Preparation Of Hyperbranched Polyamide-Amines Functional Materials And Their Adsorption For Heavy Metal Ions

With the rapid development of electroplating,metallurgy,mining industry and urbanization,a large number of waste-water containing heavy metal ions such as Pb,As,Ni,Cd,Cr,etc.are discharged into the aquatic,and most of these heavy metal ions are harmful to the environment.In recent years,there are many kinds of technologies for the treatment of sewage containing heavy metal ions.Among these technologies,the adsorption technology has the advantages of large adsorption capacity,fast adsorption speed,recyclable adsorbent,simple operation etc.,which is suitable for multi-component recovery and treatment,and it is an effective technology with popularization value.As the core of adsorption method,the design and development of adsorption materials are very important.Compared with many adsorption materials,hyperbranched polyamide-amines（H-PAMAMs）have attracted extensive attention from researchers because of its advantages of abundant surface functional groups,non-toxicity,easy preparation and modification,etc.However,they are not very suitable as adsorbent materials due to their solubility and difficulty in separation,which also limits their application in wastewater treatment.In order to compensate to some extent for the shortcomings of such materials,the synthesis and development of functionalized composites based on H-PAMAMs are becoming increasingly prominent in the direction of addressing heavy metal pollution.In this paper,two kinds of new hyperbranched polyamide-amines functional composites with simple synthesis process,low toxicity and environmental protection were prepared,and systematically explored the adsorption behavior of Pb²⁺,Cu²⁺,Hg²⁺in water bodies.The specific research contents are as follows:1.Hyperbranched polyamide-amines（H-PAMAMs）were synthesized via one-pot method,and then the H-PAMAMs were crosslinked by epichlorohydrin.Finally,the crosslinked hyperbranched polyamide-amines（C-H-PAMAMs）were prepared.The influences of solution p H value,initial concentration of Pb²⁺,dosage of adsorbents and coexistence of multi-metal ions on the adsorption performance were systematically investigated by C-H-PAMAMs,and the adsorption characteristics and mechanism of the C-H-PAMAMs for Pb²⁺were explored by FTIR,SEM,XPS,etc.The results of adsorption experiments indicated that the removal rate was highest at m（H-PAMAMs）:m（ECH）=13:7.The maximum adsorption capacity of the adsorbent for Pb²⁺was 180.83 mg/g at p H=4.0 and T=318 K,and the adsorption process of Pb²⁺on the C-H-PAMAMs was well described by the Langmuir and pseudo-second-order kinetic models.Thermodynamic analysis indicated that the adsorption could be defined as a spontaneous endothermic process.Four adsorption-desorption recycling tests showed that the the removal rate of Pb²⁺on C-H-PAMAMs decreased by only 2.55%.In the coexistence of multi-metal ions,C-H-PAMAMs had a high adsorption capacity and selectivity for Pb²⁺.The X-ray photoelectron spectroscopy（XPS）and FT-IR analysis showed that the adsorption mechanism of the C-H-PAMAMs for Pb²⁺was the synergistic chelation of-COO^-and-CO-NH-.2.The highly cross-linked hyperbranched polyamide-amines（H-PAMAMs）were prepared via one-pot methods,and then modified them with thiourea to synthesize a novel adsorbent（CHAP-SH）containing sulfhydryl groups.The adsorption behavior of CHAP-SH for Cu²⁺was systematically studied,and the adsorption characteristics and mechanism of CHAP-SH for Cu²⁺were explored by FT-IR,XPS,TGA,SEM-EDS,etc.The results of adsorption experiments indicated that the CHAP-SH had high adsorption capacity and selectivity for Cu²⁺.Under the conditions of p H=5.0 and T=45℃,the maximum adsorption capacity of Cu²⁺was 157.73 mg/g through the analysis of relevant model fitting data.The adsorption behavior of Cu²⁺on the CHAP-SH was more in line with Langmuir isotherm and pseudo-second-order kinetic models.XPS analysis indicated that the adsorption mechanism of the CHAP-SH for Cu²⁺was mainly the synergistic interaction with-NH,-COO^-,and-SH functional groups.Finally,after seven adsorption/desorption cycles,the removal rate of the adsorbent was still higher than91.25%,which means that the material has great potential in the treatment of wastewater containing Cu²⁺ions.3.The aforementioned sulfhydryl-functionalized novel cross-linked hyperbranched polyamide-amines composite（CHAP-SH）was used as an adsorbent and its adsorption characteristics and mechanism on Hg²⁺in water were systematically investigated.The results showed that CHAP-SH exhibited rapid performance in the removal of Hg²⁺,with a maximum adsorption capacity of 282.74 mg/g under optimum adsorption conditions.The whole adsorption behavior could be well adapted to the Langmuir,Redlich-Peterson isotherm and pseudo-second-order kinetic models,which reflected that the adsorption process was mainly monolayer chemisorption.Meanwhile,CHAP-SH had strong selectivity for Hg²⁺in the coexistence of multi-metal ions,and it still had excellent recoverability after five cycles.The interaction mechanism during adsorption process was further explored by XPS and FT-IR,and the results showed that the nitrogen-containing,oxygen-containing and sulfur-containing related groups in the adsorbent molecules had synergistic complexation with Hg²⁺.