菜园土壤锌的吸附——解吸特性研究

本文研究了菜园土壤锌的吸附 -解吸特性。实验结果表明 ,三种菜园土壤吸附Zn2 + 均随平衡液中Zn2 + 浓度的增加而增大 ,且均可用Langmuir方程和Freundlich方程来描述 ,相关系数均大于 0 .9,达极显著水平。由Langmuir方程求得的菜园土壤对Zn2 + 的最大吸附量的大小顺序为 :黄松土 >粉泥土 >江涂砂 ,但对Zn2 + 的吸附作用力强度和最大缓冲容量的顺序则相反 ,以江涂砂 >粉泥土 >黄松土。菜园土壤对Zn2 + 的解吸量随其吸附量的增加而增加 ,两者之间呈显著线性正相关。     

改性沸石对Zn2+的吸附特性研究

通过间歇震荡平衡法研究了天然沸石及3种改性沸石对Zn2+的吸附特性。研究结果表明,沸石、改性沸石对Zn2+的等温吸附曲线符合Langmuir方程、Freundlich方程、Temkin方程,其中Freundlich方程的拟合性最好,相关系数在0.988～0.999之间。沸石及改性沸石对Zn2+吸附量大小顺序依次为铵改性沸石>钾改性沸石>镁改性沸石>天然沸石。该规律与改性阳离子价数、离子水合半径密切相关。     

不同磷浓度处理暗棕壤对Zn2+吸附解吸行为的研究

通过等温吸附试验,研究不同磷含量处理暗棕壤对Zn2+的吸附解吸行为,结果表明:(1)随平衡液中Zn2+浓度的增加,3种处理暗棕壤对Zn2+的吸附作用均表现为:低浓度下(0～100 mg/L),吸附量增加迅速,随着浓度升高(100～150 mg/L),吸附量变缓并渐趋平衡,含磷量高的土壤吸附Zn2+的量较高。(2)Freundlich、Langmuir和Temkin方程均能很好描述Zn2+在3种不同磷含量暗棕壤上的吸附等温线,拟合效果依次为Freundlich>Langmuir>Temkin。经参数计算,较高磷含量有利于提高暗棕壤的最大吸附量和土壤对Zn2+的缓冲容量,而磷含量不同对Zn2+在暗棕壤上的吸附力没有太大影响。(3)3种不同磷含量处理暗棕壤吸附量与解吸量关系图形状相似,呈高度线性相关,均表现为暗棕壤对Zn2+的解吸量随吸附量的增加而增加,磷含量较高土壤有利于Zn2+的固定且不易解吸。     

不同土地利用方式土壤对铜、镉离子的吸附解吸特征

采用一次平衡法对Cu²⁺、Cd²⁺在城市及城郊农田、林地、草地3种土地利用方式土壤中的吸附解吸过程进行比较研究, 结果表明: Cu²⁺、Cd²⁺在3种土地利用方式土壤中的吸附量均随平衡液浓度的增加而增大, Cu²⁺、Cd²⁺在农田土壤上的吸附量均高于林地和草地土壤。分别用Langmuir和Freunlich两种等温吸附方程对吸附过程进行拟合, 3种土壤对Cu²⁺的吸附过程运用Langmuir方程拟合效果好, 而对Cd²⁺的吸附过程运用Freunlich方程拟合效果更好。Cu²⁺在3种土壤的解吸量大小顺序为农田>林地>草地, Cd²⁺在3种土壤的解吸量大小顺序为农田>草地>林地。两种离子在3种土壤中的动态吸附是个快速反应的过程, 随时间延长, 吸附反应趋于平衡。运用双常数函数方程和Elovich方程能较好地拟合重金属在土壤上的吸附动力学过程。Cu²⁺、Cd²⁺的吸附与土壤黏粒含量、有机质含量、CEC和pH均有关。     

