土壤对外源钍的吸附行为表征

外源钍对土壤的污染风险和程度取决于钍在土壤中的吸附行为. 以包头稀土工业区土壤样品和土壤环境矿物组分为研究对象, 通过静态吸附方法研究外源钍在土壤样品和环境矿物组分(高岭土、蒙脱土、碳酸钙、水合氧化铁/锰和腐殖酸)上的吸附, 并对吸附行为进行了表征. 结果表明, 土壤样品对外源钍有很强的吸附能力, 对加入的外源钍(10^-4 mol/L)吸附率在97%以上; 土壤环境矿物组分对加入的外源钍(1 g/L)吸附率在28%～46%之间. 通过扫描电镜-能谱(SEM-EDS)分析可知, 外源钍进入土壤后与矿物组分发生相互作用, 可能形成了稳定化钙质钍碳酸盐和钍磷酸盐; 傅里叶变换红外光谱(FTIR)分析表明, 钍是与土壤环境矿物组分上的活性吸附位点发生相互作用而吸附并保持在土壤中, 是物理吸附和化学吸附共同作用的过程; X射线衍射分析(XRD)表明, 土壤在吸附钍前后, 其矿物组分基本相同, 而矿物晶体相态发生明显变化. 由于不同土壤矿物组分对钍的吸附方式不同, 导致吸附的钍以不同形态存在于土壤中.     

城市土壤对铅的吸附动力学特征及影响因素

采用批量法对温州景山森林公园5种不同土壤的Ph的吸附动力学行为进行了研究,初步探讨了不同理化性质土壤对重金属吸附的影响。结果表明,在实验条件下,5种土样均在180rain内达到吸附平衡;抛物线扩散方程、双常数速率方程和Elovich方程能很好地描述5种土壤Pb^2＋动力学行为;随着外源Pb^2＋质量浓度的增大,土壤对Pb^2＋的吸附量都相应增大;通过吸附速率与吸附强度与土壤理化性质相关性分析,得出土壤对重金属铅的吸附速率是土壤各理化性质综合作用的结果,而土壤对铅的吸附强度在很大程度上取决于土壤pH。     

我国主要类型土壤对稀土元素的吸附和解吸特征

研究了我国主要类型土壤、高岭石和合成氧化物对混合稀土元素的吸附-解吸行为。其对稀土元素的等温吸附可以用Langmuir、Freundlich和Temkin方程描述。决定其对稀土吸附量的因素,主要是粘土矿物类型和无定形氧化铁含量。这两个因素和土壤的pH值决定土壤对稀土的吸附强度。土壤中以及合成的铁、锰氧化物对稀土有强烈专性吸附作用。     

安徽主要土壤对钕的吸附

安徽五种主要土壤在自然和钙饱和状态下对钕的吸附(25℃)都与所选用的Langmnir方程、Temkin方程和Freundlich方程有很好的拟合性。效的最大吸咐量(x_m)与土壤阳离子(CEC)呈显著相关。而表征土壤吸附强度因子与土壤组分有关。钙饱和后对黄褐土和砂姜黑土的吸附性质影响较大,对灰潮土、黄潮土和棕红壤影响较小。总的趋势是:钙饱和土壤吸附钕量都小于相应的自然土壤;吸附强度因子是棕红壤、黄褐土和砂姜黑土小于其对应的自然土壤,而灰潮土和黄潮土则大于其对应的自然土壤。     

掺杂MnO2土壤对多种雌激素化合物的吸附热力学特征及机理

通过析因实验设计优化了掺杂MnO2土壤对雌酮(E1)、雌二醇(E2)、17α-乙炔基雌二醇(EE2)、雌三醇(E3)和双酚A(BPA)等多种雌激素化合物的吸附条件,采用Langmuir吸附等温式和Gibbs方程考察了掺杂MnO2土壤吸附雌激素化合物的热力学规律和吸附过程的热力学性质,并利用傅里叶变换红外光谱对吸附机理进行了探讨,同时利用液相色谱-质谱联用技术对土壤中多种雌激素化合物的主要降解产物进行了定性分析.结果表明,雌激素化合物浓度和MnO2掺杂比例对雌激素化合物在掺杂MnO2土壤中的吸附量起显著的正效应,土壤质量对雌激素的吸附起负效应,土壤-水吸附体系的pH值对E2的吸附量起正效应而对E3起负效应.Langmuir吸附等温式能够描述雌激素在掺杂MnO2土壤中的热力学吸附行为(R2>0.99),吸附过程中雌激素化合物的ΔG均为负值,绝对值均小于40 kJ/mol,说明土壤吸附雌激素化合物为自发的物理吸附过程;掺杂MnO2土壤对雌激素的吸附既存在物理吸附作用,也存在化学降解作用.雌激素化合物的降解主要由于土壤中的有机碳增强了MnO2的导电性能,说明MnO2可以作为土壤固定化剂,能够有效地防止雌激素化合物因解吸作用而形成的"二次污染".     

