Lead-zinc Tailings Research Articles

Comprehensive Recovery of Valuable Metals from Lead-zinc Tailings by Flotation

This study takes lead-zinc flotation tailings as the research object. The process of “tailings regrinding-lead-zinc mixed floatation-activation zinc separation” is used to comprehensively recover valuable metal elements from the original tailings. The results show that the grinding fineness is -74 μm under the condition that m accounts for 82%; the recovery rates of lead and zinc in the lead-zinc mixed concentrate obtained from the open-circuit test are 36.4% and 18.0%, respectively; the recovery rate of zinc in the coarse zinc concentrate is 57.6%; the valuable metal elements in the original tailings are effectively recovered.

Heavy Metal Concentrations and Accumulation Characteristics of Dominant Woody Plants in Iron and Lead−Zinc Tailing Areas in Jiangxi, Southeast China

Phytoremediation using woody plants can effectively reduce heavy metal (HM) concentrations in soils. However, the remediation capacity of woody plants depends greatly on plant species and soil environmental conditions. In order to evaluate the HM remediation potential of woody plants from different tailing areas, the HM accumulation characteristics of roots, shoots, and leaves of 12 dominant native woody plants growing in iron and lead-zinc tailing areas were analyzed. The results showed that the concentrations of Cd, As, Ni, Mn, and Cr in most plants in the two tailing areas exceeded the level of normal plants. The distribution of different elements in plants was generally as follows: root > leaf > shoot for Pb and As; root > shoot > leaf for Cr; and leaf > shoot > root for Zn, Ni, and Mn. The distribution of Cu and Cd in plants varied with the type of HM pollution in the two tailing areas. There were significant (p < 0.05) negative correlations between available phosphorus in the soil and Pb, Cd, and Zn in the plant roots when the soil was heavily polluted with Pb, Cd, and As; similarly, there were significant (p < 0.01) negative correlations between readily available potassium in the soil and Pb, Zn, and Ni in plant roots. Based on the higher than average concentration of HMs in plants, and higher bioconcentration factors and translocation factors, some plants were considered woody plant species with phytoremediation. Slash pine (Pinus elliottii) and indian azalea (Rhododendron simsii) had strong enrichment and translocation abilities for Cd, oriental white oak (Quercus glauca) and beautiful sweetgum (Liquidambar formosana) for Mn and paulownia (Paulownia fortunei) for Zn. The plants listed above can be used as potential species for phytoremediation in iron and lead-zinc tailing areas.

Organic-inorganic composite modifiers enhance restoration potential of Nerium oleander L. to lead-zinc tailing: application of phytoremediation.

Lead-zinc tailings are complex heavy metal solid wastes produced in the mining process. In this study, two kinds of organic-inorganic mixed improvers mushroom residue + calcium carbonate (M + C) and peat soil + calcium carbonate (N + C) were selected. Then, the effect of two improvers and a woody plant, Nerium oleander L., on the combined remediation of lead-zinc tailings was compared, respectively. The results showed that two combined improvers can slightly improve the pH of tailing, significantly increase the activity of phosphatase and catalase, effectively reduce the contents of DTPA-extractable Pb and Zn, and significantly improve the structure of tailing. However, the improvement effect of M + C was better than that of N + C on tailings' physical and chemical properties. Two improvers can reduce the enrichment and the stress degree of Pb and Zn on the N. oleander and increase the accumulation of Pb and Zn while promoting the growth of the N. oleander. The content of Pb and Zn showed the trend of root > stem > leaf under the two improvers, and the content of Zn was basically higher than that of Pb. To sum up, the combination of two modifiers and N. oleander has a good effect on the remediation of lead-zinc tailings, and the remediation effect of M + C was better than N + C.

