Reductive Dehalogenation of Iodoform by Fe/Pd Bimetallic Material

This study investigated the reductive dehalogenation of iodoform by Fe/Pd bimetallic material. The influences of bimetallic dosage, pH and dissolved oxygen (DO) were investigated to find the best reaction condition. Moreover, analysis of mechanism and biotoxicity test were also conducted to obtain a deeper understanding on the reaction process. The results indicated that increase the dosage of Pd/Fe bimetallic material could significantly enhance the removal efficiency of iodoform. The remaining concentration of iodoform decreased remarkably from 630.40 to 377.40 μg/L within 20 min reaction when the bimetallic dosage increased from 5 to 20 g/L. Acidic condition was favorable to the dehalogenation of iodoform. The remaining concentration of iodoform dramatically decreased to 294.9 μg/L after 20 min reaction when the initial pH was 3. The presence of dissolved oxygen inhibited the reductive dehalogenation of iodoform by Pd/Fe bimetallic system. Fe/Pd bimetallic system achieved excellent performance on the dehalogenation of iodoform probably due to the primary battery structure created between iron and plating metal Pd. This structure could effectively avoid the blocking of active reaction sites caused by the formation of iron hydroxide precipitation which covering the surface of iron as well as accelerate the electron transfer rate. The analysis on the reaction mechanism indicated that iodoform underwent dehalogenation step by step after receiving the electron transformed from zero valent iron. 5.09% of iodoform was reduced to diiodomethane, 29.75% of iodoform was reduced to iodomethane, and 62.97% of iodoform was reduced to methane during the whole reaction period when calculated by molality. The toxicity text showed that the relative luminous inhibition rate of water sample was decreased from 76.23 to 11.38% during the dehalogenation of iodoform by Fe/Pd bimetallic material.