Transport Of Heavy Metal Ions Research Articles

Analytical model for electrokinetic remediation of contaminated soil

Electrokinetic remediation (EKR) is an effective approach to eliminate heavy metal contaminants from soil and pore water. However, only a few studies have been conducted on related analytical theory because of the complexity of transport processes and the lack of effective calculation methods. In this study, a novel analytical model is proposed to investigate the one-dimensional transport of heavy metal ions (HMIs), encompassing electro-osmosis, electro-migration, hydraulic osmosis, diffusion, adsorption, and thermal diffusion. A comprehensive analysis is conducted to study the effects of key parameters on the transport process. Several important insights are gained, e.g., an increase in the Soret coefficient accelerates the migration of HMIs. Meanwhile, an increase in both the electric potential gradient and the hydraulic gradient is beneficial for the remediation of contaminated soil, although the effect of the electric potential gradient is more significant.

A genome-wide association analysis for salt tolerance during the soybean germination stage and development of KASP markers.

Salt stress poses a significant challenge to crop productivity, and understanding the genetic basis of salt tolerance is paramount for breeding resilient soybean varieties. In this study, a soybean natural population was evaluated for salt tolerance during the germination stage, focusing on key germination traits, including germination rate (GR), germination energy (GE), and germination index (GI). It was seen that under salt stress, obvious inhibitions were found on these traits, with GR, GE, and GI diminishing by 32% to 54% when compared to normal conditions. These traits displayed a coefficient of variation (31.81% to 50.6%) and a substantial generalized heritability (63.87% to 86.48%). Through GWAS, a total of 1841 significant single-nucleotide polymorphisms (SNPs) were identified to be associated with these traits, distributed across chromosome 2, 5, 6, and 20. Leveraging these significant association loci, 12 candidate genes were identified to be associated with essential functions in coordinating cellular responses, regulating osmotic stress, mitigating oxidative stress, clearing reactive oxygen species (ROS), and facilitating heavy metal ion transport - all of which are pivotal for plant development and stress tolerance. To validate the candidate genes, quantitative real-time polymerase chain reaction (qRT-PCR) analysis was conducted, revealing three highly expressed genes (Glyma.02G067700, Glyma.02G068900, and Glyma.02G070000) that play pivotal roles in plant growth, development, and osmoregulation. In addition, based on these SNPs related with salt tolerance, KASP (Kompetitive Allele-Specific PCR)markers were successfully designed to genotype soybean accessions. These findings provide insight into the genetic base of soybean salt tolerance and candidate genes for enhancing soybean breeding programs in this study.

Light-Augmented Multi-ion Interaction in MXene Membrane for Simultaneous Water Treatment and Osmotic Power Generation.

The mixing of wastewater and natural water releases abundant osmotic energy. Harvesting this energy could significantly reduce the energy and economic cost of water treatment, leading to sustainable wastewater treatment technology. Yet, such energy harvesting is highly challenging because it requires a material that is highly permeable to nontoxic ions while rejecting toxic ions in wastewater to reach high power density and prevent environmental pollution. In this work, we demonstrate that a light-augmented biomimetic multi-ion interaction in an MXene membrane can simultaneously realize high permeability of Na+ ions for enhanced osmotic power generation and high selectivity to heavy metal ions up to a ratio of 2050 for wastewater treatment. The Na+ permeability is enhanced by the photothermal effect of the MXene membrane. The transport of heavy metal ions, however, is suppressed because, under angstrom-confinement, heavy metal ions are strongly electrostatically repelled by the increased number of permeating Na+ ions. As a result, the membrane can stably generate osmotic power from simulated industrial wastewater, and the power density can be enhanced by 4 times under light illumination of approximate 1 sun intensity. This work highlights the importance of multi-ion interaction for the transport properties of ionic materials, which remains rarely investigated and poorly understood in previous studies.

