Bleaching Process Research Articles

Fabrication of coconut dregs residue derived nano-cellulose film for food packaging

To replace conventional plastic as food packaging, several studies related to the preparation of cellulose films from various types of biomass have been reported. However, there have been no reports regarding the use of coconut dregs residue as source of cellulose for the fabrication of cellulose films. This is the first report on the fabrication of cellulose film from coconut dregs under various conditions. The purpose of this work was to investigate the effect of hydrochloric acid, and ultrasonication during the isolation process of cellulose from coconut dregs on the characteristic of cellulose film produced. Hydrochloric acid was used in the hydrolysis process and the concentrations used were 3 M, 5 M, and 7 M. The ultrasonication process was performed after the bleaching process of cellulose isolation. Cellulose films were prepared from ultrasonicated isolated cellulose particles prepared with different hydrochloric acid concentrations and compared with cellulose films obtained from isolated cellulose without the ultrasonication process. Results showed the higher hydrochloric acid concentration the lower particle size of cellulose produced. The cellulose particle size decreased after ultrasonication treatment and cellulose obtained using hydrochloric acid 7 M became nano-size cellulose particles after the ultrasonication process. These results influence the film properties obtained from these cellulose particles, where the lower the particle size the more transparent the film produced. The most transparent film was produced from cellulose particles isolated using hydrochloric acid 7 M in combination with the ultrasonication process. Furthermore, hydrochloric acid concentration and ultrasonication also influenced the tensile strength, crystallinity, and thermal stability of the films.

A Comprehensive Investigation of Woolenization Process Effect on Jute Yarn Quality

Jute, a renowned biodegradable and sustainable textile fibre, plays a pivotal role in environmentally conscious textile production. The purpose of this study was to investigate the effects of the woolenization process on the qualitative attributes of jute yarn, such as yarn evenness, and tensile and functional properties, with a special focus on the development of wool-like properties. Yarn samples were meticulously prepared from white jute fibre, categorized into three distinct count groups (C8, C10, and C12), and subjected to four treatment categories: untreated (U), woolenized (W), bleached (B), and dyed (D). The results showed that the woolenization process impoverished yarn evenness, with a significant 15.2% increase in CVm for WC8, 74% and 88.6% increase in Thin (-50%)/Km and Thick (+50%)/Km, respectively, for WC10. For tensile properties, a 27% reduction in tenacity and 176.5% remarkable elongation improvement were noted for samples WC10 and WC12, respectively. Furthermore, the development of wool-like properties was noteworthy in functional properties, including a 38.8% increase in Specific Volume Index (SVI), and a 12.8% reduction in moisture content was marked for WC8. The woolenization process also had an adverse effect on jute yarn count and quality ratio, with a deterioration of 12.5% and 32.2% marked for sample WC10, respectively. The results suggest that the bleaching process performed after woolenization negatively impacts yarn evenness. However, dyeing after woolenization and bleaching can enhance overall yarn quality. The outcome of this study will promote the use of natural fibre, and jute over synthetic and natural wool fibres.

Reactivation of used bentonite (Spent Bleaching Earth) and its reuse as adsorbent for CPO (Crude Palm Oil) bleaching process

Used bentonite or spent bleaching earth (SBE) is one of agro-industrial solid wastes in palm oil bleaching process. SBE has potential to be reactivated and reuse as adsorbent of crude palm oil (CPO). Reusing reactivated SBE is an effort to utilize waste so that it can increase added value while also preventing environmental damage due to waste accumulation. This study aimed to determine the effect of repeated use of reactivated SBE as adsorbent in the CPO bleaching process. The research methods consisted of 4 stages: characterization, reactivation of SBE and CPO bleaching process, then analysis of bleached oil, and cost analysis of the process. This study used two different types of SBE whose oil content had previously been recovered. Repetitive use of both SBE samples affected the quality of bleached oil. Maximum repetitive use that could be received by using SBE samples A was at fourth level and B was at the second level. Costs analysis of reactivation and two times repeated use of SBE was higher than fresh bleaching earth (FBE) purchase with equivalent amount for bleaching process. However, reactivation and reuse of SBE could increase the added value of the waste and prevent negative impacts on the environment.

