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In this study, we evaluate the factors which determine the reactivity of divalent metal ions in the spontaneous formation of metallochlorophylls, using experimental and computational approaches. Kinetic studies were carried out us...
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In this study, we evaluate the factors which determine the reactivity of divalent metal ions in the spontaneous formation of metallochlorophylls, using experimental and computational approaches. Kinetic studies were carried out using pheophytin a in reactions with various divalent metal ions combined with non- or weakly-coordinative counter ions in a series of organic solvents. To obtain detailed insights into the solvent effect, the metalations with the whole set of cations were investigated in three solvents and with Zn2+ in seven solvents. The reactions were monitored using electronic absorption spectroscopy and the stopped-flow technique. DFT calculations were employed to shed light on the role of solvent in activating the metal ions towards porphyrinoids. This experimental and computational analysis gives detailed information regarding how the solvent and the counter ion assist/hinder the metalation reaction as activators/inhibitors. The metalation course is dictated to a large extent by the reaction medium, via either the activation or deactivation of the incoming metal ion. The solvent may affect the metalation in several ways, mainly via H-bonding with pyrrolenine nitrogens and the activation/deactivation of the incoming cation. It also seems to affect the activation enthalpy by causing slight conformational changes in the macrocyclic ligand. These new mechanistic insights contribute to a better understanding of the "metal-counterion-solvent" interplay in the metalation of porphyrinoids. In addition, they are highly relevant to the mechanisms of metalation reactions catalyzed by chelatases and explain the differences between the insertion of Mg2+ and other divalent cations.
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Spirulina cells are capable of biosorption of various heavy metals. It is possible to remove or reduce the ions of contaminated water using biomass of Spirulina. The present study showed that Spirulina biomass absorbed 95% (approx...
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Spirulina cells are capable of biosorption of various heavy metals. It is possible to remove or reduce the ions of contaminated water using biomass of Spirulina. The present study showed that Spirulina biomass absorbed 95% (approx.) lead at room temparature where the initial concentration was 50 ppm and the pH was 6.0.
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Metallic iron enables an effective heavy metal removal from the single Cu(II), Cr(VI), Zn(II), Ni(II), Pb(II) and Cd(II) solutions and from their mixture under batch conditions and in the flow mode. The kinetic experiments of meta...
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Metallic iron enables an effective heavy metal removal from the single Cu(II), Cr(VI), Zn(II), Ni(II), Pb(II) and Cd(II) solutions and from their mixture under batch conditions and in the flow mode. The kinetic experiments of metal removal and analysis of precipitate formed indicated a more complicated mechanism of the decontamination process as compared to that of ordinary reduction of metal ions with metallic iron. Chemical, FTIR and X-ray analyses of the precipitate show its chemical change with time. Metal ions in solutions were determined using chemical analysis and anodic stripping voltammetry with the bismuth film electrode.
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Urbanization and industrialization are responsible for environmental contamination in the air, water, and soil. These activities also generate large amounts of heavy metal ions in the environment, and these contaminants cause vari...
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Urbanization and industrialization are responsible for environmental contamination in the air, water, and soil. These activities also generate large amounts of heavy metal ions in the environment, and these contaminants cause various types of health issues in humans and other animals. Hexavalent chromium, lead, and cadmium are toxic heavy metal ions that come into the environment through several industrial processes, such as tanning, electroplating, coal mining, agricultural activities, the steel industry, and chrome plating. Several physical and chemical methods are generally used for the heavy metal decontamination of wastewater. These methods have some disadvantages, including the generation of secondary toxic sludge and high operational costs. Hence, there is a need to develop a cost-effective and eco-friendly method for the removal of heavy metal ions from polluted areas. Biological methods are generally considered eco-friendly and cost-effective. This review focuses on heavy metal contamination, its toxicity, and eco-friendly approaches for the removal of heavy metals from contaminated sites.
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Polyrhodanine-coated γ-Fe_2O_3 nanoparticles, synthesized by one-step chemical oxidation polymerization, were applied to the process of removal of heavy metal ions from aqueous solution. Factors influencing the uptake of heavy me...
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Polyrhodanine-coated γ-Fe_2O_3 nanoparticles, synthesized by one-step chemical oxidation polymerization, were applied to the process of removal of heavy metal ions from aqueous solution. Factors influencing the uptake of heavy metal ions such as solution pH, initial metal ion concentration, contact time, and species of metal ions were investigated systematically by batch experiments. The adsorption equilibrium study exhibited that the Hg(II) ion adsorption of polyrhodanine-coated magnetic nanoparticles followed a Freundlich isotherm model than a Langmuir model. The kinetic data of adsorption of Hg(II) ion on the synthesized adsorbents were best described by a pseudo-second-order equation, indicating their chemical adsorption. In addition, the synthesized nano-adsorbents can be repeatedly used with help of an external magnetic field due to their magnetic properties. This work demonstrates that the magnetic polyrhodanine nanoparticles can be considered as a potential recyclable adsorbent for hazardous metal ions from wastewater.
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Abstract The results of an experimental study of the processes of ion exchange sorption and desorption of copper and zinc ions on a composite sorbent are presented. The sorbent is obtained from modified sawdust and chitosan at a m...
