Qin Zhangjie, Chen Xinmin, Ouyang Nanqi, Lan Shuai, Jiang Guanjie, Zhang Junxia, Zhang Qin
Key Laboratory of Poyang Lake Basin Agricultural Resource and Ecology of Jiangxi Province, College of Land Resource and Environment, Jiangxi Agricultural University Nanchang 330045 China
RSC Adv. 2019 Aug 19;9(45):25951-25956. doi: 10.1039/c9ra03332g.
Birnessite is one of the most important manganese oxides that can control the geochemical behaviors of pollutants or can be applied to form industrial products. Many studies have been conducted on the synthesis of hexagonal birnessite because different synthesis methods can affect the structural, morphological, and physicochemical properties of hexagonal birnessite. However, there are still some defects in these synthesis methods. Therefore, a new synthesis method that is rapid, simple, and low-cost was proposed in this study involving the reduction of KMnO by HO in a HSO solution without controlling the pH, temperature and pressure. Using a series of XRD, chemical composition, AOS, SSA, SEM, FTIR, and TGA analyses, Bir-HO was found to have lower crystallinity than Bir-HCl. However, the AOS and SSA of Bir-HO were 3.87 and 103 m g higher than those of Bir-HCl, , 3.70 and 22 m g, respectively. Moreover, both Bir-HO and Bir-HCl had similar particle morphology and thermal stability; in addition, the maximum adsorption content of Pb on Bir-HO (∼3006 mmol kg) was ∼30% greater than that on Bir-HCl (∼2285 mmol kg) at pH 5.5; this indicated that the adsorption of Pb on Bir-HO was better and belonged to a pseudo-second-order model. All the abovementioned results indicate that Bir-HO synthesized herein using the proposed synthesis method can have large application value.
水钠锰矿是最重要的锰氧化物之一，它能够控制污染物的地球化学行为，或可用于制造工业产品。由于不同的合成方法会影响六方水钠锰矿的结构、形态和物理化学性质，因此人们对六方水钠锰矿的合成进行了大量研究。然而，这些合成方法仍存在一些缺陷。因此，本研究提出了一种快速、简单且低成本的新合成方法，即在不控制pH值、温度和压力的情况下，在硫酸溶液中用草酸还原高锰酸钾。通过一系列XRD、化学成分、阳离子交换容量（AOS）、比表面积（SSA）、扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）和热重分析（TGA）发现，水钠锰矿-草酸（Bir-HO）的结晶度低于水钠锰矿-盐酸（Bir-HCl）。然而，Bir-HO的AOS和SSA分别比Bir-HCl高3.87和103 m²/g，Bir-HCl的AOS和SSA分别为3.70和22 m²/g。此外，Bir-HO和Bir-HCl具有相似的颗粒形态和热稳定性；另外，在pH 5.5时，Bir-HO对铅的最大吸附量（约3006 mmol/kg）比Bir-HCl（约2285 mmol/kg）高约30%；这表明Bir-HO对铅的吸附效果更好，且符合准二级模型。上述所有结果表明，采用本研究提出的合成方法制备的Bir-HO具有较大的应用价值。