Rhizosphere microbial characteristics of pioneer plant Oxyria sinensis Hemsl. in abandoned Pb-Zn mining area

Oxyria sinensis has the characteristics of drought resistance, barren resistance, pollution resistance and clonal reproduction, and has the potential to be developed as a restoration plant (pioneer plant) for vegetation restoration and heavy metal pollution control in mining wasteland. In this study, the rhizosphere microbial communities of the pioneer plant O. sinensis growing in a lead-zinc mine wasteland and the rhizosphere microbial communities of O. sinensis growing in adjacent non-mining areas were studied by field investigation. There were significant differences in the composition of microbial communities between the rhizosphere soil of O. sinensis and the bare soil. There were significant differences in the composition of soil microbial communities between the non-mining area control and the lead-zinc mine wasteland. Compared with the non-mining area control, the rhizosphere soil of O. sinensis in the lead-zinc mine wasteland had a unique microbial community. The dominant bacteria were Nitrospirae, Chloroflexi, Proteobacteria, Actinobacteria, Ascomycota and Kickxellomycota. Further gene function prediction showed that the metabolic pathway sequences related to heavy metal ion transport, heavy metal resistance and repair in the rhizosphere soil of O. sinensis were more abundant than those in the control. The dominant ecological functional groups of fungi in the rhizosphere soil of O. sinensis were saprophytic flora and pathological flora. Plenodomus, Surfurifusis, Sphingomonas, Filobasidium and Articulospora were enriched in the rhizosphere soil of O. sinensis in the abandoned land of lead-zinc mining area, and had high tolerance to heavy metals in the soil, indicating that O. sinensis can recruit heavy metal-tolerant microbial groups to promote its survival and adaptation in the abandoned land of the mining area.

Effect of Capillary Transport of Zinc Chloride Solution in Nanopores of Cement-based Materials

In recent years, heavy metal pollution has become more severe, which threatens human health and ecological environment. Cement-based materials are the most common remediation methods to fix heavy metal pollution. In order to explore the transport of heavy metal ions in cement-based material nanochannels from the molecular scale. In this paper, 11A Tobermorite was used as the initial cement-based material model, and then through a series of adjustments, CSH gel channels were assembled with Zncl2 solution, so as to explore the capillary transport of zinc chloride solution in cement-based material nanopores. The density distribution of water and the number distribution of zinc ions show that the density of water molecules in the nanoporous channel decreases sharply, and the migration of zinc ions in the nanoporous channel is well limited by calcium silicate hydrate.

Mobility of water-soluble aerosol organic matters (WSAOMs) and their effects on soil colloid-mediated transport of heavy metal ions in saturated porous media

Water-soluble aerosol organic matters (WSAOMs) produced by biomass pyrolysis/burning can penetrate subsurface environment, and are anticipated to have a profound effect on the fate of contaminants in aquatic ecosystems. Herein, WSAOMs derived from corn straw (CS-WSAOMs) and pinewood sawdust (PW-WSAOMs) pyrolysis at 300–900 °C were utilized to investigate their mobility characteristics and impacts on the transport of heavy metal ions (i.e., Cd2+) in saturated quartz sand with or without soil colloids. This study clearly demonstrated that WSAOMs in subsurface systems exhibited high mobility, which increased as WSAOMs molecular sizes decreased and hydrogen-bond interactions between WSAOMs and sand grains declined. WSAOMs significantly improved heavy metal (i.e., Cd2+) and soil colloid-mediated Cd2+ mobility in the porous media, which stemmed from the increased binding affinities of colloids toward metal ions and the high mobility of WSAOMs. Interestingly, in terms of the mobility and colloid-facilitated transport of Cd2+, WSAOMs from higher pyrolysis temperatures exhibited enhanced effects; meanwhile, the PW-WSAOMs demonstrated stronger effects than the CS-WSAOMs. The trends were mainly attributed to the differences in the metal-binding affinities (e.g., cation-π interactions) and transport abilities of WSAOMs, as well as diverse Cd2+ adsorption capacities of colloids induced by various WSAOMs.

