Initial Zinc Concentration Research Articles

Ion exchange recovery of zinc from chloride and chloride–sulfate solutions

The present work is focused on sorption recovery of zinc (II) ions from chloride and chloride–sulfate solutions on some commercial anion exchangers with different physical and chemical structures. Initial zinc concentration was 1.0–5.0 mmol/L. HCl concentration in initial solutions was from 0.001 to 4.0 mol/L, whereas chloride–sulfate systems were investigated at molar ratios of HCl:H 2SO 4 = 1:1; 1:2 and 1:4. Acids concentrations were 0.001 and 2.0 mol/L. It was shown that the anion exchangers investigated possess good sorption and kinetic properties. After ion exchange recovery, zinc was effectively eluted by means of 2 M HCl. The elution results in complete zinc removal from the sorbents investigated and complete purification of solutions from zinc. Based on the data obtained, the anion exchangers Purolite S 985, Purolite A 500 and AM-2B can be recommended for zinc recovery from industrial solutions and waste water.

Effect of anions on removing Cu 2+, Mn 2+ and Zn 2+ in electrocoagulation process using aluminum electrodes

In the present study, the performance of electrocoagulation process with aluminum electrodes in the treatment of Cu 2+, Zn 2+ and Mn 2+ containing aqueous solutions was investigated by depending on type of anion in solution, considering some operating conditions such as initial metal concentration and pH. Results obtained from synthetic wastewater showed that type of anion in solutions has a significant effect on the metal removal. The initial concentration of zinc influenced significantly the performance of electrocoagulation process as compared with the results obtained from Mn and Cu metals. Anions studied did not generate an important difference between pH variations. Best removals for three metals were achieved with increasing the pH in the presence of both anions. Total removals of copper and zinc reached almost 100% after 5 min at pH values > 7. At the end of the experiments for 35 min, the Mn removals were 85 and 80% in the presence of sulfate and chloride anions, respectively.

Factorial design analysis for sorption of zinc on hydroxyapatite

A factorial design was employed to evaluate the quantitative removal of zinc from aqueous solutions on synthesized hydroxyapatite. The experimental factors and their respective levels studied were the initial zinc concentration in solution (35≤CZn≤85mg/L), adsorbent dosage (4.5≤Csusp≤9.5g/L), Ca/P molar ratio (1.667≤Ca/P≤2) and calcination temperature of hydroxyapatite (600≤TCal≤800°C). The adsorption parameters were analysed statistically by means of variance analysis by using the STATISTICA software.The experimental results and statistical analysis show that increasing in the calcination temperature from 600 to 800°C decrease the zinc adsorption whereas the increase of adsorbent dosage increases it. Based on the analysis of variance and the factorial design of experiments, adsorbent dosage has a positive effect on the removal of zinc, whereas zinc concentration, Ca/P molar ratio and calcination temperature have a negative effect on this process. The factorial results also demonstrate the existence of statistically significant binary interactions of the experimental factors. The experimental results were fitted to the Langmuir and Freundlich equations to find out adsorption capacities. In most cases, the results indicate that the sorption data fits well in the Freundlich isotherm model.The results of XRD analysis, pHPZC and pHFinal values indicated that ion exchange and dissolution/precipitation mechanisms predominate for the sorption of zinc on our hydroxyapatite.

The electrowinning of cadmium in the presence of zinc

The electrowinning of cadmium in the presence of zinc has been investigated. As such, the effects of initial cadmium concentration (40–160 g/L), current density (50–150 A/m 2), free acid concentration (0–196 g/L), initial zinc concentration (20–120 g/L), and temperature (25–70 °C) on current efficiency (CE) and specific power consumption (SPC) in electrowinning of cadmium have been examined. Under the optimum working conditions (initial cadmium concentration 120 g/L, current density 80 A/m 2, free acid concentration 98 g/L, and temperature 40 °C), CE and SPC were 98% and 1.21 kWh/kg, respectively. The presence of zinc (20–120 g/L) had no systematic effect on CE and SPC, but decreased the purity of the deposited cadmium down to 99.92%.

