Efficient adsorptive removal of Cobalt(II) ions from water by dicalcium phosphate dihydrate. (1st April 2021)

• Record Type: Journal Article
• Authors: Vivas, Eleazer L.; Cho, Kuk
• Is Part Of: Journal of environmental management. Volume 283(2021)
• Publication Date: 2021-04-01
• Subjects: Adsorption -- Brushite -- Kinetics -- Monetite -- Cobalt-60; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.111990
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Although the radionuclide 60 Co is widely used, its presence in various effluents demands its removal to preclude environmental pollution and detrimental effects on human health. This study investigated the batch adsorption performance of a potential cobalt adsorbent, dicalcium phosphate dihydrate (DCPD), in immobilizing Co 2+ from water. The influences of solution pH, contact time, initial concentration, and competing cations were examined and discussed. Stable cobalt uptake was observed at pH 4–8. The sorption kinetics showed a multi-stage uptake profile, implying that several mechanisms are involved in the adsorption process. Microscopy and structural analysis revealed that DCPD decomposes to its anhydrous form during adsorption, which explains the multistep curve over the entire adsorption period. However, the non-apatitic transformation is not exclusive to cobalt uptake. Intraparticle diffusion also contributed to the overall removal kinetics of Co 2+ from water. Considering the Sips isotherm model, the maximum Co 2+ adsorption capacity of DCPD was 441 mg g −1 . Cobalt uptake selectivity dropped in the presence of Ca 2+ ions, from 1.21 × 10 4 to 207 mL g −1, indicating DCPD would be more applicable in treating soft 60 Co-contaminated waters. Structural analysis, elemental mapping, and qualitative analysis of solid residues confirmed that ion exchange is involved in the removal of cobalt from aqueous solutions. Graphical abstract: Image 1 Highlights: Dicalcium phosphate dihydrate (DCPD) exhibited multistage kinetic Co 2+ uptake profile. DCPD transformed to its anhydrous form during adsorption. . DCPD adsorbent exhibited high Co 2+ uptake in water ( q max ≅ 441 mg g −1 ). . DCPD removed at least 90% of Co 2+ ions in water at C o ≤ 50 mg L −1 . DCPD demonstrated potential use in the immobilization of 60 Co from softer wastewaters.