Oxidative Bleaching Research Articles

High-Resolution Peat Core Chronology Covering the Last 12 KYR Applying an Improved Peat Bog Sampling

ABSTRACTThis work focuses on building a high-resolution age-depth model for quantitative palaeoclimate study from the Mohos peat bog, East Carpathian mountains. The investigated core presents a continuous peat profile for the last 12 kyr. The chronology was based on 36 accelerator mass spectrometry radiocarbon (AMS14C) analyses of the separatedSphagnumsamples from different depths of the profile. DrySphagnumsamples for AMS dating were prepared using the classic acid-base-acid (ABA) method followed with an oxidative bleaching step to get clean cellulose.Sphagnumcellulose samples were measured by AMS using the EnvironMICADAS at the ICER (Debrecen, Hungary). A high-resolution chronology was obtained with the use of Bayesian age-depth modeling. Peat accumulation rate has been calculated and the sections with variable accumulation rate values were observed along the profile.

Uric Acid: A Less-than-Perfect Probe for Singlet Oxygen.

Uric acid and/or its monoanion has long been used as chemical-trapping agents to demonstrate the presence of singlet oxygen, O2 (a1 Δg ), in aqueous systems. "Oxidative bleaching" of uric acid, generally monitored through changes in the uric acid absorption spectrum, is often used in support of claims for the intermediacy of O2 (a1 Δg ). The bleaching of uric acid has also been used to quantify photosensitized O2 (a1 Δg ) yields in selected systems. Unfortunately, experiments performed to these ends often neglect processes and phenomena that can influence the results obtained. For the present study, we experimentally examined the behavior of uric acid under a variety of conditions relevant to the photoinitiated creation and subsequent removal of O2 (a1 Δg ). Although the oxidative destruction of uric acid can indeed be a useful tool in some cases, we conclude that caution must be exercised such as not to incorrectly interpret the data obtained.

Protective Bleaching of Camel Hair in a Neutral Ethanol⁻Water System.

As conventional bleaching under alkaline conditions is chemically damaging to protein fibers, a three-stage protective bleaching process in neutral ethanol–water mixtures was proposed for camel hair using mordanting with ferrous salts, oxidative bleaching with hydrogen peroxide, and reductive bleaching with sodium hydrosulfite. The aim of this work was to improve the whiteness degree of camel hair without substantial tenacity loss. In addition, the roles of ethanol during the bleaching treatment were also examined by characterizing the fibers using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction. The whiteness degree and mechanical properties of camel hair bleached in the neutral ethanol–water system were significantly superior to those of fibers bleached by a conventional method. SEM images showed no visible cracks on the scales of fibers bleached in the ethanol–water system, whereas large grooves were observed on fibers bleached in aqueous solution. TEM images confirmed the positive influence of ethanol on the mordanting process, and FTIR spectra suggested that ethanol reduced the breakage of hydrogen bonds in the fibers during the oxidative bleaching process. These findings indicate the potential of this protective bleaching method for application to a broad range of other natural protein fibers.

2,4,5-Trihydroxy-3-methylacetophenone: A Cellulosic Chromophore as a Case Study of Aromaticity.

The title compound (2,4,5-trihydroxy-3-methylacetophenone, 1) was isolated as chromophore from aged cellulosic pulps. The peculiar feature of the compound is its weak aromatic system that can be converted into nonaromatic (quinoid or cyclic aliphatic) tautomers, depending on the conditions and reaction partners. In alkaline media, the participation of quinoid canonic forms weakens aromaticity, whereas in neutral and acidic media, the strong hydrogen bond between the 2-hydroxyl group and the acetyl moiety plays an important role in favoring quinoid tautomers. As a result, compound 1, with quinoid contributions being already “preset”, is relatively stable toward oxidation and hardly undergoes alkylation or nitration at CH-6, whereas the 2,4,5-trimethoxyderivative, being “properly” aromatic and even more sterically hindered, is readily alkylated or nitrated. The lability of the aromatic system is best demonstrated by the unusual reaction of 1 with hydroxylamine, producing a tetroxime that is derived from its 2,4,5-triketo tautomer. The high oxidative stability and low reactivity of the compound hinder oxidative bleaching of this chromophore in cellulosic pulps and detection reactions for analytical purposes.

