Ferrous Ldh Removal Of The Adsorption Mechanism Of Arsenic In The Water Environment

China is facing a serious situation of water environment, water pollution and water resources become increasingly growing shortage of water in China's existing environmental problems are two main aspects.Arsenical water pollution refers to the water pollution that leaded by arsenic or arsenical compounds, it can be divided into two classes:natural pollution and man-made pollution, and the latter is more serious than the former. The main arsenical man-made pollution resource is the industrial sewage which contains arsenic or arsenical compounds. Generally the organisms who drink arsenic exceed water in a long term can get arseniasis and be jeopardized directly or indirectly, so developing efficient treatment and understanding arsenic behavior in environment are both major public health issues gaining in creasing attention in recent years.Based on the theories of adsorption method and Ion exchange method, the paper prepared three types of layered double hydroxides containing ferric iron including Zn-Fe-LDH, Mg-Fe-LDH, Mn-Fe-LDH to remove arsenic, and studied their morphologies and elemental compositions and the adsorption property of arsenic(?)emoval and the dynamic characteristic of arsenic adsorption onto layered double hydroxides, discussed exploratory process for the treatment of arsenic, in addition to study the mechanism of different divalent metal ions and trivalent metal ion in layered double hydroxides to remove arsenic.The experimental results were as follows:the synthetic method of three types of LDHs is easy to operate and apply to practice, the LDHs is a convenient and practical materials to to remove arsenic and arsenical compounds. The equilibrium sorption model for arsenic adsorption on three types of LDHs can be described by Langmuir mode, and the coefficients of determination are all above 0.97.under the same pH value conditions, the adsorption capacity of the three types of LDHs is like this:Q(Mn-Fe-LDH)>Q(Zn-Fe-LDH)>Q(Mg-Fe-LDH).Based on the Langmuir mode, the maximum arsenic adsorption of Mn-Fe-LDH is 2259.9ug/g. And the results show that:the three kinds of LDH in the treatment of arsenic water for pH range is wider, the SO42-, Cl- have no influence of water, but CO32- in water had significant inhibitory effect to the LDH.The element content and chemical composition of three types of LDHs are roughly estimated, and they each has two metal ions active center as follow:Fe, Zn;Fe, Mg;Fe, Mn, so that the LDHs can coordinate with arsenite anions and adsorb arsenic or arsenical compounds intensively. The different kinds of divalent metal ions has different affinity on arsenite anions.For instance, when the Mg-Fe-LDH remove arsenite anions,MgO,Mg(OH)2 are all microsolubility,so the stability of the Mg-Fe-LDH can be weakened, and the arsenite anions which has been adsorbed can be dissolved out again. When the Zn-Fe-LDH remove arsenite anions, the Zn(OH)2 is amphoteric compound and insoluble substances, so it's better than the Mg-Fe-LDH. When the Mn-Fe-LDH remove As(V), the hydrates of Mn has upstanding oxidation on arsenite anions, and the the typical laminated structure of Mn-Fe-LDH can adsorb and fix the arsenate anions to remove the arsenic or arsenical compounds in drinking water.The mechanism of the three types of LDHs to remove arsenic are mainly through the way of ion exchange and adsorption. To analyze and discuss in theory and to test and verify by experiments, the result proved that based on the way of ion exchange and adsorption to remove e arsenic by LDH is an effective arsenic removal method, and it is economical and practical technology valuable to popularize in high-Arsenic water area.