Adsorption performance and mechanism of U(VI) removal from wastewater by polyaniline-coated and carbon dot functionalized CoMn2O4
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摘要: 核工业发展产生的含铀废水对人类健康和生态环境产生严重威胁。对含铀废水的有效化处理是核能绿色发展的重要保证。采用化学聚合法合成了一种新型聚苯胺包覆碳点功能化锰钴金属氧化物(CMC20%/PANI)。吸附剂表面丰富的氧、氮基团为U(VI)的高效捕获提供活性位点。采用静态吸附法研究了材料去除溶液中U(VI)的性能。因此，在pH = 5、120 min，CMC20%/PANI对U(VI)的吸附容量达到285 mg/g。吸附过程符合准二级动力学和Sips模型，表明吸附剂对铀涉及单层和多层的化学吸附，并且Sips拟合的理论吸附容量为659.7 mg/g。吸附机制研究表明：静电吸引、孔扩散以及含氧、氮基团的络合配位作用成为CMC20%/PANI对U(VI)的主要去除机制。Abstract: Uranium-containing wastewater posed a serious threat to human health and the ecological environment. Its effective treatment had strategic significance for the green development of nuclear energy and environmental protection. A novel polyaniline-coated carbon dot functionalized manganese cobalt metal oxide was synthesized by chemical polymerization method (CMC20%/PANI). The abundant oxygen and nitrogen groups on the surface of the adsorbent provided active sites for the efficient capture of U(VI). The performance of the material in removing uranium from the solution was evaluated using a static adsorption method. The results show the adsorption capacity of uranium reaches 285 mg/g at pH = 5 and 120 min. The adsorption process is in line with pseudo-second-order kinetic and the Sips model, suggesting that uranium adsorption by the adsorbent involves monolayer and multilayer chemisorption as well as a theoretical adsorption capacity of 659.7 mg/g fitted by Sips. Adsorption mechanism analysis shows that electrostatic attraction, pore diffusion and complex coordination of oxygen and nitrogen groups are the main removal mechanism with CMC20%/PANI on U(VI).
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Keywords:
- CoMn2O4 /
- PANI /
- CDs /
- adsorption /
- U(VI) /
- wastewater
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随着我国桥梁建设的快速发展，交通量的增加，桥梁结构遭遇火灾情况也时有发生[1-4]，2007年10月广东广深高速虎门大桥，油罐车爆炸引发大火，拉索和桥墩都被大火湮灭；2014年，湖南郴州在建赤石特大桥在主跨合拢前6号桥墩左幅塔顶突发大火，事故导致6号桥墩左幅9根斜拉索断裂，这些火灾事故对缆索的受力性能构成了极大的考验。文献[5-8]对钢丝缆索的高温力学性能进行研究，在火灾高温下钢丝力学性能会明显下降，导致缆索的承载能力急剧下降。
