Question 1

Can Thiourea Dioxide Really Replace Sodium Hydrosulfite?

Accepted Answer

Yes, although in theory a threefold substitution is possible, the replacement should be process-specific.

Question 2

Why Would a Textile Factory Switch from Sodium Hydrosulfite?

Accepted Answer

The main reasons are usually:

Question 3

Is Thiourea Dioxide Stronger than Sodium Hydrosulfite?

Accepted Answer

Under suitable alkaline and thermal activation conditions, Thiourea Dioxide can provide a very strong reducing environment.

Question 4

How Much Thiourea Dioxide Should I Use Instead of Sodium Hydrosulfite?

Accepted Answer

There is no universal conversion factor.

Question 5

Can Thiourea Dioxide Reduce the Chemical Consumption?

Accepted Answer

Potentially, yes. The correct calculation is chemical cost per tonne of fabric, rather than chemical price per kg.

Question 6

Can You Provide a Cost Calculation for My Factory?

Accepted Answer

Yes. We recommend using the following formula: annual chemical cost = production volume × dosage × chemical price.

Question 7

Does Thiourea Dioxide Work Particularly Well for Polyester Reduction Clearing?

Accepted Answer

Yes, polyester/disperse-dye reduction clearing is one of the most relevant applications to evaluate.

Question 8

Can Thiourea Dioxide Be Used for Color Stripping?

Accepted Answer

Yes. Thiourea Dioxide is used as a reductive stripping agent for certain dyed textiles.

Question 9

Can Thiourea Dioxide Completely Replace Hydrosulfite in Stripping?

Accepted Answer

Not necessarily in every application. The answer depends on dye chemistry, shade depth, fiber type, dye-fiber bonding, pH, temperature, treatment time and the required stripping level.

Question 10

Can Thiourea Dioxide Be Used for Dyeing-Machine Cleaning?

Accepted Answer

Yes, this is another practical application to evaluate.

Question 11

What About Safety and Storage?

Accepted Answer

This is an important purchasing consideration.

Question 12

Does Thiourea Dioxide Have an Odor Problem Like Hydrosulfite?

Accepted Answer

In solid form, Thiourea Dioxide is essentially odorless. Even after dissolving in water, its odor remains very faint — it is simply not in the same league as sodium hydrosulfite.

Question 13

Will Thiourea Dioxide Damage Polyester Fabric?

Accepted Answer

Under properly controlled conditions, Thiourea Dioxide can be used for polyester reduction processing.

Question 14

Will Thiourea Dioxide Affect the Color Shade?

Accepted Answer

It can, depending on the dye and process. That is precisely why Thiourea Dioxide should be evaluated using instrumental color measurement.

Question 15

What Is the Recommended Laboratory Test?

Accepted Answer

We recommend a 4-point dosage screening test: fabric = customer production polyester fabric; liquor ratio 1:10–1:20; temperature 70–80°C; time 15–20 min; Thiourea Dioxide 0.5 / 1.0 / 1.5 / 2.0 g/L; NaOH 1–2 g/L as a starting range.

Question 16

How Much Thiourea Dioxide Would I Need per Tonne of Fabric?

Accepted Answer

A simple calculation is: Thiourea Dioxide kg/tonne = dosage g/L × liquor ratio L/kg ÷ 1,000.

Question 17

What Is the Real Cost Advantage?

Accepted Answer

The correct purchasing calculation should contain five variables: 1. product price; 2. dosage; 3. liquor ratio; 4. process efficiency; 5. wastewater/operating cost.

Question 18

Is Thiourea Dioxide Suitable for Pulp and Paper Applications?

Accepted Answer

Yes, Thiourea Dioxide has reducing applications in pulp and paper chemistry, including selected bleaching/deinking processes.

Question 19

Can You Provide Free Samples for Testing?

Accepted Answer

Yes. For qualified textile, dyeing, printing, pulp and paper customers, we can provide a free trial sample for laboratory or pilot-scale evaluation, subject to shipping and sample policy.

