Zinc Smelter Research Articles

Cadmium Depth Separation Method in Polymetallic Sulfate Solution: Flow-Electric Field Enhanced Cementation Combined with M5640 Extraction

An efficient and controllable process for separating copper and cadmium was required to be developed due to the high cost of the long separation process of copper cadmium slag generated from the zinc smelting process. Therefore, a new process for the application and deep separation of copper and cadmium was developed by combining the Circulating Flow Electric (CFE) cadmium cement method and the 2-hydroxy-5-nonyl formaldehyde oxime (M5640) copper extract method. The process firstly removed copper ions utilizing M5640 and obtained a primary purification solution, followed by CFE method to extract cadmium in depth. The effects of extractant volume fraction, pH, Oil phase/Aqueous phase (O/A) ratio and reaction time on the removal of copper ions were investigated. The results showed that the removal of copper was above 97%, while the removal of zinc and cadmium was below 1.6%, respectively, proved that the selectivity of M5640 for copper was significantly higher than that for metals such as cadmium and zinc. The characterization results indicate that the oxygen on the hydroxyl group and the nitrogen on the oxime group co-ligated with the copper ions and subsequently formed chelated extracts. That was the mechanism of the copper ion purification by M5640. Furthermore, the extraction of high purity cadmium was carried out in the extraction residual liquid. A novel method of cadmium removal enhanced by coupling an electric field with a circulating flow field was developed and applied to the cement cadmium from sulfate solutions. The optimal process conditions of the method were explored, which were further fitted into statistical equations and optimized by response surface analysis. Since the fitted theoretical results were close to the experimental results, the optimization was considered as effective. The optimized experimental parameters were 6.23 mL/s of flow rate, 48.14 mA/cm2 of current density, 2.25 of pH, and 0.93 of anode/cathode area ratio, respectively. Next, the extraction electrical efficiency, purity and its weight distribution in the cell of cadmium sponge under different flow fields were calculated and measured. The results were analyzed to prove the existence of an optimal interval for the distribution of cadmium under high-speed flow field.

The impact of exposure to lead on the occurrence of insomnia in shift workers of the Zinc Steelworks in Miasteczko Śląskie

Introduction: The aim of the study was to assess the effect of lead concentration and shift work on the occurrence of insomnia in the employees of the Zinc Steelworks in Miasteczko Śląskie in Poland. Material and methods: The study group consisted of 240 employees of the zinc smelter, reporting periodic and control examinations to the Occupational Medicine Clinic. Respondents were asked to complete a questionnaire consisting of the Athens Insomnia Scale and questions about the place and nature of work. Results: Analyzing the results of lead and zinc proporphiryn( ZPP) levels in the shift and non-shift subgroups of the study group, a slightly higher mean level of lead and ZPP was found in the shift subgroup. Using logistic regression, the probability of insomnia was determined depending on the concentration of lead and ZPP in the organism. As the level of lead and ZPP increases in the study group, the probability of insomnia increases. It is the largest among the examined group working in shifts. Conclusions: As the blood lead level increases, the likelihood of insomnia in steel plant workers increases.

Exploring the potential health and ecological damage of lead–zinc production activities in China: A life cycle assessment perspective

Lead and zinc are indispensable nonferrous metals in the current industrialized society because of their position as raw materials for various industrial products. However, the massive environmental burden imposed by the activities of the lead–zinc industry will trigger potential social impacts. This study systematically evaluated the environmental and social economic burden of lead–zinc production activities at the national level during the entire industrial chain via life cycle assessment coupled with economic assessment method. China, the world's largest lead and zinc metal producer, was used as an example. Results demonstrated that in 2018, the national values of the potential threats to human health, ecosystem quality, and social economy were 3.55 × 105 DALY, 1.27 × 104 species. yr, and 3.90 × 1010 $, respectively. The potential social economic impact of China's lead–zinc production increased by 49% from 2008 to 2018. Direct emission was the primary contributor in most environmental impact categories (i.e., freshwater ecotoxicity, particulates formation, non-carcinogens, and carcinogens), except for global warming, in which electricity generation was the main contributor. Heavy metals emitted during the mining and dressing stage provided the predominant contribution to ecosystem quality degradation. Copper discharged into water was identified as a key substance that accounted for 59% of the overall potential threats. Henan, Hunan, and Yunnan provinces were the dominant provinces contributing to the overall social economic impacts of lead–zinc smelting. Additionally, association analysis indicated a significant correlation between the lead–zinc smelting activities and multiple cancers (e.g., stomach, brain, liver, and colon cancers). Adopting environmentally-friendly and cost-effectiveness wastewater treatment technology (e.g., adsorption) or water reuse is recommended to reduce heavy metal emissions. The development of renewable electricity and implementing cross-regional electricity transmission options have important benefits for reducing the environmental and social economic burden of the lead–zinc production activities. The application of long-term marginal power would alleviate the environmental burden in global warming category by 32.1%. The dust removal technologies of selective catalytic reduction, electrostatic precipitator, and wet flue gas desulfurization are implemented in combination to remove carcinogenic heavy metals from the air to reduce health risks and socio-economic losses.

