天然沸石对重金属离子的竞争性吸附研究

通过室内分析的方法研究了天然沸石对4种重金属离子Cd2 、Zn2 、Cu2 、Pb2 的竞争性吸附特性。研究结果表明,与单一离子体系比较,沸石在竞争体系中对Cd2 、Zn2 、Cu2 、Pb2 4种重金属离子的吸附量均呈下降的趋势。竞争体系下,其它重金属离子的存在显著地抑制了沸石对Cd2 的吸附,而对Pb2 的吸附几乎没有影响。天然沸石对4种重金属离子的富集系数,其大小顺序依次为Pb2 >Cu2 >Zn2 >Cd2 。该选择性吸附顺序可能与重金属离子的水合能、离子半径、有效水合离子半径等因素密切相关。     

生物有机肥对重金属的吸附解吸作用的影响

通过室内培养的方法比较了生物有机肥和干鸡粪对重金属离子Pb2+、Cd2+、Cr3+、As6+的吸附与解吸特性。研究结果表明:生物有机肥和鸡粪对4种重金属离子的吸附量大小依次为Cr3+>Pb2+>Cd2+>As6+,解吸量大小顺序为Pb2+>Cd2+>Cr3+>As6+,而解吸率的大小顺序为As6+>Pb2+>Cd2+>Cr3+,这主要与四种金属离子的电荷种类、数量及水合离子半径等密切相关。与干鸡粪相比,生物有机肥增加了对4种重金属离子的吸附率,同时降低了对4种重金属离子的解吸率。     

Cu、Zn、Pb、Cd对鲫鱼(Carassius auratus)组织DNA毒性的研究

用非程序DNA的合成作为毒性评价指标研究了混合重金属对鲫鱼 (carassiusauratus)组织DNA的毒性作用 ,结果表明 ,混合重金属的毒性作用靶标器官是鱼脑和鱼的肝脏 ;混合重金属中的主要毒性成分是Zn、Pb和Cd离子 ,混合重金属对鱼脑组织的毒性大小顺序是Pb>Cd >Zn ,对肝脏DNA的毒性顺序为Pb >Zn >Cd;Cu离子能够降低其它 3种离子的毒性作用 ,降低的机制在于竞争作用 ,导致了其它离子的吸收降低     

不同pH下有机酸对针铁矿和膨润土吸附Cd2+、Pb2+的影响

用平衡吸附法研究了不同pH下,三种有机酸(乙酸、酒石酸和柠檬酸)对针铁矿和膨润土等温吸附Cd2 、Pb2 的影响。结果表明:在加入的Cd2 、Pb2 浓度分别小于0.2 mmol L-1和4.0 mmol L-1时,针铁矿和膨润土吸附平衡体系的pH随加入重金属浓度的增加而降低,膨润土体系的pH降低更明显。在有机酸作用下,pH对针铁矿和膨润土吸附Cd2 、Pb2 的影响差异显著。3酒石酸>乙酸,其对膨润土吸附的影响差异不明显。     

铵饱和沸石对几种重金属离子的吸附解吸特性影响研究

通过室内分析的方法比较了天然沸石及铵饱和沸石对重金属离子Cd2+、Zn2+、Cu2+、Pb2+的吸附及解吸特性。研究结果表明:铵饱和沸石对4种重金属离子的吸附量大小顺序依次为Pb>Cu>Zn>Cd,而解吸量和解吸率的大小顺序为Cd>Zn>Cu>Pb,这主要与四种金属离子的水合离子半径和水合能密切相关。与天然沸石相比,铵饱和沸石一方面增加了对4种重金属离子的吸附,同时又降低了其解吸率。原因是铵饱和沸石的阳离子交换量和比表面积有所增加,同时铵饱和沸石的孔穴和通道也较天然沸石更加均一和畅通。因此,铵饱和沸石在农业生产实践中,特别是土壤污染治理方面具有广阔的应用前景。     

组配改良剂对重金属污染土壤-蔬菜系统的修复效果研究

采用大田实验研究复合污染土壤中添加组配改良剂FQ12(沸石∶羟基磷灰石=1∶2)对受污染土壤和蔬菜中Pb、Cd、Cu、Zn 4种重金属的影响。结果表明,在添加FQ12后,土壤中重金属交换态含量大幅降低。辣椒可食部位中Pb、Cd、Cu、Zn含量也显著降低,FQ12添加量8.0g/kg时降低效果最好,Pb、Cd、Cu分别降低91.1%,58.3%,95.3%;Zn则是在4.0g/kg时,最大降幅达到89.4%,其他部位也有不同程度降低。在添加FQ12后,在一定程度上可以降低空心菜可食部位中Pb、Cd、Cu、Zn含量。在添加量为8.0g/kg时,4种重金属总量均达到最大降幅,最为明显的是Pb和Cu分别降低55.9%和50.7%,根部各重金属含量变化不大。由此可知,FQ12的施用对2种蔬菜吸收土壤重金属起到有效的抑制作用。     

