African Silk Biomaterials as Efficient Eco-Friendly Sorbents for Adsorption of Methylene Blue Dye

Abstract

Methylene blue (MB) dye–contaminated wastewater, particularly from the textile industries, contributes to environmental pollution, posing significant threats to human and aquatic life. Therefore, eco–friendly and low–cost adsorbents for efficient MB removal from contaminated wastewater are needed. This study presents the first comparative investigation of MB removal from water using silk cocoon and silk fibroin (SF) powders from the African wild silkworm Argema mimosae. The silk materials were ball milled at different times for up to 150 min and characterized using the XRD, FTIR, TGA, SEM-EDS, zeta potential analysis, and DLS. Batch adsorption experiments were conducted to determine the effects of solution pH, contact time, adsorbent dose, initial dye concentration, and temperature on MB adsorption. The experimental data best fitted the Langmuir and pseudo–second order models for both adsorbents, suggesting monolayer adsorption with a chemisorption rate–limiting step. The maximum adsorption capacities were 78.13 and 81.98 mg g−1 for cocoon and SF powders, respectively. The cocoon and SF powders achieved removal percentages of 86.0% and 93.5%, respectively, within 90 min. Thermodynamic parameters indicated that the adsorption was spontaneous. The findings demonstrate the good potential of A. mimosae silk biomaterials as promising, low–cost, eco–friendly, and sustainable adsorbents for the removal of dyes from contaminated water.