Zinc Efficiency Research Articles

Electrokinetic remediation of contaminated soil with waste-lubricant oils and zinc

The feasibility of electrokinetic technology on the remediation of mixed-waste-contaminated railroad soil, contaminated by lubricant oil and zinc, was investigated. To enhance the removal efficiency, catholyte purging with 0.1 M HNO 3 and a supply of non-ionic surfactant, secondary alcohol ethoxylate, was applied to the anode to remove Zn and to solubilize the lubricant oil. The catholyte purging maintained the soil pH as acidic and enhanced desorption of zinc from the soil, where the zeta potential of the acidic soil became positive. Thereafter, the direction of electro-osmotic flow was changed from the cathode to anode and the flow rate was reduced. The lesser in magnitude reverse electro-osmotic flow inhibited the migration of zinc and the lubricant oil was removed by the electro-osmotic flow. The removal of zinc and lubricant oil was enhanced with an increase in voltage gradient; however, a higher voltage gradient resulted in higher energy expenditure. After electrokinetic operation over 17 days, the removal efficiency of zinc was 22.1–24.3%, and that of lubricant oil was 45.1–55.0%. Although the removal of lubricant oil was quite high, the residual concentration did not meet Korean regulation levels.

Zinc Efficiency is Correlated with Root Morphology, Ultrastructure, and Antioxidative Enzymes in Rice

ABSTRACT To elucidate physiological mechanisms of zinc (Zn) efficiency in rice (Oryza sativa L.), comparative studies on root morphology, ultrastructure, and oxidative enzyme activities were investigated using Zn-efficient rice genotype (‘IR8192’) and Zn-inefficient rice genotype (‘Erjiufeng’). The results showed that moderate Zn-deficient conditions increased root length, root surface, and root tips in both genotypes, but a greater extent occurred in ‘IR8192’. Under moderate Zn deficient conditions, many swollen mitochondria were observed in the root tip cells of ‘Erjiufeng’, whereas most root cells in ‘IR8192’ remained intact. Disturbances in the ultrastructure of these organelles were accompanied with elevated oxidative stress in both genotypes and the increases were less in ‘IR8192’ than in ‘Erjiufeng’. This may result from the differences that existed in the activities of antioxidative enzymes between these two genotypes. These results suggest that Zn efficiency in ‘IR8192’ is closely associated with its high root tolerance to Zn-deficiency by maintaining a relatively higher efficient antioxidative system and intact root tip cell and functions.

Leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system

The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NY4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69 μm, holding at 80 °C for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2:1, and the ratio (g/mL) of solid to liquid being 1:10.

Application of Vacuum Metallurgy to Separate Pure Metal from Mixed Metallic Particles of Crushed Waste Printed Circuit Board Scraps

The principle of separating pure metal from mixed metallic particles (MMPs) byvacuum metallurgy is that the vapor pressures of various metals at the same temperature are different As a result, the metal with high vapor pressure and low boiling point can be separated from the mixed metals through distillation or sublimation, and then it can be recycled through condensation under a certain condition. The vacuum metallurgy separation (VMS) of MMPs of crushed waste printed circuit boards (WPCBs) has been studied in this paper. Theoretical analyses show that the MMPs (copper, zinc, bismuth, lead, and indium, for example) can be separated by vacuum metallurgy. The copper particles (0.15-0.20 mm) and zinc particles (<0.30 mm) were chosen to simulate the MMPs of crushed WPCBs. Experimental results show that the separated efficiency of zinc in the copper-rich particles achieves 96.19 wt % when the vacuum pressure is 0.01-0.10 Pa, the heating temperature is 1123 K, and the heating time is 105 min. Under this operation condition, the separated efficiency of zinc in the copper-rich particles from crushed WPCBs achieves 97.00 wt % and the copper purity increases from 90.68 to 99.84 wt %.

