Extraction of cadmium from solutions containing various heavy metal ions by Amberlite LA-2

In present study, selective extraction of cadmium from acidic leach solutions, containing various heavy metal ions, by emulsion liquid membrane (ELM) is studied. For this reason, the zinc plant copper cake was leached with sulfuric acid and main acidic leach solution containing Zn(II), Cu(II), Fe(II), Cd(II), Co(II) and Ni(II) ions was obtained. After Zn(II), Cu(II), Fe(II) and Cd(II) ions in the acidic leach solution were separated, the important parameters influencing the extent of cadmium extraction were investigated and optimum conditions were determined. Cadmium extraction was influenced by number of parameters like initial metal ion concentration, mixing speed, phase ratio, extractant concentration, surfactant concentration, the stripping solution type and concentration, and the feed solution acid concentration. The optimum values of parameter above mentioned were used and cadmium in the acidic leach solution containing 650 mg Cd/L, 365 mg Co/L, 535 mg Ni/L, and 1260 mg Zn/L was almost completely extracted within 10 min. The results showed that it is possible to extract 99% of cadmium after 10 min contact time by using ELM from aqueous solutions, containing Fe(II), Al(III), Cu(II), Zn(II), Pb(II), Co(II) and Ni(II) ions, at the optimum operating conditions.     

Metal sorption on macroporous poly(GMA-co-EGDMA) modified with ethylene diamine

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), poly(GMA-co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine (EDA). The samples were characterized by mercury porosimetry, FT-IR spectroscopy and elemental analysis. The sorption rate of the modified copolymer, poly(GMA-co-EGDMA)-en for Cu(II) ions determined under non-competitive conditions was relatively rapid, i.e. the maximum capacity was reached within 30 min. Batch sorption capacities for Cu(II), Fe(II), Mn(II), Cd(II), Zn(II), Pb(II), Cr(III) and Pt(IV) ions were determined under non-competitive conditions in the pH range 1.25–5.5 at room temperature. The maximum sorption capacities of poly(GMA-co-EGDMA)-en under non-competitive conditions were 1.30 mmol/g for Pt(IV) at pH 5.5, 1.10 mmol/g for Cu(II) at pH 5.5, 1.06 mmol/g for Pb(II) at pH 1.25 and 0.67 mmol/g for Cd(II) ions at pH 5.5. The selectivity of poly(GMA-co-EGDMA)-en towards Cu(II), Co(II), Ni(II), Pb(II) and Pt(IV) ions was investigated under competitive conditions. Poly(GMA-co-EGDMA)-en showed high selectivity for Pt(IV) over Cu(II), Co(II), Ni(II) and Pb(II) ions at pH 2.1. At pH 5.5, the metal sorption capacities of poly(GMA-co-EGDMA)-en decreased in the order: Cu(II) > Co(II) > Pt(IV) ≈ Ni(II) > Pb(II). Regeneration of the Cu(II), Ni(II) and Pb(II) loaded poly(GMA-co-EGDMA)-en with 2 M H₂SO₄ showed that the polymer can be reused in several sorption/desorption cycles.     

Chitosan modified with Reactive Blue 2 dye on adsorption equilibrium of Cu(II) and Ni(II) ions

This study aimed at immobilizing Reactive Blue 2 (RB 2) dye in chitosan microspheres through nucleophilic substitution reaction. The adsorbent chemical modification was confirmed by Raman spectroscopy and thermogravimetric analysis. This adsorption study was carried out with Cu(II) and Ni(II) ions and indicated a pH dependence, while the maximum adsorption occurred around pH 7.0 and 8.5, respectively. The pseudo second-order kinetic model resulted in the best fit with experimental data obtained from Cu(II) (R = 0.997) and Ni(II) (R = 0.995), also providing a rate constant, k₂, of 4.85 × 10⁻⁴ and 3.81 × 10⁻⁴ g (mg min)⁻¹, respectively, thus suggesting that adsorption rate of metal ions by chitosan-RB 2 depends on the concentration of ions on adsorbent surface, as well as on their concentration at equilibrium. The Langmuir and Freundlich isotherm models were employed in the analysis of the experimental data for the adsorption, in the form of linearized equations. Langmuir model resulted in the best fit for both metals and maximum adsorption was 57.0 mg g⁻¹ (0.90 mmol g⁻¹) for Cu(II) and 11.2 mg g⁻¹ (0.19 mmol g⁻¹) for Ni(II). The Cu(II) and Ni(II) ions were desorbed from chitosan-RB 2 with aqueous solutions of EDTA and H₂SO₄, respectively.     

