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- Selective oxidation of 4-nitrophenol with H2O2 in a biphasic system by janus-like carbon nanotubesPublication . Sanches, Flávia Kim; Roman, Fernanda; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Silva, Adrián; Faria, Joaquim; Machado, Bruno; Serp, Philippe; Marin, Pricila; Gomes, HelderThe use of petroleum-based products has increased drastically with the increase in population, resulting in the deposition of oily products in aquatic systems. It is estimated that for each ton of petroleum that undergoes refinement processes, between 0.5 and 1 ton of oily wastewaters are generated, bearing an oil concentration that may reach 40 g L-1 [1,2]. Hazardous pollutants dissolved both in oily and aqueous phases may also be found in those oily wastewaters [3], hindering their treatment through conventional processes. Furthermore, the oil phase is, in some cases, an added-value product, and its degradation results in economic losses. Thus, the development of processes that allow the removal of hazardous contaminants from oily and aqueous phases, providing an opportunity for recovering both phases, should be advantageous [3]. This work deals with the selective removal of a hazardous compound (4-nitrophenol, 4-NP) from a simulated oily wastewater (2,2,4-trimethylpentane:water = 10:90 v/v) by an oxidative process considering H2O2 as oxidant and amphiphilic Janus-like carbon nanotubes as catalysts. Amphiphilic catalysts were selected since they should present advantages in this process due to their ability to interact with both aqueous and oily compounds and phases [4]
- Remoção de metais pesados em lixiviados para uso como fertilizantesPublication . Cardoso, Jonathan; Fernández-Delgado, Marina; Vertonha, Maria Thais; Cabral, David; Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Arrobas, Margarida; Brito, Paulo; Gomes, HelderThe aim of this work is to offer a sequence of processes to convert leachate liquid stream with a highly variable composition, collected from the composting line of a mechanical and biological treatment facility, into commercial fertilizers, which fit the composition requirements of the European Legislation. The leachate was first characterized by total organic carbon (TOC), density, fixed and volatile solids, nutrients as organic and ammoniacal nitrogen, phosphorus, potassium, and heavy metals content, to verify the accordance with the European Legislation for fertilizers. The preliminary characterization showed that the leachate contains low levels of organic and ammoniacal nitrogen and phosphorus but high contents of potassium and TOC, which are interesting to fertilizing purposes, and chromium, which needs to be removed to fit the specifications. To chromium removal, some adsorbents materials were proposed: activated carbon produced from the compost of the referred company and acid activated clays obtained from a partnership with a Kazakhstan institution. The results after the adsorption process showed an interaction between the adsorbents and TOC, which was not intended, and a reduction in the heavy metals content, more efficient for Pb, Cd, Zn and Cu, but less for Cr removal. For future work, the study of the use of ionic resins was proposed through the development of an experimental design, in order to obtain the optimized parameters for the minimization of TOC loss, and promotion of heavy metals removal, especially chromium, using a response surface methodology.
- Polyolefin-derived carbon nanotubes as magnetic catalysts for wet peroxide oxidation of paracetamol in aqueous solutionsPublication . Díaz de Tuesta, Jose Luis; Silva, Adriano S.; Roman, Fernanda; Sanches, Lucas Fenato; Silva, Fernando Alves; Pereira, Ana I.; Silva, Adrián; Faria, Joaquim; Gomes, HelderThis work deals with developing feasible valorization technologies to prepare carbon nanotubes (CNTs) from plastic solid waste and demonstrate their application in catalytic wet peroxide oxidation (CWPO). CNTs were synthesized by catalytic chemical vapor deposition (CCVD) at 850 oC, considering low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) as carbon precursors representative of urban plastic solid waste. Iron oxide nanoparticles supported in alumina, previously synthesized by sol-gel, were used as catalysts in the CCVD process. TEM micrographs allow us to determine 41 nm as the average outer diameter of the CNTs and to visualize magnetic iron nanoparticles (ca. 10 nm) embedded inside the CNTs (ca. 6.4 % of content measured as ashes). These magnetic nanoparticles were kept in the CNT structure even after the puri-fication of the CNTs with sulphuric acid, allowing to obtain magnetic CNTs. All purified and non-purified CNTs prepared from the polyolefins were assessed as catalysts in CWPO of paracetamol (PCM), used as a model pharmaceutical contaminant in water at CPCM,0 = 100 mu g mL-1 (CH2O2,0 = 472 mu g mL-1, CCNT = 2.5 g L-1, pH0 = 3.5 and T = 80 degrees C). The concentrations of PCM, H2O2, aromatic and total phenolic compounds were monitored for 24 h. All CNTs showed catalytic activity, allowing the complete degradation of PCM at 6 h of reaction time. The stability and reusability of materials are tested and proved in CWPO.
