Prepared 13X Zeolite from Local Natural Clay as a Promising Adsorbent for the Removal of Malachite Green Dye from Aqueous Medium

Abstract

Textile dyeing processes generate large amounts of wastewater containing various dye compounds, especially malachite green, which raises environmental concerns due to its persistence in water and potential toxicity. This study describes the synthesis of a new zeolite derived for the first time from red clay deposits in the Adrar region (Algeria). The X-ray fluorescence (XRF) analysis was conducted to investigate the chemical composition of the raw red clay, revealing SiO₂ and Al₂O₃ as its major components. Zeolite 13X was produced by initially mixing natural red clay with NaOH, followed by calcination at 600 °C. Various characterization techniques, including XRD, SEM, and FTIR, were performed to verify the structure, surface morphology, and chemical properties of the synthesized zeolite. Malachite green (MG) adsorption tests were conducted on the material, with key parameters like contact time, pH, temperature, and initial dye concentration optimized to enhance removal capacity. The results indicated that the isotherms were accurately modeled by the Langmuir isotherm, which confirms homogenous and monolayer sorption together with a highest removal capacity of 91.92 mg/g. It was found that the pseudo-second-order model was the most suitable for explaining with \({R}^{2}=0.994\). Calculations were also performed for thermodynamic parameters, such as variations in standard entropy (ΔS), enthalpy (ΔH), and Gibb's free energy (ΔG). The results show that the sorption process of MG dye by zeolite 13X is spontaneous and exothermic. Furthermore, superior regeneration was observed for 13X-NRC using a 50/50 (v/v) water–ethanol mixture over four cycles. The 13X zeolite derived from local red clay provides a cost-effective and efficient solution for the removal of MG dye from wastewater.