恒电荷土壤及可变电荷土壤与离子间相互作用的研究 I.共存离子对NO_3~-吸附的影响

研究了我国典型３种可变电荷土壤和４种恒电荷土壤在陪伴阳离子分别为Ｋ十、Ｎａ十、Ｃａ２＋时和１ｍｍｏｌＬ－１ＫＣ１、Ｋ２ＳＯ４支持电解质中ＮＯ３－的吸附。结果表明，ＮＯ３－吸附量随ｐＨ的增加而减小。在添加相同浓度ＮＯ３－时，３种可变电荷土壤对ＮＯ３－的吸附量顺序为Ｃａ（ＮＯ３）２＞ ＫＮＯ３＞ＮａＮＯ３＞ＫＮＯ３十ＫＣＩ＞ＫＮＯ３＋Ｋ２ＳＯ４；在初始ＮＯ３－浓度０．５－５ｍｍｏｌＬ－１的范围内，吸附量随浓度变化的关系符合Ｌａｎｇｍｕｉｒ等温吸附式．由此求出与ＮＯ３－吸附结合能有关的常数（Ｋ）在不同共存离子存在下数值较小且差异不大，因此认为不同陪伴阳离子和不同伴随阴离子对ＮＯ３－吸附的电性机理影响不大，只是改变了土壤表面的正电荷数量从而使吸附量发生变化。４种恒电荷土壤对ＮＯ３－的吸附量通常很小，其中在Ｃａ（ＮＯ３）２介质中较在其他介质中稍大，最大吸附量仅为１．５～ｍｍｏｌ ｋｇ－１左右，约为可变电荷土壤的１／１０，且在浓度较低时常观察到负吸附。     

可变电荷土壤表面酸碱模型及其计算机模拟

在假定土壤对酸碱的缓冲作用全由表面基团反应所控制的基础上,建立了一个描述可变电荷土壤酸碱滴定曲线的模型,并在计算机上对实验结果进行了模拟。结果表明,本模型可以较好地描述土壤酸碱滴定曲线,提供土壤的酸强度(K_a)和酸容量(S_t),并可进一步提供土壤的酸缓冲容量曲线。本模型对了解和认识土壤酸化和吸附等过程具有一定的意义。     

恒电荷土壤与可变电荷土壤对Cl~-和NO_3~-吸附的差异及其机理

对 3种可变电荷土壤和 4种恒电荷土壤在不同 pH、不同浓度、不同相伴阴阳离子下混合体系中Cl-和NO3-的吸附进行了测定。结果表明 ,在Cl-和NO3- 共存体系中 ,Cl-比例增大使可变电荷土壤Na+吸附量及OH-释放量增加 ,而对恒电荷土壤影响不大。Cl-和NO3-吸附量随平衡Cl-和NO3-浓度增加而增大 ,随pH升高而减少。但恒电荷土壤在上述各种条件下对Cl-和NO3-吸附均相同 ,而可变电荷土壤对Cl-吸附量大于NO3-的吸附量 ;NO3-、Cl-的选择系数为 0.51～0.78,Cl-和NO3-的相对吸附量分别为56.9%和 43.1%。在不同相伴阳离子下 ,可变电荷土壤平衡溶液Cl-/NO3-比值均小于 1,且为Na+K+Ca2+Mg2+Fe3+;而恒电荷土壤Cl-/NO3-比值为 1左右 ,且不受阳离子类型的影响。由此认为 ,Cl-和NO3-在两类土壤中均以电性吸附为主 ,恒电荷土壤对Cl-和NO3-的亲合力及吸附机理相同 ;而可变电荷土壤对Cl-的亲合力 NO3- ,Cl-存在着专性吸附     

离子强度和pH对可变电荷土壤与铜离子相互作用的影响

研究了离子强度和pH对可变电荷土壤表面电荷与铜离子吸附的影响。作为对照 ,也研究了它们对恒电荷土壤黄棕壤的有关性质的影响。结果表明 ,随pH升高 ,土壤的表面负电荷增加 ,正电荷减少。对于可变电荷土壤 ,可出现电荷零点 (pH0 )。随pH升高 ,土壤对Cu2 的吸附量增大。随着离子强度增大 ,恒电荷土壤对Cu2 的吸附百分率明显降低 ,可变电荷土壤对Cu2 离子的吸附百分率也降低 ,但降低的幅度比恒电荷土壤者小得多。土壤中氧化铁的含量越高 ,降低的幅度越小。对于含 2 1 %左右游离氧化铁的铁质砖红壤 ,即使支持电解质NaNO3的浓度高达 1molL- 1,对Cu2 的吸附仍然几乎没有影响。从离子强度和pH与土壤表面电荷和铜离子吸附的关系 ,可以推测在土壤对铜离子的吸附中 ,既存在电性吸附 ,又存在专性吸附。在可变电荷土壤对铜离子的吸附中 ,专性吸附较为重要     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究 Ⅰ.共存离子对NO3-吸附的影响

