Removal of color and turbidity in sugarcane juice treated by electrocoagulation with aluminum electrodes

Abstract The liming (Ca(OH)2 addition) and sulfitation (HSO3- addition) is the conventional treatment for purification of sugarcane juice (SCJ) in sugar cane mills to crystal sugar production. Although, the sulfite has been associated to human health problems, this industrial step kept untouchable or few studies have been made to change this scenery. This work aimed to evaluate the variables which influence the electrocoagulation performance on the SCJ purification as a sulfur-free crystal sugar process. A fractional factorial design with the surface response methodology was used to evaluate the influence of voltage, pH, soluble solids total (Brix), temperature and distance between the electrodes in the electrocoagulation process. The outputs were turbidity, juice color, sucrose contents (as pol%juice) and Reducing Sugars (RS). Residual aluminum was analyzed by voltammetry to control de aluminum releasing into the treated juice. The electrocoagulation reduced color and turbidity, in special at low pH (2.5), highest voltage (25 V) and minimal distance of electrode (1.0 cm). Although in this conditions, sucrose was converted into RS indicating partial hydrolysis. In this work, the most part of residual aluminum went to floated and precipitated phases (76.8% and 18.1%, respectively), whereas only 5.1% remained in the SCJ clarified. Electrocoagulation/electroflotation proved to be a potential technique as a substitute for sulfitation in SJC treatment, which ensures the production of safe food for humans. Resumo A caleagem [adição de Ca(OH)2] e a sulfitação (adição de HSO3-) são etapas do tratamento convencional do caldo de cana (CCA) em usinas para a produção de açúcar cristal. Embora a geração de sulfito esteja associada a problemas de saúde humana, essa etapa industrial manteve-se intocável, sendo que poucos estudos foram feitos para alterar esse cenário. Este trabalho teve como objetivo avaliar as variáveis que influenciam o desempenho da eletrocoagulação na purificação de CCA como um processo alternativo à produção de açúcar cristal sem uso de enxofre. Um planejamento fatorial fracionário com a metodologia de resposta de superfície foi utilizado para avaliar a influência da tensão, do pH, dos sólidos solúveis totais (Brix), da temperatura e da distância entre os eletrodos no processo de eletrocoagulação do caldo de cana. As respostas avaliadas foram turbidez, cor do caldo, teor aparente de sacarose (como pol%caldo) e açúcares redutores (AR). O alumínio res