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

地球上有相当大的面积被所谓的受损土壤所覆盖，特别是酸性土壤，植物的生长通常受到限制。这部分是由于该地区土壤水pH值较低，但主要是由于土壤水中铝离子浓度较高。我们一直致力于以工业木质素为原料，通过部分氧化法开发新的土壤调节剂，并报道了部分氧化木质素对植物铝毒性的有效去除。本文研究了碱氧级废液中木质素碎片的化学特性及其对铝的毒性作用。结果表明，木质素片段整体及其高分子量部分对铝毒性的迁移具有积极作用，而低分子量部分则表现出不同的迁移行为。在较低剂量下，草酸含量较高的部分对铝毒性的去除有积极作用，但随着剂量的增加，对铝毒性的去除有明显的消极作用。这种行为可以用草酸与铝离子之间的配合物来解释，并通过27AL-NMR证实了这一点。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.