Microbial biosorption of copper and lead from aqueous systems

The improved methods of heavy metals removal by biosorbents: A review

For decades, a vast array of innovative biosorbents have been found out and used in the removal of heavy metals, including bacteria, algae and fungi, etc. Although extensive biological species have been tried as a biosorbent for heavy metals removal, for removal efficiency or economy efficiency limited, it has failed to make a substantial breakthrough in practical application. Thus, many improved methods based on biosorbents emerged. In this review, based on the literature and our research results, we highlight three types of novel methods for biosorbents removal of heavy metals: chemical modification of biosorbents; biomass and chemical materials combination; multiple biomass complex systems. We mainly focus on their configuration, biosorption performance, their creation method, regeneration/reuse, their application and development in the future. Through the comparative analysis of various methods, we think that intracellular autogenous nanomaterials may open up another window in biosorption of heavy metals area. At the same time, the combination of various treatment methods will be the development tendency of heavy metal pollution treatment in the future.

Mixed-species biofilms cultured from an oil sand tailings pond can biomineralize metals

Here, we used an in vitro biofilm approach to study metal resistance and/or tolerance of mixed-species biofilms grown from an oil sand tailings pond in northern Alberta, Canada. Metals can be inhibitory to microbial hydrocarbon degradation. If microorganisms are exposed to metal concentrations above their resistance levels, metabolic activities and hydrocarbon degradation can be slowed significantly, if not inhibited completely. For this reason, bioremediation strategies may be most effective if metal-resistant microorganisms are used. Viability was measured after exposure to a range of concentrations of ions of Cu, Ag, Pb, Ni, Zn, V, Cr, and Sr. Mixed-species biofilms were found to be extremely metal resistant; up to 20 mg/L of Pb, 16 mg/L of Zn, 1,000 mg/L of Sr, and 3.2 mg/L of Ni. Metal mineralization was observed by visualization with scanning electron microscopy with metal crystals of Cu, Ag, Pb, and Sr exuding from the biofilms. Following metal exposure, the mixed-species biofilms were analyzed by molecular methods and were found to maintain high levels of species complexity. A single species isolated from the community (Rhodococcus erythropolis) was used as a comparison against the mixed-community biofilm and was seen to be much less tolerant to metal stress than the community and did not biomineralize the metals.

In situ heavy metals (copper, lead and cadmium) in different plankton compartments and suspended particulate matter in two coupled Mediterranean coastal ecosystems (Toulon Bay, France)

We monitored the concentrations of copper, lead and cadmium in seawater, in suspended particulate matter (SPM) and in bacteria, phyto- and zooplankton communities separated from abiogenic particles, over a one year cycle in two coupled Mediterranean coastal ecosystems (Little Bay (LiB) and Large Bay (LaB)). Metals were present in seawater in the order Cu>Pb>Cd in both bays and showed important variations within the same month than among months. In LiB, their concentrations were between 0.62 and 2.82 microg Cu l(-1), 0.16 and 19 microg Pb l(-1) and 0.007 and 0.14 microg Cd l(-1), respectively, whereas in LaB, they were between 0.23 and 2.11 microg Cu l(-1), 0.09 and 0.76 microg Pb l(-1) and not detected and 0.65 microg Cd l(-1). SPM play an important role on metal adsorption, especially for copper. Bioaccumulation factors showed that bacteria and phytoplankton accumulate metals whereas zooplankton tends to biodiminish them in the plankton food web.

Biosorption of cadmium, copper, lead and zinc by inactive biomass of Pseudomonas Putida

The accumulation of Cd(II), Cu(II), Pb(II) and Zn(II) at mg L(-1) concentration levels by inactive freeze-dried biomass of Pseudomonas Putida has been investigated. These metals could be efficiently removed from diluted aqueous solutions. A contact time of 10 min was sufficient to reach equilibrium. The pH has a strong effect on metal biosorption and the optimal pH values were 6.0, 5.0-6.0, 6.0-6.5 and 7.0-7.5 for Cd(II), Cu(II), Pb(II) and Zn(II) respectively. Under these conditions there was 80% removal for all metals studied. The process of biosorption can be described by a Langmuir-type adsorption model. This model accounts for 98% of the data variance. The K(A) and q(max) parameters for each metal are strongly correlated (at confidence levels greater than 98%) with the metal acidity, quantified by the constant of the corresponding M(OH)(+) complex, thus confirming previous assertions by other authors.

Bioaccumulation and biosorption of lead by poultry litter microorganisms

Microorganisms are known to interact with metals through a number of mechanisms, including binding the metals to their cells' walls and intracellular accumulation. Poultry litter has a high density of various microorganisms along with many nutrients. The objective of this research was to study the removal of Pb from an aqueous solution by the microorganisms found in poultry litter under an aerobic environment. A Pb(NO3)2 solution was treated with the aqueous extract of either the nonradiated litter or gamma-radiated litter in order to differentiate between the removal of Pb through bioaccumulation (by the living organisms) and biosorption (by the dead organisms). Lead removal was measured using anodic stripping voltammetry. Both the nonradiated and the gamma-radiated litter removed significant amounts of Pb. After 14 d, the amount of Pb removed through bioaccumulation by the nonradiated litter and through biosorption by the radiated litter was about 44 and 30%, respectively. There was no increase in Pb removal between 14 and 60 d. The biomass density of the aqueous extract of poultry litter increased significantly in the presence of 400 ppb Pb(NO3)2.

Bioremediation of metal contamination

Recent studies have demonstrated that microbes might be used to remediate metal contamination by removing metals from contaminated water or waste streams, sequestering metals in soils and sediments or solubilizing metals to aid in their extraction. This is primarily accomplished either by biosorption of metals or enzymatically catalyzed changes in the metal redox state. Bioremediation of metals is still primarily a research problem with little large-scale application of this technology.