Experimental and RSM-based process-parameter optimization of NaHSO ₄ -Assisted thermal activation of coal fly ash for alumina extraction

This study investigates the NaHSO4-facilitated thermal processing of coal fly ash for alumina extraction and the optimization of critical process variables using Response Surface Methodology (RSM). SEM, TGA, and XRD techniques were utilized to examine the NaHSO4-facilitated thermal activation of coal fly ash. A Box – Behnken Design (BBD) employing RSM was utilized to evaluate the influence of several process factors, including temperature (200–1000°C), duration (0.5–4 h), and NaHSO4/Al2O3 molar ratio (2–8) on the extraction percentage of alumina. Under optimal operational parameters of a NaHSO4/Al2O3 molar ratio of 4, calcination duration of 3 hours, and a thermal treatment temperature of 600°C, a maximum alumina extraction percentage of 90.23% was achieved. The quadratic model, based on ANOVA results, has demonstrated the high predictability of the response and identified optimal operational conditions. This work demonstrates that NaHSO4-assisted thermal activation is an effective method for extracting alumina from coal fly ash under optimal conditions. The findings indicate that NaHSO4-assisted thermal activation offers an efficient method for alumina extraction from coal fly ash under optimized conditions.