Adsorption of Methylene Blue from High-Salt Wastewater by Construction and Demolition Waste-Based Chabazite

In this study, construction and demolition waste (CDW) were selected as raw material to prepare chabazite by alkali fusion hydrothermal method. The obtained chabazite was utilized in adsorbing methylene blue from high-salt wastewater. The physical and chemical properties of the chabazite were characterized by XRD, FTIR, and N2 adsorption/desorption isotherms. The synthesized chabazite possessed typical phase structure and functional groups. Its specific surface area (111.97 m2/g) and total pore volume (0.488 cm3/g) increased by about 8.26 and 6.78 times than that of CDW, respectively. The adsorption capacity on the chabazite at c(NaCl) = 7000 mg/L reduced to 77.28% of that at c(NaCl) = 0 mg/L, indicating that salinity had a negative effect on the adsorption. The Langmuir adsorption isotherm and pseudo-second-order kinetic model could describe the adsorption process of methylene blue on the synthesized chabazite. The saturated adsorption capacity of chabazite for methylene blue reached up to 80.61 mg/g under c(NaCl) = 5000 mg/L at 25 & DEG;C, which was about 4 times that of CDW, showing the remarkable adsorption performance at high salinity. The adsorption process at high-salt condition was spontaneous, exothermic, and tended to be ordered. This study indicates that it is feasible to prepare chabazite from CDW, and the obtained chabazite is a novel and effective adsorbent in treating high-salt wastewater.