Sulfuric acid improves the reactivity of zeolites <italic>via</italic> dealumination: Fid-Bau Portal

Sulfuric acid improves the reactivity of zeolites via dealumination

Chen, Xu / Srubar, Wil V. III

Highlights • Sulfuric acid (H2SO4) treatment enhanced reactivity of zeolites with Ca(OH)2. • H2SO4 induced smaller particle sizes and liberated aluminates via dealumination. • Smaller particle sizes accelerated peak heat evolution. • Free aluminates increased heat via reaction with aqueous Ca²⁺.

Abstract The demand for supplementary cementitious materials (SCMs), like fly ash, slag, and silica fume, is projected to rise over the next few decades. However, global decarbonization efforts, such as decommissioning of coal-fired power plants, will limit the supply of SCMs. Therefore, alternative SCM sources are a critical need for the cement and concrete industry. However, the high crystallinity of zeolites limits their pozzolanic reactivity. The goal of this work was to improve the reactivity of two common zeolites, namely clinoptilolite and SSZ-13, by treating them with sulfuric acid. The treatment enhanced zeolite reactivity via dealumination and decreased particle sizes, which led to increased reactivity with calcium hydroxide, as indicated by a 42.0% increase in reaction heat measured by isothermal calorimetry. We elucidate mechanistic understanding that smaller particle sizes induced by acid treatment accelerated peak heat evolution, while free aluminates from dealumination increased heat via direct reaction with aqueous Ca²⁺.