Zinc removal from acid rock drainage by clinoptilolite in a slurry bubble column

Zinc uptake by adsorption from zinc-spiked acid rock drainage (ARD) on natural clinoptilolite was investigated in a slurry bubble column. The effects of contact time, adsorbent particle size, initial aqueous zinc concentration, adsorbent dosage and initial solution pH on zinc immobilization were examined. Langmuir and Freundlich adsorption isotherm equations were fitted to the experimental data. Finer clinoptilolite particles adsorbed more zinc, probably due to more accessible surface area. Zinc adsorption improved as pH increased from 2 to 5, probably due to competition of H + at low pH. A slurry loading of 200 g clinoptilolite per kilogram ARD and an initial aqueous pH of 4 appear to be suitable conditions for removing zinc from ARD. While the aqueous concentration of zinc in ARD was reduced significantly in a single run, 8 cycles of adsorption in series were needed to reduce the zinc concentration to the regulated level.

Removal of zinc by live, dead, and dried biomass of Fusarium spp. isolated from the abandoned-metal mine in South Korea and its perspective of producing nanocrystals

Bioremediation is an innovative and alternative technology to remove heavy metal pollutants from aqueous solution using biomass from various microorganisms like algae, fungi and bacteria. In this study biosorption of zinc onto live, dead and dried biomass of Fusarium spp. was investigated as a function of initial zinc(II) concentration, pH, temperature, agitation and inoculum volume. It was observed that dried, dead and live biomass efficiently removed zinc at 60 min at an initial pH of 6.0 ± 0.3. Temperature of 40 °C was optimum at agitation speed of 150 or 200 rpm. The initial metal concentration (10–320 mg L −1) significantly influenced the biosorption of the fungi. Overall, biosorption was high with 30–60% by dried, live and dead biomass. In addition to this, the potential of Fusarium spp. to produce zinc nanocrystals was determined by transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction and fourier transform infrared spectroscopy, which showed that dead biomass was not significantly involved in production of zinc nanocrystals.

Examination of zinc uptake in a combined system using sludge, minerals and ultrafiltration membranes

This work investigates the feasibility of zinc removal from wastewater with the use of ultrafiltration (UF) membranes combined with natural minerals and sludge. Activated sludge obtained from a membrane bioreactor (MBR) was enriched with initial zinc concentration of 320 mg/L and specific concentrations of zeolite, bentonite and vermiculite. The mixture was agitated and placed inside a batch ultrafiltration unit where the filtration process took place. The effect of several parameters on zinc removal was investigated including the mineral type, quantity and grain size, the metal–mineral contact time and the associated kinetics, the pH value, the zinc initial concentration and sludge mixed liquor suspended solids (MLSS) concentration. The ultrafiltration membranes without any mineral addition were able to remove 38–78% of zinc ions due to biosorption on sludge flocs. The addition of minerals increased the Zn(II) removal efficiencies reaching in some cases more than 90%. Bentonite was the most effective mineral in zinc removal followed by vermiculite. Alkaline pH values favoured zinc removal due to enhanced chemical precipitation. A three-stage adsorption process was identified where the boundary layer diffusion process was followed by a two-stage intraparticle diffusion process. Powder size vermiculite was more effective than granular vermiculite in zinc removal. Minerals also resulted in membrane fouling mitigation since the membrane permeability drop was reduced. The combined sludge–mineral–ultrafiltration system can be effectively employed for the treatment of industrial wastewater.

The role of liquid membranes in the selective separation and recovery of zinc for the regeneration of Cr(III) passivation baths

® 272 abstract This work aims at the separation of the metallic impurities, namely Zn 2+ and Fe 3+ , from trivalent chromium spent passivation baths used in the galvanic industry by means of selective liquid membranes as an efficient and necessary step in the regeneration of the baths for their useful life extension. A Liqui-Cel hollow fiber membrane contactor separated the spent bath from an emulsion phase constituted of an organic liquid membrane consisting of Cyanex®272, kerosene and 1-decanol and an acidic receiving solution. Real spent passivation baths were used as feed solutions, with complex composition, being the main metallic content: Cr3+ (4500-9350 mg L−1), and Zn2+ (2500-11,780 mg L−1) and Fe3+ (20-93 mg L−1) as tramp ions. The influence of different operational variables on the kinetics of the separation of zinc and chromium as well as on the enrichment of zinc over iron and chromium in the stripping phase was investigated. The variables under study were the pH of the feed mixture, the initial zinc concentration, the carrier concentration in the liquid membrane, and the type and concentration of acid, hydrochloric acid and sulphuric acid used as stripping agent. © 2010 Elsevier B.V. All rights reserved.

