Resumo Sintetizaram-se pigmentos do sistema Zn2-xNixSiO4 variando a proporção molar de zinco e níquel, partindo da estrutura willemita (Zn2SiO4) à olivina (Ni2SiO4), usando areia descartada de fundição (ADF) e sílica comercial como fontes de SiO2. A ADF foi caracterizada por análise química e DRX. A síntese dos pigmentos seguiu rota cerâmica, com x = 0, 0,5, 1, 1,5 e 2,0 mol e calcinação a 1200 °C. Os pigmentos foram caracterizados mediante DRX e medidas colorimétricas. Os resultados mostraram que, apesar da presença de alumina e ferro na ADF, as fases cristalinas e cor dos pigmentos foram similares para ambas as fontes de sílica. Teores menores de níquel favoreceram a formação de willemita e maiores a de olivina. Todos os pigmentos (com e sem ADF) dispersos em dois esmaltes e queimados em forno semi-industrial desenvolveram coloração marrom, indicando instabilidade destes nas matrizes usadas, mas confirmando a viabilidade de substituição da sílica comercial por ADF.
Two reactors were tested to generate Al3+, that quickly form Al(OH)3 used to remove dissolved silica. Reactor (A) has parallel plates with a vertical zig-zag hydraulic path; this configuration has the disadvantage of important load lost due to the opposition between a going down water flux and the electrochemically generated gas bubbles naturally moving up in some regions. Reactor (B) consisted on an alternating arrangement of a reaction camera with only ascendant flow of water, followed by a chamber designed for water drop. The reaction zone, where bubbles generate is the same where the water moves up. Reactor (B) saves energy and had a better performance for equivalent conditions when compared with reactor (A) to remove silica.
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