Efficient recovery of valuable metals from lead-zinc smelting by-products by ultrasonic strengthening

As a byproduct of lead and zinc smelting, zinc oxide dust often contains abundant valuable metals such as zinc and germanium. To improve the leaching of zinc and germanium in sulfuric acid, the correlation between germanium and other elements in zinc oxide dust, the phase composition of the main elements, and Eh-pH dominant area of germanium were analyzed. Finally, ultrasonic waves and potassium dichromate were added to enhance the leaching of zinc and germanium in the leaching process. The results show that the best recoveries of zinc and germanium are 99.25 % and 90.44 %, respectively, under the optimum conditions. Compared with the existing process, the leaching rate is increased by 8 ∼ 10 % and the leaching time is reduced by more than 50 %. There are fewer impurities in the leaching residue after leaching, and the lead content is about 50 % and can be directly recycled back into the lead smelting process for recycling. In conclusion, the oxidation leaching of zinc and germanium from zinc oxide dust with potassium dichromate under ultrasound proves to be efficient, economical and practical.

Life cycle assessment for waste acid treatment in zinc smelting

Lift cycle assessment (LCA) methodology was applied to evaluating and comparing two waste acid disposal processes in zinc smelting. The results indicate that environmental impacts of gas—liquid vulcanization technologies are human toxicity, abiotic depletion potential, and global warming risk, which are mainly caused in neutralizing— evaporating—crystallization unit and electrodialysis unit. As for traditional lime neutralization method, vulcanization unit is the main factor. In this regard, the total environmental impact of traditional lime neutralization method is much higher than that of gas—liquid vulcanization technologies. Furthermore, the sensitive analysis shows that electricity and sodium sulfide (60%) are sensitive factors in two waste acid disposal technologies. In addition, the total cost of disposing a functional unit waste acid in traditional lime neutralization process is nearly 27 times that of the gas—liquid vulcanization waste acid disposal technologies.

Environmental impact of typical zinc smelting that implements solid waste collaborative utilization in China

Environmental impact of typical zinc smelting that implements solid waste collaborative utilization in China

Optimization and application of passive air sampling method for gaseous elemental mercury in Ulsan, South Korea.

We compared uptake rates and concentrations of gaseous elemental mercury (GEM) by passive sampling conditions and investigated the spatial distribution of GEM in Ulsan, the largest industrial city in South Korea. For the optimization of sampling conditions, two outer sampling containers (cylindrical polyethylene terephthalate and two stainless steel bowls), two different sulfur contents of the sorbent (16.3% and 26.3%), and three sampling periods (1, 2, and 3months) were considered. The uptake rates of GEM were not statistically different by the sampling container, but they were increased with the sulfur contents of activated carbon. A sampling condition using two stainless bowls and lower sulfur contents of activated carbon for 2-3months was preferred with the highest precision of GEM concentrations. With the same method, passive air samples were collected for 3months in duplicate from 10 sites in Ulsan. The concentrations of GEM ranged from 3.13 to 11.2ng/m3 (mean 4.65ng/m3), and the highest concentration was measured at a non-ferrous industrial complex. A zinc smelter in the non-ferrous industrial complex was identified as a major mercury source in Ulsan. This study is the first passive air sampling study investigating the spatial distributions of GEM in different types of industrial areas as well as residential areas of Ulsan.

