Phallusia nigra-mediated vanadium removal from brine: Assessment and optimization

The rejected brines from desalination plants contain significant amounts of heavy metals. In this study, we evaluated the effectiveness of Phallusia nigra Savigny, 1816 (P. nigra) in removing vanadium from the rejected brines of desalination plants through the bioaccumulation process. Initial assessments revealed a remarkably high accumulation rate of vanadium in P. nigra with a bioaccumulation factor exceeding 4.7 × 10⁴ in the tunic and 5.1 × 10⁵ in the mantle body. Acclimation experiments demonstrated that P. nigra could survive salinities up to 56 practical salinity units (psu), temperatures of ≤32 °C, and pH of 6.5-8.5. We employed the L-16 Taguchi approach in experimental design to optimize environmental conditions for vanadium removal by P.nigra. Our results indicated that temperature has the most significant effect on increasing vanadium bioaccumulation in P. nigra, followed by salinity and pH. Under optimal conditions, the vanadium concentration reached 1892.30 ppm in the entire body of P. nigra compared to 350 ppm in natural conditions. Considering that, a high concentration of vanadium is toxic to the environment and the conventional methods of its removal from brine are costly and include the use of chemicals that pollute the environment, therefore, vanadium removal from brine using P. nigra can be considered a cost-effective and environmentally friendly method in the future, as opposed to some chemical methods.