Sorption Removal of Pb（Ⅱ） from Solution by Uncalcined and Calcined MgAl-Layered Double Hydroxides

Layered double hydroxide （LDH） with a Mg/Al molar ratio of 1 ： 1 was synthesized by using a co-precipitation method and its calcined product （CLDH） was obtained by calcination of the MgAl-LDH at 500 ℃. The sorption removal of Pb^2＋ from solution was investigated, finding that both LDH and CLDH show good sorption ability and they could be used as a new type of environmental sorbent for the removal of Pb^2＋ from water. The sorption kinetics and the sorption isotherms of Pb^2＋ on both LDH and CLDH can be described by the pseudo-second order kinetics and Freundlich isotherm, respectively, under the studied conditions. The sorption amounts of Pb^2＋ on LDH and CLDH are independent of pH in a pH range of about 3-10. The presence of NaNO3 may inhibit the sorption of Pb^2＋ on LDH while hardly affect that on CLDH. The sorption mechanism of Pb^2＋ on LDH and CLDH may be attributed to the surface precipitation and the surface complex adsorption. The surface complex adsorption may be further distinguished to the chemical binding adsorption forming the inner-sphere surface complexes and the electrostatic binding adsorption forming the outer-sphere surface complexes. The sorption mechanism of Pb^2＋ on LDH may be attributed to the surface precipitation and the electrostatic binding adsorption, while that on CLDH may be attributed to the surface precipitation and the chemical binding adsorption.

Sorption Removal of Pb(II) from Solution by Uncalcined and Calcined MgAl‐Layered Double Hydroxides

Layered double hydroxide (LDH) with a Mg/Al molar ratio of 1:1 was synthesized by using a co‐precipitation method and its calcined product (CLDH) was obtained by calcination of the MgAl‐LDH at 500 °C. The sorption removal of Pb²⁺ from solution was investigated, finding that both LDH and CLDH show good sorption ability and they could be used as a new type of environmental sorbent for the removal of Pb²⁺ from water. The sorption kinetics and the sorption isotherms of Pb²⁺ on both LDH and CLDH can be described by the pseudo‐second order kinetics and Freundlich isotherm, respectively, under the studied conditions. The sorption amounts of Pb²⁺ on LDH and CLDH are independent of pH in a pH range of about 3–10. The presence of NaNO₃ may inhibit the sorption ofPb²⁺ on LDH while hardly affect that on CLDH. The sorption mechanism of Pb²⁺ on LDH and CLDH may be attributed to the surface precipitation and the surface complex adsorption. The surface complex adsorption may be further distinguished to the chemical binding adsorption forming the inner‐sphere surface complexes and the electrostatic binding adsorption forming the outer‐sphere surface complexes. The sorption mechanism of Pb²⁺ on LDH may be attributed to the surface precipitation and the electrostatic binding adsorption, while that on CLDH may be attributed to the surface precipitation and the chemical binding adsorption.