采用轻质、高强、耐腐蚀、抗疲劳的碳纤维增强树脂复合材料(Carbon fiber reinforced polymer，CFRP)用于桥梁缆索，可提高桥梁跨径，从根本上解决钢质拉索的腐蚀及疲劳问题。但CFRP索内的CFRP筋遇到火灾后环氧树脂会燃烧分解，影响其极限承载性能，对桥梁结构的安全造成影响。文献[9-12]通过试验研究发现，高温下CFRP筋的力学性能下降十分明显。付成龙等[11]研究了温度对CFRP筋弯曲强度和压缩强度的影响，研究显示温度对试样弯曲强度和压缩强度的影响较大，CFRP筋的强度保留率随温度升高而降低。方志等[12]对较高玻璃化转变温度Tg(Tg >200℃)的CFRP筋高温后力学性能进行研究，处理温度为100℃时，筋材静力性能与常温试件相比未发生明显变化，筋材经历200℃和300℃温升作用后，其抗拉强度、弹性模量和极限拉应变均有所下降。
文献[13-15]对桥梁缆索的阻燃防火措施做了一些研究。李艳等[13]在索体外表面设置一种导热系数很低的耐高温防火涂层，从而降低火源热辐射传给索体的温度。张凯等[14]研究了带砂浆包覆层CFRP筋的高温力学性能，在砂浆包覆层保持完好未爆裂的情况下，包覆层为CFRP筋提供了较好的隔氧环境，CFRP筋在长时间高温作用后具有较高的残余强度。徐玉林等[15]对外包陶瓷纤维防火层的CFRP索的耐火性进行了火灾试验研究，对CFRP 缆索外包陶瓷纤维防火层可大幅提高缆索的临界安全耐火时长。
综上所述，目前已有一些缆索的阻燃防火措施，如外包砂浆或陶瓷纤维防火层，但这些措施会大幅度增大索体直径，严重影响索体外表面的空气动力学特性。本文针对桥梁缆索用CFRP筋在高温下的力学性能及CFRP索的阻燃防火措施进行系统研究，研制开发具有阻燃防火特性的CFRP索，避免火灾带来的风险，保障应用安全，有助于CFRP索的推广应用。
1. CFRP筋高温力学性能
CFRP筋采用拉挤成型工艺制备，为了便于锚固，筋材表面带有螺旋肋，筋材底径7 mm，纤维体积分数为72vol%，密度为1.52 g/cm3，玻璃化转变温度Tg为120℃。
图1为CFRP筋高温拉伸试验。可见，筋材两端采用粘结型锚固方式，筋材锚固后穿过试验台架，在筋材中间自由段部位外套金属铝筒，金属铝筒外缠绕加热带对筒内空气进行加热，采用热电偶监测空气温度，采用温度继电器控制温度，使金属铝筒内温度保持设定温度，采用千斤顶加载，加载速度不超过300 MPa/min。筋材拉伸强度为筋材破断时压力传感器载荷读数除以筋材承载面积。
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图 1 碳纤维增强树脂复合材料(CFRP)筋高温拉伸试验Figure 1. High temperature tensile test of carbon fiber reinforced polymer (CFRP) tendon1.1 CFRP筋不同加热温度下力学性能
对筋材中间自由段部位进行加热，加热至指定温度，保温2 h后进行破断拉伸试验，获得筋材在高温下的拉伸强度。
图2为不同温度下保温 2 h后的CFRP筋材抗拉强度。可以看出，随着试验温度的升高，筋材拉伸强度呈线性下降趋势，270℃加热2 h，筋材强度降为2000 MPa左右，210℃加热2 h，筋材强度最低为2245.8 MPa，比初始强度下降26.13%。图3为保温2 h后筋材高温拉伸破断照片。可以看出，筋材发生了散丝状断裂。
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图 2 不同温度下保温 2 h后的CFRP筋材抗拉强度Figure 2. Tensile strength of CFRP tendons at different temperatures with heat preservation 2 h![]()
图 3 CFRP筋材高温拉伸破断状态Figure 3. Tensile fracture state of CFRP tendons at high temperature1.2 CFRP筋不同加热时间下力学性能
对筋材中间自由段部位进行加热，加热至210℃，分别保温1、2、3 h后进行破断拉伸试验，获得筋材在高温下的拉伸强度。图4为210℃不同保温时间下的CFRP筋材抗拉强度。
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图 4 210℃不同保温时间下的CFRP筋材抗拉强度Figure 4. Tensile strength of CFRP tendons with different holding time at 210℃可以看出，筋材高温拉伸强度仅与试验温度有关，当筋材芯部温度达到保温温度时，筋材的高温拉伸强度与保温时间无关，210℃的高温3 h内，筋材剩余拉伸强度均能达到2245.8 MPa以上。
1.3 CFRP筋加热冷却后力学性能
