By: Sandriele Streit
As previously mentioned, magnesium is present in the human body, plants, soil, water and everything around us. Additionally, there are several industries that use magnesium compounds in their production processes. One of these industries is pulp and paper, which requires the application of chemicals that act as a bleaching agent. Join us as we learn about the benefits of applying magnesium hydroxide of a high purity when bleaching cellulose pulp!
Magnesium hydroxide as a sustainable bleaching agent in paper and cellulose
The pulp and paper industry is responsible for transforming wood into various solutions that meet a wide range of needs. During processing, this wood passes through several stages until it is transformed into cellulose and eventually paper.
The cellulose is extracted from wood chips, through means of mechanical and/or chemical stage that remove darkening substances, such as lignin and other metallic chromophores in order to form bleached cellulose pulp. During the bleaching steps, the cellulose pulp is subjected to the action of bleaching agents such as soda (sodium hydroxide), hydrogen peroxide and/or chlorine dioxide.
The function of these agents is to eliminate darkening substances without degrading the cellulose fibers. Soda is a bleaching agent with high alkalinity. This means that, in addition to hydrolyzing lignin and darkening substances, it also reaches cellulose fibers, degrading them and, consequently, decreasing the pulp yield.
Another agent used in the bleaching stages is hydrogen peroxide, an oxidizing agent that helps to remove lignin. However, hydrogen peroxide decomposes easily in the presence of metals and impurities, generating reactive species that damage the cellulose structure, which also causes a decrease in pulp yield. In some processes, in order to prevent the hydrogen peroxide from decomposing, magnesium sulfate is added to inactivate the metal ions.
Therefore, in a traditional cellulose bleaching process, agents that perform a bleaching or auxiliary function are added: soda, hydrogen peroxide, magnesium sulfate and chlorine dioxide. This allows a high level of whiteness to be achieved during the process, but the use of these agents leads to some challenges.
High-performance bleaching agent
One of the requirements for selecting a high-performance bleaching agent is the product’s purity. The presence of impurities and metals is of course undesirable during the processes involving the use of high purity products. The greatest advantage offered by magnesium hydroxide of a marine origin, Hidromag PC, is its high purity when compared to compounds of a mineral origin, which guarantees a bleaching process that is free of metals.
In addition to its high level of purity, Hidromag PC is also able to encapsulate other metal ions present in the process, such as iron and copper, among other metals, in order to protect the hydrogen peroxide against degradation and the generation of reactive species that damage the cellulose structure.
This allows the application of hydrogen peroxide to be optimized, reducing hydrogen peroxide residue by 31% and making it more readily available and efficient in performing its function. The performance of the bleaching action of Hidromag PC is also marked by a 23% reduction in the chlorine dioxide load used, maintaining the brightness of the pulp at 90.5% ISO.
Hidromag PC offers intermediate alkalinity, which makes it more effective and less aggressive than soda. Tests indicate that the amount of soda used in the process can be reduced by 11% and be partially replaced by magnesium hydroxide.
Magnesium hydroxide effectively interacts with lignin, degrading it without reaching the cellulose chain, thereby helping to preserve fibers. This increases viscosity, resulting in a higher yield of bleached pulp, which favors draining and efficiency throughout the remaining production stages.
Hidromag PC’s intermediate alkalinity also allows it to be classified as a non-hazardous chemical under ABNT NBR 14725-2, thereby increasing safety in operations.
The Hidromag PC is an environmentally friendly solution, since it is extracted in an synergistic manner in which Bel Mag is able to sustainably harness natural resources. Due to its contribution to the ideal performance in bleaching paper and cellulose and the fact that it is a non-hazardous agent, Hidromag PC assists in reducing the Chemical Oxygen Demand (COD) of the wastewater generated during the bleaching process.
Benefits of using Hidromag PC
By choosing Hidromag PC, you are able to rely on a marine-sourced solution that guarantees safety, economy and a high level of performance in the pulp and paper bleaching process. Hidromag PC offers the following advantages:
- A high level of purity;
- It is a chemical not classified as dangerous, which contributes to the safety of operations;
- Reduction in costs related to chemical bleaching agents;
- Alkalinity that protects against cellulose fibers;
- Prevents hydrogen peroxide from decomposing into free radicals that act aggressively on fibers;
- Reduces the chemical oxygen demand (COD) of wastewater.
Would you like to learn more about Hidromag PC and its advantages? Get in touch with our team today!
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