Effect of Heavy Metals (Cd, Cu) on the Gametophytes of Laminaria japonica Aresch

Effects of various concentrations of two heavy metals, namely Cd and Cu, on gametophytes of Laminariajaponica Aresch were determined by recording morphological changes of gametophytes, determining pH values and the heavy metal content of the culture solution, calculating the germination rate of sporophytes, and observing heavy metal (Cd) distribution using a fluorescence microscope. The results showed that heavy metals damaged the gametophytes, and were even lethal, and that the higher the concentration of heavy metal ions, the greater the injury to gametophytes. Gametophytes could not survive in culture solutions containing more than 100 mg/L Cd and 50 mg/L Cu and were only able to survive in culture solution containing a mixture of Cd and Cu up to a concentration of 10 mg/L, which indicates that gametophytes have a higher tolerance to Cd than Cu and that multiple heavy metal ions in solution markedly aggravate the damage to gametophytes compared with individual heavy metal ions. With increases in the concentration of the heavy metal, the burgeoning rate of sporophytes decreased acutely, and solutions containing multiple heavy metal ions caused even more marked harm to sporophytes than solutions containing a single heavy metal ion, because most sporophytes died in mixed solutions. The pH value of the culture medium dropped immediately at the beginning (the first day) of treatment, increased over the following days, and then decreased again. The pH of culture media containing multiple heavy metal ions showed greater variation than media containing a single heavy metal ion, with the extent of the decrease in pH of culture media containing multiple ions being greatest during the last period of the experiment. With increases in the concentration of heavy metals, the capacity of gametophytes to accumulate these ions increased. The blue fluorescent light emitted by the Cd- and Cd-binding protein complex existing in gametophytes in media containing different concentrations of Cd showed clearly the distribution of the ion in gametophytes and the results obtained were consistent with distribution determined using other methods.All results of the present study showed that gametophytes of L. japonica play a remarkable role as heavy metal decontaminators, especially with regard to Cd.     

Heavy metal uptake capacity of fresh water algae (Oedogonium westti) from aqueous solution: A mesocosm research

The green macroalgae present in freshwater ecosystems have attracted a great attention of the world scientists for removal of heavy metals from wastewater. In this mesocosm study, the uptake rates of heavy metals such as cadmium (Cd), nickel (Ni), chromium (Cr), and lead (Pb) by Oedogonium westi (O. westti) were measured. The equilibrium adsorption capabilities of O. westti were different for Cd, Ni, Cr, and Pb (0.974, 0.418, 0.620, and 0.261 mgg^–1, respectively) at 18°C and pH 5.0. Furthermore, the removal efficiencies for Cd, Cr, Ni and Pb were observed from 55–95%, 61–93%, 59–89%, and 61–96%, respectively. The highest removal efficiency was observed for Cd and Cr from aqueous solution at acidic pH and low initial metal concentrations. However, the removal efficiencies of Ni and Pb were higher at high pH and high concentrations of metals in aqueous solution. The results summarized that O. westti is a suitable candidate for removal of selected toxic heavy metals from the aqueous solutions.     

Effect of Heavy Metals （Cd, Cu） on the Gametophytes of Laminaria japonica Aresch

Effects of various concentrations of two heavy metals, namely Cd and Cu, on gametophytes of Laminariajaponica Aresch were determined by recording morphological changes of gametophytes, determining pH values and the heavy metal content of the culture solution, calculating the germination rate of sporophytes, and observing heavy metal （Cd） distribution using a fluorescence microscope. The results showed that heavy metals damaged the gametophytes, and were even lethal, and that the higher the concentration of heavy metal ions, the greater the injury to gametophytes. Gametophytes could not survive in culture solutions containing more than 100 mg/L Cd and 50 mg/L Cu and were only able to survive in culture solution containing a mixture of Cd and Cu up to a concentration of 10 mg/L, which indicates that gametophytes have a higher tolerance to Cd than Cu and that multiple heavy metal ions in solution markedly aggravate the damage to gametophytes compared with individual heavy metal ions. With increases in the concentration of the heavy metal, the burgeoning rate of sporophytes decreased acutely, and solutions containing multiple heavy metal ions caused even more marked harm to sporophytes than solutions containing a single heavy metal ion, because most sporophytes died in mixed solutions. The pH value of the culture medium dropped immediately at the beginning （the first day） of treatment, increased over the following days, and then decreased again. The pH of culture media containing multiple heavy metal ions showed greater variation than media containing a single heavy metal ion, with the extent of the decrease in pH of culture media containing multiple ions being greatest during the last period of the experiment. With increases in the concentration of heavy metals, the capacity of gametophytes to accumulate these ions increased. The blue fluorescent light emitted by the Cd-and Cd-binding protein complex existing in gametophytes in media containing different concentrations of Cd showed clearly the distribution of the ion in gametophytes and the results obtained were consistent with distribution determined using other methods. All results of the present study showed that gametophytes of L. japonica play a remarkable role as heavy metal decontaminators, especially with regard to Cd.     

