化学工程

黄土在中国分布广泛，其水敏性强，但保水性能差，制约了干旱地区农业生产发展。为改善黄土的吸水和保水性能，以PDA(聚多巴胺)为增强材料，采用高效复合表面修饰方法，制备具有优异捕水和保水性能的PDA@LS改性黄土，并研究其微观特征、官能团分布、热质量损失特性、吸水性能和保水性能，对失水过程进行动力学分析，探讨改性黄土的捕水和保水机制。结果表明：盐酸多巴胺与空载黄土的质量比为1∶10时制备的改性黄土兼具低黏度和较好的流动性，饱和吸水量较空载黄土的0.275 7 g/g提升至0.474 2 g/g,开放环境下保水性能较空载黄土提升27.96%,并可多次进行水的解吸和复吸。动力学分析表明：PDA@LS改性黄土的恒温失水过程遵循Logarithmic模型，改性后的黄土中水分更易保持，有效水分扩散系数相比黄土降低56.02%,但易受温度的影响。PDA的改性极大改善了黄土吸水和保水性能，变黄土为“黑土”,对干旱地区土壤保水改良和水利用率的改善提供重要参考。

Loess is widely distributed in China, and it has strong water sensitivity but poor water retention performance, which restricts the agricultural production in arid areas. To improve the water uptake and retention performance of loess, the PDA@LS modified loess with excellent water capture and retention properties was prepared by using a high-efficiency composite surface modification of PDA(polydopamine). The microscopic characteristics, functional group distribution, thermal mass loss characteristics, water uptake and retention properties of modified loess were studied. The kinetics of the water loss process was analyzed to explore the water capture and retention mechanisms of modified loess. The results show that the modified loess exhibits low viscosity and good fluidity when the mass ratio of dopamine hydrochloride to loess is 1∶10. The saturated water absorption of modified loess increases from 0.275 7 g/g to 0.474 2 g/g, and its water retention property is improved by 27.96% compared to that of loess in an open environment. In addition, the modified loess is reusable in the cycles of water uptake and loss. Kinetic analysis indicates that the dehydration process of PDA@LS modified loess at a constant temperature follows logarithmic model. The modified loess is more prone to retain water, and its effective water diffusion coefficient is reduced by 56.02% compared to that of loess, but it is easily affected by temperature.This study significantly improves water uptake and retention performance of loess through PDA modification, effectively transforms loess into “black soil”, and provides an important reference for improving soil water retention and water use efficiency in arid areas.