Preparation and Characterization of High-Specific-Surface-Area Calcium Hydroxide Derived from Carbide Slag

Carbide slag is a bulk industrial solid waste, and its open‑air stockpiling causes severe environmental pollution. In this work, nano‑calcium hydroxide with high dispersity, high activity and large specific surface area was prepared from carbide slag via a coupled process consisting of high‑temperature calcination for impurity removal, controllable crystallization and organic surface composite modification. Key parameters including crystallization temperature, modifier dosage, modifier type and drying temperature were regulated by orthogonal tests to precisely control the nano‑crystal size of calcium hydroxide and effectively mitigate nanoparticle agglomeration. The effects of the four above‑mentioned parameters on the specific surface area of products were investigated using an L₉(3⁴) orthogonal array, and the optimal preparation conditions were determined. Combined with multiple micro‑characterization techniques including TG‑DTA, XRD, SEM and BET, the optimal process for synthesizing nano‑calcium hydroxide was established. Under the optimal conditions, the as‑prepared calcium hydroxide exhibited a grain size of 50–150 nm, a mass fraction of 95.1 %, a specific surface area of 48.97 m²/g, a bulk density of 0.65 g/mL and a pore volume of 0.24 cm³/g. This proposed process enables high‑value resource utilization of carbide slag and provides reliable technical support for preparing desulfurization and denitrification materials from industrial solid waste.