Thank you very much. Could you please inform me any mechanism for significant increase in wash fastness of natural dyed cotton fabric due to uv/ozone treatment?

Poorer wet fastness levels are typical for textiles dyed with most of natural dyes. Possibly a cationic aftertreatment can help to improve the fastness level. For further information see

Samanta et al. J. Text. Inst. 100, 565 (2009)

This is specific to each natural dye. must all aboard know the chemical class of the dye and its mounting mechanism. Then you can choose the appropriate treatment (cationization, UV / ozone, plasma, etc.)

Thanks Helga Thomas. Please provide me the title of the paper regarding the cationic after treatment of cotton fabric for improving the wash fastness. 

The title is: "Application of single and mixtures of red sandalwood and other natural dyes for dyeing of jute fabric: studies on colour parameters/colour fastness and compatibility"

Thank you for your cooperation. 

Direct dyes have poor fastness properties ,   But we cannot get all the shades in natural dyes  i Sandal wood colour is fast , But blue Or purple by fruit  juice is  not fast , Natural  dyes turmeric has poor fastness but its fastness could be improved 

Please read our publication (attached) where you will find many such treatments for improving the colour fastness of cotton, dyed with natural dyes.

Article Optimization of fastness and tensile properties of cotton fa...

Most important  process in the cotton dyeing is scouring process. Impurities present in the cotton varies from one region to another Calcium , Magnesium Iron manganese and copper vary from one variety to another . To get good fastness properties porous structure and capillaries in fully developed cotton should have free flow of liquor during dyeing. If this is done in scouring fastness of the natural dyes could be improved on cotton. Need based reciepe has to be worked our. Best cotton has following impurities 

1) Calciun 650 PPM 2) Magnesium -420 ppm 3) Iron 12 ppm ,4) Magnesium less 2  5) Copper less then one.

But cotton we recieve has calcium 1643ppm . Magnesium 870 ppm  Iron 88PPM , Magnesium 12 ppm , and copper 5ppm 

The impurities present in the cotton wont allow  proper dyeing and fastness in  dyed  products. The measurements and processes required are inadequate in the process houses in decentralised sector. Hence, this awareness is required to be inculcated in all dye Houses 

I hope this will give you lead to get fastness properties. If you need further clarifications free to contact me 

The wash fastness is presumed as the bottleneck shortcoming of natural dyed textile materials.  However, to gratify that shortcoming several researchers have taken several attempts. Some of those are 

1. Selection of favorable anchoring groups containing dye molecules  for cellulose

2. Selection of favorable dye extraction techniques. (Ultrasound, Microwave)

3. Lion share dye molecules are anionic that why it is very crucial to select proper crosslinker/ mordants. Habitually metallic salts are used but the uses of metal salts are problematic because the substantial amount of metallic salts remain unreacted in the mordanting bath. Those residual metals lead environmental hazard.  Additionally, the trace metals onto fabric prone to migrate in sweat and afterward cause various skin problems. Please check the below articles for clarification. 

http://journals.sagepub.com/doi/abs/10.1177/0040517516639816

http://www.sciencedirect.com/science/article/pii/S2213343716302305

That's why it is necessary to use alternative novel mordanting agents like tannic acid, natural mordants, etc. Additionally, cotton can be pre-cationized by chitosan. 

4. Irradiation of both cotton and dye could be carried out to obtain upturned outcomes. 

5. UV, Ozone, plasma techniques can be employed. 

6. The particle size of the molecule can be optimized for obtaining outstanding durability of natural dyed cotton toward laundering. 

Best wishes 

increase the anchoring capability of the dye by appropriate ion, then you will get your desired results