Nowadays, there is a growing concern about the environmental impacts of colored wastewater. Thus, the present work aims the synthesis, characterization and determination of photocatalytic activity of iron oxide (Fe₂O₃) nanocatalyst, evaluating the effect of hybridization with titanium (TiNPs-Fe₂O₃) and silver (AgNPs-Fe₂O₃) nanoparticles, on the degradation of Rhodamine B dye (RhB). Nanocatalysts were characterized by XRD, SEM, TEM, FTIR, N₂ porosimetry (BET/BJH method), zeta potential and DRS. Photocatalytic tests were performed in a slurry reactor, with the nanocatalyst in suspension, using RhB as a target molecule, under ultraviolet (UV) and visible radiation. Therefore, the photocatalytic activity of the nanocatalysts (non-doped and hybridized) was evaluated in these ideal conditions, where the AgNPs-Fe₂O₃ sample showed the best photocatalytic activity with a degradation of 94.1% (k = 0.0222 min⁻¹, under UV) and 58.36% (k = 0.007 min⁻¹, under visible), while under the same conditions, the TiO₂-P25 commercial catalyst showed a degradation of 61.5% (k = 0.0078 min⁻¹) and 44.5% (k = 0.0044 min⁻¹), respectively. According with the ideal conditions determined, reusability of the AgNPs-Fe₂O₃ nanocatalyst was measured, showing a short reduction (about 8%) of its photocatalytic activity after 5 cycles. Thus, the Fe₂O₃ nanocatalyst can be considered a promising catalyst in the heterogeneous photocatalysis for application in the degradation of organic dyes in aqueous solution.

The extensive use of pesticides in agriculture has significantly impacted the environment and human health, as these pollutants are inadequately disposed of into water bodies. In addition, pesticides can cause adverse effects on humans and aquatic animals due to their incomplete removal from the aqueous medium by conventional wastewater treatments. Therefore, processes such as heterogeneous photocatalysis and adsorption by nanocomposites have received special attention in the scientific community due to their unique properties and ability to degrade and remove several organic pollutants, including pesticides. This report reviews the use of nanocomposites in pesticide adsorption and photocatalytic degradation from aqueous solutions. A bibliographic search was performed using the ScienceDirect, American Chemical Society (ACS), and Royal Society of Chemistry (RSC) indexes, using Boolean logic and the following descriptors: “pesticide degradation” AND “photocatalysis” AND “nanocomposites”; “nanocomposites” AND “pesticides” AND “adsorption”. The search was limited to research article documents in the last ten years (from January 2012 to June 2022). The results made it possible to verify that the most dangerous pesticides are not the most commonly degraded/removed from wastewater. At the same time, the potential of the supported nanocatalysts and nanoadsorbents in the decontamination of wastewater-containing pesticides is confirmed once they present reduced bandgap energy, which occurs over a wide range of wavelengths. Moreover, due to the great affinity of the supported nanocatalysts with pesticides, better charge separation, high removal, and degradation values are reported for these organic compounds. Thus, the class of the nanocomposites investigated in this work, magnetic or not, can be characterized as suitable nanomaterials with potential and unique properties useful in heterogeneous photocatalysts and the adsorption of pesticides.