ABSTRACT
This study focuses on the difficulty of converting fluorinated rare earth elements into hydroxylated rare earth elements in rare earth melt electrolysis slag (RMES) and proposes the use of a microwave-assisted atmospheric alkaline leaching method for the treatment of RMES. The leaching behavior of RMES under microwave-assisted atmospheric alkaline leaching was studied, and the optimal reaction conditions were determined. Under the conditions of a reaction temperature of 150 °C, initial NaOH concentration of 60 %, NaOH-to-slag mass ratio of 4:1, microwave power of 700 W, reaction time of 120 min, and stirring speed of 300 r/min, the conversion rate of fluorinated rare earths reached 99.17 %. The apparent rate equation of the microwave-assisted atmospheric alkaline leaching process was obtained by leaching kinetic analysis, and the apparent activation energy under this process was calculated to be 54.872 kJ/mol, which was 12.458 kJ/mol lower than that achieved when conventional heating was used for leaching (67.33 kJ/mol).
ABSTRACT
Biodegradation behavior and kinetics of ethylthionocarbamate under nitrate, sulfate and ferric reducing conditions by mixed cultures enriched from the anaerobic digester sludge was investigated. The results showed that ethylthionocarbamate could be degraded independently by the mixed cultures coupled to nitrate, sulfate, and ferric reduction, and meanwhile, nitrite, sulfide, and ferrous were accumulated as a result of nitrate, sulfate and ferric reduction, respectively. Ferric was a more favorable terminal electron acceptor compared to nitrate and sulfate. The order of the electron acceptors with decreasing biodegradation rates of the ethylthionocarbamate was: ferric>nitrate>sulfate, and the corresponding maximum biodegradation rate was 7.240, 6.267, and 4.602 mg/(L·d), respectively. The anaerobic biodegradation of ethylthionocarbamate under various electron acceptor conditions can be accurately described by first order exponential decay kinetics.