Quantitative trait loci analysis of zinc efficiency and grain zinc concentration in wheat using whole genome average interval mapping

Zinc (Zn) deficiency is a widespread problem which reduces yield and grain nutritive value in many cereal growing regions of the world. While there is considerable genetic variation in tolerance to Zn deficiency (also known as Zn efficiency), phenotypic selection is difficult and would benefit from the development of molecular markers. A doubled haploid population derived from a cross between the Zn inefficient genotype RAC875-2 and the moderately efficient genotype Cascades was screened in three experiments to identify QTL linked to growth under low Zn and with the concentrations of Zn and iron (Fe) in leaf tissue and in the grain. Two experiments were conducted under controlled conditions while the third examined the response to Zn in the field. QTL were identified using an improved method of analysis, whole genome average interval mapping. Shoot biomass and shoot Zn and Fe concentrations showed significant negative correlations, while there were significant genetic correlations between grain Zn and Fe concentrations. Shoot biomass, tissue and grain Zn concentrations were controlled by a number of genes, many with a minor effect. Depending on the traits and the site, the QTL accounted for 12–81% of the genetic variation. Most of the QTL linked to seedling growth under Zn deficiency and to Zn and Fe concentrations were associated with height genes with greater seedling biomass associated with lower Zn and Fe concentrations. Four QTL for grain Zn concentration and a single QTL for grain Fe concentration were also identified. A cluster of adjacent QTL related to the severity of symptoms of Zn deficiency, shoot Zn concentration and kernel weight was found on chromosome 4A and a cluster of QTL associated with shoot and grain Fe concentrations and kernel weight was found on chromosome 3D. These two regions appear promising areas for further work to develop markers for enhanced growth under low Zn and for Zn and Fe uptake. Although there was no significant difference between the parents, the grain Zn concentration ranged from 29 to 43 mg kg−1 within the population and four QTL associated with grain Zn concentration were identified. These were located on chromosomes 3D, 4B, 6B and 7A and they described 92% of the genetic variation. Each QTL had a relatively small effect on grain Zn concentration but combining the four high Zn alleles increased the grain Zn by 23%. While this illustrates the potential for pyramiding genes to improve grain Zn, breeding for increased grain Zn concentration requires identification of individual QTL with large effects, which in turn requires construction and testing of new mapping populations in the future.

Adsorption of zinc and toluene by alginate complex impregnated with zeolite and activated carbon

In this study, a novel alginate complex was developed for removal of mixed contaminants containing both organic and inorganic compounds. The alginate complex was generated by impregnating synthetic zeolite and powdered activated carbon (PAC) into alginate gel bead. The adsorption of zinc and toluene as target contaminants onto the alginate complex was investigated by performing both equilibrium and kinetic batch tests. Equilibrium tests showed that adsorption of two contaminants followed Langmuir isotherm and that the alginate complex was capable of removing zinc (maximum binding energy β = 4.3 g/kg) and toluene ( β = 13.0 g/kg) best compared to other adsorbents such as granular activated carbon (GAC), zeolite, and alginate impregnated with PAC (AG–AC bead). These values were higher than those of any other adsorbents for each contaminant. It was further revealed from kinetic tests that removal efficiency of zinc and toluene was 54% and 86% for the initial solution concentrations of 250 mg/L, respectively. This indicates that the alginate complex developed in this study can be used as promising adsorbents for simultaneous removal of organic and inorganic compounds from industrial wastewater or groundwater containing mixed contaminants.

Domesticated emmer wheat [T. turgidum L. subsp. dicoccon (Schrank) Thell.] as a source for improvement of zinc efficiency in durum wheat

Modern durum wheat (AABB) is more sensitive to zinc (Zn) deficiency than bread wheat (AABBDD). One strategy to increase productivity and expansion of durum wheat industry in Zn-deficient soils is to improve its ability to grow and yield in such soils. This ability is termed Zn efficiency. In a growth room experiment using soil culture, we assessed the potential of Triticum turgidum L. subsp. dicoccon (Shrank) Thell. (domesticated emmer wheat, AABB) as a genetic resource for further improvement of Zn efficiency in modern durum wheat. Twenty four accessions of domesticated emmer wheat, four durum landraces/cultivars, and two bread wheat cultivars/ advanced breeders lines of known Zn efficiency were tested under Zn deficiency and Zn sufficiency. Significant variation was observed among genotypes in Zn deficiency symptoms, dry matter production, shoot Zn concentration, shoot Zn content and Zn utilisation efficiency (physiological efficiency). We identified domesticated emmer wheat accessions with greater Zn efficiency than modern durum wheat and even bread wheat genotypes. These accessions could be used in breeding programs to improve Zn efficiency of durum wheat. The results suggest that Zn efficiency of durum or bread wheat is likely to be determined collectively by its progenitors.

