卤素离子还原三价钴氨络合物的实验研究

Experimental study of hexamminecobalt (Ⅲ) regeneration by halide ions

钴氨络合物具有良好的同时脱硫脱硝能力,但是在吸收的过程中,[Co(NH_3)_6]^(2+)易被氧气氧化为[Co(NH_3)_6]^(3+)而失去络合NO的能力。为了使反应循环进行,需将[Co(NH_3)_6]^(3+)还原为[Co(NH_3)_6]^(2+)。利用碘离子和溴离子做为[Co(NH_3)_6]^(3+)的还原剂,搭建再生实验台开展pH值、温度以及卤素离子浓度对[Co(NH_3)_6]^(3+)转化率影响的实验研究,比较2种离子的还原效果。实验结果表明:与溴离子相比,碘离子还原[Co(NH_3)_6]^(3+)的反应速率更快,达到平衡的时间更短,[Co(NH_3)_6]^(3+)的转化率更高,还原效果更好。pH值降低、温度升高可促进碘离子和溴离子对[Co(NH_3)_6]^(3+)的还原。浓度提高对碘离子还原[Co(NH_3)_6]^(3+)的影响很小,但可提高溴离子做还原剂时[Co(NH_3)_6]^(3+)的转化率。当溶液的pH值为9.8,温度为50℃,浓度为0.03 mol/L时,碘离子做还原剂的[Co(NH_3)_6]^(3+)转化率最大可达52%,溴离子做还原剂的[Co(NH_3)_6]^(3+)转化率最大可达33%。

Hexamminecobalt(Ⅱ)has good simultaneous desulfurization and denitrification ability,but it could be easily oxidized by oxygen to form hexamminecobalt(Ⅲ)in the absorption process.While hexamminecobalt(Ⅲ)could not bind NO.In order to drive the reaction in circles,[Co(NH 3)6]3+needs to be regenerated to[Co(NH 3)6]2+.Iodide ion and bromide ion were employed as reductants of[Co(NH 3)6]3+.A regeneration experimental apparatus was set up to study the influence of pH,temperature and halide ion concentration on conversion efficiency of[Co(NH 3)6]3+and compare the reduction effect of these two kinds of ions.The experimental results show that the reduction effect of iodide ion is better than that of bromide ion due to its faster reaction speed,less equilibrium time and higher conversion efficiency of[Co(NH 3)6]3+.Decreasing pH and increasing temperature could increase the[Co(NH 3)6]3+conversion efficiencies of both iodide ion and bromide ion.Increasing the halide ion concentration had little effect on[Co(NH 3)6]3+regeneration by iodide ion,while it could increase the[Co(NH 3)6]3+conversion efficiency regenerated by bromide ion.Conversion efficiency of[Co(NH 3)6]3+could get its maximum value of 52%regenerated by iodide ion and 33%regenerated by bromide ion at pH of 9.8,temperature of 50℃and halide ion concentration of 0.03 mol/L.