An experimental study of the suitable process of modifying clinoptilolite for the treatment of high-fluoride groundwater

Abstract：A suitable process to modify natural clinoptilolite from Beipiao area of Liaoning Province was determined by using contrast experiments of three different modifying methods. The process includes: (1) roasting the zeolite at 700℃ for 5 hours in muffle furnace, (2) soaking it in hydrochloric acid of 10% concentration for 12 hours, (3) using clear-water to wash it to neutrality, then boiling it in the liquid of hydroxide sodium of 2% concentration for 6 hours, (4) washing it to neutrality by using the water of pH=3, and soaking it in alum liquid of 10% concentration at the temperature of 70℃ for 24 hours, and (5) washing it by clear-water and drying it at the temperature of 80℃. For the modified clinoptilolite, the penetrability of interior pores and specific surface areas are augmented, and the adsorbability of fluoride is increased together with the decrease of silicon-aluminum ratio. Therefore, the high-energy of defluoridation is shown with the increasing ion-exchange capability of this modified zeolite.