细菌胞壁多糖对水体中低浓度Pb2+和Cd2+的吸附研究*

室内模拟研究了长春市伊通河天然水环境中优势细菌胞壁多糖对Pb²⁺ 和Cd²⁺ 吸附 ,结果发现 :胞壁多糖对Pb²⁺ 和Cd²⁺ 的吸附量分别在pH为 4 5、 5 0时最大 ;且均分为两个阶段 ,即当pH <4 5 ,对Pb²⁺ 的吸附量与pH呈正相关 ,当pH >4 5时 ,对Pb²⁺ 的吸附量与pH呈负相关 ;对Cd²⁺ 的吸附量在pH <5 0时     

蛋白核小球藻对Pb(Ⅱ)和Cd(Ⅱ)的生物吸附及其影响因素

藻类吸附作用影响重金属在水生生态系统中的迁移过程及其环境行为。同时,利用藻类吸附能力是修复重金属污染水体和重金属废水处理的一项清洁、廉价和高效的技术。测定了蛋白核小球藻对Pb2+和Cd2+的吸附和脱附动力学,表明吸附是快速表面过程,吸附4 h后基本达到平衡,不易脱附。研究了蛋白核小球藻对Pb2+和Cd2+的吸附热力学,绘制了吸附等温线,并用Langmuir模型进行拟合,相关系数R2分别为0.9906和0.9827,计算得到最大吸附量分别为0.373 mmol Pb/g和0.249 mmolCd/g。考察了pH值、离子强度和温度等环境因素对蛋白核小球藻吸附Pb2+和Cd2+的影响。结果表明,蛋白核小球藻对Pb2+和Cd2+的吸附量在pH值5.0—6.0之间达到最大值,并随着溶液离子强度的增加而降低,随着溶液温度的升高而增加。温度的影响还表明,蛋白核小球藻对Pb2+和Cd2+的吸附是吸热过程。实验还考察了水体环境中普遍存在的溶解性有机质主要成分-富里酸的影响,表明富里酸会抑制蛋白核小球藻对Pb2+和Cd2+的吸附,重金属离子浓度较低时的抑制效果更明显,最大抑制率分别达到了34.2%和34.9%。由于其对重金属的较高吸附量和吸附本身快速完成的特性,蛋白核小球藻有望成为较理想的生物吸附剂,在重金属污染水体的生物修复及废水处理中发挥重要作用。     

Pb2+、Cd2+和Ce3+对猪胰α-淀粉酶活性的影响

分别研究了Pb2+、Cd2+和Ce3+对Ca(Ⅱ) α-淀粉酶活性影响及对其Ca2+的竞争作用.结果表明三种金属离子低浓度情况下(0.5～5 mmol/L)对α-淀粉酶具有激活现象,而较高浓度则抑制酶活力.Pb2+、Cd2+和Ce3+竞争置换α-淀粉酶中Ca2+能力的大小是:Pb2+＞Cd2+＞Ce3+,其抑制酶活作用大小:Pb2+＞Cd2+＞Ce3+.     

不同污染负荷土壤中镉和铅的吸附－解吸行为

采用一次平衡法,对3种不同污染负荷土壤Cd2 和Pb2 的吸附-解吸行为进行了比较.结果表明,低污染负荷土壤对Cd2 和Pb2 的吸附能力高于高污染负荷土壤.3种土壤对Cd2 的吸附等温线与Freundlich方程有较好的拟合性,Pb2 的等温吸附过程可用Langmuir方程与Freundlich方程来描述.双常数方程是描述这3种不同污染负荷土壤中Cd2 和Pb2 吸附动力学行为的最优模型,其次为Elovich方程,最差模型是一级动力学方程.Pb2 的解吸滞后现象较Cd2 明显.高污染负荷土壤的吸附态Cd2 、Pb2 解吸率高于低污染负荷土壤,Cd2 、Pb2 解吸量与其初始吸附量之间的关系符合二次幂方程.3种土壤Cd2 、Pb2 的解吸速率随重金属初始浓度的增加而增加,随解吸时间的延长而降低.     

