Sodium Hydroxide in Paper Production and Recycling

Sodium Hydroxide in Paper Production and Recycling

There are three significant steps in paper manufacturing:
The raw material is pulped to obtain fibers that can be used to produce paper. The pulp is brightened or bleached.
This bleacher or brightened pulp is then developed into the paper.

Cellulose has always been used to make paper. According to conventional methods, the plant containing this natural fiber is cut into tiny pieces and then mashed in water so that the fibers get isolated. This mixture is then poured into a wire mesh mold followed by pressing out the excess water and drying the paper sheet.

To obtain a smooth printing surface and meet other specific requirements some paper products use fillers, coating, and other additives. An increasing number of paper manufacturers currently use wood as a source of cellulose.

materials used in Papermaking Process

Four essential materials are used in the manufacturing process of paper. These materials include water, energy, chemicals, and fibers.

Water: Water is used to carry the fibers through all the manufacturing steps and chemical reactions. It also separates organic residues from the pulp.
Energy: The papermaking process involves the usage of both electricity and steam. Energy for this process is obtained from oil, coal, natural gas, or hydroelectric power.
Chemicals: Chemicals are used in additives like fillers and coatings to meet the specific requirements of all kinds of papers. Caustic soda is used to clean the recovered fibers. Wood chips are cooked in a chemical solution during the kraft and sulfite pulping process to dissolve the lignin that compresses fibers. Caustic soda is added to increase the pH in the pulping process of fibers. The higher pH of the paper fiber solution causes
the fibers to smoothen and swell. it is important for the grinding process of the fibers.

In many papermaking processes, wood is treated with a solution containing sodium sulfide and sodium hydroxide. This helps dissolve most of the unwanted material in the wood. leaving relatively pure cellulose, which forms the basis of the paper. In the paper recycling process, sodium hydroxide is used to separate the ink from the paper fibers allowing the paper fibers to be reused again.
Sodium hydroxide is also used to refine raw materials for wood products such as cabinets and furniture and in wood bleaching and cleaning.

Fibers: Cellulose fibers are the main components in making paper. Lignin, organic glue, is made from flexible cellulose fibers obtained from wood. This glue is found in plenty in softwood trees than in hardwood trees. Several non-wood plants are used as raw materials for paper and some of the fibers obtained from these plants can be grouped into agricultural residues.

How Paper Gets Recycled Wood is the best source of pulp for making paper, but the used paper is also a rich source of pulp. Writing and printing on paper does not remove the fiber content, and fiber eventually becomes paper.

Recycling Paper Process

Sodium Hydroxide in Paper Production and Recycling
Here’s How the Process of Recycling Paper Works:
Recycling start by collecting paper from multiple sources such as offices, homes, and universities. After the paper is collected, it is then graded to sort a similarly graded paper together. Grading is essential because it determines the amount of fiber that can be extracted from the pulp. The sorted paper is then turned into pulp using water, hydrogen peroxide, and caustic soda with soap. The pulp thus formed is screened for non-paper debris such as staples and plastic. The pulp is now all fiber and will be repeatedly de-inked until it becomes white. The whitened pulp is fed into rollers, which removes most of the water after which it is moved onto a dryer.

Lastly, the almost dry pulp is pushed through an ironing-board-type machine that rolls it into the desired paper grade.
It is essential to note here that paper recycling is not comparable to other types of recycling, like aluminum recycling. With metals, the metallic properties are retained after repeated recycling, but recycling paper leads to a reduction in the length of fibers. Eventually, recycled paper will
reach a point where it can no longer be recycled.
ARAX CHEMISTRY is a great manufacturer of Caustic Soda Flakes, Aluminum Sulfate, and Copper Sulfate which offers its High-quality products.

Sodium hydroxide details
Sodium hydroxide details

Sodium hydroxide details

Sodium hydroxide details : Sodium hydroxide (NaOH) an inorganic compound with following synonyms

Caustic soda


Sodium hydrate

NaOH widely used inorganic industrial chemical.

Sodium hydroxide’s chemical formula is NaOH

NaOH molecular weight of 39.997 g/mol

Sodium hydroxide is containing ph of ~12-14

Sodium hydroxide characteristics can be mentioned as

Raw material for various industrial products Co-product in chlorine synthesis

Strong base

Highly corrosive

Auxiliary chemical

Odorless material

Caustic soda forms

Caustic soda is available in two forms – Caustic soda lye and Caustic soda solid.
Solid form of caustic soda can be in the form of Caustic soda flakes or Caustic soda granules.

