Adsorption properties of phosphorus in water by modified activated carbon coated with LDHs
Two layered doubled hydroxides(MgAl-LDHs and MgFe-LDHs)were synthesized by hydrother-mal 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 phos-phate 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 adsor-bents.The thermodynamic parameters ΔG0<0,ΔH0<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.
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