木瓜微粉及其对胆酸钠和重金属吸附特性研究

研究了吸附时间对木瓜微粉吸附胆酸钠的影响,并分别对金属混合液浓度、模拟人体胃肠环境的pH条件、木瓜粉的粒径对木瓜微粉吸附混合液中Cu2+、pb2+、Cd2+、Hg2+的能力进行分析,以明确木瓜微粉及其体外对胆酸钠、Cu2+、Pb2+、Cd2+、Hg2+的吸附特性.结果显示:(1)随粉碎时间的延长,微粉所占的比例增大,粒径分布更加均匀,粉碎过程中存在粉碎一团聚一再粉碎的动态变化.(2)木瓜微粉对胆酸钠的吸附随吸附时间的延长,吸附量显著增加,粗粉和粉碎10、60 min得到的微粉A、C在30 min内对胆酸钠(0.2%)吸附达到了平衡,粉碎30 min得到的微粉B在吸附60 min时对胆酸钠仍有显著的吸附能力.(3)在试验范围内,木瓜微粉B对Cu2+、Pb2+、Cd2+、Hg2+的最适吸附浓度分别为3.00、3.00、1.00、0.01 μg/mL.(4)在pH为7时对Cu2+、Pb2+、Cd2+、Hg2+的吸附率分别比pH为2时高出40.85%、21.07%、27.33%、66.38%.(5)不同粒径的木瓜粉对Cu2+的吸附率随粒径的减小而降低,对Hg2+的吸附率则增加,但对Pb2+和Cd2+的吸附率没有显著差异.研究表明,木瓜微粉在体外具有良好的吸附胆酸钠、Cu2+、Pb2+、Cd2+、Hg2+作用,可广泛用于食品和药品中.     

茶树根细胞壁对铅的吸附作用

以提取的水培茶树龙井43根细胞壁为供试材料,研究了茶树根细胞壁对Pb的吸附作用.结果表明:酸性条件下茶树根细胞壁对Pb的吸附量随着吸附液初始pH值的升高而增大,当初始pH值在2.0~4.5时Pb吸附量快速上升.在吸附液初始pH值为4.5的条件下,当吸附达到平衡时,随着吸附液Pb浓度的提高,茶树根细胞壁对Pb的吸附量增大,其吸附行为更适合用Freundlich吸附模型拟合.当达到吸附平衡时,根细胞壁的Pb吸附总量为9.7mg·g-1,当吸附时间达到320 min时根细胞壁对Pb的吸附量可以达到平衡吸附量的90%,从解吸动力学曲线来看,在60 min时Pb的解吸量可以达到平衡解吸量的50%,吸附、解吸动力学方程更适合用二级速率方程描述.根细胞壁分别经酯化、果胶酶改性、氨基甲基化改性处理后,其对Pb的累积吸附量与未改性处理相比分别降低了51.1%、41.3%和10.8%,表明根细胞壁上的-COOH、半乳糖醛酸多聚物果胶质及-NH2在一定程度上参与了Pb在茶树根细胞壁上的吸附.     

酵母菌Y17吸附Cu2+的影响因素及吸附机理研究

以高效吸附Cu2+的酵母菌Y17为材料, 对其吸附Cu2+过程中的主要影响因素, 包括溶液pH、Cu2+初始浓度、菌体添加量、吸附时间和温度以及吸附机理进行了探讨。结果表明, 对吸附过程影响较大的因素依次为吸附液pH值、Cu2+初始浓度、菌体添加量和吸附时间。正交试验得到最佳吸附条件为溶液pH5.0, 吸附时间40 min, 加菌量5.0 g湿菌/L时, 对初始浓度为8 mmol/L的Cu2+达到最佳吸附率为82.7%。通过对Y17菌体不同处理及解吸实验, 初步确定Y17吸附Cu2+的位点在细胞壁, 细胞壁表面的-NH2, -COOH基团在其吸附过程中起着重要作用。     