Solidification Experiment of Lithium-Slag and Fine-Tailings Based Geopolymers

Based on the pressure of environmental protection, more and more scientific researchers are trying to reuse aluminum–silicon-rich industrial wastes. In this study, activated lithium-slag and lead–zinc tailings were used as raw materials to prepare geopolymers at ratios of 3:7, 1:1, and 7:3. These geopolymers were initially cured for 12 h at 25 °C, 50 °C, 75 °C, and 100 °C and were then cured at room temperature to the specified ages. The compressive strength of each group of geopolymers was tested at the ages of 3 days, 7 days, and 28 days. The optimal group of samples was selected, that is, those with a ratio of lithium-slag to lead–zinc tailings of 7:3 and an initial curing temperature of 75 °C. After that, the heavy metal leaching test and porosity analysis test were carried out on the optimal group of samples, and the curing effect was considered to meet the requirements of the Chinese specifications. In addition, in order to reveal the mechanism of the chemical reaction, scanning electron microscopy and X-ray diffraction (XRD) were used to study the microstructure and hydration products of the C3 group cured samples. This study provides a new concept for the reuse of industrial wastes such as lithium-slag and fine-tailings.

Study on preparation of glass-ceramics from municipal solid waste incineration (MSWI) fly ash and chromium slag

In order to realize the harmless treatment of municipal solid waste incineration (MSWI) fly ash and chromium slag, the CaO–SiO2–Al2O3 glass-ceramics were successfully prepared by the one-step method using a mixture of lead-zinc tailings and coal gangue as a flux. The results showed that the mixture successfully reduced the melting temperature of MSWI fly ash with a maximum blending ratio of 70% at 1450 °C, and realized the co-sintering of chromium slag and the base glass of MSWI fly ash. In addition, according to the analysis results of XRD, SEM, and EDS, combined with heavy metal leaching data measured by the TCLP method, diopside ferrous crystals exerted a better solidification effect on Zn and Cd than did gehlenite crystals. Uvarovite crystals exhibited an effective solidification effect on Cr owing to the participation of Cr in its formation, and the toxicity assessment of heavy metals in all samples satisfied the demand of the EPA and the CN GB 5058.3. This work provides a consult for the low-cost, green and efficient treatment of chromium slag, MSWI fly ash, coal gangue, and lead-zinc tailings.

Experimental study on solidification and remediation of lead–zinc tailings based on microbially induced calcium carbonate precipitation (MICP)

With the development of industry, the human demand for lead and zinc is increasing gradually, and the heavy metal pollution caused by the mining process of lead–zinc tailings is becoming more and more serious. To alleviate the pollution problem, microbially induced calcium carbonate precipitation (MICP) technology has been used to solidify and remedy lead–zinc tailings containing heavy metals based on the multi-shell curing method. Based on unconfined compression strength (UCS) and the parameters of heavy metal ions leaching concentration, exploring the addition of lead–zinc tailings on the impact of microbially induced calcium carbonate precipitation on solidifying and repairing lead–zinc tailings, using SEM, XRD, FTIR, EDS and XPS tests, and revealing the mechanism of MICP to solidify lead–zinc tailings. The results of the experiment showed that MICP had a good solidifying and repairing effect on heavy metals in lead–zinc tailings. When the thickness of lead–zinc tailings was 2 cm, the unconfined compression strength of the specimen was the maximum up to 0.93 MPa and the calcium carbonate content was up to 7.41 %. At the same time, Fe3+, Zn2+, Pb2+, Cu2+ and Cd2+ in the leaching solution could be completely removed, and the removal of Mn2+ and Cr3+was up to 98.24 % and 95.56 % respectively, which was the best condition for solidification. The samples of lead–zinc tailings being solidified and repaired based on MICP showed that calcium carbonate was primarily precipitated as the commonly crystal forms of aragonite, calcite, and vaterite, with strong cohesiveness, which made lead–zinc tailings particles connected together. At the same time, the CO32– and alkaline substances produced by microbial metabolism made the heavy metal ions released by the lead–zinc tailings mainly precipitate in the form of metal carbonate, which reduced the pollution to the environment. This technology provides a new method for solidifying and repairing lead–zinc tailings.

Mechanical properties of one-part geopolymer masonry mortar using alkali-fused lead–zinc tailings