Extraction of Cellulose from Corn Tassel Using Alkaline Pretreatment and Bleaching Process

This study explores the extraction of cellulose from corn tassels using an alkaline pretreatment followed by a bleaching process, aiming to address the challenge of non-biodegradable microbead production. The process involved the delignification of corn tassels using a sodium hydroxide (NaOH) solution, followed by bleaching with a combination of NaOH and acetic acid. The cellulose was then characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TGA). The results showed that the alkaline treatment effectively removed hemicellulose, lignin, and other impurities, enhancing the cellulose content and altering its structural and thermal properties. The extracted cellulose exhibited a crystallinity index of 44.97%, with a higher amorphous content of 55.03%, indicating the presence of disordered materials. TGA analysis revealed that the cellulose underwent two-step thermal decomposition, with a primary stage between 46.75°C and 349.02°C, and a secondary phase from 396.82°C to 697.43°C. The study demonstrates that corn tassels, often regarded as agricultural waste, can be effectively utilized to extract cellulose, offering a sustainable alternative for applications requiring biodegradable materials.

Morphology and structure of sawdust waste after adding magnetic nanoparticles

Sengon (Albizia chinensis) is a type of forest plant that grows quickly and is widely used to meet human needs. The large number of uses of Sengon wood causes sengon wood waste, such as sawdust, to increase. The study’s aim is to analyze the morphology and structure of sawdust waste after adding magnetic (Fe3O4) nanoparticles. The methods include collecting sawdust waste from wood (Sengon) was conducted by the crushing process to get smaller sawdust sizes. Alkalization was applied to sawdust and followed by a bleaching process. The powder is then immersed in a solution containing magnetic (Fe3O4) nanoparticles of 10wt%, and then dried. Sawdust composite powder the analyzed using X-ray diffraction and electron microscope instruments. The result indicates that magnetic nanoparticles deposit on sawdust powder and then make the powder become rougher. Higher content of magnetic nanoparticles causes higher agglomeration. The diffraction pattern with 2θ of 14, 16, and 22 indicates that the structure of sawdust is cellulose 1β. The degree of crystalline of sawdust powder reduces from 76.1% to 73.3% after adding magnetic nanoparticle. In the future, these composite powder results will develop as flocculants for wastewater treatment.

Reactivated Spent Bleaching Earth as a New Path in Waste Resource Utilization for the Crude Palm Oil Bleaching Process

The palm oil refining process usually uses adsorbents. The commonly used adsorbent is Bleaching Earth. However, this raises a new problem: hazardous waste in the refining process, namely Spent Bleaching Earth (SBE). For this reason, one of which is the utilization of SBE as an adsorbent through a reactivation process. This study aims to determine the characterization of RBE produced from the microwave reactivation process and acid solution as an adsorbent in the palm oil (CPO) bleaching process. The SBE reactivation process was carried out using microwaves and sulphate acid solution at concentrations 3N. RBE characteristics were analyzed using Scanning Electron Microscopy - energy dispersive X-ray spectroscopy (SEM-EDS) and Brunner Emmet Teller (BET) - Barrett-Joyner-Halenda (BJH). The resulting RBE characteristics include surface area, pore volume, and pore size of 436,820 m2/g, 0.544 cc/g, and 2.488 nm, respectively. Patricelli model is more appropriate to use to explain the mechanism of the SBE desorption process using the MAE method with the coefficient of determination value of 0.9931. The palm oil adsorbed using RBE has 10R/20Y/0.9W of color quality, 3.93% free fatty acid number, and 11.61 meq O2/kg peroxide number. In this study, SBE was successfully converted into RBE by microwave reactivation process, and the excellent performance of RBE in palm oil bleaching was verified. This research not only helps to solve the environmental problems in the process of palm oil refining but also provides a new way for waste resource utilization.

The Influence of the Used Bleaching Earth on the Content of Natural Dyes in Hemp (Cannabis sativa L.) Oils

Cold-pressed hemp oils are characterized by an intense color, which is undesirable when used directly. Therefore, research was undertaken on removing chlorophyll and carotenoids effectively. This publication presents the results of tests that verified the adsorption properties of seven bleaching earths (BE1–BE7) in two doses (2.5% and 5.0%) in the low-temperature bleaching process of hemp oils. These oils were obtained by cold and hot pressing of the seeds of three varieties of hemp (Cannabis sativa L.): Finola, Earlina 8FC, and Secuieni Jubileu. The color change and the content of carotenoid and chlorophyll pigments in the bleached oils were verified using the colorimetric method (CIE-Lab). The BEs used had different abilities to reduce the content of natural dyes connected with oil decolorization. The conducted research allowed us to characterize the influence of BEs on the organoleptic properties of the tested oils. Hemp oil obtained from the Secuieni Jubileu CP and HP hemp variety should be bleached with unmodified magnesian bentonite at 2.5%. Unmodified attapulgite clay is not recommended for this variety, as it strongly adsorbs carotenoids from the oil.

