OH-浓度对地下水中铁碳酸盐沉淀形成的影响

Investigation of the effect of OH^- concentration on the formation of iron carbonate precipitation in groundwater

铁的碳酸盐沉淀是Fe^0-PRB运行过程中最为常见的铁腐蚀产物,其对Fe^0-PRB的长期运行有重要的影响.探究这类沉淀产物形成的环境条件,可为控制Fe表面碳酸盐沉淀的生成提供重要依据.本文以Fe Cl_2、Na OH、Na_2CO_3为反应物,考察了缺氧条件下不同[OH^-]=0.02,0.06,0.1mol/L及R=[Fe^(2+)]/[OH^-]、R′=[CO_3^(2-)]/[OH-]对铁的碳酸盐沉淀生成情况的影响.结果表明,不同实验条件下检测到了Fe CO_3、Fe_2(OH)_2CO_3及Fe_6(OH)_(12)CO_3三种铁的碳酸盐沉淀.Fe_6(OH)_(12)CO_3仅能在低浓度[OH^-]=0.02mol/L时生成,高浓度的OH^-条件下不能生成.Fe_2(OH)_2CO_3在较低的OH-浓度,较小的R条件下生成;较高的OH^-浓度,较大的R同样有利于Fe_2(OH)_2CO_3的生成.Fe CO_3仅在[OH^-]=0.02mol/L,[Fe^(2+)]、[CO_3^(2-)]均较低情况下与Fe_2(OH)_2CO_3共同生成.

Iron Carbonate precipitation is the most common corrosion products during the process of Fe0-PRB operation, which have important influence on the long-term operation of Fe0-PRB. Exploring the precipitate formation condition can provide vital evidence to controll its formation on the Fe surface. Experiments were conducted in FeCl2, NaOH, and Na2CO3 solutions to investigate the effect of different OH- concentration （0.02、0.06、0.1mol/L） and R=[Fe2＋]/[OH-]、R′=[CO32-]/[OH-] on the precipitate formation under anaerobic conditions. FeCO3、Fe2（OH）2CO3 and Fe6（OH）12CO3 were detected under the different experimental conditions, Fe6（OH）12CO3 can formation in the low concentration [OH-]=0.02mol/L and not formation in the high OH- concentration solutions. The low OH- concentration and low R, high OH-concentration and large R have positive effect on the formation of Fe2（OH）2CO3. FeCO3 just be detected and precipitated with Fe2（OH）2CO3 in the system with low concentrations of Fe2＋、CO32-、OH-.