Feasibility of Adsorption Kinetic Models to Study Carrier-Mediated Transport of Heavy Metal Ions in Emulsion Liquid Membranes.

Emulsion liquid membranes have been successfully used for the removal of different types of organic and inorganic pollutants by means of carrier-mediated transport mechanisms. However, the models that describe the kinetics and transport of such mechanisms are very complex due to the high number of model parameters. Starting from an analysis of the similarity between the elemental mechanisms of carrier-mediated transport in liquid membranes and of transport in adsorption processes, this paper presents an experimental analysis of the possibility of applying kinetic and mechanistic models developed for adsorption to carrier-mediated transport in emulsion liquid membranes. We study the removal of a target species, in this case, Cu(II), by emulsion liquid membranes containing membrane phase solutions of benzoylacetone (carrier agent), Span 80 (emulsifying agent) and kerosene (diluent), and hydrochloric acid as a stripping agent in the product phase. The experimental results fit the pseudo-second-order adsorption kinetic model, showing good relationships between the experimental and model parameters. Although both Cu(II) diffusion through the feed/membrane interface boundary layer and complex Cu-benzoylacetone diffusion through the membrane phase controls Cu(II) transport, it is the former step that mainly controls the transport process.

Enhanced transport of heavy metal ions by low-molecular-weight organic acids in saturated porous media: Link complex stability constants to heavy metal mobility

Environment-ubiquitous low-molecular-weight organic acids (LMWOAs) can interact with heavy metal ions and thus affect their mobility in subsurface aquifers. Herein, the effects of LMWOAs (including acetic acid, tartaric acid, malonic acid, oxalic acid, and citric acid) on the mobility of heavy metal ions (including Cd2+, Zn2+, Ni2+, Mn2+, and Co2+) in porous media were investigated to reveal the role of the stability constants of metal-LMWOA complexes in the mobility of heavy metal ions in porous media. The results showed that the mobility of different metal ions followed the order of Cd2+ < Zn2+ < Ni2+ < Mn2+ < Co2+ despite of LMWOAs-free or LMWOAs-addition. For each heavy metal, all the organic acids enhanced its transport by forming stable non-adsorbing metal-LMWOA complexes and the enhanced ability followed the order of citric acid > oxalic acid > malonic acid > tartaric acid > acetic acid. An interesting finding was that there was a significantly positive correlation between the enhanced abilities of LMWOAs to metal mobility and the complex stability constants (log K) (R2 = 0.801–0.961, p < 0.05), indicating that the complex stability of metal-LMWOA was the dominant factor responsible for the enhanced transport of heavy metal ions. Meanwhile, the linear slope indicated the intensity of enhancement of LMWOAs on heavy metal mobility was heavy metal type-dependent. This study proposed that the complex stability of metal-LMWOA could be an indicator to quantify and predict the impact of LMWOAs on the mobility of heavy metals.

Advances in plant heavy metal transporter P1B-ATPases

P1B-ATPases are a group of proteins that can transport heavy metal ions across membranes by hydrolyzing ATP and they are a subclass of the P-type ATPase family. It was found that P1B-ATPases are mainly responsible for the active transport of heavy metal ions in plants and play an important role in the regulation of heavy metal homeostasis in plants. In this paper, we dissusses the mechanism of P1B-ATPases from the structure and classification of P1B-ATPases, and review the current research progress in the function of P1B-ATPases, in order to provide reference for future research and application of P1B-ATPases in improving crop quality and ecological environment management.

Implication of exogenous abscisic acid (ABA) application on phytoremediation: plants grown in co-contaminated soil.