Application of Activated Rice Husk for Adsorptive Bleaching of Groundnut Oil: Kinetic, Equilibrium and Thermodynamic Study

Kinetic, equilibrium and, thermodynamic studies of the bleaching of crude groundnut oil at optimized conditions were carried out using activated rice husk as an adsorbent for the bleaching process. The efficiency of bleaching was estimated by measuring the absorbance using a double- beam spectrophotometer at a wavelength of 450nm. The effects of adsorbent dosage, bleaching temperature and, contact time on the bleaching efficiency were studied. A directly proportional relationship was found between dosage and contact time and the bleaching efficiency while a bell curve was discovered for temperature increase. The surface area of the rice husk increased from
 150.32 to 1450.32 m2/g while the pore volume decreased from 0.15524 to 0.12844 cm3/g after activation which was determined via a Brunauer-Emmet-Teller (BET) analysis and the results further validated by the Scanning Electron Microscopy (SEM) images obtained. The kinetic data of the bleaching process were best described by the pseudo-second order kinetic model while the equilibrium adsorption isotherm analysis showed that the results from the Temkin isotherm were the most significant. The thermodynamic study revealed that the adsorptive bleaching process is feasible, spontaneous and, exothermic with a decrease in entropy. The enthalpy value also showed that the adsorption process is predominantly physisorption. This study has revealed that an effective adsorbent can be produced from rice husks under optimized process conditions.

Effects of Hair Dying by Used-up Coffee Grounds Extract (CGE)

Purpose: This study aimed to examine the effects of hair dyeing employing used-up coffee grounds extract (CGE).Methods: The total polyphenol concentration of CGE was analyzed using the Folin─Ciocalteu’s method, and a shampoo formulation was prepared by adding different CGE concentrations. The hair dyeing effectiveness was observed according to changes in these two variables: dyeing concentration and dyeing time. To investigate the dyeing effects, L<sup>*</sup> (Lightness), a<sup>*</sup> (Red─Green), and b<sup>*</sup> (Yellow─Blue) values were measured using a colorimeter. The optical density value was measured to examine the hair’s fading degree after bleaching.Results: The total polyphenol concentration in CGE was 122─133 mg GAE/g. The samples showed significant dyeing effects before and after application in terms of L<sup>*</sup>, a<sup>*</sup>, and b<sup>*</sup> values. Hair dyeing ability increased with both amplified CGE concentration and dyeing time. Regarding the bleaching process, no decrease in hair colour intensity or change in hair’s fading degree was observed for 21 days.Conclusion: The possibility of dyeing using CGE has been demonstrated, and further commercialization as a shampoo formulation is considered possible.

ISOLATION OF CELLULOSE FROM SIWALAN FIBER (BORASSUS FLABELLIFER L.) USING RESPONSE SURFACE METHODOLOGY

Objective: This study investigated the isolation of α-cellulose powder from siwalan fibers (Borassus flabellifer L.).
 Methods: The methods include delignification using 10% NaOH, and bleaching using 10% NaOCl. The present research used response surface methodology (RSM) to investigate the impact of temperature and duration on the bleaching process. Two factors were evaluated and optimized using the central composite design (CCD).
 Results: The findings revealed that the hit quality and white degree were 91.5% and 52.58% when the temperature and time of bleaching were 40 °C and 30 min, respectively. Utilizing an analysis of variance (ANOVA), the most influential factors on the percentage of strike quality and whiteness degree were identified. Absorption at 3323.34 cm-1 for O-H, 2893.22 cm-1 for C-H, 1371.38 cm-1 for C-O-H, and 1157.28 cm-1 for C-O, according to FTIR characterization results, are characteristic cellulose peaks.
 Conclusion: The cellulose characterization results acquired in this work show that the temperature in the bleaching process has a significant effect on the cellulose isolation results.

