Sorção de nitrato em carvão ativado tratado com CaCl2 : estudo de ciclos de sorção/regeneração

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

2012

RESUMO

Nitrate (NO-3) is an inorganic ion which is present naturally in the environment, being the most stable form of oxidized nitrogen. Due to its high solubility in water, it is possibly the groundwater contaminant more widespread in the world, causing problems in the production of drinking water and ecological disturbances. In this context, the objective of this study is to investigate the sorption capacity of the commercial granular activated carbon, chemically modified with CaCl2 to remove nitrate from aqueous solutions and to study the regeneration capacity of the sorbent under different conditions. For this purpose tests of sorption and desorption were carried out, determining the optimal process conditions: pH, residence time and concentration of solid sorbent. Further, equilibrium isotherms for this system were built. In the desorption process of activated carbon saturated with nitrate, water (60°C) and aqueous solutions of HCl, C6H8O7, NaOH, CaCl2 were employed. The best sorption conditions found in the experiments were as follow: pH 6.0, time 30 min and concentration of sorbent 20 g.L-1, using nitrate solutions with initial concentration of 20 mg.L-1. For regeneration tests, the residence time was set as 30 min, using 400 mL of CaCl2 2000 mg.L-1 to keep Ca2+ in solution. Therefore, it was possible to perform twenty cycles of sorption/regeneration (S/R), yielding 54% nitrate removal at the end of these cycles. During regeneration, the concentration of Ca2+ in the CaCl2 solution was monitored. After 20 S/R cycles, the sorbent was regenerated with 50 mL of HCl solution (100 mg.L-1) or 50 mL of H2O at 60°C. Additionally, more 20 cycles (S/R) were performed for the regenerated sorbent with HCl solution or H2O (60°C). Maximum removal values of nitrate (58%) were achieved in both cases at the end of each 20 cycles (S/R). A total of 60 cycles (S/R) were performed, achieving nitrate removal of 55% at the end of the last cycle. The Langmuir sorption isotherm type was found to be the best fit to experimental data, providing the energy constant or affinity of the process and also the maximum accumulation of nitrate in the sorbent.

ASSUNTO(S)

nitrato sorption carvao ativado regeneration nitrate solventes sorção activated carbon

ACESSO AO ARTIGO

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