摘要
批量法实验研究表明,五氯苯酚(PCP)在合成的针铁矿、纤铁矿和赤铁矿表面吸附的浓度等温线为饱和型特征,可用Langmuir公式拟合,而pH吸附等温线为峰型曲线,峰值在pH≈5。矿物表面化合态和PCP溶液离子化合态分析与计算表明,PCP在氧化铁矿物表面存在两种吸附反应模式,即表面静电吸附反应和表面络合吸附反应,表面静电吸附反应常数比表面络合吸附反应常数高1～2个数量级。并进一步从反应机制上证明了憎水型可离解有机化合物(HIOCs)在矿物表面吸附的模式与趋向性。
The experiments of pentachlorophen ol(PCP)adsorption onto the suspensions of t he synthesized iron oxides are performed by the batch equ ilibrium technique with the initial PCP concentration C 0 =11.8μmol /L and the solution volume 25mL,which cont aining solid mineral phase goethite(α-FeOOH)=105.2mg,lepidocrocite(γ-FeOOH)=60.8mg and hematite(α-Fe 2 O 3 )=64.0mg,respectively,and under I=0.1(NaCl )and t=25℃for a reaction period 24h.Both of con centration isotherms and pH isotherms are drawn out.The former can be fitted by Langmuir equation with the C max =3.27μmol /g and K L =0.0581for goethite at pH =5.3,2.37μmol /g and 0.0685for lepidocrocite at pH =5.7,and 1.98μmol /g and 0.121for hematite at pH =5.7,respectively.The latter shows a typical peak curve with the peak position about pH≈5,and the peak values are 1.89μmol /g for goethite,1.69μmol /g for lepidocrocite and 1.98μmol /g for hematite,respectively,t hat are almost 1～2orders of magnitude larger than the p eak values of the phyllosilicate kaolinite,montmorillonite and illite reported by our previous study.Based on the acid-base titration data,the protonation constants of iron oxides are calcu lated in this study,which are p K a1 =6.26and p K a2 =9.48for goethite,6.38and 9.30for lepidocrocite,6.34and 8.88for hematite,respectively.Thus th ere may have three kinds of speciatio n:protonation form >FeOH +2 ,neutral form>FeOH and deprotonation form>FeO - on iron oxide surfaces.Meanwhile PC P may be in molecular form C 6 Cl 5 OH in acid solution or ionized to the anion form C 6 Cl 5 O - in neutral or basic solution for p K=4.71.The speciation topographic analysis suggests that the two kinds of the surface adsorption reactions may be taken place,the s urface electrostatic adsorption and surfa ce complexation adsorption.The calculation results of the adsorption r eaction equilibrium constants strongly suggest that the predominant surface re action is the electrostatic interaction with K 1 =1.15×10 6 L /mol for goethite,1.07×10 6 L /mol for lepidocroc
出处
《地球化学》
CAS
CSCD
北大核心
2005年第3期297-303,共7页
Geochimica
基金
国家自然科学基金(40373035)
广东省自然科学基金(030461)
中国科学院知识创新工程前沿研究项目(GIGCX-04-02)~~
关键词
五氯苯酚
针铁矿
纤铁矿
赤铁矿
吸附
表面反应模式
pentachlorophenol
goethite
lepi docrocite
hematite
adsorption,s urface reaction models