研究了我国典型3种可变电荷土壤和4种恒电荷土壤在陪伴阳离子分别为K+、Na+、Ca2+时和1mmolL-1KCl、K2SO4支持电解质中NO-3的吸附.结果表明,NO-3吸附量随pH的增加而减小.在添加相同浓度NO-3时,3种可变电荷土壤对NO-3的吸附量顺序为Ca(NO3)2＞KNO3＞NaNO3＞KNO3+KCl＞KNO3+K2SO4;在初始NO-3浓度0.5～5mmolL-1的范围内,吸附量随浓度变化的关系符合Langmuir等温吸附式.由此求出与NO-3吸附结合能有关的常数(K)在不同共存离子存在下数值较小且差异不大,因此认为不同陪伴阳离子和不同伴随阴离子对NO-3吸附的电性机理影响不大,只是改变了土壤表面的正电荷数量从而使吸附量发生变化.4种恒电荷土壤对NO-3的吸附量通常很小,其中在Ca(NO3)2介质中较在其他介质中稍大,最大吸附量仅为1.5mmolkg-1左右,约为可变电荷土壤的1/10,且在浓度较低时常观察到负吸附.     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究 Ⅱ.共存体系中Cl-的吸附特性

对 3种可变电荷土壤和 4种恒电荷土壤在陪伴阳离子分别为Na 、K 、NH 4 、Mg2 、Ba2 、Al3 和共存SO2 -4下Cl- 的吸附量进行了测定。结果表明 ,供试土壤的Cl-吸附量顺序均为AlCl3>BaCl2 和MgCl2 >KCl和NH4 Cl>NaCl,其中可变电荷土壤的差异较大。不同电解质溶液中Cl- 吸附量的顺序与土壤所带正电荷量的顺序一致。Langmuir方程的K值较小 ,且在不同介质中的差异不大。随SO2 -4浓度的增大 ,可变电荷土壤对Cl- 的吸附量减少 ,平衡液的pH值增大 ,而恒电荷土壤则变化甚微 ,说明共存的SO2 -4使可变电荷土壤的表面负电荷增加 ,但对恒电荷土壤则影响不大。这些结果说明 ,Cl- 以电性吸附的机理不因介质而变。可变电荷土壤在一价阳离子存在时 ,除土壤本身所带的正电荷外 ,还有一价阳离子吸附后产生的正电荷以及由此引起的对Cl- 的协同吸附。在二、三价阳离子存在时 ,还有Cl- 的离子对吸附 ,而恒电荷土壤在所有介质中 ,似乎总是以与Cl- 的协同吸附为主     

Estimation of nitrate retention in a Ferralsol by a transient-flow method

Anion retention is important in highly weathered soils that contain large amounts of iron and aluminium oxides with surfaces of variable charge. Sorption mechanisms retard anionic solute transfer through these soils. We determined the retardation factor for nitrate in highly weathered Ferralsols from New Caledonia from dynamic experiments using a transient‐flow method, and we evaluated the effect of soil solution concentration and organic matter content. A simple method with sectionable tubes was used to determine the nitrate isotherm during non‐steady‐state water flow under unsaturated conditions. The topsoil retarded the movement of nitrate, and the sorption followed a linear isotherm. In subsoils, retardation factors were larger and increased from 1.15 to 2.05 at soil pH as the NO₃^–‐N concentration of the input solution decreased from 71.43 to 0.35 mm , indicative of a non‐linear isotherm. Positive surface charge sites were considered to be of two types: one with strong affinity for nitrate at small concentrations and one with weak affinity for adsorption of nitrate at larger concentrations. This type of isotherm with high‐ and low‐energy sites is similar to those found for oxyanions and heavy metals. The related anion exchange capacity was larger than that usually observed in soils of variable charge. Not all exchange sites were detected with our method, and some sites were obviously not available for nitrate retention.     

