不同波长和强度光照对水体汞还原的影响

采用室内模拟实验,探讨不同光波长、强度对HgCl2还原反应的影响,根据载气中Hg0的实时浓度跟踪HgCl2还原反应的过程,计算Hg0释放通量来进行汞光还原程度定性分析、动力学定量分析,并运用积分法和微分法确定反应级数.结果表明,Hg2+的还原量与光波长呈负相关、与光强度呈正相关,说明光子提供的能量对汞的光还原反应起关键性作用,汞还原率由光波长和强度共同决定,并且受溶液体积和载气流速影响;在各组实验中,载气中的Hg0浓度均表现为先上升再下降后趋于平稳的规律,Hg0浓度上升阶段的主要反应是Hg2+的还原反应和Hg0的释放,而下降阶段的主要反应是Hg0的释放;本研究中可见光下的汞还原反应为一级反应,UVA、UVB光照下的汞还原反应为二级反应,这与汞的配合物具有特定的光谱吸收带和实验用灯提供的光波范围有关.

Influence of Light Wavelength and Intensity on the Reduction of Divalent Mercury in Aquatic System

Laboratory experiments were conducted to investigate the photo-reduction of HgCl₂ under various light wavelengths and intensities. The whole process was tracked by changing Hg⁰ concentrations in argon and Hg⁰ flux was calculated for qualitative and quantitative analysis; the rate order was determined by both differential and integral methods. The principal results indicated: Higher mercury emission flux was observed under shorter light wavelength and stronger intensity, which shows the important role of photo-energy in the reaction. The degree of mercury reduction was determined by radiation wavelength and intensity, and it was also influenced by solution volume and the flow rate of carrier gas. Under different light conditions, Hg⁰ concentrations in argon all increased at the beginning and decreased after a specific time period, since the main reactions in rising period were the photo-reduction of Hg²⁺ and the emission of Hg⁰ while the reaction in decreasing period was the emission of Hg⁰ only. The rate order under visible light was the first order while it was the second order under UVA and UVB, which attributes to the fact that coordination complex has certain light absorption band, which is related with the available light wavelength provided by experimental lamps.