title: New insight into adsorption characteristics and mechanisms of the biosorbent from waste activated sludge for heavy metals.
abstract: The adsorption characteristics and mechanisms of the biosorbent from waste activated sludge were investigated by adsorbing Pb(2+) and Zn(2+) in aqueous single-metal solutions. A pH value of the metal solutions at 6.0 was beneficial to the high adsorption quantity of the biosorbent. The optimal mass ratio of the biosorbent to metal ions was found to be 2. A higher adsorption quantity of the biosorbent was achieved by keeping the reaction temperature below 55°C. Response surface methodology was applied to optimize the biosorption processes, and the developed mathematical equations showed high determination coefficients (above 0.99 for both metal ions) and insignificant lack of fit (p=0.0838 and 0.0782 for Pb(2+) and Zn(2+), respectively). Atomic force microscopy analyses suggested that the metal elements were adsorbed onto the biosorbent surface via electrostatic interaction. X-ray photoelectron spectroscopy analyses indicated the presence of complexation (between -NH2, -CN and metal ions) and ion-exchange (between -COOH and metal ions). The adsorption mechanisms could be the combined action of electrostatic interaction, complexation and ion-exchange between functional groups and metal ions.
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Swette Center for Environmental Biotechnology, Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: zhiqiang@tongji.edu.cn.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: School of Civil Engineering and Transportation, Shanghai Technical College of Urban Management, Shanghai 200432, China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: siqingxia@tongji.edu.cn.
authors.forename: Siqing
authors.initials: S
authors.lastname: Xia
mesh_terms: D000327:Adsorption; D007700:Kinetics; D019216:Metals, Heavy / Q000737:chemistry*; D008956:Models, Chemical; D012722:Sewage / Q000737:chemistry*; D013696:Temperature
chemical_list: D019216:Metals, Heavy; D012722:Sewage
keywords: Adsorption; Biosorbent; Metal ions; Response surface methodology (RSM); Waste activated sludge