Heavy metals uptake from aqueous solutions and industrial wastewaters by humic acid-immobilized polymer/bentonite composite: Kinetics and equilibrium modeling

This study explored the feasibility of utilizing a novel adsorbent, humic acid-immobilized-amine-modified polyacrylamide/bentonite composite (HA-Am-PAA-B) for the adsorption of Cu(II), Zn(II) and Co(II) ions from aqueous solutions. The FTIR and XRD analyses were done to characterize the adsorbent material. The effects of pH, contact time, initial adsorbate concentration, ionic strength and adsorbent dose on adsorption of metal ions were investigated using batch adsorption experiments. The optimum pH for Cu(II), Zn(II) and Co(II) adsorption was observed at 5.0, 9.0 and 8.0, respectively. The mechanism for the removal of metal ions by HA-Am-PAA-B was based on ion exchange and complexation reactions. Metal removal by HA-Am-PAA-B followed a pseudo-second-order kinetics and equilibrium was achieved within 120 min. The suitability of Langmuir, Freundlich and Dubinin-Radushkevich adsorption models to the equilibrium data was investigated. The adsorption was well described by the Langmuir isotherm model. The maximum monolayer adsorption capacity was 106.2, 96.1 and 52.9 mg g^?1 for Cu(II), Zn(II) and Co(II) ions, respectively, at 30 °C. The efficiency of HA-Am-PAA-B in removing metal ions from different industry wastewaters was tested. Adsorbed metal ions were desorbed effectively (97.7 for Cu(II), 98.5 for Zn(II) and 99.2% for Co(II)) by 0.1 M HCl. The reusability of the HA-Am-PAA-B for several cycles was also demonstrated.     

NO reduction over nanostructure M-Cu/ZSM-5 (M: Cr,Mn, Co and Fe) bimetallic catalysts and optimization of catalyst preparation by RSM

The selective catalytic reduction (SCR) of NO with NH₃ in the presence of oxygen over a series of H-ZSM-5 supported transition metal oxides (Co, Mn, Cr, Cu and Fe) was investigated. Among them, Cu/ZSM-5 nanocatalyst was found to be the most promising catalyst based on activity. The modification of Cu/ZSM-5 by adding different transition metals (Co, Mn, Cr and Fe) to improve the efficiency of NO conversion was studied. The results indicated that the Fe–Cu/ZSM-5 bimetallic nanocatalyst was the highest active catalyst for NO conversion (67% at 250 °C and 93% at 300 °C). Response surface methodology (RSM) involving central composite design (CCD) was employed to evaluate and optimize Fe–Cu/ZSM-5 preparation parameters (Fe loading, calcinations temperature, and impregnation temperature) in SCR of NO at 250 °C. The optimum condition for maximum NO conversion was estimated at 4.2 wt.% Fe loading, calcinations temperature of 577 °C and impregnation temperature of 43.5 °C. Under these condition, experimental NO conversion efficiency was 78.8%, which was close with the predicted value (79.4%).     