镉在针铁矿、针铁矿-腐植酸复合胶体中吸附解吸行为比较研究

采用批平衡试验法,比较研究了重金属镉在针铁矿和针铁矿-腐植酸复合胶体中的吸附热力学和动力学行为。结果表明,在试验浓度范围内,两种吸附剂对Cd2＋的等温吸附特征均可用Langmuir、Freundlich和Linear方程加以描述。其中以Langmuir方程的拟合效果最佳,线性相关系数为：0.991、0.999,由此推导出的最大吸附量分别为41.667和45.455mg·g^-1,表明腐植酸与针铁矿复合胶体较单一针铁矿的吸附力有所提高,且所吸附的镉均难以解吸,平均解吸率分别为5.871%和1.068%。胶体对Cd^2＋的吸附是一个快速反应过程,4h达到吸附平衡。Elovich方程是拟合吸附动力学过程的最优方程（相关系数分别为0.987和0.997）。通过计算镉在针铁矿和针铁矿-腐植酸复合胶体中的吸附自由能变化量（ΔG的绝对值均〈40kJ·mol^-1）,推测镉在两种胶体中的吸附为物理吸附过程,其吸附机理可能有氢键、偶极作用力和范德华力等作用,而不存在化学键合作用。     

酸性条件下粉砂质壤土对Cd~(2+)的吸附解吸特性研究

为了解酸性条件下粉砂质壤土对Cd2+的吸附-解吸机制,采用一次平衡法进行了不同pH值条件下壤土对Cd2+的吸附-解吸实验。结果表明:壤土对Cd2+的吸附量和吸附率均随着pH值升高而增加,不同初始浓度下达到的最大吸附率为0.69~0.95,酸性条件下壤土对Cd2+的等温吸附Freundlich方程拟合效果最好,通过拟合的Langmuir方程计算出壤土对Cd2+的饱和吸附量为2 500 mg/kg。Cd2+的解吸量和解吸前的吸附量呈显著正相关线性关系,解吸率随着pH值升高而减小,pH值从2以等间隔1变化到6,平均解吸率依次为1.11、0.33、0.07、0.06、0.06;表明在酸性污水灌溉条件下污灌壤土中的镉易向下迁移,污染深层土壤和地下水。     

胶体作用下饱和土壤中Cd运移的数值模拟

通过室内土柱出流实验探讨了饱和壤砂土中Cd在SiO2胶体作用下的运移行为,并用对流-弥散方程(Convection-Dispersion Equation,CDE)对实验结果进行了数值模拟。结果表明,土壤中SiO2胶体的存在抑制了Cd的运移,土壤对Cd的吸附以动力学反应为主。耦合Freundlich等温吸附的单点非平衡模型(One Site Nonequilibrium Model,OSM)能较好地模拟Cd在壤砂土中的运移,模拟得到的吸附特性参数β较小,表明壤砂土吸附表面的不均一性较强。SiO2胶体的穿透时间较早,耦合沉淀-释放反应的CDE模型可以很好地描述SiO2胶体在壤砂土中的运移。胶体作用下的CDE模型成功地模拟了SiO2胶体存在时Cd的运移;同时,参数敏感性分析结果表明,胶体对Cd的吸附速率系数kamc、kaic越小,解吸速率系数kdmc、kdic越大,越有利于Cd的运移。     

膨润土对重金属离子的竞争性吸附研究

通过间歇震荡平衡法研究了膨润土对4种重金属离子Cd2+、Zn2+、Cu2+、Pb2+的竞争性吸附特性及其机制。研究结果表明:与单一离子体系比较,膨润土在竞争体系中对Cd2+、Zn2+、Cu2+、Pb2+4种重金属离子的吸附量均呈下降趋势。竞争体系下,其它重金属离子的存在显著抑制了膨润土对Cd2+的吸附,降幅为19.20%~37.50%,而对Pb2+的吸附能力几乎没有影响,降幅仅为0.41%~2.83%。膨润土对4种重金属离子的富集系数,其大小顺序依次为Pb2+>Cu2+>Zn2+>Cd2+。该选择性吸附顺序与重金属离子的一级水解常数密切相关。     

