小球藻对水溶液中Zn2+、Cd2+的吸附

对小球藻生物吸附Zn^2 ,Cd^2 的影响因素进行了研究,发现小球藻对Zn^2 ,Cd^2 的生物吸附主要经历了快速的物理吸附和缓慢的化学吸附两个步骤;pH值是影响Zn^2 ,Cd^2 生物吸附的一个重要因素,pH值为6-7时,小球藻对Zn^2 ,Cd^2 的去除率较高,在实验条件下去除率可达87%以上;研究还表明,小球藻干粉比新鲜藻能富集更多的Zn^2 ,Cd^2 。用Freundlich方程模拟吸附等温线,拟合良好。     

活性小球藻对铅离子的吸附与解吸特征研究

研究了活性小球藻对Pb^2＋的生物吸附、解吸及其机理。结果表明,培养至指数生长期的小球藻对Pb^2＋的吸附能力最强,吸附率可达75％。吸附液的pH值在7左右,小球藻对Pb^2＋有较好的吸附作用,吸附率可达80％。吸附的动力学实验表明,在小球藻对Pb^2＋吸附的起始阶段,吸附速度较快,10min即可达到平衡。研究还表明,加强光照可以促进小球藻对Pb^2＋的吸附在一定的浓度范围内,小球藻对Pb^2＋的吸附符合Freundlich等温吸附模型。在解吸实验中,用EDTA和HCI作为解吸剂的解吸率可分别达到近80％和60％,可以有效解吸被吸附的Pb^2＋。     

小球藻对U(VI)的生物吸附特性

试验研究了小球藻吸附U(VI)的过程, 探讨了吸附机理、吸附热力学和动力学。考查了pH值、时间、U(VI)的起始浓度和温度等对吸附的影响。研究表明, pH值对小球藻的吸附效果影响较大, 小球藻吸附U(VI)的最佳pH值为6, 最大吸附量为2.7 mg/g, 吸附在5 min内基本达到平衡。小球藻对U(VI)的吸附量与其浓度的正相关; 温度在20℃~30℃时, 对铀的吸附影响不大。实验结果还表明, 吸附过程符合准二级动力学方程, 其相关系数达0.99, 该吸附为多种反应同时作用的复杂过程。U(VI)在小球藻上的吸附行为可以很好地用Langmuir等温方程来描述。     

小球藻对U(VI)的生物吸附特性

试验研究了小球藻吸附U(VI)的过程,探讨了吸附机理、吸附热力学和动力学.考查了pH值、时间、U(VI)的起始浓度和温度等对吸附的影响.研究表明,pH值对小球藻的吸附效果影响较大,小球藻吸附U(VI)的最佳pH值为6,最大吸附量为2.7mg/g,吸附在5min内基本达到平衡.小球藻对U(VI)的吸附量与其浓度的正相关;温度在20℃-30℃时,对铀的吸附影响不大.实验结果还表明,吸附过程符合准二级动力学方程,其相关系数达0.99,该吸附为多种反应同时作用的复杂过程.U(VI)在小球藻上的吸附行为可以很好地用Langmuir等温方程来描述.     

啤酒酵母生物吸附镉的研究

研究了啤酒酵母在游离与固定化条件下对重金属离子Cd^2 的生物吸附特性。灭活的啤酒酵母在适当条件下对Cd^2 有较强的吸附作用,它的吸附能力受到酵母浓度、Cd^2 浓度、pH值和固定化方法等的影响。结果显示：实验条件下,啤酒酵母的最高吸附率达93％,此时的吸附能力为46．5mg Cd^2 ／g干酵母。吸附后用1mol／L的HC1解吸,解吸率达84％。用海藻酸钙凝胶包埋法对啤酒酵母细胞进行固定化,固定化细胞对Cd^2 的吸附主要受到海藻酸钠浓度和Cal2浓度的影响,且凝胶本身对Cd^2 的吸附能力不能忽略。     

小球藻生物富集锌、镉机制的研究

藻类对许多重金属具有较强的生物富集能力,小球藻（Chlorella spp.)分别在不同系列Zn^2 ,Cd^2 浓度下培养8d间隔2d,测定小球藻的生物量及Zn和Cd的含量。结果表明,小球藻随水体中Zn^2 和Cd^2 的浓度不同,在重重金属水体中暴露时间不同,具有不同的富集速率和能力。     

小球藻吸附镍离子的研究

在小球藻液中分别添加含不同浓度的Ni^2 ,NH4^ N,PO4^3--P溶液,研究小球藻吸附Ni2 的能力。实验结果表明,小球藻对Ni^2 的生物吸附经历了一快一慢两个过程。随着Ni^2 的浓度的增加,小球藻对Ni^2 的吸附量不断增加,在最佳pH为8.0-8.5的条件下,低氮磷浓度的组合,升高温度或加强光照有利于小球藻对Ni^2 的吸附。20℃和30℃下,小球藻对Ni^2 的吸附符合Fluendlich等温模型,小球藻在对数生长期时对Ni^2 的富集能力最强。     

