摘要
通过间歇式批实验和动力学实验研究了不同pH条件下磷酸盐在镁铝双氢氧化物(Mg-Al-LDH)、钠基膨润土(Na-Mt)及镁铁铝改性膨润土(Mg-Al-Mt、Fe-Mt和Fe-Al-Mt)的吸附特征。结果表明,在pH4.5～9.0范围内,随着pH的升高,Na-Mt,Fe-Mt和Fe-Al-Mt3种矿物对磷的吸附率相应减少,镁铝双氢氧化物对磷的吸附率有所增加;Mg-Al-LDH、Fe-Mt和Fe-Al-Mt的对磷吸附率约为95%,比Mg-Al-Mt高40%,比Na-Mt高80%。用Langmuir方程描述磷的等温吸附过程,最大吸附容量(Qm)大小顺序为Fe-Al-Mt>Fe-Mt>Mg-Al-LDH>Mg-Al-Mt>Na-Mt,b值大小依次为Mg-Al-LDH>Fe-Mt>Fe-Al-Mt>Mg-Al-Mt>Na-Mt,最大缓冲容量(Qmb)以Mg-Al-LDH的为最大,Na-Mt的为最小;Freundlich等温吸附方程参数KF代表相对吸附容量,以Mg-Al-LDH的KF值最高,依次是Fe-Mt、Fe-Al-Mt和Mg-Al-Mt,Na-Mt的KF值最小,这与Qmb的结果一致;决定系数(R2)表明,Langmuir等温吸附方程能更好地拟合铁改性蒙脱土和铁铝改性蒙脱土,而Freundlich方程对钠蒙脱土,双氢氧化物和镁铝改性蒙脱土的拟合效果要好。磷酸盐吸附过程分为快反应和慢反应,用动力学实验数据进行拟合,准二级动力学方程能够更好的拟合改性蒙脱土和Mg-Al-LDH对磷的动力学吸附数据,其决定系数为0.999;Elovich方程拟合改性蒙脱土磷酸盐的吸附数据也有很好的相关性(R2为0.89～0.94)。Na-Mt矿物磷酸盐的吸附用抛物线扩散方程描述最为合适,原因可能是磷酸盐镶嵌在矿物层间是一个扩散过程,不涉及化学吸附过程。
Characteristics of phosphate adsorption on Mg-Al layer double hydroxide（Mg-Al LDH） and Na-montmorillonite（Na-Mt） and Mg/Fe/Al modified montmorillonite（Mg-Al-Mt and Fe-Mt and Fe-Al-Mt） were studied by batch adsorption and kinetic experiments at different pH values.The results indicated that the percentage of phosphate adsorption on Na-Mt and Fe-Mt and Fe-Al-Mt decreased,and that on Mg-Al LDH increased with solution pH increase.The adsorptin effects of phosphate adsorption on Mg-Al LDH、Fe-Mt and Fe-Al-Mt were about 95%,higher 40% and 80% than that of Mg-Al-Mt and Na-Mt,respectively.The order of maximum adsorption capacity（Qm） from Langmuir equation was Fe-Al-MtFe-MtMg-Al LDHMg-Al-MtNa-Mt,and b vaules,the important parameters of the adsorption ability,was Mg-Al LDHFe-MtFe-Al-MtMg-Al-MtNa-Mt,and Maximum buffering capacity（Qmb） was the most largest on Mg-Al-LDH and the most smallest on Na-Mt.KF vaules of relatively adsorption capacity form Freundlich equation was the order of Mg-AlFe-Mt Fe-Al-MtMg-Al-MtNa-Mt.And this was in accordance with the results of maximum buffer capacity（Qmb）.The isothermal adsorption of Fe-Mt and Fe-Al-Mt were well described by Langmuir equation,and that of Na-Mt,Mg-Al-LDH and Mg-Al-Mt were in accordance with Freundlich equation by the determination coefficients（R2）.Phosphate adsorption could be divided into rapid and slow reactions.The pseudo second order kinetics provided the best correlation of the experimental data of various modified Mt and Mg-Al-LDH,and the determination coefficients（R2） were 0.999.There also was correlation coefficient R2（0.89～0.94） on various minerals fitted by Elovich equation.Parabolic diffusion equation was most suitable to descrirbe the phosphate adsorption on Na-Mt,and because phosphate adsorption was a diffusion process by inlaid in mineral layers and did＇t involve chemical adsorption processes.
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2011年第10期2061-2067,共7页
Journal of Agro-Environment Science
基金
"十一五"国家科技支撑计划项目(2008BAJ08B13)
