Time-Dependent Dissolution of Potassium from K-Bearing Mineral Residues in Organic Acids

Abstract

<title>Abstract</title> Background and Aims: Potassium (K)- bearing minerals are vital for soil fertility and act as slow-release reservoirs for crop productivity. Organic acids, such as oxalic and citric acids, enhance K dissolution. Methods Time-dependent experiments measured K dissolution from minerals in oxalic and citric acids. Mehlich-1 extraction and atomic absorption spectrophotometry quantified K release over intervals under controlled conditions. Results Oxalic acid enhanced K release by 25% more than citric acid. For biotite-mica, increasing oxalic acid concentration from 0.5 to 5.0 mmol L⁻¹ raised K release from 800 to 1600 mg kg⁻¹. During a further increase to 10 mmol L⁻¹, slightly improved dissolution was recorded. Percentage K release varied by mineral, biotite-mica, muscovite-mica, and K-feldspar recorded 5–11%, 3–7%, and 2–6% respectively. Citric acid caused significant K release between 0.5 and 1.0 mmol L⁻¹, with increases up to 10 mmol L⁻¹. Above 5 mmol L⁻¹, muscovite-mica dissolved more K than biotite-mica and K-feldspar, with K-feldspar showing higher dissolution percentages of 3.1–7.5% in citric acid than oxalic acid that recorded 2.4–6.2%. Conclusion Organic acids enhance K release via chelation, destabilization of mineral surfaces, and solubility increases. Oxalic acid’s superior performance highlights its role in improving soil fertility. Also, oxalic acid outperformed citric acid in dissolving K from minerals, underscoring the importance of targeted nutrient management strategies.