The color of wood is the same as the texture, strength and density of wood. It is an important indicator to evaluate the quality of wood and determine its value [3] . Wood bleaching is a processing process that uses chemicals to make solid wood, veneer, wood chips, wood pulp lighter, uniform in color, and eliminates pollution. It is an important processing link for solid wood products, wood-based panel decoration, pulp and paper, and man-made fibers. An important component of the production of advanced wood-based panels, paper and man-made fibers. Due to the continued strong development of the wood industry, the paper industry and the man-made fiber industry, wood bleaching has received much attention and a large number of new technologies for wood bleaching have emerged.  1 Basic principles of wood bleaching and common pharmaceuticals The main components of the wood cell wall are cellulose, hemicellulose and lignin. Cellulose and hemicellulose do not absorb visible light, and lignin which is present as a matrix in cellulose microfibers is the main coloring substance, and its basic structural unit is phenylpropanyl, in which benzene rings, anthraquinones and The carbonyl group (>C=O) and the carboxyl group (-C=O-OH) of the monomer side chain all contain carbon-oxygen (C=O) and carbon-carbon (C=C) conjugated double bond structures. Color groups are an important source of wood color. In addition, a large amount of hydroxyl groups (-OH) and methoxy groups (-OCH3) present in the wood component, although colorless by themselves, are highly susceptible to degradation under the action of light (especially ultraviolet light) and oxygen, making wood Darker tones, a potential chromophoric group known as a color-promoting group. The bleaching process of wood is to use chemical agents to oxidize and reduce the surface of wood, and to destroy the CM (21) color group (such as C=C, C=O) or closed color-assisting group that can absorb visible light in wood. Such as -OH), it produces whitening and decolorization. The chemical agents used can be classified into two types, oxidized and reduced (see Table 1) [4] . 2 Bleaching agent selection The ideal bleaching effect is to remove the colored material while minimizing damage to the surface. When the coloring matter can be extracted with a solvent, it is preferable to use a solvent extraction method; when the solvent cannot be extracted, a method of decomposing the coloring substance can be used; when the decomposition is difficult, the coloring substance should be changed. Sexual approach [4]. The methods of decomposition and modification include oxidation method, reduction method, methylation method, acetylation method, etc. No matter which method is used, in principle, the best possible bleaching effect is obtained with as few agents as possible, that is, Maximize the role of bleach and reduce the gain. Wood is a kind of natural material. The color of the material is variability inside and outside the plant. When choosing bleaching agent, it is not only necessary to be based on the color and color of the material, but also the ease of bleaching treatment. The price and dosage of the drug should be as low as possible, whether the drug is harmful to the human body, whether it is polluted by the environment, etc. [4] . 3 Mechanism of wood bleaching 3.1 white rot fungus bleach mechanism  Under suitable conditions, Phanerochaete chrysosporium, Forces annosus, Ganderma ostale, Panus conchatus, Phlebia radiata The hyphae of white rot fungi such as Tranzetes versicolor, Cythus stererreus, white rot fungus IZU-154, Pleurotus ostreatus begin to grow, hyphae grow During the process of spreading, a large amount of extracellular oxidase is secreted. Among them, the key two types of peroxidases, LiP and MnP, rely on the formation of H2O2, which triggers the initiation of a series of free radical chain reactions. The benzene ring in the prime structure undergoes a single electron oxidation reaction to form a cationic group, and then undergoes a series of spontaneous reactions to degrade. These degradation processes include the removal of methoxy groups, the Cα-Cβ bond, the Cβ-Cγ bond, and the cleavage of the alkyl aryl ether bond until ring-opening cleavage of the benzene ring. The degradation products of lignin are then absorbed by the mycelium and eventually oxidized to carbon dioxide and water [5] . At present, white rot fungi have not been industrialized for pulp bleaching, and laboratory research has been ongoing. Obviously, once the action time of white rot fungus bleached pulp is shortened and other problems are properly solved, white rot fungus bleached pulp will eventually be industrialized [5] . 3.2 Electrochemical bleaching mechanism In recent years, in the study of pulp bleaching, electrochemical bleaching has gradually attracted the attention of researchers. The basic principle of electrochemical bleaching is to bleach the pulp by the action of a current to produce a bleaching chemical. Three electrochemical bleaching mechanisms are described here: electrochemical chlorine bleaching, electrochemical oxygen bleaching and electrochemical hydrogen peroxide bleaching.  (1) Electrochemical chlorine bleaching. In electrochemical chlorine bleaching, a chemical reaction with bleaching is produced according to the following electrochemical reaction: Anode reaction: 2CI-→ CI2+2e Cathodic reaction: 6H++ 6e→ 3H2 Liquid phase reaction: 3CI2+ 6H2O→ Cl2, HClO, ClO-, and ClO3- in the solution cause lignin to be chlorinated and oxidized almost simultaneously [6-8] .  (2) Electrochemical oxygen bleaching. Oxygen bleaching is recognized as a bleaching technique that is environmentally friendly. The kinetics and mechanism of oxygen bleaching have attracted the attention of many scientists [9-11] . Perng et al [12] believe that the oxygen bleaching mechanism under the action of current can be expressed as the following chain reaction: Chain trigger: Anode reaction: M(n-1)+→ Mn+ Chain growth: Chain termination: L stands for lignin and M stands for transition metal  In recent years, electrochemical oxygen bleaching of wood pulp has received extensive attention, but research on grass pulp has rarely been reported. Especially for the large straw country in China, the electrochemical bleaching research of straw pulp is of great significance.  (3) Electrochemical hydrogen peroxide bleaching. Under electrochemical conditions, hydrogen peroxide can be directly produced by the following electrode reactions [13, 14] : H2O2 is one of the main chemical reagents for chlorine-free bleaching (ECF) and total chlorine-free bleaching (TCF) processes. Reducing the production cost of hydrogen peroxide is the key to the price of ECF and TCF pulp to compete with chlorine bleached pulp. At present, the H2O2 used for bleaching in the factory is mainly produced by multi-step treatment after hydroquinone is auto-oxidized, and the production process is complicated and the cost is high. According to Mathur et al. [14] , the hydrogen peroxide produced by electrochemical method is about 15% lower than the current H2O2, which has certain application prospects.  3.3 Mechanism of Oxidative Bleaching Chlorine bleaching waste liquids contain toxic substances such as chloroform and dioxins and carcinogens [15] . Therefore, the bleaching mechanism of hydrogen peroxide is taken as an example to discuss the oxidative bleaching mechanism. Hydrogen peroxide decomposes to form free radical HOO·, O-, HO2- attacking pigment conjugated system, participates in oxidative bleaching, changes the structure and quantity of chromophore groups, and thus achieves the result of decolorization [16~18] . The chain termination reaction caused by free radicals is as follows: 3.4 reduction bleaching mechanism Here, the reduction bleaching mechanism is illustrated by taking only the bleaching mechanism of sulfur dioxide as an example. The principle of bleaching of sulfur dioxide is mainly: sulfur dioxide can combine with certain colored substances to form unstable colorless substances, thereby achieving the purpose of bleaching, and the colorless substances are easily decomposed by heat to restore the colored materials to their original colors. If SO2 is passed into a slightly acidic magenta solution, the magenta solution fades. There is a chromophore in the structure of magenta. When the chromophore encounters sulfurous acid, it forms an unstable colorless compound and changes the structure of the chromophore. This colorless compound is unstable and decomposes when exposed to heat. For the chromophore [19] .  3.5 Activated carbon bleaching mechanism Activated carbon is an allotrope of carbon. It is a powdery, granular or pellet-shaped amorphous porous carbon with strong adsorption properties. The mechanism of activated carbon bleaching is that the loose porous structure of activated carbon has adsorption activity, and the pigment in the active substance is removed, thereby achieving the purpose of bleaching, and the process is a physical process without chemical reaction [19] .  3.6 Toner bleaching mechanism It can be seen from the hue diagram that the adjacent two primary colors of the three primary colors are matched to obtain a color. Two kinds of inter-colors can be matched to obtain a complex color. The relative hue also has the effect of mutually absorbing the reflected spectrum. For example, in a bleaching paste with a light yellow color and a low lignin content, a blue-violet or red-blue dye is added to absorb the pale yellow or orange spectrum at a wavelength of 500 to 600 nm, which can complement each other and allow visual observation. It reflects a higher whiteness. Under the premise of not changing the process flow, the toning method can not only achieve the whitening effect, but also improve the whiteness of the pulp, and the operation is simple and the cost is low [20] . 