The Utilization of Algae and Seaweed Biomass for Bioremediation of Heavy Metal-Contaminated Wastewater

The presence of heavy metals in water bodies is linked to the increasing number of industries and populations. This has serious consequences for the quality of human health and the environment. In accordance with this issue, water and wastewater treatment technologies including ion exchange, chemical extraction, and hydrolysis should be conducted as a first water purification stage. However, the sequestration of these toxic substances tends to be expensive, especially for large scale treatment methods that require tedious control and have limited efficiency. Therefore, adsorption methods using adsorbents derived from biomass represent a promising alternative due to their great efficiency and abundance. Algal and seaweed biomass has appeared as a sustainable solution for environmentally friendly adsorbent production. This review further discusses recent developments in the use of algal and seaweed biomass as potential sorbent for heavy metal bioremediation. In addition, relevant aspects like metal toxicity, adsorption mechanism, and parameters affecting the completion of adsorption process are also highlighted. Overall, the critical conclusion drawn is that algae and seaweed biomass can be used to sustainably eliminate heavy metals from wastewater.     

Bioremediation of effluent from a uranium mill tailings repository in South China by <Emphasis Type="Italic">Azolla</Emphasis>–<Emphasis Type="Italic">Anabaena</Emphasis>

Hydroponic experiments were conducted on the removal of uranium, heavy metals and nutrients from the effluent of a uranium mill tailings repository in South China by Azolla–Anabaena. The plant–microbe symbiont was kept in the effluent for 30 days, and it was found that U, Fe, Mn, Cu, Zn, Pb, Cd, total phosphorus (TP), total nitrogen (TN) and SO₄^2? reduced by 87.6, 99.1, 98.8, 88.2, 91, 78.3, 77.5, 93.4, 98.7 and 76.7%, respectively. Specifically, the concentration of uranium reduced to 0.039 mg L^?1, which is below the limits of contaminants by the Department of Environmental Protection of China. The concentration of Fe, Cu, Zn, Pb, TP and TN in the effluent reached the quality standard for drinking water. The results showed that Azolla–Anabaena can be used for the bioremediation of the effluent from the uranium mill tailings repository.     

生物材料对重金属离子的吸附富集作用

介绍了重金属离子的生物吸附富集作用,从生物材料的类型、生物吸附的选择性、化学修饰与生物吸附、生物对重金属离子的浓缩富集作用和生物吸附的机理及模型等方面作了说明。利用生物材料可去除水体中的重金属离子。     

Removal,recovery and enrichment of metals from aqueous solutions using carbon nanotubes

Environmental pollution caused by toxic metals (heavy metals, radioactive metals, etc.) is one of the major global issues, thus removal of toxic metals from contaminated water seems to be particularly important. On the other hand, the recovery and enrichment of metals, especially noble metals, from waste water is also crucial. To address these issues, nanotechnology plays an essential role in environmental monitoring and pollution control. To remove metals from contaminated water, or enrich metals from waste water, carbon nanotubes (CNTs) and their composites have attracted great attention due to their excellent adsorption performance. The removal efficiency for metal ions by CNTs was observed aroud 10–80 %, which could be improved to approach 100 % by selectively functionalizing CNTs with organic ligands. Herein, we review the applications of CNTs in treatment of toxic metal-containing wastewater for environmental monitoring and metals recovery. Due to their higher sensitivity and selectivity towards the enrichment of metals or detection of toxic metal pollution of the environment, and the latest research progress of using CNT composites for metal treatment is also discussed.     

Colloidochemical Processes in the Biotechnology of Heavy Metal Removal from the Soil

The sorption processes of uranium(VI), copper, cobalt, and strontium by the native soil were studied. It was shown that, by their ability to be accumulated by the podsolized soil, these metals are arranged in the following sequence: U(VI) > Cu > Co > Sr. This selectivity sequence is retained during the sorption of metals from mixed solutions containing their equimolar concentrations. The possibility of the leaching of the studied metals from the contaminated soil by Basillus cereusVKM 4368 metal-resistant culture was demonstrated using glucose and sodium acetate as the sources of carbon and energy. In the first case, 90–99% of heavy metals was extracted from the soil as water-soluble citrate complexes. In the second case (during the metabolism of acetate by bacteria), the removal of heavy metals from the soil as hydroxide–carbonate precipitates and complexes was equal to 80–90%. Sedimentation of particles in the soil suspension is accelerated considerably after the treatment by the metal-resistant culture.     