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。     

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。     

固定化海洋微藻对污水中Ni2+的吸附

采用海藻酸钠包埋小球藻和叉鞭金藻,制得含藻细胞的固定化胶球,用其对Ni^2 进行生物吸附,研究了固定化小球藻和固定化叉鞭金藻对污水中Ni^2 的吸附率。结果表明：对于同一种固定化微藻,处于对数生长中期时对Ni^2 吸附效果较好,且吸附过程主要在前4h完成;Ni^2 浓度越大,吸附率越高;固定化微藻比悬浮态微藻吸附率高;在相同的实验条件下,固定化小球藻比固定化叉鞭金藻吸附率高。     

Cadmium removal in a biosorption column

New biosorbent material derived from a ubiquitous brown marine alga Ascophyllum nodosum has been examined in packed-bed flow-through sorption columns. It effectively removed 10 mg/L of cadmium down to 1.5 ppb levels in the effluent, representing 99.985% removal. The experimental methodology used was based on the early Bohart and Adams sorption model, resulting in quantitative determination of the characteristic process parameters which can be used for performance comparison and process design. An average metal loading of the biosorbent (N(0)) determined was 30 mg Cd/g, corresponding closely to that observed for the batch equilibrium metal concentration of 10 mg Cd/L. The critical bed depth (D(min)) for the potable water effluent quality standard (0.005 mgg Cd/L) varied with the column feed flow rate (2.4 to 9.6 L/h . cm(2)) from 20 to 50 cm. The sorption column mass transfer and dispersion coefficients were determined, which are also required for solving the sorption model equations. (c) 1994 John Wiley & Sons, Inc.     

Copper,Lead, Cadmium,and Zinc Sorption By Waterlogged and Air-Dry Soil

Competitive sorption of copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn) was studied in three soils of contrasting chemical and physical properties under air-dry and waterlogged conditions. Competitive sorption was determined using the standard batch technique using six solutions, each with Cu, Pb, Cd, and Zn concentrations of approximately 0, 2.5, 5, 10, 20, and 50?mg L^?1Waterlogged soils tended to sorb higher amounts of added Cu, Pb, Zn and Cd relative to soils in the air-dry condition; however, this increase in sorption was generally not statistically (p<0.05) significant. The magnitude of sorption under both waterlogged and air-dry conditions was affected by the type and amount of soil materials involved in metal sorption processes, and competition between other metals for the sorption sites. Metal sorption was closely correlated with soil properties such as cation exchange capacity, organic carbon, and Fe and Mn hydrous oxides. Exchangeable Al may have markedly reduced metal sorption due to its strong affinity for the sorption sites, while increases in exchangeable Mn may have enhanced Zn and Cd sorption. Heavy metal sorption was best described as a combination of both specific and nonspecific interactions. The extractability of Cu, Pb, Cd, and Zn under waterlogged and air-dry conditions was also studied. Three solutions containing these metals were mixed with each soil to achieve a final concentration of 0, 50, and 500?mg kg^?1. Each soil was extracted every 7 days using 1?M MgCl₂ (pH 7) to determine metal extractability. Metal extractability initially decreased then increased due to waterlogging. The increased extractability of added metals was closely related to increased solubility of Fe and Mn suggesting that dissolution of Fe and Mn, oxides under reducing conditions caused a release of previously sorbed Cu, Pb, Cd, and Zn.     

Copper flotation waste from KGHM as potential sorbent for heavy metal removal from aqueous solutions

Sorption affinity of copper flotation waste from KGHM toward Cd(II), Cr(III), Cu(II), and Pb(II) ions was investigated in this work. Batch sorption studies, using single-element synthetic aqueous solutions at various pH (2–12), contact time (10–300 min), initial concentration (100–5000 mg dm^?3; 1–100 mg dm^?3 for Cd(II)) and adsorbent dose (25–200 g dm^?3), were performed. Bonding strength of adsorbed metals was tested from the degree of desorption. The maximum metal removal was observed at pH 5–8, ≥120 min reaction time, and 25 g dm^?3 adsorbent dose. Maximum sorption capacities of studied material were 41.6, 58.8, and 83.8 mg g^?1 for Cr(III), Cu(II), and Pb(II), respectively, for 5000 mg dm^?3 initial concentration, and 0.86 mg g^?1 for Cd(II) for initial concentration of 50 mg dm^?3. Sorption isotherms were very well fitted to Langmuir (Cd, Cr, Pb) and Freundlich (Cu) models. Sorption kinetics was nearly ideally fitted to pseudo-second-order kinetic model. Desorption studies showed that most of Cr(III) (98.5%) and Pb(II) (67.3%) ions remained bound to the surface, indicating that the chemisorption dominated as a controlling process. On the other hand, mostly desorbed were Cd(II) (98.5%) and Cu(II) (90.3%) ions, which indicated that processes like physisorption or precipitation were prevailing.     

