Utilization of Pineapple Fruit Waste in Greener Alternative Agents for Thai Silk Pretreatment and Acid Dyeing Wastewater Treatment.

Abstract

Pineapple, extensively cultivated in tropical and subtropical regions, contains bromelain, a protein-digesting enzyme that is highly valued in the food and beverage industries. Pineapple residues from food processing retain these enzymes and can be repurposed for silk processing. This research utilized Smooth Cayenne pineapple juice as a degumming agent and its pulp as an adsorbent for dyeing effluent treatment. Pineapple juice, containing bromelain with a protease activity of 16.40 µg/mL·min, effectively removed 22% of sericin from raw silk using a liquid ratio of 30:1 at pH 7 and 60 °C for 60 min. Unlike alkaline degumming, which weakened silk fibers (maximum load 6.18 ± 1.56 N), pineapple juice-treated silk retained higher strength (maximum load 7.80 ± 1.32 N), offering a gentler alternative. The remaining pineapple pulp, after juice extraction, was processed into a porous adsorbent with a surface area of 3.63 m²/g and a pore size of 6.15 nm. This material absorbed acid dyes effectively at pH 5, the normal pH used in the acid dyeing of silk. Valorizing pineapple residues reduces chemical use, energy consumption, and environmental impact while lowering production costs and enhancing local resources.