Potassium-doped kaolinitic clay from Agboville (Côte d’Ivoire): structural characterization, adsorption behavior, and thermodynamic insights

Camile M. Nongbé et al.

Abstract


This study investigates the adsorption of potassium ions onto thermally activated kaolinitic clay from Agboville (Côte d’Ivoire), with emphasis on the influence of particle size and precursor type (K2CO3 vs. CH3CO2K). The 100–250 µm fraction exhibited the highest performance, with maximum adsorption capacities of 149.84 mg g-1 (K2CO3) and 198.91 mg g-1 (CH3CO2K), the latter providing the most efficient uptake. Potassium acetate produced the most homogeneous and effective incorporation of K+, and was therefore selected as the reference system for further interpretation. The Temkin isotherm model gave the best fit (R2 = 0.9894), while adsorption kinetics followed the pseudo-second-order model (R2 = 0.998), indicating a chemisorption-controlled mechanism. Thermodynamic parameters (ΔG° = -6.16 to -8.55 kJ mol-1; (ΔH°  = +17.8 kJ mol-1; (ΔS°  = +80.3 J mol-1 K-1) confirmed a spontaneous and endothermic process. Characterization analyses revealed surface and bonding modifications induced by potassium doping: attenuation of ν(OH) bands (3695–3620 cm-1) and a shift of the ν(Si-O) vibration to ∼ 1010 cm-1 (FT-IR), an increase in pHPZC from 4.6 to 6.2, homogeneous K+ distribution (1.0–3.0 at. %, EDS), and thermal stability above 700 °C (TGA/DTG). Overall, potassium-doped Agboville clay, particularly when prepared with CH3CO2K, appears as a low-cost, thermally robust and highly basic local adsorbent suitable for aqueous pollutant removal and catalytic support applications.


Keywords


Kaolinitic clay ; Potassium doping ; Adsorption kinetics ; Physicochemical characterization.

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References


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