4 Research Status of Domestic Wood Bleaching Bleaching is one of the fastest growing and most varied technologies in the field of pulp and paper, wood processing and man-made fibers. For this reason, China's timber scientists have done a lot of work, the main results are as follows: 4.1 Applied Research In response to the phenomenon of paulownia discoloration, in 1995 Hu Weihua et al [21] selected two different formulations to test the stains. The results showed that under the same conditions, the samples treated with the oxidizing formula were superior to the reducing formula. And the orthogonal test method was used to analyze the influence of relevant factors on the decomposition rate of hydrogen peroxide in the bleaching process of Paulownia [22] , Deng Shaoping [23]漂白 The bleaching test was carried out on four commonly used decorative woods by orthogonal test to determine the concentration. The best combination of bleaching process factors such as temperature, time, pH value and auxiliary agent provides a theoretical basis for decorative wood production enterprises to solve the problem of wood bleaching. Li Niancun et al. [3] introduced a new type of bleaching agent, and discussed the formulation and bleaching process parameters of the bleaching agent when using the new bleaching agent. Compared with the traditional bleaching agent H2O2, the new wood bleaching agent has lower price and better bleaching effect. The operation is more convenient. Test results show that the new wood bleaching agent is well suited for wood bleaching. Wu Zhihui et al [24] studied the prototype of tooth-color craft wood fan and other products and the performance of the mass production of the product and the improvement of the traditional fan technology. The results show that the wood fan after bleaching and dehydration has small deformation, low cost and authenticity. The rate is high, and it is pointed out that the use of the fan blank of the stone wood for bleaching can be made into a high-grade and delicate ivory craft wood fan.  Yang Yonggang et al [25] focused on the oxygen-alkali bleaching process of straw ASAQ pulp, which provided a theoretical basis for the next bleaching of straw and its high whiteness and short procedure of complete chlorine-free bleaching, which is expected to be higher. The whiteness and short procedure were completely chlorine-free bleaching. At the same time, Dai Hongqi et al [26] studied the surface chemical properties of bleached wheat straw pulp. In recent years, Wang Haisong [27] and Xu Qinghua et al. [28] have studied the deinking of waste paper and the amount of lignin contained in deinked waste paper pulp, and found that only hydrogen peroxide and sodium dithionite are suitable. bleach. Huang Ganqiang [29] studied the high temperature and high pressure hydrogen peroxide bleaching technology of sulphate bamboo pulp, aiming to provide a basis for green bleaching technology. Yang et al. [30] discussed various factors affecting the bleaching of single-stage peracetic acid poplar wood pulp; Xu Teng et al [31] also studied the amount of peracetic acid bleaching solution, temperature, time and pH for bleaching in 2003. The impact and pointed out that acetic acid is an environmentally friendly chemical. Xu Ying [32] took kaolin as the research object. On the basis of determining the type and occurrence state of dyeing impurities, the whitening test was carried out by three methods: reduction bleaching, oxidative bleaching and oxidation-reduction combined bleaching. The factors affecting the bleaching effect (sample mineral composition, dosage, pH value, slurry concentration, reaction temperature, reaction time, dosing system) were studied, and the results were better in neutral alkaline environment. Bleaching effect, while avoiding acid medium corrosion production equipment.  Ying Runfen et al [33] in the real face of the fast-growing material Eyu 375 with reed, Italian poplar wood cooking bleaching comparison test, found that the fast-growing material Eyu 375 as a short fiber raw material easy to pulp, easy to bleach, pulp High whiteness, good fiber uniformity, small amount of impurities, easy to dehydrate, is conducive to papermaking, but the cost is higher than the pulp. Zhan Huaiyu et al. [34] analyzed and studied the fiber morphology, chemical composition and pulp bleaching properties of Li Wei, and found that Lishui wood is a better papermaking material. Liu Li et al [35] and Zhao Jian et al [36] studied the kraft pulping of blue dragonfly, respectively, and found that blue dragonfly has excellent pulping performance.  4.2 Research on Bleaching Aids In 2001, Yin Suhong et al [37] reported the effects of additives such as stabilizers, chelating agents and activators, and basic parameters of peroxygen bleaching on bleaching effects, and confirmed that in peroxygen bleaching, stabilizers, bleach activators, Chelating agents are essential additives. Zhang Zeng et al [38] specifically discussed the performance of the bleach activator Fe(III) for hydrogen peroxide, and obtained that the Fe(III) tetraamide macrocyclic complex activator has sufficient stability and suitable temperature. The range can effectively improve the delignification ability of H2O2 and have good delignification selectivity in the bleaching process. Recently, the United States has also developed a series of trivalent iron complex-TAML activators. The addition of this activator to hydrogen peroxide can effectively activate low-temperature hydrogen peroxide, enhance the oxidation capacity of hydrogen peroxide, and improve pulp. Whiteness, reducing production costs [15] . Jiang Maosheng et al [39] applied the gas