纳米纤维素助剂对马铃薯淀粉氧化的影响

研究了纳米结晶纤维素（NCC）作为淀粉氧化助剂对马铃薯淀粉氧化的影响。通过测定氧化淀粉的羧基含量和黏度来表征NCC对淀粉氧化程度的影响,并通过分析淀粉氧化前后的红外光谱（FT-IR）、X射线衍射图谱（XRD）和扫描电镜（SEM）图片来表征NCC对氧化淀粉结构的影响。结果表明：次氯酸钠氧化马铃薯淀粉时,pH值9、温度45℃是氧化的最佳条件,添加一定量的NCC可以促进淀粉的氧化,同时淀粉的氧化程度随着有效氯用量的增加而升高。在此条件下,当NCC添加量为5%,有效氯用量为2.25%时,得到的氧化淀粉含羧基比相同条件下不添加NCC得到的提高了10.42%。     

Ozone and chlorine dioxide: Similar chemistry and measurement issues

The chemical reactions associated with ozone and chlorine dioxide can be complicated and involve numerous intermediates. When ozone is applied, the presence of reactive intermediate species (O₂ ^‐, O₃ ^‐, OH, HO₂, HO₂ ^‐, and H₂O₂) influence the extent of oxidation that takes place and determines the amount and types of by‐products formed. Similarly, when chlorine dioxide is applied the amount of intermediate (Cl₂O₂) formed determines whether chlorine dioxide producing reactions or chlorate ion forming reactions occur. Ozone and chlorine dioxide are excellent agents for inactivating Cryptosporidium and Giardia. Microbiologically, each of the agents are very reactive. In the case of ozone, typically each molecule undergoes a one‐electron change. The mechanism of chlorine dioxide inactivation involves a recycling process whereby chlorine dioxide is reduced to chlorite ion followed by the “regeneration” of chlorine dioxide that continues to react within the cell over and over again. Chlorite ion also has oxidizing power and in some cases, is a biocide. When ozone and chlorine dioxide are used in combination, it is important that the chlorine dioxide application follow the ozone treatment to prevent the formation of unwanted by‐products such as ClO₃ ^‐.     

Structure and formation of cellulosic chars

The formation and structure of chars produced on heating of cellulose, lignin, and wood have been investigated by FTIR and CP/MAS ¹³C-NMR, and the results have been discussed in conjunction with parallel permanganate oxidation studies reported before. These data show that when cellulose is heated for 5 min within the temperature range of 325–350°C, the IR bands associated with hydroxyl and glycosidic groups in cellulose disappear, and new bands signal the formation of unsaturation and carbonyl groups by dehydration and rearrangement. The NMR data also show the disappearance of the glycosyl carbons at 60–110 ppm and the appearance of methyl and other paraffinic carbons at 0–60 ppm, aromatic carbons at 110–170 ppm, carboxyl carbons at 170–190 ppm, and carbonyl carbons at 190–220 ppm. On heating at 400°C the IR and NMR signals for the glycosyl groups completely disappear, the signals for carbonyl and carboxyl groups diminish, and those for the aromatic and paraffinic groups expand. At this stage the char contains about 69% aromatic and 27% paraffinic carbons. At the temperature range of 400–500°C the paraffinic carbon content is reduced to 12%, and a highly aromatic (88%) char is produced. This is consistent with the permanganate oxidation studies which show the production of polycyclic aromatic structures resulting from extensive condensation and crosslinking at these temperatures. The chars produced from wood and lignin at 400°C had about the same aromatic carbon content as the corresponding cellulose char; however, the char yields were higher due to the presence of the methoxy phenyl groups that survive the heating process, as indicated by strong NMR signals at 55 and 148 ppm.     

Water Disinfection: A Relationship Between Ozone and Aldehyde Production

In the water potabilization plant of Turin city (Italy), the oxidation process is carried out with ozone. Due to its well-known insufficient performance, it is necessary to add alternative oxidants (hypochlorite ion and chlorine dioxide). In this paper, we discuss the formation of linear carbonyl groups during surface water treatment in Turin.

