Correlation between microstructure and dissolution property of magnesium hydroxide synthesized via magnesia hydroxylation: Effect of hydration agents

Abstract

The dissolution of magnesium hydroxide (MH) is a crucial process in its environmental protection application filed. In the present study, we attempted to improve the dissolution property of MH by changing the synthesis conditions. Various MH nanoparticles were prepared by MgO hydroxylation within hydration agents. The pH-stat method was applied to investigate the dissolution rate of the hydrate product. SEM, EDS-Mapping, FT-IR, and XRD technologies were utilized to gain surface and bulk structure information about the hydroxylation product. The dissolution property test results show that the average OH− released rate and Acid Neutralizing Capacity (ANC) in 120 min were promoted significantly form 27.7 ± 0.55 mmol/min/mol MH and 29.32 ± 0.59 mmol H+/g to 45.69 ± 1.37 mmol/min/mol MH (10 g NH4AC as hydration agent) and 31.31 ± 0.63 mmol H+/g (5g MgAC2 as hydration agent). The morphology and structure characterization results show that product with thin flake structure, large microscopic internal strain and low crystallinity would exhibit high dissolution activity. The present experimental results indicate that the curled sheet structure is an important reason for dissolution performance improvement, which is also proved by the Density-Functional Theory (DFT) calculation results of the affinity of H2O for uptake by the MH (001) surface. The results will be used to guide the synthesis of MH slurry with high activity and also provide valuable reference for the regulation of dissolution properties of other crystals.