对筋材中间自由段部位进行加热，加热至指定温度，保温2 h，待筋材充分冷却至室温后进行破断拉伸试验，获得筋材经历高温冷却后的拉伸强度，如图5所示。可以看出，筋材高温加热冷却后继续进行拉伸试验，拉伸强度会存在一定的可逆性恢复，且恢复后的剩余强度均能达到2800 MPa以上，但最终剩余拉伸强度较原始强度呈略微下降趋势，且加热温度越高，剩余拉伸强度越低，最大下降幅度为6.13%。
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图 5 经历不同温度加热2 h冷却后CFRP筋材抗拉强度Figure 5. Tensile strength of CFRP tendons after heating at different temperatures for 2 h and cooling2. CFRP索阻燃防火措施
分别采用石棉布、陶瓷纤维布及阻燃防火涂层材料来研究对CFRP筋/索的阻燃防火效果。
2.1 石棉布、陶瓷纤维布阻燃防火效果
对在持荷状态下的7 mm直径CFRP筋试验件中间部位用火焰温度1000℃的高温火焰枪进行灼烧，如图6所示，其中图6(a)中筋材无保护，图6(b)中筋材包裹陶瓷纤维布，观测不同时间筋材的受力状态及筋材表面的温度变化，灼烧2 h后，进行破断拉伸试验，获得剩余强度。
表1为不同防护措施下筋材温度及持荷性能。可以看出，在无任何防护条件下，对拉伸应力水平1170 MPa条件下的CFRP筋用火焰温度1000℃的高温火焰枪进行灼烧，25 min后，筋材灼烧部位树脂热解，筋材断裂；采用45 mm厚度陶瓷纤维布与石棉包裹筋材，施加1170 MPa拉伸应力，经过1000℃火焰灼烧2 h，筋材表面温度最高分别为562℃与635℃，筋材高温部位树脂发生热解，没有发生断裂(图7)，剩余强度分别为1646 MPa与1249 MPa，图8为其破断试样；采用60 mm厚度石棉包裹筋材，施加1170 MPa拉伸应力，经过1000℃火焰灼烧2 h，筋材表面温度最高为170℃，筋材完好，没有发生断裂，剩余强度为3121 MPa，筋材基本没有发生损伤。
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图 6 持荷条件下CFRP筋阻燃防火措施对比Figure 6. Comparison on fire retardant measures of CFRP tendons under load conditions表 1 不同防护类型下CFRP筋材温度及持荷性能Table 1. Temperature and load carrying capacity of CFRP tendons under different protection typesProtection
typeProtection thickness/mm Burning time/min CFRP tendons temperature/℃ Stress level/MPa Test result Resident strength/MPa — — 25 1000 1170 Resin pyrolysis,
tendon tensile fracture— Ceramic fiber cloth 45 120 562 1170 Resin pyrolysis,
tendon is not fracture1646 Asbestos 45 120 635 1170 Resin pyrolysis,
tendon is not fracture1249 Asbestos 60 120 170 1170 The tendon is not damaged 3121 ![]()
图 7 CFRP筋材高温下树脂热解(562℃，2 h)Figure 7. Resin pyrolysis of tendons at high temperature (562℃, 2 h)![]()
图 8 树脂热解后CFRP筋材极限拉伸破断Figure 8. Ultimate tensile fracture of CFRP tendons after resin pyrolysis以上试验研究可以看出，包裹60 mm厚的石棉可以起到很好的阻燃防火效果，但是过厚的石棉必然影响索体直径，给CFRP索的盘卷带来困难，同时会改变索体表面原有的空气动力学特性，不方便应用。
2.2 阻燃防火涂层
选用一种阻燃防火涂层，刷在CFRP索股索体双层聚乙烯(PE)护套外表面，其中索股直径61 mm，PE护套厚度6 mm，阻燃防火涂层厚度2 mm，如图9所示。所用阻燃防火涂料层由基料丙烯酸乳液、膨胀催化剂聚磷酸铵、碳化剂季戊四醇、膨胀发泡剂三聚氰胺与氯化石蜡、颜料钛白粉、成膜助剂醇酯等组成。
在PE表面刷有2 mm阻燃防火涂层，并在索体PE内表面预埋测温线，用火焰温度1000℃的高温火焰枪对索股局部进行长达2 h的高温灼烧试验(图10)，阻燃防火涂料层发生膨胀并形成均匀而致密蜂窝状碳化层，保护双层PE护套不发生燃烧，使得缆索具有阻燃防火特性，PE护套仅发生软化。无阻燃防火涂层保护的索体5 min内PE护套燃烧殆尽，漏出索体(图11)。图12为2 mm阻燃防火涂层温度-时间曲线。可以看出，2 h灼烧索股PE内表面最高温度为206℃。
