多木素体系中过渡金属催化分解过氧化氢的规律

Decomposition of hydrogen peroxide by the lignin-combined transition metals in pulp bleaching

研究了木素/锰体系、木素/铁体系,以及木素/锰/铁体系对过氧化氢分解的影响规律。并选用乙二胺四乙酸、硅酸钠、硫酸镁等过氧化氢稳定剂,探究其在控制木素/金属体系催化分解过氧化氢的积极影响。研究结果表明,木素/过渡金属体系中,过氧化氢的分解符合伪一级动力学行为规律。其中,木素/铁体系的过氧化氢分解伪一级速率常数k_(obs)为0.0068min^(-1),木素/锰体系的过氧化氢分解速率常数k_(obs)为0.0063min^(-1),木素/铁/锰体系的过氧化氢分解速率常数k_(obs)为0.0053min^(-1)。可见,在木素存在条件下,铁/锰对过氧化氢分解存在协同促进作用。另外,硫酸镁、硅酸钠和乙二胺四乙酸等常用稳定剂,对木素/过渡金属体系中过氧化氢分解有抑制作用。当乙二胺四乙酸单独添加时,对木素/铁/锰体系过氧化氢分解的抑制作用最强,伪一级速率常数为0.0004min^(-1)。

IThe essay hereby investigated the effects on the decomposing of hydrogen peroxide under typical pulp bleaching conditions, including lignin-combined manganese, lignincombined iron, and lignin-combined iron and manganese. A variety of bleaching stabilizers, such as ethylene diamine tetraacetic acid（EDTA）, sodium silicate（Na_2SiO_3） and magnesium sulfate（MgSO_4）, were selected and added individually to investigate their positive effects on hydrogen peroxide decomposition. The results showed that the hydrogen peroxide decomposition in the presence of lignincombined transition metals could conform with the principles of pseudo-first-order kinetics. The pseudo-first-order rate constant（k_（obs）） of peroxide decomposition with lignin-combined iron was 0.0068 min^（-1）, while that of lignin-combined manganese was 0.0063 min^（-1）. Synergistic effect of manganese and iron combined with lignin on peroxide decomposition was found to be exist, with a pseudo-first-order rate constant（k_（obs）） of 0.0053 min^（-1）. It proved that iron and manganese could work in coordination to push the decomposing of hydrogen peroxide. And regular stabilizers such as MgSO_4, Na_2SiO_3 and EDTA can restrain the decomposition of hydrogen peroxide. Especially the individual addition of EDTA can bring the most obvious effect on the reduction of peroxide decomposition with the k_（obs） of 0.0004 min^（-1）.