Pages 454–457
Abstract
Research summary supplied by the authors
The discharge of waste pickle liquor from the leather industry, characterized by high acidity and elevated sodium chloride content, poses serious environmental and health concerns. This study reports a novel and sustainable approach for the reuse of tannery pickle liquor as both a reaction medium and acid source for the synthesis of azo dyes, which are subsequently utilized within the same leather industry. The process follows green chemistry principles by valorizing waste, minimizing reagent consumption, and operating under energy-efficient, room-temperature conditions. The optimized one-pot process achieved high yields of up to 99.23%, producing 6.43 g of azo dye from skin pickle liquor and 7.7 g from hide pickle liquor at laboratory scale, demonstrating a viable alternative to conventional acid-intensive synthesis routes. The method exhibited strong sustainability metrics, including a high Eco-scale score of 84.19, low Efactor, high reaction mass efficiency, and reduced water intensity compared to traditional processes. Importantly, the sodium chloride–rich wastewater generated after dye synthesis was successfully reused in subsequent leather pickling after pH adjustment to 2.8, eliminating the need for fresh water and additional sodium chloride. The synthesized azo dyes were applied to zeolite-, vegetable-, and chrome-tanned leathers, showing good dye uptake, vibrant coloration, and lightfastness comparable to conventional dyes. Overall, this integrated waste-toresource strategy significantly reduces freshwater and chemical consumption, supports circular economy practices, and contributes to Sustainable Development Goals 6 and 12 by transforming hazardous tannery effluent into a valuable functional product.