聚（丙烯酸-板栗壳色素）高吸水树脂控制合成及其在重金属污染土壤树木修复中的应用基础研究

Heavy metal-contaminated soil remediation is a major science and technology requirement in China. Dendroremediation which combines energy forest with ecological engineering is not involved directly in people’s food chain and has economic, ecological and social benefits. However, newly planted seedlings in dendroremediation in arid, semi-arid, seasonal arid areas suffer the stresses of the drought the heavy metals, being bad for their survival and growth. Chestnut shell pigment a natural melanin from the waste biomass. It shows strong binding ability towards heavy metals. The applicant has synthesized multifunctional poly(acrylic acid/chestnut shell pigment) superabsorbent in a pre-research. This project proposes to improve its performances for heavy-metal adsorption and water absorption by controlling synthesis. It will be applied in analog soils contaminated with simulation a heavy metal such as Cu, Pb, Cd, and Cr. The effect of the application on the soil properties in the aspects of physics, chemistry, and biology will be tested. Caragana korshinskii and Robinia pseudoacacia are selected as tree species for bioassays to illustrate the influence of the application on the seed germination. The physiological mechanisms will be clarified, and the feasibility of using the superabsorbent in dendroremediation of heavy metal-contaminated soils will be checked preliminarily. The experimental data and theories will guide the production and application of the superabsorbent.

重金属污染土壤修复是我国重大科技需求。结合能源林生态工程的树木修复法不与人类食物链直接相连，兼具经济、生态、社会三大效益。然而，在干旱、半干旱、季节性干旱区采用树木修复时，新植苗木受到干旱和重金属的双重胁迫，影响成活和生长。板栗壳色素是来自于废弃生物质的天然黑色素，具有很强的重金属结合能力。申请人预研合成了具有强吸附重金属性和吸水性的聚（丙烯酸-板栗壳色素）多功能高吸水树脂。本项目拟通过控制合成进一步提高该树脂吸附重金属和吸水性能，研究其施用对模拟Cu、Pb、Cd、Cr重金属污染土壤理化生物性质的影响，以柠条和刺槐为生物检测树种，研究其对林木种子萌发的影响，剖析其作用机制，从而初步判断聚（丙烯酸-板栗壳色素）高吸水性树脂应用于重金属污染土壤树木修复的可行性，为其生产应用提供试验数据和理论指导。

干旱、半干旱、季节性干旱区重金属污染土壤树木修复面临干旱和重金属毒害双重困难，施用具有保水功能的重金属钝化剂是解决这一问题的重要途径。本研究以来自林产加工剩余物的板栗壳的具有很强重金属结合能力的黑色素为交联剂合成新型聚丙烯酸类多功能高吸水树脂。优化合成条件为：板栗壳色素浓度为 2.709 %（w/w以丙烯酸为基，下同）；过硫酸铵20.93 %；NaOH 10.39 %；水9.75 （w/w）；反应温度为80℃。最高吸纯水倍率 852.4 g/g，生理盐水83.33 g/g。与传统聚丙烯酸高吸水树脂相比，板栗壳色素为交联剂降低了生产成本和对石油的依赖性，提高了树脂的生物可降解性，所合成树脂很强的结合水分子和吸附重金属双重能力。由板栗壳色素各分级组分合成的高吸水树脂在吸水和吸附重金属能力方面较总板栗壳色素合成的树脂没有显著提高，没有必要对板栗壳色素进行进一步分级。合成的树脂呈规则的多孔状，吸水再脱水后发生孔变形，导致吸水能力显著下降，反复利用性能不佳。来自丙烯酸的羧基和来自板栗壳色素的羧基、羟基和氨基是水和重金属的结合位点，大部分水在树脂中以游离态或半游离态存在。该树脂主要通过离子交换或络合的化学方式吸附重金属离子，为单层吸附。一定剂量的合成的聚（丙烯酸-板栗壳色素）树脂可以缓解Cu和Cd等重金属对植物的毒害，提高种子发芽率。这种缓解作用涉及恢复和提高种子储藏物质转化酶活力，并能降低有重金属诱导的SOD应激反应。