Harmful Impacts of Heavy Metals and Utility of Biosorption Technique for Their Removal from Wastewater: A Review

The increasing number of efluents discharged from the source of water (urban, industrial, agricultural etc.), is resulting in a higher concentration of heavy metals in the source. Heavy metals have a density of over 5g/cm3 to the metals. These are toxic, mutagenic, carcinogenic and resistant in watery and non-aquatic environments and impact water and non-water bodies seriously by substituting the basic metals of the same function. The extraction from the wastewater can be done in numerous techniques for example using an ion replacement, membrane filtration, osmosis, etc. This study discusses the adverse effects of heavy metals on the human body, the benefits of biosorption over traditional approaches for removal of heavy metals, the different biosorbents used to extract heavy metals and concerning issues regarding its commercial use, offering a wider viewpoint for the diversity of biosorbents and utilization of biosorption technique. It is evident from the profound literature survey that pH, biosorbent particle size, contact time, initial metal ion concentration, presence of chelating ligands etc. are some factors that affect the rate and extent of biosorption.

Evaluation of anticancer activities varying ligand’s substituents in Co(II/III)-picolyl phenolate derivatives: Synthesis, characterization, DFT, DNA cleavage and molecular docking studies

The reaction between 2-(pyridine-2-ylmethoxy)-benzaldehyde (L) and various primary amines furnish tridentate (L1 to L3) and tetradentate (L4) chelating ligands. The choice of different primary amines in the condensation reaction incorporates...

Slow relaxations of Dy(III) single-ion magnets dominated by simultaneous binding of chelating ligands in low-symmetry ligand-fields

Electronic effect and geometry distortion of low-symmetry ligand-field on anisotropy barrier (Ueff) of spin reversal have been compared in three Dy(III) single-ion magnets through simultaneous binding of chelating ligands. The...

Experimental and theoretical insights into the photomagnetic effects in trinuclear and ionic Cu(II)-Mo(IV) systems

The crystal engineering of octacyanidomolybdate(IV) ions and copper(II) complexes with two types of chelating ligands: multidentate blocking, tren = (tris(2 aminoethyl)amine, and bidentate capable of forming unusual organic bridges, tn...

Synthesis, characterization and evaluation of antibacterial activity of copper(II)-curcumin complex against staphylococcus aureus

Curcumin, a phytochemical from turmeric, and its derivatives have been extensively investigated from both chemical and biological strategies. However, the main problem encountered while using curcumin in clinical trials is its poor solubility and rapid degradation, resulting in its low levels in tissues, thus decreasing the medicinal effect of curcumin. To overcome these problems several synthetic approaches have been carried out to prepare new derivatives possessing better properties. Curcumin as a β-diketone ligand can act as chelating ligands toward a variety of metals to form stable complexes. Some studies showed that a metal-curcumin complex displayed potential medicinal activities. In this work, a copper(II)-curcumin complex was synthesized in a two-step procedure: (i) curcumin was separated from commercial turmeric powder using chromatography techniques and (ii) the copper(II) chloride (1 eq.) and pure curcumin (2 eq.) were mixed together in ethanol. The mixture was stirred at 60 oC for 3 hours to afford a stoichiometric copper(II)-curcumin complex. The curcumin ligand and its copper(II) complex were characterized by UV-Vis, IR, NMR spectroscopic methods, from which it was found that copper atoms are coordinated through keto-enol groups of two curcumin molecules. The ground state spectral features of the copper(II)-curcumin complex were consistent with that of the 1:2 copper(II)-curcumin complex. The antibacterial activities of curcumin ligand and its complex were evaluated against Staphylococcus aureus (ATCC 6538) using a well diffusion method on nutrient agar. The results showed that the inhibitory activity was not observed for free curcumin at any concentrations while the copper(II)-curcumin complex exhibited the inhibition zones (mm) of 7.8, 11.6 and 14.9 at various concentrations (mg/mL) of 1.0, 5.0 and 15.0, respectively.

Giant single-crystal-to-single-crystal transformations associated with chiral interconversion induced by elimination of chelating ligands

Numerous single crystals that exhibit single-crystal-to-single-crystal (SCSC) transformations have been reported, and some of them show great promise for application to advanced adsorption materials, magnetic switches, and smart actuators. However, the development of single crystals with super-adaptive crystal lattices capable of huge and reversible structural change remains a great challenge. In this study, we report a ZnII complex that undergoes giant SCSC transformation induced by a two-step thermal elimination of ethylene glycol chelating ligands. Although the structural change is exceptionally large (50% volume shrinkage and 36% weight loss), the single-crystal nature of the complex persists because of the multiple strong hydrogen bonds between the constituent molecules. This allows the reversible zero-dimensional to one-dimension and further to three-dimensional structural changes to be fully characterized by single-crystal X-ray diffraction analyses. The elimination of chelating ligands induces a chiral interconversion in the molecules that manifests as a centric-chiral-polar symmetric variation of the single crystal. The study not only presents a unique material, featuring both a periodic crystal lattice and gel-like super-ductility, but also reveals a possible solid-state reaction method for preparing chiral compounds via the elimination of chelating ligands.