Genomic analysis and expression pattern of OsZIP1, OsZIP3, and OsZIP4 in two rice (Oryza sativa L.) genotypes with different zinc efficiency

The ZRT-and IRT-like proteins (ZIP) comprise a large family of transition metal transporters in plants that have diverse functions to transport zinc, iron, copper, etc. Here, we provided a complete overview of this gene family in rice (Oryza sativa L.). Based on the hidden Markov model and BLAST analysis, a total of 17 ZIP-coding genes were identified and further studied by semi-quantitative RT-PCR analysis. Sequence analysis revealed 17 putative genes distributed randomly on eight chromosomes. Although most of the predicted proteins had typical characteristics of the ZIP protein family, the extent of their sequence similarity varied considerably. The expression patterns of OsZIP1, OsZIP3, and OsZIP4, which encode Zn2+ transporters in rice, were studied in the Zn-efficient and Zn-inefficient rice genotypes (IR8192 and Erjiufeng) by semi-quantitative RT-PCR analysis of roots, shoots, and panicle from the plants grown under Zn deficiency and normal conditions. OsZIP1 was expressed only in the roots and very weakly if at all in the panicles, while the other two genes were expressed in all parts of plants under study. The Zn-deficient conditions up-regulated the expression of OsZIP1, OsZIP3, and OsZIP4 in the roots and that of OsZIP4 in the shoots of both genotypes, indicating that all these genes may participate in rice zinc nutrition. Furthermore, the expression of OsZIP3 and OsZIP4 was found to be much stronger in the roots of IR8192 than those of Erjiufeng, which suggests that these genes may contribute to high Zn efficiency in rice. The expression patterns and the roles of other OsZIPs are also discussed on the basis of the phylogenetic tree of ZIP proteins and RT-PCR analysis of the two rice genotypes with different zinc efficiency.

Enhancement of bioremediation by Ralstonia sp. HM-1 in sediment polluted by Cd and Zn

In this study, the potential for the application of the bioaugmentation to Cd and Zn contaminated sediment was investigated. A batch experiment was performed in the lake sediments augmented with Ralstonia sp. HM-1. The degradation capacity of 18.7mg-DOC/l/day in the treatment group was bigger than that of the blank group (4.4mg-DOC/l/day). It can be regarded as the result of the reduction of the metal concentration in the liquid phase due to adsorption into the sediments, with the increased alkalinity resulting from the reduction of sulfate by sulfate reducing bacteria (SRB). The removal efficiency of cadmium and zinc in the treatment group was both 99.7% after 35 days. Restrain of elution to water phase from sediment in the Ralstonia sp. HM-1 added treatment group was also shown. In particular, the observed reduction of the exchangeable fraction and an increase in the bound to organics or sulfide fraction in the treatment group indicate its role in the prevention of metal elution from the sediment. Therefore, for bioremediation and restrain of elution from the sediment polluted by metal, Ralstonia sp. augmentation with indigenous microorganism including SRB, sediment stabilization and restrain of elution to surface water is recommended.

Estimation of Protective Efficiency of Oil-based Compositions Containing Zinc and Graphite Powders Against Steel Atmospheric Corrosion

Zinc-containing oil-based compositions containing 75 wt. % zinc powder protect carbon steel in the natural conditions of urban atmosphere for a year with the protective efficiency equal to 96 %. More expedient binding is waste motor oil. The insertion of 4 wt. % graphite dust allows to decrease a content of Zn powder in the composition to 60 wt. % without essential alteration of the protective efficiency. The corrosion potential of the steel electrode covered with the oil composition containing 75 wt. % Zn powder or 60 wt. % Zn powder and 4 wt. % graphite dust in the 3 % NaCl solution is near Zn electrode potential. The polarization curves are close to ones of metal zinc. The properties of the above oil compositions were studied by the electrochemical impedance spectroscopy method too. The values of the equivalent scheme parameters satisfactorily correlate with data of the gravimetrical corrosion tests and the results of the polarization measurements and allow to explain the peculiarities of the zinc-containing oil compositions and an influence of their modification with the graphite powder.