Question 20

How Do I Start a Free Thiourea Dioxide Replacement Trial?

Accepted Answer

Very simple. Please send us the following five pieces of information: ① current application (polyester reduction clearing / stripping / machine cleaning / paper deinking / other); ② current hydrosulfite dosage, e.g. 3 g/L; ③ current NaOH dosage, e.g. 2 g/L; ④ processing conditions — temperature + time + liquor ratio; ⑤ annual consumption, e.g. 50 tonnes/year.

Question 21

What exactly is FAS?

Accepted Answer

Formamidine Sulfinic Acid (FAS), is a sulfur-containing reducing agent used in various bleaching and de-colorization applications.

Question 22

Why can FAS be used for deinking pulp?

Accepted Answer

FAS generates active reducing species under suitable alkaline conditions.

Question 23

Can FAS replace Sodium Hydrosulfite?

Accepted Answer

In many applications, FAS can be evaluated as an alternative to Sodium Hydrosulfite (Sodium Dithionite, Na₂S₂O₄).

Question 24

How much FAS is required per ton of pulp?

Accepted Answer

There is no single universal dosage.

Question 25

How do I convert my existing Sodium Hydrosulfite dosage to FAS?

Accepted Answer

There is no universal 1:1 conversion factor.

Question 26

How much can FAS improve pulp brightness?

Accepted Answer

Brightness improvement depends heavily on the incoming pulp.

Question 27

Is FAS effective for colored wastepaper?

Accepted Answer

FAS can be particularly interesting when the recycled furnish contains colored materials or chromophores that respond to reducing treatment.

Question 28

Can FAS be combined with Hydrogen Peroxide?

Accepted Answer

Potentially, yes.

Question 29

What is the recommended pH for FAS bleaching?

Accepted Answer

FAS performance is strongly affected by pH.

Question 30

What temperature and reaction time are required?

Accepted Answer

FAS bleaching performance is influenced by both temperature and reaction time.

Question 31

Will FAS affect pulp strength?

Accepted Answer

This is an important qualification issue.

Question 32

Does FAS cause brightness reversion?

Accepted Answer

Brightness stability should be evaluated after treatment.

Question 33

Does FAS remove ink, ash, stickies or contaminants?

Accepted Answer

FAS should not be regarded as a universal deinking chemical.

Question 34

What is the environmental impact of FAS?

Accepted Answer

There is an impact, but it is manageable, and it is generally lighter than a conventional sodium hydrosulfite process. FAS is not a "pollution-free" raw material. It decomposes in water: the sulfur ultimately becomes sulfate and the nitrogen becomes urea. The parameters that need to be controlled in wastewater are COD and total nitrogen; no heavy metals and no chlorinated organics are involved.

Question 35

Is FAS safer than Sodium Hydrosulfite?

Accepted Answer

Safety must be evaluated across the entire lifecycle:

Question 36

Is FAS stable at high temperature?

Accepted Answer

Solid FAS is stable at ambient temperature in the dry state, but strictly speaking it is not "heat-resistant". It begins to decompose above about 100°C, and above 126°C it decomposes exothermically, releasing SO₂, NH₃ and other gases. Its thermal stability is markedly better than that of sodium hydrosulfite — which decomposes above 85°C, can decompose explosively at 190°C, and self-ignites on contact with water; FAS has a higher decomposition threshold and behaves more controllably. As a reducing agent it will decompose on heating — and in bleaching applications that decomposition is actually part of the mechanism.

Question 37

Are metal ions important in FAS bleaching?

Accepted Answer

Yes.

Question 38

Is FAS actually cheaper than Sodium Hydrosulfite?

Accepted Answer

This is perhaps the most important purchasing question.

Question 39

Do you have real paper-mill application data?

Accepted Answer

Yes. The FAS produced by our company once accounted for more than 70% of the FAS market for paper applications in China.

Question 40

Can you provide free samples and technical support for a mill trial?

Accepted Answer

Yes — this should be the starting point of a serious FAS development program.

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