Soaked Activated Coke Waste Ameliorates Saline-Alkali Soils via Selective Salt Ion Adsorption and Enhances Maize Growth
摘要
Activated coke waste (ACW), a byproduct of industrial desulfurization and denitrification, consists of fine particles (< 1 mm) with a porous structure, high specific surface area, and pH ~ 5, rendering it a candidate for saline-alkali soil remediation. However, its inherent excess salts and contaminants restrict direct agricultural application. In this study, ACW was treated with a dilute nitric acid solution to remove excess salts and contaminants, yielding the soaked activated coke waste (SACW) sample. The research systematically examined the adsorption properties and mechanisms of SACW for salt ion removal by solution experiment. Additionally, soil cultivation experiments were conducted to evaluate its potential in improving plant growth within saline-alkali soils. Compared to raw ACW, SACW exhibited reduced pH and electrical conductivity (EC), elevated oxygen-to-carbon (O/C) ratio, and expanded pore volume. SACW displayed ion adsorption selectivity in the order of SO₄2⁻ > Na⁺ > Cl⁻. Isothermal adsorption analysis revealed that Na⁺ and Cl⁻ adsorption aligned with the Langmuir model, whereas SO₄2⁻ adsorption adhered to the Freundlich model. Application of SACW (≥ 10 g kg⁻1) effectively improved saline-alkali soil properties by lowering pH and salinity, enhancing soil aggregate stability, and promoting nutrient utilization efficiency. Notably, SACW-treated soils supported maize plants with significantly increased height and biomass (13.94% and 159.28% higher, respectively; P ≤ 0.05) compared to untreated controls. These benefits stemmed from improved nutrient availability and reduced salt stress-induced plasma membrane damage. These findings validate SACW as a sustainable, functional amendment for reclaiming saline-alkali ecosystems and boosting crop productivity.