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Grey to black color extraction from walnut hulls the outer green or black husks of Juglans species—relies on the rich content of juglone, tannins, and other polyphenolic compounds that produce deep, dark hues. The process begins with collecting fresh or dried walnut hulls, followed by cleaning and drying. The hulls are then ground into a coarse or fine powder to increase surface area for extraction. Extraction is typically carried out using hot water, alkaline solutions, or ethanol under controlled temperature and pH to maximize pigment yield and achieve a rich grey to black color. Techniques like maceration, ultrasound-assisted extraction (UAE), or steam extraction can improve pigment recovery. After extraction, the solution is filtered and concentrated to obtain a stable, intense natural dye used in textile dyeing, leather tanning, and ink production. Precise control of pH, temperature, and extraction time is essential to maintain pigment stability and prevent premature oxidation or color fading.

Herbal / Solvent Extraction Plants

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Herbal / Solvent Extraction Plants

Grey to Black Color Extraction from Walnut Hulls

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