Cadmium Sorption Characteristics of Soil Amendments and its Relationship with the Cadmium Uptake by Hyperaccumulator and Normal Plants in Amended Soils

In order to select appropriate amendments for cropping hyperaccumulator or normal plants on contaminated soils and establish the relationship between Cd sorption characteristics of soil amendments and their capacity to reduce Cd uptake by plants, batch sorption experiments with 11 different clay minerals and organic materials and a pot experiment with the same amendments were carried out. The pot experiment was conducted with Sedum alfredii and maize (Zea mays) in a co-cropping system. The results showed that the highest sorption amount was by montmorillonite at 40.82 mg/g, while mica was the lowest at only 1.83 mg/g. There was a significant negative correlation between the n value of Freundlich equation and Cd uptake by plants, and between the logarithm of the stability constant K of the Langmuir equation and plant uptake. Humic acids (HAs) and mushroom manure increased Cd uptake by S. alfredii, but not maize, thus they are suitable as soil amendments for the co-cropping S. alfredii and maize. The stability constant K in these cases was 0.14–0.16 L/mg and n values were 1.51–2.19. The alkaline zeolite and mica had the best fixation abilities and significantly decreased Cd uptake by the both plants, with K ≥ 1.49 L/mg and n ≥ 3.59.     

Impact of Cell Wall Structure on the Behavior of Bacterial Cells as Sorbents of Cadmium and Lead

Batch metal sorption studies were conducted to compare the behavior of Gram-positive Bacillus subtilis and Gram-negative Escherichia coli as sorbents of Cd 2+ and Pb 2+ . A pH range from 3.0 to 6.5 was investigated at total metal concentrations of 1 2 10 -4.0 and 3.2 2 10 -5 M. Concentration apparent equilibrium sorption constants (K s n M ) and sorption capacity (S max n ) values were determined for the bacteria by fitting experimental data to one- ( n = 1) and two-site ( n = 2) Langmuir sorption isotherms. The sorption data for each of the bacteria were described well by a one-site model (r 2 > 0.9), Cd 2+ exhibited somewhat lower sorption affinities (log K s M =- 1.5 for B. subtilis , and -0.7 for E. coli ) than Pb 2+ (log K s M =-0.6 for B. subtilis and -0.8 for E. coli ). Corresponding S max values for Cd 2+ and Pb 2+ on B. subtilis were 0.36 mmole/g and 0.27 mmole/g, respectively. For E. coli Cd 2+ and Pb 2+ S max values were lower at 0.10 mmole/g and 0.21 mmole/g. A two-site sorption model yielded an improved fit for only the E. coli data with several orders of magnitude difference evident between high (Cd 2+ log K s1 M = 0.9; Pb 2+ log K s1 M = 1.5) and low (Cd 2+ log K s2 M =- 1.1; Pb 2+ log K s2 M = -1.6) affinity sorption sites. In addition, allowing for the presence of low affinity sorption (i.e., S max2 ) sites further increased the total E. coli metal sorption capacity closer to that of B. subtilis . As expected, the sorption of Cd 2+ and Pb 2+ by the bacteria exhibited a strong dependence on pH with sorption edges in the range of pH 4.2 to 5.6. The results of this study show that, despite differences in cell wall structure and composition, B. subtilis and E. coli exhibit remarkably similar sorption behavior toward Cd 2+ and Pb 2+ , respectively. These similarities can be attributed to the specific chemical reactivity of acidic functional groups (e.g., carboxyl, phosphoryl) that occur in the cell walls of both bacteria.     

Kinetic studies on the adsorption of Cd2+, Cu2+ and Zn2+ ions from aqueous solutions by cassava (Manihot sculenta Cranz) tuber bark waste

The kinetics of Cd2+, Cu2+ and Zn2+ adsorption onto pure and thioglycolic acid treated cassava tuber bark wastes (CTBW) were investigated using a batch sorption technique at 30 degrees C. Kinetic data suggested that the adsorption process was exothermic, the rate limiting sorption step was physisorption and adsorption rates could be best described by a pseudo-second order model. Rate coefficients were determined to range between 1.39x10(-2)min(-1) and 5.94x10(-2)min(-1), 1.46x10(-3)min(-1) and 5.76x10(-3)min(-1) and 0.69x10(-3)min(-1) and 5.8x10(-3)min(-1) for Cd2+, Cu2+ and Zn2+, respectively. The results from these studies indicated that the sorption process is fast and stable. The adsorption equilibria were evaluated using the Langmuir equation and the monolayer sorption capacity was found to range between 5.88-26.3mg/g, 33.3-90.9 mg/g and 22.2-83.3mg/g for Cd2+, Cu2+ and Zn2+, respectively. Negative values of DeltaG(ads)(0) indicated that the adsorption process was spontaneous and exothermic in nature.     