Selective Leaching of Zinc from Spent Zinc-Carbon Battery with Ammoniacal Ammonium Carbonate

This paper describes the ammoniacal ammonium carbonate leaching behavior of zinc and manganese from spent zinc-carbon batteries. For selective extraction of Zn from the spent zinc-carbon battery, leaching tests were carried out as a function of process parameters such as concentration of (NH4)2CO3, ammonia, temperature, time and pulp density. Physical methods of separation such as crushing was applied to reduce the material to 10–20 mm size followed by magnetic separation to separate iron with a recovery about 10 mass% leaving most of Zn and Mn in the non-magnetic fraction. Non-magnetic fraction was further subjected to sieving to separate 2.46 mm over and under size fractions. The oversize material was processed by eddy current separation to recover zinc sheet and carbon rods and plastics. The under size material with chemical composition of Zn 15.5 mass%, Mn 17.5 mass%, and Fe 1.4 mass% was used for leaching studies. Under the optimum leaching conditions (2.0 kmol/m 3 (NH4)2CO3 and 4.0 kmol/m 3 ammonia, 40 � C, 100 g/L pulp density, 30 min and 250 rpm), the leaching efficiency of zinc and manganese was 80.2% and less than 0.1%, respectively, indicating the selective recovery of zinc from the spent zinc-carbon battery. An overall zinc recovery is about 88%. [doi:10.2320/matertrans.MRA2008164]

Changes in nutrient profile of soil subjected to bioleaching for removal of heavy metals using Acidithiobacillus thiooxidans

Studies were carried out to assess changes in nitrogen, phosphorus and potassium contents in soil during bioleaching of heavy metals from soil contaminated by tannery effluents. Indigenous sulfur oxidizing bacteria Acidithiobacillus thiooxidans isolated from the contaminated soil were used for bioremediation. Solubilization efficiency of chromium, cadmium, copper and zinc from soil was 88, 93, 92 and 97%, respectively. However, loss of nitrogen, phosphorus and potassium from the soil was 30, 70 and 68%, respectively. These findings indicate that despite its high potential for removal of heavy metals from contaminated soils, bioleaching results in undesirable dissolution/loss of essential plant nutrients. This aspect warrants urgent attention and detailed studies to evaluate the appropriateness of the technique for field application.

Differential changes in photosynthetic capacity, 77 K chlorophyll fluorescence and chloroplast ultrastructure between Zn‐efficient and Zn‐inefficient rice genotypes (Oryza sativa) under low zinc stress

The relationship of zinc (Zn) efficiency in rice to differential tolerance of photosynthetic capacity and chloroplast function to low Zn stress was studied using Zn-efficient (IR8192) and Zn-inefficient (Erjiufeng) rice genotypes (Oryza sativa L.). Zinc deficiency caused extensive declines in leaf chlorophyll (Chl) content, ratios of chl a:b, Pn, Fv/Fm and Fv/Fo, indicating that the intrinsic quantum efficiency of the photosystem II (PSII) units was damaged. A greater decline was observed in the inefficient genotype (Erjiufeng) than the efficient genotype (IR8192). The 77 K chl fluorescence emission spectrum revealed that Zn deficiency blocked energy spillover from PSII to PSI and more excitation energy was distributed to PSII in IR8192 than Erjiufeng. The spectrum of Zn-deficient Erjiufeng was completely disordered, implying that the photosynthetic centers were seriously damaged. Electron microscopy showed that Zn deficiency caused a severe damage to the fine structure of chloroplasts, but IR8192 had a better preserved chloroplast ultrastructure as compared with Erjiufeng. These differences may result from the higher levels of the antioxidant enzyme activities and lower oxidant stress level in IR8192. These results indicate that Zn deficiency decreases leaf photosynthetic capacity primarily by reducing the number of PSII units per unit leaf area, and also reducing the photochemical capacity of the remaining PSII units. Therefore, the maintenance of more efficient photochemical capacity under low Zn stress is a key factor for the high Zn efficiency in rice, which may result from less antioxidant damage caused by low Zn to the chloroplast ultrastructure.

