ZIF-8 supported on cocoa-shell biochar for loratadine adsorption from aqueous solution

Loratadine is an emerging antihistamine contaminant, but its removal using biomass-supported metal-organic framework adsorbents remains scarcely explored. In this work, zeolitic imidazolate framework-8 supported on cocoa-pod-husk-derived biochar (ZIF-8@BC) was synthesized through in situ ZIF-8 growth on alkaline-modified biochar. The material was characterized by XRD, FTIR, TGA, SEM/EDX, elemental analysis, N 2 adsorption-desorption, pH, and pH PZC measurements. The results confirmed the formation of crystalline ZIF-8 domains on the carbonaceous matrix, with increased nitrogen and zinc contents, alkaline surface behavior, and improved textural properties. Loratadine adsorption was evaluated in synthetic aqueous solution under different pH, dose, concentration, contact time, and temperature conditions, with HPLC quantification. The best performance was obtained at pH 6 using 75 mg of adsorbent. Kinetic data were better described by the pseudo-first-order model, while equilibrium behavior followed the Sips model, indicating heterogeneous adsorption with finite saturation. Thermodynamic parameters showed spontaneous and weakly endothermic uptake. The proposed mechanism involves pore filling, hydrophobic interactions, π-π stacking, hydrogen bonding, and possible Lewis acid-base interactions. ZIF-8@BC also retained 82.9% of its adsorption capacity after five reuse cycles without formal regeneration.