Spectral and electrochemical investigation of octanitro substituted metal phthalocyanines

A simple and convenient method has been developed for the synthesis of 1,3,8,10,15,17,22,24-octanitrophthalocyanine derivatives MPcON's [M = Fe(III)Cl, Zn(II), Co(II), Cu(II) and Ni(II)]. The compounds were prepared from 3,5-dinitrophthalic acid in the presence of ammonium chloride, urea and catalytic quantity of ammonium molybdate in nitrobenzene solvent; the complexes were characterized by elemental analysis, electronic and IR spectra and powder XRD. The electrochemical redox properties of the complexes were studied using glassy carbon and platinum electrodes in non-aqueous media employing tetra butyl ammonium perchlorate as supporting electrolyte.     

Determination of rare earth elements in Niger Delta crude oils by inductively coupled plasma-mass spectrometry

A profile for rare earth elements (REE) of crude oils from the offshore – shallow water and onshore fields in the Niger Delta, analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) is reported. The oil samples were prepared for ICP-MS measurement by acid digestion into colourless aqueous solution. The analysis method was validated using standard reference materials SLRS-4 and NIST-1640. Results showed percentage recovery values that ranged from 81.8% to 115.4% for Co, Cu, Fe, Mn, Ni, Sb and U and from 98.8% to 104.7% for Co, Cu, Fe, Mn, Ni and Sb. The magnitude of deviation recorded in SLRS-4 for Co and Fe suggests that it may not be a suitable standard for these elements using the ICP-MS method outlined in this study. The concentrations of the detected REE; La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb ranged from 0.01 to 1.58 ppb with an average of 0.98 ppb (%RSD < 5) for the oil samples analyzed. Light REEs (LREE) were identified in all the oil samples while heavy rare earth elements (HREE) were identified in offshore oil samples only. LREE patterns constructed from chondrite-normalized values for the oils show some similarities among the oils, which suggest common origin of the oils and that the REE got into the oils from similar source. While those with different chondrite-normalized REE patterns suggest different source input of the REE. This indicates that REE will be a useful tool in oil–oil correlation. Statistical evaluation of these oils by cluster analysis using the REE as variables clearly discriminated according to their geographic sources. Biodegradation has pronounced effect on the concentration of REE in oils. Therefore, REE contents of oils will be useful in oil classification. ICP-MS proved to be a versatile method for the determination of rare earth elements in Niger Delta oils.     

A novel agricultural waste based adsorbent for the removal of Pb(II) from aqueous solution: Kinetics,equilibrium and thermodynamic studies

Fig sawdust was used as a precursor for the production of activated carbon by chemical activation with H₃PO₄. The developed Fig sawdust activated carbon (FSAC) was used as a biosorbent for the removal of Pb(II) from aqueous solution. Highest adsorption of Pb(II) (95.8%) was found at pH 4. Equilibrium data fitted very well with the Langmuir isotherm model. Maximum adsorption capacity was determined 80.645 mg g⁻¹ at pH 4. Kinetic studies demonstrated that the adsorption followed a pseudo second order kinetics model. The negative value of ΔG° confirmed the feasibility and spontaneity of FSAC for Pb(II) adsorption.     

Properties and rapid consolidation of nanostructured TiC-based hard materials with various binders by a high-frequency induction heated sintering

The densification of hard TiC–10 vol.% binder (Co, Ni, Fe) materials was accomplished within 2 min using a high-frequency induction heated sintering (HFIHS) method. The advantage of this process is not only rapid densification to almost the theoretical density but also the prevention of grain growth of the nano-structured materials. Highly dense TiC–binder (Co, Ni, Fe) composites with a relative density of up to 99.9% were obtained within 2 min by HFIHS under 80 MPa. The average grain size of TiC in the TiC–10 vol.% Ni composite was approximately 44 nm. The hardness and fracture toughness of the dense TiC–10 vol.% binder (Co, Ni, Fe) composite produced by HFIHS were also investigated.     

