Continuous metal biosorption applied to industrial effluents: a comparative study using an agricultural by-product and a marine alga

Fixed-bed column experiments have been conducted to evaluate the removal of metals from real industrial wastewaters. The effluents tested were provided by two different metallurgical companies: Industrial Gonabe, a galvanizing plant, and Sao Domingos mine, an abandoned sulfide mine. Sugar-beet pulp, a by-product of the sugar industry, and brown alga Fucus vesiculosus were used as biosorbents. The influence of pH on the sorption process was insignificant for the tests using Industrial Gonabe wastewater. On the contrary, an increase of pH improved metal sorption uptake and yield and saturation rate in the case of the Sao Domingos wastewater. A lower metal concentration in Sao Domingos wastewater resulted in a higher availability of metal-binding sites on the biomass. Better sorption parameters for both real wastewaters were obtained using brown alga Fucus vesiculosus. At pH 5, Zn sorption in continuous mode increased from 36 to 48% for Industrial Gonabe wastewater and from 34 to 37% for Sao Domingos wastewater. In the latter case, copper sorption increased from 73 to 88%. Breakthrough points that determine the service time of columns were reached later using alga as biosorbent. For Zn, column adsorption performance improved substantially with alga and its service time by 5 times. In the case of Cu, the breakthrough point of the second column was not reached during 1750 min of experimentation. The results obtained reaffirm the industrial applicability of these techniques.