Currently, various industrial wastes such as tailings and smelting slag are recycled as raw materials in the field of construction. Tailings such as lead–zinc tailings (LZTs) are generally low-reactivity materials. In this study, LZTs were activated through alkali fusion and combined with slag to synthesize a one-part geopolymer. The optimal preparation process, including calcination temperature, alkali consumption, dwell time, and slag content, was determined using response surface methodology (RSM). Subsequently, the optimal geopolymer sample was used to produce a masonry mortar. Influences of the binder–sand ratio and water-reducing admixtures, including polycarboxylate, naphthalene, and sulfonation melamine, on the properties of the mortars were investigated. Based on the results, the geopolymer paste samples produced by activated LZTs (with 20 % alkali added and calcined at 568 °C for 83 min) and 60 % slag content exhibit the optimal compressive strength of 47.2 MPa. Moreover, with a decrease in the binder–sand ratio, the water/binder content required to achieve similar consistency increased continuously; thus, the 28-d compressive strength of the mortar samples reduced significantly from 34.0 to 12.8 MPa. Owing to the incorporated three admixtures, the consistency and 28-d compressive strength of mortar samples were significantly improved; in particular, sulfonation melamine was found to increase these factors by up to 61 % and 95 %, respectively.

Preparation and characterization of glass ceramics synthesized from lead slag and lead-zinc tailings

Using lead slag and lead-zinc tailings to prepare high-value glass-ceramic can realize the comprehensive utilization of solid waste and reduce the environmental pollution caused by lead slag landfill. Firstly, lead-zinc tailings and borax are used to melt and temper lead slag to improve its sintering performance. At 1450 °C, the lead slag melted and tempered by adding 40% lead-zinc tailings and 4% borax has good fluidity in the molten state. In water quenching, crystallization is not easy, and the water quenching slag has good sintering performance. Then, the water-quenched slag obtained by melting and tempering lead slag with lead-zinc tailings and borax was ball-milled and mixed with 10% albite feldspar and sintered at 1050 °C for 90 min to prepare glass ceramics. The prepared glass-ceramics have excellent performance parameters such as bulk density of 2.79 g/cm3, water absorption of 0.05%, the flexural strength of 102.18 MPa, acid resistance of 0.15%, and alkali resistance of 0.032%. Simultaneously, the glass ceramics exhibited excellent resistance to the leaching of heavy metals where the leaching concentrations of Pb, Zn, As, and Cd were 0.125, 1.268, 0.324, and 0.029 mg/L, respectively. This research can provide a new idea for comprehensively utilizing solid waste.

Preparation of ceramsite from lead-zinc tailings and coal gangue: Physical properties and solidification of heavy metals

Lead-zinc tailings (LZT) are hazardous solid wastes that threaten the environment safety and human health. As a bulk solid waste, coal gangue (CG) also caused pollution. This paper studied the feasibility of using a combination of LZT and CG to produce ceramsite and realizing the solidification of heavy metals. The physical properties of ceramsite were evaluated, and the phase composition and microstructure were analyzed by XRD and SEM-EDS, respectively. The results showed that when the LZT content was <30 wt%, LZT and CG could be used for the preparation of ceramsite, and the prepared ceramsite met the requirements of environmental safety. Proportion of raw materials and sintering temperature affected physical properties of ceramsite. With the increase of LZT content, the apparent density, and the compressive strength of ceramsite first decreased and then increased. The increase of sintering temperature from 1150 °C to 1250 °C reduced the apparent density and the compressive strength of ceramsite. Moreover, the presence of Pb and Zn decreased the apparent density, the compressive strength, and the water absorption of the ceramsite. The valence of Pb and Zn remained as Pb2+ and Zn2+ after the ceramsite sintering. The solidification of ceramsite could be related to chemical effect through the generation of crystals (e.g., Pb3(AsO4)2 and ZnFe2O4) and physical effect though encapsulation. This work provides a potential way to the reduction, recycling, and harmless utilization of LZT and CG.

Research Status and Prospects for the Utilization of Lead–Zinc Tailings as Building Materials

Lead–zinc tailings are the typical solid wastes in mines with high yield and low utilization rates in some countries at present. They are mainly stockpiled in tailings reservoirs, occupying massive land resources and threatening the health of the environment. One of the advantages of building material production in sustainability is the ability to utilize large amounts of industrial solid wastes, and the use of lead–zinc tailings in building materials is an effective way to meet the dual needs of environmental protection and economic development. This paper reviews the progress of utilizing lead–zinc tailings as building materials and mainly summarizes the status of lead–zinc tailings in cement, geopolymer, concrete, building brick, and foam ceramic. According to previous research, lead–zinc tailings contain large amounts of silica–alumina oxide, which can be used in the production of cement clinker. The addition of lead–zinc tailings to the sintered material can reduce the sintering temperature. The active components contained in lead–zinc tailings can be used in concrete instead of cement or in the preparation of geopolymers. Meanwhile, lead–zinc tailings can also be used as a fine aggregate. However, there are few studies on the durability of building materials with lead–zinc tailings. Additionally, most of the research results of building materials are in the laboratory stage, which are difficult to be promoted. In view of these problems, corresponding suggestions and prospects are given in the end in order to provide a reference for the research on the utilization of lead–zinc tailings.

