9,954 research outputs found
nZVI particles production for the remediation of soil and water polluted by inorganic Lead
The present study deals with experiments of Pb removal by
nano-Zero Valent Iron (nZVI) in aqueous solution and in
soil. Synthetic Pb aqueous solutions were treated by nZVI,
at a fixed Pb concentration of 100 mg L-1
, varying
nanoparticles initial concentration in the range between 27
and 270 mg nZVI L-1
. A kinetic study was carried out: Pb
adsorption followed a first order kinetic, and half life times
between 11 and 26.66 min were determined. Soil samples
were first characterized, and Pb speciation and
concentration by sequential extractions was determined.
Adsorption tests were then carried out at three selected
amounts of nZVI, to allow Pb stabilization in the soil
matrix. To evaluate the treatment efficiency, sequential
extractions were also performed on the treated samples
Hexavalent chromium reduction in manganese-rich soils by ZVI nanoparticles: the influence of natural organic matter and manganese oxides
Hexavalent chromium reduction by nano Zero-Valent Iron
(nZVI) has been proved fast and efficient, mainly due to
nanoparticles large specific surface area and high chemical
reactivity. In this work the influence of natural organic
matter and manganese oxide was investigated, through a
set of experimental tests carried out on a real polluted soils
naturally rich in manganese. Soil samples were
characterized in terms of initial concentration of Cr,
Cr(VI), Mn, pH, and TOC and three different nZVI
solutions were used (120, 360 and 600 mg nZVI L-1
) for
the treatment. At selected interval times (0, 5, 10, 15, 30,
60, 120 min) a slurry sample was filtered and Cr(VI)
residual concentration and pH were measured. The same
procedure was carried out on an artificial spiked soil,
characterized by a similar TOC and poor of Mn.
Furthermore the two soils were mixed with different
amounts of leonardite, to evaluate the influence of NOM
on treatment efficiency
Continuous production of KNO3 nanosalts for the fertilization of soil by means of a Spinning Disk Reactor
In this study the production of high soluble material
nanoparticles was successfully performed by means of a
spinning disk reactor (SDR). This result was possible due
to the use of a potassium nitrate saturated solution, which
was continuously recycled back to the reactor after
removal of the produced solid nanoparticles.
Several process configurations were checked. It appears to
be mandatory that the recycled saturated solution must be
free of residual nanoparticles since their presence would
lead to heterogeneous nucleation. In this respect, a small
amount of nitric acid was added to the stream to permit the
residual nanoparticle dissolution. Moreover, a spiral
wounded piping system was developed in order to increase
both the contact time and the mixing condition of the
saturated solution with the added acid before entering the
SD
About the limits of microfiltration for the purification of wastewaters
In the past, microfiltration was widely used as a
pretreatment step for wastewater stream purification
purposes. Experiences performed during the last years
shows that microfiltration fails to maintain its
performances for longer period of times. Many case studies
demonstrate that the adoption of microfiltration leads to
the failure of the overall process; the severe fouling of the
microfiltration membranes leads to high operating costs
with the consequence to make the treatment of the
wastewater economically unfeasible. The boundary flux
concept is a profitable tool to analyze fouling issues in
membrane processes. The boundary flux value separates an
operating region characterized by reversible fouling
formation from irreversible one. Boundary flux values are
not content, but function of time, as calculated by the subboundary
fouling rate value. The knowledge of both
parameters may fully describe the membrane performances
in sub-boundary operating regimes. Many times, for
wastewater purification purposes, ultrafiltration
membranes appear to be suits better to the needs, even they
exhibit lower permeate fluxes compared to microfiltration.
Key to this choice is that ultrafiltration appears to resist
better to fouling issues, with a limited reduction of the
performances as a function of time. In other words, it
appears that ultrafiltration exhibit higher boundary flux
values and lower sub-boundary fouling rates. In this work,
after a brief introduction to the boundary flux concept, for
many different wastewater streams (more than 20,
produced by the most relevant industries in food,
agriculture, manufacture, pharmaceutics), the boundary
flux and sub-boundary fouling rate values of different
microfiltration and ultrafiltration membranes will be
discussed and compared. The possibility to successfully
use microfiltration as a pretreatment step strongly depends
on the feedstock characteristics and, in detail, on the
particle size of the suspended matter. In most cases,
microfiltration demonstrates to be technically unsuitable
for pretreatment purposes of many wastewater streams; as
a consequence, the adoption of microfiltration pushes
operators to exceed boundary flux conditions, therefore
triggering severe fouling, that leads to economic
unfeasibility of the process in long terms
Chromium recovery by membranes for process reuse in the tannery industry
Leather tanning is a wide common industry all over the
world. In leather processing, water is one of the most
important medium, almost 40-45 L water kg-1 raw-hide or
skin is used by tanneries for processing finished leathers.
