Batch desorption studies and multiple sorption-regeneration cycles in a fixed-bed column for Cd(II) elimination by protonated Sargassum muticum

The protonated alga Sargassum muticum was employed in batch desorption studies to find the most appropriate eluting agent for Cd(II)-laden biomass regeneration. Eleven types of eluting solutions at different concentrations were tested, finding elution efficiencies higher than 90\% for most of the desorbents studied. Total organic carbon and biomass weight loss measurements were made. The reusability of the protonated alga was also studied using a fixed-bed column. Eleven consecutive sorption-regeneration cycles at a flow rate of 10 mL min(-1) were carried out for the removal of 50 mg L-1 Cd(II) solution. A 0.1 M HNO3 solution was employed as desorbing agent. The column was operated during 605 h for sorption and 66 h for desorption, equivalent to a continuous use during 28 days, with no apparent loss of sorption performance. In these cycles, no diminution of the breakthrough time was found; although, a relative loss of sorption capacity, regarding the found in the first cycle, was observed. The slope of the breakthrough curves experiments a gradual increase reaching its maximum value for the last cycle tested (40\% greater than for the first one). The maximum Cd(II) concentration elution peak was achieved in 5 min or less, and the metal effluent concentration was always lower than 0.9 mg L-1 after 1 h of elution. The maximum concentration factor was determined to be between 55 and 109. (c) 2006 Elsevier B.V. All rights reserved.