The results obtained in the field confirm the synthesis of some aliphatic carbonyl compounds of low molecular weight. This phenomenon happens preeminently during the ozone disinfection process and, secondarily, during the other disinfection processes.

Experimental results show that, in this last event, chlorine reacts with organic substances, and in a second moment, after organics consumption, if chlorine is still in a sufficient concentration, oxidizing them.     

NaOH/硫脲/尿素预处理对棉纤维TEMPO选择性氧化的影响

采用NaOH/硫脲/尿素体系对棉纤维进行预处理,再进行选择性氧化,可以有效提高氧化棉纤维的羧基生成量。对比研究预处理棉纤维与普通棉纤维经2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)选择性氧化后的羧基含量、纤维形态以及黏度。结果表明,经NaOH/硫脲/尿素体系预处理能够加快氧化反应速率,增加羧基生成量,但对纤维有一定的损伤。其中,羧基生成量随着纤维质量分数的增加呈先增加后减少的趋势,当纤维素质量分数为6%时,羧基生成量最大,棉纤维的可及度和反应性提高。纤维形态分析表明,经NaOH/硫脲/尿素体系预处理的棉纤维润胀溶解程度要大于未预处理的氧化棉纤维;在TEMPO的氧化条件下,氧化棉纤维的相对黏度随着纤维素质量分数增加而增加;当纤维素质量分数较高时,氧化过程中氧化棉纤维的羧基生成量和降解程度都近似于原纤维。     

Heterogeneous Catalytic Ozonation with Supported Titanium Dioxide in Model and Natural Waters

This paper presents the results obtained with heterogeneous catalytic ozonation in which model and natural waters are ozonated in the presence of supported titanium dioxide (TiC₂) as a solid catalyst. The conditions in preparing the supported catalyst are experimentally optimized. The efficiencies of three catalyst supports (attapulgyte, alumina and silica gel) for organic matter oxidation have been compared. The TiC₂ supported in alumina calcined at 500[ddot]C compacted to granular form with a particle diameter about 2-4 mm is demonstrated to be the best catalyst on the removal total organic carbon (TOC) by ozone.     

Prostaglandins and prostaglandin intermediates. XV. Synthesis of 4-Oxo Carboxylic Acids and γ-Lactones by oxidative cleavage of homoallyl and homopropargyl ketones or alcohols

A convenient method to convert homoallyl or homopropargyl ketones or alcohols into 4-oxo carboxylic acids or γ-lactones is the oxidative cleavage of the multiple bond with potassium permanganate in diluted sulfuric acid. This is exemplified by the preparation of intermediates for the synthesis of 8-methylprostaglandin C₂. The oxidation of the allylic compounds with permanganate is compared with the oxidative cleavage by ozone/hydrogen peroxide, ozone/chromic acid or sodium periodate/potassium permanganate.     

Ceric ion-induced redox polymerization of acrylonitrile on cellulose

The ceric ion-cellulose redox system has been studied for grafting acrylonitrile on cotton fibers. Grafting yields are very high as compared to the persulfate-thiosulfate redox system reported earlier. Traces of copper sulfate in the reaction mixture do not increase grafting yields, unlike the persulfate-thiosulfate system. The high polymerization rate on cotton fibers is shown to be due to the reducing action of cellulose and not to the large surface area of cotton fibers. The Ce⁺⁴ consumption during grafting is higher than during oxidation of cellulose, indicating formation of homopolymer during the grafting reaction. Studies on the consumption of Ce⁺⁴ by model compounds such as D-glucose and α-methyl-D -glucoside show that the hemiacetal group in D -glucose is responsible for a faster rate of Ce⁺⁴ consumption. Formation of a Ce⁺⁴-alcohol complex also contributes to the initial fast rate of Ce⁺⁴ consumption. Studies on the oxidation of cellulose by Ce⁺⁴ indicate that the initial oxidative attack occurs on carbon atom 2, with the formation of a >C?O group. On further oxidation, cleavage of the C₂-C₃ bond occurs as shown by the presence of glycol aldehyde determined chromatographically. Cellulose-polyacrylonitrile grafts have been isolated by an acetolysis treatment followed by extraction with dimethylformamide. Number-average molecular weights of the isolated fractions are approximately 50,000–55,000. A theoretical method to calculate the number-average molecular weights, based on the PAN and the COOH contents of the grafted cellulose, is described.     

