Preparation and adsorption performance of biomass-based polyurethane adsorbents for gallium ions from coal gangue acid leachate

Although coal gangue acid leachate is rich in gallium, its strongly acidic nature, the heavy dependence of adsorbents on petroleum‑based raw materials, and the difficulty in straw management constitute major technological bottlenecks. Utilizing straw to prepare biomass‑based polyurethane adsorbents aligns with the concept of “treating waste with waste” and offers a viable route to relieve the shortage of gallium resources. Therefore, this study focused on the preparation of biomass-based polyols, the synthesis of biomass-based polyurethane adsorbents, and the adsorption and separation of gallium ions in coal gangue acid leachate. The preparation conditions and adsorption conditions were optimized. Under the optimal conditions, 10% polyether polyol was replaced, and the hydroxyl value of biomass-based polyol was 355.23 mgKOH/g. At the optimized condition of 40°C, this adsorbent achieves an adsorption efficiency of 85.07%, demonstrating fast and efficient adsorption performance. In contrast, traditional polyurethane adsorbent requires higher temperatures and longer adsorption times to achieve a comparable adsorption effect. The molecular weight of the synthesized biomass polyurethane adsorption adsorbent is 36,560. Furthermore, the adsorption mechanism of biomass-based polyurethane adsorbent was revealed, which provided a new method for the efficient recycling of biomass waste and coal gangue.