Exploring an oxidative bleaching treatment for Chilean bamboo: a source of cellulose for biofuel generation and the nanotech industry

Quila (Chusquea quila) is a very abundant native Chilean bamboo species. This work reports on a delignification process which can be applied to quila to produce crystalline cellulose, an important resource for obtaining cellulose nanofibres or nanocrystals. Alternatively, the crystalline cellulose can then be subjected to fermentation processes, making it a useful raw material for biofuel production. The treatment studied is an oxidative treatment at low concentration (15% v/v), for short time periods (10, 20 min) and at temperatures between 100 and 140 °C, which produces alpha-cellulose fibres with high crystallinity (over 70%) and low residual lignin content (< 2%). The morphology of the cellulose fibres was analysed by scanning electron microscope, revealing a smooth surface containing many fibrils. Infrared spectroscopy was used to identify functional groups, showing that almost 99% of the lignin was removed. The crystallinity index of the cellulose fibres after the reaction was up to 79%, making it an excellent raw material for processing cellulose nanofibres required by the emerging nanotech industry. Carbohydrate analysis revealed 86% glucose and 14% xylose, which makes quila a promising candidate as a precursor for biofuel generation.

Ozone bleaching of cellulose

In this study, ozone treatment has been investigated in seeking of a more environmentally friendly alternative process for bleaching of cellulosic fibers. The primary advantage of ozone treatment is reduced environmental impact especially in case of chemical oxygen demand (COD) values of the process effluent. The highly oxidative ozone gas substitutes conventional harsh chemicals and decomposes back to oxygen owing to its limited half-life. Hence, ozone treatment seems as a good alternative for oxidative bleaching purposes of cellulose.

A Study of the Adsorptive and Oxidative Bleaching of Palm Oil Using Clay and Potassium Tetraoxomanganate V11 Materials

Fats and oils undergo hydrolysis reaction. They hydrolyse to yield propane-1,2,3 triol and the corresponding alkanoic acids if it is acid hydrolysis. Alkaline hydrolysis yields sodium or potassium salt of the alkanoic acid and propane-1,2,3-triol. A common approach for bleaching palm oil has been the use of clay materials, particularly the commercially available fuller’s earth. In this study, the suitability of chemical bleaching of palm oil using acidified (0.1M H2SO4) and non-acidified 1.0M KMnO4 was examined. This is compared to the adsorptive procedure using clay materials. Average bleaching absorbance values of 0.017+0.005 and 0.115+0.004 for acidified and non-acidified KMnO4 were respectively obtained from the oxidative bleaching procedure. Those for fuller’s earth and its blend with sodium sesquicarbonate (trona, a locally obtained clay) gave absorbance values of 0.121+0.011 and 0.186+0.006 respectively; while that for trona/activated carbon blend was 0.234+0.007. These are in comparison to 0.881 for the unbleached palm oil. Thus, a relatively better bleaching was achieved with the oxidative process. A first order rate reaction with respect to the bleaching agents was obtained for both procedures. Rate constants of 0.079+014 (acidified) and 0.055+0.020min-1 (non-acidified) at 800C were recorded for the oxidative bleaching. These are compared to 0.034+0.009 obtained for the clay mixture. Half-life values of 10min for acidified oxidative process, and 28min for adsorptive clay mixture method, were obtained. Efficiency of 98% was obtained for the acidified oxidative compared to approximately 70% for the clay blend. A significance, p&lt; 0.05, between the absorbance values for the acidified oxidative and each of the adsorptive clay bleaching procedures was obtained.These observations indicate the potentials of oxidizing agents especially the acidified KMnO4 in the bleaching of palm oil, and therefore, suggest its usage industrially for this purpose.

