The Use of Chlorine in Paper Making – Bleaching of Wood Pulp

Here we will explain about  the use of Chlorine in paper making.

What is Chlorine?

Chlorine is a naturally-occurring chemical element that has the symbol Cl and the atomic number 17. Chlorine naturally occurs mainly as NaCl, carnallite [KMgCl2.6(H20)], and sylvite (KCL). It is an essential nutrient for various plants and animals. Chlorine is categorized as the halogens group of elements. It is the second-lightest element of that category.

Chlorine, in the periodic table, appears between fluorine and bromine. Chlorine can be seen as a yellow-green gas at room temperature and it has a pungent, irritating scent (that is quite similar to bleach). Chlorine is an extremely reactive element and it is considered to be a strong oxidizing agent. The word chlorine is derived from the Greek word chloros which means greenish yellow or pale green. Chlorine, in industrial production, is made through several process, such as:

  • The membrane cell process
  • The mercury cell process
  • The diaphragm cell process

History of Chlorine

Chlorine was first discovered by German-Swedish chemist named Carl Wilhelm Scheele in 1774. Carl W. Scheele discovered Chlorine through the chemical reaction of Mineral pyrolusite (MnO2) with Hydrochloric acid (HCl), which was first thought by Scheele as oxygen.

The name “Chlorine” was not introduced until later in 1810 by Sir Humphry Davy, who also proposed and confirmed Chlorine as an element.

Uses of Chlorine

Chlorine can be used for various purposes. Some of them can be seen as listed below.

  • Water disinfectant: it is used as the part of the sanitation process for sewage and industrial waste.
  • Drinking water production
  • Bleaching agent: It is used during the production of paper and cloth.
  • Cleaning products: Chlorine is also used for cleaning purposes. E.g. household bleach.
  • Medicines: About 85% of all medicines that are made today are manufactured using Chlorine. Some medicines that use Chlorine are medicines that are used to treat diseases like, AIDS, allergies, arthritis, cancer, common cold, depression, diabetes, ear infections, fungal diseases, glaucoma, headache, heart disease, hypertension, inflammation, leukemia, malaria, meningitis, nausea, osteoporosis, pneumonia, psoriasis, seizures, ulcers, and whooping cough. Examples of medicines that are manufactured using Chlorine are Acetaminophen (which is used widely as a pain reliever) and BENADRYL® (which is a well-known decongestant).
  • Pesticides: Specifically, insecticides. DDT is the well-known of all pesticides that contain chlorine.
  • Food seasoning: Chlorine is used in food seasoning as a table salt.
  • Food preservatives: Chlorine dioxide (ClO2) is used as a food preservative because it does not react with organic matters that are found in foods to form harmful byproduct. Studies found that ClO2 works as an effective sanitizer which can inactivate a broad spectrum of microorganisms (such as bacteria, fungi, and viruses).
  • Organic chemistry purpose: Chlorine in used in the forming of several compounds, like chloroform, carbon tetrachloride, polyvinyl chloride.
  • Swimming pool treatment: Chlorine is used in swimming pool to kill bacteria that can possibly be harmful to humans. Chlorine kills the bacteria through a chemical reaction. When the chlorine solution is poured into the water, that solution breaks down into several different chemicals, including Hypochlorous acid (HOCl) and Hypochlorite iron (OCl). Those chemicals kill bacteria by attacking the lipids in the cell walls and destroying the cell structure, making them harmless. 
  • Chlorinated solvents: These solvents are commonly used as an extraction medium in many processes, like pharmaceutical process, printing, mining and plastic processing, adhesives manufacturing, and in paint and varnish remover.
  • Chemical productions: Chlorine is also used in chemical production to separate metals (such as copper, lead, zinc, nickel, and gold) from their ores.
  • Polymers: Chlorine is used as material in the making of Polyvinyl chloride (PVC) or also known as vinyl. PVC is one of the most widely produced synthetic plastic polymer, along with polyethylene and polypropylene.
  • Paints: Chlorine can also be used as a paint. Paint that uses chlorine as one of its ingredients is known as Chlorinated rubber paint. Chlorinated rubber paint is widely used in commercial, industrial, and healthcare sectors as a surface coating due to its extremely hard-wearing characteristics.
  • Preparation of Chlorides
  • Dyes
  • Petroleum products
  • Plastics
  • Antiseptics
  • Synthetic rubbers
  • Refrigerants
  • Manufacture of Chlorates

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Effects of Chlorine

Although Chlorine can be beneficial at times, we must also take precautions as Chlorine can also bring us side effects. The effects may be caused by several reasons, such as accidental spill, breathing, skin or eye contact, and swallowing. The effects may take some minutes or even seconds to begin. Some side effects caused by Chlorine can be seen as listed below.

  • Damage cells (by its corrosive acids)
  • Airway irritation
  • Wheezing
  • Breathing difficulty
  • Sore throat
  • Cough
  • Chest tightness
  • Eye irritation
  • Skin irritation
  • Frostbite
  • Pulmonary edema: It is an effect caused by breathing chlorine. It is a condition where the lung contains an excessive amount of water and it makes a difficulty in breathing. Pulmonary edema develops within several hours after exposed to chlorine. Pulmonary edema is also known as lung congestion or pulmonary congestion.

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How to Treat Side Effects Caused by Chlorine

If you happen to be exposed to chlorine, you can follow some precautions to treat you from chlorine side effects.

  • Move away from the area you think you were exposed
  • Remove chlorine from any of your clothing quickly
  • Rinse your skin immediately if you happen to be in contact with chlorine. You may also use soap.
  • Seek medical attention quickly if the symptoms are severe (like Pulmonary edema)

Use of Chlorine in Paper Making

What’s the use of Chlorine in paper making? Chlorine plays an important role in the making of paper. The usual compound of chlorine that is used in the making of paper is Chlorine dioxide. Chlorine dioxide serves as a bleaching agent for wood pulp and it is used because chlorine dioxide minimizes the amount of organochlorine compound that are produced in the process.

The process of doing it is called bleaching of wood pulp, which is a chemical process. In this process, the wood pulp’s color is enlightened and whiten. The output product of this wood pulp bleaching is paper. This process can also be done by using other material than wood, such as bamboo and kenaf.

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