Browsing by Author "Marques, Vitor da Costa"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Performance and modeling of Ni(II) adsorption from low concentrated wastewater on carbon microspheres prepared from tangerine peels by FeCl3-assisted hydrothermal carbonizationPublication . Díaz de Tuesta, Jose Luis; Roman, Fernanda; Marques, Vitor da Costa; Silva, Adriano S.; Silva, Ana P. F.; Bosco, Tatiane; Shinibekova, Assem A.; Aknur, Sadenova; Kalmakhanova, Marzhan; Massalimova, Bakytgul Kabykenovna; Arrobas, Margarida; Silva, Adrián; Gomes, HelderThe presence of heavy metals in the environment as a consequence of human activity is an issue that has caught the attention of researchers to find wastewater treatment solutions, such as adsorption. In this work, hydrochars and activated carbon microspheres are prepared from tangerine peels as carbon precursor and FeCl3 as activating and structure-directing agent in the hydrothermal carbonization, allowing to obtain hydrochar microspheres ranging from 50 to 3615 nm. In addition, a pyrochar was prepared by pyrolysis of the same precursor. The activated carbon shows the highest surface area (SBET up to 287 m2 g–1), but the basicity of the pyrochar (1.83 mmol g-1, SBET = 104 m2 g–1) was determinant in the adsorption of Ni, being considered the carbon-based material with the highest uptake capacity of Ni. Isotherm and kinetic adsorption of Ni on the most representative activated carbon microsphere, pyrochar and hydrochar microsphere are assessed by 10 and 7 models, respectively.
- Valorization of tangerine peels in the preparation of adsorbents for removal of Ni(II) from aqueous solutionsPublication . Marques, Vitor da Costa; Gomes, Helder; Díaz de Tuesta, Jose Luis; Dal Bosco, Tatiane CristinaThe discharge of industrial and domestic wastewater is one of the main causes of contamination of water bodies by heavy metals. Among these heavy metals, nickel (Ni) is one of the most used in industrial processes, such as the production of alloys, stainless steel and automotive batteries, as well as electroplating activities, causing high concentrations in the effluents of these industries. Several techniques, such as chemical precipitation and filtration, have been studied in order to promote the removal of these heavy metals from wastewater. However, these techniques are often financially and technically costly. Under this context, adsorption using activated carbons (ACs) appears as an alternative, which is characterized by being an effective and economically viable technique. Citrus fruits, such as tangerine, are of great importance in the Portuguese economic context. In 2017, just over 374.4 thousand tons were produced, with 10% of this volume corresponding to tangerine. This research aimed, therefore, to produce ACs from tangerine peels and use them in the adsorption of nickel from aqueous medium. The ACs were produced in two stages: activation and carbonization. Upon activation, the hydrothermal carbonization process (HTC) was used considering FeCl3 as activating agent under three concentrations (0.5, 1.0 and 2.5 M). Afterwards, the prepared materials were carbonized in a tubular oven at 800 ºC for 4 h. The samples were named as follows: TW-C (pyrolyzed peels without HTC), TW-Fe-0.5-C / TW-Fe-1.0-C / TW-Fe-2.5-C (HTC and pyrolyzed peels) and TW-Fe-2.5 (peels with HTC without pyrolysis). The physico-chemical properties of the ACs, such as elemental analysis, ash content, acidity and basicity, were determined to correlate with their performance. The kinetic and isotherm adsorption of Ni(II) onto the ACs was assessed at the following operating conditions: 2.5 g L-1 of AC, 25 ºC and pH 6 and modelled by the kinetic models of pseudo-first order, pseudo-second order and Elovich, as well as the adsorption isotherms of Langmuir, Freundlich and the General Isotherm Equation (GIE) of Tóth. The materials TW-C showed the best adsorption results and removed 99% of Ni(II) at pH 9. The kinetic models that best described the adsorption process were pseudo-second order (TW-Fe-2.5-C) and Elovich (TW-C). The GIE of Tóth showed the best fit, however, its parameters did not show statistical significance at the 5% confidence level, being rejected. The Freundlich model was able to represent the experimental data with certain precision (R² reached 0.9557 and 0.9785 for TW-C and TW-Fe-2.5-C, respectively) and statistical significance according to the t-test and F-test.