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图 11 无阻燃防火涂层聚乙烯(PE)燃烧Figure 11. Combustion of polyethylene (PE) sheath without fire retardant coating![]()
图 12 2 mm厚阻燃防火涂层温度-时间曲线Figure 12. Temperature-time curve of 2 mm thickness fire retardant coating2.3 CFRP索股表层不同位置处温度测定
为探究发生火灾时CFRP索股内部PE内筋材温度，将测温线置于不同位置处测量灼烧试验时各位置的温度(图13)，分别为索股PE内表面、距离PE内表面7 mm、距离PE内表面14 mm。图14为灼烧2 h索股内部不同位置处温度-时间曲线。可以看出，紧贴PE内表面的温度最高，为206℃，其次是测温线与PE内表层间隔7 mm处的温度(次外层筋材)，为156℃，温度最低的是与PE内表层距离14 mm处的温度(第三层筋材)，为100℃。
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图 14 CFRP索股不同位置处温度-时间曲线Figure 14. Temperature-time curves at different positions of CFRP cable strand3. 阻燃防火涂层耐火时间
针对阻燃防火涂层的不同厚度，试验研究在1000℃火焰灼烧下阻燃防火效果的持续性，索股规格同2.2节。图15为不同厚度阻燃防火涂层温度-时间曲线。可知无阻燃防火涂层防护，索股PE层5 min燃烧殆尽；0.3 mm厚度阻燃防火涂层可保护索股PE层20 min；1.4 mm厚度阻燃防火涂层可保护索股PE层160 min；刷有2 mm厚度阻燃防火涂层的索股在长达360 min的火焰灼烧下，PE内表面最高温度为245℃，PE层未发生破坏，仅发生软化，建议阻燃防火涂层厚度为2 mm。
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图 15 不同厚度阻燃防火涂层的温度-时间曲线Figure 15. Temperature-time curves of fire retardant coating with different thickness图16为2 mm厚度阻燃防火涂层的索股燃烧360 min试验过程的发泡过程。可以看出，随着火焰灼烧时间的增长，发泡层高度逐渐增大，发泡尺寸也逐渐增大，6 h熄火后形成一个6 cm×8 cm、高4 cm的发泡层，长达6 h的灼烧试验，PE内表面最高温度为245℃，熄火后，拨开厚厚的发泡层，PE护套仅发生软化。结合图15与图16，可以看出，燃烧前20 min为快速发泡升温阶段，发泡层快速增大，PE内表面温度从室温上升到196℃；20~140 min为稳定阶段，发泡层缓慢增大，PE内表面温度维持在203~209℃之间；140~360 min为动态平衡阶段，继续燃烧温度缓慢升高，燃烧至180 min，PE内表面温度达到216℃，阻燃防火涂层内层达到发泡温度开始发泡，发泡层高度增加，PE内表面温度下降，燃烧至240 min，PE内表面温度降至200℃，燃烧至280 min左右，发泡层表层开始发生热解，PE内表面温度升高至230℃左右，阻燃防火涂层内层达到发泡温度进一步发泡，发泡层高度持续增加，PE内表面温度下降，但随着发泡层表层热解，PE内表面温度又缓慢上升。
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图 16 2 mm厚度阻燃防火涂层的CFRP索股膨胀发泡过程Figure 16. Intumescent process of CFRP cable strand coated with 2 mm thickness fire retardant coating4. 结 论
(1) 碳纤维增强树脂复合材料(Carbon fiber reinforced polymer，CFRP)筋材高温剩余强度随温度升高呈线性下降趋势，210℃加热3 h，剩余强度最低为2245.8 MPa，比初始强度下降26.13%。
(2) CFRP筋材高温加热冷却后强度存在一定程度的可逆性恢复，剩余强度均能达到2800 MPa以上，但较原始强度略微下降，且经历温度越高剩余强度越低，最大下降幅度为6.13%。
(3) 对比3种阻燃防火措施，阻燃防火涂层具有较好的阻燃防火效果，2 h灼烧索股聚乙烯(PE)内表面最高温度为206℃，次外层筋材最高温度为156℃，第三层筋材最高温度为100℃，火灾2 h内，索股仍可承载，剩余强度≥2245 MPa。
