Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, China.
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, China.
Environ Pollut. 2019 Jan;244:783-791. doi: 10.1016/j.envpol.2018.10.062. Epub 2018 Oct 24.
The heavy metal ion adsorption performance of birnessite (a layer-structured manganese oxide) can be enhanced by decreasing the Mn average oxidation state (Mn AOS) and dissolution-recrystallization during electrochemical redox reactions. However, the electrochemical adsorption processes of heavy metal ions by tunnel-structured manganese oxides are still enigmatic. Here, tunnel-structured manganese oxides including pyrolusite (2.3 Å × 2.3 Å tunnel), cryptomelane (4.6 Å × 4.6 Å tunnel) and todorokite (6.9 Å × 6.9 Å tunnel) were synthesized, and their electrochemical adsorptions for Cd were performed through galvanostatic charge-discharge. The influence of both supporting ion species in the tunnel and tunnel size on the electrochemical adsorption performance was also studied. The adsorption capacity of tunnel-structured manganese oxides for Cd was remarkably enhanced by electrochemical redox reactions. Relative to K in the tunnel of cryptomelane, the supporting ion H was more favorable to the electrochemical adsorption of Cd. With increasing initial pH and specific surface area, the electrochemical adsorption capacity of cryptomelane increased. The cryptomelane electrode could be regenerated by galvanostatic charge-discharge in NaSO solution. Due to the differences in their tunnel size and supporting ion species, the tunnel-structured manganese oxides follow the order of cryptomelane (192.0 mg g) > todorokite (44.8 mg g) > pyrolusite (13.5 mg g) in their electrochemical adsorption capacities for Cd.
层状结构的锰氧化物（水钠锰矿）可以通过降低 Mn 平均价态（Mn AOS）和电化学氧化还原过程中的溶解-再结晶来增强对重金属离子的吸附性能。然而，隧道结构的锰氧化物的电化学吸附重金属离子的过程仍然很神秘。在这里，合成了包括软锰矿（2.3 Å×2.3 Å 隧道）、钾钠锰矿（4.6 Å×4.6 Å 隧道）和斜方锰矿（6.9 Å×6.9 Å 隧道）在内的隧道结构的锰氧化物，并通过恒电流充放电对它们的电化学吸附 Cd 性能进行了研究。还研究了隧道中支撑离子种类和隧道大小对电化学吸附性能的影响。隧道结构的锰氧化物的电化学氧化还原反应显著增强了对 Cd 的吸附能力。与钾在钾钠锰矿隧道中的情况相比，支撑离子 H 更有利于 Cd 的电化学吸附。随着初始 pH 值和比表面积的增加，钾钠锰矿的电化学吸附容量增加。在 NaSO 溶液中通过恒电流充电/放电可以使钾钠锰矿电极再生。由于隧道大小和支撑离子种类的差异，隧道结构的锰氧化物对 Cd 的电化学吸附容量按如下顺序排列：钾钠锰矿（192.0 mg g）>斜方锰矿（44.8 mg g）>软锰矿（13.5 mg g）。
