The efficiency of electrolysis (EC/Cl2) and photo-assisted electrolysis (EC/UV/Cl2) methods, in the presence of chloride, for the abatement of real dairy waste from a producer in the Triangulo Mineiro region of Brazil, was evaluated. A complete 23 factorial design was performed for the variables time, pH and current. After determining the ideal pH, a Central Compound Design (CCD) was performed, where the applied current (533.42 mA) and treatment time (60.45 minutes) were maximized. The effluent was subsequently submitted to prolonged EC/Cl2 and EC/UV/Cl2 treatment in order to evaluate the behaviour of specific environmental parameters over time. The EC/UV/Cl2 method was more efficient than simple EC/Cl2 treatment. The EC/UV/Cl2 method resulted in a reduction of all environmental parameters investigated to levels within legal standards for effluent discharge. A relatively low cost of treatment is obtained with Energy per Order (EEO) values of 0.89 and 1.22 kWh m−3 order−1 for the EC/UV/Cl2 and EC/Cl2 treatments, respectively. The electrochemical production of free chlorine species followed by subsequent photolysis and production of radical species can convert a simple electrochemical process into an advanced oxidation process (AOP).
The use of chicken eggshells and ferrous metal waste were evaluated as feedstock for the synthesis of Ca2Fe2O5 perovskite. The solid Ca2Fe2O5 obtained was applied as heterogeneous catalyst in the transesterification reaction
of soybean oil with methanol for biodiesel production. The calcium ferrite (Ca2Fe2O5) obtained from waste materials was formed at temperatures above 898 K and its basic force was very similar to that one presented in the same structure obtained using high-purity
reagents. The formation of the Ca2Fe2O5/CaO system occurred for both catalysts at higher temperatures. The catalysts Ca2Fe2O5lab and Ca2Fe2O5res presented the same basic strength, 0.469 and 0.473
mmol/g, respectively. This fact indicates that both cata- lysts have similar structures even though they were prepared with very different origins of reagents. Besides that, the residual Ca2Fe2O5 perovskite showed a good catalytic performance in the transesterification
reaction. The transesterification reaction led to yields of biodiesel greater than 80 %, at 333 K, methanol to oil molar ratio of 3:1 and 10 h of batch reaction.
O metal cromo, presente em rejeitos das indústrias de couro, quando descartado de modo inadequado, ocasiona severos danos à saúde humana e ao equilíbrio ambiental. O objetivo do presente estudo foi otimizar o processo de biossorção de cromo de resíduos de curtume empregando o biossólido em sistema de fluxo contínuo. O biossólido de uma estação de tratamento de esgoto foi empregado como material biossorvente em sistema de filtros com fluxo contínuo. As análises de remoção de cromo foram realizadas em diferentes variações de pH, massa do biossorvente e tempo de processamento. A otimização do processo ocorreu em pH 4,30, tempo superior a 2 horas, 2,93 gramas de biossólido com remoção de cromo superior a 90% em sistema de fluxo contínuo. As isotermas de Freundlich revelaram adequação do processo à adsorção física. Trata-se, portanto, de um método alternativo, renovável, de fácil aplicação, eficiente, podendo ser empregado juntamente com os processos clássicos em tratamento de efluente de curtume.
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