Nanofiltration (NF) with adsorptive membrane technologies are one of the most promising methods for the efficient treatment of industrial wastewater having toxic heavy metal ions. The present investigation deals with the fabrication of nanocomposite Fe3O4@MXene membranes by self‐assembly of Fe3O4 nanoparticles (NPs) and two‐dimensional (2D) MXene nanosheets on the surface of cellulose acetate (CA) base membrane. The Fe3O4 NPs were found to be uniformly dispersed on the MXene sheet structure and thus expanded the 2D nanochannel of MXene. The water flux and the removal ratio of heavy metal ions by this nanocomposite membrane were found to improve significantly, compared to the virgin MXene membrane. Under the synergistic effect of layer sieving and the adsorption ability, the composite NF membrane was found to achieve a maximum of 63.2% for Cu2+, 64.1% for Cd2+ and 70.2% for Cr6+ removal from wastewater, respectively. Moreover, Fe3O4@MXene membrane also exhibited good recycling ability after washing by HCl solution.

Fluorite, barite and calcite are important industry minerals. However, they often co-exist, presenting difficulty in selectively separating them due to their similar surface properties. In this study, valonea extract and sodium fluosilicate were used as depressants to selectively separate them by flotation, with sodium oleate as the collector. The single mineral flotation results showed that valonea extract displayed the strongest depression on calcite, while sodium fluosilicate displayed the strongest depression on barite. These two depressants allowed selective separation of the three minerals through sequential flotation. The flotation of mixed minerals showed that 94% of the calcite was successfully depressed by the valonea extract, and 95% recovery of the fluorite was achieved in the subsequent flotation with sodium fluosilicate depressing barite. The different depressant-mineral interactions were investigated via electro-kinetic studies and molecular dynamics (MD) simulations using the Materials Studio 6.0 program. The valonea extract exhibited the strongest adsorption on the calcite surface, and sodium fluosilicate exhibited the strongest adsorption on the barite surface, which prevented oleate species from reacting with Ca 2+ or Ba 2+ surface sites. This study provides useful guidance for how to process fluorite, barite and calcite resources.

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