Navegando por Autor "Jegatheesan, Veeriah"

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    Management of waste printed circuit boards via supercritical water technology
    (2022) Souza, Guilherme Botelho Meireles de; Pereira, Mariana Bisinotto; Santos, Lucas Francisco dos; Alonso, Christian Gonçalves; Jegatheesan, Veeriah; Cardozo Filho, Lúcio
    In this study, the application of the supercritical water technology on the management of waste printed circuit boards (PCBs) obtained from small information technology (IT) and communication equipment was conducted. Initially, an extensive recycling-oriented characterization of waste printed circuit boards was conducted through a combination of several physicochemical analyzes such as MP-AES, XRF, TG/DTA, CHNS elemental analysis, SEM and XRD. Afterwards, at supercritical conditions of water (Tc > 374.29 °C and Pc > 22.089 MPa), the optimal conditions for the degradation of the organic polymers present in the waste PCBs were defined by a response surface methodology. A complete organic degradation rate (ODR) was achieved at 600 °C, reaction time of 60 min, waste PCBs load of 15 g and flow-rate of 5 mL min−1. After the removal of the organic polymers, the metals were liberated, and the metal recovery efficiency (MRE) reached values higher than 90% at all evaluated conditions. Then, initial insights on the subsequent treatment of the liquid decomposition by-products generated during the supercritical water (ScW) processing of waste PCBs were provided. A total organic carbon reduction of 99.88% was achieved via the ScW oxidation process using the same experimental apparatus. The treated solution was successfully re-used in the ScW processing of waste PCBs instead of clean water. Moreover, hydrogen, methane, CO2, and CO were identified as the major gaseous products associated to the supercritical water treatment of waste PCBs. Finally, a novel strategy to enhance the production of combustible gases, through the addition of ethanol and glycerol, and increase the economic feasibility of the supercritical water processing of waste PCBs was proposed.
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    Supercritical water technology: an emerging treatment process for contaminated wastewaters and sludge
    (2022) Souza, Guilherme Botelho Meireles de; Pereira, Mariana Bisinotto; Mourão, Lucas Clementino; Santos, Mirian Paula dos; Oliveira, José Augusto de; Aldaya Garde, Ivan Aritz; Alonso, Christian Gonçalves; Jegatheesan, Veeriah; Cardozo Filho, Lúcio
    The destruction of toxic, persistent, refractory, and hazardous organic compounds, often present at high concentrations in both industrial and municipal wastewaters, remains a major challenge to be overcome, mainly due to the inefficiencies of conventional processes. Notwithstanding, the search for novel treatment methods has received great attention recently. Supercritical water technology has proved to be a very promising treatment method for contaminated wastewaters and sludges. Performances of supercritical water technology in treating wastewaters from a wide variety of industries including pulp and paper, pharmaceutical, textile, pesticides, dairy, petrochemical, explosives, and distillery were reviewed. Furthermore, the effects of main operating conditions, namely temperature, pressure, residence time on the treatment efficiency, usually reported in terms of total organic carbon and chemical oxygen demand removal were summarized. In addition, well-known technical challenges faced by supercritical water processes such as corrosion, salt deposition, clogging, elevated running costs and possible solutions to mitigate those challenges have been discussed. At last, the future scope of the supercritical water technology is expected to be driven by policies aiming at the reduction of greenhouse gas emissions, environmental protection, mitigation of climate changes and the production of commercial gases from highly efficient treatment of contaminated organic wastewaters and sludges.
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    Valorization of e-waste via supercritical water technology: an approach for obsolete mobile phones
    (2023) Souza, Guilherme Botelho Meireles de; Pereira, Mariana Bisinotto; Mourão, Lucas Clementino; Alonso, Christian Gonçalves; Jegatheesan, Veeriah; Cardozo Filho, Lúcio
    The improper handling of electronic waste has not only severe environmental impacts but also results in the loss of high economic potential. To address this issue, the use of supercritical water (ScW) technology for the eco-friendly processing of waste printed circuit boards (WPCBs) obtained from obsolete mobile phones has been explored in this study. The WPCBs were characterized via MP-AES, WDXRF, TG/DTA, CHNS elemental analysis, SEM and XRD. A L9 Taguchi orthogonal array design was employed to evaluate the impact of four independent variables on the organic degradation rate (ODR) of the system. After optimization, an ODR of 98.4% was achieved at a temperature of 600 °C, a reaction time of 50 min, a flowrate of 7 mL min−1, and the absence of an oxidizing agent. The removal of the organic content from the WPCBs resulted in an increase in the metal concentration, with up to 92.6% of the metal content being efficiently recovered. During the ScW process, the decomposition by-products were continuously removed from the reactor system through the liquid or gaseous outputs. The liquid fraction, which was composed of phenol derivatives, was treated using the same experimental apparatus, achieving a total organic carbon reduction of 99.2% at 600 °C using H2O2 as the oxidizing agent. The gaseous fraction was found to contain hydrogen, methane, CO2, and CO as the major components. Finally, the addition of co-solvents, namely ethanol and glycerol, enhanced the production of combustible gases during the ScW processing of WPCBs.