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1.
Sci Total Environ ; 791: 148281, 2021 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-34119786

RESUMEN

The use of magnetic lanthanum-based materials for phosphate removal from river water has gained increasing attention. However, challenges to produce and use lanthanum-based materials in large-scale or pilot-scale studies remain. In this work, a kilogram-scale Fe3O4/La(OH)3 magnetically recyclable composite for removing phosphate from river water was developed through a low-temperature precipitation route. The composite was used to remove phosphate from river water at both bench- and pilot-scales. Based on the bench-scale tests, the developed Fe3O4/La(OH)3 composite was found to have excellent magnetic particle separation efficiency (>98%) and a sorption capacity of 11.77 mg/g for phosphate. A 1.0 g/L dosage of the composite in the river water sample was able to selectively reduce the phosphate level from 0.089 to 0.005 mg/L in 60 min over five consecutive adsorption cycles. At the pilot-scale, the Fe3O4/La(OH)3 composite only achieved 36.0% phosphate removal efficiency, which is considerably different from the bench-scale results over an operational time of five months and a total treatment volume of 300 m3. This significantly reduced removal efficiency is mainly attributable to turbidity, suspended solids, and organic matter in the river water and the deteriorated magnetic separation efficiency. This study revealed potential challenges and shed new insights on moving magnetic nanocomposite-based technology from the bench-scale to the pilot-scale, which can inspire new designs for the application of similar technology.


Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Adsorción , Lantano , Fosfatos/análisis , Ríos , Agua , Contaminantes Químicos del Agua/análisis
2.
Chemistry ; 23(20): 4827-4836, 2017 Apr 06.
Artículo en Inglés | MEDLINE | ID: mdl-28194825

RESUMEN

Two isomeric bottlebrush polyamides P-1 and A-1, with the same repeating monomer dipole units aligned along the polymer backbone in pseudo-parallel and pseudo-antiparallel fashion, respectively, were synthesized and characterized. Both polymers can form thermoreversible gels with aromatic solvents but P-1 was found to show inferior gelation strength compared with that of A-1. Furthermore, despite their close structural resemblance, a 1:1 mixture of the P-1 and A-1 polymers was shown to exhibit self-sorting in the gel state. Gel formation was found to be a kinetically trapped process through hydrogen bonding, π-π stacking interactions, and side chain interdigitation. The different gelation and self-sorting properties can be explained by the local dipole-dipole interactions originating from the different modes of backbone dipole alignment. In single gel systems, the antiparallel-aligned dipoles in A-1 facilitated a more compact molecular packing owing to the enthalpically more favorable polymer chain association. On the other hand, the parallel-aligned dipoles in P-1 gave rise to a less stable head-to-head packing, which had difficulties to convert to the more stable head-to-tail packing in a kinetically trapped environment. In the mixed gel system, it is the unfavorable hetero-polymer mismatch dipole-dipole interaction that inhibited the mixing of the A-1 and P-1 polymers and led to self-sorting.


Asunto(s)
Geles/química , Polímeros/química , Amidas/química , Rastreo Diferencial de Calorimetría , Enlace de Hidrógeno , Isomerismo , Espectroscopía de Resonancia Magnética , Conformación Molecular , Peso Molecular , Reología , Dispersión del Ángulo Pequeño , Solventes/química , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos X
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