3种改良剂对油菜生物量及其吸收重金属的影响

通过连续三季盆栽试验研究粉煤灰、膨润土、腐殖酸提高油菜生物量,降低油菜Cd、Pb、Cu、Zn浓度的效果。结果表明,膨润土、腐殖酸、粉煤灰的施入提高油菜生物量的效果第二季好于第一、三季。仅考虑对生物量的影响,改良剂效果为膨润土>腐殖酸>粉煤灰。第二季膨润土降低油菜Cd浓度效果较好;第二季粉煤灰、第二季膨润土及第二、三季腐殖酸降低油菜Pb浓度效果较好,3种改良剂均有降低油菜中Pb浓度的效果;3种改良剂均未显著影响油菜中Cu浓度;第二季膨润土降低油菜Zn浓度效果较好。3种改良剂抑制土壤重金属进入油菜的效果不同,应用时可根据改良剂特点适时施入土壤,充分发挥改良剂吸附、固定重金属的作用。     

时间和温度对活性炭与板栗壳吸附铜锌铅镉的影响

随着工业化和城市化进程的加快,废水排放引起的水环境重金属污染问题越来越突出,去除污水中的重金属成为水环境保护的重要内容之一。本文选取活性炭与板栗壳作为吸附剂,研究在不同的时间及温度下,这2种吸附剂对废水中的Cu2+、Zn2+、Pb2+、Cd2+的吸附性能影响。研究发现,活性炭作为吸附剂时,Cu2+吸附量最大是在0.5 h时,Zn2+是在3 h时,Pb2+和Cd2+则是1 h时;用板栗壳吸附时,Cu2+和Pb2+吸附量最大在1 h,Zn2+是在1 h时,Cd2+则是0.5 h时。吸附剂为活性炭或板栗壳,温度对Zn2+的吸附率影响都不大;吸附Cu2+时,活性炭受温度的影响大于板栗壳,其吸附率随温度的升高而减小;Pb2+和Cd2+的吸附受温度影响明显,均是40℃时吸附率较高,但板栗壳>活性炭,且Cd2+>Pb2+。     

胶体存在时不同质地土壤对锌镉的吸附试验研究

以重金属离子Zn和Cd及胶体为对象,通过等温静态批量平衡吸附试验,分析了3种不同质地土壤对Zn、Cd单一吸附和等量竞争吸附特征,胶体对土壤吸附Zn、Cd的影响,并用Langmuir和Freundlich方程对试验结果进行了拟合。结果表明,随着平衡液中Zn2+、Cd2+浓度的增加,土壤对Zn、Cd的吸附量逐渐增大;3种质地土壤对Zn、Cd吸附量顺序为砂壤>粉壤>壤砂土;Zn2+、Cd2+共存时,土壤对这两种离子的吸附量比单一离子存在的情况下明显下降;胶体存在时抑制了土壤对Zn的吸附,促进了土壤对Cd的吸附;就本试验来说,Freundlich方程拟合效果优于Langmuir方程。     

低分子有机酸对土壤中重金属的解吸及影响因素

研究了柠檬酸、草酸、酒石酸和苹果酸对矿区土壤中重金属Pb、Cd、Cu和Zn的解吸行为,并探讨了介质pH值对其解吸土中重金属的影响。振荡解吸试验结果表明四种低分子有机酸对供试污染土壤中Pb、Cd、Cu和Zn都具有一定的解吸能力。由于土壤中重金属有效态含量较低,各重金属的解吸率都不高。在对Pb和Cd的解吸中,各低分子有机酸能力大小顺序为柠檬酸>酒石酸≈苹果酸>草酸;Cu的解吸顺序为柠檬酸>草酸>酒石酸≈苹果酸;Zn的解吸顺序为酒石酸>柠檬酸≈苹果酸>草酸。低分子有机酸随浓度的增加,其解吸能力提高。低分子有机酸对重金属的解吸量随pH值的降低而增加。     

Comparison of Heavy Metal Adsorptions by Thai Kaolin and Ballclay

The adsorption characteristics of heavy metals: cadmium(II), chromium(III), copper(II), nickel(II), lead(II), and zinc(II) ions by kaolin (kaolinite) and ballclay (illite) from Thailand were studied. This research was focussed on the pH, adsorption isotherms of single-metal solutions at 30–60 °C by batch experiments, and on ion selectivityin mixed and binary combination solutions. It was found that, except Ni, metal adsorption increased with increased pH of the solutions and their adsorption followed both Langmuir and Freundlich isotherms. Adsorption of metals in the mixture solutions by kaolin was: Cr > Zn > Cu ≈ Cd ≈ Ni > Pb, and for ballclay was: Cr > Zn > Cu > Cd ≈ Pb > Ni. The adsorption of metals was endothermic, with the exception of Cd, Pb and Zn for kaolin, Cu and Zn for ballclay. Kaolin and ballclay exhibited relatively hard Lewis base adsorption site. The presence of other metals may reduce or promote the adsorption of heavy metals. The presence of Cr³⁺ induced the greatest reduction of metal adsorptiononto kaolin, as did the presence of Cu²⁺ for ballclay.     

