改性菠萝皮对水中亚甲基蓝的吸附性能研究

Study on Adsorption Performance of Modified Pineapple Peel for Methylene Blue in Water

以农业废弃物菠萝皮为原料,使用柠檬酸对菠萝皮粉末分别进行超声波改性和热改性,探究了改性菠萝皮对亚甲基蓝的去除效果。通过扫描电子显微镜(SEM)和傅里叶变换红外光谱(FTIR)对改性前后菠萝皮孔隙和表面结构进行表征,同时考察了改性前后菠萝皮的投加量、pH值、反应时间和染料质量浓度对吸附亚甲基蓝的影响。结果表明:经过柠檬酸改性后的菠萝皮表面引入了羧基官能团,对亚甲基蓝的吸附效果显著增加。在吸附剂用量为1.2 g·L^(-1)、起始p H为6.52、改性时间90 min、起始质量浓度为100 mg·L^(-1)的条件下,柠檬酸超声波改性菠萝皮(PA-US)和柠檬酸热改性菠萝皮(PA-TM)对亚甲基蓝的去除率分别可以达到65%、98%。吸附等温线的研究表明,PA-US和PA-TM吸附过程均符合Langmuir等温模型,说明该吸附过程为单分子层吸附,且对亚甲基蓝的最大吸附量分别为56.05 mg·g^(-1)和333.33 mg·g^(-1),与未改性菠萝皮(PA)的最大吸附量相比,分别提高了1.39、8.08倍。吸附动力学研究表明,PA-US和PA-TM对亚甲基蓝的吸附均符合准二级动力学方程模型。由吸附等温线和动力学模型结果可以推断该吸附过程属于化学吸附。

Using agricultural waste pineapple peel as raw material,pineapple peel powder was modified by ultrasonic wave and thermal wave respectively with citric acid,and the removal effect of methylene blue by modified pineapple peel was explored.The pore and surface structures of pineapple peels before and after modification were characterized by scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FTIR),and the effects of dosage,pH,reaction time and dye mass concentration on the adsorption of methylene blue were also investigated before and after modification.The experimental results showed that carboxyl functional groups were introduced on the surface of pineapple peel modified with citric acid,and the adsorption effect on methylene blue was significantly increased.The removal of methylene blue by citric acid ultrasonically modified pineapple peel(PA-US) and citric acid thermally modified pineapple peel(PA-TM) could reach 65% and 98% under the conditions of adsorbent dosage of 1.2 g·L^(-1),starting pH of 6.52,modification time of 90 min,and starting concentration of 100 mg·L^(-1),respectively.The adsorption isotherm studies showed that both PA-US and PA-TM conformed to the Langmuir isotherm model,indicating that the adsorption process was monomolecular layer adsorption,and the maximum adsorption of methylene blue was 56.05mglu^(-1) and 333.33 mg·g^(-1),which were 1.39 times and 8.08 times higher compared with that of the maximum adsorption of unmodified pineapple peel(PA),respectively.The adsorption kinetic studies showed that the adsorption of methylene blue by both PA-US and PA-TM conformed to the quasi-secondary kinetic equation model.From the adsorption isotherms and kinetic modeling results,it was inferred that the adsorption process belonged to chemisorption.