- Treatment of wastewater containing pharmaceutical compounds by catalytic wet peroxide oxidation using clay-based materials as catalystsPublication . Silva, Adriano S.; Gomes, Helder; Sgorlon, Juliana; Díaz de Tuesta, Jose LuisThis work deals with the treatment of wastewater containing paracetamol, used as a model pharmaceutical emergent pollutant, by catalytic wet peroxide oxidation using clay-based materials as catalysts. The catalysts prepared in this work were clays activated through acid treatment and clays pillared with Co and Fe. For the preparation, natural clays from four different regions of Kazakhstan were used: Akzhar, Asa, Karatau and Kokshetau. The FTIR analysis showed that the pillared clays have a higher amount of iron in its structure when compared with the natural materials, suggesting that the intercalation of iron was successful. The N2 adsorption isotherms obtained were classified as Type II, typical of macroporous materials. The acid characterization showed that the procedures used for the preparation of the acid activated clays and of the pillared clays caused structural modifications. After the preparation and characterization, the pillared materials were tested in the degradation of paracetamol by catalytic wet peroxide oxidation (CWPO). Paracetamol concentration, hydrogen peroxide concentration and total organic carbon analysis (TOC) were followed against time. The material with the best activity was the Kokshetau pillared clay (KOP), with a complete conversion of the pollutant being obtained between 240 and 360 minutes of reaction, followed by a negligible iron leaching of 0.011 %. This leaching left the reaction system with a concentration of 0.089 mg/L of Fe, which is lower than the limit established by the European legislation for discharge in natural water courses (2 mg/L). Since the Kokshetau pillared clay presented the best result, other Kokshetau-based samples (activated, calcined and natural) were also tested in the CWPO of paracetamol. The higher efficiency of KOP in the CWPO of paracetamol can be explained by the fact that this material has a higher acidity, basicity and surface area when compared to the other pillared samples.
- Heavy metals removal on leachate for use as fertilizersPublication . Cardoso, Jonathan; Vertonha, Maria Thais; Cabral, David; Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Arrobas, Margarida; Brito, Paulo; Gomes, HelderMunicipal landfill leachates typically contain high ammonium and organic concentration which could contribute to its use in agriculture, leading to the reduction of costs for the respective waste treatment plants. However, due to the nature of the leachates, they may contain phytotoxic substances. The landfillleachate samples differ by many factors such as the composition of the treated waste, elapsed time, geochemical and weather conditions [1-3]. Taking into account these considerations, leachate samples from a storage tank at the "Residuos do Nordeste, ElM" mechanical and biological treatment plant, were collected in February 2019, and stored :at 4°C. The leachate samples were processed using activated carbon adsorbents produced from the compost of the referred company, and H2S04 activated clays obtained from a partnership with a Kazakhsta1n institution. The leachate samples were mixed with the adsorbents for 48 hours, centrifugated and the supernatant was reserved. TOC analysis in a Shimadzu TOC-L equipment and metals quantification by atomic absorption spectroscopy using a Varian SpectrAA 220 apparatus were carried out. :Selected results are presented in Fig. 1. The original leachate presents an organic carbon content closer to the requirements of the EU legislation for liquid organo-mineral fertilizers. The activated carbon promoted greater TOC removal in comparison with the activated clays. Both materials showed interaction with the heavy metals. However, Cr still remains present in higher conten1ts and K presents lower values than the legislation requirements. Overall, the activated carbons presented a greater potential for heavy metals removal. However, ion-exchange resins will be tested for a more efficient heavy metals removal to minimize possible secondary elimination of components sue:h as nutrients and organic carbon.
