This study assessed the degradation of bromothymol blue in a Venturi device based on a hybrid process that combines hydrodynamic cavitation (HC) and hydrogen peroxide (H2O2). A Rotatable Central Composite Design (RCCD) was used to optimize the following variables: pressure, reaction time and molar ratio of hydrogen peroxide. Degradation efficiencies were evaluated based on Chemical Oxygen Demand (COD) and color removals before and after Venturi treatment. Maximum COD (93.42%) and color (93.28%) removals were observed at 4.0 bar inlet pressure, at a treatment time of 25 minutes and at H2O2/effluent (dye) molar ratio of 30:1. The hydrodynamic cavitation/hydrogen peroxide system has great potential to remove normally recalcitrant organic pollutants.
RESUMOO biodiesel representa uma alternativa essencial para atender à crescente demanda energética da sociedade moderna de forma sustentável. Os objetivos do presente estudo foram otimizar a síntese do biodiesel a partir do óleo residual de fritura em banho ultrassônico, determinar o custo de produção do biodiesel e caracterizar o produto obtido a partir dos parâmetros estabelecidos pela Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP). A matéria-prima utilizada foi o óleo residual de fritura, coletado no campus II da Universidade Federal do Triângulo Mineiro. As rotas foram definidas pelo Planejamento Composto Central (PCC), que otimizou as variáveis; massa de hidróxido de sódio, tempo de reação e as massas de etanol e metanol. Posteriormente, as amostras foram caracterizadas, analisando os parâmetros; massa específica, ponto de congelamento, índice de peróxido e índice de insaturação. As análises do biodiesel otimizado (rendimento superior a 90%) ficaram dentro dos limites estabelecidos pela ANP. Os custos de produção do litro de biodiesel nas rotas metílica e etílica foram R$ 2,124 e R$ 2,453, respectivamente. O maior tempo de processo para a rota etílica (35%) que elevou o custo de produção (13,41%) do biodiesel nessa rota. A síntese de biodiesel otimizada a partir de óleo residual de fritura, em banho ultrassônico, constitui-se como um processo sustentável e economicamente viável para a produção em larga escala. Essa metodologia favorece a ampliação do uso de biodiesel (energia verde com menor custo de produção) como uma alternativa aos combustíveis à base de petróleo (óleo diesel). PALAVRAS-CHAVE: biocombustível,otimização, ultrassom.
The possibility of Pb2+, Cd2+, Ni2+ and Ba2+ ions removal from aqueous solution using light expanded clay aggregate (LECA) was investigated in this work. The central composite design (CCD) in response surface methodology (RSM) was used to optimize the operating parameters (adsorbent granulometry, absorption time and initial metal ions concentration) to reach the maximum ions removal in single and multi-elemental solutions. After optimization, the results shows that the removal efficiency decrease following the ion sequence Pb2+ > Ba2+ > Cd2+ > Ni2+ ions. The better efficiency (~95%) is observed for the Pb2+. The Langmuir and Freundlich isotherm models were applied to the equilibrium data at room temperature. The results revealed that data on LECA was very well fitted with Langmuir equations. The real interest of this work is to demonstrate that a simple material such as LECA can be used to remove extremely small levels of toxic metals, such as those found in drinking water. So our results could be the starting point for the development of a low-cost filtration system to remove toxic metals.
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