Effects of doping ions on the degradation of coal-mine gas via Fenton reagent

The degradation of coal-mine gas with Fenton reagent is carried out through the oxidation reactions between methane and hydroxyl radicals (·OH) generated via the catalytic decomposition of H2O2 with Fe2+.In order to restrain the invalid decomposition and improve the efficiency of coal-mine gas degradation with Fenton reagent,the stability of Fenton reagents can be kept by doping hard-acid ions,such as Mg2+,Ca2+,and Na+,etc.The influence rules of Mg2+ on the stability of Fenton reagents,the apparent formation rate of ·OH and the degradation ratio of methane were systematically investigated.The experimental results demonstrate that the introduction of Mg2+ can effectively maintain the stability of Fenton reagents and improve the efficiency of gas degradation and ·OH formation via Fenton reagents.When 0.5 mmol/L of Mg2+ is added,the apparent formation rate of ·OH reaches to a maximum of 80.41% after 0.5 h.Meantime,the degradation percentage of coal-mine gas increases up to 40%,which is much higher than that obtained in the traditional Fenton system.Furthermore,by means of quantum chemistry theory,it is evidenced that the transmission process of chain reactions with Fenton reagents can be lengthened by decreasing the activity of peroxy-radicals (HOO·) via doping hard-acid ions.The special effect of hard-acid ions can decrease the ineffective decomposition of H2O2,promote the stability of Fenton reagents,and enhance the efficiency of apparent formation rate of  ·OH and degradation ratio of gas,which present the theoretical basis for the efficient degradation of coal-mine gas.