(4) 阻燃防火涂层越厚防护时间越长，2 mm厚阻燃防火涂层的索股在长达360 min的火焰灼烧下，PE内表面最高温度为245℃，PE层未发生破坏，仅发生软化，建议阻燃防火涂层的厚度为2 mm。
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图 1 聚苯胺包覆碳点功能化锰钴金属氧化物(CoMn2O4/CDs/PANI)的合成路线
Figure 1. Synthetic route to polyaniline-coated carbon dot functionalized manganese cobalt metal oxide was synthesized by chemical polymerization (CoMn2O4/CDs/PANI)
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图 2 PANI和CMCx/PANI的(a) XRD谱图；(b) FT-IR谱图
Figure 2. (a) XRD patterns of PANI and CMCx/PANI; (b) FT-IR spectra
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图 3 (a-b) PANI、(c-d) CMC20%/PANI、(e-f) CMC50%/PANI的SEM
Figure 3. SEM of (a-b) PANI, (c-d) CMC20%/PANI, and (e-f) CMC50%/PANI
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图 4 CMC20%/PANI和CMC50%/PANI：(a) N2循环吸脱附和(b) 孔径分布曲线
Figure 4. (a) N2 cyclic adsorption desorption and (b) pore size distribution curves of CMC20%/PANI and CMC50%/PANI
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图 5 (a) pH对PANI、CMC10%PANI、CMC20%/PANI和CMC50%/PANI的吸附铀性能的影响(T = 298 K, m/V = 0.25 g/L, C0 = 100 mg/L)；(b) CMC20%/PANI Zeta电位；(c) 不同时间CMC20%/PANI对铀吸附性能(pH=5.0, T = 298 K, m/V = 0.25 g/L, C0 = 100 mg/L)和(d) 颗粒内扩散模型拟合曲线
Figure 5. (a) Effect of pH on the uranium adsorption performance of PANI, CMC10%PANI, CMC20%/PANI, and CMC50%/PANI (T = 298 K, m/V = 0.25 g/L, C0 = 100 mg/L); (b) Potential of CMC20%/PANI Zeta; (c) Uranium adsorption performance of CMC20%/PANI at different times (pH=5.0, T = 298 K, m/V = 0.25 g/L, C0 = 100 mg/L); (d) Fitting curve of intra particle diffusion model
qt—The adsorption capacity at an time point
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图 6 (a) CMC20%/PANI在不同初始浓度及温度下对铀酰离子的吸附性能；等温线拟合曲线(C0=20~400 mg/L, T=298~318 K, pH = 5.0, m/V = 0.25 g/L)；(b) lnK与1/T的关系
Figure 6. (a) The adsorption performance of CMC20%/PANI on uranyl ions at different initial concentrations and temperatures; Isotherm fitting curve (C0=20~400 mg/L, T=298~318 K, pH = 5.0, m/V = 0.25 g/L); (b) Relationship between equilibrium constant and reciprocal temperature
K—Thermodynamic equilibrium constant.
