Pesticides are chemical compounds applied in agriculture to repel or kill undesirable organisms, and are therefore the most effective way to optimize the quantity and quality of crops to ensure food safety for the population [1, 2]. According to data from the Food and Agriculture Organization of the United Nations (FAO), there has been continuous increase in the use and commercialization of pesticides over the past 30 years. In 2020, about 2.7 million tons of pesticides were used in agriculture worldwide, with the majority in the United States of America, followed by Brazil, China, Argentina, and the Russian Federation [3].
The effective use of pesticides to control pests, such as thiacloprid, is widespread throughout the world, especially from the point of view that many of these neonicotinoid can be used to control the most different types of pests [4, 5]. However, due to its high-water solubility (185 mg L− 1 at 20 ºC) and low molecular weight (253 g mol− 1), thiacloprid is highly mobile in aquatic environments and poses a significant threat to aquatic ecosystems and human health [6, 7].
Recent studies indicate that ingestion of this insecticide can cause mutagenic and carcinogenic effects, acute toxicity, skeletal retardation, and changes in motor ability [8, 9]. Therefore, it is necessary that thiacloprid be removed from the aquatic environment, so that it does not affect the organisms present in the environment, nor those that come into contact with it.
Various treatment approaches, such as adsorption [10], advanced oxidative processes [11], membrane filtration/separation [12], and biological treatment [13] can be found in the literature aimed at the remediation of pesticides from the aqueous medium. However, most remediation technologies have high cost, low efficacy, and the possibility of degradation products that may be equally or more toxic than the pesticide to be removed [14].
Adsorption technology is a promising technique for removing pesticides from water because of its high efficiency and practicality, versatile method, eco-friendly, easy to use, so on [14, 15]. The process consists of dispersing a solid material in the aqueous solution containing the pesticide, and after a certain period of time, separating the phases. It is extremely important to point out that the physical and chemical features of the adsorbent material can decisively influence the efficiency of remediation of a given pollutant, considering that the adsorption technology is governed mainly by a surface process [16]. Therefore, there is a search for increasingly specific and effective adsorbents for environmental remediation of pesticides, such as thiacloprid.
Silicon-based nanoarchitectured materials, such as MCM-41-based nanomaterials, have infinite advantages when compared to a bulk material, mainly presenting characteristics such as wide and controllable internal surface, well-defined mesopores, large high surface area, and high stability of mesoporous framework [17–19]. The MCM-41-based nanostructures concentrates most studies in the M41S family, due to its two-dimensional hexagonal arrangement with P6mm space group symmetry and well-defined hexagonal network arrangement, it has been widely used with inorganic support [18, 19].
The anchoring of chiral molecules in the self-assembled nanoarchitectures, such as the M41S family, can be carried out in a promising way due to the multifunctional characteristics of these nanomaterials [20]. The synthesis of small organic molecules that have chiral centers with the ability to separate a extensive variety of chiral compounds was developed by Pirkle and collaborators [21–23]. Such molecules synthesized by Pirkle have aromatic units that interact with a combination of different intermolecular forces.
The intermolecular forces act in an important way in the maintenance of the stereochemical control, promoting an improvement in the efficiency of adsorption and separation of chiral compounds. These chiral molecules can be physically grafted within a nanoporous support, such as MCM-41-based nanoarchitecture [24–26].
The adsorption procedures are promising; but several variables that affect the adsorption phenomenon as: pH, adsorption time, analyte concentration, and mass of the adsorbent should be studied. In this sense, multivariate optimization is an interesting option in adsorption processes optimization. These tools have numerous advantages, such as: (i) possibility of evaluating synergistic and antagonistic interactions between variables; (ii) possibility of forecasting the system under study in a condition that has not been tested in practice; and (iii) reduces the generation of chemical waste which contributes to the principles of green chemistry. Among the multivariate optimization tools factorial design is more employed and allows a preliminary evaluation of the variables for development. Factorial designs have been used in several areas, but its use in absorption procedures has not been explored sufficiently [27–29].
In previous studies it has been observed that interactions can be formed between MCM-41-based mesoporous arrays with pesticides [30]. Therefore, the application of a new functionalized mesoporous material may be a promising alternative for environmental remediation of thiacloprid. The aim of the present approach was to optimize the ability of the MCM-41-Pirkle adsorbent to act as a remediator for the pesticide thiacloprid. For this, a factorial design was employed in order to optimize the main parameters involved in the adsorption process.