In‐vitro study on the efficacy of tannin fractions of edible nuts as antioxidants

Tannin fractions were isolated from crude acetonic extracts of defatted walnut, hazelnut and almond kernels using Sephadex LH‐20 column chromatography. The obtained material was characterized by content of total phenolics and electrophoretic separations using capillary zone electrophoresis (CZE). The antioxidant activities of the tannin fractions were analyzed by several methods: DPPH and ABTS assays, photochemiluminescence (PCL) method, as well as in two lipid model systems: emulsion with β‐carotene‐linoleic acid and L ‐α‐lecithin liposomes. The contents of total phenolics in the tannin fractions of walnuts, hazelnuts and almonds were 550, 329 and 83 mg catechin eq/g, respectively. The electrophoretic profiles of hazelnut and almond tannin fractions were similar, in contrast to the walnut profile. All analyzed fractions exhibited strong antioxidant properties. The antioxidant capacity of lipid‐soluble (ACL) compounds determined by PCL method was the highest for the fraction isolated from walnuts – 7.35 mmol Trolox eq/g. The DPPH radical and the ABTS radical cation were scavenged by the walnut tannin fraction with a higher efficacy than by the two other fractions. EC₅₀ values of the DPPH method were 1.8 times higher for the hazelnut fraction and 2.3 times higher for the almond fraction when compared to the walnut tannins. In turn, the total antioxidant activity values were 8.17, 2.82 and 1.98 mmol Trolox eq/g for the walnut, hazelnut and almond fractions, respectively. On the other hand, in both lipid models applied, lower antioxidant activity of walnut tannins than of hazelnut tannins was noted. The antioxidant effect of almond tannins was weaker or similar than that of walnut tannins in the β‐carotene‐linoleic acid emulsion and the L ‐α‐lecithin liposomal system, respectively.     

Adsorption of Cu(II) from aqueous solutions by tannins immobilized on collagen

Novel adsorbents were prepared by immobilizing tannins on collagen fibre matrices. Their adsorption properties, including adsorption equilibrium, adsorption kinetics, and column adsorption kinetics to Cu(II) were investigated. Immobilized Myrica rubra tannin and black wattle tannin exhibited significantly higher adsorption capacity than larch tannin and the adsorption isotherms of these three immobilized tannins can be described by the Freundlich model. Detailed adsorption studies of immobilized black wattle tannin to Cu(II) indicated that temperature had little effect on the adsorption isotherms whereas the effect of pH was significant. Adsorption rate data fitted well to a pseudo‐second‐order rate model, and the adsorption capacity calculated by this model was consistent with the result of actual measurement at relatively higher adsorption temperatures. Immobilized black wattle tannin also had excellent column adsorption kinetic properties and high binding capacity. The adsorptivity of the column was stable even after repeated adsorption–desorption cycles. Copyright © 2004 Society of Chemical Industry     

Water-soluble oxidized starch in complexation of Fe(III), Cu(II), Ni(II) and Zn(II) ions

The structure of the bromate-oxidized wheat starch (OS) contains partly opened glucose units with carbonyl and carboxyl groups at C2-, C3- or C6-positions. OS with a variable degree of oxidation (DO) was studied in alkaline conditions as a water-soluble complexing agent for Fe(III), Cu(II), Ni(II) and Zn(II) ions, which are common in various wastewaters. Complexation was studied by inductively coupled plasma-optical emission spectrometry (ICP–OES) in a single metal ion or multi-metal ion solutions. The DO affected the efficiency of the complexation with metal ions. OS with the high DO (carboxyl and carbonyl DO of 0.72 and 0.23, respectively) complexed and held Fe(III) or Zn(II) ions in a soluble form effectively in 0.5 mM single ion alkaline solution with the molar ratio of 0.65:1 of oxidized starch-to-metal ion (OS-to-M). The OS-to-M molar ratio of 1.3:1 was required to form a soluble complex with Cu(II) or Ni(II) ions. These complexes were thermally stable at the temperature range of 20–60 °C. OS with the low DO (carboxyl and carbonyl DO 0.47 and 0.17, respectively) complexed Zn(II) ions highly, Cu(II) and Ni(II) ions poorly and Fe(III) ions only partly. In the multi-metal ion solution of OS the solubility of these metal ions improved with the increasing DO of starch, which followed the same tendency as was observed in the single metal ion systems. The increased molar ratio of OS-to-M improved the complexation and solubility of the metal ions in all multi-metal ion series. As the soluble multi-metal ion complexes were reanalyzed after 7 days, all solutions had kept the high complexation and solubility of metal ions (ca. 90%). Complexation by OS did not show a selective binding of the ions in the multi-metal ion solution. It was concluded that the flexible, opened ring structure units of OS prevented the selective binding to metal ions but made the complexes highly stable. Titrimetric studies of OS–Fe(III) complexation showed that each anhydroglucose unit of OS had more than one coordination site and as the content of OS increased, the free sites coordinated to Fe(III) ions and formed cross-linked starch structures.     