The investigation of oxidative bleaching performance of peripherally Schiff base substituted tri-nuclear cobalt-phthalocyanine complexes

This study covers the functional complexes of tetrakis [4-(salicyhydrazone)phenoxy)] phthalocyaninato cobalt (II) (5) which was the macro molecular Schiff base ligand and synthesized through a multistep reaction sequence starting first with the cyclotetramerization of 4-[4-(1,3-Dioxolan-2-yl)phenoxy]-phthalonitrile (2). Then, the de-protection of tetra acetal groups of Tetrakis[4-(1,3-dioxolan-2-yl)phenoxy)]phthalocyaninato cobalt (II) (3) to the aldehyde functionality in acetic acid/FeCl3 system to yield the Tetrakis(4-formylphenoxy)phthalocyaninato cobalt(II) (4) and then its condensation with salicylhydrazide gave to 5. Finally, CoPc-bis(salicyhydrazone)phenoxy)manganese (III) (6), CoPc-bis(salicyhydrazone) phenoxy)cobalt(III) (7) and CoPc-bis (salicyhydrazone)phenoxy) nickel(II) (8) were synthesized using with the related MnCl2·4H2O, CoCl2·6H2O, Ni(CH3COO)2 salt in basic conditions in DMF. FT-IR, UV–Vis, MS spectra and elemental analysis were applied to characterize to prepared compounds.The bleaching performances of the prepared phthalocyanine compounds (3–8) were examined by the degradation of Morin as the hydrophilic dye which characterized the wine stains on the fabrics. Progress of the degradations in the catalysts (3–8)/H2O2 combination in basic aqueous solution conditions was investigated by using online spectrophotometric method (OSM). It was found that the prepared catalysts showed better bleaching performance at 25°C than to that of tetraacetylethylenediamine (TAED) bleach activator commercially used in powder detergent formulations.

Exogenous spermidine delays chlorophyll metabolism in cucumber leaves (Cucumis sativus L.) under high temperature stress

This study evaluated the effects of exogenous spermidine (Spd) on chlorophyll (Chl) biosynthesis and catabolism in the leaves of cucumber (Cucumis sativus L.) seedlings under high temperature stress. Substrate culture experiments were performed using the high temperature-sensitive variety ‘Jinchun No. 2’ in an artificial climate chamber at 42/32 °C with foliar applications of 1.0 mmol L−1 Spd. The results suggested that high temperature stress markedly reduced the leaf Chl concentrations and inhibited plant growth; the harmful effect of high temperature on the cucumber seedlings was mitigated by exogenous Spd, which increased the leaf Chl concentration and promoted plant growth. Under high temperature stress, the conversion of porphobilinogen (PBG) into uroporphyrinogen III (UroIII) in the Chl biosynthetic pathway and the catabolic process of Chl were accelerated. Following the application of exogenous Spd, the conversion of PBG into UroIII was suppressed, and the accumulation of certain intermediates, e.g., protoporphyrin IX (ProtoIX) and Mg-protoporphyrin IX (Mg-ProtoIX), was decreased in the Chl biosynthetic pathway. Additionally, exogenous Spd reduced chlorophyllase (Chlase) and Mg-dechelatase (MDCase) activity and transcript levels and markedly downregulated pheophorbide A oxygenase (PaO), red Chl catabolite reductase (RCCR), Chl b reductase 1 (CBR1) and stay-green reductase 1 (SGR1) transcript levels. These results indicate that although high temperature stress accelerated Chl biosynthesis, it concurrently facilitated Chl catabolism in cucumber leaves. Exogenous Spd delayed the conversion of PBG into UroIII in the Chl biosynthetic pathway, effectively preventing oxidative bleaching of Chl in cucumber leaves. Meanwhile, Spd clearly decreased PaO pathway-related enzyme activity and transcript levels, thereby slowing Chl catabolism and increasing Chl concentrations.