The composition of tannery wastewater presents
considerable dissimilarities in the concentration range of
pollutants both of inorganic (chlorides, with concentration
ranging from several hundred to over 10,000 mg L-1 Cl–;
sulphate (VI), ammonium ions and sulphide ions,
exhibiting concentration that ranges from tens to several
hundred mg L-1) and organic (the COD value is usually
several thousand mg L-1 O2). Throughout the years, many
conventional processes have been carried out to treat
wastewater from tannery industry: unfortunately, in this
case, biological treatment methods give rise to an
excessive production of sludge, whereas physical and
chemical methods are too expensive in terms of energy and
reagent costs. In this work, a membrane process based on
NF membrane modules was adopted to treat the tannery
feedstock after primary conventional treatment. In a first
step, the determination of all boundary flux parameters, in
order to inhibit severe fouling formation during operation,
were performed. After this, experimental work was carried
out to validate the approach. The target of water
purification was reached, that is the legal discharge to
municipal sewer system in Italy of 90% of the initial
wastewater stream volume. This allows having an
immediate cost saving of 21%. Moreover, the developed
process leads to a second benefit, that is the production of
5% of the initial volume as a highly chromium-rich
concentrate at no cost suitable to tannery process recycle
and reuse. In this case, cost saving rates exceeds 40%. At
the end, scale-up of the investigated process will be
discussed from technical and economic point of view
An Innovative and Easy Method for Iron-Doped Titania Synthesis
In this work, photocatalytically active titanium oxide nanoparticles were synthesized for the treatment of contaminated water under visible light. Various Ag, Sr and Fe-based synthesis and doping techniques (mainly hydrothermal and sol-gel methods) were performed. Adsorptive and photocatalytic properties were studied by testing in batch mode for the decontaminating a synthetic methylene blue solution (used as a model contaminant) using a simple 13 W LED bulb as the light source. The best material in terms of both activity (high removal kinetics) and simplicity of synthesis was found to be titanium oxide doped with Fe via "solid-state"method. This method enabled the synthesis of titania nanoparticles about 70 nanometers in size with Fe3+ effectively substituting titanium atoms (Ti4+) in the crystalline bulk of titania. The pseudo-first-order kinetic model was found to represent the behavior of the experimental data
Soil Biocementation via Enzyme Induced Carbonate Precipitation (EICP) Method Employing Soybeans as a Source of Cheap Enzyme
In this work, the soil improvement technique via Enzyme Induced Carbonate Precipitation (EICP) was investigated by employing, as an alternative to expensive pure enzymes, enzymes extracted from agro-food wastes (tomato, apple, and soybean) such that the process is economically viable and fully embraces the concept of the circular economy. The feasibility of the process was evaluated by monitoring calcium carbonate precipitation in a sand sample. The effect of selected operative parameters was investigated during the injection into different grain size sand samples. The optimal operating conditions in terms of sand grain size, temperature, Urea/Calcium concentration were found. Results demonstrated the effectiveness of this alternative solution for EICP method in term of acquired material strength and the possibility to operate sand consolidation through an economically sustainable process
Focusing properties of linear undulators
This paper investigates the focusing properties of linear magnetic undulators, i.e., devices characterized by weak defocusing properties in the horizontal (wiggling) plane and strongly focusing in the vertical plane. The problem of identifying the conditions that ensure the existence of the electron beam eigenstates in the undulator lattice for a given working point of electron beam energy E_{b} and resonant wavelength λ_{r} is studied. For any given undulator lattice, a bandlike structure is identified defining regions in the (E_{b},λ_{r}) plane where no periodic matching condition can be found, i.e., it is not possible to transport the electron beam so that optical functions are periodic at lattice boundaries. Some specific cases are discussed for the SPARC FEL undulator
Analytical Model of Connected Bi-Omega: Robust Particle for the Selective Power Transmission Through Sub-Wavelength Apertures
Cataloged from PDF version of article.In this paper, we present a new analytical model of
the connected bi-omega structure consisting of two bi-omega particles
connected together through their arms. A single bi-omega
particle consists of a pair of regular equal omegas with mirror
symmetry. Assuming the individual bi-omega particle electrically
small, the equivalent circuit is derived, in order to predict its
resonant frequency. Then, two bi-omega particles are connected
together, obtaining a symmetric structure that supports two
fundamental modes, with even and odd symmetries, respectively.
The proposed analytical model, then, is used to develop a procedure
allowing the design of the particle for a desired resonant
frequency. The effectiveness of the proposed analytical model and
design guidelines is confirmed by proper comparisons to full-wave
numerical and experimental results. We also demonstrate through
a proper set of experiments that the resonant frequencies of the
connected bi-omega particle depend only on the geometrical and
electrical parameters of the omegas and are rather insensitive to
the practical scenario where the particle itself is actually used, e.g.
in free-space, rectangular waveguide or across an aperture in a
metallic screen
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