柠檬酸对黄壤无机纳米微粒吸附-解吸Cd~(2+)的影响

通过超声-离心-冻融的方法,提取名山河流域老冲积黄壤中的纳米微粒(≤100nm),以原土及提取的纳米微粒为研究对象,采用平衡液吸附法及NaNO3、HCl解吸剂解吸法进行室内吸附-解吸模拟试验,研究柠檬酸对黄壤纳米微粒吸附-解吸Cd2+特性的影响。结果表明,纳米微粒对Cd2+的吸附率(94.58%~97.29%)远大于原土对Cd2+的吸附率(45.02%~69.00%),这说明纳米微粒对Cd2+有较强的固持能力;原土及纳米微粒对Cd2+的吸附量随初始Cd2+浓度的增加而明显增加,且低浓度阶段(0.1~1mmol/L)吸附量的增加速率高于高浓度阶段,说明低浓度柠檬酸能促进无机纳米微粒对Cd2+的吸附,而较高浓度的柠檬酸则会抑制Cd2+的吸附;Freundlich、Temkin方程对等温吸附过程的拟合均达到了极显著水平(P0.01),Langmuir方程达到显著水平(P0.05),其中Freundlich方程拟合效果最佳,说明土壤纳米微粒对Cd2+的吸附为多层吸附。通过NaNO3、HCl溶液解吸法可以看出,黄壤无机纳米颗粒对Cd2+的吸附主要以专性吸附为主,非专性吸附质量分数随着Cd2+吸附量增加而增大,而专性吸附质量分数随着Cd2+吸附量增加而减少,原土的专性及非专性吸附解吸率均大于纳米微粒,进一步表明黄壤纳米微粒对Cd2+的固持能力强,有较强的环境缓冲能力。     

土壤对铜的吸附-解吸特征及对土地利用的响应

用吸附平衡法研究黄河三角洲地区土壤对Cu2+的吸附和解吸特征,对比了农田和未利用地土壤吸附与解吸能力的差异,并分析了差异形成的原因。结果表明,土壤对Cu2+的吸附量随着平衡液Cu2+质量浓度的增加而增加,其吸附作用可用Langmuir,Temkin和Freundlich方程来拟合,以Langmuir方程拟合结果最佳。根据Langmuir方程计算出的两种土壤最大吸附量分别为3 961mg/kg和3 521mg/kg,农田土壤对Cu2+的吸附能力强于未利用地土壤;土壤Cu2+的解吸量远远小于土壤对Cu2+的吸附量,与农田土壤相比,未利用地土壤Cu2+的解吸有滞后现象;农田土壤和未利用地土壤Cu2+的解吸率变化范围分别为0.1%～0.35%和0.15%～1.8%,农田土壤的解吸率明显低于未利用地土壤。综合分析认为,两种土壤吸附—解吸特征的差异与农田土壤具有较高的有机质含量,从而在土壤胶体表面形成较多的吸附位点有关。     

安徽凤阳几种土壤对锌的吸附

研究了凤阳县几种土壤吸附锌的性能,讨论了这几种土壤对锌的吸附性能与它们的理化性质的关系。结果表明:供试土壤吸附锌的能力比较接近,土壤吸附锌的量随平衡液浓度的增加而增加,吸附符合Freund lich吸附、Langmu ir吸附和Temk in吸附关系;在土壤质地比较接近的情况下,土壤对锌的最大吸附量与土壤的酸碱度、有机质含量、质地等因素有关。     

Adsorption isotherms of some heavy metals under conditions of their competitive adsorption onto highly calcareous soils of southern Iran

Recently, application of sewage sludge or effluents resulted in raising the concentrations of some heavy metals in some agricultural soils of Iran. Experiments were conducted to evaluate the competitive adsorption of lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd) on six calcareous soils. Adsorption characteristics were evaluated by equilibration of 1 g of each soil sample with 20 ml of 0, 10, 20, 30, 40, 50, 100, or 200 mg L^?1 of their nitrate solutions and 0.01 M NaNO₃ as background electrolyte. Furthermore, solid/liquid distribution coefficients (K_d) of studied metals, as an index of soil capacity to resist a change of the soil solution concentration, were calculated. Results indicated that amounts of adsorbed Pb, Cu, Zn, and Cd increased with increase in their concentrations in the contact solutions, but this trend was more pronounced for Pb and Cu than the others. For all studied soils and metals, Langmuir equation described the adsorption behavior fairly well. Furthermore, Langmuir and Freundlich equation parameters were positively correlated to cation exchange capacity (CEC) and smectite contents; whereas, they were negatively correlated to sand content. Considering K_d values, the selectivity sequence of the metal adsorption was Pb > Cu > Zn > Cd. Therefore, the risk of leaching and also plant uptake of Zn and Cd will be higher as compared to those of the other elements.     

