Recycling silica-rich wastes in sustainable mechanochemical-hydrothermal production of zeolite Y for ammonia remediation in aquaculture

Silica-rich dealuminated kaolin (SRDK), produced as a by-product in alum industry, is still considered as waste materials in Egypt. Expansion of aquaculture along the banks of Nile River and its canals negatively affects water quality due to formation of ammonia. The current investigation aims to eradicate ammonia from aquaculture systems via an integrated approach of converting SRDK to pure zeolite Y in two-step process. The main constituent of SRDK is amorphous silica with a small amount of unreacted metakaolin and crystalline silica. XRD and FTIR proved that zeolitization started by mechanochemical activation at room temperature. However, hydrothermal treatment at 105 degrees C and 125 degrees C produces zeolite Y with different Si/Al ratios and microcrystalline quartz is completely reacted at 125 degrees C. The adsorption isotherm data of ammonia was best fitted by Freundlich model. Zeolite Y produced from 80% SRDK and 20% metakaolin at 125 degrees C has a high efficiency to remove ammonia from aquaculture.

Automated summary

Silica-rich dealuminated kaolin (SRDK), a waste material in Egypt, can be converted into pure zeolite Y through a two-step process for the removal of ammonia from aquaculture. SRDK consists of amorphous silica with some unreacted metakaolin and crystalline silica. Zeolitization starts through mechanochemical activation at room temperature and is further enhanced by hydrothermal treatment at different temperatures. The zeolite with the highest efficiency for ammonia removal is obtained from a mixture of 80% SRDK and 20% metakaolin at 125 degrees C.