Research in the cold pad–batch dyeing process for wool pretreated by hydrogen peroxide

The cold pad–batch dyeing process of wool pretreated by hydrogen peroxide was carried out with Lanasol reactive dyes and Realan reactive dyes. The influences of various conditions of the dyeing process, including urea dosage, sodium bisulphite dosage, pH value, batching time and the liquor pickup on colour yield, were analysed. Fixation, levelness of dyeing, dye penetration, colour fastness, breaking strength and elongation were compared between untreated and treated wool fabrics. The study showed that cold pad–batch dyeing of wool fabric is a good prospect for future use because of the resulting advantages, such as higher fixation yield, less energy usage and lower sewage discharge.     

Comparison of four oxidants activated through tetraacetylethylenediamine for developing sustainable and rapid degradation of organic dye

Four common oxidants, including hydrogen peroxide (H₂O₂), sodium percarbonate (SPC), sodium perborate (SPB) and sodium persulphate (SPS), were activated with tetraacetylethylenediamine (TAED) to degrade an azo dye, CI Reactive Red 195, in water, for building a novel and rapid oxidative system comprising the merits of cost‐effectiveness and high sustainability. Elevated temperature and high pH level enhanced the activation effect of TAED for accelerating dye degradation. Peracetic acids were confirmed to be the main oxidative species for dye degradation in four TAED/oxidant systems. Hydroxyl radicals and sulphate radicals were also involved in dye degradation in the TAED/SPS system, which showed a stronger oxidative capacity than the other three systems over a wide pH range. More importantly, the addition of inorganic salts or surfactants also favoured the dye degradation in TAED/oxidant systems. Although a slow mineralisation process of the dye was found when the TAED/SPC or SPS system was used, low‐toxic intermediates were detected after the degradation.     

Application of urea/H2O2 activation‐oxidation system in degradation of PVA and desizing of polyester/cotton fabric

The viscosity and the UV–vis spectrum of PVA degradation aqueous solutions, the FTIR, and DSC spectrums of degradation products were measured to investigate and compare the effect of Fenton's reagent and urea/H₂O₂ activate oxidation systems on the degradation of PVA. The results showed that the viscosity of PVA aqueous solution decreased and the degradation rate of PVA increased with the concentration of hydrogen peroxide in both activate oxidation systems. The FTIR and DSC spectrum of degradation products showed that the degradation products contained aldehyde, ketone groups. The aldehyde compounds and carbon dioxide produced in the degradation systems were validated by Fehling reagents and clarifying limewater. When the urea/H₂O₂ system was applied in the one‐bath and one‐step desizing and scouring process of polyester/cotton 65/35 fabric, the results of 94.7% degradation rate of PVA, the 99.0% desizing rate of PVA, the whiteness, and wicking height of the fabric were obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ozone-Based Advanced Oxidation Processes for the Decomposition of N-Methyl-2-Pyrolidone in Aqueous Medium

The present study investigates the decomposition of N-Methyl-2-Pyrolidone (NMP) using conventional ozonation (O₃), ozonation in the presence of UV light (UV/O₃), hydrogen peroxide (O₃/H₂O₂), and UV/H₂O₂ processes under various experimental conditions. The influence of solution pH, ozone gas flow dosage, and H₂O₂ dosage on the degradation of NMP was studied. All ozone-based advanced oxidation processes (AOPs) were efficient in alkaline medium, whereas the UV/H₂O₂ process was efficient in acidic medium. Increasing ozone gas flow dosage would accelerate the degradation of NMP up to certain level beyond which no positive effect was observed in ozonation as well as UV light enhanced ozonation processes. Hydrogen peroxide dosage strongly influenced the degradation of NMP and a hydrogen peroxide dosage of 0.75 g/L and 0.5 g/L was found to be the optimum dosage in UV/H₂O₂ and O₃/H₂O₂ processes, respectively. The UV/O₃ process was most efficient in TOC removal. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of NMP in wastewater.     

