81 research outputs found
Phosphorus removal from eutrophic waters with an aluminium hybrid nanocomposite
An excess of phosphorus (P) is the most common cause of eutrophication of freshwater bodies. Thus, it is imperative to reduce the concentration of P to prevent harmful algal blooms. Moreover, recovery of P has been gaining importance because its natural source will be exhausted in the near future. Therefore, the present work investigated the removal and recovery of phosphate from water using a newly developed hybrid nanocomposite containing aluminium nanoparticles (HPN). The HPN-Pr removes 0.80 ± 0.01 mg P/g in a pH interval between 2.0 and 6.5. The adsorption mechanism was described by a Freundlich adsorption model. The material presented good selectivity for phosphate and can be regenerated using an HCl dilute solution. The factors that contribute most to the attractiveness of HPN-Pr as a phosphate sorbent are its moderate removal capacity, feasible production at industrial scale, reuse after regeneration and recovery of phosphate.The authors acknowledge the Foundation for Science and Technology (FCT) Project SFRH/BD/39085/2007 for the financial support
Nanostructured Metal Oxide Sorbents for the Collection and Recovery of Uranium from Seawater
The ability to collect uranium from
seawater offers the potential
for a long-term green fuel supply for nuclear energy. However, extraction
of uranium, and other trace minerals, is challenging because of the
high ionic strength and low mineral concentrations in seawater. Herein
we evaluate the use of nanostructured metal oxide sorbents for the
collection and recovery of uranium from seawater. Chemical affinity,
chemical adsorption capacity, and uptake kinetics of sorbent materials
were evaluated. Materials with higher surface area clearly produced
better sorbent performance. Uptake kinetics showed that the materials
could rapidly equilibrate in a few hours with effective solution contact.
Manganese, iron oxide, and especially Mn–Fe nanostructured
composites provided the best performance for uranium collection from
seawater. The preferred materials were demonstrated to extract uranium
from natural seawater with up to 3 mg U/g-sorbent in 4 h of contact
time. Inexpensive nontoxic carbonate solutions were demonstrated to
be an effective and environmentally benign method of stripping the
uranium from the metal oxide sorbents. Various formats for the utilization
of the nanostructured metals oxide sorbent materials are discussed,
including traditional methods and nontraditional methods such as magnetic
separation
Manganese Doping of Magnetic Iron Oxide Nanoparticles: Tailoring Surface Reactivity for a Regenerable Heavy Metal Sorbent
A method for tuning the analyte affinity of magnetic,
inorganic
nanostructured sorbents for heavy metal contaminants is described.
The manganese-doped iron oxide nanoparticle sorbents have a remarkably
high affinity compared to the precursor material. Sorbent affinity
can be tuned toward an analyte of interest simply by adjustment of
the dopant quantity. The results show that following the Mn doping
process there is a large increase in affinity and capacity for heavy
metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements
were carried out for the removal of cadmium from river water and showed
significantly higher loading than the relevant commercial sorbents
tested for comparison. The reduction in Cd concentration from 100
ppb spiked river water to 1 ppb (less than the EPA drinking water
limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped
iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were
able to load ∼1 ppm of Cd followed by complete stripping and
recovery of the Cd with a mild acid wash. The Cd loading and stripping
is shown to be consistent through multiple cycles with no loss of
sorbent performance
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