Immobilized Lignin Peroxidase-Like Metalloporphyrins as Reusable Catalysts in Oxidative Bleaching of Industrial Dyes.

Synthetic and bioinspired metalloporphyrins are a class of redox-active catalysts able to emulate several enzymes such as cytochromes P450, ligninolytic peroxidases, and peroxygenases. Their ability to perform oxidation and degradation of recalcitrant compounds, including aliphatic hydrocarbons, phenolic and non-phenolic aromatic compounds, sulfides, and nitroso-compounds, has been deeply investigated. Such a broad substrate specificity has suggested their use also in the bleaching of textile plant wastewaters. In fact, industrial dyes belong to very different chemical classes, being their effective and inexpensive oxidation an important challenge from both economic and environmental perspective. Accordingly, we review here the most widespread synthetic metalloporphyrins, and the most promising formulations for large-scale applications. In particular, we focus on the most convenient approaches for immobilization to conceive economical affordable processes. Then, the molecular routes of catalysis and the reported substrate specificity on the treatment of the most diffused textile dyes are encompassed, including the use of redox mediators and the comparison with the most common biological and enzymatic alternative, in order to depict an updated picture of a very promising field for large-scale applications.

Stability, redox parameters and electrocatalytic activity of a cytochrome domain from a new subfamily

We report a spectroscopic, electrochemical and spectroelectrochemical characterization of the soluble cytochrome c domain (Cyt-D) from the Rhodothermus marinus caa3 terminal oxygen reductase and its putative electron donor, a high potential [4Fe–4S] protein (HiPIP). Cyt-D exhibits superior stability, particularly at the level of the heme pocket, compared to archetypical cytochromes in terms of thermal and chemical denaturation, alkaline transition and oxidative bleaching of the heme, which is further increased upon adsorption on biomimetic electrodes. Therefore, this protein is proposed as a suitable building block for electrochemical biosensing. As a proof of concept, we show that the immobilized Cyt-D exhibits good electrocatalytic activity towards H2O2 reduction. Relevant thermodynamic and kinetic electron transfer parameters for Cyt-D and HiPIP are also reported, including reorganization energies of 0.33eV and 0.42eV, respectively.

Effect of fitting sheep covers and injection of a mineral supplement on the brightness, clean colour and photostability of wool grown by grazing Merino sheep

Wethers sourced from a Merino genetic resource flock, selected on the basis of their measured wool clean colour at 2 years of age, were stratified on the basis of clean colour and allocated to one of four treatment groups in a 2 × 2 factorial design. The aim was to investigate the effect of coating the fleece and administration of a commercial mineral supplement on brightness, clean colour and photostability over a 12-month period when run on the Central Tablelands of New South Wales. Coating the fleece significantly improved both the brightness and clean colour of the fleece (P&lt;0.001, by 4 and 0.5 T units, respectively), but had no effect on the photostability of the two traits. The mineral supplement had no significant impact on the colour or photostability traits and there was no evidence of an interaction between coating the fleece and the mineral supplement. Although the improvements in brightness and colour arising from coating the fleece complemented the predicted responses to genetic selection for these two traits, the combined effect would not be sufficient to replace the routine use of oxidative bleaching during processing.

The Bleaching of Soybean Fabric by Different Treatments Combined with Ozonation

This article is about bleaching of soybean fibers. Although the studies related to dyeing of soybean fibers have been found in the literature, little has been reported on the effect of bleaching. The natural color of soybean protein fibers is pale yellow or cream, and it is therefore usually necessary to bleach them to improve their whiteness. Different bleaching treatments combined with ozonation were performed in order to establish the effect on whiteness, yellowness, lightness, wettability, hydrophility, moisture sorption, and fiber damage properties of knitted soybean fabric. As a result of study, bleaching process combined with ozonation (ozonation + oxidative bleaching + reductive bleaching) supplied soybean fabric with a white appearance (highest whiteness degree), highest hydrophility, and minimal fiber damage.