Biosorption of Zn(II) by live and dead cells of Streptomyces ciscaucasicus strain CCNWHX 72-14

The biosorption characteristics of Zn(II) using live and dead cells of Streptomyces ciscaucasicus strain CCNWHX 72-14 as biosorbents have been investigated in the present research. Optimum conditions for biosorption were determined to be: pH adjusted to 5.0, agitated at 90 rpm and at a dose of 2 g/L. For initial zinc concentrations of 1–150 mg/L, batch biosorption data of live biomass preferred to be simulated with Freundlich model while those of dead strain fit Langmuir isotherm well. Experimental maximum biosorption capacity turned out to be 42.75 mg/g (0.654 mmol/g) for living material and 54 mg/g (0.826 mmol/g) for dead sorbents, respectively. The pseudo-second-order equation, instead of the pseudo-first-order one, was chosen to describe the time course biosorption process. In contrast to live biosorbents, dead biomass seemed to have lower binding strength with higher desorption efficiency at pH 1.0. Competitive biosorption revealed the order of competing metal ion to be: Cu 2+ > Cd 2+ > Ni +. FT-IR analysis indicated that more functional groups were involved in the biosorption process of dead adsorbents, compared with those linked to live biomass. Taken together, it can be concluded that dead cells of CCNWHX 72-14 were better and cheaper biosorbents than live ones.

Influence of operation variables on the recovery of zinc from spent pickling effluents using the emulsion pertraction technology

Spent pickling effluents coming from hot-dip galvanizing processes contain high amounts of zinc and other metallic compounds in hydrochloric acid media. Thus, the effluent has a strong hazardous character and needs to be treated before disposal. Emulsion pertraction (EPT) with hollow fiber modules, can be considered as a clean alternative able to carry out the separation and recovery of zinc. After demonstrating the viability of EPT for the treatment of this kind of effluents in previous works using tributyl phosphate (TBP) as extractant agent and service water as back-extraction agent, several experiments were performed to analyse the influence on the extraction (EX) and back-extraction (BEX) kinetics of the main operation variables: (i) initial zinc concentration in the aqueous feed phase, (ii) organic phase/stripping phase volume ratio in the emulsion stream and (iii) emulsion volume.

Batch adsorption of zinc on tea factory waste

Approximately 857,000 tonnes of tea is produced in India per year, which is 27.4% of total world production. After processing, tea factory waste is about 190,400 tonnes. Batch adsorption studies have been carried out for evaluating the suitability of tea factory waste as a low-cost adsorbent for the removal of zinc. The effects of various parameters like pH, adsorbent dose, initial concentration of zinc, temperature on adsorption performance were studied using tea factory waste (TFW). The study shows the adsorption potential of Indian TFW for the removal of Zn(II) from aqueous solution. The color removed and sized TFW show very good adsorption for Zn(II) in synthetic wastewater at pH 4.2 and room temperature. The maximum adsorption capacity of Zn(II) per gram of TFW was calculated as 8.9±0.08 mg. The results prove that the low-cost tea factory waste can be used as a potential adsorbent in developing countries like India.