土壤有机质对菲的吸附-解吸平衡的影响

以自然土壤和过氧化氢分级土壤为实验模拟样品,测定了菲在这些样品上的吸附一解吸等温线,用线性和Freundlich模型拟合了这些等温线．^13C NMR谱表明,随着土壤有机质腐殖化程度的加深,有机质将含有较多的长链烷烃化合物,含氧、氮化合物有所减少,芳香环的数量变化不大．吸附实验结果表明,土壤有机质含量与菲的吸附容量存在一定的线性相关关系．有机质腐殖质化程度较深的样品比原土壤具有更大的吸附容量,其吸附等温线表现出更为明显的非线性,而且具有更明显的解吸滞后现象．说明土壤中一些结构紧密和含极性官能团较少的有机质是引起菲的非线性吸附过程和解吸滞后现象的主要原因。     

莠去津吸附的土壤淋溶柱色谱法研究

采用新发展的土壤淋溶柱色谱法,研究农药在水－土壤体系中的吸附。用土壤装填成液相色谱柱,以农药水溶液为流动相,以除草剂莠去津（２－氯－４－乙胺基－６－异丙胺基－ｓ－三嗪）为例,质量浓度从１９．７３μｇ／Ｌ至２９．６０ｍｇ／Ｌ,紫外检测器监测吸附平衡。吸附相中莠去津的质量浓度经甲醇淋洗液的测定值扣除柱内液相中的质量浓度后得到。对于极稀溶液,可采用在ＯＤＳ柱上富集－液相色谱台阶梯度法测定。莠去津在沙壤土上的吸附行为符合Ｆｒｅｕｎｄｌｉｃｈ方程式,其吸附常数Ｋｆ＝８４２．６ｍＬ／ｋｇ。     

皮胶原纤维对单宁的选择性吸附

用动物皮为原料制备皮胶原纤维吸附材料, 研究了这种吸附材料对单宁的吸附特性. 结果表明, 皮胶原纤维对单宁具有非常好的吸附选择性和高吸附容量, 通过一次吸附, 单宁的去除率可达90%以上, 而其他有效成分损失率小于10%. 单宁在胶原纤维上的吸附属于氢键吸附; 其吸附平衡符合Freundlich方程; 其吸附动力学符合拟二级速度方程.     

酚醛型吸附树脂对咖啡因吸附性能的研究

利用 3种自制吸附树脂JDW 1、JDW 2、JDW 3和DuoliteS 761对咖啡因进行了静态和动态吸附研究 .结果发现 3种自制树脂对咖啡因的吸附性能明显优于DuoliteS 761 ;在吸附咖啡因的初始阶段 ,即达到 3 2 %～5 1 %平衡吸附百分率时 ,吸附速率数据和半经验速率方程很吻合 ,证实吸附咖啡因是粒扩散控制过程 ;酚醛型吸附树脂等温吸附咖啡因的平衡吸附数据符合Langmuir方程 ,相关系数在 0 99以上 ,因此 ,酚醛型吸附树脂吸附咖啡因属单分子层吸附 ;用 1mol LHCl和 40 %的甲醇溶液复合使用 ,效果很好     

活性炭纤维的微孔结构水吸附

测定了两种活性炭纤维（ACF）的氮气、水吸附等温线和XPS,研究了ACF的微孔结构和表面性质,用αs图分析氮吸附等温线获得了ACF的比表面积、微孔容量和微孔径。XPS表明在ACF表面存在多种不同结合状态的氧。水在ACF上的吸附等温线呈V型,具有很大的脱附滞后环。水通过与ACF表面的氧形成氢键发生吸附。ACF表面的初始吸附点多,则在低、中压时的水吸附量就大。     

A New Rapid Determination Method of Soil Organic Carbon Adsorption Coefficients of Pesticides with Soil Column Liquid Chromatography

Recent legislation in many countries requires extensive testing of all manufactured chemicals for environmental evaluation and registration. Among the requirements are water solubility, solvent (usually octanol) - water partition coefficient, soil adsorption and bioconcentration factors in aquatic organisms. Soil adsorption influences the extent of vaporization of a compound from the soil surface and its lateral (run-off) or vertical transport including groundwater contamination. Additionally,…     

五种不同类型土壤中有机化合物土壤吸附系数的预测

为了验证土壤柱液相色谱法测定农药的土壤吸附系数的普遍适用性和预测的准确性,采用了5种组成及性质差异较大、具有一定代表性的土壤样品,对在甲醇 水流动相条件下测定的保留因子与土壤吸附系数间的相关性进行了研究。结果表明,土壤柱液相色谱法是预测农药的土壤吸附系数的一种有效方法,适于多种类型土壤中农药土壤吸附系数的预测。     

Soil Type and Herbicides Adsorption

Abstract

Herbicides behaviour in soils greatly depends on adsorption through its influence on degradation and movement. The adsorption intensity depends on both the chemical structure of pesticides, the nature of soil constituents and soil physico-chemical factors such as the pH. In this paper, the role played by these factors is analysed and used to evaluate the possible use of soil surveys for assessing adsorption behaviour of pesticides in soils. The analysis is based on adsorption measurements of three herbicides (atrazine, terbutryn and 2,4-D) by several soils differing in their mineralogical composition, organic matter content and pH. Using statistical analysis, it is shown that some relations can be defined between soil types and adsorption behaviour. These relations are strongly dependent on the electrical state of the herbicide molecule (cationic, anionic and neutral).     

