2 research outputs found
Adsorption of Arsenic on Polyaluminum Granulate
The kinetics and efficiencies of arsenite and arsenate
removal
from water were evaluated using polyaluminum granulates (PAG) with
high content of aluminum nanoclusters. PAG was characterized to be
meso- and macroporous, with a specific surface area of 35 Ā± 1
m<sup>2</sup> g<sup>ā1</sup>. Adsorption experiments were conducted
at pH 7.5 in deionized water and synthetic water with composition
of As-contaminated groundwater in the Pannonian Basin. AsĀ(III) and
AsĀ(V) sorption was best described by the Freundlich and Langmuir isotherm,
respectively, with a maximum AsĀ(V) uptake capacity of ā¼200
Ī¼mol g<sup>ā1</sup> in synthetic water. While AsĀ(III)
removal reached equilibrium within 40 h, AsĀ(V) was removed almost
entirely within 20 h. Micro X-ray fluorescence and electron microscopy
revealed that AsĀ(III) was distributed uniformly within the grain,
whereas AsĀ(V) diffused up to 81 Ī¼m into PAG. The results imply
that AsĀ(V) is adsorbed 3 times faster while being transported 10<sup>5</sup> times slower than AsĀ(III) in Al hydroxide materials
Quantification of Carbon Nanotubes in Environmental Matrices: Current Capabilities, Case Studies, and Future Prospects
Carbon
nanotubes (CNTs) have numerous exciting potential applications
and some that have reached commercialization. As such, quantitative
measurements of CNTs in key environmental matrices (water, soil, sediment,
and biological tissues) are needed to address concerns about their
potential environmental and human health risks and to inform application
development. However, standard methods for CNT quantification are
not yet available. We systematically and critically review each component
of the current methods for CNT quantification including CNT extraction
approaches, potential biases, limits of detection, and potential for
standardization. This review reveals that many of the techniques with
the lowest detection limits require uncommon equipment or expertise,
and thus, they are not frequently accessible. Additionally, changes
to the CNTs (e.g., agglomeration) after environmental release and
matrix effects can cause biases for many of the techniques, and biasing
factors vary among the techniques. Five case studies are provided
to illustrate how to use this information to inform responses to real-world
scenarios such as monitoring potential CNT discharge into a river
or ecotoxicity testing by a testing laboratory. Overall, substantial
progress has been made in improving CNT quantification during the
past ten years, but additional work is needed for standardization,
development of extraction techniques from complex matrices, and multimethod
comparisons of standard samples to reveal the comparability of techniques