Abscisic acid (ABA) may play an important role in alleviating negative effects of heavy metal stress on growth performance of plants. A pot experiment was conducted to investigate differential effects of exogenous ABA with different concentrations (0, 20, 40, and 60 μmol/L) on heavy metal accumulation and physiological response of Cd/Zn hyperaccumulator Sedum alfredii Hance and non-hyperaccumulator Hylotelephium spectabile (Boreau) H. Ohba grown in co-contaminated soil. In the experiment, Cd, Zn, or Pb concentration in stem and leaf of H. spectabile was significantly increased by exogenous ABA application than control. However, the opposite pattern was observed for S. alfredii. With decrease of Cd concentration, Zn or Pb concentration in root of H. spectabile grown in co-contaminated soil was significantly increased by exogenous ABA application than control. Cd, Zn, or Pb concentration in root of S. alfredii was significantly increased by exogenous ABA application than control. Compared with S. alfredii, BCF and TF of Cd, Zn, or Pb for H. spectabile were significantly increased by exogenous ABA application. With negative effect on root growth, total biomass of the two species, especially H. spectabile, was significantly increased by exogenous ABA application than control. With increase of their total chlorophyll content, antioxidant capacity of the two species subjected to heavy metal stress was improved by exogenous ABA application than control. Heavy metal-induced growth inhibition was significantly alleviated by exogenous ABA application when the two species were grown in co-contaminated soil. We tentatively concluded that differential effects of exogenous ABA application on transport pathway of ions incurred different patterns of heavy metal accumulation between Cd/Zn hyperaccumulator S. alfredii and non-hyperaccumulator H. spectabile. It is suggested that compared with Cd/Zn hyperaccumulator S. alfredii, exogenous ABA application may improve heavy metal uptake in root and transport of heavy metal ions between different organs for non-hyperaccumulator H. spectabile grown in co-contaminated soil. Our results provide insight into effects of exogenous ABA application on phytoremediation of Cd-, Pb-, and Zn-co-contaminated soil.

Preparation of Modified Calcium Bentonite for the Prevention of Heavy Metal Ion Transport in Groundwater

Vertical engineered barriers are often used to prevent the transport of heavy metal ions in groundwater, and barrier layers are the key to pollution control. In this study, modified calcium-based bentonite (CB) was prepared via the modification of CB with sodium carboxymethyl cellulose (CMC) and sodium hexametaphosphate (SHMP) for the prevention of heavy metal ions transport. CMC-SHMP@CB composites were prepared by pulping, drying and grinding. Structural characterization was performed by using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The swelling, permeability and adsorption properties of the CMC-SHMP@CB composites were further evaluated. The results show that these CMC-SHMP@CB composites have a hybrid microstructure from the intercalation and exfoliation action during modification. The swell index in deionized water of the CMC-SHMP@CB composites is 24.4 mL/2 g, which is 4.8 times that of the original CB index. Modification of CB with CMC and SHMP significantly improves its anti-permeation performance. In the presence of Cd2+ and Ni2+ ions, the hydraulic conductivity of the CMC-SHMP@CB composites still reaches ~ 3 × 10-11 m/s, which is much lower than the value of untreated CB. The adsorption capacity values of CMC-SHMP@CB for Ni2+ and Cd2+ were 11.01 mg/g and 13.82 mg/g, which are 5.6 times and 7.2 times the values before modification. CMC-SHMP@CB composites have great potential for use as the barrier layers for the prevention of heavy metal ions transport in groundwater.

Separation/Competitive Transport of Heavy Metal Ions across the Bulk Liquid Membranes with N,N',N''-Tris(4-methylphenyl)phosphoric Triamide As Carrier

The competitive bulk liquid membrane transport of seven metal ion by N,N',N''-tris(4-methylphen-yl)phosphoric triamide carrier was studied using a flame atomic absorption spectrometry. Dichloromethane (DCM), chloroform (CHCl3), nitrobenzene (NB) and 1,2-dichloroethane (1,2-DCE) solvents have been used as bulk liquid membranes (BLM). The carrier has been shown the maximum transport rate for Cu2+ cation in all of the BLM systems (except of 1,2-DCE) in comparison to the other cations containing Co2+, Cd2+, Ag+, Pb2+, Ni2+, Cu2+, and Zn2+. The obtained results show that the selectivity and efficiency of transport in presence of this ligand change with the type of organic solvents. Various factors that affect the transport efficiency of this heavy metal cations have been optimized in order to obtain maximum transport. The complexation process between phosphoric triamide and Cu2+cation have also been examined by conductomery method. The stoichiometry of the complex and the formation constant of phosphoric triamid-Cu2+ complex have been determined.

