title: Adsorption characteristics of Ni(II) onto MA-DTPA/PVDF chelating membrane.
abstract: The melamine-diethylenetriaminepentaacetic acid/polyvinylidene fluoride (MA-DTPA/PVDF) chelating membrane bearing polyaminecarboxylate groups was prepared for the removal of Ni(II) from wastewater effluents. The membrane was characterized by SEM, (13)C NMR and FTIR techniques. Quantitative adsorption experiments were performed in view of pH, contact time, temperature, the presence of Ca(II) and lactic acid as the controlling parameters. Adsorption kinetics and equilibrium were examined regarding the single Ni(II) system, binary Ni(II) and Ca(II) system and nickel-lactic acid complexes system. The desorption efficiency was also evaluated, and the adsorption mechanism was suggested based on experimental data. The results show that the sorption kinetics fit well to Lagergren second-order equation and the isotherms can be well described by Langmuir model. At 298 K, the second-order rate constant is calculated to be 4.171, 11.39, 6.203 cm(2)/(mg min) and the equilibrium uptake is 0.0264, 0.0211 and 0.0216 mg/cm(2) in the aforementioned three systems. The distribution coefficient of Ni(II) slowly decreases from 4.27 to 2.72, and the separation factor (f(Ni(II)/Ca(II))) increases from 3.10 to 8.46 when the initial Ca(II) concentration varies from 20 to 200mg/L. This reveals the chelating membrane shows more affinity for Ni(II) than Ca(II) ions. In the studied range of lactic acid concentration, Ni(II) uptake decreases with the maximum ratio of 10%. Chemical bonding (chelation) dominates in the adsorption process, and the negative ΔG° and ΔH° indicate the spontaneous and exothermic nature of adsorption.
authors.affiliation: Department of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Zhao
authors.forename: Laizhou
authors.initials: L
authors.lastname: Song
authors.forename: Jie
authors.initials: J
authors.lastname: Fu
authors.forename: Pei
authors.initials: P
authors.lastname: Tang
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D002614:Chelating Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning / Q000379:methods; D009532:Nickel / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D004369:Pentetic Acid / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D005465:Fluorocarbon Polymers
chemical_list: D002614:Chelating Agents; D019344:Lactic Acid; D008567:Membranes, Artificial; D009532:Nickel; D009930:Organic Chemicals; D004369:Pentetic Acid; D011145:Polyvinyls; C024865:polyvinylidene fluoride; D005465:Fluorocarbon Polymers