Ultrasonic-assisted desulfurization of organic sulfur of jambi coal using mixtures of potassium tert-butoxide/tetrahydrofuran and peroxyacetic acid

Chemical desulfurization remains an efficient technique for eliminating organic sulfur from coal, but removing organic sulfur is challenging owing to coal's complex macromolecular structures. In this study, peroxyacetic acid (PAA) and potassium tertbutoxide/tetrahydrofuran (KOTBU/THF) were used to desulfurize Jambi high-sulfur coal in the presence of ultrasonics. The parameters that were used to investigate the effect of sulfur removal are the concentration of acetic acid (30,50, and 70) and potassium tert-butoxide (4.75,10,17.5, and 25%), the temperature (30,50, and 70°C), and the sonication time (10,20, and 30 minutes). The optimization of coal desulfurization using PAA and KOTBU/THF was conducted by response surface methodology (RSM) utilizing a central composite design (CCD). The results indicate the highest reduction of 43.54% in organic sulfur for the coal treated by PAA with the conditions of 70:30 (CH3COOH: H2O2), 30°C for 30 minutes, while 66.76% with KOTBU/THF was achieved at optimized conditions of 25% potassium tert-butoxide at 70°C for 30 minutes. The percentage of inorganic, total sulfur, pyrite, and sulfate sulfur of PAA led to ca. 35- 62, 42-74, 43-78, and 15-43%, respectively. Compared to KOTBU/THF with the amount of ca. 43- 73, 50-81, 50-85, and 36-67% using ASTM D2492, with the organic sulfur being determined by difference. The result of absorbance in hydroxyl radical production by PAA and KOTBU/THF was consistent with the regular pattern of the total sulfur removal. From the FESEM-EDX analysis, the sulfur content for both treated coals decreased from 4.2% to 2.4% (PAA) and 1.0% (KOTBU/THF).