One-step high efficiency synthesis of zeolite from fly ash by mechanochemical method as a low-cost adsorbent for cadmium removal

Abstract

The hydrothermal synthesis of zeolite from fly ash is a time-consuming process with a low conversion rate. Mechanochemical activation is commonly employed as a green and moderate pre-treatment process for surface modification purposes. This study proposes a one-step high efficiency synthesis of zeolite from fly ash using the mechanochemical method. The ball milling modification is conducted simultaneously with the zeolite synthesis process, reducing the overall synthesis time to a significant extent (3 h being determined as the optimal synthesis time). The findings reveal that P1 zeolite can be effectively synthesized under the following conditions: a sodium hydroxide concentration of 2 mol L−1, a synthesis temperature of 130 °C and a ball milling frequency of 30 Hz. Moreover, the synthesized zeolite exhibits a maximum Cd2+ adsorption capacity of 130.68 mg/g at pH= 5, following pseudo-second-order kinetics and Langmuir adsorption isotherm. This study not only simplifies the production process and saves energy but also yields zeolite with smaller particle sizes and higher purity. By utilizing the mechanochemical method, the disposal of solid waste can be made environmentally friendly, convenient, and economically beneficial.