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.

The adsorption of a metal ion to a polycyclic aromatic molecule such as helicene is the object of our study. The latter could function as a chiral molecular clamp for the cationic alkali metal. The main contribution of this work is to attribute new microscopic interpretations for the adsorption of potassium and cesium ions onto a thin layer of helicene achieved by the QCM technique. Throughout the grand canonical ensemble and some theoretical considerations, statistical physics processing has been used for modeling of experimental adsorption isotherms. A new model has been developed and chosen as an appropriate one to present a good correlation with experimental isotherms. Six physico-chemical parameters are obtained from the fitting of the experimental adsorption isotherms. Thanks to the steric parameters, we have found that an increase in temperature promotes a rise in the numbers of ions per site n₁ and n₂ and raises the adsorption capacities N_M1 and N_M2. The two energetic parameters c₁ and c₂ allow deduction of the adsorption energies at four temperatures. It is found from the calculated energies that physical adsorption takes place; the helicene can function as potassium and cesium captor and the K⁺–helicene complex is more stable than the Cs⁺–helicene complex.