An enhanced removal of Malachite Green Oxalate using recycled porcelain tile waste: A sustainable and high-efficiency adsorbent

This study introduces a sustainable and cost-effective approach for the removal of malachite green oxalate (MGO) dye from aqueous solutions over recycled porcelain and ceramic building tile waste (BTW) as an adsorbent surface. The physicochemical properties of BTW were characterized using X-rays diffraction (XRD), X-ray fluorescence (XRF), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), Brunner-Emmett-Teller (BET), and zeta potential analysis, revealing a porous structure rich in SiO 2 , Al 2 O 3 , CaO, and Fe 2 O 3 , with nanoscale surface irregularities (<20 nm), high surface area, and a negative surface charge. Adsorption experiments were conducted to optimize operational parameters, including contact time, adsorbent amount, temperature, and dye concentration. Under optimal conditions (30 minutes, 0.02 g BTW, 25 mg·L −1 MGO dye, and 328 K), a maximum removal efficiency of 98% was achieved. Thermodynamic analysis indicated a spontaneous (ΔG° < –11.170 kJ·mol −1 ) and endothermic (ΔH° = +0.178 kJ·mol −1 ) process, driven by entropy gain (ΔS° = +34.600 J·mol −1 ·K −l ), suggesting a physisorption mechanism. Kinetic modelling revealed that the adsorption process follows a pseudo second-order model (R 2 = 0.9992), indicating strong physical adsorption with partial chemisorption characteristics. Compared to other adsorbents, BTW demonstrated superior performance at lower dosage and shorter contact time, highlighting its potential as a low-cost, environmentally friendly material for dye-contaminated wastewater treatment.