小球藻吸附水中Pb2+影响因素的初步研究

对小球藻生物吸附水中Pb2 + 的影响因素作了初步研究。实验表明 :在小球藻处于指数生长期和静止期时加入Pb2 + ,去除率达 6 0 %以上 ;当藻细胞密度一定时 ,随着Pb2 + 浓度的增加 ,Pb2 + 的去除率增大 ;当Pb2 + 浓度一定时 ,随着藻细胞密度的增加 ,小球藻对Pb2 + 的去除率增大 ,藻细胞密度为 1 2 9× 10 8个 /ml时 ,去除率可达 92 82 % ;加强光照可以促进小球藻对Pb2 + 的吸附 ;在pH值为 5～ 10的范围内 ,pH对Pb2 + 吸附影响不大 ,较佳的pH值在 7左右。实验最佳条件的去除率在 90 %以上 ,去除效果较好。     

用EDTA法研究镰刀菌胞内、胞外Pb2+的分布特征

【目的】建立一种方便、快捷、相对准确、能够定量地测定镰刀菌细胞内、外Pb2+分布的技术手段。【方法】用EDTA溶液浸泡镰刀菌细胞,使其胞外(表面)Pb2+被螯合、洗脱并测定,之后将被浸泡、清洗过的细胞消解、测铅。【结果】EDTA可以将镰刀菌表面的Pb2+螯合,且在99 min内不损伤镰刀菌细胞;以EDTA为反应介质和滴定剂,XO为指示剂,测定镰刀菌胞内、胞外Pb2+分布是可行的。依据此实验方法,测定了镰刀菌在Pb2+浓度为500 mg/L的培养基中的生长曲线、培养基中Pb2+浓度和细胞内、外Pb2+的含量。【结论】镰刀菌固定Pb2+的过程是先将Pb2+吸附在菌体胞外,之后转运至细胞内部,菌体胞外Pb2+的容纳量是有限的,每克菌体胞外Pb2+饱和吸附量约1.37 mg,通过计算可得,每克菌体用于吸附Pb2+的胞外活性位点约3.97×1018个。     

紫色土有机质对团聚体吸附-解吸Pb~(2+)的影响

选取名山河流域4种土地利用方式(茶园、旱地、水田、林地)的紫色土为对象,采用平衡液吸附法及NH4OAc、EDTA解吸法研究有机质对Pb2+在全土及各粒径团聚体中吸附-解吸的影响,用Langmuir、Freundlich和Temkin方程对等温吸附过程进行拟合。结果表明:去除有机质前后,4种土地利用方式紫色土全土及各粒径团聚体对Pb2+的吸附量均随Pb2+初始浓度的增大而增加,各粒径团聚体对Pb2+的吸附量排序为(0.002 mm)2~0.25 mm全土0.053~0.002 mm0.25~0.053 mm,Freundlich方程拟合效果最佳,分布系数Kd值与Pd2+初始浓度呈曲线负相关,林地对Pb2+的吸附容量最大,茶园最小;4种土地利用方式紫色土全土及各粒径团聚体以静电吸附方式为主,络合吸附方式为辅,非解吸率大小关系均为林地旱地水田茶园,说明茶园紫色土对Pb2+的固持能力最弱,林地最强。去除有机质后,4种土地利用方式紫色土全土及各粒径团聚体对Pb2+的吸附量均有所降低,相较于茶园和水田,林地和旱地吸附减少量更为明显,Pd2+最大吸附减少量与有机质去除量呈极显著正相关,4种土地利用方式紫色土NH4OAc解吸率明显增加,EDTA解吸率相应减少,非解吸率均有不同程度的降低。     

Equilibrium isotherm studies for the uptake of cadmium and lead ions onto sugar beet pulp

