ABSTRACT

The adsorption of chlorinated aromatic compounds (CACs) on pristine biochar was often limited. Surface modification can greatly improve the adsorption capacity of biochar. In this work, by pyrolysis activation of rubber-seed shell wastes, nitrogen auto-doped biochar (RSS-NBC) was synthesized and used for purifying CACs-containing wastewater. Systematic characterization results showed that after proper treatment, the as-prepared RSS-NBC had high specific surface area, abundant surface oxygen- and nitrogen-containing functional groups, and nano-scale pore structure. Batch adsorption experiments were conducted with using three typical CACs probing pollutants, i.e. 1,2-dichlorobenzene (1,2-DCB), 2,4-dichlorophenol (2,4-DCP) and 2,4-dichlorobenzoic acid (2,4-DCBA). The adsorption experiments results showed that the maximum adsorption amounts of 1, 2-DCB, 2,4-DCP, and 2,4-DCBA could reach 2284, 1921, and 1142 mg/g at 298.15 K. Moreover, 90% of the equilibrium adsorption amount can be reached within 0.5 h. The adsorption kinetic results showed that the adsorption processes of the three CACs followed the pseudo-second-order rate model and were dominated by chemisorption. Also, the adsorption isotherms of 1, 2-DCB and 2, 4-DCP belonged to the Freundlich model and were valid for multilayer adsorption, while the adsorption of 2,4-DCBA followed Langmuir model and single-layer adsorption. The thermodynamics data indicated that the spontaneous adsorption process of 1, 2-DCB and 2, 4-DCP was endothermic while that of 2,4-DCBA was exothermic. After 5 cycles of adsorption-regeneration, the removal efficiency of RSS-NBC particles still remained more than 80% for the three typical CACs, indicating that it could be reused as an effective and retrievable adsorbent in the treatment of CACs-containing effluents.

摘要

氯化芳香化合物 (CAC) 在原始生物炭上的吸附通常是有限的。表面改性可以大大提高生物炭的吸附能力。在这项工作中，通过热解活化橡胶种子壳废物，合成了氮自掺杂生物炭 (RSS-NBC) 并用于净化含 CACs 的废水。系统表征结果表明，经过适当处理后，所制备的RSS-NBC具有高比表面积、丰富的表面含氧和含氮官能团以及纳米级孔结构。使用三种典型的 CACs 探测污染物进行批量吸附实验，即 1,2-二氯苯 (1,2-DCB)、2,4-二氯苯酚 (2,4-DCP) 和 2,4-二氯苯甲酸 (2,4 -DCBA）。吸附实验结果表明，最大吸附量为1，2-DCB、2,4-DCP和2,4-DCBA在298.15 K时分别可达2284、1921和1142 mg/g，而且在0.5 h内可达到90%的平衡吸附量。吸附动力学结果表明，三种CACs的吸附过程遵循伪二级速率模型，并以化学吸附为主。此外，1, 2-DCB和2, 4-DCP的吸附等温线属于Freundlich模型，适用于多层吸附，而2,4-DCBA的吸附符合Langmuir模型和单层吸附。热力学数据表明，1, 2-DCB和2, 4-DCP的自发吸附过程是吸热的，而2,4-DCBA的自发吸附过程是放热的。经过5次吸附-再生循环后，三种典型CAC对RSS-NBC颗粒的去除效率仍保持在80%以上，