Development of a one-stage process for pretreatment and cationisation of cotton fabric

A one-stage process for cationisation and pretreatment of cotton fabric was developed. Cationisation of cotton cellulose was carried out with 3-chloro-2-hydroxypropyltrimethylammonium chloride, whereas pretreatment comprised enzymatic and oxidative desizing, scouring, bleaching with hydrogen peroxide, combined desizing and scouring as well as combined desizing, scouring and bleaching. Each of these pretreatment operations or their combination with and without cationisation was carried out using three techniques, namely, cold pad–batch, pad–steam and exhaustion. It was found that the cationisation chemicals were compatible with the scouring ingredients and, to a lesser extent, with the formulation of enzymatic desizing. On the other hand, cationisation chemicals were not compatible with oxidative desizing or peroxide bleaching ingredients. Efficiency of the one-step process for scouring and cationisation was maximised through detailed investigation of the process parameters. The treated fabric can be dyed without electrolyte and the fabrics show a high levelness of colour shade, residual wax content and nitrogen content.     

UVA-LED assisted persulfate/nZVI and hydrogen peroxide/nZVI for degrading 4-chlorophenol in aqueous solutions

Photocatalytic degradation of 4-chlrophenol (4-CP) using UVA-LED assisted persulfate and hydrogen peroxide activated by the nZVI (Nano Zero Valent Iron) in a batch photocatalytic reactor was investigated. The reaction involved a lab-scale photoreactor irradiated with UVA-LED light emitted at 390 nm. The efficiency of the reaction was evaluted in terms of 4-CP degradation and mineralization degree at different pH of solution, initial concentrations of nZVI, persulfate, hydrogen peroxide and 4-CP. In UVA-LED/H₂O₂/nZVI process, complete degradation of 4-CP (>99%) and 75% mineralization was achieved at pH of 3, hydrogen peroxide concentration of 0.75 mM, nZVI dosage of 1mM and initial 4-CP concentration of 25mg/L at the reaction time of 30 min. The optimum conditions obtained for the best 4-CP degradation rate were at an initial concentration of 25mg/l, persulfate concentration of 1.5mM, nZVI dosage of 1mM, pH of 3 and reaction time of 120min for UVA-LED/persulfate/nZVI process. It was also observed that the 4-CP degradation rate is dependent on initial 4-CP concentrations for both processes. The pseudo-first-order kinetic constant at 25mg/L initial concentration of 4-CP was found to be 1.4×10^?1 and 3.8×10^?2 in UVA-LED/H₂O₂/nZVI and UVA-LED/persulfate/nZVI processes, respectively. Briefly, the UVA-LED/H₂O₂/nZVI process enhanced the degradation rate of 4-CP by 3.67-times in comparison to UVA-LED/persulfate/nZVI process at 30min contact time, which serves as a new and feasible approach for the degradation of 4-CP as well as other organic contaminants containing wastewater.     

Decolorization of colored poly(ethylene terephthalate) bottle flakes using hydrogen peroxide

A novel process for the oxidative decolorization of green and blue colored poly(ethylene terephthalate) (PET) bottle flakes, using an aqueous solution of hydrogen peroxide (H₂O₂) has been developed. A strong dependence of H₂O₂ concentration and temperature on decolorization rate has been found. The decolorized flakes were characterized for color and intrinsic viscosity (IV) values; decolorized flakes exhibit color values similar to those of colorless recycled PET. The IV of peroxide bleached PET flakes indicated a decrease in PET molecular weight, which correlated with the severity of decolorization conditions. Despite decreases in PET IV values, the bleached flake still exhibited useful PET molecular weights. The consumption of H₂O₂ during the bleaching process was quantified titrating residual peroxide with a standardized potassium permanganate solution. H₂O₂ consumption rates of 0.3–0.9 g per gram of green PET flake were measured, depending on the specific bleaching conditions used. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008     

An evaluation of the effectiveness of applying a gelatin–copper complex in the low-temperature bleaching of cotton with hydrogen peroxide

A gelatin–copper complex was prepared and then added as catalyst to a hydrogen peroxide bleaching bath. Cotton fabric was bleached with the new system at low temperature (70 °C). The effects of the gelatin–copper complex on the whiteness, capillary effect, damage, and bleaching rate of the bleached fabric and on the decomposition ratio of hydrogen peroxide were evaluated. These effects were compared with the effectiveness of traditional high-temperature bleaching and low-temperature bleaching without the gelatin–copper complex. The results showed that the gelatin–copper complex enhances the bleaching effectiveness of hydrogen peroxide. The whiteness of cotton fabric bleached with the catalytic complex is comparable with the whiteness achieved with a conventional peroxide system. The catalytic bleaching technology not only realises low-temperature and low-alkali bleaching of cotton with hydrogen peroxide but also reduces fabric strength loss, which meets the requirements of industry for continued development of the wet processing of textiles.     