Temporal Variations of Sediment Provenance in a Karst Watershed, China

The environmental quality of the sediments in karst areas is a common concern, and it is of great significance to analyze the sources of the sediments. This study investigates the sources and its temporal variations of catchment sediments in a typical small karst watershed area. Toxic metal concentrations in the catchment area were monitored via three geochemical baseline projects in China. The sediment identification fingerprint tool (SIFT) was used to establish a geochemical model for tracing the main source contributions and its temporal variations of catchment sediments over the past 28 years (1992–2019). The catchment sediments in the small karst catchment area were mainly sourced from the background lithologies, among which limestone contributed the most, followed by dolomite, sand-shale, and mudstone; however, the anthropogenic lead–zinc tailings contributed the least. The contributions and temporal variations of each source were closely related to the lithology, topography, and landform, as well as the change in land-use and vegetation cover and the degree of rocky desertification. Moreover, the implementation of vegetation restoration and control of rocky desertification decreased the contributions of the upstream geological bodies, and the toxic metal content of the catchment sediment decreased accordingly. This study is of great significance for environmental governance in karst areas.

Enrichment and Recovery of Lead-Zinc Tailings by Spiral Wall Cyclones

In order to solve the problem of increasing the difficulty of sorting lead-zinc tailings in China, the re-separation of lead-zinc tailings is realized, the recovery efficiency is improved, and the sorting cost is reduced. Through the structural improvement of the traditional column conical cyclone, a spiral wall cyclone suitable for secondary sorting of lead-zinc tailings is proposed, and the lead-zinc tailings with different density are quickly separated by using the diversion of the spiral wall and the enrichment of mineral particles. The results showed that the recovery rate of heavy concentrate PbO increased from 55.55% to 85.25% by the spiral wall cyclone after structural optimization, an increase of nearly 30%, and the enrichment ratio of down-export PbO concentrate also increased from 1.321 to 1.762. It can be seen that the optimized spiral wall cyclone can effectively increase the secondary sorting efficiency of lead-zinc tailings, and provide a reference for the structural design of hydraulic cyclones in the same type of mine to a certain extent.

Analysis of Influencing Factors of Cementitious Material Properties of Lead-Zinc Tailings Based on Orthogonal Tests.

At present, the treatment of tailings is mostly carried out in the form of stacking in tailings ponds, resulting in a huge waste of mineral resources and a major threat to the environment and ecology. Using tailings instead of a part of the cement to make cementitious materials is an effective way to reduce the accumulation of tailings. In this paper, lead-zinc tailings-based cementitious materials were prepared by using lead-zinc tailings, fly ash, and ordinary Portland cement, and the effects of four factors on the mechanical properties of lead-zinc tailings, as well as fly ash content, cement content, and water-binder ratio were studied by orthogonal experiments. The corresponding relationship between the factors and the properties of cementitious materials was determined, and the optimization and prediction of the raw material ratio of lead-zinc tailings-based cementitious materials were realized. The test showed the ratio of raw materials to be at the lowest price ratio. Synchronously the ratio that meets the minimum strength requirements was predicted. When the proportion of fly ash:lead and zinc tailings:cement = 30:40:30 and the water-binder ratio was 0.4, the predicted compressive strength of the prepared cementitious material achieved 22.281 MPa, which meets the strength requirements, while the total content of lead-zinc tailings and fly ash was the highest at this time.

