脲酶抑制剂对EICP防风固沙效果的影响研究

Effects Researches of Urease Inhibitor on Wind-breaking and Sand-fixation of EICP

植物源脲酶诱导碳酸钙沉积(EICP)的固化技术因其环境友好且经济高效,能够在荒漠风积沙表面形成固化层,起到防风固沙作用,逐渐被应用于土地荒漠化和沙化治理。然而,碳酸钙在土体表面的快速沉积,产生孔喉效应,使碳酸钙积淀在土体表面,造成固化深度浅、固化效果不均匀。为此,使用脲酶抑制剂延缓尿素水解,实现对碳酸钙沉淀生成速率的调控,进而优化土体表面固化效果,提高其防风固沙能力。结果表明,NBPT的添加能有效延缓尿素水解速率,降低初期碳酸钙的生成速率,但不影响碳酸钙最终生成量。NBPT的抑制效果与浓度、混合时间关系密切,浓度越高,混合时间越短,其抑制效果就越好。与未处理试样相比,无论是否添加NBPT,经EICP处理的试样抗风蚀性均明显提高。向EICP溶液中添加NBPT能有效改善土体固化层表面强度、厚度和碳酸钙分布,浓度为0.1 g/L固化效果最佳。SEM和XRD试验结果显示,添加NBPT后,碳酸钙晶体形貌多为球状和针簇状,而这种针簇状晶体之间的相互交织与嵌套可提高EICP固化效果。

The solidification technology of enzyme-induced carbonate precipitation(EICP)has been gradually applied to land desertification control because it is environmentally friendly and cost-effective. It can form a curing layer on the surface of desert aeolian sand for wind-breaking and sand-fixation. However,the rapid deposition of calcium carbonate on the soil surface produces a pore throat effect,making it to be accumulated on soil surface,causes shallow solidification depth and uneven solidification effect. To this end,the urease inhibitor was used to delay urea hydrolysis and control the formation rate of CaCO,to further optimize the surface solidification effect of soil and improve its ability of wind-breaking and sand-fixation. Results show that the addition of NBPT could effectively delay the hydrolysis rate of urea and reduce the initial formation rate of CaCO,but did not affect the final formation amount of CaCO. The inhibitory effect of NBPT was strongly related to concentration and mixing time. The higher the concentration,the shorter the mixing time was,the better the inhibitory effect would be. Compared with untreated samples,the wind erosion resistance of the samples treated by EICP was significantly improved whether NBPT was added or not. Adding NBPT to the EICP solution could effectively improve the surface strength,thickness,and calcium carbonate distribution of the soil curing layer. The solidification effect was the best when the concentration of NBPT was 0.1 g/L.SEM and XRD results show that with NBPT addition,the morphology of calcium carbonate crystals was mostly spherical and needle cluster,and the interweaving and nesting of needle cluster crystals could improve the solidification effect of EICP.