An experimental study on high-purity uranium refining by passing in succession through pulsed extraction,washing, and stripping columns

Nuclear-purity uranium was refined by passing a solution of uranyl nitrate in 3–5 M HNO₃ in succession through pulsed extraction, washing, and stripping columns for feeding into the U(III)–U(IV) chemical exchange system for uranium isotope separation. The extractant (tri-n-butyl phosphate, TBP), the diluent (kerosene), nitric acid, ammonium carbonate, sodium nitrate, and water were preliminarily refined to chemical purity. The diameter and height of pulsed columns for uranium purification was 25 and 1500 mm, respectively, and the pulse frequency was 1 s^–1. The content of transition metals (Fe, Co, Ni, Cu, Ag) and Pb, which can catalyze the U(III) oxidation in acidic aqueous solutions, was reduced to the level lower than 1 ppm (10^–4%). The total purification factor was higher than 103. The purification required 3–4 theoretical plates with HETP of the columns of 35–40 cm.     

Neutron activation analysis applied to the study of heavy metal marine pollution observed through bioaccumulation in macroscopic algae near El Jadida,Morocco

The heavy metals bio-accumulation ability of algae was studied along the North Atlantic Morrocan coast. Instrumental neutron activation analysis was used, to determine concentrations of various elements. The k ₀ standardization method was used. Some interferences corrections, particularly due to high concentrations of uranium were applied. The quality of the method was checked by using the CRM 140, a Fucus provided by IAEA. Important pollutions appear for several heavy metals from the Morrocan phosphate industry, with respect to the natural background environment.     

Separation of cesium-137 from uranium fission products via a Neoflon® column supporting tetraphenylboron

Cesium is a member of the Group I alkali metals, very reactive earth metals that react vigorously with both air and water. The chemistry of cesium is much like the chemistry of neighboring elements on the periodic table, potassium and rubidium. This close relation creates many problems in plant-life exposed to cesium because it is so easily confused for potassium, an essential nutrient to plants. Radioactive ¹³⁴Cs and ¹³⁷Cs are also chemically akin to potassium and stable cesium. Uptake of these radioactive isotopes from groundwater by plant-life destroys the plant-life and can potentially expose humans to the radioactive affects of ¹³⁴Cs and ¹³⁷Cs. Much experimental work has been focused on the separation of ¹³⁷Cs from uranium fission products. In previous experimental work performed a column consisting of Kel-F supporting tetraphenylboron (TPB) was utilized to separate ¹³⁷Cs from uranium fission products. It is of interest at this time to attempt the separation of ¹³⁴Cs from 0.01M EDTA using the same method and Neoflon in the place of Kel-F as the inert support. The results of this experiment give a separation efficiency of 88% and show a linear relationship between the column bed length and the separation efficiency obtained.     

The removal of Cu,Ni, and Zn in industrial soil by washing with EDTA-organic acids

In order to improve the heavy metal removal ability of traditional single washing agents and explore the removal mechanism of heavy metals. Then, the washing reagents that mixed by low-molecular weight organic acids (citric acid, oxalic acid, and tartaric acid) and artificial chelating compound ethylenediaminetetraacetic acid disodium (EDTA) were selected. Furthermore, the effect of soil washing parameters, the variation of leaching toxicity, mobility, stability and speciation of heavy metals were also considered. The results of soil washing experiments showed that mixing an equal volume of 0.05 M EDTA and 0.2 M organic acids (citric acid, oxalic acid, and tartaric acid) could remove more than about 80% heavy metals from soil under the optimal conditions. In addition, the soil leaching toxicity was decreased and the stability of remaining heavy metals was increased, indicating that EDTA-organic acid washing reagents could effectively reduce the ecological risk of contaminated soil. EDTA had a stronger chelating ability with heavy metals than the organic acids, and the organic acids could not only chelate heavy metals but also decrease the pH of the mixture for promoting the desorption of heavy metals. Thus, mixing EDTA and organic acids was advisable method to improve soil washing technology.     

Assessment of heavy metals leachability from metallo-organic sorbent-iron humate-with the aid of sequential extraction test

The sequential extraction test, known as a BCR procedure, was used to assess a leachability of heavy metals (Zn, Cd, Pb, Cu) from the metallo-organic sorbent—iron humate—loaded with these metals. The sequential test allowed to discriminate between various fractions of heavy metals, namely the acid-extractable fraction, the fraction bound to Fe oxides, and the fraction bound to organic matter. It was proven that the heavy metals are bound mainly to Fe oxides and organic matter, and thus they may be relatively hardly liberated into the environment. The BCR sequential extraction test exhibited a very good repeatability, when it was applied to the loaded sorbent—relative standard deviations were typically lower than 10%.     

