硅藻类粗多糖生物剂的制备及其对Cd2+的吸附性能

为了考察粗多糖对Cd2+的吸附性能，采用不同方法（稀酸法、稀碱法及超声-冻融-加热法）由海洋硅藻提取粗多糖，并进一步揭示硅藻粗多糖对Cd2+的吸附潜力.通过对比不同方法下粗多糖的组分质量分数（总糖、蛋白质和硫酸基）及其对Cd2+的吸附量，筛选出优质的粗多糖吸附材料，利用FTIR（傅里叶变换红外光谱）和SEM（扫描电镜）浅析粗多糖对Cd2+的吸附机制，采用吸附动力学和吸附等温模型详细探讨其对Cd2+的吸附特性.结果表明:①超声-冻融-加热法比稀酸法、稀碱法所提取的粗多糖的总糖质量分数高，分别为31.39%（480 nm）、26.74%（490 nm）；蛋白质杂质质量分数为7.09%，硫酸基质量分数为2.86%.②硅藻类细胞壁具有微孔结构，主要是由硅藻壳、多糖、蛋白质和脂肪组成，提取出的粗多糖表面均含有氨基、酰胺基、羰基、羟基等官能团，为其吸附重金属离子提供可能性.③超声-冻融-加热法在3倍体积乙醇沉淀时提取的粗多糖对Cd2+吸附量最大，为353.12 mg/g；该粗多糖对Cd2+的吸附更符合伪二级动力学模型，表明吸附过程有化学吸附参与；相比于Freundlich等温吸附模型，吸附数据更符合Langmuir等温吸附模型，表明该粗多糖对Cd2+的吸附主要为单层吸附.研究显示，利用超声-冻融-加热法提取出的硅藻粗多糖对Cd2+的吸附量为353.12 mg/g，是一种很有应用潜力的生物吸附材料. 

Preparation of Crude Polysaccharide Biological Agent from Diatom and Its Adsorption of Cadmium Ions

Crude polysaccharides were extracted from mixed marine diatoms by different methods using dilute acid, dilute alkali and ultrasonic-thawing-heating respectively, and adsorption capacities of Cd²⁺ by those crude polysaccharides were investigated to reveal potential use of marine diatom crude polysaccharides for Cd²⁺ removal from aqueous solution. The optimal crude polysaccharides adsorption material was screened by comparing components (total sugar, protein and sulfate), while Cd²⁺ adsorption capacities of crude polysaccharides using different extraction methods. Mechanism of Cd²⁺ adsorption by the crude polysaccharides was simply analyzed by FTIR and SEM. The adsorption properties of the crude polysaccharides were fully analyzed by adsorption kinetics and adsorption isotherms. Results suggested that:(1) The total sugar content using ultrasonic-thawing-heating was 31.39% (480 nm) and 26.74% (490 nm), which was higher than that by dilute acid and dilute alkali methods. The protein impurity content was 7.09%, and the sulfate group content was 2.86%. (2)The diatom cell wall possessed porous structure and composed of silica frustule, polysaccharides, protein and lipid. The surface of extracted crude polysaccharide contained amino amide, carbonyl and hydroxyl groups which is able to provide an adsorptive possibility of heavy metal ions. (3) The crude polysaccharide obtained by ultrasonic-thawing-heating with 3 times volume of ethanol precipitation possessed the highest adsorption capacity of Cd²⁺, 353.12 mg/g. The kinetic process of Cd²⁺ adsorption on the crude polysaccharides was well fitted by the pseudo-second-order model, suggesting involvement of chemical adsorption. The isothermal adsorption properties of Cd²⁺ adsorption on the crude polysaccharides could be better described by the Langmuir isothermal adsorption model than by Freundlich model, indicating that the adsorption process of Cd²⁺ is a monolayer adsorption process. The maximum adsorption capacity of the crude polysaccharides extracted by ultrasonic-thawing-heating was 353.12 mg/g. Therefore, the crude polysaccharides of marine diatom would be a great alternative adsorbent for Cd²⁺ removal from water.