Hierarchical structurized waste brick with opposite wettability for on-demand oil/water separation

Due to the variety of oily wastewater and complexity of separation system, it has put forward new challenge and requirement to separation materials for on-demand separation of various oil/water mixtures. Here, we reported a facile waste-to-resource strategy to rationally fabricate hierarchical ZnO nanopillars coating onto the surface of waste brick grains (ZnO/WBG) via simple physical process and in-situ growth technique. Specifically, the directly as-prepared ZnO/WBG possess superhydrophilic/underwater superoleophobic (UWSOB) properties and modified ZnO/WBG by organosilicon reagent possess quasi superhydrophobic/superoleophilic (SHOBI) properties. It is also worth noting that this discrete ZnO/WBG with opposite wettability can be accumulated into ZnO/WBG layer with numerous tortuous channel structure, making it feasible for on-demand separating various oil/water mixtures whether immiscible light- and heavy-oil/water mixtures or oil-in-water and water-in-oil emulsions. It has been demonstrated that the filter layers with opposite wettability exhibit high separation efficiency and flux, excellent chemical stability and admirable recyclability. Thus, this novel and cost-effective ZnO/WBG layer holds great promise for large-scale and versatile oil/water separation. Additionally, this work presents a sustainable perspective of effectively utilizing waste brick to construct workable functionalized materials with tremendous application potential, showing far-reaching value and significance in fundamental research and environmental protection.