Chromium(III) biosorption onto spent grains residual from brewing industry : equilibrium, kinetics and column studies

The use of industrial wastes for wastewater treatment as a strategy to their re-use and valorisation may provide important advances toward sustainability. The present work gives new insights into heavy metal biosorption onto low-cost biosorbents, studying chromium(III) biosorption onto spent grains residual from a Portuguese brewing industry both in batch and expanded bed column systems. Experimental studies involved unmodified spent grains and spent grains treated with NaOH. Metal uptake followed a rapid initial step, well described by the pseudo-second-order kinetic model up to 27 h, indicating chemisorption to be the rate-limiting step. Beyond this period intraparticle diffusion assumed an important role in the uptake global kinetics. The best fit for equilibrium data was obtained using the Langmuir model, with unmodified spent grains having the higher maximum uptake capacity (q max = 16.7 mg g1). In open system studies, using expanded bed columns, the best performance was also achieved with unmodified spent grains: Breakthrough time (C/C i = 0.25) and total saturation time (C/C i = 0.99) occurred after 58 and 199 h of operation, corresponding to the accumulation of 390 mg of chromium(III), 43.3 % of the total amount entering the column. These results suggest that alkali treatment does not improve spent grains uptake performance. Changes in biomass composition determined by Fourier transform infrared spectroscopy suggested hydroxyl groups and proteins to have an important role in chromium(III) biosorption. This study points out that unmodified spent grains can be successfully used as low-cost biosorbent for trivalent chromium.The authors would like to thank the Portuguese brewing industry UNICER for all the support and FCT (Fundacao para a Ciencia e a Tecnologia) financial support through the Grant PRAXIS XXI/BD/15945/98

Place des massifs granitiques de Zekkara, Tarilest et Béni-Snassène dans l'histoire géodynamique de la chaine hercynienne (Meseta orientale, Maroc)

Place of Zekkara, Tarilest and Béni-Snassène granitic massifs in the geodynamic history of hercynian orogeny (Eastern Meseta, Morocco). The paper presents the first detailed geochemical and petrographical study realised in Hercynian Zekkara, Tarilest and Béni-Snassène granitoids. These consist of metaluminous or peralu-minous magmas occuring in the crust at various levels and times. Major and trace elements compositions show a typical calc-alkaline trend characterized by enrichment in K20. The granitoids were formed by fractional crystallization of a magma derived from melt of an igneous crust. Compared with other well-studied Hercynian suites, these rocks are similar to post-collisional granitoids. No evidence to allow the existence of an old oceanic crust , this magmatism must be reattached at a tangential late Hercynian tectonic, a thinning crust and a mantled ascent model seems to be the better proposal.Cette note présente la première étude pétrographique et géochimique détaillée réalisée sur les granitoïdes hercyniens des massifs de Zekkara, Tarilest et Béni-Snassen. Ceux-ci correspondent à des magmas métalumineux ou hyperalumineux, mis en place de manière étagée dans le temps et à différents niveaux de la croûte continentale. Les compositions des éléments majeurs et traces, montrent une évolution typique des suites calco-alcalines potassiques post-collision-nelles. Les trois intrusions dérivent d'un magma crustal de nature ignée dont l'évolution est contrôlée par la cristallisation fractionnée. Aucun argument ne permettant d'évoquer des témoins d'une croûte océanique ancienne ce magmatisme serait à rattacher à une tectonique tangentielle tardi-hercynienne et un modèle d'amincissement crustal et de remontée du manteau est privilégié.El Hadi H., Reddad A., Giret Alain, Chabane Abdelkader, Hertogen J. Place des massifs granitiques de Zekkara, Tarilest et Béni-Snassène dans l'histoire géodynamique de la chaine hercynienne (Meseta orientale, Maroc). In: Géologie Méditerranéenne. Tome 27, numéro 3-4, 2000. pp. 159-173