天然磁铁矿化学改性及其在水体除砷中的应用

Chemical Modification of Natural Magnetite and Its Application in Arsenic Removal from a Water Environment

铁氧化物及其复合氧化物(如菱铁矿、水铁矿)的表面电荷高、比表面积大,在特定条件下对亚砷酸盐和砷酸盐有较强的结合能力和亲和性,以铁氧化物作为吸附剂处理高砷水已经成为研究热点之一。天然磁铁矿的主要成分为Fe_3O_4,但其本身活性较弱,直接应用于处理高砷水的除砷率低。本文对天然磁铁矿采取酸化、碱化、不同温度灼烧、不同灼烧时间等简易的方法进行改性,达到有效去除水中砷的目的。实验结果表明:经0.5 mol/L盐酸浸泡、150℃灼烧10 min的改性磁铁矿分别处理As(Ⅲ)溶液和As(Ⅴ)溶液时,As(Ⅴ)去除率达98%,吸附能力显著增强,达到预期目标;溶液中As(Ⅲ)浓度从1000μg/L下降到250μg/L,去除率达75%,即As吸附能力明显优于未改性的天然磁铁矿,与其他改性铁矿除砷能力相近,而改性方法更加简便、易行。本文研究的改性天然磁铁矿吸附剂为控制高砷水的砷含量提供了一种切实可用的吸附材料。

Iron oxides and their complex oxides such as siderite and ferrihydrite have high surface charge and specific surface area,which have strong binding capacity and affinity for arsenite and arsenate under specific conditions. Natural magnetite,mainly consisting of Fe_3O_4,has low activity itself,and is not efficient for direct treatment of high arsenic water. Reported in this paper,natural magnetite is modified by acidification,alkalization,and calcined at different temperatures for different periods,in order to enhance arsenic removal from water. Experimental results show that the modified magnetite acidified in 0. 5 mol / L hydrochloric acid and calcined at 150℃ for 10 min, has high removal efficiencies for both As（Ⅲ） and As（Ⅴ）. Removal efficiency was98% for As（Ⅴ）,whereas the removal efficiency was 75% for As（Ⅲ） with concentration decreases from 1000 μg / L to 250μg /L（in Fig. 2）. The modified natural magnetite has stronger adsorption capacity for As than natural magnetite,and is identical to other modified iron minerals. In addition, the modification method is simple and convenient. Therefore,the modified natural magnetite would be a potential adsorbent for controlling arsenic content in high arsenic water.