A reusable Fe3O4/GO-COOH nanoadsorbent for Ca2+ and Cu2+ removal from oilfield wastewater

Oilfield wastewater contains a large number of metal ions (such as Ca 2+ and Cu 2+ ). Reinjection in oil wells without treatment would affect oil recovery. To remove Ca 2+ and Cu 2+ ions, we prepared a reusable Fe 3 O 4 /GO-COOH nanoadsorbent by the magnetization and carboxylation of graphene oxide (GO). The Ca 2+ and Cu 2+ removal percents of the nanoadsorbent reached 78.4% and 51% at 60 min, respectively. After five adsorption/desorption cycles, the nanoadsorbent retained high recovery rates (82.1% for Ca 2+ and 91.8% for Cu 2+ ) and removal percents (72.3% for Ca 2+ and 49.33% for Cu 2+ ). In the simulated indoor oil recovery test, oilfield wastewater treated with Fe 3 O 4 /GO-COOH could enhance oil recovery (EOR) by 11.0% compared with untreated oilfield wastewater. The novel magnetic nanoadsorbent could not only adsorb metal ions in oilfield wastewater effectively to enhance oil recovery (EOR) but could also be quickly recycled and reused, which shows promising application prospects in oil exploitation.