Chemical Characterization of Virgin Almond and Hazelnut Oils and Their By‐Products

Various cultivars of almonds (“Ferragnes,” “Guara,” “Largueta,” and “Marcona”) and hazelnuts (“Negret,” “Pauetet,” and “Tonda”), particularly their virgin oils and by‐products, are evaluated in this study. The almond and hazelnut virgin oils present high contents of oleic acid (59–73% and 76–80%, respectively) and α‐tocopherol (420–542 and 310–378 mg kg^–1, respectively), as compared with other virgin vegetable oils. Aldehydes are the major contributors to their aromatic profile (54–74% almond oil and 30–40% hazelnut oil of total content), especially, benzaldehyde in almond oils (1.35–7.52 mg kg^–1), and hexanal in hazelnut oils (0.99–1.27 mg kg^–1). Statistical differences exist between the virgin almond and hazelnut oils and their varieties, for most of the chemical compounds studied. While all the nut varieties are high in polar phenolic compounds, “Ferragnes” almonds (1262 mg kg^–1) and “Negret” hazelnuts (1720 mg kg^–1) stand out. Accordingly, high antioxidant activity is also observed. Finally, the residual cakes may be considered a good source of polar phenolic compounds (823–2064 mg kg^–1 almond cakes, 2261–4179 mg kg^–1 hazelnut cakes), possessing high antioxidant capacity with potential applications of these by‐products as functional ingredients in food and non‐food formulations. Practical Applications: Virgin nut oils are gaining consumers’ preference due to their unique organoleptic attributes and potential health effects. It is therefore very relevant to establish their specific chemical composition, directly related to their properties, and that are greatly affected by the cultivar.     

Preparation and characterization of magnetic polymethylmethacrylate microbeads carrying ethylene diamine for removal of Cu(II), Cd(II), Pb(II), and Hg(II) from aqueous solutions

Magnetic polymethylmethacrylate (mPMMA) microbeads carrying ethylene diamine (EDA) were prepared for the removal of heavy metal ions (i.e., copper, lead, cadmium, and mercury) from aqueous solutions containing different amount of these ions (5–700 mg/L) and at different pH values (2.0–8.0). Adsorption of heavy metal ions on the unmodified mPMMA microbeads was very low (3.6 μmol/g for Cu(II), 4.2 μmol/g for Pb(II), 4.6 μmol/g for Cd(II), and 2.9 μmol/g for Hg(II)). EDA‐incorporation significantly increased the heavy metal adsorption (201 μmol/g for Cu(II), 186 μmol/g for Pb(II), 162 μmol/g for Cd(II), and 150 μmol/g for Hg(II)). Competitive adsorption capacities (in the case of adsorption from mixture) were determined to be 79.8 μmol/g for Cu(II), 58.7 μmol/g for Pb(II), 52.4 μmol/g for Cd(II), and 45.3 μmol/g for Hg(II). The observed affinity order in adsorption was found to be Cu(II) > Pb(II) > Cd(II) > Hg(II) for both under noncompetitive and competitive conditions. The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. The optimal pH range for heavy‐metal removal was shown to be from 5.0 to 8.0. Desorption of heavy‐metal ions was achieved using 0.1 M HNO₃. The maximum elution value was as high as 98%. These microbeads are suitable for repeated use for more than five adsorption‐desorption cycles without considerable loss of adsorption capacity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 81–89, 2000     

