焙烧层状氢氧化镁铝对水溶液中亚硝酸盐的吸附脱除

ADSORPTIVE REMOVAL OF NO_2^- FROM AQUEOUS SOLUTION BY CALCINED Mg-Al LAYERED DOUBLE HYDROXIDES

通过静态吸附实验,研究了焙烧层状氢氧化镁铝(Mg-AlCLDH)对水溶液中NO2-的吸附脱除性能,并用粉末X射线衍射对Mg-AlCLDH吸附前后的结构进行了表征.结果表明,Mg-AlCLDH可有效脱除水溶液中的亚硝酸盐(NO2-),对NO2-的脱除是通过"结构记忆"效应实现的.当NO2-初始浓度高达15mgN·l-1时,经0.10gMg-AlCLDH处理后,溶液中残余浓度小于1mgN·l-1.在293—323K温度范围内,NO2-在Mg-AlCLDH上的饱和吸附量为17.24—29.94mgN·g-1,吸附量明显高于其它吸附剂;吸附量随温度的升高而增大,表现为吸热吸附;吸附过程符合Langmuir线性等温方程式.吸附速率随温度的升高而迅速增大,伪二级动力学方程可用来描述其吸附动力学过程;吸附Ea为109.94kJ·mol-1,Mg-AlCLDH对NO2-的吸附主要是化学吸附·Mg-AlCLDH对NO2-的脱除率基本不受溶液初始pH值的影响,吸附量随离子强度的增大而减小.正交实验结果显示溶液初始浓度是影响吸附量的最主要因素.

The calcined Mg-Al layered double hydroxides （ Mg-Al CLDH） for removal of NO2^- from aqueous solution was investigated. The results show that Mg-Al CLDH is an effective adsorbent for the removal of NO2^- from aqueous solution. The mechanism is followed ＂ memory effect＂ . At the initial concentration of 15 mgN · l^-1 for NO2^- , the equilibrium concentration is lower than 1 mgN · l^-1. The maximum adsorption capacities of NO2^- on Mg-Al CLDH from 293 to 323 K are 17.24 to 29.94 mgN · g^-1, which are much higher than those obtainedfor other adsorbents. The adsorption processes are endothermic. The adsorption data are well fitted to the Langmuir isotherm model. The adsorption rate is increased considerably with temperature. The activation energy is 109.94 kJ · mol^-1. The adsorption processes are chemical adsorption and well fitted with the pseudosecond-order kinetic model. The removal rate is influenced insignificantly at the initial pH of 4.0 to 9.0. The adsorption capacities are decreased with the increasing concentrations of competitive ions. The orthogonal array design shows that the initial concentration of solution is the most important factor.