Abstract
In a scenario of high demand, low availability, and high economic value, the recovery of rare-earth metals from wastewater is economically and environmentally attractive. Bioadsorption is a promising method as it offers simple design and operation. The aim of this study was to investigate lanthanum bioadsorption using a polymeric bioadsorbent of sericin/alginate/poly(vinyl alcohol)-based biocomposite. Batch system assays were performed to evaluate the equilibrium, thermodynamics, regeneration, and selectivity of bioadsorption. The maximum capture amount of lanthanum at equilibrium was 0.644 mmol/g at 328 K. The experimental equilibrium data were better fitted by Langmuir and Dubinin–Radushkevich isotherms. Ion exchange mechanism between calcium and lanthanum (2:3 ratio) was confirmed by bioadsorption isotherms. Thermodynamic quantities showed that the process of lanthanum bioadsorption was spontaneous (−17.586, −19.244, and −20.902 kJ/mol), endothermic (+15.372 kJ/mol), and governed by entropic changes (+110.543 J/mol·K). The reusability of particles was achieved using 0.1 mol/L HNO3/Ca(NO3)2 solution for up to five regeneration cycles. The bioadsorbent selectivity followed the order of lanthanum > cadmium > zinc > nickel. Additionally, characterization of the biocomposite prior to and post lanthanum bioadsorption showed low porosity (9.95 and 12.35%), low specific surface area (0.054 and 0.019 m2/g), amorphous character, and thermal stability at temperatures up to 473 K. This study shows that sericin/ alginate/poly(vinyl alcohol)-based biocomposites are effective in the removal and recovery of lanthanum from water.
Highlights
Rare-earth metals (REMs) consist of scandium, yttrium, and 15 lanthanides, i.e., lanthanum–lutetium [1]
This study shows that sericin/ alginate/poly(vinyl alcohol)-based biocomposites are effective in the removal and recovery of lanthanum from water
The equilibrium studies for lanthanum bioadsorption on the sericin/alginate crosslinked with poly(vinyl alcohol) (SAPVA) particles were performed at temperatures of 298, 313, and 328 K
Summary
Rare-earth metals (REMs) consist of scandium, yttrium, and 15 lanthanides, i.e., lanthanum–lutetium [1]. REMs are known as the “vitamins of the industry” [2]. These metals are found mainly in China (55 million tons), United States (13 million tons), India (3.1 million tons), Brazil (2.2 million tons), and Australia (2.1 million tons) [3,4]. China concentrates about 97% of the worldwide REM production [4,5]. Lanthanum is a relevant and reactive REM due to its optical, magnetic, and chemical properties [6,7]. The concentration of lanthanum found in the earth’s crust is only 0.002% [5]. Lanthanum is usually used in high-tech applications, such as batteries, catalysts, ceramics, glasses, and superalloys [7,8]
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