X-type zeolites use an ion-exchange mechanism to capture and retain heavy metals for soil and water remediation. Zeolites are hydrated aluminosilicate minerals characterized by a three-dimensional open structure. Their cation exchange capacity (CEC), large surface area, and porosity allow the absorption and encapsulation of pollutants. The geopolymer product, containing the zeolites in formation, can be applied directly to contaminated soil, thus immobilizing toxic heavy metals within the zeolite structure during growth and formation.
The new process synthesizes geopolymers and zeolites from fly ash, a by-product of thermal power plants. Hydrothermal synthesis uses low incubation temperatures (35-40 °C). The low-temperature seawater method produces up to eight times the zeolites compared to traditional techniques, and produces them more cheaply.