Sorption of Pb(II), Cd(II) and Zn(II) by iminodiacetate chelating resins in non-competitive and competitive conditions

Two chelating resins (CRs) bearing iminodiacetate (IDA) groups derived from acrylonitrile - divinylbenzene (AN-DVB) copolymers having 10 and 15 wt.% nominal cross-linking degrees and a high mobility of the functional groups caused by the presence of a longer spacer between the matrix and the IDA groups were synthesized and tested as sorbents for heavy metal ions like: Pb(II), Cd(II) and Zn(II) from aqueous solutions by batch and column techniques. Experimental data obtained from batch equilibrium tests have been analyzed by two isotherm models: Freundlich and Langmuir. The overall adsorption tendency of CRs toward Pb(II), Cd(II) and Zn(II), under non-competitive conditions, followed the order: Cd(II) > Pb(II) > Zn(II). Selectivity studies were performed in ternary mixture of Pb(II), Cd(II) and Zn(II) to check if the synthesized CRs can be useful for selective separation of heavy metal cations. The results revealed that the CRs with IDA groups exhibited high selectivity toward Pb(II), both in batch and column techniques. Regeneration of the resins was achieved using 0.1 M HCl solution.     

Synergistic Solvent Extraction and Transport of Zn(II) and Cu(II) across Polymer Inclusion Membranes with a Mixture of TOPO and Aliquat 336

Separation of zinc(II) and copper(II) ions from aqueous solutions by synergistic extraction and transport through polymer inclusion membranes (PIMs) has been investigated. A mixture of trioctylphosphine oxide (TOPO) and trioctymethylammonium chloride (Aliquat 336) was used as a selective extractant as well as an ion carrier in polymer membranes. The effects of hydrochloric acid concentration in the aqueous phase and extractants concentration in the organic phase on the separation process of zinc(II) and copper(II) ions have been studied. Zn(II) ions were successfully separated from Cu(II) ions in solvent extraction process using 0.025 M TOPO and 0.06 M Aliquat 336 in kerosene. Polymer inclusion membranes (PIMs) containing a mixture of TOPO and Aliquat 336 as the ion carrier have been prepared and the facilitated transport of Zn(II) and Cu(II) ions has been studied. The influence of membrane composition on the transport kinetic of Zn(II) and Cu(II) has been evaluated. Zn(II) ions were preferably transported from the aqueous solutions containing Cu(II) and above 87% of Zn(II) ions were effectively recovered from the 0.5 M HCl solution as the source phase through PIM into 0.5 M H₂SO₄ as the stripping phase.     

Removal of Cu(II) and Zn(II) Using Lignocellulosic Fiber Derived from Citrus reticulata (Kinnow) Waste Biomass

Abstract

The biosorption of Cu(II) and Zn(II) using dried untreated and pretreated Citrus reticulata waste biomass were evaluated. The Cu(II) and Zn(II) sorption were found to be dependent on the solution pH, the biosorbent dose, the biosorbent particle size, the shaking speed, the temperature, the initial metal ions (800 mg/L), and the contact time. Twenty-eight physical and chemical pretreatments of Citrus reticulata waste biomass were evaluated for the sorption of Cu(II) and Zn(II) from aqueous solutions. The results indicated that biomass pretreated with sulphuric acid and EDTA had maximum Cu(II) and Zn(II) uptake capacity of 87.14 mg/g and 86.4 mg/g respectively. Moreover, the Langmuir isotherm model fitted well than the Freundlich model with R ² > 0.95 for both metal ions. The sorption of Cu(II) and Zn(II) occurred rapidly in the first 120 min and the equilibrium was reached in 240 min. FTIR and SEM studies were also carried out to investigate functional groups present in the biomass and the surface morphological changes of biomass.     