Efficient removal of lead and copper ions from water by enhanced strength-toughness alginate composite fibers

In this study, we designed and synthesized an enhanced strength-toughness alginate composite fiber by using graphene oxide as reinforcing filler for removing heavy metal ions from water media. The as-prepared alginate composite fiber exhibits high affinity to Pb2+ ion, and the maximum adsorption capacity for Pb2+ reached 386.2 mg/g, which is higher than the reported Pb2+-sorbent. The prepared round-shaped nanofibers have relatively uniform distribution with a diameter of 400 nm, and the interlaced fibers form porous structure that conducive to the rapid transport of heavy metal ions. Adsorption mechanism analysis shows that the alginate composite fibers combine heavy metals mainly by ion exchange and chemical coordination effects. Owing to the excellent mechanical properties of graphene oxide, the alginate composite fibers can be used repeatedly with minimal loss in performance.

Arabidopsis CNGC Family Members Contribute to Heavy Metal Ion Uptake in Plants.

Heavy metal ions, including toxic concentrations of essential ions, negatively affect diverse metabolic and cellular processes. Heavy metal ions are known to enter cells in a non-selective manner; however, few studies have examined the regulation of heavy metal ion transport. Plant cyclic nucleotide-gated channels (CNGCs), a type of Ca2+-permeable-channel, have been suggested to be involved in the uptake of both essential and toxic cations. To determine the candidates responsible for heavy metal ion transport, a series of Arabidopsis CNGC mutants were examined for their response to Pb2+ and Cd2+ ions. The primary focus was on root growth and the analysis of the concentration of heavy metals in plants. Results, based on the analysis of primary root length, indicated that AtCNGC1, AtCNGC10, AtCNGC13 and AtCNGC19 play roles in Pb2+ toxicity, while AtCNGC11, AtCNGC13, AtCNGC16 and AtCNGC20 function in Cd2+ toxicity in Arabidopsis. Ion content analysis verified that the mutations of AtCNGC1 and AtCNGC13 resulted in reduced Pb2+ accumulation, while the mutations of AtCNGC11, AtCNGC15 and AtCNGC19 resulted in less Pb2+ and Cd2+ accumulation in plants. These findings provide functional evidence which support the roles of these AtCNGCs in the uptake and transport of Pb2+ or Cd2+ ion in plants.

Co-transport of graphene oxide and heavy metal ions in surface-modified porous media

The ability to predict the transport of heavy metal ions in porous media with different surface characteristics is crucial to protect groundwater quality and public health. In this study, the effects of graphene oxide (GO) on co-transport and remobilization of Pb2+ and Cd2+ in humic acid (HA), smectite, kaolinite, and ferrihydrite-coated sand media were evaluated via laboratory packed-column experiments. Scanning electron microscope and energy dispersive X-ray analysis showed that the surface morphology of the coated sands was quite different and that ∼56.7–89.9% of the surface was covered by the coating and the major elemental components were C, O, Si, Al, and Fe. GO exhibited high mobility in HA, kaolinite, and smectite-coated sand, but showed high retention in ferrihydrite-coated sand. While GO reduced the transport of Pb2+ and Cd2+, both metal ions also reduced the mobility of GO in coated-sand columns. Elution experiments revealed that GO led to the remobilization and release of the previously sorbed Pb2+ and Cd2+ from the coated sand. However, GO could not release Pb2+ and Cd2+ from smectite-coated sand columns, probably because smectite has stronger adsorption affinity to the heavy metals than GO. Derjaguin-Landau-Verwey-Overbeek calculations were employed and explained the GO transport behavior in the columns well. Furthermore, the advection-dispersion-reaction equation simulated the cotransport of Pb2+ and Cd2+ with GO in the coated sand well. These results are expected to provide insight into the potential impact of coexisting nanomaterials with contaminants in vulnerable soil and groundwater systems.