Cytogenetic Studies on Nine Genotypes of Phaseolus vulgaris L. Cultivated in Egypt in Relation to Zinc Efficiency

This investigation deals with variations in karyotype features, nuclear DNA content and nuclear volume in nine genotypes of Phaseolus vulgaris that show different adaptations to Zinc Deficiency (ZD). In addition, this study addresses the correlation between chromosome length, nuclear DNA amount and nuclear volume on one hand and the capacity of the examined genotypes to tolerate Zn deficiency on the other hand. It was found that Zn Efficiency (ZE) genotypes have the longer chromosomes, higher amounts of DNA content and larger nuclear volume than ZD genotypes.

Grain zinc, iron and protein concentrations and zinc-efficiency in wild emmer wheat under contrasting irrigation regimes

Micronutrient malnutrition, and particularly deficiency in zinc (Zn) and iron (Fe), afflicts over three billion people worldwide, and nearly half of the world’s cereal-growing area is affected by soil Zn deficiency. Wild emmer wheat [Triticum turgidum ssp. dicoccoides (Korn.) Thell.], the progenitor of domesticated durum wheat and bread wheat, offers a valuable source of economically important genetic diversity including grain mineral concentrations. Twenty two wild emmer wheat accessions, representing a wide range of drought resistance capacity, as well as two durum wheat cultivars were examined under two contrasting irrigation regimes (well-watered control and water-limited), for grain yield, total biomass production and grain Zn, Fe and protein concentrations. The wild emmer accessions exhibited high genetic diversity for yield and grain Zn, Fe and protein concentrations under both irrigation regimes, with a considerable potential for improvement of the cultivated wheat. Grain Zn, Fe and protein concentrations were positively correlated with one another. Although irrigation regime significantly affected ranking of genotypes, a few wild emmer accessions were identified for their advantage over durum wheat, having consistently higher grain Zn (e.g., 125 mg kg−1), Fe (85 mg kg−1) and protein (250 g kg−1) concentrations and high yield capacity. Plants grown from seeds originated from both irrigation regimes were also examined for Zn efficiency (Zn deficiency tolerance) on a Zn-deficient calcareous soil. Zinc efficiency, expressed as the ratio of shoot dry matter production under Zn deficiency to Zn fertilization, showed large genetic variation among the genotypes tested. The source of seeds from maternal plants grown under both irrigation regimes had very little effect on Zn efficiency. Several wild emmer accessions revealed combination of high Zn efficiency and drought stress resistance. The results indicate high genetic potential of wild emmer wheat to improve grain Zn, Fe and protein concentrations, Zn deficiency tolerance and drought resistance in cultivated wheat.

Estimation of Protective Efficiency of Oil-Based Compositions Containing Zinc and Graphite Powders Against Steel Atmospheric Corrosion

not Available.

Improved efficiency of zinc phthalocyanine/C60 based photovoltaic cells via nanoscale interface modification

The photovoltaic performance of zinc phthalocyanine (ZnPc)∕C60 heterojunctions is improved by alternately depositing ultrathin active layers between the two bulk layers. Using a proper multilayer structure, a 60% improvement in conversion efficiency under AM1.5 illumination is obtained, in comparison with that of flat heterojunctions. Transmission electron microscope investigations reveal an effective phase separation of ZnPc and C60 and a high degree of crystalline ordering of C60 in this system. The authors propose that an interpenetrating interface is formed, which facilitates both exciton separation and charge transport, and enhances the photocurrent from ZnPc due to an extended photoactive region.

Marschner reviews: A new initiative in delivering cutting-edge science in soil–plant interactions