Current Situation and Development Trend of Comprehensive Utilization of Zinc Smelting Slag

Current Situation and Development Trend of Comprehensive Utilization of Zinc Smelting Slag

Factors on the distribution, migration, and leaching of potential toxic metals in the soil and risk assessment around the zinc smelter

Mining activities usually caused soil polluted by potential toxic elements (PTEs). This paper used the analysis of correlation, variance, and power analysis to clarify the relationship and migration characteristic of 90 samples in 30 sampling points at the depths of 30, 100, and 200 cm. The results showed in the weakly alkaline red loam, pH had no significant effect on the total concentration of PTEs in the soil. The greater the depth was, the greater the total concentration of PTEs in the soil. And depth had no significant effect on the soil pH. The cadmium (Cd) migration process in the soil was more severe than other elements. The arsenic (As) migration ability was lower than other elements. Except for chromium (Cr), lead (Pb) and antimony (Sb) had the strongest migration ability. Soil depth and total PTEs concentration had no significant effect on the leaching concentration of As and Sb, whether it was by water leaching or acid leaching. From the perspective of the potential ecological risk index, Pb and Cr had low or no risk, while As, Sb, and Cd needed to be dealt with. From the perspective of Hazard Quotient, Pb, Cr, and Cd have low or no non-carcinogenic risk, while As and Sb did the opposite. This research inspired understanding the process of soil PTEs migration, and helping local government to control the distribution of PTEs.

Assessment of sulfidated nanoscale zerovalent iron for in-situ remediation of cadmium-contaminated acidic groundwater at a zinc smelter

Unprecedented high concentrations of heavy metals have been detected in the groundwater at a zinc smelter in Seokpo, South Korea. The outflow of the contaminated groundwater into the nearby Nakdong River must be prevented by some means such as permeable reactive barrier (PRB). As a reactive material for injection-type PRB, we have tested sulfidated nanoscale zerovalent iron (S-nZVI) to assess its efficacy in remediating the groundwater from the smelter. The S-nZVI efficiently removed Zn, Ni, and Al in the groundwater, and neutralized the groundwater to pH > 6. Sulfidation of nZVI greatly increased the removal of Cd (99.8%) compared to that by nZVI (7.2%). MINEQL+ modeling and particle characterization were performed to elucidate the forms of heavy metals in the solution and on the surface of S-nZVI. Raman and XPS results suggested that FeS on the surface of S-nZVI reacted with Cd(II) and Zn(II), forming more-stable CdS and ZnS. Sequential application of NaHCO3 after S-nZVI treatment in a column setup was suited for the removal of remaining Zn and Fe as well as the reduction of microbial toxicity. This study guides to use of S-nZVI for in-situ remediation of cadmium-contaminated groundwater with other coexisting heavy metals from a zinc smelter.

Study on leaching behaviour of germanium and iron in zinc oxide dust from lead zinc smelting

ABSTRACT Zinc oxide dust from lead zinc smelting is an important raw material for germanium recovery. This article researched the behaviour of germanium and iron in zinc oxide dust leaching in response to the problem of low germanium leaching efficiency. For this purpose, the germanium phase distributions were confirmed, the effects of sulphuric acid concentration, liquid–solid ratio, leaching temperature, and leaching time were determined. According to the findings, germanium exists primarily in the form of soluble germanium oxide and germanates. In addition, the germanium leaching efficiency is most affected by the leaching time, because the leaching iron will be oxidised and create Fe4Ge3O12 precipitation with the leaching germanium if the leaching time is too long, resulting in the decline of germanium leaching efficiency. The leaching efficiency of zinc and germanium can reach 89.05% and 84.32%, respectively, when the sulphuric acid concentration is 150 g/L, the liquid–solid ratio is 5:1, the leaching temperature is 85°C, and the leaching time is 30 min, which is 0.44% and 7.21% higher than that under unoptimised conditions. Furthermore, through sodium sulphite-assisted leaching, the leaching efficiency of germanium is further increased to 89.48%, indicating that reductant-assisted leaching is a direction worthy of study.

Removal of arsenic in acidic wastewater using Lead-Zinc smelting slag: From waste solid to As-stabilized mineral.

