Modification of MgAl hydrotalcite by ammonium sulfate for enhancement of lead adsorption

The modification of hydrotalcite (LDH) by (NH4)2SO4 was investigated in order to apply the modified LDH (MLDH) as an adsorbent in the removal of Pb(II). During the SO42– modification, the exchange process between SO42– and CO32– in interlayer spaces took place along with Mg2+ partial dissolution from edges of the brucite sheets, which provided active sites for Pb(II) bonding to the adsorbent particles. The modification could reduce the permanent positive charge density from 2.31 and 1.20 C/m2 and increased the surface area from 98.7 to 104.5 m2/g, which enhanced the Pb(II) sorption performance of the adsorbent due to more lead salts precipitates by binding Pb(II) with SO42− in the interlayer space, or probably including with SO42– attached on the surface of the particles. It could be concluded that the sorption process was chemisorption and diffusion mixed type sorption process, but chemisorption was dominant compared with diffusion.