Study On Removal Of Nickel And Cyanide From Wastewater By Synthesizing Layer Double Hydroxides In-situ

The possibility of removing nickel and complex of cyanide with heavy metal from wastewater by synthesizing layer double hydroxide (LDH) in situ was studied . The effects of pH value, reaction time, Mg²⁺/Al³⁺ molar ratio and initial concentration of Ni²⁺ and Fe(CN)₆^3- on removal efficiency and the removal theory by X-ray diffraction were studied. Compared synthesizing Layer double hydroxides in-situ with Chemistry precipitation. The results show:(1) The effects on removal efficiency are pH value, Mg²⁺/Al³⁺molar ratio and initial concentration of Ni²⁺, and the fisrt is pH value, the second is initial concentration of Ni²⁺, the last is Mg²⁺/Al³⁺molar ratio. The maximal removal efficiency of Ni²⁺ obtained when the pH was 8.5, and Mg²⁺/Al³⁺molar ratio range from 1 to 2 , at this time Mg²⁺and Al³⁺ use efficiency are very high . X-ray diffraction and infrared spectrometry of the precipitate of the sample approved that the solids are Layer double hydroxides crystal. The technique of synthesizing Layer double hydroxides in-situ can remove nickel from wastewater effectively at lower pH value (pH≤9), but the technique of chemistry precipitation can not remove nickel. At high pH (pH≥S10) two techniques can remove nickel effectively, but to the removal efficiency and plain sedimentation, synthesizing Layer double hydroxides in-situ is better than chemistry precipitation.(2) Removing complex of cyanide and heavy metal is feasible by synthesizing LDH in situ The key factor affecting the removal of Fe(CN)₆^3- is pH value, the maximal removal efficiency obtained when the pH was 9.5. The precipitate of the sample was analyzed by X-ray diffraction, the results show that the precipitate is the LDH crystal. It indicates that Fe(CN)₆^3- is embedded into the structure of the LDH layers. The products of removing Fe(CN)₆^3- from wastewater by synthesizing LDH in situ have magnetic behaviour by calcinated at 400℃, that is to say the products of removing Fe(CN)₆^3- by synthesizing LDH can make ferrite magnetic material, realize changing the wastage to utility.