Potential Desalination of Coal Seam Gas Coproduced Water Using Zeolite

Abstract

Natural clinoptilolite type zeolite was examined for its potential to treat coal seam gas (CSG) water and remove sodium ions to lower sodium adsorption ratio and reduce pH. The effectiveness of unmodified and modified natural zeolite is due to their regular composi - tion and open porous structure, high exchange capacity, mechanical strength and stability, and consistency in particle size. The effects of acid modification in bringing about changes to the physicochemical properties of clinoptilolite underpin the effectiveness of this mate rial for treatment of CSG saline water. The sodium adsorption capacity of acid-modified zeolite increases up to three times greater than that of the unmodified zeolite. The atomic percentage and binding energies of the chemical elements comprising zeolite are changed significantly following the acid modification. The Si/Al atomic ratio increases with increasing sulfuric acid concentration. Dealumination is the main reason for the increase in the surface charge and cation exchange capacity of clinoptilolite after acid modification. It is due to the increased defects in the crystal structure/lattice, which result in increasing numbers of charge vacancies. Sodium-rich synthetic zeolites 4A and Na ─ Y after acid modification are also examined by following the dissolution of the first-order fast kinetics and recrystallization processes which can be homogeneous or heterogeneous.