Department of Chemical Engineering, Faculty of Engineering, Thammasat University, Pathumthani, Thailand.
Environ Sci Pollut Res Int. 2011 Jul;18(6):857-64. doi: 10.1007/s11356-011-0442-3. Epub 2011 Jan 21.
The nano-scale zero-valent iron (NZVI) was used for the removal of arsenite (As(III)) and arsenate (As(V)) in aqueous solution. Batch experiments were conducted to investigate the effects of initial pH, initial arsenic concentration, dissolved oxygen (DO), and ratio of As(III)/As(V) on arsenic removal.
The NZVI synthesized by using NaBH4 and FeCl3 was put into use right after its synthesis. The arsenic treatment system of recirculation mode consists of a reactor with a liquid volume of 4.4 L, which provides dual function of reactants reaction and particles settling in one unit.
Consequently, the pseudo-first order rate equations can be used to describe the removal kinetics for As(V) at pH 4 and 7, while the pseudo-second order reaction was observed for As(V) at pH 9 and As(III) at all pH's studied. Arsenic removal rates of both As(V) and As(III) were lower in the system with lower DO. The rate of As(III) removal decreased with the increase of its initial concentration. In contrast, the removal rate of As(V) still remained significantly high as its initial concentration increased.
This study reveals that low pH and high DO will favor arsenic removal. With the mixture of As(III) and As(V), the total arsenic was removed faster than solution containing As(III) or As(V) alone. In addition, the mixture with higher fraction of As(V) resulted in higher arsenic removal.
纳米零价铁（NZVI）被用于去除水溶液中的亚砷酸盐（As(III)）和砷酸盐（As(V)）。通过批次实验研究了初始 pH 值、初始砷浓度、溶解氧（DO）以及 As(III)/As(V) 比值对砷去除的影响。
使用 NaBH4 和 FeCl3 合成的 NZVI 在合成后立即使用。采用循环模式的砷处理系统由一个 4.4 L 液体体积的反应器组成，该反应器在一个单元中同时提供反应物反应和颗粒沉降的双重功能。
因此，在 pH 4 和 7 下，可以使用准一级速率方程来描述 As(V)的去除动力学，而在 pH 9 下观察到了准二级反应，而在所有研究的 pH 值下均观察到了 As(III)。在 DO 较低的系统中，As(V)和 As(III)的去除速率较低。As(III)的去除速率随着其初始浓度的增加而降低。相比之下，As(V)的去除速率仍然保持显著高，即使其初始浓度增加。
本研究表明，低 pH 值和高 DO 将有利于砷的去除。对于 As(III)和 As(V)的混合物，总砷的去除速度比单独含有 As(III)或 As(V)的溶液更快。此外，具有较高比例 As(V)的混合物会导致更高的砷去除率。
