Effects of waste fluid catalytic cracking on the properties of semi-hydrate phosphogypsum

Phosphogypsum poses environmental problems; therefore, this research paper examines and discusses the possibilities of effective utilization of phosphogypsum as a binding material. However, water-soluble primary calcium phosphate and fluoride, while remaining in phosphogypsum as unwanted impurities, makes it unsuitable for the production of gypsum-based products. This paper describes the process of adsorbing hazardous phosphogypsum impurities by zeolite. The waste fluid catalytic cracking (FCC) process catalyst based on synthetic zeolite Y was used in the experimental research described in this paper. In order to improve the properties of the binding material from phosphogypsum the ultrasound treatment of phosphogypsum paste was used. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer (EDS), the compressive strength of phosphogypsum specimens. The results showed, that the compressive strength increased about four times while using ultrasound treatment and waste FCC catalyst (zeolite Y) addition from 0.5 until 10% compared with specimens without zeolite and sonication. With the increase of zeolite by more than 10%, compressive strength decreased additionally. It was also determined that phosphogypsum paste used with waste FCC catalyst (zeolite Y), which was treated with ultrasound was an effective additive for neutralizing the acidic phosphogypsum medium. It neutralized the acidic admixtures, regulated the phosphogypsum hydration and the time setting duration as well. Additives modified the microstructure of hardened gypsum and increase its strength.