Effect of Calcium on the Soil Adsorption of Cadmium and Zinc in Some Spanish Sandy Soils

Castellón Plain is a natural area with an extension of 464 km², situated in Castellón (eastern coast of Spain), with an important number of ceramic industries which generate waste waters containing cadmium and zinc. In this paper, equilibrium adsorption isotherms have been obtained to examine the behaviour of cadmium and zinc in three selected soils of Castellón Plain (Spain) by means of batch experiments. Both metals exhibit non-linear adsorption isotherms with adsorption maximum beyond the dissolved concentration range considered in this study. Statistical analysis showed that data fit slighty better to Freundlich linearization than that of Langmuir. Adsorption coefficients obtained from Freundlich approximation were calculated to evaluate the relative cadmium and zinc distribution between solution and studied soils obtaining coefficients ranging from 5200 to 5900 μg kg^-1μg l^{-1 -n} for cadmium and from 3500 to 43200 μg kg^-1μg l^{-1 -n} for zinc. The effects of salt concentration and calcium competition for adsorption sites were investigated providing different concentrations of CaCl₂ in background solutions. Adsorption capacities of cadmium and zinc in the studied soils decreased when the salt concentration increased. A tenfold increase in calcium concentration reduced the cadmium adsorption capacity approximately by one third whereas the Ca²⁺ ion does not seem a significant competitor with Zn²⁺ for adsorption sites in soils with high organic matter content, where precipitation of zinc can be expected.     

Ionic strength effect on heavy metal adsorption by soil

Abstract

The adsorption of Cd and Cu by three different soils was studied in the presence of variable concentrations of calcium chloride. Cadmium adsorption fitted the Freundlich equation while Cu better fitted the Langmuir equation. Increasing ionic strength decreased metal adsorption because of the competition of Ca‐ions for the adsorption sites of the soils.

Results could be useful from the standpoint of correct management of sewage sludges and animal slurries applied to agricultural soils because they have an electrolyte concentration greater than that found in normal soil solutions.     

Pb和Cd在塿土不同剖面土壤中的竞争吸附作用

多种金属离子的共存影响土壤对重金属离子的吸附作用,从而影响其生物有效性和迁移特征。利用等温吸附方法研究了塿土不同发育层次土壤对Pb~(2+)、Cd~(2+)单一离子和两种离子共存的吸附特征。对于单一的离子吸附,Pb~(2+)在塿娄土耕层、黏化层和钙积层的分配系数为8.0、8.1和6.1,Langmuir方程最大吸附量为6.1、5.8和6.0 mmol kg~(-1);而Cd~(2+)的分配系数为4.2、7.1和4.7,最大吸附量为5.5、4.8和2.9 mmol kg~(-1);三种土壤对Pb~(2+)的吸附性能均强于对Cd~(2+)的吸附。当Pb~(2+)、Cd~(2+)共存时,两种离子间存在竞争吸附作用,致使Pb~(2+)、Cd~(2+)的吸附量均降低,Pb~(2+)、Cd~(2+)互为竞争性吸附离子的亲和力效应在0.8~0.9之间,竞争性的Langmuir吸附方程可用于描述Pb~(2+)、Cd~(2+)的竞争吸附。     

