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 Mg 2+ -intercalated vermiculite (VMT) and Al 2 (SO 4 ) 3 into the sodic soil, detailed quasi-in-situ X-ray diffraction and transmission electron microscope demonstrated the mineralization process. The free OH – , CO 3 2– and Cl – can be in-situ super-stable mineralized into MgAl-layered double hydroxide (MgAl-LDH). The CO 3 2– and Cl – were confined in the interlayer of MgAl-LDH, while OH – reacted with Mg 2+ and Al 3+ to form the laminate of MgAl-LDH. At the same time, due to slow release of Mg 2+ 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 Al 2 (SO 4 ) 3 for 150 days, the soil pH decreased from 10.18 to 7.47, while the contents of soluble Na + and CO 3 2– reduced significantly. Moreover, seedling emergence rate of corn and cabbage plants after application of VMT and Al 2 (SO 4 ) 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. After adding Mg 2+ -intercalated VMT and Al 2 (SO 4 ) 3 into sodic soil, the free OH – , and CO 3 2– can be in-situ super-stable mineralized to form the corresponding MgAl-LDH, and the Na + can fill the cationic vacancy of VMT due to slow release of Mg 2+ . After 150 days of treatment, the pH value of soil decreased from 10.18 to 7.47, and EC, soluble Na + , CO 3 2– content, and bulk density reduced significantly. • Addition of VMT and Al 2 (SO 4 ) 3 to sodic soil resulted in the formation of MgAl-LDH/VMT. • The CO 3 2– were confined into the interlayer of MgAl-LDH. • The OH – got involved into the MgAl-LDH laminate. • Slow release of Mg 2+ from VMT led to the formation of cationic vacancy, which can be filled by Na + . • The neighboring-charge restriction effect resulted in the decrease of the pH and EC significantly.