物理化学学报 >> 2025, Vol. 41 >> Issue (3): 100023.doi: 10.3866/PKU.WHXB202311032

所属专题： 电化学分离与资源化

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荷叶衍生多孔碳的零电荷电位调节实现废水中电化学捕集镉离子

叶萍1,†, 覃玲霜1,†, 贺萌瑶1, 巫方方1, 陈增烨1, 梁明星1,2,*(), 邓立波1,*()   

  1. 1 深圳大学化学与环境工程学院, 广东 深圳 518060
    2 深圳大学物理与光电工程学院, 广东 深圳 518060
  • 收稿日期:2023-11-26 修回日期:2024-01-09 录用日期:2024-02-04 发布日期:2024-02-26
  • 通讯作者: Email: (M.L.)Email: (L.D.)
  • 作者简介:

    †These authors contributed equally to this work.

  • 基金资助:
    深圳市科技计划(JCYJ20220818095806013); 深圳市科技计划(JCYJ20230808105111022); 广东省自然科学基金(2023A1515012267); 国家自然科学基金(22178223); 国家资助博士后研究人员计划(GZC20231721)

Potential of Zero Charge-Mediated Electrochemical Capture of Cadmium Ions from Wastewater by Lotus Leaf-Derived Porous Carbons

Ping Ye1, Lingshuang Qin1, Mengyao He1, Fangfang Wu1, Zengye Chen1, Mingxing Liang1,2,*(), Libo Deng1,*()   

  1. 1 College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, Guangdong Province, China
    2 College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, Guangdong Province, China
  • Received:2023-11-26 Revised:2024-01-09 Accepted:2024-02-04 Published:2024-02-26
  • Contact:
  • Supported by:
    the Shenzhen Science and Technology Program(JCYJ20220818095806013); the Shenzhen Science and Technology Program(JCYJ20230808105111022); Natural Science Foundation of Guangdong Province(2023A1515012267); National Natural Science Foundation of China(22178223); National Sponsored Postdoctoral Researcher Program of China(GZC20231721)

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摘要：

随着电池、电镀和采矿业的发展，镉(Cd2+)等重金属离子被大量排放，对环境造成严重威胁。由于废水中Cd2+浓度低，传统的去除技术存在动力学慢、二次污染等问题。因此，本文通过微波热解和KOH活化工艺，制备了荷叶衍生碳，开发了基于生物质衍生碳、不对称结构的电容性去离子(CDI)系统。结果表明，获得的纳米片状薄碳(NSTC-3)具有3705.0 m2∙g-1的超高比表面积，在0.5 A∙g-1电流密度下展现了92.5 F∙g-1的比电容(NSTC-3为工作电极，商业活性炭YP-50F为对电极)。分别以YP-50F、NSTC-3为阳极和阴极，在1.2 V电压下，实现了88.6 mgCd·gcathode-1的电吸附容量(Cd2+的初始浓度为100 mg∙L-1)，比对称构型(NSTC-3//NSTC-3)的性能提高了36.3%。优异的去除性能和良好的循环稳定性归因于电极表面电荷性质的调控和不对称电极结构的构建，从而最大限度地减少了同离子排斥，调节了电极电势分布。本研究为设计生物炭基电化学水处理工艺提供了新思路。

关键词: 电容去离子, 镉, 荷叶衍生碳, 不对称构型, 零电荷电势

Abstract:

With the growth of batteries, electroplating, and mining industries, heavy metal ions such as cadmium (Cd2+) are being discharged on a massive scale, thus posing a severe threat to the environment. Conventional techniques for removing Cd2+ from wastewater with low concentrations still suffer from slow kinetics and secondary pollution. A carbon-based capacitive deionization (CDI) system is highly desired but encounters a severe co-ion expulsion effect. Herein, we developed CDI systems based on surface charge-modulated porous carbon and an asymmetric configuration. This was achieved by first preparing porous carbons through facile microwave pyrolysis of lotus leaf followed by KOH activation. The morphology, pore structure, heteroatom content, surface charge, and electrochemical behavior of porous carbons were investigated by adjusting the mass ratio of KOH to carbon. The lotus leaf-derived carbons show a morphology of nanosheet-like thin carbon (NSTC), with their specific surface areas increasing with the amount of KOH used for activation. In contrast, the heteroatom (i.e., nitrogen and oxygen) contents decrease with the increase in the mass ratio of KOH to carbon, resulting in a more positive surface charge. Notably, the NSTC with a mass ratio of 3 for KOH/carbon (NSTC-3) displays an ultrahigh specific surface area of 3705.0 m2∙g-1, and a specific capacitance of 92.5 F∙g-1 at a current density of 0.5 A∙g-1 when coupled with a commercial activated carbon in an asymmetric YP-50F//NSTC-3 supercapacitor. Consequently, the CDI cell equipped with a YP-50F as the anode and a NSTC-3 as the cathode exhibits a high specific adsorption capacity of 88.6 mgCd·gcathode-1 at 1.2 V in a 100 mg∙L-1 Cd2+ solution, which is about 36.3% higher than that of the symmetrical configuration NSTC-3//NSTC-3. Furthermore, 71% of the initial removal capacity of the YP-50F//NSTC-3 system is retained after 7 cycles of charging and discharging. Characterizations of the cathode after the adsorption process indicate that the Cd2+ is captured by both electrical-double-layer and pseudocapacitive mechanisms. Additionally, CdCO3 precipitate is also responsible for Cd2+ removal, which might be ascribed to the reaction of dissolved CO2 in aqueous media with Cd2+ under the electrified action. The high removal performance and excellent cycling stability are attributed to the tunability of the surface charge properties and the asymmetric configuration, which minimizes the co-ion expulsion and modulates potential distribution. This study provides a novel avenue to design biochar-based configurations for electrified water treatment.

Key words: Capacitive deionization, Cadmium, Lotus leaf-derived carbon, Asymmetric configuration, Potential of zero charge