- Technologies to upcycle plastic solid wastes into nanostructured carbon materials and their application in the removal of micropollutantsPublication . Díaz de Tuesta, Jose Luis; Roman, Fernanda; Silva, Adriano S.; Ribeiro, Rui; Vieira, Octávia; Silva, Adrián; Faria, Joaquim; Gomes, HelderThe world’s plastics production has been increasing stiffly over the years. Accounting only 2019, the global production of plastics reached nearly 370 million metric tonnes, with ca. 15.7% of those produced in Europe.1 Recent projections point towards a cumulative generation of plastic solid wastes (PSWs) of over 25,000 million metric tonnes by 2050.2 Among these, 36.4% are expected to be discarded in landfills or in the environment; a similar fraction (36.4%) should be incinerated, and only 27.2% will be recycled.2 These forecasts point out that PSWs are mismanaged, mainly because current technologies are unable to promote proper reusing/recycling of these materials.3 Proper waste management falls within the scope of upstream responses. However, several difficulties have been hindering waste plastic recycling, such as the lack of economic attractiveness of the resulting products.4 Using waste plastics as feedstock for the production of added-value products and materials has been proposed as the boost needed to increase the attractiveness of plastics recycling. Among them are the preparation of carbon nanomaterials (CNs), such as carbon nanotubes or graphene, using PSWs as carbon precursors. This represents a new strategy for the valorisation of PSWs, consisting in the cracking of polymers that compose them and further synthesizing the CNs, using the resultant degradation gaseous products, by catalytic chemical vapour deposition (CCVD). However, most studies only report single pure polymers as model PSW to carry out a one-step process (pyrolysis and synthesis) without targeting applications of the resulting CNs.5-7 The properties of the CNs obtained from PSWs could be fined tuned for specific applications, as demonstrated in a previous work.8 These characteristics of the developed fine tuned CNs make them highly suitable for the removal of micropollutants, as will be shown in this talk.
- Wet peroxide oxidation of paracetamol using acid activated and Fe/Co-pillared clay catalysts prepared from natural claysPublication . Silva, Adriano S.; Kalmakhanova, Marzhan; Massalimova, Bakytgul Kabykenovna; Sgorlon, Juliana; Díaz de Tuesta, Jose Luis; Gomes, HelderMany pharmaceuticals have been recently identified at trace levels worldwide in the aquatic environment. Among them, the highly consumed paracetamol (PCM), an analgesic and antipyretic drug, is largely being accumulated in the aquatic environment due to ine cient removal by conventional sewage treatment plants. This work deals with the treatment of PCM, used as a model pharmaceutical contaminant of emerging concern, by catalytic wet peroxide oxidation using clay-based materials as catalysts. The catalysts were prepared from natural clays, extracted from four di erent deposits using acid-activated treatment, calcination, and pillarization with Fe and Co. Pillared clays show the highest catalytic activity owing to the presence of metals, allowing to remove completely the PCM after 6 h under the following operating conditions: CPCM = 100 mg L1, CH2O2 = 472 mg L1, Ccat = 2.5 g L1, initial pH = 3.5 and T = 80 C. The prepared materials presented high stability since leached iron was measured at the end of reaction and found to be lower than 0.1 mg L1.
