LDHs覆膜改性活性炭对水中磷的吸附特性研究

Adsorption properties of phosphorus in water by modified activated carbon coated with LDHs

采用水热共沉淀法合成两种层状双金属氢氧化物(MgAl-LDHs和MgFe-LDHs)覆膜于活性炭,并研究了其对水中磷的吸附特性。结果表明,在pH=7、温度为298.15 K、吸附时间为4 h时,MgAl-LDHs和MgFe-LDHs改性基质对磷酸盐最大理论吸附容量分别为3.158 mg/g和4.557 mg/g。吸附过程更加符合Langmuir等温模型和拟二级动力学吸附模型,以均匀单分子层化学吸附为主。当磷酸盐初始浓度为0.5 mg/L和2 mg/L时,MgAl-LDHs改性基质的饱和吸附容量接近MgFe-LDHs改性基质的2倍,MgAl-LDHs改性基质更适合作为吸附剂。LDHs改性基质吸附磷酸盐的热力学参数ΔG_(0)<0、ΔH_(0)<0,说明吸附过程是自发的放热过程,低温更有利于提高吸附效果。

Two layered doubled hydroxides(MgAl-LDHs and MgFe-LDHs)were synthesized by hydrothermal coprecipitate method and coated on activated carbon,and their adsorption properties for phosphorus in water were investigated.The results showed that the maximum theoretical adsorption capacities of MgAl-LDHs and MgFe-LDHs modified substrates were 3.158 mg/g and 4.557 mg/g,respectively,when pH=7,temperature was 298.15 K and adsorption time was 4 h.The pseudo-second-order kinetic adsorption model and the Langmuir isothermal model both provide better descriptions of the adsorption process,and the homogeneous monolayer chemisorption is the main process.When the initial concentration of phosphate is 0.5 mg/L and 2 mg/L,the saturated adsorption capacity of MgFe-LDHs modified matrix is nearly twice that of MgFe-LDHs modified matrix,and MgAl-LDHs modified matrix is more suitable as adsorbents.The thermodynamic parametersΔG_(0)<0,ΔH_(0)<0 for adsorption of phosphate by LDHs modified matrix indicate that adsorption is a naturally occurring exothermic process,and low temperature is more conducive to improving the adsorption effect.