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Bacteria and cyanobacteria remove heavy metal because the cell wall has the ability to capture the heavy metals due to negatively charged groups within its fabric (Uslu & Tanyol 2006). There are several processes to remove heavy metals, such as transport across the cell membrane, biosorption to cell walls, entrapment in extra cellular capsules, precipitation, complexation and oxidation/reduction (Rai et al. 1981; Brady et al. 1994; Veglio et al. 1997). Bacteria are the most abundant and versatile of microorganisms (Mann 1990) and bacteria species such as Bacillus sp., Micrococcus luteus, Pseudomonas cepacia, Bacillus subtilis and Streptomyces coelicolor have been used for copper removal from wastewater (Nakajima 2002; Öztürk et al. 2004; Hassan et al. 2009). Veneu et al. (2013) used Streptomyces lumalinharesii for copper removal from wastewater and a removal of 81% was reported at an optimum pH of 5 with best fit to the Freundlich model. Öztürk et al. (2004) used S. coelicolor for copper removal and reported 21.8% removal at an optimum pH of 5 with a good fit to the Langmuir model. Uslu & Tanyol (2006) used P. putida for copper removal as a single component (in the presence of copper only) or as binary component (in the presence of copper along with other heavy metal, i.e., lead here) and reported an endothermic and spontaneous process with 50% copper removal from wastewater. Lu et al. (2006) used Enterobacter sp. J1 for copper removal and an adsorption capacity of 32.5 mg/g and a removal of 90% of copper removal was reported at pH >2. Even after four repeated adsorption and desorption cycles, the Enterobacter sp. J1 biomass achieved 79% removal. Nakajima (2002) studied removal of copper using Arthrobacter nicotianae bacteria from wastewater by electron spin resonance method, and found that copper ions present in bacterial cells are of octahedral structure with nitrogen and oxygen as ligand atoms and most copper in bacterial cells is combined with amino acid residues present in cell surface protein. Table 23 summarises the removal parameters for the sequestering of copper using bacteria as an adsorbent.

Table 23

Copper removal using bacteria as an adsorbent

AdsorbentInitial metal concentration (mg/L)pHBest model fitContact time (min)Adsorbent dose (g/L)Adsorption capacity (mg/g)Removal per cent (%)References
Paenibacillus polymyxa 25–500 Langmuir 120 – 112, 1,602 – Acosta et al. (2005)  
Escherichia coli 32–64 – – – – 8.846, 10.364 – Ravikumar et al. (2011)  
Pseudomonas stutzeri 30–100 Langmuir, Freundlich 30 36.2 – Hassan et al. (2009)  
Pseudomonas putida 0.1 Langmuir 10 6.6 80% Pardo et al. (2003)  
Sphaerotilus natans 100 Langmuir 150 60 – Beolchini et al. (2006)  
Sphaerotilus natans (Gram-negative bacteria) – – Langmuir 30 44.48 – Pagnanelli et al. (2003)  
Bacillus sp. (bacterial strain isolated from soil) 100 Langmuir 30 16.25. 1.64 – Tunali et al. (2006)  
Lactobacillus sp. (DSM 20057) 0.398–39.8 3–6 Langmuir 5–1,440 0.3–10 0.046 – Schut et al. (2011)  
AdsorbentInitial metal concentration (mg/L)pHBest model fitContact time (min)Adsorbent dose (g/L)Adsorption capacity (mg/g)Removal per cent (%)References
Paenibacillus polymyxa 25–500 Langmuir 120 – 112, 1,602 – Acosta et al. (2005)  
Escherichia coli 32–64 – – – – 8.846, 10.364 – Ravikumar et al. (2011)  
Pseudomonas stutzeri 30–100 Langmuir, Freundlich 30 36.2 – Hassan et al. (2009)  
Pseudomonas putida 0.1 Langmuir 10 6.6 80% Pardo et al. (2003)  
Sphaerotilus natans 100 Langmuir 150 60 – Beolchini et al. (2006)  
Sphaerotilus natans (Gram-negative bacteria) – – Langmuir 30 44.48 – Pagnanelli et al. (2003)  
Bacillus sp. (bacterial strain isolated from soil) 100 Langmuir 30 16.25. 1.64 – Tunali et al. (2006)  
Lactobacillus sp. (DSM 20057) 0.398–39.8 3–6 Langmuir 5–1,440 0.3–10 0.046 – Schut et al. (2011)  

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