Stability and Mobility of Metal-Humic Complexes Isolated from Different Soils

The contamination of potable water aquifers by heavy metals is one of the most severe environmental threats. For the transport of heavy metals from various types of contaminated sites into the ground water and also into surface water aquifers, humic substances (HS) are recognized to be of main importance. Dissolved in natural waters humic substances are readily complexed with a variety of metal ions. Therefore, humic substances are of cardinal importance for the migration and, consequently, the pollution of ground waters with heavy metals. Our paper presents the results of a comprehensive comparison of several isolated humic acids of soils of different origin (different geochemical milieu) and their metal complexes. Two polluted sites in Germany, which differ in their geochemical milieu (pH-value) were selected. The aim of our experiments was to describe the properties of terrestrial humic substances depending on their origin and genesis as well as the effects of the transport of humic substance-bound metals into the water-unsaturated soil zone. After determination of heavy metals in the soils by photon activation analysis the activated soil was used as an inherent tracer in batch experiments with the isolated humic acid. After adsorption of the loaded humic acid on an XAD-8 resin column, the partition of metals mobilized by humic acids could be quantified. There are correlations of the formation of metal-humic complexes with the soil pedogenes, with the pH-value as well as with the humic acid concentration.     

Determination of Kinetic Parameters in the Biosorption of Cr (VI) on Immobilized <Emphasis Type="Italic">Bacillus cereus</Emphasis> M<Superscript>1</Superscript><Subscript>16</Subscript> in a Continuous Packed Bed Column Reactor

Due to technological advancement, environment suffers from untreated toxic heavy metal bearing effluent coming from different industries. Chromium (VI) is one of those heavy metals having adverse impact on ecological balance, human, and plant health because of its carcinogenic properties. Biosorption is presented as an alternative to traditional technologies which are costly and inefficient for treatment of industrial wastes containing low amount of heavy metals. In this study, bioremediation of Cr (VI) ions by immobilized Bacillus cereus M¹ ₁₆ was investigated in a laboratory scale packed bed up-flow column reactor. The effect of important parameters, such as the inlet flow rate, influent concentration, and effective bed height, has been studied. External mass transfer, surface adsorption, and intrabead mass transfer were also studied to conclude the rate limiting step for removal of Cr (VI) and to determine the process parameters which are important for biosorption optimization. The external mass transfer coefficient was calculated at different flow rates (6.51 × 10⁻² to 7.58 × 10⁻² cm/min). Using the model, the surface adsorption rate constant (k _ad) and the intrabead mass transfer coefficient (k _i) were predicted as 0.0267 × 10⁻³ and 0.7465 × 10⁻³ l/g/min, respectively. Both are much lower than the external mass transfer coefficient (k _e). The surface adsorption phenomenon is acting as the rate-limiting step due to its high resistance for removal of Cr (VI).     

Effects of supercritical fluid extractions on metal ion partitioning as indicated by sequential extractions

We have studied the partitioning of stable elements and uranium to two sediments using sequential extractions (SE). These matrices were then subjected to supercritical fluid extraction (SFE) to attempt to remove the uranium. SEs were repeated on the material remaining after SFE to determine any changes in partitioning. We have confirmed that under suitable chemical conditions, ligand-assisted SFE can be used to extract many metal ions from such matrices. Under the conditions we used, the "easily leachable" metals were extracted, but the refractory metals were not. In addition, SFE appears to redistibute the remaining metal cations among the remaining geochemical after SFE treatment. Our results are presented and discussed in the context of developing decontamination strategies for contaminated soils and sediments.     

Bioengineered Chimeric Spider Silk‐Uranium Binding Proteins

Heavy metals constitute a source of environmental pollution. Here, novel functional hybrid biomaterials for specific interactions with heavy metals are designed by bioengineering consensus sequence repeats from spider silk of Nephila clavipes with repeats of a uranium peptide recognition motif from a mutated 33‐residue of calmodulin protein from Paramecium tetraurelia. The self‐assembly features of the silk to control nanoscale organic/inorganic material interfaces provides new biomaterials for uranium recovery. With subsequent enzymatic digestion of the silk to concentrate the sequestered metals, options can be envisaged to use these new chimeric protein systems in environmental engineering, including to remediate environments contaminated by uranium.

     

Dynamics of Heavy Metals in Soils of a Reed Bed System

Abstract

Heavy metal balances of a reed bed system (soil pH > 7, carbonate content about 30%) continuously flooded with sewage during 5 years indicate that only Pb, Zn, Cd and Cu were partly stored in the soil. Strong reductive conditions, high sewage percolation and metal complexation with soluble organic compounds caused a considerable leaching of Fe, Mn, Ni and Cr from the soil and formation of amorphous iron oxides. The results indicate that continously flooded reed bed systems with high percolation rates are not suitable for the elimination of heavy metals. Conversely, it should be possible to purify metal contaminated soils through percolation of sewage with low metal content.     