- Wet peroxide oxidation of paracetamol using natural clay-based materials as catalystsPublication . Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Sgorlon, Juliana; Kalmakhanova, Marzhan; Gomes, HelderIn recent years, many pharmaceutical compounds have been identified worldwide at trace levels (in the order from ng·L·1 to mg·L-1) in the aquatic 12nvironment [1]. The presence of pharmaceutical contaminants in water, even at low concentrations, could bring harmful toxicological consequences to human beings and animals that ingested the contaminated water [2]. This work deals with the treatment of water containing paracetamol (PCM) by catalytic wet peroxide oxidation (CWPO) using clay-based materials as catalysts. PCM was considered as a model pharmaceutical emergent pollutant. For the preparation of the catalysts, natural clays from four different regions of Kazakhstan were used Akzhar, Asa, Karatau, and Kokshetau. From the clay obtained in kokshetau deposit, three catalysts were prepared: 1) natural one (KON), 2) calcined clay at 600 °C for 5 h (KOC), and 3) a pillarized clay (KOP) with a pillaring solution containing 0.25 M CoCI2, 0.5 M FeCI3 and 0.5 M NaOH, resulting in OH/(Fe+Co) = 2:1. Additionally, three clays were ptrepared by the same procedure of pillarization from the Akzhar, Asa and Karatau natural clays, resulting in AKP, ASP, and KAP, respectively. The concentration of PCM, H20 2 and total organic carbon (TOC) were followed during the CWPO experiments (Fig. 1 ). All materials revealed high catalytic activity, the non-pillared samples allowing to remove more than 33.4% of PCM after 24 h of reaction time under the following operating conditions: 80 °C, initial pH 3.5, Ccatalyst = 2.5 g L-1, CPCM = 100 mg L-1 and CH202 = 472 mg L-1. The CWPO runs done with the pill a red clay catalysts resulted in more than 90% of removal of the pollutant after 24 h of reaction. The best catalyst was KOP since it leads to the complete removal of the pollutant after 8 h of reaction time and to the highest abatement of TOC (>60%) under the same operational conditions.
- Magnetic carbon nanotubes obtained from plastic as catalysts for wet peroxide oxidation of paracetamolPublication . Sanches, Lucas Fenato; Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Silva, Fernando Alves; Silva, Adrián; Gomes, HelderMagnetic carbon nanotubes (MCNTs) were prepared by catalytic chemical vapour deposition (CCVD) and tested as catalysts for catalytic wet peroxide oxidation (CWPO) of paracetamol (PCM). For the synthesis of the MCNTs, low-density polypropylene (LDPE) and high-density polypropylene (HDPE) were used as model carbon precursors present in urban plastic solid waste (Aboul-Enein, 2018). The catalyst employed in CCVD was magnetite supported on alumina prepared by a sol-gel process. The CWPO runs were conducted with the stoichiometric concentration of H2O2 needed for the full mineralization of 100 ppm of PCM, at 80 °C and initial pH 3.5, following experimental methods described elsewhere (Silva, 2019). The catalyst prepared from LDPE, LDPE_MCNTW, was able to completely degrade the pollutant within 6 h of reaction, while HDPE_MCNTW took 8 h to achieve the same removal. Iron measurement in the final reaction solutions showed the absence of possible additional pollution coming from iron leaching of the catalysts.
- Wastewater purification using advanced functionalized nanoparticlesPublication . Noorimotlagh, Zahra; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Mirzaee, Seyyed Abbas; Martínez, Susana Silva; Gomes, HelderEnvironmental pollution is rapidly increasing due to population growth, industrialization, urbanization, etc. Anthropogenic activities have increased pollution in all sections of the environment (i.e., soil, air, water, and wastewater). There is great importance attached to resolving this complicated situation, which could effectively reduce the negative impacts of anthropogenic activities on the environment. Nanotechnology, especially functionalized nanoparticles (FNPs), is emerging as an effective solution to environmental pollution at the global scale. The extraordinary chemical and physical properties of materials at the nanometer scale enable new and innovative applications in the environmental sector. Although manufactured metal-based NPs are being produced, concern about their toxicity is increasing. To resolve the toxicity of NPs, functionalization of the materials appears to be a possible solution. The functionalization of NPs, as well as the metal core, can be varied according to the problem being targeted. This chapter discusses detailed information about the fabrication methods of FNPs used for environmental purification, especially wastewater treatment. Their scope in the environment, which includes cleaning up existing pollution, is also discussed. A critical evaluation of the challenges and future needs for a safe environment are also explored.