Fabrication of g-C3N4/alginate biocomposites with fenugreek seed gum for efficient column and batch adsorption of mercuric ions.

Mercuric ions (Hg2+) are among the most dangerous heavy metal cations to human health because they resist corrosion, dissolve easily, and have the potential to cause cancer and other diseases. In environmental adsorption applications, the development of eco-friendly, efficient, and reusable solid adsorbents is considered the main challenge. In the current study, three solid adsorbents were prepared and characterized for the efficient removal of Hg2+, namely, graphitic carbon nitride/alginate (CAlg), fenugreek seed gum/alginate (FAlg), and graphitic carbon nitride/fenugreek seed gum/alginate (FCAlg) composites. The fabricated FCAlg showed important characteristics, such as a surface area (S BET) of 161.4 m2 g-1, a pore diameter of 2.032 nm, a point of zero charge (pHPZC) of 6.7, and a surface rich in different chemical functional groups. Both batch and fixed-bed column adsorption techniques were employed to remove Hg2+ ions to achieve a complete picture of the fabricated adsorbent's efficiency. FCAlg effectively adsorbed Hg2+ ions in batch studies, achieving the highest adsorption capacity (460.7 mg g-1) under specific conditions such as pH 4, 1.0 g L-1 adsorbent dose, 50 min of shaking time, and 15 °C. Several nonlinear isotherm and kinetic models were used to accurately characterize Hg2+ adsorption. FCAlg exhibited a column adsorption capacity of 68.3 mg g-1 under optimal conditions including a bed height of 1.5 cm, an initial Hg2+ concentration of 80 mg L-1, a solution flow rate of 10 mL min-1, pH 4, and 15 °C. Overall, the batch and column studies highlight the strong potential of FCAlg for practical applications as an adsorbent for Hg2+ removal due to the surface chemical functional groups introduced by the applied biopolymers and enhanced textural characteristics.