method to study the decomposition kinetics of H2O2 under different bleaching conditions, and analyzed various factors and microscopic mechanisms affecting the decomposition of H2O2. The results show that the decomposition of H2O2 in the bleaching process is affected by CuO, Fe2O3 and MnO2. The strong catalysis, while MgSO4 and Na2SiO3 synergistically form silicate particles, can occlude harmful metal ions, produce a stabilizing effect, and reduce the inefficient decomposition of H2O2. In 2003, Li Dan et al [40] pointed out that the addition of sulfamic acid to the hypochlorite bleaching of masson pine sulfate chemical wood pulp can effectively prevent excessive degradation of fibers and significantly increase the strength of bleached pulp, thereby improving paper quality or reducing The slurry ratio of chemical wood pulp in papermaking has obvious economic benefits.  In recent years, Chen Yuhe et al [41] treated paulownia wood with dilute solution of NaOH, observed the change of permeability and color of paulownia, and studied the promoting effect of lye on the bleaching effect of paulownia wood. The results showed that the NaOH diluted solution had no obvious effect on wood color. The damage effect can significantly improve the permeability of paulownia and promote the bleaching effect of wood. Lin et al. [42] found that polyxylase can significantly increase the whiteness of pulp, reduce the amount of chemical bleaching agent and the pollution load of bleaching wastewater. However, the role of polyxylase in pulp bleaching is only to help bleach, but not Complete replacement of chemical bleaching agents cannot fundamentally eliminate the production of bleaching wastewater. Lin Youfeng et al [43] discussed the application and mechanism of urea as a cooking agent and bleaching protectant; subsequently, Tang Fenghua et al [44] pointed out that urea as a pretreatment aid for hydrogen peroxide enhanced oxygen bleaching has a better bleaching effect.  4.3 Review Study Li Jian et al [45] and Xu Yongji et al [46] respectively summarized and summarized the basic knowledge of wood bleaching and the more common methods of eliminating discoloration. Luo Jusheng [47] expounded the status quo of chemical pulp bleaching technology in China and its gap with foreign countries, analyzed the pollution sources of pulp bleaching process, and evaluated and introduced the ways to reduce pollution and the more mature and feasible technical measures. Zhang Zhongcheng et al. [48] introduced the properties and applications of various decolorants, bleaches and brighteners in detail, gave several methods for decolorization and bleaching of chemical and other products, and discussed the latest developments in the field of decolorization and bleaching. Recently, Jing Qi et al. [49] introduced the progress of preparation of bleach activators in the past 10 years, pointing out that bleach activators are compounds containing oxygen or nitrogen acyl groups, which can react with strong nucleophilic peroxyacid to produce peracetic acid, thereby improving bleaching. effect. Zhou Xuefei [50] introduced several oxygen bleach activators such as molybdate, diaminodicyanide and eye amine, potassium permanganate and their effects.  5 Research directions for wood bleaching Despite the fruitful results in wood bleaching, in the 21st century, scientists at home and abroad engaged in wood bleaching research still face new challenges. First of all, in practice, it is found that whether the bleaching of solid wood or veneer, or the bleaching of wood chips, wood pulp or cellulose is restricted by the difficulty of penetration of wood to varying degrees, resulting in insufficient bleaching depth and uneven whiteness, so in-depth While studying the permeability of wood, the development of additives such as surfactants, bleach activators, penetrants and brighteners suitable for wood bleaching should be highly valued to promote the start and development of the wood improvement industry. Once again, logs and large-scale plates are difficult to dry after being treated by conventional bleaching processes, which are prone to cracking and deformation, reduce bleaching efficiency, and also bring a large amount of bleaching wastewater. Therefore, it is necessary to develop a new bleaching process suitable for logs and large-scale plates as soon as possible to meet the improvement of the surface color of artificial logs and large-scale plates.  In addition, in recent years, chlorinated bleaching waste liquids have been found to contain toxic substances such as chloroform and dioxins and carcinogens [15] . For this reason, people have to improve the bleaching method to reduce or eliminate organic matter in bleaching waste liquid. Chloride production, but ECF and TCF bleaching costs are relatively high, the state should provide policy support, and the application of regulations to limit the application of chlorine bleaching technology. However, China is still in a backward state in this respect. Therefore, the development of pollution-free bleaching technology and the reduction of environmental pollution by bleaching wastewater are another research direction in the future [51] .