湿地系统中植物和土壤在治理重金属污染中的作用

重金属污染环境的治理是目前环境工程的核心课题。湿地作为水陆相互作用形成的独特生态系统,在重金属污染治理中的作用倍受关注。对湿地植物、土壤在治理重金属污染中所起的关键作用及其机理做一综述,并对治理重金属污染的湿地构建提出几点建议。     

Assessment of Some Heavy Metals in the Dead Sea Mud and Treatment Optimization

This paper describes the experimental remediation of the Dead Sea mud and the quantitative determination of some heavy metals. Herein, two chelating agents were employed as extracting aqueous solution: ethylenediaminetetraacetic acid (EDTA) and citric acid. The study focused on the main known heavy metals that were reported previously to be in the Dead Sea mud, which are Co, Ni, Pb, Zn, and Cr. Findings had indicated that citric acid was efficient in the removal of the aforementioned heavy metals. Physicochemical parameters that were expected to affect the removal of metals in the Dead Sea mud were optimized. Those parameters were the chelating agent concentration, mixing time and speed, type of washing water, temperature, and pH. The results showed that the best removal of heavy metals from Dead Sea mud can be achieved under optimum citric acid concentration, 1.5 g/50 mL for treatment of 10 g mud. Optimum mixing speed and time were found to be 800 rpm and 1 hr, respectively. Regarding washing water, it was found that the use of the same water for repeated washing provided better removal percentages. pH values and temperature had effect on removal percentages of the heavy metals from mud. However, working at pH 7 and room temperature would provide convenient results for heavy metal removal.     

Effects of moisture content and initial pH in composting process on heavy metal removal characteristics of grass clipping compost used for stormwater filtration

Heavy metals are common contaminants in stormwater runoff. One of the devices that can be used to effectively and economically remove heavy metals from runoff is a yard waste compost stormwater filter. The primary goal of composting is to reduce waste volume rather than to produce stormwater filter media. Moisture content (MC) and initial pH, the two important parameters in composting, were studied for their effects on yard waste volume reduction and heavy metal adsorption performances of the compost. The main objective of this investigation was to examine whether the conditions that provided high yard waste volume reduction would also result in compost with good heavy metal removal performances. Manila grass was composted at different initial pHs (5–9) and MCs (30–70%) and the composts were used to adsorb cadmium, copper, lead and zinc from water. Results indicated that MC is more critical than initial pH for both volume reduction and production of compost with high metal adsorption performances. The most optimal conditions for the two attributes were not exactly the same but lower MCs of 30–40% and pH 7 or higher tended to satisfy both high volume reduction and effective metal adsorption.     

Biosorption of copper(II) and cobalt(II) from aqueous solutions by crab shell particles

Biosorption of each of the heavy metals, copper(II) and cobalt(II) by crab shell was investigated in this study. The biosorption capacities of crab shell for copper and cobalt were studied at different particle sizes (0.456-1.117 mm), biosorbent dosages (1-10 g/l), initial metal concentrations (500-2000 mg/l) and solution pH values (3.5-6) in batch mode. At optimum particle size (0.767 mm), biosorbent dosage (5 g/l) and initial solution pH (pH 6); crab shell recorded maximum copper and cobalt uptakes of 243.9 and 322.6 mg/g, respectively, according to Langmuir model. The kinetic data obtained at different initial metal concentrations indicated that biosorption rate was fast and most of the process was completed within 2h, followed by slow attainment of equilibrium. Pseudo-second order model fitted the data well with very high correlation coefficients (>0.998). The presence of light and heavy metal ions influenced the copper and cobalt uptake potential of crab shell. Among several eluting agents, EDTA (pH 3.5, in HCl) performed well and also caused low biosorbent damage. The biosorbent was successfully regenerated and reused for five cycles.     

