Synthesis of Ca-based Layered Double Hydroxide from Blast Furnace Slag and Its Catalytic Applications

Abstract

A Ca-based layered double hydroxide (LDH) was synthesized from blast furnace slag (BFS) via a facile and low-cost manufacture process. The synthesis was performed through a two-step method including (i) an acid-dissolution and (ii) an alkali-precipitation process using BFS as a sole metal source. The formation of Ca–Al LDH crystals occurred above pH 9, and under the optimal synthetic conditions (at 373 K and pH 11.5) a well-crystallized stoichiometric hydrocalumite (Ca:Al:Cl=2:1:1) incorporating the slag-derived metallic elements in its structure was obtained with a metal recovery rate of 85%. The impacts of synthesis pH and temperature on the material structures were investigated in detail. The catalytic properties of the thus synthesized LDH material was demonstrated on industrially important several chemical reactions including (1) oxidation of alkyl aromatics with O₂, (2) CO₂ fixation reaction and (3) biodiesel synthesis from vegetable oil. These results open up a new route to fabricate a low-cost LDH compound and its potential availability as an alternative solid base catalyst.