A new biomaterial,hen egg shell membrane,to eliminate heavy metal ion from their dilute waste solution

The egg shell membrane (ESM) is an intricate lattice network of stable and water-insoluble fibers with high surface area. ESM accumulates and eliminates various heavy metal ions from dilute aqueous solution with high affinity and in short contact time, depending on pH and characteristics of the individual ion. Under certain conditions, the level of precious ions, Au, Pt, and Pd accumulation approaches 55, 25, and 22% of dry wt of ESM, respectively. Also uranium uptake 30% of that of ESM. Experiments suggested that ESM is promising to use for the purpose of removal/recovery of metals and water pollution control.     

The Use of Seaweed and Sugarcane Bagasse for the Biological Treatment of Metal-contaminated Waters Under Sulfate-reducing Conditions

When wetlands reach maximum treatment capacity to remove heavy metals, removal can still take place through precipitation as sulfide because of the biological reduction of sulfate. To achieve this goal, anaerobic conditions must be attained, a sulfate source must exist, and an adequate substrate for sulfate-reducing bacteria (SRB) is also required. In the present work, two ligneous-cellulosic materials, a brown seaweed and sugarcane bagasse, have been selected as substrates for SRB growth. Experiments were simultaneously conducted in continuous operation in two columns (0.57 L each), one containing the ligneous-cellulosic material plus inoculum and another containing only the ligneous-cellulosic material. In this work, the removal of cadmium and zinc was studied because of their presence in effluents from mining/metallurgy operations. Results obtained indicated that the inoculated reactor was able to treat the effluent more efficiently than the noninoculated reactor considering the time course of the tests.     

Biosorption of copper by biomass of extremophilic algae

Copper and lead are among the most important chemical pollutants of the environment including hydrosphere. Interaction of these heavy metals with biomass of aquatic plant organisms including algae is an area of active research in ecological chemistry. We investigated the interaction of the biomass of unique extremophilic (thermophilic) algae Galdieria sulphuraria with these heavy metals in aquatic environment using stripping voltammetry. Biosorption of copper by the studied biomass from aquatic medium has been discovered; however, no biosorption of another heavy metal from aquatic environment with the biomass has been detected. The experiments with the mortmass of Galdieria sulphuraria have revealed no sorption of the heavy metals as measured by stripping voltammetry. The difference in the interaction of copper and lead with the algal biomass is important for deeper understanding of the biosorption phenomenon. The new data stimulated further interest to the concept of biogenic migration of chemical elements that was proposed by V.I. Vernadskii. The results contributed to the scientific basis for innovative biotechnology to decontaminate water.     

Heavy Metal Contamination and Accumulation in Soil and Plant Species from the Xinqiao Copper Deposit,Anhui Province,China

The distribution and accumulation of heavy metals in soil and various plants were investigated in Xinqiao, the location of one of the largest copper deposits in China. The concentrations of cadmium, copper, lead, and zinc were determined by inductively coupled plasma–mass spectrometry (ICP–MS), and the results suggest that the soil was contaminated by mining activities. Plants grown around the study area accumulated these metals at various concentrations. The concentrations of metals in the plants indicated that the accumulation levels were not consistent with the relative concentrations in the corresponding soils. Almost all plants primarily accumulated heavy metals in above-ground tissues, especially Commelina communis. High biological transfer coefficients for Buddleja davidii, Rumex acetosa, Debregeasia edulis, Commelina communis, and Rosacfolius smith for some metals indicate accumulation in stems and leaves and identify these plants as hyperaccumulators.     

Uranium speciation in biofilms studied by laser fluorescence techniques

Biofilms may immobilize toxic heavy metals in the environment and thereby influence their migration behaviour. The mechanisms of these processes are currently not understood, because the complexity of such biofilms creates many discrete geochemical microenvironments which may differ from the surrounding bulk solution in their bacterial diversity, their prevailing geochemical properties, e.g. pH and dissolved oxygen concentration, the presence of organic molecules, e.g. metabolites, and many more, all of which may affect metal speciation. To obtain such information, which is necessary for performance assessment studies or the development of new cost-effective strategies for cleaning waste waters, it is very important to develop new non-invasive methods applicable to study the interactions of metals within biofilm systems. Laser fluorescence techniques have some superior features, above all very high sensitivity for fluorescent heavy metals. An approach combining confocal laser scanning microscopy and laser-induced fluorescence spectroscopy for study of the interactions of biofilms with uranium is presented. It was found that coupling these techniques furnishes a promising tool for in-situ non-invasive study of fluorescent heavy metals within biofilm systems. Information on uranium speciation and uranium redox states can be obtained.