Development of highly porous mullite whisker ceramic membranes for oil-in-water separation and resource utilization of coal gangue

To realize the recycling of coal gangue and obtain high value-added products, highly porous mullite whisker ceramic microfiltration membranes for the treatment of emulsified oily wastewater were prepared using Al(OH)3 and coal gangue as primary materials and MoO3 as the additive. By a comparative study on the ceramic membranes with and without MoO3 addition, the sintering reaction process, thermal shrinkage behavior, microstructure, open porosity, flexural strength, pore size distribution, and pure water permeate flux of the ceramic membranes were illuminated. The MoO3 addition enhances mullitization reaction and promotes mullite whisker growth. Through changing the sintering temperature so as to control mullitization reaction and mullite whisker growth, the satisfactory porosity and pore size are achieved for the mullite whisker ceramic membrane sintered at 1400 °C. The mullite whisker ceramic microfiltration membrane, possessed a high open porosity of 47.21 ± 0.48%, the average pore size of 185.3 nm and flexural strength of 34 ± 2.5 MPa, shows the highest permeability of 35.8 mL·m−2·s−1 and above 97% oil rejection when operating at 0.1 MPa trans-membrane pressure in oil-in-water separation experiments.