Effect of Adding Chelating Ligands on the Catalytic Performance of Rh-Promoted MoS2 in the Hydrodesulfurization of Dibenzothiophene

Hydrodesulfurization (HDS) is a widely used process currently employed in petroleum refineries to eliminate organosulfur compounds in fuels. The current hydrotreating process struggles to remove organosulfur compounds with a steric hindrance due to the electronic nature of the current catalysts employed. In this work, the effects of adding chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) to rhodium (Rh) and active molybdenum (Mo) species for dibenzothiophene (DBT) HDS catalytic activity was evaluated. HDS activities followed the order of RhMo/ɣ-Al2O3 (88%) > RhMo-AA/ɣ-Al2O3 (73%) > RhMo-CA/ɣ-Al2O3 (72%) > RhMo-EDTA/ɣ-Al2O3 (68%). The observed trend was attributed to the different chelating ligands with varying electronic properties, thus influencing the metal–support interaction and the favorable reduction of the Mo species. RhMo/ɣ-Al2O3 offered the highest HDS activity due to its (i) lower metal–support interaction energy, as observed from the RhMo/ɣ-Al2O3 band gap of 3.779 eV and the slight shift toward the lower BE of Mo 3d, (ii) increased Mo-O-Mo species (NMo-O-Mo ~1.975) and (iii) better sulfidation of Rh and MoO in RhMo/ɣ-Al2O3 compared to the chelated catalysts. The obtained data provides that HDS catalytic activity was mainly driven by the structural nature of the RhMo-based catalyst, which influences the formation of more active sites that can enhance the HDS activity.

I. Magnesium Promoted Coupling of Carbodiimides and Terminal Acetylenes, II. Bismuth Compounds Supported by Di(amido) Chelating Ligands

<p>The work presented in this thesis is divided into two parts, both of which investigate the chemistry of main group elements supported by N,N'-donor ligands. Part 1 investigates the use of Mg(mesC{NCy}₂)(N{SiMe₃}₂)(THF) (mes = 2,4,6- Me₃C₆H₃, Cy = C₆H₁₁) as a pre-catalyst for the coupling of terminal acetylenes to carbodiimides. A catalytic cycle for the reaction is proposed, based on a series of stoichiometric reactions. Ligand redistribution via Schlenk equilibria is a prominent feature of the proposed catalytic cycle. The scope of catalysis was also investigated, indicating a strong dependence on the sterics and electronics of both the carbodiimide and the terminal acetylene. Investigation of other magnesium species identified other pathways into the catalytic cycle. Part 2 explores the derivitisation of Bi(Me₂Si{NAr})Cl (Ar = 2,6-i-Pr₂C₆H₃) to form a number of novel bismuth(III) species of the general formula Bi(Me₂Si{NAr})X (X = alkyl, aryl, amide, aryloxide, phosphide). In addition, a number of cationic bismuth species have been isolated from the reaction of Bi(Me₂Si{NAr})Cl with ECl₃ (E = Al, Ga). Preliminary investigations reveal that the amide and aryloxide derivatives are active as initiators for the ring-opening polymerisation of lactide and ε-caprolactone. A number of bismuth(III) compounds bearing the related di(amido)ether ligands [O(Me₂Si{NAr})₂]²⁻ have also been synthesised.</p>

I. Magnesium Promoted Coupling of Carbodiimides and Terminal Acetylenes, II. Bismuth Compounds Supported by Di(amido) Chelating Ligands

<p>The work presented in this thesis is divided into two parts, both of which investigate the chemistry of main group elements supported by N,N'-donor ligands. Part 1 investigates the use of Mg(mesC{NCy}₂)(N{SiMe₃}₂)(THF) (mes = 2,4,6- Me₃C₆H₃, Cy = C₆H₁₁) as a pre-catalyst for the coupling of terminal acetylenes to carbodiimides. A catalytic cycle for the reaction is proposed, based on a series of stoichiometric reactions. Ligand redistribution via Schlenk equilibria is a prominent feature of the proposed catalytic cycle. The scope of catalysis was also investigated, indicating a strong dependence on the sterics and electronics of both the carbodiimide and the terminal acetylene. Investigation of other magnesium species identified other pathways into the catalytic cycle. Part 2 explores the derivitisation of Bi(Me₂Si{NAr})Cl (Ar = 2,6-i-Pr₂C₆H₃) to form a number of novel bismuth(III) species of the general formula Bi(Me₂Si{NAr})X (X = alkyl, aryl, amide, aryloxide, phosphide). In addition, a number of cationic bismuth species have been isolated from the reaction of Bi(Me₂Si{NAr})Cl with ECl₃ (E = Al, Ga). Preliminary investigations reveal that the amide and aryloxide derivatives are active as initiators for the ring-opening polymerisation of lactide and ε-caprolactone. A number of bismuth(III) compounds bearing the related di(amido)ether ligands [O(Me₂Si{NAr})₂]²⁻ have also been synthesised.</p>