Selective Removal Of Zinc Research Articles

Selective removal of zinc from single and industrial aqueous solutions using ecologically sustainable ceramic adsorptive aggregates

Selective removal of zinc from single and industrial aqueous solutions using ecologically sustainable ceramic adsorptive aggregates

Selective removal of zinc and lead from electric arc furnace dust by chlorination–evaporation reactions

Re-melting of scrap in an electric arc furnace (EAF) results in the accumulation of filter dust from off-gas treatment that predominantly consists of iron and zinc oxides. Filter dust is classified as hazardous waste due to its high contents of potentially toxic or ecotoxic elements such as Pb, Cr, Cd, and As. A promising processing route for this waste is selective chlorination, in which the non-ferrous metal oxides are chlorinated and selectively evaporated in form of their respective chlorides from the remaining solids via the process gas flow. Here, we investigate stepwise thermochemical treatment of EAF dust with either waste iron(II) chloride solution or hydrochloric acid at 650, 800, and 1100 °C. The Zn and Pb contents of the thermochemically processed EAF dust could be lowered from 29.9% and 1.63% to 0.09% and 0.004%, respectively. Stepwise heating allowed high separation between zinc chloride at the 650 °C step and sodium-, potassium-, and lead-containing chlorides at higher temperatures. Furthermore, the lab-scale results were transferred to the use of an experimental rotary kiln highlighting the possibilities of upscaling the presented process. Selective chlorination of EAF dust with liquid chlorine donors is, therefore, suggested as a potential recycling method for Zn-enriched steelworks dusts.

Selective Removal of Zinc from BOF Sludge by Leaching with Mixtures of Ammonia and Ammonium Carbonate

The zinc content of basic oxygen furnace (BOF) sludges is too high for direct recycling into the blast furnace via the sinter plant, as excessive zinc concentrations are detrimental for the refractory lining of the blast furnace. However, by partial and selective removal of zinc from the BOF sludge, the residual sludge can be used as a secondary iron resource in the blast furnace. In this paper, BOF sludge was leached with aqueous ammonia, aqueous solutions of ammonium salts (chloride, carbonate, and sulfate), and aqueous mixtures of ammonia and ammonium salt. The mixtures of ammonia and ammonium salt could leach more zinc with respect to either the aqueous ammonia or the aqueous ammonium salt solution. The ammonia–ammonium carbonate (AAC) mixture was selected as the most suitable lixiviant due to the high zinc leaching efficiency in combination with a high selectivity towards iron; furthermore, this combination does not introduce unwanted chloride or sulfate impurities in the residue. The leaching process was optimized in terms of the liquid-to-solid ratio, total ammonia concentration, ammonium:ammonia molar ratio, temperature, and leaching time. The co-dissolved iron was precipitated as a hydroxide after oxidation of ferrous to ferric ions by an air stream, without co-precipitation of zinc, while the dissolved zinc could be easily recovered as zinc sulfide by precipitation with ammonium sulfide. The (almost) closed-loop process was successfully up-scaled from 10 mL to 1 L scale.Graphical

Remote control of the reversible assembly/disassembly of supramolecular aggregates

ABSTRACTA multi-component system is presented in which the actuation of a copper-loaded nanoswitch by zinc(II) ions as an external trigger and the thereby prompted release of copper(I) ions allows self-assembly of 11 parts resulting in the formation of a three-component supramolecular prism. Using the same protocol, a three-component rectangle was made from eight parts. Disassembly of the aggregates was accomplished by selective removal of zinc(II) ions using hexacyclen. In sum, the reversible assembly and disassembly of supramolecular aggregates was controlled in a multi-component mixture through intermolecular communication using a second messenger.

Selective removal of zinc using tri-ethanolamine-based supported liquid membrane

This work is a comprehensive study on the selective removal of Zn (II) from aqueous solution using a flat-sheet polypropylene-supported liquid membrane system. Tri-ethanolamine (TEA) dissolved in cyclohexanone was used as a carrier for extraction of zinc ions through supported liquid membrane. Different parameters affecting the zinc ion transport were studied. The experiments were performed at various operating conditions such as metal and acid concentration in feed phase, strip phase concentration, and carrier concentration, to find the best set of parameters that would yield the maximum extraction. The extraction time, flux value, the stoichiometry of the complex formed, and membrane stability was also investigated. The experiments were performed in co-transport mode. The optimized conditions obtained for zinc ion transport are as follows: 2.30 × 10−4 mol/dm3 of Zn2+ ions and 1M of HCl in feed solution, 50% TEA in cyclohexanone in membrane phase, and 0.7M of NaOH in stripping phase. Under these optimum conditions, the membrane is stable for about 10 consecutive experiments. The extraction efficiency was found to be 87% in 120 min.

