Surface Functionalization of Waste Brick Powder With Amine Groups for High‐Performance Adsorptive Removal of Cationic Dyes From Aqueous Solutions

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In this study, waste brick powder (WBP) was functionalized with aminopropyl trimethoxysilane (APTMS) to introduce amino functional groups, yielding NH 2 ‐WBP, to enhance crystal violet (CV) adsorption. The synthesized adsorbent was comprehensively characterized using various techniques. Batch adsorption experiments evaluated the effects of contact time (30–120 min), solution pH (2–12), adsorbent dose (0.01–0.4 g), initial dye concentration (5–25 mg L − 1 ), and temperature (15°C–50°C) on CV removal. Functionalized waste brick powder (NH 2 ‐WBP) achieved an exceptional removal efficiency of 99.96% under optimal conditions, including a pH of 7, an adsorbent dosage of 0.25 g, a CV concentration of 10 mg/L, and a contact time of 60 min. Adsorption kinetics were analyzed using the pseudo‐first‐order, pseudo‐second‐order, Elovich, and intraparticle diffusion models. The pseudo‐second‐order model best fit the experimental data (R 2 = 0.9965), indicating that the adsorption rate was predominantly governed by surface interactions, with a maximum uptake of CV by NH 2 ‐WBP of 2.96 mg g − 1 . Equilibrium data were evaluated using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models. The Dubinin–Radushkevich model showed the highest correlation (R 2 = 0.9947) and the highest energy required for adsorption (1.0584 mg g − 1 ). Thermodynamic parameters indicate that the adsorption removal process is spontaneous and endothermic.