贵州草海湿地周边耕地土壤与农作物重金属污染特征

采集草海湿地周边主要农作物可食部分及对应根系的土壤样品,分析测试了重金属Cd,Cr,Hg,Pb,As和Zn的含量,对比研究了土壤和作物中重金属污染水平及对重金属的富集能力。结果表明:土壤重金属元素Zn,As,Cr平均含量未超过贵州省土壤元素背景值,其他3种重金属Pb,Cd,Hg平均值分别是背景值的1.24,1.44,7.5倍;与中国《食品中污染物限量》标准相比,除Hg平均含量超标外,蔬菜中As,Cr,Zn,Cd和Pb平均含量处在可接受范围内。6种重金属的单因子污染指数的高低依次是Hg > Pb > Cd > As > Cr > Zn,葱和萝卜处于安全水平,其余农作物处于警戒线;不同种类作物中重金属富集特征差异较大,菠菜对As,Cd,Hg,Pb的富集系数比其余作物高,萝卜叶对Cr和Zn的富集能力较强,重金属Cr富集系数最低的是玉米,Zn和Hg富集系数最低的是萝卜根,Cd和Pb富集系数最低为马铃薯,As富集能力最低的为白菜。     

THE SPECIFIC ADSORPTION OF DIVALENT Cd, Co, Cu, Pb, AND Zn ON GOETHITE

The specific adsorption of divalent Cd, Co, Cu, Pb, and Zn on goethite is measured as a function of pH. For each mole of heavy metal adsorbed approximately two moles of H+ ions are displaced from the interface. Using these results the heavy metal adsorption data are expressed as functions of the solution concentrations of both H+ and metal ions, and the interfacial reaction is described by the equation, ₂SH+M²⁺= S₂M+₂H⁺. The adsorption data are consistent with an electrochemical model of the simultaneous adsorption of H⁺ ions and divalent metal ions on to the oxide. The intrinsic affinities of the metal ions for the oxide surface increase in the order, Cd < Co < Zn < Pb < Cu. However, besides the affinity of the metal ion for the surface, the adsorption curves are considered to be influenced by surface charge, the adsorption density of the metal ions and their size. The analysis of the data in terms of H⁺ and M²⁺ ion adsorption is considered to be complementary to the hydrolysis model for heavy metal adsorption.     

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.     

几种土壤在单一Zn及Cd Cu共存条件下对Zn的吸附

研究了Zn2+在单一及与Cd2+、Cu2+共存条件下在塿土、黄绵土、黑垆土、黄褐土、砂土5种土壤中的吸附特征,并探讨了其吸附机制。结果表明,在20℃、30℃下,Zn2+在各供试土样中吸附等温线总体上均呈I或III型等温线形式,总体上黑垆土、塿土对Zn2+吸附最强,而砂土的吸附总是最差;塿土、黄绵土和黄褐土中Zn2+吸附的温度效应呈现升温正效应特征,砂土中则总体上表现出随温度上升呈下降趋势,黑垆土中Zn2+吸附的温度效应则与重金属处理有关。Freundlich模型是描述Zn2+吸附等温线最佳模型。Cd2+、Cu2+的共存对Zn2+的吸附均具有显著的拮抗作用,但对Zn2+吸附规律的影响不同。机理分析表明,Zn2+在土壤中的吸附主要以化学吸附为主,Cu2+由于其与Zn2+相似的化学吸附特点而竞争Zn2+化学吸附点位,但Cd2+吸附主要竞争以电性引力形式吸附的Zn2+,因而Cu2+对Zn2+吸附的影响较大,而Cd2+影响较小。     

Comparison of single and competitive metal adsorption by pepper stem biochar

Carbon-based sorbents have been proven to be cost-effective in removing pollutants from wastewater. Biochar from plant residue and agricultural waste is an emerging treatment technology. However, there is a limited number of studies on the effects of various biochar sources on metal adsorption. The aim of this study was using batch experiment to evaluate the adsorption of heavy metals in single- and multi-metal conditions onto pepper stem biochar. The maximum adsorption capacities (mg g^?1) of metals by pepper stem biochar were in the order of Pb (131) ? Cr (76) > Cd (67) > Cu (48) > Zn (31) in the single-metal adsorption isotherm and Pb (91) ? Cu (39) > Cr (29) > Zn (20) > Cd (13) in the multi-metal adsorption isotherm. Lead was the most retained cation, whereas Cr and Cd could be easily exchanged and substituted by other metals (Pb or Cu). For pepper stem biochar, the Langmuir model provided a slightly better fit than the Freundlich model. Results from the batch experiments show that competitive adsorption among metals increases the mobility of these metals. Particularly, Cd adsorption capacity in multi-metal conditions was significantly reduced. Overall, the results suggested that competitive adsorption studies are necessary for obtaining an accurate estimation of the metal retention capacity of pepper stem biochar in natural environments.