The adsorption of Cd2+ and Pb2+ on sugar beet pulp (SBP), a low-cost material, has been studied. In the present work, the abilities of native (SBP) to remove cadmium (Cd2+) and lead (Pb2+) ions from aqueous solutions were compared. The (SBP) an industrial by product and solid waste of sugar industry were used for the removal of Cd2+ and Pb2+ ions from aqueous water. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, adsorbent dose, initial metal ion concentration, and time on uptake. The sorption process was relatively fast and equilibrium was reached after about 70 min of contact. As much as 70-75% removal of Cd2+ and Pb2+ ions for (SBP) are possible in about 70 min, respectively, under the batch test conditions. Uptake of Cd2+ and Pb2+ ions on (SBP) showed a pH-dependent profile. The overall uptake for the (SBP) is at a maximum at pH 5.3 and gives up to 46.1 mg g(-1) for Cd2+ and at pH 5.0 and gives 43.5 mg g(-1) for Pb2+ for (SBP), which seems to be removed exclusively by ion exchange, physical sorption and chelation. A dose of 8 gL(-1) was sufficient for the optimum removal of both the metal ions. The Freundlich represented the sorption data for (SBP). In the presence of 0.1M NaNO3 the level of metal ion uptake was found to reach its maximum value very rapidly with the speed increasing both with the (SPB) concentration and with increasing initial pH of the suspension. The reversibility of the process was investigated. The desorption of Cd2+ and Pb2+ ions which were previously deposited on the (SBP) back into the deionised water was observed only in acidic pH values during one day study period and was generally rather low. The extent of adsorption for both metals increased along with an increase of the (SBP) dosage. (SBP), which is cheap and highly selective, therefore seems to be a promising substrate to entrap heavy metals in aqueous solutions.     

Potential capacity of Beauveria bassiana and Metarhizium anisopliae in the biosorption of Cd2+ and Pb2+

In this study Beauveria bassiana and Metarhizium anisopliae were used as inexpensive and efficient biosorbents for Pb(II) and Cd(II) from aqueous metal solutions. The effects of various physicochemical factors on Pb(II) and Cd(II) biosorption by B. bassiana and M. anisopliae were studied. The optimum pH for Cd(II) and Pb(II) biosorption by two fungal species was achieved at pH 6.0 for Pb(II) and 5.0 Cd(II) at a constant time of 30 min. The nature of fungal biomass and metal ion interactions was evaluated by Fourier transform infrared. The maximum adsorption capacities (q(max)) calculated from Langmuir isotherms for Pb(II), and Cd(II) uptake by B. bassiana were 83.33±0.85, and 46.27±0.12 mg/g, respectively. However, the q(max) obtained for Pb(II) uptake by M. anisopliae was 66.66±0.28 mg/g, and 44.22±0.13 mg/g for Cd(II). B. bassiana showed higher adsorption capacity compared to M. anisopliae. The data obtained imply the potential role of B. bassiana and M. anisopliae for heavy metal removal from aqueous solutions.     

Removal of lead from aqueous solutions by Penicillium biomass

The removal of lead ions from aqueous solutions by adsorption on nonliving Penicillium chrysogenum biomass was studied. Biosorption of the Pb(+2) ion was strongly affected by pH. Within a pH range of 4 to 5, the saturated sorption uptake of Pb(+2) was 116 mg/g dry biomass, higher than that of activated charcoal and some other microorganisms. At pH 4.5, P. chrysogenum biomass exhibited selectivity for Pb(+2) over other metal ions such as Cd(+2), Cu(+2), Zn(+2), and As(+3) Sorption preference for metals decreased in the following order: Pb > Cd > Cu > Zn > As. The sorption uptake of Pb(+2) remained unchanged in the presence of Cu(+2) and As(+3), it decreased in the presence of Zn(+2), and increased in the presence of Cd(+2). (c) 1993 John Wiley & Sons, Inc.     

Effects of heavy metals Cd2+, Pb2+ and Zn2+ on DNA damage of loach Misgurnus anguillicaudatus

The effects of heavy metals Cd2+, Pb2+ and Zn2+ at 0.05, 0.5 and 5.0 mg/L level and their interactions at 0.5 mg/L level on DNA damage in hepatopancreas of loach Misgurnus anguillicaudatus for 1-35 days exposure were examined by single cell gel electrophoresis (SCGE). For each test group, 20 loaches with similar body size (5.17-7.99g; 11.79-13.21 cm) were selected and kept in aquaria with dechlori-nated water at (22±1)℃ and fed a commercial diet every 48 h. According to the percentage of damaged DNA with tail and its TL/D (tail length to diameter of nucleus) value, the relationship between DNA damage degree and heavy metal dose and exposure time was determined. Results showed that the percentage of damaged DNA and the TL/D value were increased with the prolonged exposure time. The highest percentage (84.85%) of damaged DNA was shown in 5.0 mg/L Zn2+ group after 28 days exposure and the biggest TL/D value (2.50) in all treated groups after 35 days exposure. During the first treated week, the damnification of DNA was mainly recognized as the first level, after that time, the third damaged level was mostly observed and the percentage of damaged DNA was beyond 80%. The joint toxic effects among Cd2+, Pb2+ or Zn2+ revealed much complexity, but it generally displayed that the presence of Cd2+ could enhance the genotoxicity of Pb2+ or Zn2+. In conclusion, the results suggested that there was a significant time-and dose-depended relationship between the heavy metal and DNA damage in hepatopancreas of loach, and SCGE could represent a useful means to evaluate the genotoxicity of environmental contamination on aquatic organisms.     