High surface area-activated carbon from Glycyrrhiza glabra residue by ZnCl2 activation for removal of Pb(II) and Ni(II) from water samples

A high-surface-area activated carbon was prepared by chemical activation of Glycyrrhiza glabra residue with ZnCl₂ as active agent. Then, the adsorption behavior of Pb(II) and Ni(II) ion onto produced activated carbon has been studied. The experimental data were fitted to various isotherm models. According to Langmuir model, the maximum adsorption capacity of Pb(II) and Ni(II) ions were found to be 200 and 166.7 mg g⁻¹, respectively, at room temperature. Kinetic studies showed the adsorption process followed pseudo second-order rate model. High values of intra-particle rate constants calculated shows the high tendency of activated carbon for removal of Pb(II) and Ni(II) ions.     

Effect of oxide additives on the sintering behavior and electrical properties of strontium- and magnesium-doped lanthanum gallate

The effects of 14 different metal-oxide additives (metal = Mn, Fe, Co, Ni, Cu, B, Li, V, Zn, Si, Ca, Al, Bi, and Ba) on the sintering, phase purity, and electrical properties of strontium- and magnesium-doped lanthanum gallate (LSGM) are studied. The density, phase purity, and electrical conductivity depend closely on the sintering aids and sintering temperatures. The addition of V, Zn, Si, Co, and Fe improves the densification, phase purity, and electrical conductivity, with V showing the most promising effect on the low-temperature sintering of the phase-pure LSGM specimen with high conductivity.     

Interface structure and mechanical properties of the brazed joint of TiC cermet and steel

A commercially available Ag–Cu braze alloy foil with Zn was used to join TiC cermet and steel. According to the experimental observations, the interface structure is (Cu, Ni)/Ag (s.s.) + Cu (s.s.)/(Cu, Ni)/(Cu, Ni) + (Fe, Ni) from TiC cermet to steel side. With increased brazing temperature or time, the amounts of (Cu, Ni) near the base metals/Ag–31Cu–23Zn interface and (Cu, Ni) + (Fe, Ni) near the Ag–31Cu–23Zn/steel interface increase, while the amount of Ag (s.s.) + Cu (s.s.) in the middle of the braze alloy decreases. The whole joining process consists of diffusion and solution among atoms of the braze alloy foil and base metals. The maximum shear strength is 120.7 MPa for the joint brazed at 850 °C for 10 min.     

Separation of Co(II) and Mn(II) from sulphate media via a HFSLM: Reaction flux model and experimental verification

Separation of Co(II) and Mn(II) from sulphate media through triple HFSLM in series using D2EHPA was explored. Mn(II) was extracted preferentially over Co(II) at the pH value of 5, 100 ppm of Co(II) and Mn(II), 5% (v/v) of D2EHPA, 0.2 M HCl. The highest extraction percentage of Mn(II) was 98.14%, and Co(II) remained at 94.05% in the raffinate stream. The reaction order (n) and the reaction rate constant (k_f) were found to be 1.00 and 0.0180 min⁻¹, respectively. Furthermore, the reaction flux model proved to be in good agreement with the experimental data at an average deviation of 2.24%.     

Helical poly(N-propargylamide)s with functional catechol groups: Synthesis and adsorption of metal ions in aqueous solution

A novel type of helical N-propargylamide (PA) copolymer was synthesized by catalytic polymerization of monomer 1 (M1), which provided pendent functional catechol groups, and monomer 2 (M2), which endowed the expected copolymer backbones with helical structures. With [(nbd)Rh⁺B^?(C₆H₅)₄ (nbd = 2,5-norbornadiene)] as catalyst, PA copolymers could be obtained with moderate molecular weights (3800–14,000) in high yields (?96%). The functional catechol groups enhanced the hydrophilicity of the hydrophobic mono-substituted polyacetylenes and aided the helical PA copolymers in showing a considerable adsorbance toward metal ions [Fe(III), Cr(III), Ni(II), Zn(II), Cu(II) and Cu(I)] in aqueous solution. The prepared copolymer in which M1/M2 was 0.1/0.9 [mol/mol, poly(1_0.1-co-2_0.9)] showed the highest adsorption capacity among the examined helical copolymers. In particular, for Fe(III), the maximum adsorption capacity was 186 mg g^?1.     

