阳离子聚丙烯酰胺改性膨润土对靛蓝的吸附性能

采用CPAM(阳离子聚丙烯酰胺)改性膨润土作为吸附材料,对靛蓝进行吸附研究,考察膨润土投加量、溶液的pH、反应温度、吸附时间及溶液初始ρ(靛蓝)对吸附效果的影响,并对膨润土的性能进行了表征. 结果表明,CPAM改性膨润土对靛蓝的去除率随着投加量的增加迅速增加,最佳投加量为3g/L,达到吸附平衡所需时间为40min. 当溶液pH为4.0~10.0时,CPAM改性膨润土均能保持较大吸附量,并且pH的变化对吸附量影响较小；当溶液pH大于10.0时,吸附量明显降低. CPAM改性膨润土对靛蓝的吸附动力学符合拟一级动力学方程,热力学符合Langmuir和Freundlich方程,回归系数均达0.99以上；pH为6.0时,最大吸附量为5287.0mg/g,是未改性膨润土吸附量的21.4倍,吸附性能比未改性膨润土有显著提高. 通过比表面积的测定及红外光谱和透射电子显微镜分析发现,CPAM与钠基膨润土土层中的阳离子发生离子交换反应,CPAM改性膨润土疏水性增强,层间结构发生变化,同时外比表面积增大,对有机染料的吸附作用增加,说明改性后的膨润土在结构和性能上明显优于未改性膨润土. 

Adsorption Properties of Cationic Polyacrylamide Modified Bentonite for Indigo Blue

Many kinds of treatment methods are used to deal with the dye wastewater, since it is difficult to be purified. The absorption processing technology is a common-used method. A cationic polyacrylamide (CPAM) modified bentonite was used as the sorbent to remove the indigo blue. The characteristics of the modified bentonite were investigated including the adsorbent dosage, pH, temperature, adsorption time and concentration of indigo blue. The results showed that the removal rate of indigo blue increased with the accretion of modified bentonite. The optimum dosage of CPAM bentonite was 3g/L and the sorption reached equilibrium after 40minutes. When the pH of solution ranged from 4.0to 10.0, the variation of the adsorption capacity of CPAM bentonite with varied pH was negligible, and the maximal adsorption capacity could be kept stable. However, when the pH was higher than 10.0, the adsorption capacity significantly decreased. The adsorption process followed with the pseudo-first-order kinetics. The isothermal data of sorption followed the Langmuir and Freundlich models with regression coefficients higher than 0.99. The maximum adsorption capacity of the sorbent was 5287.0mg/g at a pH of 6.0, which was 21.4times of the unmodified one. The measurement of specific surface area and the characterization of the CPAM modified bentonite by FTIR and TEM analysis suggested that the structure and properties of CPAM modified bentonite were superior to the unmodified one. The ion exchange reaction between cationic polyacrylamide and sodium base bentonite contributed much on the increase of hydrophobicity and outer specific surface area. The interlayer structure of modified bentonite was also changed during this process. These variations can effectively promote the adsorptive property of modified bentonite.