Direct synthesis of hydrogen peroxide from H2/O2 and oxidation of thiophene over supported gold catalysts

Direct synthesis of hydrogen peroxide from H₂ and O₂ was performed over supported gold catalysts. The catalysts were characterized by means of UV–vis, H₂-TPR, TEM and XPS. Based on the results we conclude that metallic Au is the active species in the direct synthesis of hydrogen peroxide from H₂ and O₂. During preparation process of catalyst by deposition–precipitation with urea, the pH value increased and the gold particle size decreased with increasing the urea concentration. The catalyst prepared with higher urea concentration showed a higher activity and its stability also was efficiently improved. Gold nanoparticles, supported on TiO₂ or Ti contained supports, gave a higher catalytic activity. Thiophene can be efficiently oxidized by hydrogen peroxide synthesized in situ from H₂ and O₂ over Au/TS-1.     

Decomposition of hydrogen peroxide in the presence of activated carbons with different characteristics

BACKGROUND: Catalytic ozonation promoted by activated carbon is a promising advanced oxidation process used in water treatment. Hydrogen peroxide generated as a by‐product from the reaction of ozone with some surface groups on the activated carbon or from the oxidation of some organic compounds present in the water being treated seems to play a key role in the catalytic ozonation process. Hydrogen peroxide decomposition promoted by two granular activated carbons (GAC) of different characteristics (Hydraffin P110 and Chemviron SSP‐4) has been studied in a batch reactor. The operating variables investigated were the stirring speed, temperature, pH and particle size. Also, the influence of metals on the GAC surface, that can catalyze hydrogen peroxide decomposition, was observed. RESULTS: Chemviron SSP‐4 showed a higher activity to decompose hydrogen peroxide than HydraffinP110 (70 and 50% of hydrogen peroxide removed after 2 h process, respectively). Regardless of the activated carbon used, hydrogen peroxide decomposition was clearly controlled by the mass transfer, although temperature and pH conditions exerted a remarkable influence on the process. Catalytic ozonation in the presence of activated carbon and hydrogen peroxide greatly improved the mineralization of oxalic acid (a very recalcitrant target compound). About 70% TOC (total organic carbon) depletion was observed after 1 h reaction in this combined system, much higher than the mineralization achieved by the single processes used. CONCLUSIONS: Of the two activated carbons studied, Chemviron SSP‐4 with an acidic nature presented a higher activity to decompose hydrogen peroxide. However the influence of the operating variables was quite similar in both cases. Experiments carried out in the presence of tert‐butanol confirmed the appearance of radical species. A kinetic study indicated that the process was controlled by the internal mass transfer and the chemical reaction on the surface of the activated carbon. The catalytic activity of hydrogen peroxide in oxalic acid ozonation promoted by activated carbon (O₃/AC/H₂O₂) was also studied. The results revealed the synergetic activity of the system O₃/AC/H₂O₂ to remove oxalic acid. Copyright © 2010 Society of Chemical Industry     

Novel bleach activator compounds derived from the reaction of isocyanic acid with selected nucleophiles

Laundry detergents commonly contain bleach activators that react with the perhydroxy anion produced from perborate or percarbonate anions to form activated peroxy compounds; these enhance bleaching and stain removal capacity especially at lower temperatures, hydrogen peroxide being an inefficient bleach below 60°C. The most commonly used activators are N, N, N′, N′-tetraacetylethylenediamine (TAED) and sodium nonanoyloxybenzenesulphonate (SNOBS) the former being used across Europe whereas the latter is used widely in the United States and Japan. This research studies the preparation of novel activator compounds which are carbamylated derivatives of selected nucleophiles using either solid or aqueous reactions of nucleophilic carboxylate anions with the highly reactive isocyanic acid entity derived from the acidification of sodium cyanate. The novel activator compounds were then assessed as bleach activators by testing against tea and bilberry-stained cotton reference fabrics at 40°C in the presence of hydrogen peroxide at pH values ranging from 4 to 10; bleaching efficiency was assessed visually and colorimetrically. Results showed that all of the synthesised compounds were more effective bleach activators across the pH range tested than the standard TAED system.     

H2O2 Generation during Carbon Ozonation – Factors Influencing the Process and Their Implications

Hydrogen peroxide generation during contact of aqueous ozone with activated carbon surface is an established process. However, no systematic research concerning this phenomenon has been conducted. In this paper, factors affecting H₂O₂ generation are presented. Formation of hydrogen peroxide in contact of ozone with carbon is a surface phenomenon, strongly affected by the solution pH. Re-ozonation of the same carbon sample does not lead to H₂O₂ generation. Additionally, the amount of generated H₂O₂ is significant only in strongly acidic environment. It implies that hydrogen peroxide generated by surface of activated carbon cannot be ozone decomposition initiator in catalytic ozonation based on activated carbon as a catalyst.     

