Ultra-thin iron phosphate nanosheets for high efficient U(VI) adsorption

Abstract

In this study, the ultra-thin iron phosphate Fe7(PO4)6 nanosheets (FP1) with fine-controlled morphology, has been designed as a new two-dimensional (2D) material for uranium adsorption. Due to its unique high accessible 2D structure, atom-dispersed phosphate/iron anchor groups and high specific surface area (27.77 m2·g−1), FP1 shows an extreme-high U(VI) adsorption capacity (704.23 mg·g−1 at 298 K, pH = 5.0 ± 0.1), which is about 27 times of conventional 3D Fe7(PO4)6 (24.51 mg·g−1-sample FP2) and higher than most 2D absorbent materials, showing a great value in the treatment of radioactive wastewater. According to the adsorption results, the sorption between U(VI) and FP1 is spontaneous and endothermic, and can be conformed to single molecular layer adsorption. Based on the analyses of FESEM, EDS, Mapping, FT-IR and XRD after adsorption, the possibile adsorption mechanism can be described as a Monolayer Surface Complexation and Stacking mode (MSCS-Mode). Additionally, the research not only provide a novel preparing method for 2D phosphate materials but also pave a new pathway to study other two-dimensional adsorption materials.

Structure, morphology, size and application of iron phosphate

“…Ultra-thin iron phosphate nanosheets, with some mesoporous morphologies, were designed as a new 2D material with high surface area of 27.77 m 2 g −1 [41].…”

“…The sorption of U(VI) is mainly dominated by inner-sphere surface com-plexation, which was a spontaneous and endothermic process. The ultra-thin iron phosphate nanosheets with finecontrolled morphology were used as a new 2D material for uranium adsorption [41]. It shows an extreme-high U(VI) adsorption capacity of 704.23 mg g −1 , about 27 times of conventional 3D material (24.51 mg g −1 ) and higher than most 2D absorbent materials.…”

Preparation of aluminum sludge composite gel spheres and adsorption of U(IV) from aqueous solution

“…9). The Langmuir isothermal model assumes that the adsorbent material is a homogeneous monolayer adsorption of the target, while the Freundlich isothermal model assumes that the adsorbent material has heterogeneous adsorption energy (Wang et al 2019a). The isotherm model is based on the following mathematical equations (5)-(7), and the specific parameters are shown in Table 2:…”

Construction of Novel Three Dimensionally Macroporousg-C3N4for Efficient Adsorption/Photocatalytic Reduction of U(VI)

“…图 4(a)为吸附动力学曲线, 从图中可以看出在 吸附初期吸附速率快; 当吸附持续 50 min 以上时, 吸附速率趋于平缓; 当吸附 100 min 以上时, 吸附 基本达到平衡。这是由于在吸附初始阶段, 吸附剂 表面有大量的可用吸附位点, 而当吸附进行到一定 程度时, 可用吸附位点减少导致吸附速率降低。其 中块体 g-C 3 N 4 本身紧密堆积, 造成活性位点少, 进 而表现出较低的吸附容量; 而三维大孔 g-C 3 N 4 具有 三维大孔良好的开放结构和较多的活性位点, 表现 出高效吸附的能力。为了深入分析吸附动力学过程, 用准一级和准二级动力学模型对实验数据进行拟合, 拟合公式如下 [33][34][35][36] : Fig. 4 (a) Adsorption kinetics and (b) adsorption isotherms for U(VI) on bulk g-C 3 N 4 and 3D macropoous g-C 3 N 4 pH=5.0±0.1, T=293 K, m/V=0.5 g/L The insert in (a) is the pseudo-second-order kinetic plots 刻的吸附量, k 1 (min -1 )和 k 2 (g/(mg·min))分别代表准 一级和准二级动力学常数。准二级动力学模型拟合 结果如图 4(a)中插图和表 1 所示, 可知准二级动力 学的拟合度系数(R 2 )高于准一级动力学的, 因此吸 附过程更接近准二级动力学模型。 块体 g-C 3 N 4 和三维大孔 g-C 3 N 4 对不同浓度 U(VI) 的吸附等温线示于图 4(b)。由图中的吸附等温线可 以看出, 三维大孔 g-C 3 N 4 对 U(VI)的吸附能力远好 于块体 g-C 3 N 4 。为了进一步研究溶液初始浓度与吸 附量的关系, 利用 Langmuir 和 Freundlich 等温吸附 模型对实验结果进行分析, 拟合公式如下 [37][38] :…”