triangle test, whole apples exposed to chlorinated trisodium phosphate (200 ppm chlorine) and shredded lettuce exposed to peroxyacetic acid were statistically different from the other treated samples.     

漆酶/介体处理纸浆的反应性能及动力学研究

采用溶解氧分析仪对漆酶和漆酶/介体处理未漂KP浆过程中的氧气质量浓度进行测定,研究了不同条件下漆酶/介体处理纸浆的反应性能,通过对实际动力学曲线的拟合,建立了漆酶/介体体系催化氧化反应的动力学模型。结果表明:不同的介体中,丁香酸甲酯(MS)协同漆酶处理纸浆表现出较活跃的反应性能。漆酶单独处理MS(无纸浆)也消耗一定的氧气。单加漆酶处理纸浆时,初始几分钟内反应速率较快,之后体系中氧气质量浓度基本不变。漆酶/MS处理未漂KP浆时,在30 min内即可消耗完密闭反应体系中的氧气。漆酶/MS对纸浆中木素的催化氧化反应符合一级指数幂函数动力学特征。     

高氧气调包装肉类研究进展

肉类高氧气调包装通常是用含有70%~80%的氧和20%~30%的二氧化碳的混合气体对新鲜肉类进行包装的技术,其中的氧气可使肉类呈现稳定的红色,二氧化碳主要是抑制细菌的生长而延长贮藏期限。本文对近年来该技术在新鲜肉类中应用的研究情况进行了总结,从高氧包装对肉类颜色的影响、高氧环境下的微生物生长、高氧对肉类的脂类氧化和蛋白质氧化的影响以及提高高氧气调包装肉类品质的措施等方面进行了评述。肉类的颜色稳定性与肌肉类型有关,随O2浓度的增加而增大,随CO2浓度的增加而降低。另外,肉类颜色稳定性受肉类氧化特别是脂类氧化的影响。高氧气调包装肉类中的微生物受到CO2的抑制作用表现出比生长速率降低及生长的迟滞期延长。高氧气调包装会引起脂类和肌红蛋白的氧化以及蛋白质的交联,导致肉的嫩度和多汁性下降。高氧气调包装会导致肉类煮制时出现过早熟褐现象。添加某些防腐剂和抗氧化剂可以有效改善高氧气调包装肉类质量,延长肉类贮藏期限。     

Carbon isotope fractionation during permanganate oxidation of chlorinated ethylenes (cDCE,TCE, PCE)

Permanganate oxidation of chlorinated ethylenes is an attractive technique to effect remediation of these important groundwater contaminants. Stable carbon isotope fractionation associated with permanganate oxidation of trichloroethylene (TCE), tetrachloroethylene (PCE), and cis-1,2-dichloroethylene (cDCE) has been measured, to study the possibility of applying stable carbon isotope analysis as a technique to assess the efficacy of remediation implemented by permanganate oxidation. Average carbon isotope fractionation factors of alphaTCE = 0.9786, alphaPCE = 0.9830, and alphacDCE = 0.9789 were obtained, although the fractionation factor for PCE may be interpreted to change from a value of 0.9779-0.9871 during the course of the reaction. The fractionation factors for all three compounds are quite similar, in contrast to the variation of fractionation factors vs degree of chlorination observed for other degradative processes, such as microbial dechlorination. This may be due to a common rate-determining step for permanganate oxidation of all three compounds studied. The large fractionation factors and the relative lack of dependence of the fractionation factors upon other environmental factors (e.g. oxidation rate, presence of multiple contaminants, incomplete oxidation, presence of chloride in solution) indicate that monitoring delta13C values of chlorinated ethylenes during oxidation with permanganate may be a sensitive, and potentially quantitative, technique to investigate the extent of degradation.     

Formation of Pb(III) intermediates in the electrochemically controlled Pb(II)/PbO₂ system

The formation of lead dioxide PbO(2), an important corrosion product in drinking water distribution systems with lead-bearing plumbing materials, has been hypothesized to involve Pb(III) intermediates, but their nature and formation mechanisms remain unexplored. This study employed the electrochemical (EC) method of rotating ring disk electrode (RRDE) and quantum chemical (QC) simulations to examine the generation of intermediates produced during the oxidation of Pb(II) to PbO(2). RRDE data demonstrate that PbO(2) deposition and reduction involves at least two intermediates. One of them is a soluble Pb(III) species that undergoes further transformations to yield immobilized PbO(2) nanoparticles. The formation of this intermediate in EC system is mediated by hydroxyl radicals (OH(?)), as was evidenced by the suppression of intermediates formation in the presence of the OH(?) scavenger para-chlorobenzoic acid. QC simulations confirmed that the oxidation of Pb(II) by OH(?) proceeds via Pb(III) species. These results show that Pb(III) intermediates play an important role in the reactions determining transitions between Pb(II) and Pb(IV) species and could impact lead release in drinking water.