Analysing the Impact of the Bleaching Process on Wet Spun Hemp Yarn Properties

Historically, cotton has been regarded as a highly sustainable material; however, thorough research indicates otherwise. The increasing levels of pollution and the need to address climate change have led towards a global search for sustainable alternatives. Plants with comparable chemical compositions, such as hemp, are attracting growing attention. The cultivation of hemp can be done with sustainable methods, thereby making it a viable alternative to cotton. This study investigates the mechanical, physical, and dyeing properties of 100% wet-spun hemp yarn in its natural and bleached state with the objective of incorporating its use in both technical and traditional textiles. Although significant academic literature is available on the properties of cotton, there is a noticeable lack of literature based on wet-spun hemp. This research suggests that the bleaching process positively affects wet-spun hemp yarn, thus making it suitable for use by the textile industries in various applications.

Decay resistance and moisture absorption of transparent wood composite

ABSTRACT Transparent wood composite (TWC) is a novel wood-based polymer composite that combines high optical transmittance (more than 80%) with good mechanical and thermal properties. It offers numerous potential areas of applications, including smart windows, energy-efficient elements, display panels, light diffusers and substrates for solar cells. The sensitivity of TWC towards moisture and biological agents such as fungus becomes important for certain applications. In this study, TWCs were prepared using wood veneers of Populus deltoides (poplar) and Melia dubia (melia) through the process of lignin-modification bleaching and epoxy-resin infiltration. Water-absorption studies were carried out by immersing TWC specimens in deionized water for a duration of 400 h and by exposing specimens to different relative humidity (RH) conditions. The fungal resistance was evaluated by exposing specimens to a brown rot (Oligoporous placentus) and a white rot (Trametes hirsutu) fungus. Results indicated that TWC can absorb a maximum of 8% to 10% of water during a water immersion test for a period of 400 h. Exposing TWC specimens to different RH conditions resulted in no significant moisture adsorption. TWC was highly resistant to white rot and brown rot fungus.

Optimization of canola meal bleaching by hydrogen peroxide, protein extraction and characterization of their functional properties

The aim of the present work was to study the optimization of a process of canola meal bleaching with hydrogen peroxide. Effect of the bleaching on crude proteins extractability, their emulsifying and foaming properties were evaluated. The obtained results showed that hydrogen peroxide was highly effective for canola meal bleaching and its chromatic parameters were significantly improved. The bleached canola meal reached values of L* = 83.46, a* = −3.66, b* = 17.18 and BI = 18.05, making it compatible with commercial flours such as oat, rye, and whole wheat pastry flours. Protein extractability from the bleached meal was significantly enhanced up to 90 %. The functional properties evaluation of the extracted proteins from the bleached meal showed highly improved emulsifying and foaming properties. The extracted proteins from the bleached meal were mixed with canola oil and the analysis of the peroxide index did not show any oxidizing effect.

Effect of Chemical Pre-treatment on Screen Printed Fabric Performance Properties

Printing is the process of transferring a specific pattern or design onto the surface of textile fabric. In the printing process, screen printing is one of the fundamental printing methods on textiles and is widely used worldwide. However, screen-printed fabrics have specific properties like fastness, water absorbency, and whiteness index that increase the end-use properties of the printed fabrics. There are several factors that affect the technical characteristics of printed fabrics. This research focuses on an experimental approach to ascertain and confirm the pre-treatment process as one of the most important factors in pigment dye screen-printed fabrics. The main raw material used in this research was 100% cotton fabric with a plain weave structure. The experimental method used in this research involved the pre-treatment (singeing, scouring, and bleaching) process with different recipes and four samples. Screen-printed fabric after printing was tested for its technical properties using standard test methods. The results of a one-way ANOVA (Analysis of Variance) were analysed using MINITAB and Microsoft (MS) Excel software. The results indicate superior fabric technical properties like color fastness to rubbing and washing, coupled with improved water absorbency and excellent whiteness index values of samples printed after bleaching with Hydrogen Peroxide (H2O2). In this research, we conclude that printed fabric after bleaching with H2O2 has the best color fastness, and bleaching with NaOCl is the next one. However, printed fabric has a low fastness property after scouring and singeing.