Purification of Wet‐Process Phosphoric Acid by Hydrogen Peroxide Oxidation,Activated Carbon Adsorption and Electrooxidation

In this work, three technologies are studied for the purification of phosphoric acid produced by the wet process: chemical oxidation with hydrogen peroxide, adsorption onto activated carbon, and electrochemical oxidation by boron‐doped diamond anodes. The treatment of wet‐process phosphoric acid by chemical oxidation with H₂O₂ as oxidizing agent can remove 75 % of the initial TOC as maximum, indicating that this wet‐process phosphoric acid contains an important amount of organics that cannot be oxidized by hydrogen peroxide under the operation conditions used. High temperatures and hydrogen peroxide/TOC ratios close to 150 g H₂O₂/g TOC allow obtaining the best chemical oxidation results. The adsorption onto activated carbon can remove between 40 and 60 % of the initial TOC as maximum. Adsorption times of 2 hours and activated carbon/WPA ratios close to 12 g AC/Kg WTP assure both steady state and maximum adsorption of organics. The electrochemical process is the only technique by which complete mineralization of WPA organics can be achieved. Operating at 60 mA cm^–2 and at room temperature, high current efficiencies are achieved which only seem to decrease by mass transport limitations.     

The Peroxysilicate Question. 29Si-NMR Evidence for the Role of Silicates in Alkaline Peroxide Brightening of Mechanical Pulp

The influence of hydrogen peroxide on the chemistry of aqueous silicates was investigated by high-resolution ²⁹Si-NMR and electrochemical methods. The observations indicate that dissolved silicates form labile complexes with radical H₂O₂-decomposition products, possibly O₂·^?. An important role of soluble silicates in peroxide bleaching liquors thus might be to affect the activity of free radical species which mediate H₂O₂ bleaching and decomposition reactions. Attempts to prepare the widely reported peroxysilicates from silicate/H₂O₂/NaOH mixtures resulted in the isolation of Na₂O₂·8H₂O.     

Development of new eco‐friendly options for cotton wet processing

A new approach was used to search for the optimal conditions for enzymatic scouring with an alkaline pectinase and to investigate the feasibility of performed combined bioscouring and H₂O₂ bleaching and combined bioscouring and reactive dyeing of unscoured cotton fabrics. The possibility of conducting enzymatic desizing, bioscouring, and H₂O₂ bleaching of starch‐sized cotton fabrics in a single bath was also examined. The results indicated that changes in the parameters of the bioscouring process, the types and concentrations of the treating bath components, and the sequence of the treatment and addition had pronounced effects on certain properties of the treated cotton substrates (e.g., the residual size, weight loss, wettability, yellowness and whiteness, and dyeability with reactive dyes). The optimal conditions for efficient bioscouring alone and in combination with H₂O₂ bleaching, reactive dyeing, and enzymatic desizing and H₂O₂ bleaching were determined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1825–1836, 2004     

Single stage process for desizing,scouring, and bleaching of cotton fabric

The efficiency of a treating bath formulation consisting of H₂O₂, sodium hydroxide, chelating agents, wetting agent, metal ions, and MgSO₄ · 7H₂O in effecting combined desizing, scouring, and bleaching of cotton fabric using a winch beck system was investigated under different conditions. Presence of MgSO₄ · 7H₂O at a concentration of up to 3 g/l was essential for stabilization of the strongly alkaline H₂O₂ solutions (containing 10 g/l NaOH) at 95°C for 90 min to achieve complete starch removal and to bring about fabric with satisfactory whiteness and absorbency without seriously degrading the fibre substance. Chelating agents, namely EDTA and gluconic acid (2 g/l, each) assisted in stabilization of H₂O₂ even in presence of Fe³⁺, Cu²⁺ or both ions and resulted in improved whiteness and lower fibre degradation but had no effect on residual starch or on wettability of the fabric. The wetting agent used had no significant effect on stabilization of H₂O₂ and fibre degradation, but it helped starch removal and improved the wettability of the fabric. The decomposition of H₂O₂ increased by increasing its own concentration from 2 to 12 ml/l as well as the concentration of sodium hydroxide from 5 to 17.5 g/l. The same hold true for temperature (60 to 98°C) and duration (30 to 150 minutes). Combined desizing, scouring, and bleaching of loomstate cotton fabric could successfully be effected by using a treating bath consisting of sodium hydroxide (10 g/l), H₂O₂ (4 ml/l), MgSO₄ · 7H₂O (3 g/l), EDTA (2 g/l), gluconic acid (2 g/l), anionic/nonionic wetting agent (1.5 g/l) at 95°C for 90 min, and a material : liquor ratio of 1 : 25.     