Biosorption of Cu2+, Cd2+, Pb2+, and Zn2+ using dried marine green macroalga Caulerpa lentillifera

The sorption of Cu2+, Cd2+, Pb2+, and Zn2+ by a dried green macroalga Caulerpa lentillifera was investigated. The removal efficiency increased with pH. The analysis with FT-IR indicated that possible functional groups involved in metal sorption by this alga were O-H bending, N-H bending, N-H stretching, C-N stretching, C-O, SO stretching, and S-O stretching. The sorption of all metal ions rapidly reached equilibrium within 20min. The sorption kinetics of these metals were governed by external mass transfer and intraparticle diffusion processes. The sorption isotherm followed the Langmuir isotherm where the maximum sorption capacities was Pb2+>Cu2+>Cd2+>Zn2+.     

Enhanced and selective adsorption of Pb2+ and Cu2+ by EDTAD-modified biomass of baker's yeast

Enhanced and selective removal of Pb2+ and Cu2+ in the presence of high concentration of K+, Na+, Ca2+ and Mg2+ were achieved by adsorption on biomass of baker's yeast modified with ethylenediaminetetraacetic dianhydride (EDTAD). The modified biomass was found to have high adsorption capacities and fast rates for Pb2+ and Cu2+, and it also displayed consistently high levels of metal uptake over the pH range from 2.7 to 6.0. From Langmuir isotherm, the adsorption capacities for Pb2+ and Cu2+ were found to be 192.3 and 65.0 mg g(-1), respectively, which are about 10 and 14 times higher than that of the unmodified biomass. Competitive biosorption experiments showed that the co-ions of K+, Na+, Ca2+ and Mg2+ had little effects on the uptake of Pb2+ and Cu2+ even at the concentration of 1.0 mol L(-1). The adsorbed Pb2+ and Cu2+ on the modified biomass could be effectively desorbed in an EDTA solution, and the regenerated biomass could be reused repeatedly with little loss of the adsorption capacity.     

Studies of biosorption of Pb2+, Cd2+ and Cu2+ from aqueous solutions using Adansonia digitata root powders

The potentials of Adansonia digitata root powders (ADRP) for adsorption of Pb²⁺, Cd²⁺ and Cu²⁺ from aqueous solutions was investigated. Physico-chemical analysis of the adsorbent (ADRP) shows that hydroxyl, carbonyl and amino groups were predominant on the surface of the adsorbent. Scanning Electron Microscope (SEM) image revealed its high porosity and irregular pores in the adsorbent while the Energy Dispersive X-ray Spectrum showed the major element with 53.0% Nitrogen, 23.8% carbon, 9.1% calcium, 7.5% potassium and 6.6% magnesium present. The found optimal conditions were: initial concentration of the metal ions = 0.5 mg/L, pH = 5, contact time = 90 min, adsorbent dose = 0.4 g and particle size = 32 µm. Freundlich isotherm showed good fit for the adsorption of Pb²⁺, Cd²⁺ and Cu²⁺. Dubinin-Radushkevich isotherm revealed that the adsorption processes were physisorption Cd(II) and Cu(II) but chemisorption with respect to Pb(II) ions. The kinetics and thermodynamic studies showed that Pseudo-second order and chemisorptions provided the best fit to the experimental data of Pb (II) ions only. Batch desorption result show that desorption in the acidic media for the metal ions were more rapid and over 90% of the metal ions were recovered from the biomass.     

