Lanthanum-doped kaolinite for hierarchical bi-modal porous inorganic membrane

Abstract Porous inorganic membranes can function in corrosive or high-temperature environments for prolonged duration without significant degradation in performance. Their high fabrication and material cost, however, outweigh their advantages. Here, adding lanthanum (La) to kaolinite, a cheaper inorganic material, enables a stronger and more permeable membrane sintered at 1150 °C; A 11 wt% La-doped kaolinite displays strength of ∼10 MPa and Darcy’s permeability of 1.5 × 10 −13  m 2 –2.5 and 3 times higher than the pristine sintered kaolinite matrix respectively. The La-doping technique disrupts the randomly oriented stack of kaolinite flakes and increases the particle-particle contacts during sintering. Consequently, “pot-holes” are created to give a bi-modal porous structure, which reduces the tortuosity and improves the pore connectivity. It is concluded that La interacts with Al of the kaolinite during sintering based on XRD and EDX analysis. Finally, a carbon nanotube network (CNTN) is incorporated into the porous channel of La-doped membrane and is used as a membrane to purify emulsified oily water with a 100% rejection.