Separation and concentration processes of solutions of Co(II), Ni(II), Cr(III), Fe(III) and Mn(II) by extraction with toluene-dissolved rosin

The extraction and stripping of Co(II), Ni(II), Cr(III) and Fe(III) from aqueous solutions by rosin dissolved in toluene has been investigated. Results obtained show that rosin is better extractant than abietic or n-lauric acids under comparable conditions. From these results, and the data of Mn(II) solvent extraction studied previously under the same conditions, a separation and concentration process for these five cations in aqueous solutions has been designed. Saturated solutions of Fe(III), Cr(III), Mn(II) and finally Co(II) and Ni(II) have been obtained successively by extraction and stripping, by addition of ammonium hydroxide to obtain the appropriate pH value, and by modifying adequately the organic phase/aqueous phase volume ratio.     

Zn-Enhanced Asp-Rich Antimicrobial Peptides: N-Terminal Coordination by Zn(II) and Cu(II), Which Distinguishes Cu(II) Binding to Different Peptides

The antimicrobial activity of surfactant-associated anionic peptides (SAAPs), which are isolated from the ovine pulmonary surfactant and are selective against the ovine pathogen Mannheimia haemolytica, is strongly enhanced in the presence of Zn(II) ions. Both calorimetry and ITC measurements show that the unique Asp-only peptide SAAP3 (DDDDDDD) and its analogs SAAP2 (GDDDDDD) and SAAP6 (GADDDDD) have a similar micromolar affinity for Zn(II), which binds to the N-terminal amine and Asp carboxylates in a net entropically-driven process. All three peptides also bind Cu(II) with a net entropically-driven process but with higher affinity than they bind Zn(II) and coordination that involves the N-terminal amine and deprotonated amides as the pH increases. The parent SAAP3 binds Cu(II) with the highest affinity; however, as shown with potentiometry and absorption, CD and EPR spectroscopy, Asp residues in the first and/or second positions distinguish Cu(II) binding to SAAP3 and SAAP2 from their binding to SAAP6, decreasing the Cu(II) Lewis acidity and suppressing its square planar amide coordination by two pH units. We also show that these metal ions do not stabilize a membrane disrupting ability nor do they induce the antimicrobial activity of these peptides against a panel of human pathogens.     

Removal of Copper(II) and Zinc(II) from Aqueous Solutions Using a Lignocellulosic-Based Polymeric Adsorbent Containing Amidoxime Chelating Functional Groups

In this study, the adsorption of Cu(II) and Zn(II) ions from aqueous solutions onto amidoximated polymerized banana stem (APBS) has been investigated. Infrared spectroscopy was used to confirm graft copolymer formation and amidoxime functionalization. The different variables affecting the sorption capacity such as pH of the solution, adsorption time, initial metal ion concentration, and temperature have been investigated. The optimum pH for maximum adsorption was 10.5 (99.99%) for Zn²⁺ and 6.0 (99.0%) for Cu²⁺ at an initial concentration of 10 mg L^?1. Equilibrium was achieved approximately within 3 h. The experimental kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models and are well fitted with pseudo- second-order kinetics. The thermodynamic activation parameters such as ΔG^o, ΔH^o, and ΔS^o were determined to predict the nature of adsorption. The temperature dependence indicates an exothermic process. The experimental isotherm data were well fitted to the Langmuir model with maximum adsorption capacities of 42.32 and 85.89 mg g^?1 for Cu(II) and Zn(II), respectively, at 20°C. The adsorption efficiency was tested using industrial effluents. Repeated adsorption/regeneration cycles show the feasibility of the APBS for the removal of Cu(II) and Zn(II) ions from water and industrial effluents.     

