BDE-28在天然土壤上的吸附行为研究

Sorption Behaviors of BDE-28 on Natural Soils

研究了BDE-28在3种不同有机质含量的天然土壤上的吸附行为,包括吸附过程动力学和热力学等温线.结果表明,双室一级动力学模式较单室一级动力学模式更适于描述BDE-28在天然土壤上的吸附过程动力学特征,尤其是在吸附初始阶段(0～25 h).快吸附自吸附初始到表观吸附平衡的整体吸附过程中占据优势地位,而慢吸附的贡献率则逐渐增加并在49～55 h后达到相对稳定.快吸附达到其吸附容量的时间远快于慢吸附.在吸附开始阶段的2.5～4.5 h,BDE-28吸附总量的增加主要决定于快吸附;但在后续的吸附阶段,慢吸附的影响逐渐成为主导.在所研究的平衡浓度范围内,DA模式和Freundlich模式对BDE-28吸附等温线均可提供较好的且相似的拟合结果.就Freundlich模式而言,具有较低(0.72%)和较高(7.90%)TOC分数的样品的非线性指数n都接近1.0(分别为1.03±0.05和1.00±0.05),表明2种土样在所研究的BDE-28平衡浓度范围内呈现线性吸附特征;而另一TOC含量居中(4.42%)的土样则表现出明显的非线性行为,模型非线性指数n<1.0(0.89±0.04).

The sorption kinetics and isotherms of BDE-28 on three natural soils with different soil organic matter fractions（fOC） were investigated.The results indicated that a two（fast and slow）-compartment first-order model was more appropriate for describing the sorption kinetic data,compared to a one-compartment first-order model,especially in the initial sorption stage within 25 h.The fast sorption was predominant during the whole sorption process from beginning to the apparent sorption equilibrium;while the contribution of the slow sorption to the total sorption amount gradually increased and then achieved a plateau at 49 h or 55 h.The approaching time to the individual sorption capacity for the fast sorption was much shorter than that for the slow sorption.The contribution of the fast sorption to the increase in the total sorption amount of BDE-28 was prevailing at the beginning of sorption process from 2.5 h to 4.5 h;whereas the fraction of the slow sorption became primary at the subsequent stage of sorption process.The fitting results by the Dubinin-Ashtakhov（DA） model were comparable with those by the Freundlich model in the range of apparent equilibrium concentration studied.As for the Freundlich model,the nonlinear exponent（n） values of BDE-28 for the two samples with lower fOC（0.72%） or higher fOC（7.90%） approached to 1.0（1.03 ± 0.05 and 1.00 ± 0.05,respectively）,suggesting the linear sorption characteristics in the studied range of apparent equilibrium concentrations of BDE-28;while the nonlinear behavior of BDE-28 for the left sample with medium fOC（4.42%） was indicated by its n value less than 1.0（0.89 ± 0.04）.