Constructed wetlands for waste water treatment: the use of laterite in the bed medium in phosphorus and heavy metal removal

In Northern Ireland, phosphorus enrichment of lakes due to agriculture is a significant problem. Heavy metal exports from landfill sites, often located on water-logged land, are also of concern. Locally available laterite, a low grade bauxite which is rich in iron and aluminium, is used in acid solution with subsequent precipitation to remove phosphorus and heavy metals at several sewage treatment works. Constructed wetlands offer an attractive alternative to conventional waste water treatment in certain circumstances but removal of phosphorus is strongly dependent on the bed medium. Calcium-, iron- and aluminium-rich solid media are recommended. A brief introduction to the use and cost-effectiveness of constructed wetlands (CWs) in treating a range of effluents is given. This study, using both laboratory tests and pilot-scale constructed wetlands, reports the effectiveness of granular laterite in removing phosphorus and heavy metals from landfill leachate. Initial laboratory studies have shown that laterite is capable of 99% removal of phosphorus from solution. A pilot-scale experimental CW containing laterite achieved 96% removal of phosphorus. This removal is much greater than that reported in other systems. Initial removals of aluminium and iron by pilot-scale CWs have been up to 85% and 98% respectively. Percolating columns of laterite reduced Cd, Cr and Pb to undetectable concentrations. Possible application of this low cost, low technology, visually unobtrusive yet efficient system to rural areas with dispersed point sources of pollution is discussed.     

Cocoa shells for heavy metal removal from acidic solutions

The development of economic and efficient processes for the removal of heavy metals present in acidic effluents from industrial sources or decontamination technologies has become a priority. The purpose of this work was to study the efficiency with which cocoa shells remove heavy metals from acidic solutions (pH 2) and to investigate how the composition of these solutions influences heavy metal uptake efficiency. Adsorption tests were conducted in agitated flasks with single-metal solutions (0.25 mM Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn), multi-metal solution (comprised of 0.25 mM of each of the cations above) and an effluent obtained from chemical leaching of metal-contaminated soil, in the presence of different cocoa shell concentrations (5–40 g/l). Results from the single-metal solution assays indicated that the fixation capacity of heavy metals by cocoa shells followed a specific order: Pb > Cr > Cd=Cu=Fe > Zn=Co > Mn=Ni=Al. Cocoa shells are particularly efficient in the removal of lead from very acidic solutions (q_max=6.2 mg Pb/g, pH_i=2.0 and T=22 °C). The presence of other metals and cations in solution did not seem to affect the recovery of lead. It was also observed that the maximum metal uptake was reached in less than 2 h. This research has also demonstrated that the removal of metals caused a decline in solution proton concentration (pH increase) and release of calcium, magnesium, potassium and sodium from the cocoa shells.     

Comparison of Extractants for Removing Heavy Metals from Contaminated Clayey Soils

This article describes the removal of heavy metals from contaminated clayey soils by soil washing using various extractants. Two clayey soils, kaolin, a low buffering soil with pH of 5, and glacial till, a high buffering soil with pH of 8, were used to represent various soil conditions. These soils were spiked with chromium (Cr), nickel (Ni), and cadmium (Cd) to simulate improper disposal of typical electroplating waste constituents. The following extracting solutions were investigated for the removal of heavy metals from the soils: deionized water, distilled water, and tap water; acetic acid and phosphoric acid; chelating agents ethylenediaminetetraacetic acid (EDTA) and citric acid; and the oxidizing agents potassium permanganate and hydrogen peroxide. The effect of extractant concentration on removal of heavy metals was also investigated. Complete removal of Cr was achieved using 0.1?M potassium permanganate for kaolin, while a maximum of 54% was removed from glacial till. A maximum Ni removal of 80% was achieved using tapwater for kaolin, while a maximum removal of 48 to 52% was achieved using either 1?M acetic acid or 0.1?M citric acid for glacial till. A maximum Cd removal of 50% was achieved using any of the extractants for kaolin, while a maximum removal of 45 to 48% was obtained using either acids or chelating agents for glacial till. Overall, this study showed that complete removal of Cr, Ni, and Cd from clayey soils is difficult to achieve using the soil-washing process, and also the use of one extractant may not be effective in removing all metals. A sequential extraction using different extractants may be needed for the removal of multiple metal contaminants from clayey soils.     