Equilibrium and thermodynamic analysis of zinc ions adsorption by olive oil mill solid residues

This work investigated the equilibrium batch dynamics of using olive oil mill solid residues as an adsorbent for zinc removal from aqueous solutions. It was found that a sorbent concentration of 4 g L −1 achieved the best removal percentage and the best sorbent capacity. Adsorption equilibrium was reached in 60 min for an initial zinc concentration of 0.25 mmol/L and 180 min for an initial zinc concentration of 1–3 mmol/L. A particle size of olive mill residue ranging from 0.85 to 1.18 mm was used in the study. It was found that the maximum adsorption capacity of zinc was at a pH value of 5.0. It was found that q max for zinc ions, was 5.63, 6.46, and 7.11 mg g −1 at temperature values of 298, 308, and 328 K, respectively. The data pertaining to the sorption dependence upon metal ion concentration could be fitted to a Langmuir isotherm model. The second-order kinetic model provided the best correlation of the data. The change in entropy (Δ S°) and heat of adsorption (Δ H°) for zinc ions adsorption on olive mill solid residues were estimated as −1419 kJ kg −1 K −1 and 4.7 kJ kg −1, respectively. The examined low-cost adsorbent could offer an effective way to decrease zinc ions concentration in wastewater.

Biosorption of Zn(II) from an aqueous solution by Erythrina variegata orientalis leaf powder

In the present investigation, the biosorption is carried out in a batch process to test the suitability of abundantly and freely available plant based material, Erythrina variegata orientalis (Indian coral tree) leaf powder, as an adsorbent for removal of Zn(II) from aqueous solution. The influence of various process parameters like agitation time, adsorbent size and dosage, pH of the aqueous solution and initial zinc concentration is studied. It is observed that there is a significant increase in percentage removal of Zn(II) as pH increases from 2 to 3 and attains maximum when pH is 7. The agitation time is to be 60 min. The Langmuir isotherm is more suited for biosorption followed by Freundlich isotherm. The biosorption of Zn(II) follows pseudo-second-order kinetics and is exothermic, irreversible and spontaneous. Key words: Biosorption, zinc, leaf powder, kinetics.

Time focused measurements of roof runoff quality

Runoff properties and their changes during runoff of a 14 year old zinc roof were investigated. Zinc, lead, cadmium, pH value, rain intensity and electric conductivity have been measured for a period of one year. A runoff rate of 3.73 g/m 2 a and a volume weighted mean zinc concentration of 4.9 mg/L were determined. First flush behaviour was observed in 93% of runoff events. Low rain intensities are correlating with higher zinc concentrations in runoff, whereas the duration of antecedent dry periods could not directly be linked with initial zinc concentrations.

Use of Serum Zinc Concentration as an Indicator of Population Zinc Status

Assessing the prevalence and severity of zinc deficiency in populations is critical to determine the need for and appropriate targeting of zinc intervention programs and to assess their effectiveness for improving the health and well-being of high-risk populations. However, there is very little information on the zinc status of populations worldwide due to the lack of consensus on appropriate biochemical indicators of zinc status. The objective of this review was to evaluate the use of serum zinc concentration as an indicator of population zinc status. We have reviewed the response of serum zinc concentration to dietary zinc restriction and zinc supplementation. In addition, we completed pooled analyses of nine zinc intervention trials in young children to assess the relations between serum zinc concentration of individuals before treatment and their responses to zinc supplementation. Also, in updated combined analyses of previously published data, we investigated the relation between the mean initial serum zinc concentration of a study population and their mean growth responses to zinc supplementation in randomized intervention trials among children. The results from depletion/repletion studies indicate that serum zinc concentrations respond appreciably to severe dietary zinc restriction, although there is considerable interindividual variation in these responses. There is also clear evidence that both individual and population mean serum zinc concentrations increase consistently during zinc supplementation, regardless of the initial level of serum zinc concentration. By contrast, an individual's serum zinc concentration does not reliably predict that person's response to zinc supplementation. Serum zinc concentration can be considered a useful biomarker of a population's risk of zinc deficiency and response to zinc interventions, although it may not be a reliable indicator of individual zinc status.

Pelletizing and alkaline leaching of powdery low grade zinc oxide ores

Low grade powdery zinc oxide ores (5.2% Zn, <2 mm) are mixed with cement 5 wt.%, pelletized and solidified. The diameters of the pellets obtained are between 5 mm to 8 mm. When the pellet solidification periods are 3 days, 10 days and 45 days respectively, the alkaline leaching rates of zinc in the pellets are up to 92.2%, 87.3% and 72.9% respectively. Decreasing the solidification time can reduce reaction time, increase dissolution of zinc in pellets and lower the effect of initial zinc concentration on leaching rate. The experiment results show that the minimum solidification time is three days, and the kinetic study indicates that alkaline leaching of the low grade zinc oxide pellets is controlled by the diffusion of the leach liquor through the gangue layer in the whole leach process, and the apparent rate constants are 3.51×10−2 day−1, 8.09×10−3 day−1, 4.74×10−3 day−1 respectively.

