Carbon-based adsorbents possess exceptional adsorption capability, making them an ideal platform for the remediation of environmental contaminants. Here, we demonstrate carbonized lignosulfonate (LS)-based porous nanocomposites with excellent adsorption performance towards heavy metal ions and cationic dye pollutants. Through microwave-assisted hydrothermal carbonization, a green approach was employed to carbonize lignosulfonate to carbon spheres. The LS-derived carbon spheres were then oxidized into nanographene oxide (nGO) carbon dots. A facile two-step procedure that involved the self-assembly of nGO and gelatin into a hydrogel precursor coupled with freeze-drying enabled the construction of three-dimensional (3D) free-standing porous composites without the use of organic solvents or chemical crosslinking agents. The favorable pore structure and abundance of surface functional groups on the nGO/gelatin porous composite proved to substantially facilitate the adsorption of Cu(II) in comparison to conventionally-used activated carbon. Further enhancement of adsorption performance was achieved by introducing additional surface functional groups through a non-covalent functionalization of the porous composite with lignosulfonate. The presence of negatively-charged sulfonate groups increased the Cu(II) equilibrium adsorption capacity (66 mg/g) by 24% in comparison to the non-functionalized nGO/gelatin counterpart. Both functionalized and non-functionalized composites exhibited significantly faster adsorption rates (40 min) compared to many graphene- or GO-based adsorbents reported in literature. In addition to the adsorption of heavy metal ions, the composites also demonstrated good adsorption capacity towards cationic dyes such as methylene blue. This paves the way for a high value-added application of lignin in environmental remediation and opens up new possibilities for the development of sustainable materials for adsorption and water purification.

中文翻译：

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碳化木质素磺酸盐基多孔纳米复合材料，可吸附环境污染物

碳基吸附剂具有出色的吸附能力，使其成为修复环境污染物的理想平台。在这里，我们展示了碳化的木质素磺酸盐（LS）基多孔纳米复合材料，对重金属离子和阳离子染料污染物具有优异的吸附性能。通过微波辅助的水热碳化，采用了绿色方法将木质素磺酸盐碳化为碳球。然后将LS衍生的碳球氧化成纳米氧化石墨烯（nGO）碳点。轻松的两步过程涉及将nGO和明胶自组装到水凝胶前体中，并进行冷冻干燥，从而无需使用有机溶剂或化学交联剂即可构建三维（3D）独立式多孔复合材料。与常规使用的活性炭相比，nGO /明胶多孔复合材料上有利的孔结构和丰富的表面官能团被证明可大大促进Cu（II）的吸附。通过用木质素磺酸盐对多孔复合材料进行非共价官能化引入其他表面官能团，可以进一步提高吸附性能。与未官能化的nGO /明胶对应物相比，带负电荷的磺酸盐基团使Cu（II）平衡吸附容量（66 mg / g）增加了24％。与文献中报道的许多基于石墨烯或GO的吸附剂相比，官能化和非官能化的复合材料均表现出明显更快的吸附速率（40分钟）。除了吸附重金属离子外，该复合材料还表现出对阳离子染料如亚甲基蓝的良好吸附能力。这为木质素在环境修复中的高附加值应用铺平了道路，并为开发可持续的吸附和水净化材料开辟了新的可能性。