Nanoparticle-Sorbed Phosphate: Iron and Phosphate Bioavailability Studies with Spinacia oleracea and Selenastrum capricornutum

In this study, nanoscale zero-valent iron (NZVI) particles have been used for phosphate recovery from aqueous solutions. The bioavailability of the phosphate sorbed onto NZVI particles was determined using spinach (Spinacia oleracea) and algae (Selenastrum capricornutum) grown in hydroponic solutions. Simultaneous bioavailability of iron (from NZVI) was also determined. Spent NZVI particles (after phosphate adsorption) were added to the algae and spinach growth media as the only source of phosphate and iron. Phosphate sorbed by NZVI was bioavailable to both algae and spinach. The concentration of algae increased by 6.7 times when the only source of phosphate was spent NZVI as compared to algae grown in standard all nutrient media (including phosphate). Again, removing phosphate from the growth media decreased the algae concentration similar to 3 fold when compared to algae grown in all-nutrient media. In the spinach study, plant biomass increased in the presence of spent NZVI (where nanoparticles were the only source of phosphate) by 2.2-4 times more than the plant treated with the all-nutrient solution. Results also indicated 21, 11, and 7 times more iron content in the roots, leaves, and stems of the spinach treated with spent NZVI respectively, as compared to the controls.