Hazardous maize processing industrial sludge: Thermo-kinetic assessment and sulfur recovery by evaporation-condensation technique

Abstract

In the present work, a detailed thermo-kinetics of hazardous sulfur-rich sludge generated from the corn processing industry was performed for acquiring the optimum parameters for the efficient recovery of sulfur using the evaporation-condensation technique. Sulfur in the sludge was found to be 79 ± 3% (wt%) as estimated by the Bureau of Indian Standards method. A weight loss of 77 ± 3% was found in the active devolatilization zone from ≈ 200–400 °C. The online FTIR confirmed the evolution of mainly sulfur vapors (S8) along with some sulfur dioxide (SO2) and disulfur (S2). The thermogravimetric data (TG) was used to evaluate the kinetic parameters with the help of model-free methods, and Z-master plots determined additional insight into the reaction mechanism. Furthermore, the calculated activation energy (Ea) was used to determine the thermodynamic feasibility. The average Ea values appraised by FM, FWO, sDAEM, and ST models were 55.43, 72.04, 62.33, and 62.67 kJ mol−1, respectively. Overall, 91.2% of sulfur was successfully recovered at 400 °C, having 99 ± 0.5% purity. The approximate cost analysis of the sulfur recovery process was also estimated to check the economic viability. Recovered sulfur could be directly used for industrial and agricultural applications without any further purification.