A New Method for Mercury Removal

A method is desibed for the removal of mercury from solution by using the off-gas produced from aerobic cultures of Klebsiella pneumoniae M426. Cells growing in Hg-supplemented medium produced a black precipitate containing mercury and sulphur. The ratio of Hg:S was determined as ~1:1 by analysis using proton-induced X-ray emission, suggesting precipitation of HgS within the culture. The outlet gases produced by a mercury-unsupplemented aerated culture were bubbled into an external chamber supplemented with up to 10 mg HgCl₂/ml. A yellowish-white precipitate formed, corresponding to 99% removal of the mercury from solution within 120 min. Energy dispersive X-ray microanalysis showed that this metal precipitate consisted of mercury, carbon and sulphur. Formation of mercury carbonate was discounted since similar precipitation occurred at pH 2 and no oxygen was detected in the solid, which gave an X-ray powder pattern suggesting an amorphous material, with no evidence of HgS. Precipitation of mercury with a volatile organosulphur compound is suggested. Bio-precipitation of heavy metals by using culture off-gas is a useful approach because it can be used with concentrated or physiologically incompatible solutions. Since the metal precipitate is kept separate from the bacterial biomass, it can be managed independently.     

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。     

Biosorption of Chromium(VI) and Lead(II): Role of Spirulina platensis in the Treatment of Industrial Effluent

Biosorption is the process of removal of any chemical molecules by the treatment of biological material. Industrialization resulted in the discharge of various toxic heavy metals into water bodies, which poses serious health hazards to humans and animals. In the present study, live Spirulina platensis was used as a biosorbent for the removal of the heavy metals chromium (Cr(VI)) and lead (Pb(II)) from the aqueous samples. S. platensis were cultured in the presence of different concentrations of heavy metals. The growth of the algal cells was found to be decreased by 59% and 36% in media containing 50 ppm Cr(VI) and Pb(II), respectively. To assess the biosorption of heavy metals, at different time intervals, the spent culture media were used to detect Cr(VI) by atomic absorption spectroscopy method and Pb(II) by 4-(2-pyridylazo)resorcinol indicator method. Results suggested that there was a significant uptake of Cr(VI) and Pb(II) from the medium by S. platensis, with corresponding decrease of metals in the medium. When metal salt solutions or industrial effluent samples were passed through the column containing immobilized live S. platensis in calcium alginate beads, the concentration of Cr(VI) was found to be reduced drastically. The present study indicates the application of S. platensis for the bioremediation of heavy metals from the samples obtained from industrial effluents.     

Bioleaching of Heavy Metal Polluted Sediment: Influence of Sediment Properties (Part 2)

A remediation process for heavy metal polluted sediment has previously been developed, in which the heavy metals are removed from the sediment by solid‐bed bioleaching using sulfuric acid as a leaching agent arising from added elemental sulfur (S⁰). This process has been engineered with Weiße Elster River sediment (dredged near Leipzig, Germany), as an example. Here, six heavy metal polluted sediments originating from various bodies of water in Germany were subjected to bioleaching to evaluate the applicability of the developed process on sediment of different nature: each sediment was mixed with 2 % S⁰, suspended in water and then leached under identical conditions. The buffer characteristics of each sediment were mainly governed by its carbonate and Ca content, i.e., by its geological background, the redox potential and oxidation state depended on its pre‐treatment (e.g., on land disposal), while the pH value was influenced by both. The added S⁰ was quickly oxidized by the indigenous microbes even in slightly alkaline sediment. The microbially generated H₂SO₄ accumulated in the aqueous phase and was in part precipitated as gypsum. Significant acidification and heavy metal solubilization only occurred with sediment poor in buffer substances. With the exception of one sediment, the behavior in bioleaching correlated well with the behavior in titration with H₂SO₄. Since the content in carbonate seemed to be the most important factor deciding on the leachability of a sediment, oxic Weiße Elster River sediment was mixed with 2 % S⁰ and 0 to 100 g/kg of ground limestone to simulate various buffer capacities, suspended in water and then leached. The lime did not inhibit microbial S⁰ oxidation but generated a delay in acidification due to neutralization of formed H₂SO₄, where the pH only started to decrease when the lime was completely consumed. The more lime the sediment contained, the longer this lag period lasted, and the higher the pH and the lower the fraction of the solubilized heavy metals finally was. Since Cu requires stronger acidic conditions for its solubilization, it responded more sensitively to lime addition than Zn, Ni, and Cd. Heavy metal polluted sediment containing large amounts of carbonate may, in principle, also be remediated by bioleaching, but metal solubilization requires excessive amounts of the leaching agent and is thus uneconomical.     