High-arsenic wastewater has long been considered a major threat to ecological balance and human health because of its strong toxicity and high mobility. Herein, an environmentally friendly process was proposed for As removal and fixation in the form of As-stabilized mineral, using Lead-Zinc smelting (LZS) slag as the in situ Fe donor, neutralizer, and crystal seed. The slag was dissolved in the wastewater and released Fe and Ca ions, while simultaneously increasing the pH value of the solution to help scorodite synthesis. The dissolved Ca2+ ion preferentially reacted with SO42- ion in the form of CaSO4·2H2O precipitate as in situ "seeds" for As precipitation. The dissolved Fe(II) and As(III) ions were oxidized to Fe(III) and As(V) ions by H2O2, and later reacted with each other to generated amorphous ferric arsenate on the surface of CaSO4·2H2O, and then evolved into scorodite crystals with high stability. With a Fe/As molar ratio of 2, a reaction temperature of 90°C, and a reaction time of 12h, 98.42% of As was effectively precipitated from the wastewater with an initial As concentration of 7530.00mg/L. Moreover, the leached As concentration of the As-bearing precipitate in the TCLP test was 3.46mg/L. The concentration of the residual As and heavy metals ions in the final filtrate was lower than local wastewater discharge standards, successfully realizing the treatment of smelting wastewater. In summary, a prospective process successfully shows a great potential for co-treatment of LZS wastewater and slag, which could advance the large-scale disposal of LZS plants.

Spastic Paraplegia and Ataxia in a Welder.

A 51-year-old welder (nonsmoker) developed subacute lower paresthesias and progressive spastic paraplegia and ataxia. Symptoms appeared 10 days after the first zinc exposure in the yacht construction site (8-hour day/40 days in a confined space with face shield only). Examination revealed loss of vibratory sensation, spasticity, hyperreflexia, and sensory ataxia. Serum heavy metals (Cu 1 mg/L and Pb 4,22 μg/L), B-complex vitamins, and paraneoplastics on serum and CSF were unremarkable. The elevated zinc level (137 μg/dL) was found. Spinal MRI showed combined degeneration (Figure). Myelopathy in zinc smelter workers was reported in the 19th century1 and recently rediscovered in excessive zinc ingestion. Copper secondary deficiency is hypothesized even if the normal copper serum level is reported.2 Two months later, copper became low (0.8 mg/L), a time-dependent process might explain late copper deficiency in our case. Symptoms ameliorated 4 months later with normalization of serum zinc/copper levels.

Ectomycorrhizal diversity on the roots of Pitch pine (Pinus rigida Mill.) saplings as influenced by remediation and soil metal content

From 1913 to 1980, two zinc smelters in Palmerton, Pennsylvania, emitted large quantities of atmospheric pollutants nearly eliminating forests along a ridge above the town. In 2008, a remediation treatment was applied to the land above one of the smelters that included the planting of several locally adapted plant species. It also included mineral fertilization and mycorrhizal inoculation. One of the species, the Pitch pine (Pinus rigida, Mill.), is a native tree that is both tolerant of metalliferous soils and obligatorily ectomycorrhizal. This report summarizes the results of two observational studies conducted 5 years after the remediation treatment. The first study's objective was to compare ectomycorrhizal communities on treated Pitch pine saplings, with communities on naturally regenerating saplings in an adjacent non‐remediated area. The second study's objective was to determine if the composition of the fungal communities on root tips of naturally regenerating Pitch pine saplings differed with distance from the smelters. Fungal community compositions were determined using internal transcribed spacer rRNA sequences. Comparisons of sequences from the remediated and non‐remediated sites revealed that communities at the remediated sites had lower taxonomic diversity and were dominated by members of a genus in the remediation inoculant. The results of the smelter‐proximity study indicated that although fungal diversity did not differ markedly with distance from the smelters, the relative abundances of some taxa were greater on saplings growing directly above the smelters, where the soils contained highest concentrations of zinc and cadmium.

