Preparation and characterization of different zeolites from andesite rock: Product evaluation for efficient dye removal

Abstract Synthetic Zeolite mixture (ZM) containing Analcime (ANA), Wairakite (W), and Phillipsite (PHI) was produced by alkali activation of andesite rock (AR) under hydrothermal conditions of 1.0&3.0 M NaOH, 100 °C, and duration of 1–5 days. The main affecting parameters for ZM phase crystallization were alkalinity, solution chemistry, parent rock dissolution rate, and reaction duration. The low alkali concentration was advantageous for ANA formation, and the hetero cationic slurry environment containing sodium and calcium resulted in co-crystallization of ANA-W zeolite series in the same pot. High alkalinity unfavored ANA persistence but was more suitable for PHI domination. The FT-IR results confirmed the conversion of the precursor rock into zeolites, whereas the measured surface area indicated the enlargement of the BET of the rock from 2.62 into 91.4 m2/g after zeolitization. The rock and synthetic product were identified using the X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), specific surface area (BET), and the structural groups for AR and ZM were tested using the FT-IR technique. The phase internal structures and microanalysis are monitored by the Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDS). Zeta potential of samples was measured using a particle size analyzer. For economic aspect, ZM formed at low alkali content of 1.0 M NaOH, 100 °C, and 5 days was evaluated for methylene blue dye removal as a model of textile wastewater. The effect of pH, contact time, initial concentration and zeolite dose on adsorption has been investigated. Zeta potential measurements revealed that, the pH pzc was 1.9. The maximum sorption performance was found to be 95.7% at 10 pH within 240 min and 1.5 g/L zeolite dosage. Furthermore, the application of the zeolitic product on a synthetic simulated effluent composed of different dyes and salts implied a removal efficiency of 92.63%. The isothermal investigation of Langmuir and Freundlich models at different temperatures revealed that, MB adsorption using the formed zeolite was adapted to the Freundlich isotherm. The dye removal was matched with the pseudo-first kinetic model. Also, the high efficiencies in the removal of dye molecules through 5 consecutive cycles were demonstrated in the regeneration experiments.