Biosorption of lead(II), cadmium(II), copper(II) and nickel(II) by anaerobic granular biomass

Biosorption is potentially an attractive technology for treatment of wastewater for retaining heavy metals from dilute solutions. This study investigated the feasibility of anaerobic granules as a novel type of biosorbent, for lead, copper, cadmium, and nickel removal from aqueous solutions. Anaerobic sludge supplied from a wastewater treatment plant in the province of Quebec was used. Anaerobic granules are microbial aggregates with a strong, compact and porous structure and excellent settling ability. After treatment of the biomass with Ca ions, the cation exchange capacity of the biomass was approximately 111 meq/100 g of biomass dry weight which is comparable to the metal binding capacities of commercial ion exchange resins. This work investigated the equilibrium, batch dynamics for the biosorption process. Binding capacity experiments using viable biomass revealed a higher value than those for nonviable biomass. Binding capacity experiments using non-viable biomass treated with Ca revealed a high value of metals uptake. The solution initial pH value affected metal sorption. Over the pH range of 4.0-5.5, pH-related effects were not significant. Meanwhile, at lower pH values the uptake capacity decreased. Time dependency experiments for the metal ions uptake showed that adsorption equilibrium was reached almost 30 min after metal addition. It was found that the q(max) for Pb2+, Cd2+, Cu2+, and Ni2+ ions, were 255, 60, 55, and 26 mg/g respectively (1.23, 0.53, 0.87, and 0.44 mmol/g respectively). The data pertaining to the sorption dependence upon metal ion concentration could be fitted to a Langmiur isotherm model. Based on the results, the anaerobic granules treated with Ca appear to be a promising biosorbent for removal of heavy metals from wastewater due to its optimal uptake of heavy metals, its particulate shape, compact porous structure, excellent settling ability, and its high mechanical strength.     

Bioremediation of Heavy Metals in Liquid Media Through Fungi Isolated from Contaminated Sources

Wastewater particularly from electroplating, paint, leather, metal and tanning industries contain enormous amount of heavy metals. Microorganisms including fungi have been reported to exclude heavy metals from wastewater through bioaccumulation and biosorption at low cost and in eco-friendly way. An attempt was, therefore, made to isolate fungi from sites contaminated with heavy metals for higher tolerance and removal of heavy metals from wastewater. Seventy-six fungal isolates tolerant to heavy metals like Pb, Cd, Cr and Ni were isolated from sewage, sludge and industrial effluents containing heavy metals. Four fungi (Phanerochaete chrysosporium, Aspegillus awamori, Aspergillus flavus, Trichoderma viride) also were included in this study. The majority of the fungal isolates were able to tolerate up to 400 ppm concentration of Pb, Cd, Cr and Ni. The most heavy metal tolerant fungi were studied for removal of heavy metals from liquid media at 50 ppm concentration. Results indicated removal of substantial amount of heavy metals by some of the fungi. With respect to Pb, Cd, Cr and Ni, maximum uptake of 59.67, 16.25, 0.55, and 0.55 mg/g was observed by fungi Pb3 (Aspergillus terreus), Trichoderma viride, Cr8 (Trichoderma longibrachiatum), and isolate Ni27 (A. niger) respectively. This indicated the potential of these fungi as biosorbent for removal of heavy metals from wastewater and industrial effluents containing higher concentration of heavy metals.     

