Facile synthesis of NaY molecular sieve by low-temperature ultrasonic gelling method for efficient adsorption of rare-earth elements

Abstract

Due to the lack of rare earth resources, the recovery of rare earth ions from industrial wastewater has been widely concerned. In this work, NaY molecular sieve was synthesized at 50–90 °C for 3–10 h without template and guide agent by low-temperature ultrasonic gelling method, and it was examined as the adsorbent to recover and enrich La3+ and Eu3+ in synthetic rare earth liquids. The properties of the synthesized NaY crystallization at 90 °C for 5 h were determined as follows: relative crystallinity of 99.49%, average particle size of 300 nm, specific surface area of 873.66 m2/g, and average aperture of 0.5617 nm. When the adsorption temperature was 25 °C, the pH was about 7, the initial concentrations of La3+ and Eu3+ were 227.00 mg/L and 195.30 mg/L, respectively, the amount of NaY was 0.01 g, and the volume of the rare earth simulant was 10 ml, the unit adsorption capacity and adsorption efficiency of La3+ were respectively 174.12 mg/g and 75.30%, and the unit adsorption capacity and adsorption efficiency of Eu3+ were 147.47 mg/g and 75.51%, respectively. After four cycles, the unit adsorption efficiency of La3+ and Eu3+ were still respectively 93.20 mg/g and 91.00 mg/g. The adsorption process showed a closer agreement with Langmuir isotherm and quasi-second-order kinetics model. The results indicate that this NaY molecular sieve is a promising adsorbent for rare earth recycling and enrichment from wastewater.