Evaluation of Agricultural Feasibility of Red Mud with the Gypsum from Desulfurization Process and the Regenerated Sulfuric Acid

Abstract

Objectives : Fertilizers were manufactured using red mud, petroleum refining desulfurized gypsum, and recycled sulfuric acid, which are byproducts generated from industrial activities. The chemical properties and heavy metals were analyzed for fertilizers feasibility evaluating, and growth indicators were investigated through lettuce growth experiments and the possibility of agricultural utilizing was determined.Methods : After mixing gypsum with Red Mud at 30 wt% and 50 wt%, fertilizers neutralized at pH 6-7 using regenerated sulfuric acid (RMG30, RMG50) were prepared, and their chemical and heavy metal content were analyzed. In addition, growth indicators (e.g., germination rate, number of leaves, leaf length, leaf width, etc.) were investigated through lettuce growth in soil mixed with 5 to 15% of each fertilizer sample, and agricultural availability for crop growth was assessed.Results and Discussion : Red mud and gypsum mixtures were neutralized by RMG30 and RMG50 within the pH range of 6-7. The contents of heavy metals in the soil of the control and the treatment mixed with RMG30 and RMG50 were all below the concern standards (1 area), and the pH and EC of the treatment soil increased as the amount of fertilizer was injected into the soil. The pH of the soil in growing lettuce was observed to be 6.02 to 8.38, and in most experimental districts, including control soil, it was not included in the growth-affected pH range (pH 5.5 or less, pH 8.0 or higher). The EC of the treatment soil was 8.85 to 20.2 dS/m. In 5% and 10% treatments of RMG50, some growth indices (leaf length) to be higher than those of untreated. And higher growth indicators were observed in RMG50 processing than in RMG30 processing.Conclusion There is no concern about soil pollution caused by heavy metals contained in fertilizers. It is judged that agricultural use will be possible if RMG50 is adjusted to the appropriate EC value of the crop to be grown or used in a salt tolerance crop.