Selective transport of Pb2+ and Cd2+ across a phospholipid bilayer by a cyclohexanemonocarboxylic acid-capped 15-crown-5 ether

A cyclohexanemonocarboxylic acid-capped 15-crown-5 ether was synthesized and found to be effective as an ionophore for Pb2+ and Cd2+, transporting them across a phospholipid bilayer membrane. Transport studies were carried out using 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylcholine (POPC) vesicles containing the chelating indicator 2-([2-bis(carboxymethyl)amino-5-methylphenoxy]methyl)-6-methoxy-8-bis(carboxymethyl)aminoquinoline (Quin-2). Data obtained at pH 7.0 using this system, show that the synthetic ionophore transports divalent cations with the selectivity sequence Pb2+ > Cd2+ > Zn2+ > Mn2+ > Co2+ > Ni2+ > Ca2+ > Sr2+. Selectivity factors, based on the ratio of individual initial cation transport rates, are 280 (Pb2+/Ca2+), 62 (Pb2+/Zn2+), 68 (Cd2+/Ca2+), and 16 (Cd2+/Zn2+). Plots of log initial rate versus logM(n+) or log ionophore concentration suggest that Pb2+ and Cd2+ are transported primarily as a 1:1 cation-ionophore complex, but that complexes with other stoichiometries may also be present. The ionophore transports Pb2+ and Cd2+ by a predominantly electrogenic mechanism, based upon an enhanced rate of transport that is produced by agents which dissipate transmembrane potentials. The rate of Pb2+ transport shows a biphasic pH dependence with the maximum occurring at pH approximately 6.5. The high selectivity for Pb2+ and Cd2+ displayed by the cyclohexanecarboxylic acid-capped 15-crown-5 ether suggests potential applications of this ionophore for the treatment of Pb and Cd intoxication, and removal of these heavy metals from wastewater.     

Influence of pH on Cd and Cu uptake, distribution and their effect on nitrate reductase activity in cucumber (Cucumis sativus L.) seedling roots

Influence of different pH solutions (5.0 and 7.0) on Cu²⁺ and Cd²⁺ absorption and distribution in root cells as well as effects of these metals on nitrate reductase activity (NR) in roots of cucumber seedlings were estimated. The absorption of Cu and Cd by roots measured as metal depletion in uptake solution was similar, both metal absorption was independent of the pH of solution. However, after rinsing of roots in distilled water (30 minutes), more Cu than Cd was found in protoplasts of root cells. More Cu was measured in all cell fractions when Cu was uptaken from pH 5.0 than from 7.0. The nitrate reductase activity after one hour of metal treatments was drastically decreased by Cu. The strongest reduction of enzyme activity was observed in roots treated with Cu in buffer with pH 5.0. Influence of Cd on the enzyme activity was weaker and was independent of the pH of solution. Lower concentration of Cd in solution (20 μM) increased NR activity. The data obtained prove the higher mobility of Cu than Cd into the cells of root. The mobility of Cu depends on pH of solution. Cu ions, but not Cd, influenced membrane permeability (K leakage). Cu acted more drasticly than Cd on NR activity.     

Self-association of des-(B26-B30)-insulin. The effect of Ca2+ and some other divalent cations

It has been confirmed by sedimentation equilibrium and sedimentation velocity experiments that des-(B26-B30)-insulin does not self-associate at neutral pH. Sedimentation equilibrium experiments at pH 7, 25 degrees C were conducted to investigate the effects of the structurally and physiologically important divalent cations Zn2+, Cd2+, Pb2+ and Ca2+ on the aggregation state of des-(B26-B30)-insulin (pig) in solution. It was found that all of these ions bring about association of this insulin analogue; Zn2+ and Cd2+ to a more marked degree than Pb2+ and Ca2+. The predominant species in solutions containing Zn2+ appear to be hexamers and hexameric aggregates, in those containing Cd2+, species up to and including tetramers, and in those containing Pb2+ and Ca2+, monomers and dimers of des-(B26-B30)-insulin appear to be the only species present. The possible significance of these findings, especially in relation to a role for Ca2+ in the action of insulin, is discussed.