## 3 Results and Discussion
### Environmental Indicators of the Single-Core Magnetic Nanoparticle  
The development of new processes must comply with sustainability criteria. The methodology applied for the holistic assessment of the most suitable support was based on a life cycle perspective [48], which would include all aspects of activities during the life of a product, such as the extraction of raw materials and resources, production processes, use of products, recovery, recycling of some fractions, and the final disposal at the end-of-life stage.  
In this study, inventory data for the foreground systems (direct inputs and outputs for each scenario) such as electricity requirements (estimated with power and operational data from the different units: reactors, dryers, heaters) as well as the use of chemicals and water were average data from semi-pilot scale experiments, obtained by on-site measurements of production processes developed for a time period of three months. The environmental assessment was conducted using characterization factors from ReCiPe Midpoint methodology [34], and the impact categories for the different mNP production routes are displayed considering one gram of FeO-2206W mNPs as a functional unit (Table 4).  
The normalization results show that the impacts associated with the consumption of energy are dominant, but chemicals used in the formulations and for re-dispersion are also relevant. Regarding electricity, it is consumed for stirring, and the mechanical agitation required to obtain the transparent red solution of reverse micro-emulsion until complete reaction is remarkable (97% of the total electrical requirements). Regarding chemicals, the cyclohexane required in the formulation is the environmental critical chemical, since it is responsible for more than 85% of burdens derived from chemicals contributions regardless the impact category. Aiming to reduce the impacts, we also considered  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Scenarios** & \\ \hline
**Impact Category** & **Silica-Coated mNPs** & **Silica Thin Shell** \\ \hline Climate change & \(1.43\times 10^{-4}\) & \(1.03\times 10^{-4}\) \\ Ozone depletion & \(3.69\times 10^{-6}\) & \(2.42\times 10^{-6}\) \\ Terrestrial acidification & \(1.83\times 10^{-4}\) & \(1.30\times 10^{-4}\) \\ Freshwater eutrophication & \(9.11\times 10^{-4}\) & \(5.42\times 10^{-4}\) \\ Marine eutrophication & \(2.12\times 10^{-5}\) & \(1.45\times 10^{-5}\) \\ Human toxicity & \(5.93\times 10^{-4}\) & \(3.98\times 10^{-4}\) \\ Photochemical oxidant formation & \(1.33\times 10^{-4}\) & \(9.05\times 10^{-5}\) \\ Terrestrial ecotoxicity & \(6.18\times 10^{-6}\) & \(4.37\times 10^{-6}\) \\ Freshwater ecotoxicity & \(1.22\times 10^{-3}\) & \(8.36\times 10^{-4}\) \\ Marine ecotoxicity & \(1.45\times 10^{-3}\) & \(9.84\times 10^{-4}\) \\ Fossil depletion & \(6.20\times 10^{-4}\) & \(5.18\times 10^{-4}\) \\ Normalized index & \(5.28\times 10^{-3}\) & \(3.62\times 10^{-3}\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Normalized environmental impacts associated with the production of silica-coated mNPs (FeO-2206W) and silica thin shell per g of mNP.  
Figure 2: Phenol transformation in subsequent cycles of enzymatic treatment with laccase immobilized onto FeO-2206W (pH 6).  
the use of a lower dose of cyclohexane to obtain a thin silica coating on the nanoparticle. Although the environmental impact was reduced, the immobilization of the enzyme was negatively affected by 40%, which was detrimental to the overall efficiency of the process. However, it should be highlighted that the production systems have been assessed at the pilot scale and optimizations should be required for large-scale application.