Influence of Cotton Bleaching Methods on the Parameters of Generated Textile Industrial Wastewater

The environmental impact of industrial wastewater after bleaching requires special attention to prevent the pollution of aquatic ecosystems. The aim of this study was to compare the effluent parameters obtained after using a traditional bleaching method and an alternative enzymatic bleaching method in order to assess their possible environmental impacts. In the classical bleaching method, NaOH and H2O2 were used, and in the alternative method, pectinase enzyme, H2O2, and sodium carbonate were used as the bleaching agents. The bleaching process was designed by determining the optimum amount of pectinase enzyme, the optimum temperature, and the optimum amount of peroxide. The whiteness of the treated cotton yarns was also evaluated. The different bleaching processes were analyzed and evaluated in terms of the wastewater discharged, the pH, chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS), and conductivity. These data show that the use of the pectinase enzyme allows us to obtain much lower COD and TSS values compared to those obtained using traditional bleaching. At the same time, the use of the proposed enzymatic bleaching method reduces the environmental impact since lower concentrations of pollutants are obtained in the effluent. Therefore, the pretreatment of wastewater may require the selection of a simpler and more environmentally friendly technology, such as enzymatic bleaching.

New insights into the on-site monitoring of probiotics eDNA using biosensing technology for heat-stress relieving in coral reefs

Coral probiotics can improve the tolerance of corals to heat stress, thus mitigating the process of coral thermal bleaching. Sensitive and specific detection of coral probiotics at low abundances is highly desirable but remains challenging, especially for rapid and on-site detection of coral probiotics. Since the electrochemical biosensor has been recently used in the field of environmental DNA (eDNA) detection, herein, an efficient electrochemical biosensor was developed based on CoS2/CoSe2-NC HNCs electrode material with a specific DNA probe for the C. marina detection. After optimization, the lower limit of detection (LOD) values of such biosensors for the target DNA and genomic DNA were 1.58 fM and 6.5 pM, respectively. On this basis, a portable device was constructed for the practical detection of C. marina eDNA, and its reliability and accuracy were verified by comparison with the ddPCR method (P > 0.05). For each analysis, the average cost was only ∼ $1.08 and could be completed within 100 min with reliable sensitivity and specificity. Overall, the biosensor could reflect the protective effect of probiotics on coral heat stress, and the proposed technique will put new insights into the rapid and on-site detection of coral probiotics to assist corals against global warming.

Thermo-alkali stable bacterial xylanase for deinking of copier paper

BackgroundThe bleach-boosting capability of xylanases is well-known. The use of xylanase pre-treatment before the application of chemical bleach has multiple advantages including (i) lesser use of polluting chemicals of the traditional bleaching process; (ii) less damage to the cellulosic fibers, therefore better recyclability; and (iii) better brightness of chemical bleach. The major impediment in the application is the availability of commercial enzymes that are active at the elevated temperature and pH that exist during the industrial pulping process. In the present paper, xylanase having suitability for application in deinking is reported. ResultsThe xylanase used showed high deinking potential. Optimal deinking was obtained at the xylanase dosing of 20U/g of the dried pulp at 60℃ for a treatment time of 1h. It could bring about a 50% reduction in the usage of chemical bleach that was applied after xylanase pre-treatment. The comparison of FTIR spectra showed changes in intensity without significant changes in the functional group signatures implying that there is negligible damage to the fiber strength in the xylanase pre-treatment process as compared to the chemical bleach process. ConclusionThe xylanase used in this study was effective in deinking paper pulp and can be used for bio-bleaching of recycled paper.

Surface morphology engineering of WO3 films for increasing Li ion insertion area in electrochromic supercapacitors (ECSCs)

Two different dry deposition methods were used to deposit electrode films with different surface morphologies in relation to the performance of electrochromic supercapacitors (ECSCs): direct current (DC) magnetron sputtering and the nanoparticle deposition system (NPDS). The NPDS method, which sprays powders onto the substrate using pressure differences, deposited WO3 film with its roughness of 36 nm and its thickness of 383 nm, while the sputtered WO3 film had its roughness of 3 nm and its thickness of 262 nm. Due to its dramatic difference in surface roughness, the NPDS-WO3 thin film had larger reaction surface area as well as Li-ion diffusion coefficient than those of sputtered-WO3 films. As a result, the ECSC device with NPDS-WO3 exhibited 19 % higher coloration efficiency with greater charge capacity compared to those with sputtered-WO3. However, the ECSC device with NPDS-WO3 showed different charge/discharge with trapped Li ions during the coloring(charging)/bleaching(discharge) processes respectively, leading to rapid degradation of the device. This research highlights the clear difference between its characteristics of the thin films fabricated using the NPDS vs. sputtering methods in relation to its surface roughness so that this study would be potentially beneficial in engineering various properties of ECSC devices.