Removal of Cu(II) and Fe(III) from aqueous solutions by dead sulfate reducing bacteria

The biosorption properties of dead sulfate reducing bacteria (SRB) for the removal of Cu(II) and Fe(III) from aqueous solutions was studied. The effects of the biosorbent concentration, the initial pH value and the temperature on the biosorption of Cu(II) and Fe(III) by the SRB were investigated. FTIR analysis verified that the hydroxyl, carbonyl and amine functional groups of the SRB biosorbent were involved in the biosorption process. For both Cu(II) and Fe(III), an increase in the SRB biosorbent concentration resulted in an increase in the removal percentage but a decrease in the amount of specific metal biosorption. The maximum specific metal biosorption was 93.25 mg?g^–1 at pH 4.5 for Cu(II) and 88.29 mg?g^–1 at pH 3.5 for Fe(III). The temperature did not have a significant effect on biosorption. In a binary metal system, the specific biosorption capacity for the target metal decreased when another metal ion was added. For both the single metal and binary metal systems, the biosorption of Cu(II) and Fe(III) onto a SRB biosorbent was better represented by a Langmuir model than by a Freundlich model.     

Selective Transport of Cu(II) across a Polymer Inclusion Membrane with 1-Alkylimidazole from Nitrate Solutions

The selective transport of copper(II), zinc(II), cobalt(II), and nickel(II) ions from nitrate solutions across polymer inclusion membranes (PIMs), which consist of cellulose triacetate as polymeric support, o-nitrophenyl pentyl ether as plasticizer, and 1-alkylimidazole (alkyl from hexyl- to decyl) as ion carrier was reported. PIM was characterized by using atomic force microscopy (AFM) technique. The results show that Cu(II) can be separated very effectively from other transition metal cations as Zn(II), Co(II), and Ni(II) (at a concentration of 10^?3 mol/dm³ each). Alkyl substituents at position 1 of the imidazole ring have been found to affect the hydrophobic properties and initial flux of the transported metal ions. The efficiency of separation of metal ions by 1-alkylimidazole followed the sequence: Cu(II) > Zn(II) > Co(II) > Ni(II). The highest selectivity coefficient for Cu(II) was found with 1-hexylimidazole and its 1 mol/dm³ solution in PIM. Separation of the ions was more effective for the nitrates(V) than for chlorides.     

Antibacterial Co(II), Cu(II), Ni(II) and Zn(II) Complexes of Thiadiazoles Schiff Bases

Schiff bases were obtained by condensation of 2-amino-l,3,4-thiadiazole with 5-substituted-salicylaldehydes which were further used to obtain complexes of the type [M(L)(2)]Cl(2), where M=Co(II), Cu(II), Ni(II) or Zn(II). The new compounds described here have been characterized by physical, spectral and analytical data, and have been screened for antibacterial activity against several bacterial strains such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The antibacterial potency of these Schiff bases increased upon chelation/complexation, against the tested bacterial species, opening new aproaches in the fight against antibiotic resistant strains.     

A first report of the complexes of 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarboxymethoxy-26,28-dihydroxycalix[4]arene with Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II)

Totally six dinuclear complexes of Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) of calix[4]arene derivatized with two pendants possessing terminal –COOH functions at two of its alternate phenolic –OH groups were synthesized for the first time and were well characterized.     

Voltammetric investigation of polyelectrolyte-Cu(II) complexes

The complexation behaviours of poly(N-vinylcarbazole) (PNVCz), poly(acrylic acid) (PAA) poly(itaconic acid) (PIA) and their copolymers, synthesized by using different initial monomer compositions, with Cu(II) ions were investigated by the voltammetric technique. Their solutions were prepared in THF-water mixture according to the water-insoluble nature of PNVCz and its copolymers. The polymeric ligand-Cu(II) interactions, i.e. complex formations were studied as a function of copper ion concentration and copolymer composition. It was observed that although the cyclic voltammogram (CV) of Cu(II) alone in THF-water mixture was characterized by one redox wave, which has an irreversible nature, it became more reversible in the presence of polymer. Further, the CV results indicated the presence of two different electron transfer mechanisms, depending on the n _COOH/n _Cu(II) ratio and the carboxyl content of the copolymers.     

