Sorption and cosorption of the nonionic herbicide mefenacet and heavy metals on soil and its components

Sorption and cosorption of the nonionic herbicide mefenacet and two typical metals (copper and silver) on black soil and its components (kaolinite and humic acid) were investigated. It was found that because of their different valences and properties, Cu²⁺and Ag⁺ presented different effects on the sorption of mefenacet. Due to the competition of Cu²⁺, along with the shells of dense water formed by its surface complexation, for sorption surface area with mefenacet, the addition of Cu²⁺ decreased the sorption amount of mefenacet on soil and its components, especially on humic acid. However, the addition of Ag⁺ significantly enhanced the sorption of mefenacet, which was attributed to the softness of the cation that weakened the hydrophilicity of the local region around Ag⁺-complexed functionalities, and thus mitigated the competitive sorption of water. In addition, the sorption of mefenacet on soil with or without the two metals was generally decreased with increasing pH, which was caused by the hydrolysis of carbonyl and carboxyl groups on the surface of the sorbents, π-π interaction between mefenacet and the soil organic matter, and so on. On the other hand, the presence of mefenacet seemed to have little effect on the sorption of Cu²⁺ and Ag⁺, indicating that Cu²⁺ and Ag⁺ might be sorbed strongly on the tested sorbents and the mefenacet added was too low in concentration to affect the sorption of the metals.     

聚合氯化铝铁和粘土应急去除蓝藻的室外模拟研究

文章在开展PAFC去除淡水中的铜绿微囊藻影响因素的室内模拟研究基础上进行PAFC和粘土应急去除巢湖水中蓝藻的室外模拟研究。结果表明,在20 mg/L的絮凝剂用量下,聚合氯化铝铁(PAFC)对巢湖水中蓝藻的沉降去除效果优于聚合氯化铝,达到97.7%。PAFC,PAFC和粘土(高岭石或海泡石)可以快速高效絮凝沉降巢湖水中的蓝藻,并且在30 d之内除藻率稳定地维持90.0%以上。同时探讨其对藻毒素释放抑制的影响,结果表明,加入PAFC和粘土(海泡石或高岭石)1 d后能有效地吸附水中的藻毒素,PAFC和海泡石组的吸附去除率大于PAFC和高岭石,且30 d内仍一直维持藻毒素浓度低于对照组。     

草酸促进双酚A在黏土矿物悬浮液中光降解研究

选择两种常见的天然黏土矿物高岭石和蒙脱石,研究了有机污染物双酚A(BPA)在其表面的吸附及草酸对黏土矿物悬浮液中BPA光降解的影响.结果表明,BPA在两种黏土矿物表面的吸附量较小,吸附符合Langmuir等温式.在250W金属卤化物灯(λ≥360nm)照射下,草酸可显著促进BPA在高岭石和蒙脱石悬浮液中的光降解,降解动力学符合Langmuir-Hinshelwood方程. 降解速率受pH值的影响较大,pH=4.0时速度最快,光降解速率同时受草酸浓度的影响.最后,通过分析矿物中铁的化学环境及反应过程中铁浓度变化,分析了草酸促进BPA在黏土矿物悬浮液中光降解的可能机制.     

Removal of C.I. acid brown 75 from aqueous solution by kaolinite

The adsorption of acid brown 75 onto kaolinite in aqueous solution was studied with respect to the pH, adsorbent dosage, contact time, initial concentration, and operating temperature. Desorption of dye from dye-saturated kaolinite was observed. Experimental data indicated that the adsorption capacity of kaolinite for the dye was higher in acidic rather than in basic solution. The maximum adsorption capacity of kaolinite towards the dye was found to be 96.5 mg g^?1 (pH 1.0). At the optimal adsorption condition, the dye removal ratio was 95.5%. Dye-saturated kaolinite could desorb at aqueous NaOH, the desorption ratio of dye was 78.8%. The linear Langmuir and Freundlich isotherm models are well fitting to represent the experimental data.     

低浓度范围内聚丙烯酰胺在黏土矿物上的吸附特征

用酰胺基团溴化后碘化镉-淀粉显色分光光度法测定了在0～50mg/L低浓度范围内聚丙烯酰胺(PAM)在高岭土和蒙脱土上的吸附等温线,并考察了电解质浓度和类型对吸附的影响.结果表明,PAM在黏土矿物上有很强的吸附亲合力,吸附等温线为Langmuir型.电解质能大大增强PAM在黏土矿物上的吸附,其中二价离子比一价阳离子更有效.电解质浓度较低时,PAM分子主要以链序态吸附,电解质浓度较高时以链环态、链端态吸附的数量逐渐增多.PAM的吸附只限制在层状黏土矿物的外表面上.在Na⁺介质中,PAM在两种黏土矿物上的吸附量差别不大;而在Ca²⁺介质中,蒙脱土悬浮颗粒产生分裂,为PAM的吸附提供新的外表面积,PAM的吸附量大大高于在高岭土上的吸附量,前者约是后者的2～3倍.     