Experimental Studies on the Effects of Tin on the Densification of W-Brass Composites

The effects of 1% tin (Sn) addition on the densification of pre-alloyed and pre-mixed W-brass composites were carried out. The green compacts were produced with the pressure of 350MPa and sintered at the temperature of 800°C, 920°C and 1000°C. The Sn addition is aimed at inhibiting the dezincification (selective removal of zinc from an alloy) of the brass component by the elimination of pores and enhances densification. The hardness of the composites increased with increase in temperature, the densification was low at both temperatures while the electrical conductivity remains constant as a result of constant composition in both pre-alloyed and pre-mixed composites. The microstructures revealed pores, which might be as a result of zinc evaporation.

Temperature Enhancement of Zinc and Iron Separation from Chromium(III) Passivation Baths by Emulsion Pertraction Technology

This work reports the influence of the temperature on the selective removal of zinc and iron from a chromium(III) passivation bath by emulsion pertraction technology using Cyanex 272 as extractant and hollow fiber membrane contactors. The results indicate that the kinetics of the separation was largely influenced by the temperature in the range 10–40 °C. The viscosity of the organic liquid phase was measured at different temperatures and extractant concentrations, and the results were fitted to the Riedel and Grunberg and Nissan correlations. The improvement observed from 20 to 40 °C was explained by the increase in the diffusion coefficient of the zinc and iron organometallic complexes through the liquid membrane. However, the remarkably slower zinc and iron separation rates observed at 10 °C in comparison with those at 20–40 °C were attributed to a shift in the driving force due to an endothermic change of the interfacial extraction reaction. The equilibrium parameters at 10 and 20–40 °C were estimated by fitting the experimental kinetic results to the proposed mathematical model. Thus, this work addresses the thermal character of equilibrium and its relevant influence on the separation kinetics of reactive membrane systems.

Selective removal of zinc from basic oxygen furnace sludges

The present research investigated the removal of zinc from BOF (basic oxygen furnace) sludges in an attempt to reuse the iron content of the sludge in the production of sinter. The study consisted of two main steps: (i) the characterization of fine and coarse fractions of BOF sludges and (ii) the hybrid treatment of sludge to selectively remove zinc from iron. The characterization study showed that the Fe/Zn ratio is 132.6 in the coarse fraction and 11.6 in the fine fraction; the amount of zinc proved to be 8.5 times higher in the later fraction, while the total content of iron ranged between 50 and 60% in both fractions. Zinc could also be identified in the sludge as zincite (ZnO) and franklinite (ZnO.Fe 2O 3), whose last phase is quite stable and insoluble in NaOH solutions. Other characteristics, including the granulometry, morphology, and toxicity of both fractions of the sludge, were also determined. To improve the zinc removal efficiency, franklinite must be decomposed by a thermal treatment. For this reason, a hybrid route was investigated using the fine fraction of the sludge. The effect of various materials and reagents was evaluated concerning the decomposition of franklinite, in which NaOH was found to be the most effective. Operating variables, such as temperature, time, and NaOH/sludge ratio were studied. The treatment was found to be quite efficient in the selective removal of zinc from the sludge (zinc removal higher than 90% was obtained with practically no iron extraction), thus improving the Fe/Zn ratio in the fine fraction to approximately 200.

Selective removal of zinc(II) from spent pickling solutions in the presence of iron ions with phosphonium ionic liquid Cyphos IL 101

Trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) – a phosphonium ionic liquid – was used as a novel reagent mixed with toluene to extract selectively zinc(II) from chloride media in the presence of iron(II). The extraction of individual metal ions with Cyphos IL 101 increases in the following order: iron(II)<zinc(II)<iron(III). Zinc(II) extraction is preferred over iron(II) when both are present in the feed. Maximum loading capacity of 50vol.% Cyphos IL 101 amounts to 45, 40 and almost 30gdm−3 of Fe(III), Zn(II) and Fe(II), respectively. Selective separation of Zn(II) from mixtures of Zn(II) and Fe(II) model spent pickling solutions is investigated in multistage extraction-stripping. Zn(II) extraction from the feed containing only 5gdm−3 exceeds 85% after the first extraction stage, reaching almost 100% after three stages. Meanwhile, iron(II) extraction also increases (after three stages it amounts to 40%). Extraction in the presence of 120gdm−3 Zn(II) and 35gdm−3 Fe(II) needs four extraction stages to deplete Zn(II) in the feed. At the same time Fe(II) extraction is low and equals less than 20% after four stages. Stripping of the predominant metal ions takes place prior to the deficient ones. Zinc(II) can be selectively transferred from the feed containing high Zn(II) concentration and four times lower concentration of Fe(II) to the stripping phase. The most important from the practical point of view is the ability of Cyphos IL 101/toluene mixture to separate selectively zinc(II) from iron(II) when both are in concentrated zinc(II) feeds.

Selective Removal of Zinc from an Electroless Nickel Plating Bath by Solvent Impregnated Resin Using 2-Ethylhexylphosphonic Acid Mono-2-Ethylhexyl Ester as the Extractant

A solvent impregnated resin (SIR) containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) as the extractant was tested for zinc removal from aqueous solutions, including the real electroless nickel plating bath employed for an aluminum alloy substrate, in order to extend the bath life. The SIR effectively and selectively adsorbed zinc over nickel without any pH adjustment from the plating bath, although the adsorption was significantly suppressed by the complexation of the zinc ion by the hydrogen phosphite and dihydrogen phosphite ions. The Langmuir adsorption isotherm was used to correlate the zinc adsorption data and the SIR containing 30 wt% EHPNA, exhibited the maximum adsorption capacity of 0.51 mmol/g-dry-SIR corresponding to a zinc- to-EHPNA molar ratio of 1:2. Repeated column adsorption and elution tests for 15 cycles showed that the adsorption ability of the SIR gradually decreased suggesting that the durability of the resin should be improved.

Synthesis of Zn(II) Ion-Imprinted Polymeric Adsorbent for Selective Removal of Zinc from Aqueous Solutions

In this study, Zn(II)-imprinted polymer microbeads were synthesized for selective removal of Zn(II) from aqueous solutions. The microbeads were prepared using methacrylic acid and 1,4-vinyl pyrrolidone as functional monomers, zinc(II)acetate as zinc salt, ethylene glycol dimethacyrlate as a cross-linking agent, azo bisisobutyronitrile as an initiator and hydroxyethyl cellulose as surfactant. The non-imprinted polymer was also prepared for comparison, except without use of the Zn(II) salt. To determine the selectivity of Zn(II)-IIP beads, competitive adsorption experiments were investigated. According to the adsorption capacity values of the microbeads, Zn(II)-IIP beads show good selectivity for the target ion.

Selective extraction of zinc(II) over iron(II) from spent hydrochloric acid pickling effluents by liquid–liquid extraction

The selective removal of zinc(II) over iron(II) by liquid–liquid extraction from spent hydrochloric acid pickling effluents produced by the zinc hot-dip galvanizing industry was studied at room temperature. Two distinct effluents were investigated: effluent 1 containing 70.2 g/L of Zn, 92.2 g/L of Fe and pH 0.6, and effluent 2 containing 33.9 g/L of Zn, 203.9 g/L of Fe and 2 M HCl. The following extractants were compared: TBP (tri- n-butyl phosphate), Cyanex 272 [bis(2,4,4-trimethylpentyl)phosphinic acid], Cyanex 301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid] and Cyanex 302 [bis(2,4,4-trimethylpentyl) monothiophosphinic acid]. The best separation results were obtained for extractants TBP and Cyanex 301. Around 92.5% of zinc and 11.2% of iron were extracted from effluent 1 in one single contact using 100% (v/v) of TBP. With Cyanex 301, around 80–95% of zinc and less than 10% of iron were extracted from effluent 2 at pH 0.3–1.0. For Cyanex 272, the highest extraction yield for zinc (70% of zinc with 20% of iron extraction) was found at pH 2.4. Cyanex 302 presented low metal extraction levels (below 10%) and slow phase disengagement characteristics. Reactions for the extraction of zinc with TBP and Cyanex 301 from hydrochloric acid solution were proposed.