Compost-based sustainable treatment for simulated textile dye effluents: Evaluating adsorption capacity and...

Pollution from textile dye effluents is of growing environmental concern owing to the economic importance of the dye industry, the high toxicity of many dyes and the high cost of decontamination methods. This study evaluated urban-waste derived compost as an eco-friendly and cost-effective adsorbent to decontaminate simulated dye effluents. Batch adsorption experiments showed maximum adsorption capacities of 330, 150 and 35 mg g^-1 for Crystal Violet (CV), Brilliant Green (BG), and Rhodamine B (RhB), respectively. Adsorption efficiencies exceeding 80-90 % were achieved under optimal pH and compost dosage. Fixed-bed column experiments confirmed the highest affinity for CV, with a breakthrough time of 700 min, compared to shorter times obtained for BG and RhB. The adsorption affinity largely depended on the chemical structure of the dye, as well as on compost functional groups and surface charge. Phytotoxicity assays using Lollium perenne revealed acute toxicity of CV and BG solutions, with germination rates below 30 % and marked root elongation inhibition. However, leachates from the dye-exposed compost had less effect on germination and root elongation than either non-dye-exposed compost leachates or pure dye solutions, suggesting that the dye-exposed compost poses minimal ecological risk. Overall, these findings confirm that urban-waste compost is an effective and viable adsorbent for textile dye removal from aqueous effluents, with strong potential for wastewater treatment applications and safe reuse as a soil amendment.