Removal of cadmium from aqueous system by shelled Moringa oleifera Lam. seed powder

The present study explores the unexploited sorption properties of the plant Moringa oleifera Lam. for decontamination of Cd at laboratory scale. Sorption studies using standard practices were carried out in batch experiments as functions of biomass dosage, contact time, metal concentrations, particle size and pH. Percentage sorption in each case was computed on the basis of Cd estimation using a planar NaI (TI) detector coupled to a 4K MCA (Canberra Accuspec Card with PC-AT 386). The adsorption data accurately in a Freundlich isotherm. Sorption studies resulted in the standardization of optimum conditions for removal of Cd (85.10%) as follows: biomass dosage (4.0 g), metal concentration (25 microg/ml), contact time (40 min) and volume of the test solution (200 ml) at pH 6.5. Fourier transform infrared (FTIR) spectrometry highlighted amino acid-Cd interactions responsible for sorption phenomenon. The findings open up new avenues in the removal of toxic metals by shelled Moringa oleifera seeds (SMOS) from water bodies as low cost, domestic and environmentally friendly safe technology.     

Lead,cadmium and nickel removal efficiency of white-rot fungus Phlebia brevispora

Widespread of heavy metals contamination has led to several environmental problems. Some biological methods to remove heavy metals from contaminated wastewater are being widely explored. In the present study, the efficiency of a white-rot fungus, Phlebia brevispora to remove different metals (Pb, Cd and Ni) has been evaluated. Atomic absorption spectroscopy of treated and untreated metal containing water revealed that all the metals were efficiently removed by the fungus. Among all the used metals, cadmium was the most toxic metal for fungal growth. Phlebia brevispora removed maximum Pb (97·5%) from 100 mmol l⁻¹ Pb solution, which was closely followed by Cd (91·6%) and Ni (72·7%). Scanning electron microscopic images revealed that the presence of metal altered the morphology and fine texture of fungal hyphae. However, the attachment of metal on mycelia surface was not observed during energy-dispersive X-ray analysis, which points towards the intracellular compartmentation of metals in vacuoles. Thus, the study demonstrated an application of P. brevispora for efficient removal of Pb, Cd and Ni from the metal contaminated water, which can further be applied for bioremediation of heavy metals present in the industrial effluent.     

Removal of cadmium from aqueous solution by Nordmann fir (Abies nordmanniana (Stev.) Spach. Subsp. nordmanniana) leaves

The utility of Nordmann fir (Abies nordmanniana (Stev.) Spach. Subsp. nordmanniana) leaves from Eastern Black Sea region for the removal (sorption) of metal ions from aqueous solutions was investigated. For this, the optimum values of pH, time, metal concentration, leaf concentration, leaf particle size and adsorption capacity were determined. Also the recovery conditions of the metals from leaves were studied. Cd metal was selected because of its toxic properties. Freundlich isotherm model was used to describe the adsorption behaviour and the experimental results obtained for Cd(2+) adsorption, followed this model well. The utility of Nordmann fir leaves to remove toxic metals from aqueous solutions was proved. Hence, this study showed that the leaves of Nordmann fir can provide cheap source as biosorbents for toxic metal removal from natural or wastewaters.     

Removal of heavy metals from aqueous solution using Rhizopus delemar mycelia in free and polyurethane-bound form

This study assesses the ability of mycelia of Rhizopus delemar (both free and immobilized on polyurethane foam) to remove heavy metals from single-ion solutions as well as from a mixture of them. All experiments were conducted using 0.5-5 mm solutions of CuSO4 x 5H2O, CoCl2-6H2O and FeSO4 7H2O. Mycelia immobilized on polyurethane foam cells showed some times increase in uptake compared with that of free cells. Metal ions accumulation from a mixed solution was decreased slightly for cobalt and iron and considerable for copper ions. Heavy metal uptake was examined in the immobilized column experiments and more than 92% heavy metal removal (mg heavy metals removed/mg heavy metals added) from a mixed solution was achieved during the 5 cycles. During these experiments, the dry weight of the immobilized cells was decreased by only 2%. These results showed that immobilized mycelia of Rhizopus delemar can be used repeatedly for removal of heavy metals from aqueous solutions.