Pure form of sodium hydroxide also available as

Sodium hydroxide pellets

Sodium hydroxide flakes

Sodium hydroxide granule

Sodium hydroxide solution

Caustic soda has wide variety of industrial sectors like

In pulp and paper processing industry caustic soda used at the stages like bleaching process,
in de-inking of waste paper, and in water treatment.

Next major industry like textile industry caustic soda is used to process cotton and synthetic fibers

Caustic soda is utilized more in the soap and detergent industry.

Other caustic soda uses include

In oil and gas industry – to remove pungent smells

In household cleaning products

In beverage bottles

In home soap making

Worldwide there is high demand for caustic soda and increase in caustic soda prices,
applications in daily lives this article gives the different modern caustic soda manufacturing processes.

Production method

Sodium Hydroxide solutions are produced by three different technologies

Mercury cells

Membrane cells

Diaphragm cells

Each of above processes utilizes sodium chloride (NaCl) salt as the primary raw material.
Electrolytic splitting of salt results in products like chlorine and sodium ion (Na+).
In turn Na+ will react with water in the mercury cell to form Sodium hydroxide and Hydrogen as by product.

Mercury Cell

Fig. [1] Mercury cell

In the Mercury Cell Process saturated brine voyages down a steel trough roughly 15 meters in
length and one-meter-wide between a streaming film of mercury
(the cathode) and titanium plates (the anodes). Direct current is connected between the anode and cathode.
Chlorine freed at the anodes gathers above the brine and is begun as
a hot, wet and corrosive gas.

Sodium ions are released at the surface of the streaming mercury cathode,
forming an amalgam of low concentration with the mercury,
which streams out of the cell without reacting with the water or chlorine.

The mercury cell thus has two products

(i) Hot, wet chlorine

(ii) Sodium amalgam

The soda cell or decomposer is a cylindrical steel trough loaded with graphite balls or graphite electrodes.

The sodium amalgam is passed, along with pure water, into the decomposer,
where it reacts to transform Sodium hydroxide as a controlled 50 per
cent aqueous solution and hydrogen gas,

liberating fee mercury, which is reused again to the electrolytic cell.

The graphite provides a surface that expedites this reaction.

The following two types of reactions called brine cell and the soda
cell respectively.

Brine Cell

                       2Cl = Cl2 + e

                       Na + e = Na

                       Na + Hg = Na/Hg

Soda Cell

                          2 Na/Hg + 2 H2O = 2NaOH + H2 + 2Hg

Diaphragm Cell

This method produces 71 per cent of Sodium hydroxide.
Diaphragm Cell process utilizes asbestos or alternate substitutes to asbestos,
to separate the co-products Sodium Hydroxide (Caustic Soda) and Chlorine.

The production of 50 per cent NaOH occurs primarily outside of the electrolytic cell.

The diaphragm cell produces a very weak ‘cell liquor,’ that contains 12-14 per cent,
by weight, NaOH and the constant volume of NaCl salt.
The cell liquor is subsequently evaporated in a three or four ‘effect’ evaporation method
to a final nominal concentration of 50 per cent NaOH by weight.

The surplus salt is precipitated and filtered through the evaporation method for subsequent reuse/recycle.

This method produces the lowest quality electrochemical NaOH solutions.

The quality considerations with respect to the diaphragm cell produced Caustic solutions include comparatively high salt,
chlorates, carbonates, and sulfates. Salt, as NaCl, concentrations are
typically 1.0 per cent, with maximums ranging from 1.1 to 1.3 weight per cent, counting on producer.

The diaphragm cell created Caustic Soda (NaOH) is usually referred as Diaphragm Cell Grade. It is conjointly known as Commercial Grade, Technical Grade, and occasionally Technical Diaphragm or other similar combinations.

An additional ‘grade’ of Caustic Soda (NaOH) produced by the diaphragm cell method is the sublimate grade.
The production of sublimate Grade involves the further evaporation of the 50 per cent Diaphragm Grade NaOH solution to cut back the salt concentration.
The higher concentration solution is then re-diluted to the 50% concentration that is commercially available as sublimate grade Caustic Soda.

Common uses include process and sewer water neutralization,
textiles production, soaps and detergents and aluminum production.
These uses and applications typically can confer with the Caustic Soda as any of the varied grades.

Membrane Cell

This method produces approximately 13 per cent of Sodium Hydroxide.
The membrane cell method utilizes a selective membrane that separates
the Chlorine and Sodium ions. The membrane permits the Sodium ion to migrate across the membrane
whereas keeping the Chlorine gas and salt (brine) solution in a compartment on the opposite facet of the membrane.

