添加无定形铝氧化物对雷竹林土壤有机质矿化的影响

土壤中无定形铝氧化物对有机质的存在有很大的影响,由于雷竹特殊的经营方式导致土壤中有机质快速积累,为了解无定形铝氧化物对土壤中快速积累的有机质分解产生的影响,本文通过往不同种植年限的雷竹林土壤中增加不同量的无定形铝氧化物(0、2、10、20、40 g/kg)以及室内密闭培养法测定CO2的释放量来反映有机质的分解状况,以便了解无定形铝氧化物对快速增加的雷竹林土壤有机质分解的影响,了解集约经营下的雷竹林土壤有机质的变化趋势及稳定性.结果表明,无定形铝氧化物的加入可显著抑制土壤有机质的分解,当无定形铝氧化物的加入量为40 g/kg时,对0年(水稻)、1年、5年、15年雷竹林土壤有机质分解的抑制率分别为56.97%、60.75%、58.87%、44.25%;0年(水稻)土壤加入无定形铝氧化物0、2、10、20、40 g/kg,对有机质分解的抑制效率分别为7.49%、38.04%、50.79%、56.98%.无定形铝氧化物对有机质分解的抑制效率随其加入量的增加而提高,但随土壤有机质含量的增加而下降.     

菲在不同性质黑炭上的吸附动力学和等温线研究

在300、500和700℃3种条件下加热木屑制备得到3种黑炭,并对其结构和组成进行了表征。通过吸附动力学实验和平衡吸附实验,研究了菲在这些黑炭样品上的吸附动力学和平衡吸附,分别应用拟一阶、拟二阶和叶洛维奇3种动力学模型及Freundlich吸附等温方程对实验数据进行了拟合。结果表明,菲在黑炭样品上的吸附可以分为极快吸附、快吸附和慢吸附3个阶段,拟一阶动力学和叶洛维奇动力学方程仅能对菲在黑炭上吸附动力学的某个阶段拟合较好,而拟二阶动力学模型可较好地拟合菲的整体吸附动力学过程。说明菲在黑炭上的吸附由多个过程控制,水膜扩散、吸附剂颗粒表面扩散和吸附剂内部微孔扩散等多个过程导致了其吸附动力学的复杂性。在快吸附阶段,菲在各个黑炭上吸附动力学的差异,主要受黑炭疏水性影响。Freundlich模型对吸附等温数据的拟合结果进一步证实,多环芳烃菲在黑炭样品上的吸附受多种机制影响。     

有机酸对铝氧化物吸附磷的影响

以存在不同配位阴离子 (硫酸根、磷酸根、草酸根、柠檬酸根 )时合成的铝氧化物为对象 ,用平衡吸附法研究了草酸、柠檬酸等的浓度和 pH对铝氧化物吸附磷的影响 ,并讨论有机酸影响磷吸附的机制。结果表明 :六种合成铝氧化物的最大吸磷量 (Xm)介于 0.189～ 0.838mmol/g ,以Al(OH)x的吸磷量最高 ,铝 柠檬酸复合物 (Al-CA)的吸磷量最低 ;有机酸浓度升高时 ,铝氧化物的吸磷量降低 ,且柠檬酸的影响程度高于草酸 ;先加 pH为 2的草酸或酒石酸 ,Al(OH)x对磷的次级吸附量最低 ,而有机酸pH为 3时 ,Al(OH)x对磷的次级吸附量达最高 ,有机酸溶液 pH由 4增至 9,铝氧化物吸磷量变化不大或逐渐降低。有机酸与磷混合加入同单加磷相比 ,pH 3时差异较小 ,pH 4～ 6时差异最显著 ,pH 7～ 8时又减小 ;有机酸降低铝氧化物吸磷量的机理包括酸性溶解和络合竞争两方面 ,在 pH 2时以前者为主 ,pH 3～ 9时以后者为主 ,且铝氧化物表面的吸附点位对供试配位阴离子都是亲合的     

