Utilization of Alkaline-oxygen Delignification Stage Waste Liquor for the Removal of Aluminum Toxicity to Plant Growth

地球上相当大的面积被所谓的受损土壤，特别是酸性土壤所覆盖，植物的生长通常受到限制。这部分是由于这些地区土壤水的pH值低，但主要是由于土壤水中的高铝离子浓度。我们一直致力于开发新的土壤调理剂从工业木质素的部分氧化，并已报道，部分氧化木质素是相当有效的，以消除铝毒害植物。本研究对碱氧段废液中木质素碎片的化学特征及其对铝毒的作用进行了研究。结果表明，木质素碎片整体及其高分子量组分对铝毒具有迁移作用，而低分子量组分则表现出不同的迁移行为。草酸含量高的组分在较低的投加量下对铝毒的去除效果较好，但随着投加量的增加，草酸含量高的组分对铝毒的去除效果较差。27 AL-NMR谱证实了草酸与铝离子形成络合物的行为。游离草酸本身对植物生长是有毒的。

Quite a large area on the earth is covered by the so-called damaged soil, particularly by acid soil, on which plant growth is generally limited. This is partly due the low pH of soil water in those area, but is mainly due to the high aluminum ion concentration in the soil water. We have been working to develop the new soil conditioning agents from industrial lignins by a partial oxidation and have reported that the partially oxidized lignin is quite effective to remove aluminum toxicity to plant. In this study, chemical characteristics of lignin fragments in the alkaline-oxygen stage waste liquor and their functions to aluminum toxicity were carefully investigated. It was found that the lignin fragments as a whole and its high molecular weight fraction showed the positive effect to move aluminum toxicity, but the lower molecular weight fractions showed different behaviors dependent on the molecular weight. A fraction containing a lot of oxalic acid showed positive effect in the case of a lower dosage, but with an increased dosage it showed a clear negative effect for the removal of aluminum toxicity. This behavior can be explained by the complex formation between oxalic acid and aluminum ion which was confirmed by 27AL-NMR spectroscopy. Free oxalic acid itself is toxic to the plant growth.