The Sodium ion is reacted with refined water as within the mercury cell to provide the Caustic Soda (NaOH).
Evaporation is employed, as within the diaphragm method,
to lift the concentration up to the nominal 50 weight per cent solution.
The salt concentrations are not targeted as considerably during this
evaporation method attributable to the selective diffusion nature of
the membranes as well as the reduced quantity of evaporation needed
during this method opposed to the diaphragm evaporation.

The Caustic Soda produced by the membrane cell process is most typically brought up
as Membrane Grade. It conjointly contains a growing acceptance as
a Rayon Grade product in all areas outside of rayon fiber production.

Hope this article would be helpful.

Arax chemi Co. is a great producer of caustic soda flakes, and we are here to do service for you including export caustic soda flakes to your country or any other place you have inquiry.

Contact us for further details

office: +98-21-36442712 to 18

Export unit :

Caustic soda in Iran
Caustic soda in Iran

Caustic soda in Iran

Caustic soda in Iran : Caustic soda flakes 98-99% also known as sodium hydroxide (Noah)
as is an inorganic compound which is used in many different industries.
We have strong business relationship, and local contract with the leading caustic soda flakes/lye manufacturers in Iran.
The state-of-the-art facilities of the factories make us able to source high quality
caustic soda flakes with real purity which can be even used in food and
pharmaceutical industries.
With respect to our economical price directly from the manufacturers, product high quality,

professional packaging, and on-time delivery, we have already penetrated many markets such as Far East,
Middle East, Asian countries, Latin America, Turkey, Iraq, Uzbekistan, Kazakhstan, Turkmenistan,
Afghanistan, Pakistan, Georgia, Syria for this product.

Caustic soda packing:

our manufactured caustic soda flake is packed in best quality laminated 25 kg polypropylene
bags with inside polyethylene layer. We can offer the bags inside 1 MT jumbo bags,

and also on 1.5 MT pallets.
For our major customers that order on no name basis, we are in position to design and print
customized packaging upon customers’ requirements based on solo partnership contracts.

Caustic soda delivery basis:

we have perfect access to all transportation routes to the globe especially CIS countries,
Middle East countries, Europe, and Africa by truck, train and vessel, and can dispatch our products
immediately to any country in the world with cost-effective rates, and deliver the goods to your final destination so that you can enjoy your purchase from our factory smoothly.

Payment term:

As there are some restrictions for Iranian banks, most of our customers asked for some solution
to be able to arrange cash – T/T payment for us outside Iran. Therefore, we tried to solve this issue.

We have partner company in Latvia the payment in cash – T/T and in AED/EUR/USD
currencies from our valuable customers around the world.

Our competence:

The economical prices directly from the manufacturers, high quality of the product as per the certified lab test of the factory,
and on-time delivery of the product are the most normal things any supplier must follow
to support its customers.
Therefore, we try hard to follow these simple but important priorities to support and be
loyal partners to our valued customers,
and also promote our markets and match ourselves with the new markets around the world.

Therefore, we invite all the traders, distributors and end-users to try us with our quality
services and competitive prices.

Caustic soda flakes Applications:

Refining alumina:

caustic soda flake is used in the refining of alumina containing more like bauxite to produce aluminum oxide.
Pulp and paper: Sodium hydroxide is an important commodity chemical for the pulp and paper industry.
Principal uses in pulp and paper production include the cooking/processing of Kraft pulps,
the extraction of lignin during the pulp bleaching sequences, and the on-site
manufacture of sodium hypochlorite.
The general pulp bleaching procedure involves a bleaching sequence during which impurities and colored matter in the pulp are oxidized and/or converted to alkali-soluble
and an extraction sequence during which the impurities are removed. Extraction stages
almost invariably use caustic soda.


caustic soda flake is used mainly for two processes in textile manufacture.
Mercerizing of fibre with sodium and hydroxide solution enables greater tensional
strength and consistent lustre. It also removes waxes and oils from fibre to make the fibre more receptive to bleaching and dying.

Detergent: caustic soda flake is also widely used in making soaps and detergents,
Sodium hydroxide was originally used for soap manufacture, but now has a wider
variety of functions.
As well as an extractor and refining agent for certain oils, sodium hydroxide is used to
produce active agents,
or builders in modern synthetic detergents.

Water treatment:
Caustic soda flake is utilized to raise the PH of water in a variety of applications.

Other applications:

Caustic soda flake is used for the desulphurization in the petrochemical industry.
Caustic soda flake is used for starch production.
Caustic soda flake is used for the manufacture of bio-diesel.
Caustic soda flake is a source of sodium ions for reactions that produce other sodium compounds.