Caracterização e estudo do mecanismo de sorção de fluoretos em carvão de osso

• Ano de defesa: 2016
• Autor(a) principal: Elbert Müller Nigri
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Sorção de flúor; Processos contínuos; Carvão de osso; Regeneração; Processos em batelada; Tecnologia mineral; Engenharia de minas; Fluoretos
• Link de acesso: http://hdl.handle.net/1843/BUBD-ACMHHX

The sorption of fluoride in bone char was investigated in batch processes (shaker and rolling bottle) and columns. Bone char adsorption capacity in the presence of competing ions and in simulated groundwater were also evaluated. The compounds aluminum Chloride (AlCl3), calcium chloride (CaCl2), magnesium chloride (MgCl2), calcium hydroxide (Ca(OH)2) and ferric chloride (FeCl3) were used for bone char surface modification, with possible variations in its sorption capacity being analyzed. Chemical regeneration tests using sodium hydroxide (NaOH) and hydrochloric acid (HCl) solutions, as well as thermal regeneration tests, were also conducted. Results suggest that bone char can be used as a sorbent for removing fluorides in batch processes, with a maximum sorptive capacity of 6,77mg/g,.. Analyses of samples in its various stages throughout the study showed that the fluoride was inserted in the hydroxyapatite (HAP) structure present in bone char, forming HAP fluoridated and proving this to be one of fluoride removal methods for bone char. Regarding the regenerative processes studied, the chemical regeneration with NaOH showed promising, displaying a maximum sorptive capacity of 4,27mg/g for bone char regenerated in batch processes. Furthermore, bone char could be regenerated with NaOH in continuous processes for five cycles. The heat treatment led to an increase in bone char crystallinity and to migration of fluoride from the bone char surface to its interior. The isolated presence of chloride, sulfate or nitrate ions in solution did not affect the bone char sorption capacity for fluorides, whereas the presence of carbonate or bicarbonate ions had a negative effect, reducing the sorption capacity in about 70 and 30%, respectively. The fluoride sorption in synthetic groundwater by bone char did not differ from fluoride sorption in distilled water as well. Finally, the model of Yan presented the best fit for the breakthrough curve forecasting in experiments with columns.