Synthesis of Carbon Capturing NaX Zeolite from Rice Husk Ash: Evaluation of Its Adsorption Properties

Abstract

This study presents the synthesis and characterization of zeolites (S-1, S-2) from a commercial silica source (sodium silicate) and zeolites (RHA-1, RHA-2) derived from rice husk ash (RHA) for the efficient adsorption of Methylene Blue (MB) dye from aqueous solutions. The synthesized zeolites were characterized using various analytical techniques, including ATR-FTIR, WD-XRF, XRD, FE-SEM, and BET-N₂ adsorption analysis. FE-SEM analysis demonstrated that all synthesized zeolites exhibit a combination of cubic and octahedral morphologies. N₂ adsorption–desorption studies indicated that the BET surface areas of zeolites S-2 and RHA-2 measure 658.68 and 559.63 m² g^–1 and are fitted with Type IV adsorption isotherms. Batch adsorption experiments optimized key parameters, demonstrating that RHA-2 achieved 95.83% MB dye removal in just 20 min using 0.02 g of adsorbent at neutral pH and 25 (±1) °C temperature. The Langmuir isotherm model exhibited the most accurate match for the adsorption process with an adsorption capacity (q_max) of 40.65 mg g^–1, which adhered to pseudo-second-order kinetics. Regeneration tests confirmed reusability with efficiency decreasing to 90.1% after five cycles due to degradation. Compared to S-2, RHA-2 exhibited superior adsorption performance, highlighting its potential as a cost-effective, sustainable, and eco-friendly adsorbent for industrial wastewater treatment.