Biosorption of nickel and cadmium in the presence of diethylketone by a Streptococcus equisimilis biofilm supported on vermiculite

Abstract

a b s t r a c tA Streptococcus equisimilis biofilm supported on clays was used to decontaminate aqueous solutions containing diethylketone (DEK), nickel and/or cadmium, in a batch mode. The interaction between the sorbent matrices and the different sorbates, individually and in binary combinations, was evaluated. It was demonstrated that the growth of S. equisimilis is negatively affected by concentrations higher than 80 mg l À1 of Ni and 5 mg l À1 of Cd. DEK and Cd uptakes are positively correlated with the mass of vermiculite without biofilm, as observed in singular sorbate experiments. The same trend is observed for sorption percentages, reporting to the initial solution concentrations, as values higher than 90% were achieved for both pollutants. Although Ni uptake decreases as the mass of vermiculite increases, the percentage of sorbed Ni increased, reaching a maximum value of 100%. It was demonstrated that Ni and DEK, when mixed, present higher sorption values, suggesting a synergetic interaction between these two pollutants, whereas when DEK and Cd are mixed, the sorption of DEK decreases significantly, revealing a negative effect of Cd over the retention of DEK. It was also observable that for sorbent mass higher than 0.085 g the simultaneous uptake of DEK and Ni by the biofilm supported on vermiculite decreases, but the sorption percentage tends to increase, reaching values of 100% for 40 g of vermiculite. As the mass of sorbent increases the sorption percentage of both sorbates, DEK and Cd, tends to increase, reaching maximum values higher than 98%. These sorption systems are effective and the use of a biofilm may be an important advantage for the treatment of aqueous solutions contaminated with specific pollutants.

Biosorption of Multicomponent Solutions: A State of the Art of the Understudy Case

“…The massive research concerning biosorption of metals is an unsurprising fact, taking into account not only the toxicity effect and increased discharge of these contaminants into the environment but also the nature of adsorption and ion exchange mechanisms. Nevertheless, it is also crucial to highlight that regardless the continuous increase in published research related to the biosorption of hazardous substances and/or elements, there has been little or no exploitation in a pilot and industrial scale and/or context [18] and on the decontamination of multicomponent solutions [3,4,7,22,23]. In fact, despite the biosorption process that has been discussed in literature for 60 years with over 13,000 scientific papers in peer-reviewed journals [19], so far most of this research was performed in a laboratory scale, using batch tank reactors or packed mini-column, and has not been extensively implemented in an industrial scale and in multicomponent solutions.…”

“…The team of the Centre of Biological Engineering from the University of Minho, Portugal, has also been contributing to the study and understanding of (i) the scale-up of biosorption processes from a laboratory scale to a pilot scale and (ii) the increase of solution complexity to be decontaminated, evolving from single-component solutions to multicomponent solutions, mixing organic and inorganic compounds [3,4,7,9,15,24], the main subject of this chapter.…”

“…More complex systems were further evaluated [4] with a suspended bacterial culture of into account not only the concentrations employed but also the toxicity of the metals. In these experiments, a common increase in terms of sorption efficiency was observed, and this may be explained by the functional groups present on the biofilm that can implement the substrate molecule adsorption and eventually promote the biodegradation of diethylketone and by the increase of the available sites for sorption.…”

“…Metals including cadmium, chromium (III and VI), copper, lead, mercury, nickel and zinc are reported to inhibit microbiological processes such as acidogenesis, methanogenesis, nitrogen transformation, biomass production and enzymatic activity [22]. S. equisimilis exposure (in the form of biofilm supported into vermiculite or in suspension) to solutions containing either Cd(II) or Ni(II) (5-100 mg/L) led to microbial growth inhibition [3,4]. Nevertheless, it is important to mention that the addition of metals may also have the opposite effect and enhance and/or stimulate microbiological processes.…”

“…The non-natural redistribution of these chemicals has culminated first in their increasing discharge and accumulation into the different environmental matrices and second in the development of environmental and health problems (Figure 1) [3,4]. Therefore, there is a constant search for economical, efficient, effective and eco-friendly processes able to not only decontaminate wastewaters but also ensure that the presence of the pollutants discharged into the aquatic systems is below the permissible limits.…”