Polyhydroxyl-aluminum pillaring improved adsorption capacities of Pb²⁺ and Cd²⁺ onto diatomite

ZHU Jian(朱健), WANG Ping(王平), LEI Ming-jing(雷明婧), ZHANG Wei-li(张伟丽)

(Institute of Environmental Science and Engineering Research,
Central South University of Forestry & Technology, Changsha 410004, China)

Abstract:In order to greatly improve adsorption capacity, the diatomite was pillared by polyhydroxyl-aluminum. A series of adsorption tests were conducted to obtain the optimum condition for pillared diatomite synthesis. The scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), surface area and porosity analyzer and micro-electrophoresis were used to determine pore structure and surface property. The pillared diatomite attaining the optimal adsorption densities (q_e) of Pb²⁺ and Cd²⁺ was synthesized with the following conditions: Addition of pillaring solution containing Al³⁺-oligomers with a concentration range of 0.1–0.2 mol/L to a suspension containing Na⁺-diatomite to obtain the required Al/diatomite ratio of 10 mmol/g; synthesis temperature of 80 °C for 120 min; aging at a temperature of 105 °C for 16 h. The adsorption capacities of Pb²⁺ and Cd²⁺ on pillared diatomite increase by 23.79% and 27.36% compared with natural diatomite, respectively. The surface property of pillared diatomite is more favorable for ion adsorption than natural diatomite. The result suggests that diatomite can be modified by pillaring with polyhydroxyl-aluminum to improve its adsorption properties greatly.

Key words:diatomite; pillaring; polyhydroxyl-aluminum; synthesis; adsorption; Pb²⁺; Cd²⁺