几种有机酸对恒电荷和可变电荷土壤吸附Cu2+的影响

以恒电荷土壤(黄褐土和黄棕壤)和可变电荷土壤(红壤和砖红壤)为供试材料,研究了乙酸、草酸、酒石酸和柠檬酸对土壤吸附重金属铜离子(Cu2 )的影响。结果表明,在相同酒石酸浓度下,土壤对酒石酸的吸附量依次为黄棕壤(2 1 8mmolkg-1) >红壤(15 4mmolkg-1) >砖红壤(9 5mmolkg-1) ,土壤吸附有机酸后负电荷量增加,相同条件下增幅为砖红壤>红壤>黄棕壤;无有机酸配体时,供试土壤对Cu2 的吸附量为黄褐土>黄棕壤>砖红壤>红壤;加入有机酸时,随有机酸浓度增高,土壤对Cu2 的吸附一般表现为“峰”形曲线,峰所对应的有机酸浓度因有机酸类型而异,且随土壤可变电荷性质增强而增高;土壤吸附有机酸后对Cu2 的次级吸附不同于有机酸与铜共存时的竞争吸附,且因土壤性质表现迥异。这些结果意味着在存在有机酸配体的根际环境中,恒电荷土壤与可变电荷土壤对Cu2 的吸附明显不同,并将影响重金属离子在根际的转化与有效性     

可变电荷土壤中特殊化学现象及其微观机制的研究进展

综述了近年来可变电荷土壤化学研究的进展,着重总结了可变电荷土壤中的盐吸附、铁铝氧化物对土壤自然酸化的抑制作用和离子强度对离子专性吸附的影响等特殊化学现象及其微观机制的研究进展。用颗粒表面扩散层重叠导致有效电荷数量减小的原理解释了盐吸附现象和铁铝氧化物对土壤自然酸化的抑制作用。阐明了可变电荷土壤和矿物中介质离子强度影响离子专性吸附的机制,用四层吸附模型解释了离子专性吸附随离子强度增大而增加的现象,并根据胶体zeta电位随离子强度改变而变化的趋势进一步证明了离子强度增大使胶体专性吸附面上静电电位的绝对值减小,是离子专性吸附随离子强度增大而增加的主要原因。带电颗粒表面双电层结构和双电层相互作用的深入研究,有助于阐明可变电荷土壤中一些特殊化学现象的微观机理,从而进一步完善土壤化学理论。     

Modelling the effect of adsorption of phosphate and other anions on the surface charge of variable charge oxides

Adsorption of anions by iron and aluminium oxides decreases the charge on the surface. However, the negative charge conveyed to the surface by an adsorbed anion varies with the amount of anion adsorbed. This has been explained qualitatively by postulating a mixture of reactions at different surface coverage (Rajan, 1976) or by postulating different reaction mechanisms at different concentrations of phosphate (Ryden & Syers, 1975). We show that these effects may also be reproduced by the adsorption model of Bowden et al. (1974, 1977, 1980). This model does not require a mixture of equations to describe the variations in charge conveyed to the surface. Instead it describes the electrostatic consequences of adsorption. The charge conveyed to the surface by each increment of phosphate differs from that of the previous increment because each successive increment reacts with a surface with a different net charge. The model also reproduces the observed effects of ionic strength and pH on the charge conveyed to the surface by adsorption. Further, it suggests that differences between anions on the charge conveyed to the surface are explicable in differences in the mean distance of the adsorbed anion from the original surface.     

Description of titration curves of mixed materials with variable and permanent surface charge by amathematical model. 1. Theory. 2. Application to mixtures of lepidocrocite and montmorillonite

A model to describe titration curves of mixed materials with variable and permanent charge surfaces is based upon published proposals, but includes the adsorption of potential-determining ions on both kinds of surface, and the influence of the permanent charge. It also considers the interface formed by a system of capacitors in parallel and series. Some typical outputs of the model are given.
The model was tested for mixtures of an iron oxyhydroxide and montmorillonite. The best fit of the model to titration data of the pure materials gave a set of values for the parameters that were used to predict the behaviour of the mixtures. It was concluded that most of the parameters estimated in this way reproduced the behaviour of the mixtures. However, the maximum density of sites on the oxide decreased when the latter was mixed with montmorillonite, and the binding constants of the clay mineral for the p-d ions reached values, intermediate, between those of both minerals when the oxide was present in low proportion. These results suggested that some kind of association occurs between the solid surfaces, which would block part of the oxide surface. However, there is insufficient evidence to confirm this hypothesis.     