铁铝氧化物和高岭石对转化酶的吸附及活性的影响

Experiments were conducted to study the influences of synthetic bayerite, non-crystalline aluminum oxide (N-AlOH), goethite, non-crystalline iron oxide (N-FeOH) and kaolinite on the adsorption, activity, kinetics and thermal stability of invertase. Adsorption of invertase on iron, aluminum oxides fitted Langmuir equation. The amount of invertase held on the minerals followed the sequence kaolinite > goethite > N-AlOH > bayerite > N-FeOH. No correlation was found between enzyme adsorption and the specific surface area of minerals examined. The differences in the surface structure of minerals and the arrangement of enzymatic molecules on mineral surfaces led to the different capacities of minerals for enzyme adsorption. The adsorption of invertase on bayerite, N-AlOH, goethite, N-FeOH and kaolinite was differently affected by pH. The order for the activity of invertase adsorbed on minerals was N-FeOH > N-AlOH > bayerite > reak goethite > kaolinite. The inhibition effect of minerals on enzyme activity was kaolinite > crystalline oxides > non-crystalline oxides. The pH optimum of iron oxide- and aluminum oxide-invertase complexes was similar to that of free enzyme (pH 4.0), whereas the pH optimum of kaolinite-invertase complex was one pH unit higher than that of free enzyme. The affinity to substrate and the maximum reaction velocity as well as the thermal stability of combined invertase were lower than those of the free enzyme.     

不同条件下菲和萘在塿土上的吸附特征研究

以平衡吸附法研究了菲和萘在塿土上的吸附行为,考察了初始浓度、温度、pH、离子强度和CaCO3对塿土吸附菲和萘的影响,Henry方程、Freundlich方程和deBoer-Zwikker极化方程被用来拟和吸附等温线。结果表明,菲和萘在塿土上的吸附等温线为非线性,Freundlich方程最符合其吸附行为。菲和萘在塿土上的吸附量随温度升高而降低,其吸附是一个放热过程;吸附自由能小于零,表明吸附过程是自发的;熵变值也小于零,说明焓变是吸附过程的驱动力。随着pH增加,塿土对菲和萘的吸附量下降;而随着离子强度增加,塿土对菲和萘的吸附量增加。CaCO对菲和萘的吸附等温线也为非线性,其对塿土吸附菲和萘具有较大的贡献。     

菲和Cu^2＋在黑垆土上的吸附及其交互影响

采用批平衡法,研究了菲和Cu2＋在黑垆土上的吸附及其交互影响。结果表明,菲和Cu2＋在黑垆土上的吸附动力学曲线较好符合一级动力学方程,菲在黑垆土上的吸附主要通过分配作用,其吸附等温曲线符合线性Henry方程,Cu2＋的存在抑制菲在黑垆土上的吸附;而Cu2＋在黑垆土上的吸附主要通过表面吸附和专性吸附作用,其吸附等温曲线符合Freundlich方程,菲的存在促进了Cu2＋的吸附;对菲和Cu2＋来说,pH均是影响黑垆土吸附的主要因素,黑垆土对Cu2＋的吸附量随着土壤溶液pH值的增加而增加,而对菲的吸附量随着pH增加而降低。     

金属离子在铁(氢)氧化物与腐殖质微界面上的吸附机理和模型研究进展

铁(氢)氧化物和腐殖质是广泛分布在土壤中的重要天然活性物质,因其具有较大的比表面积并且铁(氢)氧化物表面的-OH与腐殖质表面的-COOH、-OH等活性官能团可通过静电作用、配体交换等多种机制对重金属离子产生较强吸附,从而影响重金属离子在环境中的迁移、转化和生物效应。深入了解重金属离子在铁(氢)氧化物-腐殖质复合体微界面相互作用的分子机理,对于阐明重金属离子在环境中的迁移、转化过程具有重要意义。本文综述了金属离子在铁(氢)氧化物与腐殖质上吸附机理和模型的研究进展,为重金属污染土壤的风险评估和控制提供理论依据。     