Determination of Residual Ozone or Chlorine Dioxide in Water with ACVK – an Updated Version

The determination of residual ozone or residual chlorine dioxide can be carried out with Acid Chrome Violet K (C.I. code no. 61710, formerly 6170), now available as dye for analytical use under the name of Alizarin Violet 3R (Aldrich 22, 783-8; MW 622.25). The discoloration of the dye in an NH₃-NH₄CI buffered solution of pH 8.1 to 8.5 is specific both for ozone and for chlorine dioxide without interference of chlorine, chloramines, chlorite or chlorate ions in concentrations possibly encountered in treated drinking water.

Detection limit : 0.02 mg L^?l: standard deviation : 0.01 mg L^?l are obtained both for ozone and chlorine dioxide.     

Thermal oxidation of synthetic triglycerides. II. Analysis of the volatile condensable and noncondensable phases

Tripalmitin, 1-lauryl dipalmitin, 2-lauryl dipalmitin, 1-oleyl dipalmitin and 2-oleyl dipalmitin were subjected to thermal oxidation at 200 C in the presence of air. The volatile consensable products of oxidation collected after 3 and 24 hours were analyzed for carbonyl and carboxyl compounds. The volatile non-condensable products were quantitatively examined for carbon monoxide, carbon dioxide, and hydrogen. The results indicated that long chain carbonyls were formed in the initial stages of oxidation. When the oxidation was allowed to proceed for 24 hours, saturated aldehydes from C₁ to C₁₆, methyl ketones, and other ketones were found in the volatile oxidation products. A variety of fatty acids from C₄ to C₁₆ were identified in the volatile fatty acids. The presence of dicarboxylic acids indicated that oxygen attacked the double bond of oleic acid in 1-oleyl dipalmitin. Possible mechanisms for the formation of the decomposition products were discussed. Portion of a thesis presented by Joseph G. Endres as partial fulfillment of the requirements for the degree of Doctor of Philosophy in Food Technology. Funds for the partial support of these studies were made available by the National Institute of health Grant A-1671.     

Development of Phenolic Lignin During ClO2 Bleaching of Kraft Pulp

The development of the phenolic lignin content in kraft pulp during ClO₂ bleaching was quantitatively determined by the periodate oxidation method. The effect of hypochlorous acid, an intermediate formed during chlorine dioxide bleaching, was eliminated by addition of sulfamic acid, a scavenger of hypochlorous acid. It was found that the number of free phenolic lignin groups per 100 lignin monomer units decreased from about 29 for unbleached kraft lignin to about 6.5 after 1 minute of ClO₂ bleaching. It was also shown that the in-situ generated hypochlorous acid created phenolic hydroxyl groups during chlorine dioxide bleaching. Since it was found that delignification by chlorine dioxide itself was mostly restricted to free phenolic lignin, these findings were used to explain the effect on delignification of addition order of chlorine and chlorine dioxide during bleaching of kraft pulp.     

Oxidative Hydrolysis of Cellobiose to Glucose

Abstract  

Cellobiose hydrolysis into glucose was chosen as a model system for cellulose breakdown to investigate glycosidic bond cleavage. The hydrolysis was enhanced by increased acidity in an inert gas medium, while air-assisted hydrolysis with a neutral solution achieved over 70% glucose yield. Hydrogen peroxide, as a stronger oxidant than air, converted cellobiose to carboxyl compounds, which lowered the glucose selectivity. At 150 °C, the selectivity from cellobiose to glucose was very low on porous γ-Al₂O₃ supported catalysts, even lower than without a catalyst. When the active metals were prepared on non-porous supports such as spherical alumina (α phase), the overall yield of glucose was dramatically improved at 120 °C. Similar improvements were obtained for another disaccharide model, sucrose, which achieved greater than 90% sucrose conversion with selectivity in excess of 90% at 80 °C.     