The mechanistic insights into the leaching behaviors of potentially toxic elements from the indigenous zinc smelting slags under the slag dumping site scenario

Since lager quantities of the zinc (Zn) smelting slags were traditionally dumped at the indigenous Zn smelting sites, the release characterization of potentially toxic elements (PTEs) from the Zn smelting slags under various environmental conditions were of great significance for an environmental risk analysis. The acidification of the Zn smelting slags to pH= 4 and 6 would result in the leaching concentrations of Cd and Mn exceeding the fourth–class standard of surface water quality standard in China (GB3838–2002). Notably, most metals exhibited an amphoteric leaching pattern, where the highest leached concentrations of As, Cd, Cu, Mn, Pb, and Zn were 4.15, 4.21, 140.0, 78.1, 156.9 and 477.0 mg/L, respectively. In addition, the highest release of toxic metals within 96 h reached 0.17 % of As, 3.50 % of Cd, 2.77 % of Cu, 6.92 % of Mn, 0.13 % of Pb, and 2.57 % of Zn, respectively. The combined results of various characterization techniques suggested that the PTEs remobilization effected by rhizosphere–like organic acids were mainly controlled by the precipitation of newly formed Fe, Mn and Al (hydr) oxides and the complexation of organic ligands. The present study results could provide valuable insights into the long–term leaching behaviors of PTEs from the Zn smelting slags to reduce ecological hazard.

Evaluation of heavy metal availability in soils near former zinc smelters by chemical extractions and geochemical modelling

Multi-surface modelling (MSM) is an important tool to predict heavy metal partitioning and speciation in soils. However, calcareous clay soils contaminated by smelting activities and mine waste have so far received little attention in MSM studies. In this work, 6 paired soil samples taken nearby former Zn smelters and at further distance were used for quantifying the essential input parameters for MSM including the size of the geochemically reactive pool of heavy metals and the reactivity of soil organic matter (SOM) for metal binding. The reactive heavy metal pool (Cd, Cu, Ni, Pb, and Zn) in these samples was determined by extracting soil with 0.43 M HNO3 and 0.005 M DTPA. For both extraction methods, the contribution of all heavy metals to their total contents was larger in most of the soil samples taken nearby former Zn smelters than in the paired samples from further distance. Furthermore, the amounts of heavy metals extracted with 0.43 M HNO3 were consistently larger than those extracted with 0.005 M DTPA. The sum of the humic acid (HA), fulvic acid (FA) + hydrophobic organic neutral (HON) fraction varied between 6.2 and 43% of total SOM with an average of 24%, which is at the lower end of what is commonly reported in literature. The lower SOM reactivity might be attributed to a lower humification rate of fresh soil organic matter due to heavy metal contamination. The accuracy of the MSM-predicted predictions of solubility of the heavy metals, especially for Ni and Zn, was higher when the results of the DTPA extraction method were used as model input, than when using the results of the HNO3 extraction method, especially when the soil carbonate content was > 4%. Hence, the measurement of the geochemical reactivity of heavy metals by the 0.005 M DTPA extraction method and the reactivity of SOM enable adequate MSM predictions of the solubility of heavy metals in smelter slag-contaminated calcareous clay soils.

Comprehensive Recycling Technology of Waste Residues in Zinc Hydrometallurgy

In order to improve the refining effect of zinc ore and promote the development of this industry, taking the hydrometallurgical zinc smelting process as an example, this paper first establishes a model for the recycling of waste residues in the hydrometallurgical process, proposes optimization measures based on proven comprehensive recycling technology for purifying residues to obtain higher valuable metal recovery rate, and provides reference for those in relevant fields.

Characteristics of soil pollution and element migration associated with the use of coal in Hutou Village, Yunnan Province, China

This study aimed to reveal the status and source apportionment of trace element soil pollution in a village with a relatively high incidence of lung cancer in China and determine the element migration characteristics from coal to road dust and soil. To this end, 24 soil samples, 48 road dust samples (from a previous study), and 2 coal samples were collected; major element oxides, V, Cr, Co, Ni, Cu, Zn, Zr, Cd, and rare earth elements were analyzed; minerals were identified by SEM-EDX and XRD; a geoaccumulation index (Igeo), Spearman’s correlation analysis, provenance index (PI) and positive matrix factorization (PMF) were carried out to assess the status and source apportionment of soil pollution; and mineralogical and geochemical methods were used for provenance discrimination and migration characteristics identification. The results demonstrated that (1) the Cd and Cr pollution of the soil was severe and originated mainly from indigenous zinc smelting, agricultural activities, and the use of coal. (2) The pollution migrated from Yantang coal to the road dust to the soil through mineralogical and geochemical methods. (3) A stronger fractionation of light and heavy rare earth elements was observed in the soil than in the road dust, indicating a single pollution source in the road dust and a complex source in the soil. (4) The primary reason for the lower rare earth element values in the road dust could be physical separation by the wind.

