Biosorption

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Bioresource Technology 99 (2008) 801–806

Biosorption of Cr (VI) using a bacterial biofilm supported on granular activated carbon and on zeolite
Sandra Lameiras, Cristina Quintelas *, Teresa Tavares
IBB-Institute for Biotechnology and Bioengineering, Centre for Biological Engineering, University of Minho, 4710-057 Braga, Portugal Received 16 May2006; received in revised form 20 October 2006; accepted 24 January 2007 Available online 26 March 2007

Abstract Two mini-columns partially filled with granular activated carbon (GAC) and/or a natural zeolite, covered by a bacterial biofilm of Arthrobacter viscosus, were used in a continuous flow system to remove Cr (VI) from solutions with initial concentration of 70 mg/l and a working pH rangingbetween 4.5 and 5.5. Three different set-up’s were used: two columns in series filled GAC covered with a biofilm, two columns in series filled with zeolite covered with a biofilm and a column filled with GAC followed by another column filled with zeolite, both supports covered with biofilm. Comparatively, the biosorption system supported on GAC reaches similar removal values, 19%, as the one supported onthe zeolite, 18%, but when these two beds are used in combination better performances are reached, i.e. 42% removal. The maximum uptake values ranged from 0.57 mgCr/gSupport to 3.58 mgCr/gSupport. The interactions between metal ions and functional groups on the cell wall surface of the biomass were confirmed by FTIR. GAC was regenerated with steam draughting and reused twice. The first regenerationcaused a decrease in the removal capacity of 38% and the second regeneration caused a total decrease in the removal capacity of 76%. Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Activated carbon; Biofilm; Biosorption; Chromium (VI); Zeolite

1. Introduction Environmental pollution by heavy metals is mainly caused by industrial and agricultural processes. Removal of heavy metals fromwastewater is usually achieved by physical and chemical processes which include precipitation, coagulation, reduction, membrane processes, ion exchange and adsorption (Pagnanelli et al., 2001). This work aimed at the definition of a sustainable, lowcost environmental technology targeted at small but locally vibrant industries producing wastewater with low concentration of heavy metals. These units workwithin tight budgets and are not really motivated to treat their wastes by conventional pollution abatement technology, as it is too expensive and not completely effective when applied to diluted solutions.
*

Corresponding author. Tel.: +351 253604400; fax: +351 253678986. E-mail address: cquintelas@deb.uminho.pt (C. Quintelas).

The development of a robust biosorption system consisting of abacterial biofilm supported on activated carbon and on a naturally occurring zeolite is proposed. On one hand, the ability of GAC to remove organic compounds that usually are also present in this kind of industrial wastewater seems to be a good property to be taken in consideration, in actual applications of the system under study. On the other hand, naturally occurring zeolite is not as expensive asGAC and may work as a good support for the biofilm in a second treatment unit, performing the residual metal removal that was not accomplished by the first bed. The uptake of heavy metals ions can take place by entrapment in the cellular structure of many materials of biological origin and subsequent sorption onto the binding sites present in the cellular structure. This uptake method isindependent of the biological metabolic cycle and is known as biosorption or passive uptake (Kapoor et al., 1999). Microorganisms are quite adequate for heavy metals

0960-8524/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2007.01.040

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S. Lameiras et al. / Bioresource Technology 99 (2008) 801–806

biosorption, due to their ability to sorb metal ions,...