Dear Aynaz Biuky please do recommend my answer if it was helpful

The removal of pigments and dyes from High-Density Polyethylene (HDPE) can be challenging due to the porous and non-polar nature of the material. Various methods and techniques have been explored in the literature to achieve pigment and dye removal from HDPE surfaces. Below is a literature review highlighting some of these methods:

1. Chemical Solvents:

• Solvent Extraction: One common method involves using chemical solvents to dissolve and extract pigments and dyes from HDPE surfaces. Common solvents used include acetone, alcohol, and various organic solvents. These solvents can effectively remove surface contaminants through dissolution and subsequent rinsing.
• Alkaline Solutions: Alkaline solutions, such as sodium hydroxide (NaOH) or ammonia (NH3), have been employed to remove pigments and dyes from HDPE surfaces. The alkaline nature of these solutions helps break the chemical bonds between the contaminants and the HDPE.

2. Mechanical Scrubbing:

• Abrasion and Scrubbing: Mechanical methods involve the use of abrasive materials or scrubbing tools to physically remove pigments and dyes from the surface of HDPE. These methods are often used in combination with chemical solvents to enhance effectiveness.

3. Ultrasonic Cleaning:

• Ultrasonic Cleaning: Ultrasonic cleaning utilizes high-frequency sound waves in a liquid medium to create microscopic bubbles that agitate and dislodge contaminants from the HDPE surface. It is particularly effective in removing pigments and dyes from intricate or hard-to-reach areas.

4. Thermal Methods:

• Heat Treatment: Elevated temperatures can be used to soften and remove pigments and dyes from HDPE surfaces. This method is often employed in combination with other cleaning techniques and may require caution to prevent damage to the HDPE.

5. Surfactant-Based Cleaning:

• Surfactants: Surfactants, which are surface-active agents, can be used to facilitate the removal of pigments and dyes from HDPE. Surfactants work by reducing the surface tension between the contaminants and the HDPE, allowing them to be more easily lifted off or dispersed in a cleaning solution.

6. Oxidative Cleaning:

• Oxidative Cleaning: Oxidative agents like hydrogen peroxide (H2O2) can be employed to break down and remove pigments and dyes from HDPE surfaces. This method is effective in decolorizing and removing a wide range of contaminants.

7. Biological Methods:

• Enzymatic Treatment: Some studies have explored the use of enzymes to degrade and remove pigments and dyes from HDPE. Enzymes, such as lipases or proteases, can break down organic contaminants, facilitating their removal.

8. Combination Methods:

• Combined Methods: In practice, a combination of methods is often used to enhance the efficiency of pigment and dye removal. For instance, a cleaning process may involve a chemical solvent followed by mechanical scrubbing or ultrasonic cleaning.

9. Adsorption and Filtration:

• Adsorbents: Certain adsorbent materials, such as activated carbon or zeolites, can be used to adsorb pigments and dyes from solution or suspension. This method is more commonly used in wastewater treatment processes.

10. Biodegradable Cleaners:

• Biodegradable Cleaners: Some biodegradable and environmentally friendly cleaning agents have been explored as alternatives for pigment and dye removal from HDPE surfaces. These cleaners aim to reduce environmental impact.

11. Nanomaterial-Based Cleaning:

• Nanomaterials: Nanoparticles and nanomaterials with specific properties, such as titanium dioxide (TiO2) or graphene, have been investigated for their potential in removing pigments and dyes through adsorption and photocatalytic degradation.

It's important to note that the choice of method for pigment and dye removal from HDPE will depend on factors such as the type of pigment or dye, the extent of contamination, and the specific requirements of the application. Additionally, the effectiveness of each method can vary depending on the particular contaminants and the surface characteristics of the HDPE material.

When conducting research or practical applications related to pigment and dye removal from HDPE, it's advisable to refer to relevant literature and conduct experiments to determine the most suitable method for your specific needs. Consider the environmental and safety implications of the chosen method, especially if it involves chemical solvents or other potentially hazardous materials.

Thank you so much dear Tobias Makuochukwu Onyia

May I know your references?

Dear Aynaz Biuky the link will be helpful

https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=What+are+the+different+methods+of+removing+pigments+and+dyes+from+HDPE%3F&btnG=