Facile synthesis of hierarchical structure of NaY zeolite using silica from cogon grass for acid blue 185 removal from water

Abstract

Abstract Facile preparation of hierarchical structure NaY zeolite from cogon grass silica is synthesized by microwave-assisted hydrothermal method and subsequently desilicated in ultrasonic-assisted alkaline treatment. This work aims to improve the removal efficiency of acid blue-185 (AB-185) by using hierarchical NaY zeolite. When treated the parent NaY in NaOH solution with various concentrations (0.1, 0.5 and 1.0 M), the Si/Al ratios and micropore surface area decrease but increase a maximum pore size distribution of mesopore with the NaOH concentration due to the desilication effect. Moreover, the mesopore surface area and volume significantly increase and reach to the maximum value with a concentration of 0.5 M (132 m2 g−1 and 0.12 cm3 g−1). Consequently, the NaY (0.5 M) gives the highest percentage of AB-185 removal (80 ± 1.2 %) at a pH of 5 owing to the abundant adsorption sites and the eased accessibility of dye molecules. The adsorption data fit well with the Langmuir isotherm rather than Freundlich isotherm models with a correlation coefficient of 0.99. Maximum adsorption capacity of AB-185 on NaY (0.5 M) is larger than that on the parent NaY (84.5 mg/g vs 19.4 mg/g). In addition, the adsorption process of AB-185 on NaY (0.5 M) is more favorable by the pseudo-second-order kinetic model indicating the main rate-control is chemisorption. The existence of interactions between AB-185 and the NaY (0.5 M) is confirmed by FTIR and XPS. The reusability of the NaY (0.5 M) preserves original adsorption capacity, up to five cycles indicating a promising adsorbent for water treatment.