Water contamination by organic pesticides represents a major global environmental challenge. Insecticides such as carbaryl and imidacloprid in aquatic environments can harm pollinators, thereby impacting ecosystems, food security, human health, and the economy. This situation highlights the need to develop safe, effective, sustainable remediation strategies.
In this context, this thesis focuses on the development of layered double hydroxide (LDH) based materials modified with naturally derived surfactants. The main objective was to design efficient and environmentally friendly adsorbents by establishing a link between their structural and physicochemical properties and their adsorption performance for carbaryl and imidacloprid. Although the use of natural surfactants for LDH modification has been explored to some extent, it remains limited, particularly for pesticide remediation applications.
In this research, food-grade natural surfactants, sodium palmitate (PS), sodium stearate (SS), and rhamnolipids (RL), were employed to improve the adsorption of pesticides onto CaAl- and MgAl-based LDHs. This composition was selected to minimize secondary toxicity and environmental risks associated with adsorbent materials.
The synthesized materials were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). Subsequently, adsorption studies were conducted under various experimental conditions, and the analysis of kinetic models (pseudo-first-order and pseudo-second-order) and isotherm models (Langmuir, Freundlich, Sips, and Temkin) enabled the elucidation of the adsorption mechanisms involved.
The results demonstrated that the incorporation of natural surfactants induced key structural modifications, including expansion of the interlayer spacing, the appearance of characteristic FTIR bands, increased surface hydrophobicity, and enhanced adsorption through mechanisms combining hydrophobic, surface, and anion-exchange interactions.
Among the tested materials, CaAl-PS-LDH exhibited the best performance, achieving an adsorption capacity of 16 mg g-1 for carbaryl and 4.53 mg g-1 for imidacloprid compared with 1.83 mg g-1 for carbaryl and 0.78 mg g-1 for imidacloprid with the inorganic LDH. Furthermore, characterization analyses enabled the proposal of a structural model describing the probable orientation of surfactant anions within the interlayer space.
Overall, the natural surfactant-modified LDHs developed in this thesis demonstrated competitive performance compared with LDHs intercalated with synthetic surfactants and significantly outperformed their inorganic counterparts. Moreover, adsorption efficiency was strongly influenced by pesticide molecular characteristics, pH, temperature, initial pesticide concentration, and adsorbent dosage, with optimal performance observed under slightly alkaline conditions. Reusability tests also confirmed the potential for multiple adsorption desorption cycles, although a gradual decrease in efficiency was observed.
The findings highlight the effectiveness of natural surfactant-modified LDHs for designing materials tailored to the adsorption of specific compounds. These adsorbents show strong potential for several applications, including contaminated water treatment, drinking water production, and decentralized treatment in rural, remote, or resource-limited communities.
| Date | 16 Feb 2026 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Robert Hausler (Supervisor) |
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