Abstract

HERNANDEZ-BOTIA, Angie Lorena et al. Performance of packed - bed corncob (Zea mays) in the removal of iron contained in acid mine drainage. Ciencia en Desarrollo [online]. 2020, vol.11, n.2, pp.185-203.  Epub Mar 27, 2021. ISSN 0121-7488.  https://doi.org/10.19053/01217488.v11.n2.2020.11279.

The ability of corncob (Zea mays) to remove iron contained in acidic mine drains (AMD) from coal in laboratory-scale packed bed reactors was evaluated. The tests had an effluent filtering phase, through the bed, at a flow rate of 5 mLxmin-1 and a column wash, with distilled water, in order to remove weakly adsorbed material. The variables evaluated were: (i) modification of the corncob with sodium hydroxide (NaOH) or citric acid (C6H8O7) and (ii) iron concentration in the AMD of 500 ppm, 1,000 ppm and 2,000 ppm. At the same time, trials were performed at the same conditions, but, with washes of distilled water to the corncob, each 400 mL of filtered AMD, in order to avoid saturation of the system. The treated effluent was monitored every 80 min through pH and iron measurements (atomic absorption spectroscopy). The biomasses were physicochemically characterized at the beginning and at the end of the process using FTIR. Overall, the pH of AMD played an key role in the metal removal capacity, mainly when iron concentrations of 500 Fe ppm were used, since the protons of this solution have a greater competition for the active adsorption sites in the packed bed, thus reducing the available effective surface area. The previous did not occur when using modified corncob with NaOH and iron concentrations higher than 1,000 ppm, due to the increased collisions between iron and the packed bed of corncob, which would mitigate the effect of pH. The tests with sporadic washes during the AMD filtering confirmed that the prolongation of the biomass reuse time is only possible if this effect is reduced. This work that pointed to the removal of iron contained in AMD with chemically modified corncob, could be an alternative to provide parameters of effluent remediation treatment in a simple and economical way that may be coupled to other passive remediation systems at greater scale, thus contributing to the reduction of the negative impact of contaminating leachates.

Keywords : Chemical conditioning; adsorption; biomass; coal mine; remediation.

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