Adsorção de eteramina por Luffa Cylindrica lavada em batelada e em coluna de leito fixo visando o tratamento de efluentes de flotação

Abstract

Etheramines are commonly used as quartz collector reagent in the concentration of iron ores and others, with silicate gangue, by flotation. The water reuse in mineral processing as well as the quality of hydric bodies that receive the effluents can be benefited from the removal of amines from the liquid phase. Studies on the impacts of etheramines contained in wastewater from mineral processing are still scarce, but due to the water crisis, unknown impacts may arise from not treating these effluents. In the present study, synthetic effluents containing etheramines were treated by adsorption, both in batch and in a fixed bed column, using luffa cylindrica as biosorbent. The biosorbent preparation involved a washing step and the release of extractives from the material was determined by COD measures. In three cross-current washing stages of 60 min, the COD was reduced from 217mg/L to 42mg/L in the second stage and to 36mg/L with an additional third stage. Three different configurations of batch adsorption systems were evaluated: roller system, jar-test and flasks shaker. The shaker system showed greater stability and more ease handling, with a stirring rate of 150rpm. The adsorption using the adsorbent/solution ratio of 4g/L reached the equilibrium in 40min, with etheramine removals equal to 71.5% and 58.8% for initial EDA concentrations of 50mg/L and 200mg/L, respectively. The effect of pH (7.5; 8.5; 9.5 and 10.5) on the amount adsorbed at 22°C, for an initial EDA concentration of 150mg/L, agitation of 150rpm in 2 hours was investigated. It was observed that the control and increase of the pH from 7.5 to 9.5 provided a small increase in the amount adsorbed, but a subsequent rise slightly impacted the adsorption. At equilibrium, the adsorption capacity was 7.98mgTOCg/g (Ci=50mg/L) and 22.47mgTOC/g (Ci=200mg/L) and the adsorption kinetics was well represented by a pseudo second order kinetic equation. The Freundlich, Redlich-Peterson and Sips adsorption isotherm models were similar with better fits, with correlation coefficients equal to 0.9830, 0.9825 and 0.9824, respectively. In a semi-continuous adsorption system (column of 13mm in diameter and 25cm in height, bed occupancy fraction of 0.20-0.26 and porosity above 60%) the breakthrough curves were well represented by the Yan model. At pH-7.5 and 26°C, the effect of bed height (5, 10, 15 and 20cm), feed flowrate (3.2; 8.9; 14.5 and 22.8ml/ min) and initial EDA concentrations of 50mg/L and 150mg/L were evaluated. It was observed that at higher application rates (17.177ml/cm².min) the column tends to a fast exhaustion, however, there was greater stability using a lower surface application rate (6.705ml/cm².min). In general, the C/Co ratio at the exit of the column rose rapidly to values close to 0.4, indicating a rapid adsorption, but that was followed for long periods, before the exhaustion. The shortest exhaustion time was 60min for hL=10cm for the highest superficial application rate of 17.177ml/min.cm2 and the longest time was 360min for the lowest superficial application rate (2.411ml/min.cm2 ). From the results obtained, it can be inferred that the column adsorption of etheramines by luffa cylindrica presents high potential for use in the treatment of liquid effluents containing residual concentrations of amine.