CONTUO Products presents this Manual Converter desk. Elevate your work flow. Our standing desk creates a healthy work space allowing you to balance between sitting down and standing up. The 2-tier design features a monitor tabletop and a keyboard drawer. Ergonomic and innovative, this adjustable standing desk features a smooth, gas-spring lift mechanism with 8 height settings. Raise or lower your work surface within seconds with the push levers located at both sides of the table. The spacious work surface can hold and display dual monitor setup while having space left over for pencil holders and other accessories. Take your productivity and comfort in the work place to new heights, with the Standing Desk Converter by CONTUO.
Manual Converter Desk,Office Desk Converter,Manual Standing Desk Converter,Desk Riser Converter Shaoxing contuo Transmission Technology Co.,Ltd , https://www.ctelectricdesk.com
12CIO-+ 6H2O→ 4CIO3-+ 8HCI+ 12H++ 3O2
3CIO-+ 3CI-+ 3H+HCIO→ CIO-+ H+
2HCIO+ CIO-→ CIO3-+ 2CI-+ 2H+
O2 + e-→O2-
L-+ O2→ L·+ O2-
L-+ Mn+ → L·+ M(n-1)+
L·+ O2→ L-O-O·
L-+L-O-O·→ L·+ L-O-O
L-O-O·+O2-·→ L-O-O-+O2
L-O-O-→ Degradation 
L·+ L·→L-L
Anode reaction: 4OH-→ 2H2O+ O2+ 4e-
Cathodic reaction: H2O+ O2+ 2e-→ HO2-+ OH-
Total reaction: OH-+ O2→ 2HO2-
H2O2→ HO2-+ H+
HO2· → O2-+ H+
HO· + H2O2→ H2O + HOO·
HO2· + H2O2 → H2O + O2+ HO·
HO·+ HO· → H2O2
HO· + HO2· → H2O + O2
HO2· + HO2·→ H2O2 + O2
HO2-+ not bleached → OH-+ bleached pulp
When there is no bleaching object in the solution, or when the object to be bleached is not exposed, the active oxygen released by them combines to form oxygen, which is an inefficient decomposition of hydrogen peroxide.

Secondly, as plantation wood is widely used in solid wood processing, wood-based panel secondary processing, papermaking and man-made fibers, the color of wood varies, especially the local color differences caused by knots, inclusions or various pollutants. Has been widely concerned by the processing industry [4] , so the local bleaching technology of wood has yet to be developed. However, the current bleaching technology is not targeted, and the selectivity of bleaching objects is poor, which not only causes waste of bleach, increases cost and aggravates environmental pollution, but also makes the bleaching target difficult to achieve accurately. Therefore, quantitative bleaching technology is another development direction. The basis and premise of the development of local bleaching technology for wood.  
So, here you can find all the Height Adjustable Desk for working.
CONTUO Height Adjustable Desk for office are very popular in the world.
Wood is the most intimate natural material among the three major building materials (steel, cement, wood), with high availability, regenerability and important economic value. As people's understanding of environmental protection is getting more and more profound, the trend of green consumption is rising day by day. The harm of chemical fiber to human body and the pollution of the environment have attracted the attention of governments and people of all countries, and viscose fiber, acetate fiber and lyocell fiber are deeply affected by people. Favor [1] . Pulp and paper mills are spread all over the country, and the pollution caused by pulping and bleaching is quite serious. Although the cooking black liquor can be recycled, the toxic tobacco wastewater pollution has been plagued by the paper industry [2] . Especially in the past ten years, the timber industry, the pulp and paper industry has developed strongly, and the wood suitable for wood processing and pulping has been consumed in large quantities, which has caused environmental degradation. Therefore, natural forests are widely protected by countries all over the world, making the global timber industry The supply of raw materials is gradually shifting from natural forests to plantations. The plantation grows fast, the material is early, the material is loose, the color of the material is uneven, the color is dark, and the discoloration and pollution generated by the wood during storage and processing make it suitable for furniture, papermaking, man-made fiber and floor. It is greatly restricted, which reduces the value of wood use. Therefore, the problem of material color has become an urgent problem to be solved in the wood industry, paper industry and man-made fiber industry. At present, China's planted forest area has ranked first in the world. In order to maximize the potential of plantation wood, only by thoroughly mastering the mechanisms that control its performance can these properties be changed as needed. Therefore, the development of new technology of wood bleaching can promote the formation of a green industrial chain, promote greening, rapidly increase the area covered by forests, expand urban and rural employment, and form efficient forestry, so it has significant ecological, economic and social benefits.