Moisture Stability of Maltodextrin-Based Delivery Systems

The water sorption isotherms are exploited here for maltodextrin-based perfume-delivery systems with the aim of predicting water vapor stability of the samples at a given temperature. A combination of Couchman (glass-transition temperature) and Guggenheim-Anderson-deBoer (GAB) (fraction of water condensed) models is shown demonstrating important information hidden in a simple sorption experiment (rate of loss of perfume by diffusion and capacity to retain volatiles under humid air conditions). Pure maltodextrin and maltodextrin loaded with apolar and polar perfume components are treated using the same developed methodology. It is shown that apolar molecule release from classical carbohydrate spray dry particles follows a zero-order kinetic. This poster was presented at the 2nd International Symposium on Delivery of Functionality in Complex Food Systems, University of Massachusetts, Amherst, USA. October 8th to 10th, 2007.     

Description of two-metal biosorption equilibria by Langmuir-type models

A biosorbent prepared from Ascophyllum nodosum seaweed biomass, FCAN2, was examined for its sorption capacity. Equilibrium batch sorption studies were performed using two-matal systems containing either (Cu + Zn), (Cu + Cd), or (Zn + Cd). In the evaluation of the two-metal sorption system performance, simple isotherm curves had to be replaced by three-dimensional sorption isotherm surfaces. In order to describe the isotherm surfaces mathematically, three Langmuir-type models were evaluated. The apparent one-parameter Langmuir constant (b) was used to quantify FCAN2 "affinity" for one metal in the presence of another one. The uptake of Zn decreased drastically when Cu or Cd were present. The uptake of Cd wasmuch more sensitive to the presence of Cu than to that of Zn. The presence of Cd and Zn alter the "affinity" of FCAN2 for Cu the least at high Cu equilibrium concentrations. The mathematical model of the two-metal sorption system enabled quantitative estimation of one-metal (bio)sorption inhibition due to the influence of a second metal. (c) 1995 John Wiley & Sons Inc.     

Sorption of lead, cadmium, and zinc on sulfur-containing chemically modified wastes of fluted pumpkin (Telfairia occidentalis Hook f.)

We have tested the applicability of regular as well as sulfanylacetic acid (SA) modified fluted pumpkin waste biomass as adsorbents for Pb2+, Cd2+, and Zn2+ aqueous solutions by means of the batch-sorption technique. The data revealed that SA modification produces a larger surface area, enhancing the metal-ion binding capacity of the biomass. The sorption process was examined by means of Freundlich and Langmuir models. The kinetic study showed that the sorption rates can be described by a pseudo-second-order process. The rate constants for the control biomass (CB) were 2.2x10(-2), 4.4x10(-2), and 1.6x10(-2) mg g(-1) min(-1) for Pb2+, Cd2+, and Zn2+, respectively; and the corresponding rate constants for the SA-modified biomass were 4.0x10(-2), 4.7x10(-2), and 1.7x10(-2) mg g(-1) min(-1), respectively. Thermodynamic considerations indicated a spontaneous exothermic process, which implies that physisorption is the main mechanism in the sorption process.     

Variation in Phosphorus Sorption with Soil Particle Size

Phosphorus (P) is considered a primary cause for surface water eutrophication that leads to anoxia. Understanding the relationships between soil particle size and P sorption helps devise effective best management practices (BMPs) to control P transport by erosion, leaching, and overland flow from agricultural land. Consequently, this study examined the effect of surface soil particle size on the sorption of P in five soil series (four Ultisols and one Entisol) from the Mid-Atlantic region. The sorption of P in each soil was assessed by equilibrating (after shaking for 24?h) 5?g soil containing varied amounts of KH₂PO₄ in 20?mL of 0.01?M KCl solution. Phosphorus in solution was determined by the molybdate blue method of Murphy and Riley. The P adsorption characteristics of these soils were described using the Langmuir isotherm. Results indicated that variability in P sorption was related to particle size and soil type. Soil organic matter content contributed a great deal to P sorption in the Entisol. However, soil clay had influence on the P sorption characteristics of each soil. The maximum P retentive capacities of soils (as determined by Sm from Langmuir equation) and P sorbed at 500?mg P kg^?1 addition showed a linear relationship (r2 = 0.94). Therefore, based on the results obtained, the single point method of Bache and Williams may be appropriate to describe the maximum P sorption capacity of non-sandy soils, as observed in this study.