针铁矿-高岭石复合体的表面性质和吸附氟的特性

采用X-射线衍射(XRD)、扫描电镜(SEM)、红外(FT-IR)光谱、质子电位滴定、比表面及微孔分析等方法对针铁矿、高岭石及其复合体的基本性质进行了表征;研究了供试样品对氟的吸附容量及吸附模型.结果表明,在悬浮液体系中,针铁矿可包被在高岭石表面形成二元复合体.复合体的孔径主要分布在0.42 nm和0.61 nm左右,BET表面积为34.08 m2/g,表面分形度D=2.726,质子电荷零点(pHPZNPC)位于5.50～6.50间.初始pH=6.00时,针铁矿对氟的吸附容量(qmax)为4.506 mg/g,高岭石的吸附容量为0.608 mg/g,复合体的吸附容量为3.520 mg/g.用Langmuir和Freundlich方程拟合了针铁矿、高岭石及复合体对氟的等温吸附数据,其中Langmuir方程拟合的相关系数(R2)分别为0.964、0.991和0.799,Freundlich方程拟合的相关系数分别为0.925、0.886和0.995.3种矿物吸附氟的主要机制有阴离子配体交换、表面配位和静电作用;此外,"F-键桥"对复合体吸附氟也有重要贡献.与2种单体的平均值比较,针铁矿-高岭石复合体的孔体积和孔径分布无明显变化,比表面积和表面分形度增加,表面羟基含量和质子电荷量减少,吸附氟的能力增强.针铁矿和高岭石单体对氟的吸附属于单层吸附模式,适合用Langmuir方程拟合;多层吸附模型Freundlich方程可很好地描述复合体对氟的吸附.     

pH对粘土矿物胶体在饱和多孔介质中运移的影响

环境pH值条件的变化是影响土壤胶体运移的重要因素之一.本文选取土壤体系中常见的两种不同结构类型的粘土矿物胶体高岭石和蒙脱石作为主要实验材料,通过室内模拟实验和数学模型分析的手段,分别研究了不同pH值条件下,两种无机胶体在多孔介质中的迁移规律.结果表明:高岭石胶体受溶液的pH条件影响强烈,随着pH的变化,ξ电位及颗粒粒径大小发生明显变化,不同的pH条件下的穿透曲线差异明显.在酸性条件下,高岭石胶体回收率显著降低,而蒙脱石胶体基本不受pH影响;利用HYDRUS-1D模型拟合结果与测定数据之间非常匹配,说明利用该模型模拟饱和条件下胶体在多孔介质中的迁移完全可靠.     

粘土矿物与重金属界面反应的研究进展

介绍了3种粘土吸附剂:蒙脱石、高岭石和伊利石对重金属的吸附、脱附等界面反应机理,以及粘土矿物对重金属的选择性及对吸附的影响因素.另外,还探讨了为提高其吸附性能而进行的改性方法.     

高岭土制备聚合氯化铝新工艺

介绍了以高岭土为原料，经盐酸预处理后，加水聚合、调整反应液pH，制备液体聚合氯化铝净水剂的新工艺。对所得产品的净水性能和技术指标进行了测定，结果表明，采用该工艺制得的聚合氯化铝产品技术指标符合GB1592－95标准。     

三氯乙烯在模型吸附剂上的吸附特性

为了分别揭示矿物质、有机质在疏水性有机物吸附中的作用,文章研究了蒙脱石、高岭土、硅胶以及用腐殖酸修饰后的这3种模型吸附剂对三氯乙烯的吸附行为。采用批量吸附实验方法分别研究了三氯乙烯在不同吸附剂上的吸附。结果表明,硅胶、高岭土、蒙脱石对三氯乙烯均具有一定的吸附能力,吸附系数Kd值分别为10.3、3.13、1.15L·kg-1,硅胶的吸附能力明显高于高岭土和蒙脱石。3种无机模型吸附剂对腐殖酸表现出不同的吸附能力,蒙脱石最强,高岭土次之,硅胶最差,与对三氯乙烯的吸附能力正好相反。被腐殖酸修饰后3种模型吸附剂对三氯乙烯的吸附都明显增强,但增强程度不一样,当用8%腐殖酸(腐殖酸与模型吸附剂的质量比)修饰后,3种吸附剂对三氯乙烯的吸附Kd值均在23L·kg-1左右。虽然Kd随有机质的质量分数增高而上升,但是Kd值与有机质的质量分数不存在线性相关关系,特别是对于具有较高吸附能力的无机吸附剂,说明无机矿物本身结构对于吸附起到同等重要的作用。