Discovery of significant atmospheric emission of halogenated polycyclic aromatic hydrocarbons from secondary zinc smelting

Chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/Br-PAHs) are emerging persistent organic pollutants. Current knowledge on the emissions of Cl/Br- PAHs is far insufficient for source control, much less on their formation mechanisms. In this field study, Cl/Br-PAHs formation mechanisms were proposed from the macro perspective of practical secondary metal smelting industries. We found secondary zinc smelting as a significant source of Cl/Br-PAHs (9553 ng/m3 in stack gas), exceeding concentrations from other metal smelting sources by 1–2 orders of magnitude. Cl/Br-PAH emission characteristics differed between various secondary metal smelting processes, indicating dominance of different formation mechanisms. Cl/Br-PAHs with fewer rings were dominant from secondary zinc smelting and secondary copper smelting. Differently, emissions from secondary aluminum smelting were dominated by congeners with more rings. The differences in congener profiles were attributable to the catalytic effects of metal compounds during smelting activities. Zinc oxide and copper oxide dominantly catalyzed dehydrogenation reactions, contributing to the formation of intermediate radicals and subsequent dimerization to Cl/Br-PAHs with fewer rings. Differently, aluminum oxide induced alkylation reactions and accelerated ring growth, resulting in the formation of Cl-PAHs with more rings. The newly proposed mechanisms can successfully explain the emission characteristics of Cl/Br-PAHs during smelting activities, which should be important implication for Cl/Br-PAHs targeted source control.

Cancer mortality and chemical exposure in a retrospective zinc and lead smelter cohort: A 48-year follow-up.

Very few studies to date have investigated cancer mortality in non-ferrous metal smelters. Existing studies mainly focus on lead exposure and have reported inconsistent results. The aim of this study was to investigate the risk of excess cancer mortality in the employees of a lead and zinc smelter located in the north of France by 1) comparing mortality in this cohort of employees with that of the regional population; 2) studying the associations between occupational exposure and cancer deaths. The study cohort was composed of male workers, born in France, who had been employed by the company in question for at least 365 consecutive days. A company-specific job-exposure matrix was produced in order to calculate a cumulative exposure index for 15 toxic agents. Deaths of smelter employees which occurred between January 1, 1968 and December 31, 2015 were compared to those in the regional population (standardized mortality ratio, SMR). The relationships between the cumulative exposure indexes and mortality by cancer site were studied using Cox regression models with age and the 20-year lagged cumulative exposure index as time-dependent variables. Vital status was found for 2177 of the employees in the cohort (98%). Median follow-up was 34.8 years (interquartile interval=24.3-44.8), totaling 74,437 person-years. Compared to the regional population, no excess risk of all-cause mortality (n=913, SMR=0.96, 95%CI:0.90-1.02), nor of cancer mortality (n=338, SMR=0.97, 95%CI:0.87-1.08) was found. An overall significant excess risk of cancer mortality was found for employees who worked in this non-ferrous metal smelter for a period of between 15 and 29 years (n=139, SMR=1.23, 95%CI:1.04-1.45). Asbestos exposure was found to be associated with an increased risk of mortality for all cancer sites (p=0.0012), lip-oral cavity-pharynx malignant neoplasms (MN) (p=0.0141) and trachea-bronchus-lung MN (p=0.0018); lead exposure was associated with the same risk for lip-oral cavity-pharynx (p=0.0378) and liver MN (p=0.0155); aromatic amine exposure with bladder MN (p=0.0002); chromium exposure with colon-rectum-anus MN (p=0.0057) and colon MN (p=0.0315); bismuth exposure with rectal MN (0.0011) and sodium hydroxide vapor exposure with laryngeal MN (0.0150). Including occupational exposure to numerous toxic agents other than lead in this study of smelter mortality has made it possible to identify associations between different toxic agents and cancers, opening up new avenues for future research.