Control of internal phosphorus release from sediments using magnetic lanthanum/iron-modified bentonite as active capping material. (September 2020)

• Record Type: Journal Article
• Authors: Lin, Jianwei; Zhao, Yuying; Zhan, Yanhui; Wang, Yan
• Is Part Of: Environmental pollution. Volume 264(2020)
• Publication Date: 2020-09
• Subjects: Magnetic lanthanum/iron-modified bentonite -- Magnetic iron-modified bentonite -- Sediment -- Internal phosphorus loading -- Capping -- Release control; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2020.114809
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: The non-magnetic capping materials are difficult to be recycled from the water bodies after their application, leading to the increase in the cost of the sediment remediation. To address this issue, a capping material, i.e., magnetic lanthanum/iron-modified bentonite (M-LaFeBT) was prepared by loading lanthanum onto a magnetic iron-modified bentonite (M-FeBT) and used to control the internal phosphorus (P) loading in this study. To determine the capping efficiency and mechanism of M-LaFeBT, the impact of M-LaFeBT and M-FeBT capping on the mobilization of P in sediments was investigated, and the stabilization of P bound by the M-LaFeBT and M-FeBT capping layers was evaluated. Results showed that M-LaFeBT possessed good magnetic property with a saturated magnetization of 14.9 emu/g, and exhibited good phosphate adsorption ability with a maximum monolayer sorption capacity ( Q MAX ) of 14.3 mg P/g at pH 7. Moreover, M-LaFeBT capping tremendously reduced the concentration of soluble reactive P (SR-P) in the overlying water (OL-water), and the reduction efficiencies were 94.7%–97.4%. Furthermore, M-LaFeBT capping significantly decreased the concentration of SR-P in the pore water and DGT (diffusive gradient in thin films)-labile P in the profile of OL-water and sediment. Additionally, most of P bound by the M-LaFeBT capping layer (approximately 77%) was stable under natural pH and reducing conditions. The phosphate adsorption ability for M-LaFeBT was much higher than that for M-FeBT, and the Q MAX value for the former was 4.86 times higher than that for the latter. M-LaFeBT capping gave rise to a higher reduction of DGT-labile concentration in the profile of OL-water and sediment than M-FeBT capping. The P adsorbed by the M-LaFeBT capping layer was more stable than that by the M-FeBT capping layer. Results of this study demonstrate that M-LaFeBT is promising for utilization as an active capping material to intercept sedimentary P release into OL-water. Graphical abstract: Image 1 Highlights: M-LaFeBT (14.3 mg/g) had higher phosphate uptake ability than M-FeBT (2.44 mg/g). M-LaFeBT capping significantly reduce concentration of SR-P in overlying water. M-LaFeBT had higher reduction efficiency of DGT-labile P in sediment than M-FeBT. P bound by M-LaFeBT was more stable than that by M-FeBT.