CrO42-对两种可变电荷土壤表面电荷的影响

对两种可变电荷土壤的研究结果表明,加入铬酸根(CrO42-)能增加土壤的表面负电荷,减小土壤的表面正电荷的量。CrO42-对表面正电荷的影响程度随体系pH的增加而减小,对负电荷的影响呈相反的趋势。CrO42-对表面电荷的影响程度也随其加入量的增加而增加。CrO42-主要通过自身的吸附来影响土壤的表面电荷,因为伴随着土壤表面电荷的变化,CrO42-在土壤中发生明显的吸附。而且土壤对CrO42-的吸附量随其加入量的增加而增加,随pH的升高而减小,与土壤电荷的变化趋势基本一致。     

EFFECT OF ADSORPTION OF PHENOXYACETIC ACID HERBICIDES ON THE SURFACE CHARGE OF GOETHITE

Surface charge titration measurements, performed on goethite in the presence of absorbed herbicide ions, indicate that the result of adsorption is to cause an increase in the positive charge of the mineral surface. The titration results, used in conjunction with adsorption measurements to calculate the exchange coefficients for the adsorption reactions, show that there is a significant selectivity in adsorption of the herbicides over the indifferent counterion nitrate. This is believed to be due to the existence of favourable van der Waals interactions between the adsorbed herbicide ions.     

The specific adsorption of organic and inorganic phosphates by variable‐charge oxides

We measured the reaction of inorganic phosphate and of four organic phosphates with three aluminium hydroxides or oxides. We compared the fit of the Langmuir equation with that of an equation designed to allow for the feedback effect of adsorption on the electric potential. We also fitted a four‐plane model to describe the effects of pH on adsorption and ζ potential. For inorganic phosphate, the Langmuir equation described adsorption curves poorly, indicating that there was a large feedback effect of adsorption on the electric potential of the adsorption plane. For the organic phosphates, the deviations from the Langmuir equation were not as marked, indicating that there was little feedback effect. Nevertheless, there was a large effect on the ζ potential of the phosphated aluminium (hydr)oxides. We suggest that when a large organic phosphate molecule is adsorbed, the charge conveyed to the surface is repelled electrostatically to the outside of the new surface. There is therefore a large effect on the ζ potential and a small effect on the potential of the adsorption plane. This suggestion was supported by the fit of the four‐plane model, for which, with increasing molecular weight, the mean position of the charge conveyed to the surface by adsorption was moved further from the plane carrying the potential determining ions (H⁺ and OH^?).     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究Ⅲ Cu2+和Zn2+的吸附特征

研究了3种典型可变电荷土壤和4种典型恒电荷土壤在不同pH和不同浓度下单纯及共存体系中Cu2 和Zn2 的吸附及其影响因素。结果表明,两类土壤对Cu2 或Zn2 的吸附量均随平衡浓度增加而增大,符合Langmuir吸附等温式;当Cu2 、Zn2 浓度一定时,pH升高使Cu2 、Zn2 吸附量增大,但当pH >5时,Cu2 、Zn2 吸附量随pH变化甚微,出现一个接近最大吸附量的“平台”。当添加Cu2 、Zn2 浓度相同,但二种离子的总浓度不同时,平衡液的Cu2 /Zn2 浓度比均小于1,说明两类土壤对Cu2 的吸附选择性大于Zn2 ,且这种趋势不因pH和离子浓度而改变。当Cu2 、Zn2 共存时,使可变电荷土壤的Zn2 吸附量减小约70 % ,是恒电荷土壤降低量的约1.5倍;可变电荷土壤吸附一个Cu2 或Zn2 时所释放H 的平均数,明显大于恒电荷土壤者,说明可变电荷土壤对Cu2 及Zn2 的吸附中专性吸附的比例较恒电荷土壤大     

