title: Equilibrium, kinetic, and thermodynamic biosorption of Pb(II), Cr(III), and Cd(II) ions by dead anaerobic biomass from synthetic wastewater.
abstract: OBJECTIVE
  Heavy metals are toxic pollutants released into the environment as a result of different industrial activities. Biosorption of heavy metals from aqueous solutions is a new technology for the treatment of industrial wastewater. The aim of the present research is to highlight the basic biosorption theory to heavy metal removal.
  
  
  METHODS
  Heterogeneous cultures mostly dried anaerobic bacteria, yeast (fungi), and protozoa were used as low-cost material to remove metallic cations Pb(II), Cr(III), and Cd(II) from synthetic wastewater. Competitive biosorption of these metals was studied.
  
  
  RESULTS
  The main biosorption mechanisms were complexation and physical adsorption onto natural active functional groups. It is observed that biosorption of these metals was a surface process. The main functional groups involved in these processes were hydroxyl (-OH) and carboxylic groups (C=O) with 37, 52, and 31 and 21, 14, and 34 % removal of Pb(II), Cr(III), and Cd(II), respectively. Langmuir was the best model for a single system. While extended Langmuir was the best model for binary and ternary metal systems. The maximum uptake capacities were 54.92, 34.78, and 29.99 mg/g and pore diffusion coefficients were 7.23, 3.15, and 2.76 × 10(-11) m(2)/s for Pb(II), Cr(III), and Cd(II), respectively. Optimum pH was found to be 4. Pseudo-second-order was the best model to predict the kinetic process. Biosorption process was exothermic and physical in nature.
  
  
  CONCLUSIONS
  Pb(II) offers the strongest component that is able to displace Cr(III) and Cd(II) from their sites, while Cd(II) ions are the weakest adsorbed component.
authors.affiliation: Environmental Engineering Department, College of Engineering, University of Baghdad, 8856 Baghdad, Iraq. inas_abbas@yahoo.com
authors.forename: Abbas Hamid
authors.initials: AH
authors.lastname: Sulaymon
authors.forename: Shahlaa Esmail
authors.initials: SE
authors.lastname: Ebrahim
authors.forename: Mohanad Jasim
authors.initials: MJ
authors.lastname: Mohammed-Ridha
mesh_terms: D000327:Adsorption; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D018533:Biomass; D002104:Cadmium / Q000032:analysis / Q000378:metabolism; D002857:Chromium / Q000032:analysis / Q000378:metabolism; D007477:Ions / Q000032:analysis / Q000378:metabolism; D007700:Kinetics; D007854:Lead / Q000032:analysis / Q000378:metabolism; D019216:Metals, Heavy / Q000032:analysis / Q000378:metabolism*; D008956:Models, Chemical; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry* / Q000382:microbiology / Q000469:parasitology
chemical_list: D002104:Cadmium; D002857:Chromium; D007477:Ions; D007854:Lead; D019216:Metals, Heavy; D062065:Wastewater