氧化还原条件下有机物料对酸性土壤pH、铁形态和铜吸附解吸的影响

研究了添加有机物料对水稻土、红壤和砖红壤在干湿交替一次以后土壤pH、铁的形态和对铜吸附解吸行为的影响。结果表明,添加有机物料使得土壤pH升高,且随着有机物料加入量的增加而升高。与对照相比,添加有机物料可使水稻土、红壤和砖红壤的pH分别上升1.55、0.8和1.33个pH单位。红壤和砖红壤中无定形氧化铁含量增加,而水稻土中变化不大。在铜的平衡浓度为0.2 mmol/L时,添加有机物料培养可使水稻土、红壤和砖红壤铜的吸附量分别增加6.7、10.3和3.6 mmol/kg。     

氢离子、三价铝离子、钙离子和铵离子在红壤和黑土上吸附能力的比较

分别用两种混合溶液淋洗红壤和阿斯坎凝膠(濛脱土),以蒸馏水洗去氯离子,然后用1.0NKCl 溶液代换出交换性阳离子并定其量。这两种混合溶液是:(i)CaCl_2+(CH_3COO)_2 Ca+HCl(钙盐浓度一定,HCl 浓度改变);(ii)     

Desorption kinetics of arsenate adsorbed on Al (oxy)hydroxides formed under the influence of tannic acid

Although, much research has been done on arsenate adsorption by Al (oxy)hydroxides, relatively little is known about the kinetics of arsenate desorption from these (oxy)hydroxides, especially those formed in the presence of organic acids. The desorption kinetics of arsenate adsorbed on Al (oxy)hydroxides, formed under the influence of tannic acid, was investigated using 0.1 and 0.5 mM phosphate at pH 5.5 and an ionic strength of 0.01 M at 298 and 318 K. The kinetic data expressed as the mole fraction of the arsenate remaining adsorbed on the Al (oxy)hydroxides after different desorption periods indicated multiple rate characteristics; a fast reaction period from 0.083 to 3 h and a slow reaction period from 3 to 24 h. The second-order rate equation of the six kinetic models tested was chosen to compare the desorption rate of arsenate. The rate constants of arsenate desorption from the Al (oxy)hydroxides formed at different tannate/Al molar ratios (MRs) followed the order: tannate/Al MR of 0 > tannate/Al MR of 0.1 > tannate/Al MR of 0.01 > tannate/Al MR of 0.001 in the fast reaction period, and tannate/Al MR of 0.1 > tannate/Al MR of 0 > tannate/Al MR of 0.01 > tannate/Al MR of 0.001 in the slow reaction period both in 0.1 and 0.5 mM phosphate systems. The data indicate that the Al (oxy)hydroxides formed in the presence of small amounts of tannic acid (tannate/Al MR = 0.001 and 0.01) had a higher adsorption affinity for arsenate and resulted in slower desorption rates of the adsorbed arsenate compared with the Al (oxy)hydroxides formed in the absence of tannic acid. This is ascribed to the tannate-induced structural perturbation, development of microporosity, enhanced specific surface area, and reactivity of the Al precipitates. As the tannate/Al MR increased from 0.001 to 0.1, the rate constants of arsenate desorption steadily increased. This was attributed to the decrease in the point of zero salt effect (PZSE) of the Al precipitates with the increase of the tannate/Al MR and the resultant electrostatic repulsion from coprecipitated tannate which would weaken the binding of arsenate on the Al precipitates. The effect of temperature on the desorption rate of arsenate, which was governed by the activation energy and the pre-exponential factor (collision frequency), varied with the nature of the Al precipitates. The findings obtained in the present study indicate that the relative effects of tannate-induced structural perturbation, enhanced specific surface area, decreased PZSE, and development of micropore structure in the Al (oxy)hydroxides determine the overall impact of tannate on the kinetics of arsenate desorption from these Al (oxy)hydroxides.