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图 7 CMC20%/PANI对不同金属离子的(a) 吸附容量；(b) 分配系数
Figure 7. (a) Influence of coexisting ions and (b) distribution coefficient of CMC20%/PANI
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图 8 (a) 不同解吸液的解析率；(b) 循环性能；(c) 循环后CMC20%/PANI的SEM图谱
Figure 8. (a) Resolution rates of different desorbing solutions; (b) Cycling performance; (c) The SEM of CMC20%/PANI after cycles.
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图 9 CMC20%/PANI吸附铀前后(a) FT-IR；(b) XRD；(c) SEM
Figure 9. (a) FT-IR; (b) XRD; (c)SEM of CMC20%/PANI before and after uranium adsorption
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图 10 CMC20%/PANI吸附铀前后 (a) U 4f；(b) N 1s；(c) C 1s；(d) O 1s；(e) Mn 2p；(f) Co 2p XPS精细谱图
Figure 10. CMC20%/PANI before and after uranium adsorption (a) U 4f; (b) N 1s; (c) C 1s; (d) O 1s; (e) Mn 2p; (f) Co 2p XPS fine spectrum
表 1 准一/二级动力学模型拟合参数
Table 1 Fitting parameters of pseudo first/second order kinetic models
Kinetic model qe/(mg-U/g-ads) k1/(min−1)/k2/(g·mg−1·min−1) R2 Pseudo-first-order kinetic model 277.8 0.2432 0.785 Pseudo-second-order kinetic model 286.7 0.0016 0.985 Notes: qe—Theoretical equilibrium adsorption capacity; k1—The quasi-first-order kinetic constant; k2—The quasi-second-order kinetic constant; R2—Correlation coefficient. 
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表 2 颗粒内扩散模型拟合参数
Table 2 Fitting parameters of intra particle diffusion model
T/K kp1 R12 kp2 R22 kp3 R32 298 19.184 0.947 3.473 0.805 0.855 0.109 Notes: kp—The diffusion constant in particles; R2—Correlation coefficient.
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表 3 CMC20%/PANI吸附铀酰离子的吸附等温模型拟合参数
Table 3 Fitting parameters of adsorption isotherm model for uranyl ions on CMC20%/PANI
Isothermal model Parameter 298 K 308 K 318 K Langmuir qe/(mg·g−1) 791.088 809.268 866.259 KL/(L·mg−1) 0.027 0.035 0.041 R2 0.951 0.943 0.952 Freundlich 1/n 0.396 0.363 0.357 KF/(L·g−1) 83.777 106.496 122.312 R2 0.825 0.789 0.803 Sips qe/(mg·g−1) 659.798 690.434 750.500 KS 0.041 0.049 0.058 m 1.674 1.728 1.611 R2 0.991 0.991 0.987 Notes: qe—Theoretical equilibrium adsorption capacity; KL—The saturated adsorption capacity of a single layer; R2—Correlation coefficient; 1/n—The adsorption strength; KF—The Freundlich's constant; Ks—The Sips constant related to the adsorption energy; m—The sips constant.
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表 5 各种吸附剂的铀吸附性能比较
Table 5 Comparison of adsorption capacity for U(VI) adsorption with various adsorbents
Adsorbents Time/min Adsorption Capacity/(mg·g−1) pH Cycle performance References C@CaTiO3 40 119.2 3.5 — [1] Zr-ATMPA 120 238.1 5 — [3] HAP/BTN 30 186.4 6 5/80% [7] CMPA-F-BDA 20 443 8 5/80% [13] Fe-PANI-GA 20 350.47 5.5 5/144.2~127.3 mg/g [22] LGSA 30 1162 8.5 5/94.2% [23] CS-AO-AMP 3600 620 7-9 4/90% [24] CMC20%/PANI 120 659.0 5 5/89.7% This work Notes: C@CaTiO3—Pomegranate peel carbon loaded CaTiO3; Zr-ATMPA—Organic zirconium phosphonate; HAP/BTN—Hydroxyapatite modified bentonite; CMPA-F-BDA—The modification of amino groups onto the fluorenone-functionalized conjugated microporous poly(aniline)s network; Fe-PANI-GA—Zero-valent iron-polyaniline-graphene aerogel ternary composite; LGSA—Surfactant assisted APTES functionalization of graphene oxide intercalated layered double hydroxide; CS-AO-AMP—Chitosan-based porous adsorbent with multifunctional amidoxime and phosphate groups.