Adsorption of zinc from aqueous solution using chemically treated newspaper pulp

Adsorption of zinc was studied using chemically modified newspaper pulp as an adsorbent in the aqueous medium. Quantitative chemical analysis showed the presence of trace quantities of some inorganic elements along with phosphorous in TNP. The experimental adsorption data fitted reasonably well to both Freundlich and Langmuir isotherm. pHzpc of TNP was 5.1, which indicated that the adsorbent was more potential for cationic adsorption. The adsorption kinetic data followed a pseudo-second order model for zinc. Optimum Zn 2+ loading was 9.20 mg/g for 10.31 mg/l initial zinc concentration at pH 5.80. Zn 2+ loading on TNP was dependent on initial zinc concentration. TNP was a potential adsorbent for the removal of Zn from the effluent of electroplating industry.

Zinc Biosorption by Seaweed Illustrated by the Zincon Colorimetric Method and the Langmuir Isotherm

Heavy metals are major pollutants in marine, ground, industrial, and even treated waters. Sorption of heavy metals onto live or dead biological materials (biosorption) is a potential method of removing toxic metals. Zinc and two algae, Ulva sp. and Gymnogongrus torulosus, were evaluated in this study. A linear zinc calibration curve in the range 1–8 mg L-1 was obtained using the zincon colorimetric method. In the biosorption assays, a rapid zinc uptake was observed and kinetic curves stabilized after 60 minutes. Experiments using initial zinc concentrations of 50 mg L-1 showed that 20% and 60% of zinc ions were removed from solution by Ulva sp. and Gymnogongrus torulosus, respectively. Results obtained from varying initial zinc concentrations allowed data fitting to Langmuir model with a good correlation. The maximum zinc uptake capacity and affinity constant obtained for Gymnogongrus torulosus were higher than those for Ulva sp. Maximum zinc uptake capacities were 42.8 x10-3 and 26.8 x10-3 for Gymnogon...

Shape alterations of ZnO nanocrystal arrays fabricated from NH 3·H 2O solutions

Well-aligned crystalline ZnO nanorod arrays were synthesized via an aqueous solution route with ammonia and zinc nitrate as inorganic precursors. ZnO crystalline seed films were firstly coated on ITO substrates for epitaxial growth of rods through sol–gel processing and heat treatment. SEM, TEM, SAED and XRD were utilized to characterize morphologies and structures of ZnO crystals. Heterogeneous nucleation is crucial for rod growth. A broad scope of pH favorable for heterogeneous nucleation was disclosed at zinc concentration from 0.04 to 0.1 M in the inorganic system due to the complex reaction of ammonia with Zn 2+. Elevation of initial zinc concentration or pH promoted growth rate of rods and enlarged rod size. ZnO nanorods were transformed to nanotubes, nanosheets and rods with blanket-like shaped surface mainly by secondary pH adjustment. All ZnO nanocrystals are wurtzite structure preferentially oriented in c-axis direction.

Early Stages of ZnS Growth Studied by Stopped-Flow UV Absorption Spectroscopy: Effects of Educt Concentrations on the Nanoparticle Formation

The growth of ZnS nanoparticles by precipitation from supersaturated aqueous solution is studied by stopped-flow UV absorption spectroscopy. The average size, size distribution, and concentration of the particles are monitored within the sub-second time regime with a resolution of 1.28 ms. Particle growth at these early stages is governed by pronounced ripening. The UV absorption data strongly suggest that growth occurs by preferential adsorption of HS- anions relative to Zn(2+) or ZnOH(+) cations. Correspondingly, the initial sulfide concentration has a much more pronounced influence on the growth kinetics than the initial zinc concentration. These findings are verified by zeta-potential measurements which confirm that the particle surfaces are negatively charged under near-neutral pH conditions.