title: Chelating stability of an amphoteric chelating polymer flocculant with Cu(II), Pb(II), Cd(II), and Ni(II).
abstract: The absorption spectra of Cu(2+), Pb(2+), Cd(2+), and Ni(2+) chelates of an amphoteric chelating polymer flocculant (ACPF) were measured by ultraviolet spectrophotometry, and their compositions and stability constants (β) were calculated. ACPF exhibited three apparent absorption peaks at 204, 251, and 285 nm. The CSS(-) group of ACPF reacted with Cu(2+), Ni(2+), Pb(2+), and Cd(2+) to form ACPF-Cu(2+), ACPF-Ni(2+), ACPF-Pb(2+), and ACPF-Cd(2+) chelates, respectively, according to a molar ratio of 2:1. The maximum absorption peaks of ACPF-Cu(2+), ACPF-Ni(2+), ACPF-Pb(2+), and ACPF-Cd(2+) appeared at 319, 326, 310, and 313.5 nm, respectively. The maximum absorption peaks of the chelates showed significant red shifting compared with the absorption peaks of ACPF. The β values of the ACPF-Cu(2+), ACPF-Pb(2+), ACPF-Cd(2+), and ACPF-Ni(2+) chelates were (1.37±0.35)×10(12), (3.26±0.39)×10(11), (2.05±0.27)×10(11), and (3.04±0.45)×10(10), respectively. The leaching rate of heavy metal ions from the chelating precipitates decreased with increasing pH. ACPF-Cu(2+), ACPF-Ni(2+), ACPF-Pb(2+), and ACPF-Cd(2+) were very stable at pH≥5.6. Cu(2+), Ni(2+), Pb(2+), and Cd(2+) concentrations in the leaching liquors were lower than the corresponding limits specified by the Integrated Wastewater Discharge Standard of China.
authors.affiliation: Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education and Hunan Province, Hunan Province College Key Laboratory of QSAR/QSPR, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201, PR China. Electronic address: llh213@163.com.
authors.forename: Lihua
authors.initials: L
authors.lastname: Liu
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Li
authors.forename: Xing
authors.initials: X
authors.lastname: Liu
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Zhou
authors.forename: Yulin
authors.initials: Y
authors.lastname: Ling
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002614:Chelating Agents; D011108:Polymers; D002104:Cadmium; D007854:Lead; D003300:Copper; D009532:Nickel
keywords: Amphoteric chelating polymer flocculant; Heavy metal ions; Leaching-out characteristics; Stability constant; Ultraviolet spectrophotometric method