Solarization of the zeolite production: Calcination of kaolin as proof-of-concept

The current production of zeolites from natural sources requires high temperatures to achieve a phase change in the feedstock materials. Thermal processes such as calcination are energy-consuming and industry relies on fossil fuels to generate the necessary heat, which is neither sustainable nor environmental. This study presents for the first time the treatment of aluminosilicate clay kaolin in a solar reactor to produce metakaolins that are eligible as precursors for zeolite synthesis. Kaolin was loaded in a rotary kiln and a solar simulator was used for calcination at temperatures of 700–1000 °C for 2 h. After the solar calcination process, solar-produced metakaolins were used to synthesize zeolite 4 A and zeolite 13X by hydrothermal route. The kaolin, metakaolin, and product samples obtained were analyzed by XRD, XRF, FTIR, and FE-SEM. Results show that solar-calcined kaolin was as good and efficient as the conventionally calcined one in terms of supplying the metakaolin for zeolite synthesis. Often disregarded by researchers, high-temperature calcination of the kaolin was proved to be an alternative way for the synthesis of zeolite 13X without using an extra silica source, which was achieved for the first time. The overall results suggest that solar calcination is a good alternative to mass produce meta forms of the minerals to be used in the synthesis of value-added products such as zeolites.