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Abstract The results of an experimental study of the processes of ion exchange sorption and desorption of copper and zinc ions on a composite sorbent are presented. The sorbent is obtained from modified sawdust and chitosan at a molar ratio of 1 : 0.4. The average particle size is 1.6 mm. The sorbent has a macroporous structure and contains carboxyl, phenolic hydroxyl groups and amino groups capable of ion exchange with heavy metal ions from solutions. The experimental study is а passing the initial solution through a stationary annular sorbent layer and reading the output curves of ion exchange. The sorbent with a volume of 9.8×10–4 m3 was placed in an annular adsorber between the inner and outer gratings. In the study of the direct ion exchange process, solutions of copper and zinc sulfates with a concentration of 0.05 N with volume velocity 8.1×10–6 m3/s and a sorbent in Na- form were used. Sorbent was regenerated from heavy metal ions with 0.08 N sodium hydroxide solution with volume velocity 3.2×10–6 m3/s. The full exchange capacities of the sorbent, the degree of regeneration of the sorbent and the specific consumption of the regeneration solution were calculated based on the output curves of ion exchange. The analysis of experimental data showed a decrease in the exchange capacity of the sorbent during its repeated use. After five sorption-desorption cycles, the value of the total dynamic exchange capacity of the sorbent decreased for copper ions by 30% and for zinc ions by 25%. The decrease in the exchange capacity is associated with a decrease in the amount of carboxyl and phenolic hydroxyl groups in the sorbent, as well as with the compaction of its structure and, consequently, a decrease in the availability of functional groups.
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Satisfactory sorption capacity towards heavy metals of several physically modified chelating resins at low pH is reported. It was found that the linear sorption isotherms are the most appropriate for describing the sorption of Ni ...
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Satisfactory sorption capacity towards heavy metals of several physically modified chelating resins at low pH is reported. It was found that the linear sorption isotherms are the most appropriate for describing the sorption of Ni and Pb. The data obtained revealed that the chelating resins studied are able to remove selectively copper from a complex synthetic solution containing Fe, Mn and Pb. The regeneration of Lewatit TP 208 by 10% H2SO4 in batch conditions proved to be effective through three consecutive runs of loading-regeneration.
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Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by one-step hydrothermal method using citric acid as carbon source and urea as nitrogen source. beta-cyclodextrin (beta-CD) is a cyclic oligosaccharide with a unique hol...
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Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by one-step hydrothermal method using citric acid as carbon source and urea as nitrogen source. beta-cyclodextrin (beta-CD) is a cyclic oligosaccharide with a unique hollow structure, which is beneficial to the enrichment of metal ions on the electrode surface while reducing the agglomeration of carbon quantum dots and maintaining conductivity. When Cu2+ is coordinated with beta-CD, it can further increase the affinity for Cu2+ and recognize Cu2+ more sensitively. Therefore, we coordinated Cu2+ and beta-CD to form copper ion coordinated beta-cyclodextrin (Cu-beta-CD). By self-assembly, the prepared N-CQDs and Cu-beta-CD combined to form Cu-beta-CD/N-CQDs composites. The electrochemical sensor constructed by Cu-beta-Cd/N-CQDs successfully realizes the selective detection of Cu2+ in the range of 1-125 mu mol l(-1), and the lowest detection limit is 0.094 mu mol l(-1). In the detection of actual water samples, the Recovery of Cu2+ was between 92% and 120%, and the RSD was between 2.3% and 5.2%. Therefore, Cu-beta-CD/N-CQDs composite is expected to be constructed as a non-toxic, pollution-free electrochemical sensor for selective detection of heavy metal Cu2+ ions in water.
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The natural organic matter and the iron and manganese oxides are potential adsorbing
agents of heavy metals in sediments and create a sink for them to control their
bioavailability and mobility in the aquatic environment. The sa...
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The natural organic matter and the iron and manganese oxides are potential adsorbing
agents of heavy metals in sediments and create a sink for them to control their
bioavailability and mobility in the aquatic environment. The salinity and pH of the surrounding
water highly affect the fixation of heavy metals on the river sediments. The
adsorption of copper, lead, and zinc ions in the Brahmaputra river sediment is analyzed
by batch techniques. The parameters controlling these metal ions adsorption are solution
pH, contact time, adsorbent amount, and adsorbate concentration. The equilibrium
adsorption capacities of the sediment particles of the various sizes (< 53, 53–73,
and 74–149 μm) are measured for copper, lead, and zinc ions and extrapolated using
linear Freundlich and Langmuir isotherms. The results provide strong evidence to support
the hypothesis of adsorption mechanism. It is found that the extent of adsorption
is increasing with decreasing particle size, and this may be attributed to the enhancement
of the surface area available for adsorption to occur. The sediment is studied for
metal speciation, for nine heavy metals, to explain their behavior in the five sequential
extraction steps. This is an interesting study as zinc is present in the air, soil, water, and
almost all food items, and industries naturally release zinc into the environment.
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This manuscript deals with the preparation of graphen oxide ? metal oxide composite for the removal of heavy metal ions from water by adsoprtion. Composite of graphene oxide (GO) with zink oxide and titanium oxid
This manuscript deals with the preparation of graphen oxide ? metal oxide composite for the removal of heavy metal ions from water by adsoprtion. Composite of graphene oxide (GO) with zink oxide and titanium oxide has been prepared and analyzed structurally. Further, these composites has been used for the removal of heavy metals such as lead, chromium, mercury etc. from water. Metal oxide GO composites has been found efficient towards removal of heavy metal ions.
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