No abstract

No abstract

No abstract

The desorption of La, Eu and Yb was studied in this work. The purpose of this work was to verify the reversibility of the sorption reaction, and thus the possibility of the desorption process for simultaneous metal recovery and regeneration of the biomass. The desorption of calcium ions at different levels of pH using mineral acid was also verified and the Ca release increased with decreasing pH, achieving 2.5 mequiv. gat pH 2 and 2.8 mequiv. g −1 using 0.1 mol L −1 HNO 3 . Several eluting agents at different concentrations were tested to desorb the lanthanides including nitric and hydrochloric acids, calcium nitrate and chloride salts, EDTA, oxalic and diglycolic acids. 95-100% desorption for all metals was obtained with 0.3 mol L −1 HCl. La desorption with the other eluting agents was 70% with 2 mol L −1 CaCl 2 , 83.7%, with 0.5 mol L −1 EDTA and 88.4% with 0.023 mol L −1 diglycolic acid. A plateau was reached when a liquid to solid ratio (L/S) of 2 L g −1 was used with 0.1 mol L −1 HNO 3 . Desorption levels ranged between 85 and 95%. At the same (L/S) ratio, 0.2 mol L −1 HCl was able to elute all the metals from the individual metal loaded biomass, although it could not remove the metals completely from the mixed-metal loaded biomass. The desorption levels decreased with increasing metal sorption affinity as follows, 94.0, 86.3 and 75.2% for Yb, La and Eu, respectively when the eluting agent was 0.1N HCl. There was no difference between not washing the biomass at all and washing it either once or twice after the sorption process.

Heavy metals can be removed from effluents and recovered using physico-chemical mechanisms as biosorption processes. In this work "Arribada" seaweed biomass was employed to assess its biosorptive capacity for the chromium (Cr 3+ ) and lead (Pb 2+ ) cations that usually are present in waste waters of plating industries. Equilibrium and kinetic experiments were conducted in a mixed reactor on a batch basis. Biosorption equilibrium and fluidsolid mass transfer constants data were analyzed through the concept of ion exchange sorption isotherm. The respective equilibrium exchange constants (K eqCr = 173.42, K eqPb = 58.86) and volumetric mass transfer coefficients ((k mCr a) = 1.13 × 10 −3 s −1 , (k mPb a) = 0.89 × 10 −3 s −1 ) were employed for the dynamic analysis of Cr and Pb sorption in a fixed-bed flow-through sorption column. The breakthrough curves obtained for both metals were compared with the predicted values by the heterogeneous model (K eqCr = 171.29, K eqPb = 60.14; k mCr a = 7.81 × 10 −2 s −1 , k mPb a = 2.43 × 10 −2 s −1 ), taking into account the mass transfer process. The results suggest that these algae may be employed in a metal removal/recovery process at low cost.