Zhu Donghai, Zhu Jiachen, Li Ping, Lan Shengjie
State Key Laboratory of Plateau Ecology and Agriculture, School of Chemical Engineering, Qinghai University Xining 810016 PR China
RSC Adv. 2024 Mar 1;14(11):7329-7337. doi: 10.1039/d3ra08040d. eCollection 2024 Feb 29.
In this study, magnesium hydroxide (MH) particles with distinct morphologies were obtained through direct precipitation and subsequent hydrothermal treatment with various magnesium salts. The synthesized products were systematically characterized and utilized for the removal of Pb(ii) ions from aqueous solutions. The adsorption process of Pb(ii) by two different MH structures, namely flower globular magnesium hydroxide (FGMH) and hexagonal plate magnesium hydroxide (HPMH), adhered to the Langmuir isotherm and pseudo-second-order model. FGMH exhibited higher Pb(ii) removal capacity (2612 mg g) than HPMH (1431 mg g), attributable to the unique three-dimensional layered structures of FGMH that provide a larger surface area and abundant active sites. Additionally, metallic Pb was obtained by recycling the adsorbed Pb(ii) through acid dissolution-electrolysis. Furthermore, Pb(ii) removal mechanisms were investigated by analyzing adsorption kinetics and isotherms, and the adsorbed products were characterized. Based on the findings, the removal process occurs in two key stages. First, Pb(ii) ions bind with OH ions on the surface upon diffusing to the MH surface, resulting in Pb(OH) deposits . Concurrently, Mg(ii) ions diffuse into the solution, substituting Pb(ii) ions in the MH lattice. Second, the resultant Pb(OH), which is unstable, reacts with CO dissolved in water to yield Pb(CO)(OH). Therefore, owing to its outstanding Pb(ii) adsorption performance and simple preparation method, FGMH is a promising solution for Pb(ii) pollution.
在本研究中，通过直接沉淀法以及随后用各种镁盐进行水热处理，获得了具有不同形态的氢氧化镁（MH）颗粒。对合成产物进行了系统表征，并将其用于从水溶液中去除Pb（II）离子。两种不同的MH结构，即花球状氢氧化镁（FGMH）和六方片状氢氧化镁（HPMH）对Pb（II）的吸附过程符合朗缪尔等温线和准二级模型。FGMH对Pb（II）的去除能力（2612 mg/g）高于HPMH（1431 mg/g），这归因于FGMH独特的三维层状结构，该结构提供了更大的表面积和丰富的活性位点。此外，通过酸溶解-电解回收吸附的Pb（II）得到了金属Pb。此外，通过分析吸附动力学和等温线研究了Pb（II）的去除机制，并对吸附产物进行了表征。基于这些发现，去除过程分两个关键阶段进行。首先，Pb（II）离子扩散到MH表面时与表面的OH离子结合，形成Pb（OH）沉积物。同时，Mg（II）离子扩散到溶液中，取代MH晶格中的Pb（II）离子。其次，生成的不稳定的Pb（OH）与水中溶解的CO反应生成Pb（CO）（OH）。因此，由于其出色的Pb（II）吸附性能和简单的制备方法，FGMH是解决Pb（II）污染的一种有前景的解决方案。
