Kinetic study of Diclofenac removal on Biocomposite microcapsules in aqueous systems

The study of sodium diclofenac (SDF) adsorption on alginate/inorganic filler(Alg/PZ) microcapsules addresses the environmental issues related to the presence of pharmaceutical contaminants in water. The Alg/PZ biomaterial microcapsules were synthesized by crosslinking under various conditions (polymer: 0.75-1.3 g; inorganic filler: 0.4-1.2 g). The product and raw materials were characterized by thermogravimetric analysis (TGA); Fourier transform infrared spectroscopy (FTIR); and scanning electron microscopy (SEM).

TGA revealed optimal encapsulation or synthesis for the 0.75/1.2 mass ratio (Alg/PZ), with 63.87% PZ encapsulation, indicating enhanced thermal stability. Effective entrapment of PZ within the polymeric matrix was proven by FTIR and TGA analyses, highlighting hydrogen and electrostatic bonds, while SEM images confirmed a spherical, uniform, and porous bead morphology with a diameter of 1.73 mm. Sallow-bed adsorption revealed instantaneous pseudo-second-order kinetics, reaching equilibrium in 45 minutes, with a maximum adsorption capacity (q_max) of 21 mg·g^-1 for an adsorbent mass of 0.2 g. Furthermore, kinetic studies, supported by the Weber–Morris and Crank (squared driving force model) models, highlighted pore accessibility as well as a concentration-dependent effective diffusion coefficient (Dₑff). The squared driving force mass transfer model validated diffusion-limited kinetics (D_ₑff = 2.96×10⁻⁷ cm²·s⁻¹, R² = 0.9832). This study validates Alg/PZ composites as sustainable and scalable solutions compared to conventional adsorbents, enabling 98% SDF removal under optimal conditions.