Nanoreactor-confined synthesis and separation of yellow-luminescent graphene quantum dots with a recyclable SBA-15 template and their application for Fe(III) sensing

Graphene quantum dots (GQDs) have inspired growing research efforts. Although continuous progresses have been achieved in the syntheses of diverse GQDs, it is still a challenge in size-controllable and high-yield preparation of well dispersed GQDs via simple routes. Herein, we present a top-down synthesis of GQDs by using a SBA-15 template as a nanoreactor via a HNO₃ vapor cutting strategy. With the recyclable ordered mesoporous SBA-15 template and a silica grid, a high-yield (48%) preparation as well as a facile separation of yellow-luminescent GQDs have been achieved. The obtained GQDs containing abundant oxygen-containing groups (ca. 30% for oxygen content) showed a narrow size distribution (2.5–5.2 nm), good water solubility, good photostability and high selectivity for Fe(III) sensing in tap water with satisfying recovery. Further experiments indicated that Cu(II), Co(II), Mn(II), Ni(II) could also quench the fluorescence of the as-prepared GQD after its surface states being adjusted, which might presage more possible applications of this material.     

Copper removal from acidic wastewaters using 2-hydroxy-5-nonylbenzaldehyde oxime as ionophore in pseudo-emulsion membrane with strip dispersion (PEMSD) technology

Results on Cu(II) extraction from acidic media through pseudo-emulsion based membrane strip dispersion (PEMSD) containing Acorga M5640/Iberfluid as organic phase in the form of a pseudo-emulsion with H₂SO₄ were presented. The transport of Cu(II) is investigated as a function of several experimental variables: hydrodynamic conditions, feed solution pH, Acorga M5640 (salicylaldoxime derivative) concentration in the organic solution, and initial metal concentration in feed phase. In this membrane technology, pseudo-emulsion is an emulsion that is formed temporarily between organic and stripping solutions, both solutions are completely separated when mixing is stopped. The value of the overall mass transfer coefficient obtained under standard experimental conditions was 5.5 × 10^?3 cm/s, being the recovery of copper in the stripping solution around 80–85%. The influence of the membrane support, the selectivity of Acorga M5640/Inerfluid based PEMSD towards different metals (Fe(III), Ni(II), Co(II), Zn(II), Cr(III)) an the performance of the system Cu/Acorga M5640/Ibefluid against other commercially available salicylaldoximes (LIX 860, Acorga PT5050) were also examined.     

Heavy metals adsorption on some iminodiacetate chelating resins as a function of the adsorption parameters

The adsorption properties of some novel chelating resins (CRs) bearing iminodiacetate groups for removal of heavy metal ions like: Cu(II), Co(II) and Ni(II) from aqueous solutions comparative with the commercial resin Amberlite IRC-748 have been studied in this work by a batch equilibrium technique. Quantitative analysis for adsorption was conducted using UV–vis spectroscopy to investigate the kinetics, adsorption isotherm and thermodynamics of the removal process considering equilibration time, pH, metal ion concentration and temperature as controlling parameters. The metal adsorption capacities, at pH 5, were in the order Cu(II) > Ni(II) > Co(II), for both the CR with 10 wt.% DVB (CR-10) and the commercial resin Amberlite IRC-748. The adsorption capacities on CR-10 were higher for Ni(II) and Co(II) ions, but lower for Cu(II) ions compared with Amberlite IRC-748. Both Freundlich and Langmuir isotherms well fitted on the adsorption results of Cu(II), Ni(II) and Co(II) ions on all iminodiacetate resins.     