Mechanisms of Tebuconazole Adsorption in Profiles of Mineral Soils

The study attempted to identify the soil components and the principal adsorption mechanisms that bind tebuconazole in mineral soils. The K_F values of the Freundlich isotherm determined in 18 soils from six soil profiles in batch experiments after 96 h of shaking ranged from 1.11 to 16.85 μg^1−1/n (mL)^1/n g⁻¹, and the exponent 1/n values from 0.74 to 1.04. The adsorption of tebuconazole was inversely correlated with the soil pH. Both neutral and protonated forms of this organic base were adsorbed mainly on the fraction of humins. The adsorption of the protonated form increased in the presence of hydrogen cations adsorbed in the soil sorption sites. Fourier transform infrared spectroscopy coupled with the molecular modeling studies and partial least squares regression analysis indicated that the tebuconazole molecule is bound in the organic matter through the formation of hydrogen bonds as well as hydrophobic and π–π interactions. Ion exchange was one of the adsorption mechanisms of the protonated form of this fungicide. The created mathematical model, assuming that both forms of tebuconazole are adsorbed on the organic matter and adsorption of the protonated form is affected by the potential acidity, described its adsorption in soils well.     

A New Method for Determination of Adsorption and Desorption Coefficients of Pesticides with Soil Column Liquid Chromatography

Agricultural chemicals such as pesticides were extensively applied in the fields. Pesticides effectively protect the crops, only as long as they remain in the root zone of soil. In case a portion of the chemicals leaves root zone and especially leaches through soil pores. They may pollute groundwater and be a serious environmental problem1. This problem has got widespread concern in the world. In soils the fate of organic compounds such as pesticides is governed by hydraulic transport coupled…     

Pressure Effects in Adsorption Systems

A study of the occurrence of large pressure and flow transients when a strongly adsorbed gas is fed to a column which is initially loaded with a lightly adsorbed gas is presented here. Under certain conditions, these transients can cause premature breakthrough and change the shape of the breakthrough curve. This will result in improper estimation of adsorption parameters by the dynamic column loading method and lower apparent adsorption capacity in a full scale unit. A data acquisition system was used to record the pressure and flow transients. An isothermal PDE model developed to study these transients agreed reasonably well with the nonisothermal experimental results. The PDE model predicts that pressure and flow transients will occur during step and pulse~tests conducted to obtain adsorption and mass transfer parameters by the chromatographic method. For instance, lower adsorption capacity will be realized during step tests due to lowering in column pressure. Oscillations were observed when columns are connected in series. The PDE model also predicts these oscillations. Simulations indicate that the extent of oscillations is dependent on the dead volume between columns.     

Multivariate Optimization of Pb2+ Adsorption onto Ethiopian Low-Cost Odaracha Soil Using Response Surface Methodology

Lead pollution is a severe health concern for humankind. Utilizing water contaminated with lead can cause musculoskeletal, renal, neurological, and fertility impairments. Therefore, to remove lead ions, proficient, and cost-effective methods are imperative. In this study, the Odaracha soil which is traditionally used by the local community of the Saketa District was used as a novel low-cost technology to adsorb lead ions. Odaracha adsorbent was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The adsorption process followed the batch adsorption experiment. The response surface method was implemented to derive the operating variables’ binary interaction effect and optimize the process. According to the study’s experimental result, at optimum experimental conditions Odaracha adsorbent removes 98.17% of lead ions. Based on the result of the central composite design model, the Pb²⁺ ion removal efficiency of Odaracha was 97.193%, indicating an insignificant dissimilarity of the actual and predicted results. The coefficient of determination (R²) for Pb²⁺ was 0.9454. According to the factors’ influence indicated in the results of the central composite design model, all individual factors and the interaction effect between contact time and pH has a significant positive effect on lead adsorption. However, other interaction effects (contact time with dose and pH with dose) did not significantly influence the removal efficiency of lead ions. The adsorption kinetics were perfectly fitted with a pseudo-second-order model, and the adsorption isotherm was well fitted with the Freundlich isotherm model. In general, this study suggested that Odaracha adsorbent can be considered a potential adsorbent to remove Pb²⁺ ions and it is conceivable to raise its effectiveness by extracting its constituents at the industrial level.