Evaluación del proceso de sorción de metamidofos en medio acuoso con una zeolita natural modificada con Hexadeciltrimetilamonio (HDTMA) y determinación de los parámetros termodinámicos

Abstract

Worldwide, the pesticides use has contributed significantly to the improvement and increase of food production. However, its indiscriminate and uncontrolled use has caused the emergence of resistant pests, soil pollution, air and mainly water, as well as the intoxication and death of various living organisms. Methamidophos is a systemic organophosphate pesticide with insecticidal and acaricide, banned in many countries for being considered a high toxicity pesticide due to adverse effects on the environment and human health. However, in Mexico, it is the second most widely used pesticide. It should be noted that most publications related to its quantitative determination uses High-Performance Liquid Chromatography (HPLC) or Gas Chromatography (CG) coupled to Mass Spectrometry (MS), these methods are extremely expensive and few laboratories in Mexico count on them. In addition, the conventional methods of elimination for this type of pollutants have not been proven effective, so, over the last decade, researchers have focused on methamidophos elimination by diverse methods, among which adsorption is not reported yet. This is an efficient, low-cost and accessible method for various pollutants; and in recent years, many new adsorbing materials have been investigated, including modified zeolitic materials with various surfactants. Evaluating the thermodynamic parameters involved, such as enthalpy (ΔH°), entropy (ΔS°) and free Gibb energy (ΔG°) are useful for determining the nature and type of mechanism that predominates in an adsorption process. Due to the aforementioned problems, it is important to propose new methods for the treatment of water containing this type of pollutants so this research report for the first time, on this pesticide adsorption behavior in potential adsorbent materials that allow their efficient disposal such as zeolitic materials modified with a cationic surfactant, as is HDTMA, thus opening a very wide research panorama in this area. This research carried out a systematic study on methamidophos adsorption behavior on the studied zeolitic materials, depending on diverse physicochemical parameters such as the contact time effect, and methamidophos concentration; likewise, the HDTMA-modified zeolitic material with greater adsorption capacity was selected, and only in this material was evaluated the adsorbent amount, pH effect and temperature effect of the solid/liquid systems to study and were determined thermodynamic parameters.