铁锰镁离子改性生物炭对溶液硝态氮的吸附性能研究

为突破生物炭对硝态氮吸附的局限性,以花生壳为原料,在600℃条件下热解制备生物炭(BC),分别用FeCl₃、MnCl₂、MgCl₂对其进行金属负载改性(BC-Fe、BC-Mn和BC-Mg),设计批量吸附试验,结合扫描电镜(SEM)、傅里叶变换红外光谱(FTIR)和X射线衍射(XRD)等进行表征分析。结果表明,铁、锰、镁离子改性使生物炭的比表面积增大6.67~12.16倍,孔容增加3.30~6.00倍,并显著增强了对硝态氮($\text{NO}_{3}^{-}$-N)的吸附性能(P<0.05),吸附量较BC增加11.5%~17.1%,BC-Fe、BC-Mn和BC-Mg对$\text{NO}_{3}^{-}$-N的最大吸附量分别为41.58、39.04、39.58 mg·g^-1,铁、锰、镁离子与炭的最佳质量比分别为0.80、0.20、0.20,铁离子改性效果最好;酸性条件有利于改性生物炭对$\text{NO}_{3}^{-}$-N的吸附,吸附动态符合Langmuir方程(R²=0.935~0.961),吸附过程符合准一级动力学方程(R²=0.971~0.980)。综上,通过金属离子改性,增大了生物炭的比表面积和孔容,优化了表面结构。此外,改性生物炭表面的含氧官能团和金属离子能通过形成氢键或静电作用吸附$\text{NO}_{3}^{-}$-N,进而增强对$\text{NO}_{3}^{-}$-N的吸附能力。本研究结果为生物炭吸附材料的制备及吸附性能优化提供了理论依据。     

Use of a three-plane model to describe charge properties of some iron oxides and soil clays

The pH-dependence of surface charge density of three iron oxides and the clay fraction of five horizons of a variable-charge soil has been studied by adsorption of potential-determining ions (p.d.i.) and by adsorption of electrolyte ions. The general trend of results for iron oxides can be satisfactorily explained by a model which considers a three-plane distribution of electric potential. When the model is applied to soil clays the outcome is less satisfactory and, although their charge properties seem to be largely determined by their high content of minerals with variable charge surfaces, the presence of minerals with a permanent charge (clay minerals) should be considered when explaining the particular data, even for those horizons where clay minerals are present in low proportions.     

Effects of phthalic and salicylic acids on Cu(II) adsorption by variable charge soils

In the present study, the effect of two substituted benzoic acids on Cu(II) adsorption onto two variable charge soils was investigated, with the emphasis on the adsorption and desorption equilibrium of Cu(II). Results showed that the presence of organic acids induced an increase in Cu(II) adsorption onto the two soils. The extent of the effect was related to the initial concentrations of Cu(II) and organic acid, the system pH, and the nature of the soils. The effect of organic acids was greater for Oxisol than for Ultisol. Phthalic acid affected Cu(II) adsorption to a greater extent than salicylic acid did. The effect of organic acids varied with pH. The adsorption of Cu(II) induced by organic acids increased with increasing pH and reached a maximum value at approximately pH 4.5, and then decreased. It can be assumed that the main reason for the enhanced adsorption of Cu(II) is an increase in the negative surface charge caused by the specific adsorption of organic anions on soils because the desorption of Cu(II) adsorbed in organic acid systems was greater than that for the control. The desorption of Cu(II) absorbed in both control and organic acid systems also increased with increasing pH; it reached a maximum value at pH ∼5.25 for control and salicylic acid systems and at pH ∼5.1 for a phthalic acid system, then decreased. This interesting phenomenon was caused by the characteristics of the surface charge of variable charge soils.     

低分子量有机酸对可变电荷土壤和矿物表面化学性质的影响

低分子量有机酸是土壤中广泛存在的,它们参与土壤中许多化学过程,在营养元素活化、解铝毒和矿物风化等方面发挥重要作用。本文综述了可变电荷土壤和矿物对低分子量有机酸的吸附及这类有机酸对土壤的表面电荷、动电性质和土壤吸附无机阴、阳离子的影响,为从事相关研究工作的同志提供参考。     

Analysis of the variable charge of two organic soils by means of the NICA-Donnan model

We have tested to see if the generic set of NICA‐Donnan model parameters, used to describe isolated humic substances, can also describe soil humic substances in situ. A potentiometric back‐titration technique was used to determine the variable surface charge of two organic peat soils at three different ionic strengths. The non‐ideal, competitive‐adsorption NICA‐Donnan model was used to simulate the surface charge, by assuming a bimodal distribution of H⁺ affinity on the soil solid phase. The model provided an excellent fit to the experimental data. The Donnan volume, V_D, varied slightly with ionic strength, although the variation was less than for humic substances in solution. The values obtained for the parameters that define the affinity distributions, the intrinsic proton binding constant (log K_i^int) and the heterogeneity of the site (m_i), were similar to those observed for isolated soil humic acids. The abundance of carboxylic groups in the whole soil represented 30% of the typical value for isolated soil humic acids. The composition of the organic matter of the whole soils, obtained by ¹³C CPMAS NMR, was comparable to the characteristic composition of soil humic acids.