Studies of Lignin based Adsorbent for Dye Removal

Rapid urbanization has led to the accumulation of biomass waste, posing environmental risks such as pollution, greenhouse gas emissions, fire hazards, unpleasant odors, and health concerns. This study addresses the issue by utilizing lignin extracted from biomass sources—Ayous Naturale and Poplar wood (sourced from Alpi S.p.A.) and Hippocastanum (Horse Chestnut) seeds for the adsorption of methylene blue (MB) dye from wastewater. Among various lignin extraction techniques, an optimized alkaline method was employed, testing NaOH concentrations of 5%, 7.5%, and 10%. The 10% NaOH solution yielded the highest lignin content and was selected for further analysis. Extracted lignins were characterized using SEM, FTIR, XRD, and point of zero charge (pHpzc). Lignin-based adsorbents were synthesized and tested for MB removal via UV-Vis spectrophotometry under constant pH, temperature, dye concentration, adsorbent dose, and solution volume. The highest dye removal efficiency was 64% for Hippocastanum and 61% for Ayous Naturale lignin. Kinetic studies revealed pseudo-second-order behavior for all samples except Hippocastanum, and intra-particle diffusion modeling indicated a multi-step adsorption mechanism. The findings suggest that lignins derived from these biomass wastes are effective and eco-friendly adsorbents for dye removal, demonstrating potential for industrial-scale application.