Enhanced sulfate formation on ozone-exposed soot

Gas phase experiments were conducted to examine the heterogeneous oxidation of sulfur dioxide on methane soot in the presence of ozone and water vapor. The enhanced formation of sulfate at atmospheric pressure was confirmed by the use of a particle-into-liquid sampler (PILS) coupled with ion chromatography (IC). Due to the ozone oxidation, multilayer adsorption of sulfur dioxide on soot, as well as sulfate formation and physisorption on secondary surface layer sites was observed. The ozone exposure also caused the soot to become hydrophilic, due to the formation of sulfuric acid and also likely the formation of carboxyl groups on the surface. For the soot and sulfur dioxide concentrations used, the sulfate yield increased with ozone levels, but no increase was observed at ozone concentrations above 2600 ppm.     

The Mortality of Nematodes in Drinking Water in the Presence of Ozone,Chlorine Dioxide,and Chlorine

ABSTRACT

Nematodes are among the organisms most commonly found in treated water. Although they are believed to be harmless, colonization of nematodes by pathogenic bacteria may transform them into harmful contaminants of the drinking water. Thus, efficient disinfectants must be applied to inactivate and remove nematodes. In the present study, nematode inactivation using different concentrations of ozone, chlorine dioxide, and chlorine for different exposure times are described. Three different disinfection models were tested. Based on experimental data, the best statistically significant relationship between mortality of nematodes in probits (Y), concentrations of disinfectants mg/L (C), and the exposure times in minutes (t) was established as Y = a*log(C) + b*log(t) + c. The estimated values of regression coefficients a, b, and c were 6.89, 0.76, and 1.13 for ozone, 0.66, 1.23, and 5.28 for chlorine dioxide and 1.59, 0.92, and 3.06 for chlorine, respectively. Comparison of the predicted LC(90) molar concentrations of the investigated disinfectants, chlorine dioxide, ClO₂, was found to be the most effective disinfectant, followed by ozone, O₃, while chlorine, Cl₂, was the least efficient disinfectant for inactivation of nematodes.     

Sequential disinfection of cryptosporidium parvum by ozone and chlorine dioxide

A two step disinfection approach was evaluated for control of Cryptosporidium parvum using bench‐scale experiments in 0.05 M phosphate buffer at pH 8 and 22 °C. Sequential application of ozone and chlorine dioxide was evaluated where ozone was applied first followed by chlorine dioxide. Infectivity in neonatal CD‐1 mice was used to assess oocyst viability after disinfection. The sequential treatment of oocysts by ozone followed by chlorine dioxide resulted in additional inactivation of C. parvum due to the synergism of the two disinfectants. The inactivation kinetics for chlorine dioxide were modeled following preconditioning with ozone at a given level using the Integral‐Hom model which takes the disinfectant decay into account. These preliminary findings indicate that sequential disinfection with ozone followed by chlorine dioxide may have potential in controlling waterborne parasites.     

Degradation Measurements of Linen Fabrics

Abstract

Different artificial aging techniques, e.g., thermal, chemical, and photodegradation were applied to raw linen fabrics to produce artificial model samples that mimic the archeological ones for in conservation and consolidation experiments of ancient textile fabrics. The artificially aged samples were evaluated via several instrumental methods, i.e., mechanically, spectrophotometrically, x-ray diffraction, and viscosity measurements. The results indicated that degradation reactions including oxidation, took place at glycosidic bonds as well as at hydroxyl groups of cellulose to cause scission of the molecular chains where molecular weight decreases. These aging techniques are responsible for the changes in whiteness (W_I ) and yellowness (Y_I ) indices and also of color differences (ΔE ).     

