Lanjuan Li

Displacement mechanism of binary competitive adsorption for aqueous divalent metal ions onto a novel IDA-chelating resin: isotherm and kinetic modeling.

Adsorptive properties for Cu (II), Pb (II) and Cd (II) onto an iminodiacetic acid (IDA) chelating resin were systematically investigated at the optimal pH-value in both single and binary solutions using batch experiments. The Langmuir isotherm model and the pseudo second-order rate equation could explain respectively the isotherm and kinetic experimental data for sole-component system with much satisfaction. The maximum adsorption capacity in single system for Cu (II), Pb (II) and Cd (II) was calculated to be 2.27 mmol/g, 1.27 mmol/g and 0.65 mmol/g individually. The initial adsorption rate followed the order as Cu (II)>Pb (II)>Cd (II) at the fixed initial concentration, and for each metal the initial sorption rate increased as the initial concentration increased. In addition, the modified Langmuir model could describe the binary competitive adsorption behavior successfully, with which the interaction coefficient was obtained to follow the order as Cu (II)<Pb (II)<Cd (II). Furthermore, in every case of the investigated three binary systems, the reduction in both the uptake amounts and distribution coefficients testified the antagonistic competitive phenomena. Obviously, this novel IDA-chelating resin possessed of a good selectivity toward Cu (II) over Pb (II) and Cd (II) for the obtained highest separation factor values were up to 21.30 and 133.91 in the range of tested. This interaction mechanism between the favorable component and other metal ions could mainly contribute to the direct displacement impact which be herewith illustrated schematically.

Adsorption of divalent heavy metal ions onto IDA-chelating resins: Simulation of physicochemical structures and elucidation of interaction mechanisms

The adsorption performances, under static as well as dynamic conditions, for such metal ions as Cu(II), Pb(II) and Cd(II) toward chelating resins (IRC748 and NDC702) similarly containing iminodiacetic acid group but diverse pore structures, are systematically performed and deeply exploited. The physicochemical characteristics of both IDA-chelating resins are thoroughly explored by EA, FT-IR, SEM-EDX and PSD. Langmuir isotherm and pseudo-second-order equation could satisfactorily describe the batch experimental data, based on which the equilibrium and kinetic parameters are calculated and compared. The adsorption capacities follow the order of Cu(II)>Pb(II)>Cd(II), due to the complicated impacts of metal ion electronegativity as well as resin pore textures. In the contrast of single and binary adsorption performances, more reduction of Cd(II) than Cu(II) is expectably investigated with the coexistence of competitive ion since the less affinity and hence weak competition of the former onto solid-phase. Using aqueous solution of 15 wt% HCl, nearly 100% recovery of Cu(II) and Cd(II) from IDA-resins could be strictly achieved in the column-tests. Furthermore, a schematic illustration of possible pore structure has been proposed and simulated. Meanwhile, the interaction mechanisms are thereby deduced and evidently confirmed by FT-IR as well as SEM analysis.

Insight into Highly Efficient Coremoval of Copper and p-Nitrophenol by a Newly Synthesized Polyamine Chelating Resin from Aqueous Media: Competition and Enhancement Effect upon Site Recognition

Highly efficient coremoval of Cu(II) and p-nitrophenol (PNP) was accomplished using a newly synthesized polyamine chelating resin (CEAD) as compared to three other commercial resins. The mutual effects and inner mechanisms of their adsorption onto CEAD were systematically investigated by binary, preloading, thermodynamic, and dynamic adsorption procedures. PNP was adsorbed onto both hydrophobic and hydrophilic sites, while Cu(II) only interacted with hydrophilic amine group sites. In both preloading and binary systems, the adsorption of PNP was inhibited to the same degree by the presence of Cu(II) because of selective recognition and direct competition. On the other hand, the presence of PNP obviously enhanced the adsorption of Cu(II) by more than 7%, which was related to PNP loading on the hydrophobic surface. As proved by structural characterization, hydroxyl groups facing outward create new sites for coordination with Cu(II). Moreover, ionic strength exerted some positive influence on the properties of CEAD. Finally, more than 98% of PNP and 99% of Cu(II) could be sequentially recovered with dilute NaClO3 and HCl. These superior properties demonstrated with CEAD indicate that it could be applied to wastewaters containing both heavy metals and PNP, even for high saline aqueous media.

Enhancement mechanisms behind exclusive removal and selective recovery of copper from salt solutions with an aminothiazole-functionalized adsorbent

The aminothiazole-functionalized adsorbent (CEAD) could exclusively remove and to selectively recover copper. The adsorption and separation properties of Cu(II) onto CEAD from aqueous media, with or without salts such as NaNO3, Ca(NO3)2 and Ni(NO3)2, were systematically compared by carrying out single, binary and multiple component static and dynamic experiments. In binary systems, the adsorption capacities of Cu(II) were obviously increased by 39.47%, 47.37% and 57.89% with Ni(NO3)2, NaNO3 and Ca(NO3)2, respectively. Besides, simulation study was performed to selectively recover Cu(II) from multi-component aqueous media, with the separation factor of only 54.91 in aqueous media without salts. The separation factor became infinite in the presence of NaNO3 and the enhancement ratio for Cu(II) was raised by 126.31%. Dynamic adsorption could separate Cu(II) and Ni(II) completely and the amount of effluent for pure Ni(II) increased to 127 BV with the help of NaNO3. In the predominant chelating mode simulated by density functional theory calculation, a metal ion coordinated with three nitrogen atoms and formed a chelating complex with two five-membered rings, and Cu(II) showed stronger coordinating ability than Ni(II) did. Meanwhile, anions exerted significant beneficial effects by electrostatic screening, and thus strengthened the exclusive removal and selective recovery of Cu(II).