Study on Penetration Effect of Heavy Metal Migration in Different Soil Types

Soil column permeability experiments were conducted in the laboratory to study the transport characteristics of five heavy metal ions of Mn2+, Ni2+, Cd2+, Cr2+, and Cu2+ in saturated loess, sandy soil and compound soil. The results showed that the texture of soil and the characteristics of heavy metal ions have a common effect on the transport of heavy metal ions. The migration process of five metals in eight soils is different, and the same soil conditions, different metals, and the migration process are different. Very large, the same metal, different soils are also very different. The penetration rates of the five heavy metal ions were Mn2+>Ni2+>Cd2+>Cu2+ >Cr2+. Mn2+ is the most easily migrating in both soils, requiring the shortest penetration time and a smaller retardation factor than other metals, suggesting that the resistance to penetration is minimal. The penetration time of all metals in sandy soil and compound soil is less than that in loess, and the pore flow velocity is much higher than the pore flow velocity in loess. The migration resistance of loess to all metals is much higher than that of sandy soil and compound soil. Metal migration resistance. The adsorption performance of the five heavy metal ions on the five heavy metals is higher than that of the sandy soil and the compound soil. The sandy soil originates from the impact slope of the flood land. The soil clay, cation exchange capacity and organic matter are all lower than that of the loess, and the adsorption of heavy metal ions is better. weak. Heavy metal ions are easy to migrate in sandy soils in the mining area, which infiltrate deep into the soil or into groundwater, causing pollution. Heavy metal ions in loess do not migrate easily and can be adsorbed on the surface or shallow surface for a short time. It is not easy to cause deeper contamination of groundwater, but it also causes As surface runoff migrates laterally to rivers or other areas and expands the area of pollution, no matter which kind of metal in the mining area, the content of which is too high can cause pollution to the environment and cause adverse effects.

Molecular characterization of cadmium-resistant Cupriavidus spp. and Ralstonia solanacearum isolated from soil and plants in Taiwan

Cadmium is a natural heavy-metal element. It is highly toxic and a vital industrial pollutant to the environment. In order to survive in heavy-metal polluted environments, some bacteria can withstand high concentrations of heavy metals in environment due to their specific mechanisms, including the transport of heavy metal ions out of the cell. Three kinds of membrane-bound-proteins are known to participate in this transport. The objective of this study was to determine the cadmium-resistant properties and possible mechanism among strains of Cupriavidus metallidurans (= Ralstonia eutropha), C. Taiwanensis (=R. Taiwanensis) and Ralstonia solanacearum isolated from soil and plants in Taiwan. Strains tested include six strains, rcd 6, 8, 19 (C. metallidurans) and rcd 12, 14, 21 (C. Taiwanensis), from cadmium-polluted soil, seventeen strains, nod 1 to nod 5 and nod s1 to s12 (C. Taiwanensis) from root nodules of two Mimosa species (M. pudica and M. diplotricha), and ten strains of R. solanacearum isolated from different diseased plants. Sequence analysis of 16S-23S rDNA ITS and nifH gene regions were used to confirm the taxonomic classification of these bacteria. However, the 624-bp PCR product of nifH gene was only amplified from strains nod 1 to nod 3 and nod s1 to s12, but not from other tested strains of Cupriavidus and Ralstonia spp. These tested strains could tolerate cadmium within the range from 0.67 to 6.70 mM. The gene, czcC, thought to encode the outer membrane factor (OMF) of czc efflux system, was found in fifteen tested strains (rcd 6, 8, 12, 14, 19, 21; nod s1 to s6, s9, s11; PSS161) by PCR. Especially, strains rcd 12, 14, and 21 which could tolerate higher cadmium concentration (6.70 mM) harbored the entire czc operon. In addition, the PCR products revealed that cadmium-tolerant strains contained at least a portion of the czc operon and efflux mechanism was confirmed by cadmium uptake test. The results here indicated that cadmium resistant capability in Cupriavidus spp. and R. solanacearum was related to the presence of czcC or czc operon.

