Improving the ammonium ion uptake onto natural zeolite by using an integrated modification process

Detailed investigation on the development of physical and chemical properties of a natural calcium-rich zeolite modified by an integrated process, as well as the relation between the development and ammonium ion uptake (AIU), was conducted. This process consisted of pretreatment (grinding and sieving), sodium salt modification and calcination. Both pretreatment and salt modification largely increased BET surface area, total pore volume and average pore diameter of the raw zeolite. Individual calcination at temperature above 150 °C caused framework collapse, losses of partial clinoptilolite and production of X-ray amorphous material, resulting in pore blockage and the decreases in pore volume and BET surface area. However, the introduction of sodium ion enhanced the heat resistance of the raw material from 150 to 400 °C, and Na+ ion treatment followed by calcination could effectively improved pore and surface properties of zeolite, thus leading to the significant enhancement in ammonium ion exchange and adsorption capabilities.