NO SCR with propane and propene on Co-based alumina catalysts prepared by co-precipitation

Homogeneous dispersions and small size of deposited high-content cobalt on alumina were achieved by the co-precipitation method and were well maintained on the cobalt-based binary alumina catalysts with Zn, Ag, Fe, Cu or Ni as modifiers. The component and concentration of deposited cobalt species were characterized by UV–vis, EDX and XPS spectra and found to be greatly related to the Co loading, calcination temperatures and the type of additive metals. The optimal Co loading of 8 wt% and calcination temperatures of 800 °C were demonstrated. With respect to the single cobalt-based alumina catalyst, the surface concentration of Co²⁺ on the binary catalysts with addition of Fe, Cu, Ag or Ni was all reduced and accompanying with part conversion of Co²⁺ to Co₃O₄ on the Fe and Ni-modified catalysts. A slight enhanced surface Co²⁺ concentration was only achieved on the Zn-promoted catalyst. It was also demonstrated that for the case of Cu and Fe the additive metals themselves participated in the activation of propene. The octahedral and tetrahedral Co²⁺ ions were suggested as the common active sites. A maximum deNOx activity of 96% was observed on the 8Co4ZnA800 catalyst at the reaction temperatures of 450 °C, and the catalytic performance on the cobalt-based binary alumina catalysts can be described as fellows: CoZn > CoAg, CoNi > Co Cu > CoFe. Based on the in situ DRIFT spectra, different reaction intermediates R–ONO and –NCO besides –NO₂ were formed on the 8Co4ZnA800 and 8Co4FeA800 samples, respectively, demonstrating their dissimilar reaction mechanisms.     

Hydrogenation of carbon monoxide to methane over mesoporous nickel-M-alumina (M = Fe,Ni, Co,Ce, and La) xerogel catalysts

Mesoporous nickel(30 wt%)-M(10 wt%)-alumina xerogel (30Ni10MAX) catalysts with different second metal (M = Fe, Ni, Co, Ce, and La) were prepared by a single-step sol–gel method for use in the methane production from carbon monoxide and hydrogen. In the methanation reaction, yield for CH₄ decreased in the order of 30Ni10FeAX > 30Ni10NiAX > 30Ni10CoAX > 30Ni10CeAX > 30Ni10LaAX. Experimental results revealed that CO dissociation energy of the catalyst and H₂ adsorption ability of the catalyst played a key role in determining the catalytic performance of 30Ni10MAX catalyst in the methanation reaction. Optimal CO dissociation energy of the catalyst and large H₂ adsorption ability of the catalyst were favorable for methane production. Among the catalysts tested, 30Ni10FeAX catalyst with the most optimal CO dissociation energy and the largest H₂ adsorption ability exhibited the best catalytic performance in terms of conversion of CO and yield for CH₄ in the methanation reaction. The enhanced catalytic performance of 30Ni10FeAX was also due to a formation of nickel–iron alloy and a facile reduction.     

Onion-like carbon-encapsulated Co,Ni, and Fe magnetic nanoparticles with low cytotoxicity synthesized by a pulsed plasma in a liquid

We synthesized onion-like carbon-encapsulated Co, Ni, and Fe (Co–C, Ni–C, and Fe–C) magnetic nanoparticles with low cytotoxicity using pulsed plasma in a liquid. The pulsed plasma is induced by a low-voltage spark discharge submerged in a dielectric liquid. The face-centered cubic Co and Ni, and body-centered cubic Fe core nanoparticles showed good crystalline structures with an average size between 20 and 30 nm were encapsulated in onion-like carbon coatings with a thickness of 2–10 nm. Vibrating-sample magnetometer measurements revealed the ferromagnetic properties of as-synthesized samples at room temperature (Co–C = 360 Oe, Fe–C = 380 Oe, and Ni–C = 211 Oe). Raman-spectroscopy analysis found onion-like carbon shells composed of well-organized graphitic structures. Thermal gravimetric analysis showed a high stability of the as-synthesized samples under thermal treatment and oxidation. Cytotoxicity measurements showed higher cancer cell viability than samples synthesized by different methods.