摘要
铁(氢)氧化物对P的吸持和释放在一定程度上决定着P的生物有效性和水体富营养化。以两种环境中常见晶质铁氧化物(针铁矿和赤铁矿)为对照,采用X射线衍射(XRD)、透射电镜(TEM)、热重分析(TGA)和孔径分析以及动力学和吸附-解吸热力学平衡等技术方法,研究了弱晶质水铁矿对P吸附-解吸特性,并探讨了相关机制。实验表明,三种矿物对P的吸附分为起始的快速反应和随后的慢速反应,它们均符合准一级动力学过程,反应中OH–释放明显滞后于P吸附,P吸附经历了从外圈到内圈配位、单齿到多齿配位过渡的过程;与晶质氧化铁比,水铁矿吸附容量和OH–释放量更大、慢速吸附反应更快、存在缓慢扩散反应阶段,吸附容量依次是:水铁矿(4.36μmol/m2)>>针铁矿(2.62μmol/m2)>赤铁矿(2.28μmol/m2);针铁矿和赤铁矿吸附P符合L(Langmuir)模型,而水铁矿更符合F(Freundlich)模型。中性盐介质(KCl)中在最大吸附量时P的解吸率依次为:水铁矿(8.5%)<针铁矿(10%)<赤铁矿(12.5%);柠檬酸通过配体解吸和诱导溶解两种机制促进P的解吸,最大吸附量时解吸率依次是:针铁矿(25%)<水铁矿(32%)<赤铁矿(50%)。
The retention and release of P onto iron oxides influence and determine the bioavailability and eutrophication of R We study the adsorption-desorption characteristics of P onto ferrihydrite and explore the relevant mechanisms compared with two common crystalline Fe oxides （goethite and hematite）, using the techniques of X-ray diffraction （XRD）, transmission electron microscopy （TEM）, thermal gravimetric analysis （TGA）, porosity structure analysis and the methods of kinetics and adsorption-desorption equilibrium. Results show a fast initial adsorption took place in a few minutes followed by a slow reaction process, both of which can be well fitted by first order kinetics. During the reaction, the release of OH lags behind P adsorption and increases step by step, indicating that P adsorption may go through complexation from outer-sphere to inner-sphere, from monodentate to bidentate coordination. Compared with goethite and hematite, ferrihydrite has higher amount of P adsorption and OH release, faster slow reaction process, and exhibits slow diffusion reaction stage. The maximum adsorption capacities are in order of： ferrihydrite （4.36μmol/m^2） 〉〉 goethite （2.62 μmol/m^2） 〉 hematite （2.28μmol/m^2）; adsorption isotherms of goethite and hematite agree well with Langmuir model while ferrihydrite exhibits an adsorption isotherm of Freundlich type. Desorption percentage of adsorbed P by neutral electrolyte at maximum adsorption capacities is in order of： ferrihydrite （8.5%） 〈 goethite （10%） 〈 hematite （12.5%）. Relatively, citric acid significantly promotes the desorption reaction. Desorption percentages at the maximum adsorption capacity are in order of： goethite （25%） 〈 ferrihydrite （32%） 〈 hematite （50%）.
出处
《地球化学》
CAS
CSCD
2012年第1期89-98,共10页
Geochimica
基金
国家自然科学基金重大项目(30890132,30890133)
国家自然科学基金(41171197)
国家大学生创新性试验计划项目(091050404)
