FeMn-Cl-LDHs水滑石对水中As(Ⅲ)的固定和机理研究

Immobilization and mechanism of As(Ⅲ)in water by FeMn-Cl-LDHs hydrotalcite

砷(As)污染被认为是当前世界最严峻的环境问题之一,许多国家都存在着不同程度的As污染。砷是一种有毒元素,主要以As(Ⅴ)和As(Ⅲ)2种价态的无机物形态存在于自然环境中。相比As(Ⅴ),As(Ⅲ)的危害性更大。通过共沉淀法构建铁锰基水滑石(FeMn‒Cl‒LDHs),研究了其对水中As(Ⅲ)的固定及其机理。试验结果表明,在pH为2~8范围内,FeMn‒Cl‒LDHs对As(Ⅲ)的去除率保持在97%左右;共存离子SiO_(3)^(2-)、PO_(4)^(3-)、CO_(3)^(2-)和As(Ⅲ)存在竞争吸附,而Ca^(2+)、Mg^(2+)、NO_(3)^(-)和SO_(4)^(2-)对As(Ⅲ)的去除影响较小。FeMn‒Cl‒LDHs对As(Ⅲ)的去除过程符合拟二级动力学模型和Langmuir模型,在298 K时,FeMn‒Cl‒LDtHs对As(Ⅲ)的最大吸附量为61.86 mg/g。FeMn‒Cl‒LDHs对As(Ⅲ)的去除机理可能存在氧化还原作用、离子交换和络合。经过5次吸附‒解吸试验,FeMn‒Cl‒LDHs对水中As(Ⅲ)的去除率仍保持在90%以上。FeMn‒Cl‒LDHs对水中As(Ⅲ)的去除和毒性控制具有良好的环境应用潜力。

Arsenic(As)pollution is considered to be one of the most serious environmental problems in the world at present,which exists in many countries to varying degrees.Arsenic is a toxic element that exists in the natural environment mainly in the form of inorganic substances in two valence states,As(Ⅴ)and As(Ⅲ).Compared with As(Ⅴ),As(Ⅲ)is more harmful.In present work,FeMnbased hydrotalcite(FeMn‒Cl‒LDHs)was constructed by coprecipitation method to investigate the immobilization and mechanism of As(Ⅲ)in water.The test results showed that the removal rate of As(Ⅲ)by FeMn‒Cl‒LDHs was about 97%in the range of pH 2‒8.The existing ions of SiO_(3)^(2-),PO_(4)^(3-),CO_(3)^(2-) had competitive adsorption with As(Ⅲ),while Ca^(2+),Mg^(2+),NO_(3)^(-) and SO_(4)^(2-) had little effect on the As(Ⅲ)removal.The adsorption process of As(Ⅲ)by FeMn‒Cl‒LDHs was in accordance with the pseudo second order kinetic model and Langmuir isotherm.The maximum adsorption capacity was 61.86 mg/g at 298 K.The mechanism of As(Ⅲ)removal by FeMn‒Cl‒LDHs might be redox,ion exchange and complexation.After five adsorption‒desorption experiments,the removal rate of As(Ⅲ)in water by FeMn‒Cl‒LDHs remained above 90%,which indicated that FeMn‒Cl‒LDHs had good potential for environmental application in the removal and toxicity control of As(Ⅲ)in water.