Preparation of a modified flue gas desulphurization residue and its effect on pot sorghum growth and acidic soil amelioration

Mineral soil conditioner requirement and ability to adjust soil acidity

Mineral soil conditioners (MSCs) are used to regulate soil acidity and improve soil quality; they are often made in sintering potassium feldspar, limestone, or dolomite, and are alkaline materials rich in silicon, calcium, potassium, and magnesium. The key point of how to apply them into farmlands is their ability to adjust soil acidity and the MSCs requirement (MSC_R). In this study, inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis and X-ray diffraction (XRD) were firstly used to determine the elemental and phase compositions of the MSCs in order to establish its equivalent relationship for the depletion of soil activity (H⁺) and its conversion relationship with CaCO₃. Secondly, the soil culture method and the improved Shoemaker Mclean Peatt–Double Buffer (SMP–DB) method were compared using a group of 14 typical acid soils in MSC_R. It is investigated that the MSCs contained four alkali/alkaline earth–metal elements: Ca, Mg, K, and Na in the bound aluminosilicate form (Ca₂MgAlSi₂O₇, Ca₃(SiO₃)₃, KAlSiO₄, and KAlSi₂O₆); and the depletion of 2.31 mol of H⁺ required 100 g of MSCs and the amount of Si–Ca–K–Mg MSC needed to deplete the same quantity of H⁺ was only 0.87 times that of CaCO₃. Based on the calculations by using the SMP-DB method and the soil culture method, the MSC_R for treating the 14 typical acid soils were in the range of 0.56–8.27 t hm⁻² and 0–10.8 t hm⁻², respectively. Data from both methods were highly correlated with each other and there was a good linear correlation between them, and the equation: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{MSC}_{R}}^{{\prime}}=30.29d-0.77$$\end{document}MSCR′=30.29d-0.77 could be used to calculate the MSCs requirement. The recommended MSC_R was approximately 4–8, 2–6, and 1–3 t hm⁻² when soil pH < 4.50, 4.50 < pH < 5.50, and pH > 5.50, respectively. The experimental and computational methods established in this study could serve as the scientific basis and theoretical guidance for the production and agricultural use of MSCs.

Improvement of nitrogen utilization and soil properties by addition of a mineral soil conditioner: mechanism and performance

A mineral soil conditioner (MSC) composed of activated potash feldspar, gypsum, and calcium carbonate and containing an amount of available mineral nutrients, is shown to be effective for plant growth and acidic soil amelioration. In this study, a field test was conducted over four rice seasons by examining treatment with control check (CK), MSC, biological active carbon, and lime to investigate the nitrogen-use efficiency and mechanism of soil characteristic variations due to the desilicification and allitization of soil as well as the unrestrained use of nitrogen (N) fertilizer in recent years. Influences of MSC on the xylem sap intensity and mean rice yields were evaluated, and the soil type was also analyzed using the FactSage 6.1 Reaction, phase diagram, and Equilib modules. The results of the field trial showed that MSC application increased the xylem sap intensity and nitrogen export intensity by 37.33-39.85% and 31.40-51.20%, respectively. A significant increase (5.63-15.48%) in mean grain yields was achieved with MSC application over that with biological active carbon and lime application. The effects of MSC had a tendency to increase with time in the field experiment results, and grain yields increased after the initial application. The new formation of clay minerals exhibits a significant influence on [Formula: see text] fixation, especially for 2:1 phyllosilicates with illite, owing to the interlayers of the clay minerals. Our preliminary results showed that kaolinite, the main 1:1 phyllosilicate clay mineral in ferralsol, transformed to illite at room temperature as a consequence of the presence of H₄SiO₄ and available K⁺ supplied by MSC. This indicated that improving the soil quality combined with reducing N losses from soils is an efficient way to control non-point source pollution from agriculture without the risk of decreased in grain yield.

Removal of Cd(ii) and Pb(ii) ions from natural water using a low-cost synthetic mineral: behavior and mechanisms

A low-cost synthetic mineral (LCSM) was prepared by mechanochemical treatment of a solid-state mixture containing potassium feldspar, wollastonite, gypsum, limestone and dolomite powder at a molar ration of 1 : 1 : 1 : 6 : 3 and hydration process.

Influence of Flue Gas Desulfurization Gypsum Amendments on Heavy Metal Distribution in Reclaimed Sodic Soils

Although flue gas desulfurization (FGD) gypsum has become an effective soil amendment for sodic soil reclamation, it carries extra heavy metal contamination into the soil environment. The fate of heavy metals introduced by FGD gypsum in sodic or saline-alkali soils is still unclear. This work aims to investigate the effects of FGD gypsum addition on the heavy metal distributions in a sodic soil. Original soil samples were collected from typical sodic land in north China. Soil column leaching tests were conducted to investigate the influence of FGD gypsum addition on the soil properties, especially on distribution profiles of the heavy metals (Pb, Cd, Cr, As, and Hg) in the soil layers. Results showed that pH, electrical conductivity, and exchangeable sodium percentage in amended soils were significantly reduced from 10.2 to 8.46, 1.8 to 0.2 dS/m, and 18.14% to 1.28%, respectively. As and Hg concentrations in the soils were found to be positively correlated with FGD gypsum added. The amount of Hg in the leachate was positively correlated with FGD gypsum application ratio, whereas a negative correlation was observed between the Pb concentration in the leachate and the FGD gypsum ratio. Results revealed that heavy metal concentrations in soils complied well with Environmental Quality Standard for Soils in China (GB15618-1995). This work helps to understand the fate of FGD gypsum-introduced heavy metals in sodic soils and provides a baseline for further environmental risk assessment associated with applying FGD gypsum for sodic soil remediation.