不同质地土壤中铜离子运移阻滞因子研究

采用等温静态平衡吸附实验确定了重金属铜离子在3种不同质地土壤(砂质壤土,粉砂质粘土,壤质砂土)中的阻滞因子R,然后,结合混合置换实验中测定的铜离子和示踪剂离子的出流动态,采用了确定性平衡对流-弥散方程和确定性非平衡两区对流-弥散方程计算阻滞因子R。结果表明,Langmuir等温线形吸附方程可以准确描述铜离子的吸附特性;确定性平衡模型计算的R值与实测值接近;采用混合置换实验结合对流-弥散方程计算阻滞因子的方法耗时较长,精度不高。     

Adsorption of atrazine and metolachlor in three soils from Blue Creek wetlands, Waterville, Ohio

Atrazine and metolachlor are extensively used pesticides in agricultural activities in northwest Ohio. Adsorption coefficients are often used to model pesticide fate and transport. Many physical-chemical parameters, such as organic matter, clay content, pH, and ionic strength, affect pesticide adsorption. Adsorption kinetics and adsorption isotherms were studied by batch experiment. Effects of humic acid, solution pH, and ionic strength on atrazine and metolachlor adsorption were also approached. After 24 h, both atrazine and metolachlor reached adsorption equilibrium in three local soils. Adsorption isotherms were described by Freundlich equations. The Freundlich coefficient (Kf) ranged from 0.14 to 4.47 (L kg^–1) for atrazine, and 0.04 to 5.30 (L kg^–1) for metolachlor. Adsorption capacity decreased in the order Sloan loam > Del Rey loam > Ottokee fine sand. Koc values varied considerably for both pesticides: metolachlor > in Sloan loam, atrazine metolachlor in Del Rey loam, and atrazine > metolachlor in Ottokee fine sand. In addition to organic matter content, clay played a key role in adsorption in the Del Rey loam and Ottokee fine sand. Higher adsorption was observed at pH 5 for both pesticides. As pH decreased to 3 and increased to 11, adsorption decreased. Adsorption increased as ionic strength increased.     

湖北恩施几种典型土壤对氟的吸附与解吸特性

采用室内试验方法,研究了恩施六种土壤氟吸附的特性。结果表明:(1)不同土壤的吸附量差异很大,表现为黄粘泥水田土>红粘壤土>泥质岩黄壤土>红砂泥水田土>中性紫色土>黑色石灰土;同一土壤的吸附量随氟离子初始浓度的增大而增大。不同土壤的解吸量在低浓度时差异不明显,高浓度时表现为黄粘泥水田土、红粘壤土、泥质岩黄壤土、红砂泥水田土>中性紫色土>黑色石灰土;同一土壤的解吸量随氟离子初始浓度的增大而增大。(2)Langmuir公式可以很好地描述土壤氟吸附的特性,Freundlich公式能够较好地描述土壤对氟的吸附。(3)去除铁、铝氧化物后土壤氟吸附量明显降低;草酸能够促进土壤对氟的吸附;共存PO43-能够抑制土壤对氟的吸附。     

Boron adsorption and desorption in some acid soils of West Bengal,India

Laboratory and greenhouse experiments were conducted to determine the influence of soil properties on adsorption and desorption of boron (B) as well as to estimate the degree of reversibility of adsorption reactions. The utility of Freundlich and Langmuir equations for characterizing the plant availability of applied B in soils was established using soybean [Glycine max (L.) Merr.] as a test crop. The adsorption-desorption study revealed that Fe₂O₃ and clay were primarily responsible for retaining added B in all the 25 different soils under investigation. Organic carbon, pH and cation exchange capacity (CEC) positively influenced the adsorption of B while free Fe₂O₃, organic carbon and clay retarded release of B from these soils. The degree of irreversibility (hysteresis) of B adsorption/desorption increased with increase in organic carbon and CEC of these soils. Freundlich isotherm proved more effective in describing B adsorption in soils as compared to Langmuir equation. The split Langmuir isotherm demonstrated that any of the adsorption maxima, calculated from lower, upper or entire isotherm, could be of practical use. Contrary, bonding energy coefficient, calculated either at lower or higher equilibrium concentration failed to show any practical benefit. Regression models as a function of B application rate and adsorption equation parameters to predict B uptake from applied B, demonstrated the utility of Langmuir and Freundlich equation parameters.