Effect of ZnCl2, H3PO4, and KOH activation on low-temperature NH3-denitration performance of activated carbon

This study aims to explore the effect of the activator type, activation time, and activator concentration on the denitration performance of activated carbon (AC). Combined with denitration experiments, scanning electron microscopy, pore size analysis, and Fourier transform infrared spectroscopy characterization methods, an orthogonal experiment was conducted using zinc chloride (ZnCl₂), phosphoric acid (H₃PO₄), and potassium hydroxide (KOH) as activators to explore the interaction between various factors and their effect on the denitration performance of AC. The results show that the denitration rate of ZnCl₂-activated AC is generally low because a high concentration of ZnCl₂ will block the micropores of AC and destroy the original structure. The denitration rate of H₃PO₄-activated AC decreased with the increase in H₃PO₄ concentration, especially severe blockage occurred on the AC-H3 surface. KOH activation can optimize the pore structure of AC and generate some oxygen-containing functional groups, which is beneficial to improve the adsorption performance of AC. Orthogonal experiments showed that the activator type had the most obvious effect on the denitration rate, followed by the activation time, whereas reagent concentration had little effect on the denitration rate. The optimum activation condition was 3 mol L⁻¹ KOH at 80°C for 3.5 h.