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表 4 热力学参数
Table 4 Thermodynamic fitting parameters
T/K ΔGθ/(kJ·mol−1) ΔHθ/(kJ·mol−1) ΔSθ/(J·mol−1·K−1) 298 −3.612 13.874 58.677 308 −4.199 318 −4.785 328 −5.372 338 -5.959 Notes: ΔGθ—Gibbs free energy; ΔHθ—Enthalpy; ΔSθ—Entropy change.
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目的
核工业发展产生的含铀废水对人类健康和生态环境产生严重威胁。对含铀废水的有效化处理是核能绿色发展的重要保证。
方法采用化学聚合法合成了一种新型聚苯胺包覆碳点功能化锰钴金属氧化物(CMC20%/PANI)。吸附剂表面丰富的氧、氮基团为U(VI)的高效捕获提供活性位点。采用静态吸附法研究了材料去除溶液中U(VI)的性能。
结果在pH = 5、120 min，CMC20%/PANI对U(VI)的吸附容量达到285 mg/g。吸附过程符合准二级动力学和Sips模型，表明吸附剂对铀涉及单层和多层的化学吸附，并且Sips拟合的理论吸附容量为659.7 mg/g。吸附机制研究表明：静电吸引、孔扩散以及含氧、氮基团的络合配位作用成为CMC20%/PANI对U(VI)的主要去除机制。
结论本文通过化学聚合法合成的CMC20%/PANI对U(VI)具有高吸附容量、强选择性以及良好的重复利用性，使其有望成为未来处理实际含铀废水的潜力吸附剂。
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核能衍生的含铀废水对社会和生态造成严重威胁，对其有效化处理于人类健康和生态环境而言具有战略意义。锰钴金属氧化物(CoMn2O4)作为尖晶石氧化物的一种，主要由过渡金属元素组成，价格低廉、来源广泛。由于其元素组成可调、结构灵活、热/化学稳定性高，作为高效的铀吸附剂备受关注。然而，单一双金属氧化物作为作为吸附剂存在吸附容量低、活性位点不足和对U(VI)选择性差的问题。
本文通过化学聚合法制备了一种聚苯胺包覆碳点功能化的锰钴金属氧化物(CMC20%/PANI)。基于生物质碳点(CDs)，通过水热法对CoMn2O4进行功能化，增强金属间相互作用，改善了CoMn2O4的结构和物理化学性质，从而显著增强了其吸附性能。同时聚苯胺在吸附剂表面的原位聚合包覆，克服了CoMn2O4在吸附过程中吸附容量低，U(VI)的吸附活性位点不足等问题。所制得的CMC20%/PANI在pH=5、120 min内对U(VI)的最大理论吸附容量达到659.7 mg/g，并且对U(VI)的选择性超过实验共存离子中最高选择性的9倍，以及在循环五次后对U(VI)的吸附容量仍能达到387 mg·g-1。CMC20%/PANI对U(VI)的高吸附容量、强选择性以及良好的重复利用性，使其有望成为未来处理实际含铀废水的潜力吸附剂。
CMC20%/PANI吸附剂：(a) 等温线研究；(b) 动力学研究；(c) 共存离子对吸附U(VI)的影响；(d) 循环吸脱附
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