Effects of Basalt Fiber on Strength of Alkali-Activated Slag-Tailing Cement Bodies

The influences of different quantity of basalt fiber and lead–zinc tailings on the strength of alkali-activated slag-tailings cement bodies were studied. After adding basalt fiber, the uniaxial compressive strength of the 50 and 60 g per unit tailing cement bodies increased before decreasing throughout a 7-day curing period. During a 28-day curing period, the uniaxial compressive strength of the 50 g per unit tailings cement decreased gradually, while the uniaxial compressive strength of the 60 g per unit tailings cement increased first and then decreased. Furthermore, after adding basalt fiber, the flexural strength of the 50 g per unit tailings cement body decreased gradually during a 7-day curing period, while the 60 g per unit tailings cement increased first and then decreased. Under a 28-day curing period, the flexural strength decreased first and then increased for both cement bodies. Finally, At the confining pressures of 2, 4 and 6 Mpa, the increase amplitude of the triaxial compressive strength of the cementation body was different with the addition of basalt fiber. The increase amplitude of the triaxial confining pressure from 2 to 4 Mpa was higher than that of the triaxial compression from 4 to 6 Mpa.

The following articles for this Special Issue were published in different Issues

Abstract T. Gao, X. Wang,Y. Liu, H. Wang, M. Zuo, Y. He, H. Li, G. Li, C. Li, X. Li, X. Li, Y. Yang. Characteristics and diversity of microbial communities in lead–zinc tailings under heavy metal stress in north-west China. 2022;74(2):277-287. https://doi.org/10.1111/lam.13608 https://onlinelibrary.wiley.com/doi/10.1111/lam.13608 R. Parada, L. Mendoza, M. Cotoras, C. Ortiz. Endophytic fungi isolated from plants present in a mine tailing facility show a differential growth response to lead. 2022;75(2):345-354. https://doi.org/10.1111/lam.13730 https://onlinelibrary.wiley.com/doi/10.1111/lam.13730

Influence on fine lead–zinc tailings solidified/stabilised by clinker-free slag-based binder

This study applied steel slag (SS), blast furnace slag (BFS), flue gas desulfurised (FGD) gypsum and fly ash (FA) as clinker-free cementitious materials for fine lead–zinc tailing (LZT) backfillings and investigated the mechanism of Pb and Zn immobilisation in tailings. In a binder with 42%, 42% and 16% of SS, BFS and FGD gypsum, respectively, the binder-to-tailings ratio was 1:4. Additionally, the slurry concentration was 78%, resulting in unconfined compressive strength values of 0.89, 6.47 and 11.03 MPa after 7, 28 and 56 d, respectively, and fluidity of 230 mm. After 56 d of curing, the leaching concentration of Pb and Zn became 0.34 and 0.63 μg/L, respectively, and the immobilisation efficiency and the bioavailability reduction efficiency of Pb and Zn were 99% and 90%, respectively, which are lower than the underground class III water standard. Additionally, the double salt effect was a crucial reason for the excellent immobilisation properties of Pb and Zn. Micro-analysis indicated that anglesite, minrecordite and Pb[Fe3(SO4)2(OH)6]2 formed during the hydration process with their solubility products (Ksp) at 1.622 × 10−8, 1 × 10−20 to 1 × 10−16 and 1 × 10−25.5 at 25 °C. Furthermore, the residues of Pb and Zn in the morphological analysis increased from 29% and 37% (the original) to 65% and 67% (curing 56 d), corresponding to the increasing binding energy and content of Zn–O and Pb–O. Moreover, calcium–silicate–hydrate gel and ettringite appeared in the solidified samples, with a high degree of cementation, as the hydration age increased.

Study on low-cost preparation of glass–ceramic from municipal solid waste incineration (MSWI) fly ash and lead–zinc tailings

Municipal solid waste incineration (MSWI) fly ash and lead–zinc tailings contain heavy metals and are detrimental to the environment. However, conventional melt disposal requires high temperatures, resulting in high costs. This study used coal gangue as a flux to reduce the melting temperature, and the one-step process successfully prepared the CaO-SiO2-Al2O3 series glass-ceramics. The results show that the solidification effect of diopside ferrous crystals on heavy metals is higher than that of anorthite and gehlenite, and the leaching concentration of heavy metals conforms to the U.S. Environmental Protection Agency and the Chinese National (GB 5058.3) standard limits. This study provides a reference for the efficient, green, low-cost treatment of MSWI fly ash, lead–zinc tailings, and coal gangue.