Adsorption performance and physicochemical mechanism of MnO2-polyethylenimine-tannic acid composites for the removal of Cu(II) and Cr(VI) from aqueous solution

In this work, an adsorbent, which we call MnPT, was prepared by combining MnO₂, polyethylenimine and tannic acid, and exhibited efficient performance for Cu(II) and Cr(VI) removal from aqueous solution. The oxygen/nitrogen-containing functional groups on the surface of MnPT might increase the enrichment of metal ions by complexation. The maximum adsorption capacities of MnPT for Cu(II) and Cr(VI) were 121.5 and 790.2 mg·g⁻¹, respectively. The surface complexation formation model was used to elucidate the physicochemical interplay in the process of Cu(II) and Cr(VI) co-adsorption on MnPT. Electrostatic force, solvation action, adsorbate–adsorbate lateral interaction, and complexation were involved in the spontaneous adsorption process. Physical electrostatic action was dominant in the initial stage, whereas chemical action was the driving force leading to adsorption equilibrium. It should be noted that after adsorption on the surface of MnPT, Cr(VI) reacted with some reducing functional groups (hydroxylamine-NH₂) and was converted into Cr(III). The adsorption capacity declined by 12% after recycling five times. Understanding the adsorption mechanism might provide a technical basis for the procedural design of heavy metal adsorbents. This MnPT nanocomposite has been proven to be a low-cost, efficient, and promising adsorbent for removing heavy metal ions from wastewater.     

Chitosan functionalized with 2[-bis-(pyridylmethyl) aminomethyl]4-methyl-6-formyl-phenol: equilibrium and kinetics of copper (II) adsorption

The complexation agent 2[-bis-(pyridylmethyl) aminomethyl]-4-methyl-6-formyl-phenol (HL) was immobilized in chitosan in order to obtain a new adsorbent material to be employed in studies on adsorption and pre-concentration of Cu(II). The chitosan modified by the complexation agent was characterized by infrared spectroscopy, DSC and TGA. The studies were conducted as a function of the pH of the medium and the mechanism of Cu(II) adsorption in the solid phase was analyzed utilizing several kinetic models. The parameters for the adsorption of Cu(II) ions by chitosan-HL were determined with a Langmuir isotherm, the maximum saturation capacity of the monolayer being 109.4 mg of Cu(II) per gram of polymer. Electron paramagnetic resonance spectroscopy revealed that Cu^II ions coordinate to the donor atoms of the HL ligand anchored to the surface of the polymer forming a stable chelate complex in the solid state.     

Fast removal of Pb(II) and Cu(II) from contaminated water by groundwater treatment waste: impact of sorbent composition

ABSTRACT

A non-hazardous groundwater treatment waste (GWTW) was examined as a low-cost sorbent for Pb(II) and Cu(II) ions. The content of the dominant elements in GWTW was as follows: 78% Fe₂O₃, 7.4% P₂O₅, 7.4% CaO and 5.2% SiO₂. The removal of Pb(II) and Cu(II) was fast, and more than 67–95% of ions were accumulated by GWTW during the first 3 min. The sorption capacity of GWTW depends on solution pH, concentration and temperature. Equilibrium data fitted well with Langmuir–Freundlich and Langmuir-partition models. The inherently formed nano-adsorbent could be utilized for the treatment of water contaminated with Pb(II) and Cu(II) ions.     

Calcined tetrabutylammonium kaolinite and montmorillonite and adsorption of Fe(II), Co(II) and Ni(II) from solution

Kaolinite and montmorillonite were modified with tetrabutylammonium (TBA) bromide, followed by calcination. The structural changes were monitored with XRD, FTIR, surface area and cation exchange capacity measurements. The modified clay minerals were used for adsorption of Fe(III), Co(II) and Ni(II) ions from aqueous solution under different conditions of pH, time and temperature. The uptake of the metal ions took place by a second order kinetics. The modified montmorillonite had a higher adsorption capacity than the corresponding kaolinite. The Langmuir monolayer capacities for the modified kaolinite and montmorillonite were Fe(III): 9.3 mg g^− 1 and 22.6 mg g^− 1; Co(II): 9.0 mg g^− 1 and 22.3 mg g^− 1; and Ni(II): 8.4 mg g^− 1 and 19.7 mg g^− 1. The modified kaolinite interacted with Co(II) in an endothermic manner, but all the other interactions were exothermic. The decrease of the Gibbs energy in all the cases indicated spontaneous adsorption.