天然含铁矿物对砷的吸附效果及机制

Adsorption and Mechanism of Arsenic by Natural Iron-containing Minerals

自然界中丰富的含铁矿物作为天然的铁氧化物,可作为一类修复材料用于砷污染水体和土壤稳定化修复.本文通过吸附-解吸附实验对比研究了天然赤铁矿、天然褐铁矿、天然菱铁矿、天然钛铁矿、天然磁铁矿、Fe2O3、Fe3O4及铁锰双金属材料(FMBO)对砷的吸附-解吸特性,结合光谱学手段研究其作用机制.吸附实验结果表明,9种含铁材料对As(Ⅲ)和As(Ⅴ)的吸附过程更符合准二级动力学方程和Langmuir方程,表明反应机制主要为单层化学吸附作用.其中,FMBO对As的吸附效率和吸附容量远高于其余材料,天然含铁矿物中褐铁矿对As吸附效果表现最好,对As(Ⅲ)和As(Ⅴ)的吸附容量分别为3.96mg·g^-1和2.99mg·g^-1.光谱学手段表明天然褐铁矿中含有较为丰富的针铁矿等弱结晶态矿物成分,具有相对丰富的砷吸附位点,是一种具有潜在修复能力的天然材料.

Natural iron-containing minerals present in the geosphere in the form of crystalline minerals can be used as adsorption material for removal of arsenic from wastewater and remediation of arsenic-contaminated soils.In this paper,the adsorption and desorption of arsenic onto different iron-containing materials including hematite,limonite,siderite,ilmenite,magnetite,Fe2O3 , Fe3O4 ,and Fe-Mn binary oxide (FMBO) were studied in laboratory experiments.The mechanism of arsenic adsorption was analyzed by scanning electron microscopy (SEM),X-ray diffraction (XRD),and fourier transform infrared spectroscopy (FTIR).The results showed that arsenic adsorption is fitted by pseudo-second-order kinetics and the Langmuir isotherm model for almost all adsorbents, suggesting monolayer adsorption of arsenic onto the minerals.The sorption efficiency and capacity of arsenic by FMBO are much higher than those of other materials.Furthermore,limonite has high sorption efficiencies for both As(Ⅲ) and As(Ⅴ) among the natural ironcontaining minerals,and their adsorption capacities are 3.96 mg·g^-1 and 2.99 mg·g^-1,respectively.The XRD results showed that natural limonite contains a large number of weak crystalline mineral components such as goethite,which can provide relatively abundant arsenic adsorption sites.Thus,limonite appears to be the most suitable natural mineral for arsenic adsorption.