Blackburn Richard S
Green Chemistry Group, Centre for Technical Textiles, University of Leeds, Leeds, UK.
Environ Sci Technol. 2004 Sep 15;38(18):4905-9. doi: 10.1021/es049972n.
Dyeing effluent is one of the largest contributors to textile effluent and such colored wastewater has a seriously destructive impact on the environment. Adsorption can be a very effective treatment for decolorization of textile dyeing effluent, but current techniques employ adsorption chemistry that is not particularly environmentally friendly, such as the use of alum. In this study, natural polysaccharides were used as adsorbents for removal of dye molecules from effluent. The results showed that naturally cationic polysaccharides such as chitin and chitosan gave excellent levels of color removal, and this was attributed to a combination of electrostatic attraction, van der Waals forces, and hydrogen bonding. Nonionic galactomannans (locust bean gum, guar gum, cassia gum) were also highly effective in removing dye from effluent, whereas other nonionic polysaccharides, such as starch, were not effective. This was attributed to the structure of the polysaccharides and the relative degree of inter- and intramolecular interactions between separate polymer chains. The pendant galactose residues of galactomannans prevented strong interaction, allowing greater hydrogen bonding with dye; comparatively, starch has extensive chain interactions, and as such had limited potential for hydrogen bonding with the dye molecules at the temperature of application. In addition, hydrophobic interactions between the hydrophobic parts of the dye and the alpha-face of the pendant galactose residues may have contributed to the superior performance. Repulsion between anionic polysaccharides and the dye anions prevented any hydrogen bonding and as such pectin, carrageenans, and alginic acid were not effective in dye removal from effluent. The use of galactomannans derived from plants in this system presents a sustainable method of effluent treatment. The raw materials are derived from renewable plant sources and are available in tonnage quantities, the adsorption system itself is highly effective and does not involve any additional chemical input or treatment other than the use of the adsorbent, and the adsorption agents themselves are nontoxic and biodegradable.
印染废水是纺织废水的最大来源之一，这种有色废水对环境具有严重的破坏作用。吸附法可能是处理纺织印染废水脱色的一种非常有效的方法，但目前的技术采用的吸附化学方法并非特别环保，例如使用明矾。在本研究中，天然多糖被用作吸附剂以去除废水中的染料分子。结果表明，天然阳离子多糖如几丁质和壳聚糖具有出色的脱色效果，这归因于静电吸引、范德华力和氢键的共同作用。非离子半乳甘露聚糖（刺槐豆胶、瓜尔豆胶、决明胶）在去除废水中的染料方面也非常有效，而其他非离子多糖，如淀粉，则无效。这归因于多糖的结构以及单独聚合物链之间分子间和分子内相互作用的相对程度。半乳甘露聚糖的半乳糖残基侧链阻止了强烈的相互作用，从而允许与染料形成更多的氢键；相比之下，淀粉具有广泛的链间相互作用，因此在应用温度下与染料分子形成氢键的潜力有限。此外，染料的疏水部分与半乳糖残基侧链的α面之间的疏水相互作用可能有助于其卓越的性能。阴离子多糖与染料阴离子之间的排斥作用阻止了任何氢键的形成，因此果胶、卡拉胶和海藻酸在去除废水中的染料方面无效。在该系统中使用源自植物的半乳甘露聚糖提供了一种可持续的废水处理方法。原材料来自可再生植物资源且产量可观，吸附系统本身非常有效，除了使用吸附剂外不涉及任何额外的化学投入或处理，并且吸附剂本身无毒且可生物降解。
