An all-green strategy to convert waste to new material by a solvent-free method for heavy metal adsorption

Zeolites are widely used as adsorbents to mitigate water and air pollution, but conventional hydrothermal synthesis requires a large volume of aqueous solvent and produces alkaline wastewater. Zeolite in this study was synthesized by a solvent-free method, eliminating the need for a solvent and providing a green alternative to the hydrothermal procedure. In addition, fly ash was used as raw material for zeolite due to its high proportions of Si and Al. It was determined by several structural and morphological characterization techniques that the synthesized zeolite was of the analcime type with porosity comparable to that of other known zeolite adsorbents. Several experiments with Pb 2+ and Cu 2+ solutions under different contact times, initial ion concentrations, and temperatures were conducted to investigate the adsorption behaviors of analcime zeolite toward those heavy metals. This investigation illustrates a waste-to-value approach and a green process to produce material that reduces the impact of heavy metal pollutants on the environment, thus promoting a sustainable and circular economy.