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Regeneração de carvões ativados saturados com compostos farmacêuticos
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A crescente relevância dos processos de adsorção em carvões ativados, nomeadamente para controlo de
fármacos (PhAC) no tratamento de águas, requer a avaliação da sua regeneração para aumentar a
sustentabilidade e diminuir os custos associados.
Neste trabalho estudou-se a adsorção de dois PhAC (cafeina e paracetamol) em carvões ativados
granulares (GAC) - cGAC (comercial) e GAC/PNS (preparado em laboratório a partir de casca de
pinhão). Nos sistemas GAC/PhAC, avaliaram-se os perfis cinéticos, capacidade de adsorção e eficiência
de regeneração, estudando o efeito do tamanho da partícula (425-300 ou 850-600 μm) e agente de
regeneração térmica (N2 ou Steam).
Os ensaios cinéticos revelaram maior celeridade para a cafeína, mas o equilíbrio é sempre atingido às
24h, seguindo uma cinética de pseudo-segunda ordem. Os resultados de equilíbrio ajustam-se ao modelo
de Langmuir, revelando uma capacidade de adsorção superior para o GAC/PNS comparativamente ao
cGAC (cafeína: 400 versus 250 mg/g; paracetamol: 394 versus 200 mg/g).
Os ensaios de saturação/regeneração/reutilização revelaram influência de vários fatores na eficiência de
regeneração (RE). As partículas de GAC 850-600 μm permitem RE superiores (cafeína: 95,6-91,6%;
paracetamol: 78,8-61,8%). A regeneração térmica em N2 versus Steam, potencia melhores RE (cafeina:
98,5-81,9% versus 154,0-53,6%; paracetamol: 78,8-33,5% versus 60,0-25,6%). A perda de massa é
menor na regeneração com Steam versus N2 (13-26% versus 18-46%). O GAC/PNS 850-600 μm
apresenta melhor RE para N2 (cafeína: 88,0-76,2%; paracetamol: 68,0-62,3%) e Steam (cafeína: 101,5-
91,0%; paracetamol: 69,8-69,7%) do que o cGAC. Ao longo dos ciclos de regeneração ocorre a
diminuição gradual da área superficial e da microporosidade dos GAC, sem alterações relevantes da
química superficial no cGAC, contrariamente ao GAC/PNS. A regeneração de GAC depende de
múltiplos fatores com o adsorvato a desempenhar um papel crucial, assim a otimização dos processos
de regeneração para GAC saturados com adsorvatos menos propensos à regeneração reveste-se da maior
importância.
The growing relevance of activated carbon adsorption processes, namely for the control Pharmaceutically Active Compound (PhAC) in water treatment, requires the evaluation of their regeneration to maximize its sustainability and reduce costs. In this work, it was addressed the adsorption of two PhAC (caffeine and paracetamol) by granular activation carbons (GAC) – cGAC (commercial) and GAC/PNS (lab-made from pine nut shells). For each GAC/PhAC system, kinetic profiles, adsorption capacity and regeneration efficiency were evaluated, varying the particles size (425-300 μm or 850-600 μm) and the thermal regeneration agent (N2or Steam). The kinetic assays reveled that caffeine has the fastest kinetic rate, however, for all cases the equilibrium is reached within 24h, following a pseudo-second order kinetic model. For equilibrium assays, all compounds follow a Langmuir model, reveling superior adsorption capacity for GAC/PNS in comparison to cGAC (caffeine: 400 versus 250 mg/g; paracetamol: 394 versus 200 mg/g). The saturation/regeneration/reuse assays revealed the influence of several factors in the regeneration efficiency (RE). The larger GAC particles (850-600 μm) allow superior RE values (caffeine: 95,6- 91,6%; paracetamol: 78,8-61,8%). Thermal regeneration under N2, instead for under steam, leads to better RE (caffeine: 98,5-81,9% versus 154,0-53,6%; paracetamol: 78,8-33,5% versus 60,0-25,6%). Mass loss is lower under steam regeneration, when comparing to N2 (13-26% versus 18-46%). Comparing both GAC, data shows that GAC/PNS 850-600 μm presents better RE for N2 (caffeine: 88,0- 76,2%; paracetamol: 68,0-62,3%) and steam (caffeine: 101,5-91,0%; paracetamol: 69,8-69,7%). Throughout the regeneration cycles, superficial area and microporosity of the GAC suffers gradual reduction, without relevant changes on the surface chemistry for cGAC, contrarily to GAC/PNS. Summarizing, GAC regeneration depends on several factors with adsorbate playing a major role, so process optimization for GACs saturated with adsorbates less prone to regeneration is of the utmost importance.
The growing relevance of activated carbon adsorption processes, namely for the control Pharmaceutically Active Compound (PhAC) in water treatment, requires the evaluation of their regeneration to maximize its sustainability and reduce costs. In this work, it was addressed the adsorption of two PhAC (caffeine and paracetamol) by granular activation carbons (GAC) – cGAC (commercial) and GAC/PNS (lab-made from pine nut shells). For each GAC/PhAC system, kinetic profiles, adsorption capacity and regeneration efficiency were evaluated, varying the particles size (425-300 μm or 850-600 μm) and the thermal regeneration agent (N2or Steam). The kinetic assays reveled that caffeine has the fastest kinetic rate, however, for all cases the equilibrium is reached within 24h, following a pseudo-second order kinetic model. For equilibrium assays, all compounds follow a Langmuir model, reveling superior adsorption capacity for GAC/PNS in comparison to cGAC (caffeine: 400 versus 250 mg/g; paracetamol: 394 versus 200 mg/g). The saturation/regeneration/reuse assays revealed the influence of several factors in the regeneration efficiency (RE). The larger GAC particles (850-600 μm) allow superior RE values (caffeine: 95,6- 91,6%; paracetamol: 78,8-61,8%). Thermal regeneration under N2, instead for under steam, leads to better RE (caffeine: 98,5-81,9% versus 154,0-53,6%; paracetamol: 78,8-33,5% versus 60,0-25,6%). Mass loss is lower under steam regeneration, when comparing to N2 (13-26% versus 18-46%). Comparing both GAC, data shows that GAC/PNS 850-600 μm presents better RE for N2 (caffeine: 88,0- 76,2%; paracetamol: 68,0-62,3%) and steam (caffeine: 101,5-91,0%; paracetamol: 69,8-69,7%). Throughout the regeneration cycles, superficial area and microporosity of the GAC suffers gradual reduction, without relevant changes on the surface chemistry for cGAC, contrarily to GAC/PNS. Summarizing, GAC regeneration depends on several factors with adsorbate playing a major role, so process optimization for GACs saturated with adsorbates less prone to regeneration is of the utmost importance.
Descrição
Tese de Mestrado, Química, 2023, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Carvão ativado granular (GAC) Cafeína Paracetamol Adsorção Regeneração térmica Teses de mestrado - 2023