Regenerate Cr(VI) Oxidation Bleaching Solution from Wastewater in Process of Oxidation Bleaching of Montan Wax by Indirect Electrochemical Oxidation

Regenerate Cr(VI) Oxidation Bleaching Solution from Wastewater in Process of Oxidation Bleaching of Montan Wax by Indirect Electrochemical Oxidation

Reactive Dyeing of Bio Pretreated Cotton Knitted Fabrics

This study describes the feasibility and optimization of reactive dyeing on bio treated cotton knitted fabrics. For this, cotton knitted fabrics distinctly with two different enzymes, alkaline Pectinases(Scourzyme <TEX>$L^{(R)}$</TEX>) and Pectate lyases(Bactosol Co. ip <TEX>$liquor^{(R)}$</TEX>). In this way by increasing the concentration and processing temperature, the access of enzymes towards the fatty and waxy substrate was found to be accelerated. To achieve higher absorbency and whiteness index, a series of experiments was carried out to assure that Pectate lyases enzymes possesses high access towards the fats and waxes at high temperature. To this end, cotton knitted fabrics was dyed without oxidative bleaching step. The Pectate lyases scoured and dyed fabrics showed less color difference when 2% dye shade is used. The fabrics pre-scoured with Pectate lyases showed good the light and washing fastness properties, compared to the conventional and Pectinases dyed fabrics. However pectinases enzymes showed lower activity at high temperature, caused poor wettability and whiteness index of fabrics. The improvement of the accessibility of enzyme to the pectin at higher temperature Pectate lyases treatment before dyeing was found to be useful for subsequent pectin degradation in cotton knitted fabrics.

A Study on Damage to PLA Knitted Fabrics During Scouring and Bleaching

Abstract Ingeo® PLA (polylactic acid) knitted fabric was scoured through an exhaust technique. The scouring was carried out with sodium carbonate in the presence of a detergent at various concentrations and temperatures. The scoured fabric was bleached with various oxidative bleaching agents. Bleaching was carried out with hydrogen peroxide, sodium chlorite and sodium hypochlorite. Hydrogen peroxide was applied by exhaust and cold pad batch (CPB) techniques. It was observed that during scouring PLA fabric was degraded at high alkali concentrations and processing temperatures. The scouring temperature above 60ºC proved to be deleterious due to the scouring solution penetrating into the polymer structure and damaged the fiber. Sodium chlorite and sodium hypochlorite caused little damage to the mechanical properties of PLA. Hydrogen peroxide when applied by the CPB technique did not reduce strength appreciably but when applied by the exhaust technique decreased the strength significantly. SEM analysis revealed that hydrogen peroxide caused holes and slit formation in the fiber structure.

Extraction of palm tree cellulose and its functionalization via graft copolymerization

The work in this paper was planned with the aim of extracting the cellulosic component of palm tree waste and functionalizing this cellulose through graft copolymerization with acrylic acid. The cellulose extraction included hot alkali treatment with aqueous sodium hydroxide to remove the non-cellulosic binding materials. The alkali treatment was followed by an oxidative bleaching using peracid/hydrogen peroxide mixture with the aim of removing the rest of non-cellulosic materials to improve the fiber hydrophilicity and accessibility towards further grafting reaction. Optimum conditions for cellulose extraction are boiling in 5% (W/V) NaOH in a material to liquor ratio of 1:20 for 1h then bleaching with 60ml/l bleaching mixture at initial pH value of 6.5 for 30min. The pH of the bleaching medium is turned to the alkaline range 11 and bleaching continues for extra 30min. Graft copolymerization reaction was initiated by potassium bromate/thiourea dioxide redox system. Optimum conditions for grafting are 30mmol of potassium bromate, 30mmol of thiourea dioxide and 150g of acrylic acid (each per 100g of cellulose). The polymerization reaction was carried out for 120min at 50°C using a material to liquor ratio of 1:20.

