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Carbon-Nanotube-Based Superhydrophobic Magnetic Nanomaterial as Absorbent for Rapid and Efficient Oil/Water Separation
Publication . Kudaibergenova, Rabiga M.; Roman, Fernanda; Silva, Adriano S.; Sugurbekova, Gulnar K.
In this work, the simple fabrication of a new superhydrophobic magnetic sponge based
on CNTs, NiFe2O4 nanoparticles, and PDMS was investigated. CNTs were synthesized by chemical
vapor deposition (CVD) on a nickel ferrite catalyst supported on aluminum oxide (NiFe2O4/Al2O3).
The synthesis of nickel ferrite (NiFe) was accomplished using the sol–gel method, yielding magnetic
nanoparticles (43 Am2kg−1, coercivity of 93 Oe, 21–29 nm). A new superhydrophobic magnetic
PU/CNT/NiFe2O4/PDMS sponge was fabricated using a polyurethane (PU) sponge, CNTs, NiFe2O4
nanoparticles, and polydimethylsiloxane (PDMS) through the immersion coating method. The
new PU/CNT/NiFe2O4/PDMS sponge exhibits excellent superhydrophobic/oleophilic/mechanical
properties and water repellency (water absorption rate of 0.4%) while having good absorption of
oil, olive oil, and organic liquids of different densities (absorption capacity of 21.38 to 44.83 g/g),
excellent separation efficiency (up to 99.81%), the ability to be reused for removing oil and organic
solvents for more than 10 cycles, and easy control and separation from water using a magnet.
The new PU/CNT/NiFe2O4/PDMS sponge is a promising candidate as a reusable sorbent for
collecting oil and organic pollutants and can also be used as a hydrophobic filter due to its excellent
mechanical properties.
Beyond batch experiments: unveiling the potential of bimetallic carbon xerogels for catalytic wet peroxide oxidation of hospital wastewater in continuous mode
Publication . Silva, Adriano S.; Roman, Fernanda; Ribeiro, Rui; Garcia, Juan; Gomes, Helder
Single- and bimetallic carbon xerogels were prepared by incorporating iron and iron-cobalt precursors during their synthesis,
respectively, and tested in the catalytic wet peroxide oxidation (CWPO) of ibuprofen spiked into a simulated matrix in
batch mode. The bimetallic catalyst outperformed single and non-metallic catalyst by 25 and 85% after 360 min of reaction,
at mild temperature (30 °C). The best-performing catalyst was further used to treat hospital wastewater in a CWPO system
operating in full continuous mode. Process optimization was carried out considering different catalyst loads, temperatures,
and pH. The results obtained showed that the best conditions are initial pH 3, T = 80 °C, and a catalyst load of 35.4 mg cm−
3.
Having maintained values of chemical oxygen demand (COD) removals as high as 80% after 24 h of continuous operation,
the results herein reported revealed the high potential of the bimetallic carbon xerogel for CWPO of hospital wastewater
beyond conventional applications in batch mode. Despite some catalytic deactivation, the bimetallic carbon xerogel still
delivered a mineralization degree as high as 55% of the initial total organic carbon (TOC) content of the hospital wastewater
in the third 24-h cycle of CWPO in continuous mode of operation with successive catalyst reuse, as opposed to a 73% TOC
removal in the first cycle. Therefore, our results open prospects for the implementation of CWPO for hospital wastewater
treatment in continuous mode of operation.
3D printed photopolymer derived carbon catalysts for enhanced wet peroxide oxidation
Publication . Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Henrique, Adriano; Roman, Fernanda; Omralinov, Daria; Steldinger, Hendryk; Gläsel, Jan; Etzold, Bastian J.M.; Silva, José A.C.; Silva, Adrián; Pereira, Ana I.; Gomes, Helder
In this paper, we explore the application of powdered carbon and 3D-printed carbon monoliths prepared by
carbonization of a tailored photopolymer. We demonstrate the efficiency of the developed carbonaceous samples
in removing paracetamol (PCM) and sulfamethoxazole (SMX), used as model contaminants. Our results
demonstrate that carbon samples are active in CWPO, and their catalytic activity is significantly improved by
applying nitric acid and urea functionalization methods. The characterization results showed the pure carbon
nature of the material (no ashes), their unique structure defects proven by Raman (D/G > 1.8), textural properties
(SBET = 291–884 m2/g) and their surface chemistry, which was addressed by pHPZC (2.5–7.5), acidity
(312–2375 μ mol gcat 1) and basicity (117–653 μ mol gcat 1) determination and XPS of highlighted materials (N1s =
0–3.51 at.%, O1s = 7.1–15.3 at.%). Using desorption assays, our study reveals the adsorption role for pollutant
degradation by CWPO using carbon monolithic samples. At last, we demonstrated the ability of functionalized
3D-printed carbon monoliths to keep degradation of PCM and total organic carbon (TOC) above 85 % and 80 %,
respectively, during 48 h in a continuous flow CWPO system. Sulfamethoxazole degradation in continuous
system was also studied to validate the catalyst versatility, achieving 81 % and 79 % pollutant degradation and
TOC abatement, respectively, during 48 h on stream. The characterization of the recovered catalyst provides
further insights into the absence of structural modifications after the reaction, reinforcing the stability and
reusability characteristic of the 3D-printed carbon catalyst.
Time-Dependency of Guided Local Search to Solve the Capacitated Vehicle Routing Problem with Time Windows
Publication . Silva, Adriano S.; Lima, José; Silva, Adrián; Gomes, Helder; Pereira, Ana I.
Research have been driven by the increased demand for
delivery and pick-up services to develop new formulations and algorithms
for solving Vehicle Routing Problems (VRP). The main objective
is to create algorithms that can identify paths considering execution time
in real-world scenarios. This study focused on using the Guided Local
Search (GLS) metaheuristic available in OR-Tools to solve the Capacitated
Vehicle Routing Problem with Time Windows using the Solomons
instances. The execution time was used as a stop criterion, with short
runs ranging from 1 to 10 s and a long run of 360 s for comparison. The
results showed that the GLS metaheuristic from OR-Tools is applicable
for achieving high performance in finding the shortest path and optimizing
routes within constrained execution times. It outperformed the
best-known solutions from the literature in longer execution times and
even provided a close-to-optimal solution within 10 s. These findings suggest
the potential application of this tool for dynamic VRP scenarios that
require faster algorithms.
Unveiling Key Parameters: Time Windows and Travel Times in Capacitated Waste Collection
Publication . Silva, Adriano S.; Lima, José; Silva, Adrián; Gomes, Helder; Pereira, Ana I.
Numerous studies in waste management propose solutions
to the Waste Collection Problem, often focusing on constraints such as
time windows and truck capacity. Travel times between points play a vital
role in optimizing waste collection. However, the methods for determin- AQ1
ing them are frequently omitted. Another parameter that has a great
influence on waste collection is the time window. Here, the impact of
time windows and travel times on the capacitated waste collection problem
with time windows solution was assessed for collecting three waste
types. Surprisingly, travel times were found to have minimal influence on
route optimization, while time windows significantly affected the algorithm’s
ability to identify the most efficient collection route. Addressing AQ2
these considerations is crucial for practical application and improving
the performance of waste collection algorithms in real-world contexts.
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Fundação para a Ciência e a Tecnologia
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SFRH/BD/151346/2021