聚丙烯酸修饰蛭石及其对水中Cr(VI)的吸附性能

Polyacrylic Acid-Modified Vermiculite and Its Adsorption Performance for Cr(VI) in Aqueous Solution

摘要: 本研究以丙烯酸为单体，偶氮二异丁腈(AIBN)为引发剂合成线性聚丙烯酸(PAA)，再经硫酸铝催化实现PAA在蛭石(VMT)表面的有效接枝，制备出新型聚丙烯酸/蛭石复合吸附剂(VMT-PAA)。通过XRD与FT-IR表征证实PAA成功接枝于蛭石表面及层间，且未破坏蛭石的晶体结构；BET测试表明VMT-PAA的比表面积1.16 m²/g，总孔容0.0086 cm³/g，平均孔径23.66 nm，适宜的孔结构有利于离子传输。吸附实验显示VMT-PAA对Cr(VI)的吸附性能显著优于未改性蛭石，在吸附时间为240 min，投加量为1.3 g/15 mL模拟废水下，去除率最佳。动力学拟合结果表明VMT-PAA吸附过程更符合伪二阶动力学模型(R² > 0.99)，远优于伪一阶模型，PAA接枝引入了大量羧基，从而显著提升了对Cr(VI)的吸附性能。本研究为开发高效、低成本的Cr(VI)废水处理材料提供了理论依据和技术支持。

Abstract: This study involved synthesising linear polyacrylic acid (PAA) using acrylic acid as the monomer and azobisisobutyronitrile (AIBN) as the initiator. Through aluminium sulphate catalysis, the PAA was effectively grafted onto the surface of vermiculite (VMT) in order to produce a new polyacrylic acid/vermiculite composite adsorbent (VMT-PAA). XRD and FT-IR analyses confirmed that the PAA had been successfully grafted onto the surface and interlayers of the vermiculite without damaging its crystal structure. BET analysis revealed that the VMT-PAA composite has a specific surface area of 1.16 m²/g, a total pore volume of 0.0086 cm³/g and an average pore diameter of 23.66 nm, indicating a pore structure that is favourable for ion transport. Adsorption experiments revealed that VMT-PAA exhibited significantly superior adsorption performance for Cr(VI) compared to unmodified vermiculite, achieving optimal removal efficiency at an adsorption time of 240 minutes and a dosage of 1.3 g/15 mL of simulated wastewater. Kinetic fitting results indicated that VMT-PAA ad-sorption better conformed to the pseudo-second-order kinetic model (R² > 0.99), outperforming the pseudo-first-order model by a large margin. The grafting of PAA introduced a large number of carboxyl groups, significantly enhancing the adsorption performance for Cr(VI). This study provides a theoretical foundation and technical support for the development of efficient, low-cost materials for the treatment of Cr(VI)-contaminated wastewater.