title: Removal of mercury by foam fractionation using surfactin, a biosurfactant.
abstract: The separation of mercury ions from artificially contaminated water by the foam fractionation process using a biosurfactant (surfactin) and chemical surfactants (SDS and Tween-80) was investigated in this study. Parameters such as surfactant and mercury concentration, pH, foam volume, and digestion time were varied and their effects on the efficiency of mercury removal were investigated. The recovery efficiency of mercury ions was highly sensitive to the concentration of the surfactant. The highest mercury ion recovery by surfactin was obtained using a surfactin concentration of 10 × CMC, while recovery using SDS required < 10 × CMC and Tween-80 >10 × CMC. However, the enrichment of mercury ions in the foam was superior with surfactin, the mercury enrichment value corresponding to the highest metal recovery (10.4%) by surfactin being 1.53. Dilute solutions (2-mg L(-1) Hg(2+)) resulted in better separation (36.4%), while concentrated solutions (100 mg L(-1)) enabled only a 2.3% recovery using surfactin. An increase in the digestion time of the metal solution with surfactin yielded better separation as compared with a freshly-prepared solution, and an increase in the airflow rate increased bubble production, resulting in higher metal recovery but low enrichment. Basic solutions yielded higher mercury separation as compared with acidic solutions due to the precipitation of surfactin under acidic conditions.
authors.affiliation: Department of Life Science, National Chung Cheng University, 168 University Road, Minhsiung, Chiayi 621, Taiwan; E-Mails:  biohrc@ccu.edu.tw  (H.-R.C.);  biomjt@ccu.edu.tw  (M.-J.T.).
authors.forename: Hau-Ren
authors.initials: HR
authors.lastname: Chen
authors.forename: Chien-Cheng
authors.initials: CC
authors.lastname: Chen
authors.forename: A Satyanarayana
authors.initials: AS
authors.lastname: Reddy
authors.forename: Chien-Yen
authors.initials: CY
authors.lastname: Chen
authors.forename: Wun Rong
authors.initials: WR
authors.lastname: Li
authors.forename: Min-Jen
authors.initials: MJ
authors.lastname: Tseng
authors.forename: Hung-Tsan
authors.initials: HT
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Pan
authors.forename: Jyoti Prakash
authors.initials: JP
authors.lastname: Maity
authors.forename: Shashi B
authors.initials: SB
authors.lastname: Atla
mesh_terms: D001412:Bacillus subtilis / Q000737:chemistry; D005591:Chemical Fractionation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D055666:Lipopeptides / Q000737:chemistry*; D008628:Mercury / Q000302:isolation & purification*; D010456:Peptides, Cyclic / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D007477:Ions; D055666:Lipopeptides; D010456:Peptides, Cyclic; D013501:Surface-Active Agents; D008628:Mercury