Mitigation effect of accelerators on the lead–zinc tailing induced retardation in autoclaved concrete

• Na 2 CO 3 significantly shortens the induction period of lead–zinc tailing cement pastes. • Na 2 CO 3 promotes the alkali activation of SiO 2 in tailing under autoclave curing. • No apparent coating of zinc containing compounds can be seen on C 3 S surface. • Accelerators inhibit the retardation by promoting the dissolution of cement particles. Reutilization of lead–zinc tailing in autoclaved concrete greatly reduces the land pollution by the wastes and CO 2 emission by the cement production. Given the retardation of lead and zinc on the cement hydration, three kinds of accelerators, Na 2 CO 3 , Li 2 CO 3 and triethanolamine (TEA) were employed. In this paper, the effect of accelerators on the autoclaved lead–zinc tailing blended cement mortars was investigated from aspects of compressive strength, hydration heat, phase assemblages and leachability of cement mortar. Results show that when the dosage of lead–zinc tailing exceeds 20 %, the demolding strength and the autoclaved strength of cement mortar decrease with increasing tailing dosage. Compared with Li 2 CO 3 and TEA, Na 2 CO 3 shows a more effective accelerating impact on the cement hydration. Incorporating 0.5 % Na 2 CO 3 can shorten the induction period of the lead–zinc tailing cement pastes by 20 h. Additionally, the SiO 2 in lead–zinc tailing can react with cement under autoclave curing, and the reaction is obviously promoted by the incorporation of Na 2 CO 3 . It lies in that Na 2 CO 3 and Li 2 CO 3 inhibit the retardation of lead–zinc tailing by promoting the dissolution of cement and nucleation of hydrates.

Preparation of high-purity vaterite CaCO3 from lead-zinc tailings

This study introduced a green scheme for high value treatment of lead-zinc tailings, which produced high-purity vaterite from lead-zinc tailings. The effects of different experimental parameters on the leaching and carbonization of Ca2+ in lead-zinc tailings were discussed. It was found that the optimum leaching ratio of Ca2+ in NH4Cl solution was 74.87% and the optimum carbonization ratio of Ca2+ in the leaching solution was 96.96%. The spherical CaCO3 with d50 < 10 μm, 99.41% purity, and 98.70% whiteness was prepared under suitable carbonization conditions. The XRD results showed that the CaCO3 product was high purity vaterite. The presence of NH4+ and Zn2+ in the leaching solution hindered the transformation of vaterite into calcite, leading to the formation of high-purity vaterite CaCO3. The SEM results indicated that the dispersants STP or PEG-6000 could improve the dispersion of vaterite, and STP contributed to the formation of fine particle vaterite. This method proposed an approach for the production of vaterite from lead-zinc tailings, broad application prospects.

Ecological evolution during the three-year restoration using rhizosphere soil cover method at a Lead-Zinc tailing pond in Karst areas

A major challenge for the restoration of the Lead-Zinc tailing pond in Karst areas lies in how to establish vegetation with less soil and restore the ecological functions of the substrate. In this study, a novel method, rhizosphere soil cover method (RSC), was applied to recover the vegetation at a Pb-Zn tailing pond in Karst areas. Two local tolerate plants, Miscanthus sinensis and Pueraria phaseoloides, were planted as pioneer species. Although 68 % of the tailing pond was not covered with soil, the vegetation coverage has reached over 90 % after restoration for three years. Compared with the natural revegetation process (vegetation coverage was <5 % after 20 years of natural succession), the revegetation in the tailing pond was accelerated by RSC and planting pioneer species. Both the plant's diversity and richness have significantly increased in the tailings pond during the restoration (p < 0.05). The important value indicators of M. sinensis and P. phaseoloides were the highest in the plant community, indicating the dominant role of these two plants in revegetation. Moreover, the total organic carbon, total nitrogen, total phosphorus, and total potassium in the tailings increased annually (p < 0.05), which demonstrated that the revegetation has improved the chemical properties in the substrate. In addition, the Shannon diversity index of bacteria in the tailings increased significantly from 4.11 to 5.51. The relative abundance of microbial genes related to carbon fixation and nitrogen fixation in the tailings increased by 17 % and 43 %, respectively. Meanwhile, the physicochemical properties, microbial community structure, and nutrient cycling function in the tailings without topsoil were improved more obviously than those in soils. It is thereby concluded that RSC is an efficient means for ecological restoration of the tailing ponds in Karst areas to improve the ecosystem structure and function of Pb-Zn tailings.