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

Abstract

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 CO₃^2– 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 CO₃^2– 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.