Water treatment for efficient removal of crystal violet dye using calcium-enhanced hollow carbon-based adsorbents obtained from the sustainable conversion of waste tires via pyrolysis process

In this study, a novel solid pyrolytic adsorbent was synthesized from waste tires and evaluated for removing organic pollutants from water. Comprehensive characterization (SEM, TEM, XRD, FTIR, EDS, Raman, BET) revealed a unique hollow carbonaceous framework incorporating nanoparticles, nanotubes, fullerenes, carbon black, and Ca(OH)₂ as an inherent catalytic component, with a specific surface area of 50 m²/g. The material exhibited a negative zeta potential (-18.4 mV), confirming its strong affinity toward cationic pollutants. Adsorption experiments demonstrated exceptional crystal violet (CV) removal performance, achieving a maximum adsorption capacity of 509.4 mg/g at neutral pH (7). Moreover, the adsorbent retained high efficiency over seven reuse cycles in tap water, highlighting its regeneration ability by the existing ions and operational stability. The combination of low-cost synthesis, sustainable valorization of waste tires, and superior dye removal efficiency positions this pyrolytic material as a promising candidate for scalable and eco-friendly wastewater treatment. • Green valorization of waste tires into functional environmental materials. • Sustainable carbonaceous adsorbent produced via waste tire pyrolysis. • High removal capacity of crystal violet dye (up to 509.4 mg/g). • Calcium-rich matrix enhances catalytic and adsorptive performance. • Self-catalyzed pyrolysis generates diverse carbon allotropes.