| Heavy metals, such as copper, zinc and nickel, are highly toxic and non-biodegradable which are characterized as universality, complexity, persistence and so on. The traditional technologies usually come with drawbacks of low disposal efficiency, high production cost, complicated operation and secondary pollution. Meanwhile, the coexisting salt further improve the difficulty for advanced treatment. Thus, it is of great importance to explore new techniques to effectively remove and recovery heavy metal ions.As an alternative for heavy metal pollution remediation, chelate adsorption which is represented by polyamine chelating adsorbents have been attracting wide interests due to its high removal efficiency and selectivity, superior salt tolerance and easy regeneration. The adsorption and separation behavior of heavy metal ions onto series of polyamine chelating resins with or without salt were comparably explored by carrying out the sole-/binary-/multiple-component static, kinetic and dynamic experiments, and the micro-interface interaction mechanisms as well as the principle of enhanced removal in saline systems could be explained. The project would lead to the theoretical and technical guidance for the innovative design methods of chelating resin and the harmlessization and resourceization treatment technique for heavy metals ions.In this article, polyamine was introduced to methacrylate-divinyl benzene copolymer in order to get series of high-capacity amine chelating resins (PAMB, PAMC, PAMD). Characterization of resins involving EA, FTIR, PSD, SEM and XPS, proved all the resins could be prepared with much success. The nitrogen content of the resins was 18.97%～20.83%。In single systems, the adsorption capacity increased with the optimum pH for Cu(II), Zn(II) and Ni(II), and the adsorption isotherms could be described well by Langmuir model with the equilibrium capacity of 1.97 mmol/g,1.49 mmol/g,1.44 mmol/g at the optimum pH value of 3, which was 43.79%,64.43%,65.51 higher than commercial polyamine resin S984. The adsorption processes were endothermic and spontaneous impelled by entropy. The binary adsorption isotherms were studied for different systems and could be well fitted to the Extended Langmuir model with the selective order of Cu(Ⅱ)>Zn(Ⅱ>Ni(Ⅱ. In Cu(Ⅱ)/Ni(Ⅱ systems, the separation factor could be up to 1177.13. The kinetic data could be well fitted by Lagergren-second-order equation and the adsorption rate followed the order of Cu(Ⅱ)>Zn(Ⅱ)>Ni(Ⅱ. The adsorption rate of Cu(H) was increased in binary systems while the adsorption capacity of Ni(Ⅱ) 53.20%. In dynamic adsorption, the effluent points were 92 BV and 4 BV for Cu(Ⅱ and Ni(Ⅱ) in single system, which changed to 120 BV and 1 BV in binary system. The FTIR and XPS spectra before and after interaction with metals demonstrated that the nitrogen was associated with the coordination and the selectivity was related to the character of heavy metal ions. The most stable configuration was calculated by DFT in which heavy metal ions interact with one-NH2 and two-NH-to form a stable penta cyclic compound. So, Cu(Ⅱ as the favorable component in the solution owned the largest adsorption capacity and the selective property.In multi component systems with salt, NaNO3 could increased the adsorption capacity of PAMD towards Cu(Ⅱ, Zn(Ⅱ) and Ni(Ⅱ) with the largest enhancement ratio of 70.42%,75.51% and 38.46%. In Cu(Ⅱ/Ni(Ⅱ)/NaNO3 systems, the adsorption capacity of Cu(Ⅱ increased by 87.67%while Ni(Ⅱ) decreased by 99.63% in 1500 mmol/L NaNO3 solution and the selective separation ratio increased to be infinite. The kinetic data of Cu(II) could be well fitted by Lagergren-second-order equation and the adsorption rate improved with the concentration of coexisting NaNO3. Due to the inhibiting effect, the adsorption behavior of Ni(Ⅱ could not be well fitted by any model. In 1500 mmol/L NaNO3 solution, the effluent points of Cu(Ⅱ) delayed to 172 BV and the saturation point of Ni(Ⅱ) was advanced to 52 BV, implying the more efficient separation property of PAMD in salt solutions. Electrostatic shielding effect coming from anions, Compressed double electric layer theory and Molar exchange theory could successfully explain the nature of salt enhancement from the ionic and molecular level.PAMD could selectively remove trace heavy metal ions from complex solutions and also could effectively purificate the high-saline wastewater containing various heavy metal ions. On one hand, PAMD could selectively remove Cu(Ⅱ) from high concentration Ni(Ⅱ) solutions with the purity nickel(>99.99%) volume of 1200 BVwith the running cost only 5.67 yuan per ton and 78800 yuan could be earned in each cycle. On the other hand, the high-saline wastewater from Zhejiang Xinshidai Company could be well treated by PAMD for 330 BV clean effluent with the running cost only 12.84 yuan per ton, which provides references for renovations of selective removal and effictive recovery heavy metal ions from wastewater. |
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