Cobalt ferrite nanoparticles (NPs) have received increasing attention due to their widespread therapeutic and agricultural applicability. In the environmental field, dry powder- and ferrofluid-suspended cobalt ferrite NPs were found to be useful for removing heavy metals and metalloids from water, while diluted suspensions of cobalt ferrite NP have been promisingly applied in medicine. However, the potential toxicological implications of widespread exposure are still unknown. Since cobalt ferrite NPs are considered residual wastes of environmental or medical applications, plants may serve as a point-of-entry for engineered nanomaterials as a result of consumption of these plants. Thus, the aim of this study was to assess the effects of dry powder and fresh cobalt ferrite NP on wheat plants. Seven-day assays were conducted, using quartz sand as the plant growth substrate. The toxicity end points measured were seed germination, root and shoot lengths, total cobalt (Co) and iron (Fe) accumulation, photosynthetic pigment production, protein (PRT) production, and activities of catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX). Increasing total Co and Fe in plant tissues indicated that wheat plants were exposed to cobalt ferrite NP. Seed germination and shoot length were not sufficiently sensitive toxicity end points. The effective concentration (EC₅₀) that diminished root length of plants by 50% was 1963 mg/kg for fresh ferrite NPs and 5023 mg/kg for powder ferrite NP. Hence, fresh ferrite NPs were more toxic than powder NP. Plant stress was indicated by a significant decrease in photosynthetic pigments. CAT, APX, and GPX antioxidant enzymatic activity suggested the generation of reactive oxygen species and oxidative damage induced by cobalt ferrite NP. More studies are thus necessary to determine whether the benefits of using these NPs outweigh the risks.

In the present work, we compared single and mixed adsorption of Cd(II) and Cr(VI) onto co-precipitation synthesized citrate-coated magnetite nanoparticles (NPs). Single kinetic studies revealed Cr(VI) to be better adsorbed than Cd(II). Otherwise, Cd(II) adsorption ratio was improved with Cr(VI) in the binary mixture. Single and mixed adsorption data followed in good agreement the pseudo-second-order kinetic model, with higher initial adsorption rate and rate constant values for Cr(VI). Equilibrium data from single Cd(II) and Cr(VI) adsorption only fitted concordantly the Freundlich isotherm model. The sorption capacity of magnetite NPs as function of initial metal concentrations was found to be 3 mg/g for Cd(II) and 4.65 mg/g for Cr(VI).