A novel hydroxyapatite super-hydrophilic membrane for efficient separation of oil-water emulsions, desalting and removal of metal ions

Super-hydrophilic separation membrane has been widely used to treat oily wastewater in production and life. However, the membrane is easily contaminated by oily emulsion and metal ions, which affects the separation flux and efficiency. This study presented a novel approach to prepare super-hydrophilic membranes by intercalating hydroxyapatite with graphene oxide and utilizing vacuum filtration. The membranes were thoroughly characterized using various techniques including FT-IR, XRD, SEM, AFM, and contact angle measurements. The study revealed that the hydroxyapatite's layered petal-like structure, combined with the hydrophilicity and graphene oxide, results in a membrane that is super-hydrophilic and underwater super-hydrophobic. HG-4 membrane had an excellent ability to separate oil-water emulsions (the separation flux reached 1798 L/(m2·h)). In addition, it can maintain good shape after 168 h of exposure to acid, alkali and salt. More importantly, HG-4 can effectively remove metal ions (Fe3+ adsorption effect of 98.34 %) and salt solution (CaCl2 desalination rate of 76.21 %). The proposed hydroxyapatite membrane presents a novel approach for separating oil and water, and holds promising potential for application in this field.