Effect of vermiculite on in-situ super-stable mineralization and amelioration on sodic soil

As a non-traditional cultivated land resource that can be reformed, sodic soil after amelioration can be effectively utilized to alleviate the food crisis. It is crucial to develop a new strategy that is efficient, cost-effective, and environmentally friendly for sodic soil remediation. Vermiculite features a high cation exchange capacity and porous structure. By adding Mg2+-intercalated vermiculite (VMT) and Al2(SO4)3 into the sodic soil, detailed quasi-in-situ X-ray diffraction and transmission electron microscope demonstrated the mineralization process. The free OH-, CO3 2- and Cl- can be in-situ super-stable mineralized into MgAl-layered double hydroxide (MgAl-LDH). The CO32- and Cl- were confined in the interlayer of MgAl-LDH, while OH- reacted with Mg2+ and Al3+ to form the laminate of MgAl-LDH. At the same time, due to slow release of Mg2+ from VMT, the cationic vacancy can be formed, which can be filled by large amounts of soluble Na+ in sodic soil in order to balance the charge. Sodic soil amelioration experiments illustrated that after remediating sodic soil with 2.0 wt% (weight percentage) VMT and Al2(SO4)3 for 150 days, the soil pH decreased from 10.18 to 7.47, while the contents of soluble Na+ and CO32- reduced significantly. Moreover, seedling emergence rate of corn and cabbage plants after application of VMT and Al2(SO4)3 of sodic soil increased from 6.3% to 87.5% and 2.5% to 84.1%, respectively. Compared to traditional methods, this method reduced water usage and offered advantages including high mineralization capacity, excellent stability, and fast rate. This work provides deep insight into in-situ super-stable mineralization for sodic soil amelioration using VMT.