Advanced oxidation processes for wastewater treatment: Optimization of UV/H2O2 process through a statistical technique

Optimization of UV/H₂O₂ process for integration with biological waste treatment unit was done by Taguchi's orthogonal design. Four factors were considered for optimization: Dosage of H₂O₂, pH, circulation rate and number of doses of oxidant. For each of the four factors, experiments were run at four levels. For reduction in TOC, single dosage of hydrogen peroxide was observed to be more effective than dosing the same quantity in 2, 4 or 6 equal parts. The effect of circulation rate was found to be insignificant. If AOP were to be designed as a pretreatment step before biological oxidation, 1 mole H₂O₂/mole TOC is the optimum level of dosage. This level of addition increased biodegradability. If AOP were to be designed as a post-treatment step after biological oxidation, then 4 mole H₂O₂/mole TOC would be the optimum level of dosage. At this level, decrease in TOC was high. Higher pH of the waste liquor generally favoured reduction in TOC.     

Epoxidation of allyl alcohol with hydrogen peroxide over titanium silicalite TS‐2 catalyst

The influence of the technological parameters on the course of the epoxidation of allyl alcohol with 30% H₂O₂ in the presence of titanium silicalite TS‐2 catalyst and methanol as a solvent was studied. The process was performed in an autoclave at the autogenic pressure. The influence of temperature in the range 20–120 °C, molar ratio of allyl alcohol/H₂O₂ (1:1–10:1), methanol concentration in the reaction mixture (10–80% w/w), catalyst TS‐2 concentration (0.1–2.0% w/w) and reaction time (1–8 h) were investigated. The functions describing the process were: selectivity of transformation to glycidocidol in relation to allyl alcohol consumed, selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed, conversions of allyl alcohol and hydrogen peroxide. Copyright © 2007 Society of Chemical Industry     

Laccases to Improve the Whiteness in a Conventional Bleaching of Cotton

This study reports for the first time on the enhancement of the bleaching effect achieved on cotton using laccase enzyme. Laccases applied in short‐time batchwise or pad‐dry processes prior to conventional peroxide bleaching, improved the end fabric whiteness. The whiteness level reached in the combined enzymatic/peroxide process was comparable to the whiteness in two consecutive peroxide bleaches.

Effect of 10 min laccase pre‐treatment at 60 °C, pH 5 on fabrics whiteness before and after a conventional hydrogen peroxide bleaching.     

Impact of impregnation and bleaching on the surface hardness of oak (Quercus petraea L.) wood

The impact of impregnation and bleaching on the hardness of varnish layers on oak (Quercus petraea L.) wood was investigated. A number of solutions [sodium hydroxide (NaOH) and hydrogen peroxide (H₂O₂); NaOH, calcium hydroxide, and H₂O₂; NaOH, magnesium sulfate, and H₂O₂; sodium bisulfate and H₂C₂O₄ · 2H₂; sodium silicate and H₂O₂; and potassium permanganate, sodium bisulfate, and H₂O₂] were applied at a concentration of 18% to bleach both impregnated [Tanalith‐CBC (T‐CBC) or Imersol‐WR 2000 (I‐WR 2000)] and unimpregnated (natural) wood panels. Subsequently, a water‐based varnish (WB) was coated over the samples, and the hardness of the varnished layers was determined in accordance with ASTM D 4366. Among the samples that were varnish‐coated without bleaching, T‐CBC/WB yielded the highest hardness (59.50), whereas I‐WR 2000/WB exhibited the lowest (49.17). However, among the samples varnish‐coated after bleaching, the highest (56.50) and lowest (40.83) varnish hardness values were obtained with T‐CBC/solution 2/WB and I‐WR 2000/solution 4/WB, respectively. All the chemicals used for the bleaching process reduced the surface hardness. However, after the varnish coating, except for solutions 4 and 6, all the solutions showed hardness values similar to those of varnish‐coated natural (control) samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 498–504, 2004