Quantum yield measurements for the photocatalytic oxidation of Acid Orange 7 (AO7) and reduction of 2,6-dichlorindophenol (DCIP) on transparent TiO2 films of various thickness

This work comprises the photoactivity assessment of transparent sol–gel TiO2 coatings of various thickness using two test systems. The initial rates of both photocatalytic reactions, namely the oxidative bleaching of Acid Orange 7 (AO7) and the reductive bleaching of 2,6-dichlorindophenol (DCIP) increase linearly with increasing titania film thickness as well as with increasing absorbed light flux. The latter work revealed quantum yields (QY) of 0.19% and 92% for the AO7 and DCIP test system, respectively. The low QY for the AO7 oxidation is due to the combination of a slow irreversible reduction of oxygen and also for the oxidation of AO7, thus favouring the high efficiency for electron–hole recombination that is typical for aqueous organic pollutants. In contrast, the very high QY for the photocatalysed reduction of DCIP is due to the presence of a vast excess of glycerol which traps the photogenerated holes efficiently and so allow time for the slower reduction of dye to take place. Furthermore, the oxidation of glycerol results in the generation of highly reducing R-hydroxyalkyl radicals that are able to also reduce DCIP. As a consequence of this ‘current doubling’ effect, the observed QY (92%) is much higher than the apparent theoretical value of 50%.

Biodegradable chelating agents for industrial, domestic, and agricultural applications—a review

Aminopolycarboxylates, like ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), are chelating agents widely used in several industrial, agricultural, and domestic applications. However, the fact that they are not biodegradable leads to the presence of considerable amounts in aquatic systems, with serious environmental consequences. The replacement of these compounds by biodegradable alternatives has been the object of study in the last three decades. This paper reviews the most relevant studies towards the use of environmentally friendly chelating agents in a large number of applications: oxidative bleaching, detergents and cleaning compositions, scale prevention and reduction, remediation of soils, agriculture, electroplating, waste treatment, and biocides. Nitrilotriacetic acid (NTA), ethylenediaminedisuccinic acid (EDDS), and iminodisuccinic acid (IDS) are the most commonly suggested to replace the nonbiodegradable chelating agents. Depending on the application, the requirements for metal complexation might differ. Metal chelation ability of the most promising compounds [NTA, EDDS, IDS, methylglycinediacetic acid (MGDA), L-glutamic acid N,N-diacetic acid (GLDA), ethylenediamine-N,N'-diglutaric acid (EDDG), ethylenediamine-N,N'-dimalonic acid (EDDM), 3-hydroxy-2,2-iminodisuccinic acid (HIDS), 2-hydroxyethyliminodiacetic acid (HEIDA), pyridine-2,6-dicarboxylic acid (PDA)] with Fe, Mn, Cu, Pb, Cd, Zn, Ca, and Mg was simulated by computer calculations. The advantages or disadvantages of each compound for the most important applications were discussed.

Phenolic profile and antioxidant properties of a crude extract obtained from a brewery waste stream

The main aims of this study were to determine the phenolic profile of a crude extract obtained (at pilot scale) from a brewery waste stream and to evaluate the antioxidant activity of the extract. The total phenolic content was determined by the Folin–Ciocalteu assay, which revealed that 50% of the extract comprised phenolic compounds. The polyphenols, identified and quantified by RP-HPLC–DAD and HPLC-ESI–TOF-MS, were mainly flavonoids (catechin, epicatechin, gallocatechin, epigallocatechin, quercetin) and phenolic acids (ferulic acid, p-coumaric acid, caffeic acid, protocatechuic acid). The crude extract displayed a high DPPH radical scavenging activity (0.18g/L), similar to that of BHA (0.248g/L) and higher than that of BHT (2.54g/L). All three tested products displayed a similar ability to decrease oxidative bleaching of β-carotene (antioxidant activity coefficient of 623.8 for the crude extract, 653.3 for BHA, 559.6 for BHT). This type of brewery waste stream may be a promising source of natural antioxidants to replace the synthetic antioxidants currently used in the food industry.