低浓度酸碱改性竹质活性炭对甲醛吸附性能的研究

Study on Formaldehyde Adsorption Capability of Bamboo Activated Carbon Modified by Low Concentration Acid and Base

甲醛作为室内空气的主要污染物之一,对人类的健康造成极大的危害。能否有效去除甲醛已成为人们关注的热点,而吸附法被认为是一种去除甲醛的重要方法。本研究采用低浓度的硝酸、草酸、双氧水和氢氧化钠于常温下浸渍处理竹质活性炭,利用环境扫描电子显微镜(E-SEM)、比表面积分析仪(BET)、傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)对改性前后的活性炭形貌、孔隙特征和表面官能团进行表征,并运用静、动态甲醛检测分析装置评价改性后的竹质活性炭对甲醛的吸附效果。结果表明,与未处理竹质活性炭相比,四种改性处理的竹质活性炭样品表面都有不同程度的蚀刻和皱缩,微孔数量均有不同程度的增加,但氢氧化钠改性竹质活性炭平均孔径为1.89 nm,小于未处理竹质活性炭孔径。改性前后竹质活性炭的FTIR特征吸收峰的峰形没有明显变化,只是峰强有所差异;XPS结果表明改性后竹质活性炭的含氧量均有所增加;改性活性炭对甲醛的去除能力明显提高了,其中硝酸改性竹质活性炭性能最好,主要原因是硝酸改性活性炭表面羰基和酯基的协同作用增强,提高了活性炭的极性,有利于对极性甲醛分子的吸附。

Formaldehyde,as one of the main pollutants in indoor air,does great harm to human health.The effective removal of formaldehyde has brought a critical concern recently.The adsorption method is considered as an important method to eliminate formaldehyde.In this study,bamboo-based activated carbon was impregnated with low concentration nitric acid,oxalic acid,hydrogen peroxide and sodium hydroxide at room temperature.The morphology,pore characteristics and surface functional groups of the modified activated carbon were characterized by environmental scanning electron microscopy(E-SEM),specific surface area analyzer(BET),fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectrum(XPS).The static and dynamic formaldehyde analysis device was also applied to evaluate the adsorption effect of formaldehyde on modified bamboo activated carbon.The results showed that,compared with the untreated bamboo-based activated carbons,the surface of the four modified activated carbon were etched and shrunk to a different degree,and the microporous volumes increased.The average pore size of the activated carbon modified by sodium hydroxide was 1.89 nm,smaller than that of the untreated bamboo-based activated carbon.The FTIR characteristic peak shapes of activated carbon before and after modification had no obvious change,but the peak strength was affec-ted.The XPS showed that the content of oxygen atom of carboxyl groups with the modified activated carbon had increased.The removal capacity of formaldehyde was markedly improved with the modified activated carbon,among which the activated carbon modified by nitric acid was the best.The main reason was that the synergy of carbonyl groups and ester groups on the surface of the activated carbon modified by nitric acid increased,and the polarity of the activated carbon improved,which was conducive to the adsorption of polar formaldehyde molecules.