The Increasing Importance of the Use of Ozone in the Microelectronics Industry

Recently the microelectronics industry is investigating the application of ozonated solutions in the cleaning of semiconductor devices as an alternative for the frequently used H₂SO₄-mixtures. The use of ozone would result in more environmentally friendly and cost-saving cleaning concepts. To optimize this new wet chemical cleaning processes, fundamental understanding of the behavior of ozone in ultrapure water is required. The decomposition and the solubility of ozone in ultrapure water were investigated as a function of pH, temperature and various additives. Some applications will also be discussed, namely the oxidation of silicon and the mechanistic aspects of the removal of organic contamination.     

Determination of dissociable groups in natural and regenerated cellulose fibers by different titration methods

Different titration methods were applied with the purpose to determine the dissociation properties of a natural (cotton) and regenerated (viscose, modal and lyocell) cellulose fibers. Potentiometric and conductometric titration were used to determine the content of acidic groups. pK values were determined by potentiometric titration. Polyelectrolyte adsorption was used for surface and total charge determination, and to obtain information about charge location and accessibility of charged groups. It was found that the average content of acidic groups is higher in cotton fibers than in regenerated fibers. The fiber charge of cotton is due to the dissociation of two type of acidic groups, one with pK ≈3.5 and the other with pK ≈5.5. In regenerated fibers there is only one type of acidic groups (pK ≈3.5). The pK value of the stronger acid is typical for carboxyl group in uronic acids. The polyelectrolyte adsorption indicates that most of the carboxyl groups are located in an inner region of all cellulose samples (cotton and regenerated fibers). It is concluded that titration methods are powerful tools for monitoring the content, strength, and distribution of acidic groups, as well as the total charge of natural and regenerated cellulose fibers. The three methods give similar results on all analyzed samples and show good repeatability. The results of investigation make it quite clear that combination of all titrations yields relevant information about content and strength of acidic groups in both natural and regenerated cellulose fibers used in the manufacture of textiles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3186–3195, 2004     

Flame-retardant action of chlorine compounds and antimony trioxide on cellulose fabric

Chemical research on the flame-retardant action of halogen compounds and antimony trioxide on cellulose fabric was carried out by thermogravimetry, infrared spectrum analysis, and x-ray diffraction analysis. The following results and conclusion were drawn: (1) Independently of the type of chlorine atoms introduced, that is, whether chlorine atoms are chemically bonded with cellulose chains or not, the introduction of chlorine atoms alone has little flame-retardant effect, while combination of chlorine atoms with antimony trioxide is more effective. (2) Addition of only antimony trioxide to samples obtained from the dechlorination of chlordeoxycellulose is as effective as the combination of chlorine compounds and antimony trioxide, in spite of a trace of chlorine in the DCDC samples. (3) Introduction of chlorine compounds yielded the formation of carbonyl and double bond groups in the cellulose chains. The formation of the latter groups was accelerated by the combination of antimony trioxide; that of the former groups was inhibited. Most of the introduced chlorine atoms were missing in the condensed phase even at 300°C while a large portion of the initially added antimony trioxide remained in the condensed phase at least up to 400°C. One mode of flame-retardant action of the combination of chlorine compounds and antimony trioxide was assumed to be the catalytic effect on the dehydration of cellulose to yield a thermostable polyene structure in the cellulose chains.     

The Influence of an Ozone,Chlorine and Chlorine Dioxide Treatment on Mutagentic Activity in (Drinking) Water

Three disinfectants, viz. chlorine, chlorine dioxide, and ozone, were compared with respect to the formation of organic mutagens and halogenated organic compounds in drinking water. Chlorine increased the mutagenic activity (Ames test) drastically, as well as the level of halogenated organics. High chlorine dioxide doses (5 – 15 mg/L C10₂) also showed a drastic increase of mutagenic activity, while relatively low doses of chlorine dioxide (< 5 mg/L CIO₂) in most cases showed no effect or a slight increase in mutagenic activity. Hardly any increase in the level of halogenated organics was observed after this treatment.