Cr(Ⅵ)生物吸附剂辣木籽的改性研究

Research on the modification of Moringaoleiferaseed for bio-adsorption of Cr(Ⅵ)

在前期研究中发现辣木籽具有吸附Cr(Ⅵ)的良好潜力,为进一步提高其Cr(Ⅵ)吸附容量,分别对辣木籽进行了酸、碱和热改性,并对改性条件下的典型样品进行了傅立叶红外光谱(FTIR)分析,探讨了产生吸附性能差异的原因。结果表明,酸改性均可不同程度提高辣木籽的Cr(Ⅵ)吸附性能,其中以硫酸改性辣木籽的吸附效果最好,其Cr(Ⅵ)去除率达到了81.9%,其后依次为磷酸、硝酸和盐酸;碱改性辣木籽的Cr(Ⅵ)吸附性能均比辣木籽原样差,且碱性越强对其吸附性能影响越大,可能由于强碱的存在使得辣木籽上的吸附活性基团消失;温度低于100℃的热改性对辣木籽的吸附性能基本不产生影响,干式热改性从100℃增加至140℃时,改性后辣木籽的Cr(Ⅵ)去除率持续增加,而超过140℃后辣木籽的活性基团被破坏,吸附性能下降;FTIR分析结果表明,辣木籽的吸附活性位主要是位于2 854、2 914cm-1的—CH2—官能团和1 754cm-1处的C=O官能团。

Moringa oleifera seed presented perfect potential for Cr（Ⅵ） adsorption in the preliminary study. In order to improve its Cr（Ⅵ） adsorption capacity,Moringa oleifera seed was modified by acid,alkali and heat treatment respectively,these modified Moringa oleifera seeds were characterized by Fourier transform infrared spectrometer （FTIR） to investigate the reason that caused different Cr（Ⅵ） adsorption capacity of different modified Moringa ole-ifera seeds. Results show that acid modification enhanced the Cr（Ⅵ） adsorption capacity to different degree,the per-formance of different acids followed the order of sulfuric acid〉phosphoric acid〉nitric acid〉hydrochloric acid. Sulfu-ric acid modified Moringa oleifera seed presented the best Cr（Ⅵ ） adsorption efficiency with the Cr（Ⅵ ） removal rate reached to 81.9%. The Cr（Ⅵ） adsorption capacity of alkali modified Moringa oleifera seed was worse than original samples, the negative effect was more significant under stronger alkalinity. Thermal modification had little effect on Cr（Ⅵ） adsorption capacity when the heating temperature below 100 ℃, while the adsorption capacity improved gradu-ally when dry-heating temperature increased to 140 ℃. Higher modification temperature （〉140 ℃ ） could destroy the active group on Moringa oleifera seed and further decrease its Cr（ Ⅵ ） adsorption capacity. The FTIR analysis showed that activity group of Moringa oleifera seed was -CH2-group located at 2 854,2 914 cm^-1 ,and C=O group located at 1 854 cm^-1.