Cu(II) Removal from Aqueous Samples Using In Situ Functionalized Silica with Novel Synthesized Formazan: Synthesis, Characterization, Kinetic and Isothermal Studies

A novel silica-based sorbent, silica-carbazole-formazan (Si-Carb-Formazan), was synthesized through in situ functionalization with a newly prepared carbazole formazan derivative to remove Cu-(II) ions from aqueous solutions efficiently. The sorbent was characterized using techniques such as FTIR, SEM, TGA, and XPS, which revealed a porous structure with a high surface area and excellent thermal stability. Batch adsorption experiments analyzed the influence of various factors on the sorbent's performance, demonstrating its high efficiency. Optimal adsorption occurred at a pH of 6.0, with a maximum capacity of 34 mg/g achieved within 15 min using only 5.0 mg of the sorbent. The adsorption process adhered to the Langmuir isotherm model and followed pseudo-second-order kinetics. Also, thermodynamic analysis indicated that the process was exothermic under the studied conditions. The sorbent displayed high selectivity for Cu-(II) ions over other metal ions and retained over 90% of its initial capacity after five regeneration cycles using 0.10 M HCl. These findings highlight the high efficiency and potential of Si-Carb-Formazan as a reusable and cost-effective material for the rapid removal of toxic Cu-(II) ions from contaminated water.