Fullerol-facilitated transport of copper ions in water-saturated porous media: Influencing factors and mechanism

The environmental safety of carbon nanomaterials (CNMs) has become a hot spot of worldwide research work. The high stability, mobility and adsorption capability of CNMs may give rise to the enhancement of heavy metal transport. However, the understanding of facilitated transport of heavy metal ions by CNMs is still limited. In this research, fullerol nanoparticles (C60(OH)n) were used as a typical CNM to investigate its effect on Cu2+ transport in the water-saturated porous media. Column experiments showed that C60(OH)n could facilitate the transport of Cu2+. Meanwhile, flow velocity showed little impact on the facilitated transport while pH and fullerol concentration played an important role. The mechanism of fullerol-facilitated transport of Cu2+ was mainly due to the much higher adsorption capacity of C60(OH)n than that of the porous media. Besides, the existence of C60(OH)n decreased the adsorption kinetics of Cu2+ on the porous media, which led to a decreasing chance for Cu2+ to be retained and thus enhanced the transport of Cu2+.

Comparative genomic analyses of transport proteins encoded within the red algae Chondrus crispus, Galdieria sulphuraria, and Cyanidioschyzon merolae11.

Galdieria sulphuraria and Cyanidioschyzon merolae are thermo-acidophilic unicellular red algal cousins capable of living in volcanic environments, although the former can additionally thrive in the presence of toxic heavy metals. Bioinformatic analyses of transport systems were carried out on their genomes, as well as that of the mesophilic multicellular red alga Chondrus crispus (Irish moss). We identified transport proteins related to the metabolic capabilities, physiological properties, and environmental adaptations of these organisms. Of note is the vast array of transporters encoded in G.sulphuraria capable of importing a variety of carbon sources, particularly sugars and amino acids, while C.merolae and C.crispus have relatively few such proteins. Chondruscrispus may prefer short chain acids to sugars and amino acids. In addition, the number of encoded proteins pertaining to heavy metal ion transport is highest in G.sulphuraria and lowest in C.crispus. All three organisms preferentially utilize secondary carriers over primary active transporters, suggesting that their primary source of energy derives from electron flow rather than substrate-level phosphorylation. Surprisingly, the percentage of inorganic ion transporters encoded in C.merolae more closely resembles that of C.crispus than G.sulphuraria, but only C.crispus appears to signal via voltage-gated cation channels and possess a Na+ /K+ -ATPase and a Na+ exporting pyrophosphatase. The results presented in this report further our understanding of the metabolic potential and toxic compound resistances of these three organisms.

Sustainable Use of Locally Available Red Earth and Black Cotton Soils in Retaining Cd2+ and Ni2+ from Aqueous Solutions

The relative performance of two soils as a sustainable material to attenuate the transport of heavy metal ions, cadmium (Cd2+) and nickel (Ni2+), from aqueous solutions has been evaluated. Red earth soil (RS) and black cotton soil (BCS) originating from India, were selected, and batch equilibrium tests including sorption kinetics and leaching studies were conducted. Langmuir isotherm was found to be more suitable than Freundlich isotherm for both the soils. Kinetic data were fitted on four models namely pseudo first order, pseudo second order, Elovich and intraparticle diffusion. Correlation coefficients obtained by all models fitted well in the following ranking: Elovich > Intraparticle diffusion > pseudo second order > pseudo first order. Based on extensive experimental data, it is concluded that the ranking on sorption was of the order Cd > Ni for both the soils, and BCS exhibited relatively higher retention levels compared to RS. It is further concluded that BCS can be used as a substitute to filter material, RS a substitute to main liner material in attenuating Cd2+ and Ni2+ from an industrial landfill leachate.