Quartzite Waste–Based Composite: An Environmental and Renewable Material for the Adsorptive Removal of Industrial Dyes

A carbon‐supported quartzite powder waste composite was evaluated as a sustainable and low‐cost adsorbent for the removal of the cationic dye Methylene Blue (MB) and the anionic dye Reactive Black 5 (RB5). The valorization of quartzite waste as a silica source represents an environmentally attractive strategy to mitigate disposal impacts while enabling the development of functional materials. Structural and surface characterizations performed by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) specific surface area revealed a composite containing approximately 10 wt.% carbon coating the quartzite surface, exhibiting a rough morphology and a specific surface area of 53.62 m 2 g – 1 . Batch adsorption experiments indicated that the kinetic behavior was best described by the Avrami model, with rate constants of 0.3309 s −1 for MB and 0.0377 s −1 for RB5 at 25°C. Equilibrium data were well fitted by the Langmuir model for MB and the Sips model for RB5, yielding maximum adsorption capacities of 11.63 mg g −1 and 7.99 mg g −1 , and constraints K L = 3.550 × 10 −3 L mg −1 (MB) and K S = 0.1644 L g −1 (RB5), respectively. Thermodynamic analysis demonstrated that dye adsorption was spontaneous and endothermic, as evidenced by the significant decrease in |Δ G | values (19.0 kJ mol –1 for MB and 6.4 kJ mol –1 for RB5), indicating enhanced affinity at higher temperatures. Furthermore, the adsorption mechanism was predominantly governed by chemisorption interactions, especially n –π and π–π interactions, reflecting strong adsorbent–adsorbate affinity. In addition, an ion‐exchange mechanism may occur as function of the pH and its relationship with point of zero charge. Overall, the results highlight the composite as a promising candidate for textile wastewater treatment applications and demonstrate its potential contribution to circular economy strategies through the valorization of industrial mineral waste.