Soil–plant interactions, which have been studied for well over a century (Hinsinger and Marschner 2006), represent one of the most exciting challenges of scientific endeavours of the present century. These studies cover a wide range of topics, from chemistry to molecular biology, and from rhizosphere to ecosystems. Soil–plant interactions have been the focus of agriculture-oriented studies worldwide for many years; however, in the last decade, much attention has been shifted towards issues related to global change, such as greenhouse gas emission from soil–plant systems, and soil carbon management. This trend is evidenced by the fact that among the 100 papers involving ‘‘soils’’ listed as highly cited papers, about 60% are related to soil biology, soil carbon in particular (Web of Science http://portal. isiknowledge.com/portal.cgi?DestApp=WOS& Func=Frame). Highly cited review papers (all citation classics, i.e. all cited over a hundred times) published in Plant and Soil include Haynes (1982) on effects of liming on phosphorus availability, Gorham et al. (1985) discussing salt tolerance, Melillo et al. (1989) dealing with carbon and nitrogen dynamics in soil, Graham et al. (1992) reviewing zinc efficiency in cereals, Lynch and Whipps (1990), and Jones (1998), both dealing with carbon flow in the rhizosphere, and Marschner and Dell (1994), on nutrient uptake in mycorrhizal symbioses. The review papers on plant adaptations to acid soils (Marschner 1991) and aluminium (Kinraide 1991), plant strategies for iron acquisition (Marschner and Romheld 1994), responses of soil biota to elevated atmospheric CO2 levels (O’Neill et al. 1987, 1994), symbiotic nitrogen fixation (Mariotti et al. 1981; Peoples et al. 1995), soil microbial diversity and sustainability (Kennedy and Smith 1995), nitrogen emissions from agricultural soils (Mosier et al. 1996), and on effects and of adaptation of anoxia (Drew 1983) have equally appealed to a very large number of readers for prolonged periods. The authoritative review by Vogt et al. (1996) on root dynamics in forest ecosystems as dependent on climate and forest type also continues to be cited. These reviews show the breadth of Plant and Soil as well as the enormous appreciation for the reviews that have been published in the journal over many years. That is why we have decided to start a new series of regular, authoritative reviews: our Marschner reviews. These review papers are by invitation only, as further explained below. Our citation classics are by no means restricted to review papers. Wijler and Delwiche (1954) published our very first citation classic, reporting on denitrifying H. Lambers (&) L. Bultynck University of Western Australia, Crawley, Australia e-mail: hlambers@plants.uwa.edu.au

Effect of ultrasound on the dissolution of copper from copper converter slag by acid leaching

This work presents the optimum conditions of dissolution of copper in copper converter slag in sulphuric acid ferric sulphate mixtures in the presence and absence of ultrasound. The Taguchi method was used to determine the optimum conditions. The parameters investigated were the reaction temperature, acid concentration, ferric sulphate concentration and reaction time. The optimum conditions for the maximum dissolution of copper were determined as follows: reaction temperature, 65 °C; acid concentration, 0.2 M; ferric sulphate concentration, 0.15 M; reaction time 180 min. Under these conditions, extraction efficiency of copper, zinc, cobalt, and iron from slag were 89.28%, 51.32%, 69.87%, and 13.73%, respectively, in the presence of ultrasound, while they are 80.41%, 48.28%, 64.52%, and 12.16%, respectively, in the absence of ultrasound. As seen from the above results, it is clear that ultrasound enhances on the dissolution of Cu, Zn, Co and Fe in the slag.

Extraction of zinc(II), iron(II) and iron(III) from chloride media with dibutylbutylphosphonate

The extraction of zinc(II), iron(II) and iron(III) with solutions of dibutylbutylphosphonate (DBBP) from hydrochloric acid solutions was studied. Iron(II) was only slightly extracted by DBBP. The isotherms of zinc(II) extraction with DBBP were compared with those for tributylphosphate (TBP). They indicated that extraction efficiency was higher for DBBP than for TBP. The transfer of iron(III) was effective, due to the presence of a neutral chlorocomplex at high Cl − and HCl concentrations. Thus, selective zinc(II) separation from strong chloride solution containing iron(III) with DBBP was not possible. Addition of kerosene (20–40 vol.%) increased the hydrophobicity of DBBP while slightly decreasing the efficiency of zinc(II) extraction. As a result, water content in the organic phase decreased with decreasing DBBP concentration from almost 9 to about 4%. Hydrochloric acid co-extraction was observed, and it decreased in the following order of the accompanying metal ions: Zn(II) > Fe(II) > Fe(III) for 100 and 80% DBBP. Above a DBBP concentration of 40 vol.% zinc(II) complexes with two DBBP molecules in the organic phase. At lower DBBP concentrations zinc(II) species form a complex with only one DBBP molecule. DBBP enables selective removal of zinc(II) in the presence of iron(II). The selectivity of zinc(II) extraction over iron(II) with 80% DBBP is very high and exceeds 10 3. Zinc(II) can be effectively stripped (over 90%) from loaded DBBP with water in three stages.