Characterization of Cellulose Fiber Derived from Hemp and Polyvinyl Alcohol-Based Composite Hydrogel as a Scaffold Material.

Cellulose nanocrystals (CNCs) were successfully extracted and purified from hemp using an alkaline treatment and bleaching process and subsequently used in conjunction with polyvinyl alcohol to form a composite hydrogel. Cellulose nanocrystals (1-10% (w/v)) were integrated into polyvinyl alcohol, and sodium tetraborate (borax) was employed as a crosslinking agent. Due to the small number of cellulose nanocrystals, no significant peak change was observed in the FT-IR spectra compared to pristine polyvinyl alcohol. The porosity was created upon the removal of the water molecules, and the material was thermally stable up to 200 °C. With the presence of cellulose nanocrystals, the melting temperature was slightly shifted to a higher temperature, while the glass transition temperature remained practically unchanged. The swelling behavior was examined for 180 min in deionized water and PBS solution (pH 7.4) at 37 °C. The degree of swelling of the composite with cellulose nanocrystals was found to be higher than that of pristine PVA hydrogel. The cell viability (%) of the prepared hydrogel with different proportions of cellulose nanocrystals was higher than that of pristine PVA hydrogel. Based on the results, the prepared composite hydrogels from cellulose nanocrystals extracted from hemp and polyvinyl alcohol were revealed to be an excellent candidate for scaffold material for medical usage.

Efficient and sustainable bleaching of cotton/spandex integrating UVA radiation and peroxide activator: A study focus on the degradation mechanism of natural pigments in fibres

Establishing an energy/water-saving bleaching process is highly expected by textile plants to reduce industrial carbon emission, wastewater discharge and general cost. Therefore, an efficient UVA-assisted N-[4-(triethylammoniomethyl)-benzoyl]- caprolactam-chloride (TBCC) -activated hydrogen peroxide (H2O2) bleaching strategy at ambient temperature for cotton/spandex (C/S) fabric was developed in this study. Results reveal that 7.4 g/L of TBCC-activated H2O2 (30%) achieves a slightly higher whiteness index (WI) on C/S fabrics than those only treated with 60 g/L H2O2 (30%). The treated C/S fabric displays a good dyeability using direct dyes due to the qualified wettability. The mild pH process protects C/S fabrics from damage with a low tensile loss (less than 10%) in warp and weft directions. The WI of C/S fabric mainly depends on the concentration of TBCC/H2O2 couple and radiation time. Moreover, the degradation mechanism of cotton pigment in UVA/TBCC/H2O2 bleaching system was implemented including the identification of effective reactive oxygen species (ROS), tracking of the concentration variation of hydroxyl radical (HO•) under UVA irradiation, and the exploration of degrading kinetics and pathway of morin as the model of pigment impurity. Indicated by the degradation rate constant, both TBCC and UVA plays an accelerating role in enhancing the degradation efficiency. In the radical scavenging experiment, HO• and superoxide radical (O2–•) are two major ROS participating in the degradation. And therein, HO• makes larger contribution than O2–•. HO• concentration has a high positive correlation with radiation duration and TBCC dosage based on the fluorescence labelling method. Confirmed by LC-MS/MS analyses, 2,4,6-trihydroxybenzoic acid (MW: 170.12) and 2,4,-dihydroxybenzoic acid (MW: 154.12) are two major segments degraded from the oxidation and ring-opening of C-ring in morin. Finally, considering energy, water and chemical conservations, the condition i.e. 7.4 g/L of H2O2 (30%) and 20 g/L of TBCC under 30 W UVA radiation for 1 h, is recommended, which significantly increases the WI by 46.5%, and saves about 90% energy and 50% water consumption compared with the conventional waterbath bleaching at 95 °C for 45 min when similar WI enhancement was achieved.