Lead-zinc Tailings Research Articles

Impact of Acid Rain on Release Characteristics of Heavy Metals in Low-Sulfur Tailings with Strong Acid Neutralization Capacity: A Case Study from Northern Guangxi, China

Tailing ponds are major sources of heavy metal pollution. Previous studies primarily focused on tailings with high sulfur content, with limited attention to low-sulfur tailings. This study explored the release behavior of Pb, Zn, and Cd from low-sulfur tailings under simulated acid rain conditions, considering factors such as pH, particle size, and weathering degree. Samples were collected from a lead–zinc tailing pond in the karst regions of northern Guangxi, China. Batch leaching experiments indicated that even with high acid neutralization capacity (ANC = 166.57–167.45 kg H2SO4/t), substantial heavy metal leaching occurred under acidic conditions (pH 2–3), with Pb, Zn, and Cd concentrations increasing 4–6 times compared to neutral conditions. Leachate concentrations were slightly higher in coarser particles than in finer ones, while weathering further enhanced metal release, particularly for Cd. These findings suggest that acid neutralization alone may not be sufficient to prevent heavy metal leaching in low-sulfur tailings exposed to acid rain. However, due to the laboratory scale of this study, further validation through field-scale or mesocosm experiments is necessary to confirm the observed trends and assess their implications for environmental risk management in karst regions.

Passivation of metal sulfides by a marine bacterium for acid mine drainage control

Acid mine drainage originates from metal sulfides oxidation, which results in acidic metal-rich leachate. In this study, a novel and environmentally friendly approach was demonstrated to passivate pyrite and lead-zinc tailings, respectively. The key to this approach is to develop biofilms of the marine bacterium Qipengyuania flava S1. Biofilms can induce biomineralization, thereby isolating metal sulfides from air and water. The stability and biological toxicity of the bio-passivation layers were evaluated by leaching bio-passivated pyrite or tailings in initially acidic H2O2 solutions with shaking for 180 days and then cultivating Brassica chinensis and Allium cepa with the leachates. Our results showed that after passivation, the amount of iron released by pyrite decreased by at least 99.2 ± 0.2 (in wt%). For lead-zinc tailings after passivation, the released metal ions (Fe+Al+Pb+Zn) decreased by at least 52.0 ± 3.2 (in wt%). The bio-passivation layers also maintained the pH of the leachate in the range of 7.5–8.0. Before bio-passivation, compared with mineral water, the pyrite leachate significantly inhibited the growth of the two plants, and the tailings leachate significantly inhibited the growth of A. cepa, whereas the bio-passivated pyrite or tailings leachate did not show any inhibitory effect.

Effects of active silicon amendment on Pb(II)/Cd(II) adsorption: Performance evaluation and mechanism

In this study, a high-Si (Si) adsorbent (APR@Sam) was prepared by acid leaching slag (APR) from lead-zinc (Pb-Zn) tailings based on high-temperature alkali melting technology. The synthesized Si-based materials were applied to aqueous solutions contaminated with Pb and cadmium (Cd) to investigate the crucial role of active Si in sequestering heavy metals. The adsorption capacities of APR@Sam and the Si-depleted material (APR@Sam-NSi) were studied under different pH and temperature conditions. The results showed that as the pH increased from 3 to 7, the adsorption capacity increased, the active Si content in the solution increased by 63 %, and the maximum pH of the solution after adsorption was 7.12. After the removal of active Si, the Pb (II) and Cd (II) adsorption capacities of APR@Sam decreased by 45 % and 11.96 %, respectively. OH- promoted the release of Si into the solution, enhancing the material's adsorption efficiency. The reaction mechanism is mainly attributed to surface complexation guided by Si-O and Si-O-Si bonds, metal cation exchange, and bidentate coordination. The results indicated that the Si component is critical for the removal of Pb (II) and Cd (II) by APR@Sam and provide valuable insights into resource recovery strategies from leaching residues.

Comparative study on the effect of SRB and Sporosarcina pasteurii on the MICP cementation and solidification of lead–zinc tailings

The production of tailings sand due to mining and smelting activities is one of the reasons for the accelerated environmental pollution caused by heavy metals, drawing social attention to the management of tailings sand. Microbially induced carbonate precipitation (MICP) is an environmentally friendly soil remediation technique that is gradually becoming the preferred method for soil stabilisation and heavy metal pollution control. To address the issues of heavy metal pollution release and the loose particle structure of lead–zinc tailings sand (LZTS), this study employs a layered MICP approach. The solidification effects of two typical mineralising bacteria, sulfate-reducing bacteria (SRB) and Sporosarcina pasteurii, on LZTS, were compared for the first time. The results show that the maximum unconfined compressive strength (UCS) of SRB cemented solidified lead–zinc tailings sand (SRB-CS-LZTS) specimens is 0.22 MPa, while that of S. pasteurii cemented solidified lead–zinc tailings sand (SP-CS-LZTS) specimens is 0.95 MPa. Compared with the UCS of SRB-CS-LZTS, the UCS of SP-CS-LZTS increased by 3.32 times. The effect of S. pasteurii on the improvement of UCS and immobilisation of heavy metal ions was greater than that of SRB. The immobilisation effect of SRB on SO42- in the LZTS was better than that of S. pasteurii. Compared with SRB, the biological CaCO3 formed by S. pasteurii exhibited stronger adhesion and was more suitable for the cementation and solidification of LZTS. This study uses MICP technology to treat LZTS, aligning with the green environmental concept and providing a reference for the bioremediation of multiple heavy metals in tailing areas.

Optimization of Cementitious Material with Thermal-Activated Lead-Zinc Tailings Based on Response Surface Methodology.

The accumulation of lead-zinc tailings will cause a series of problems, including geological disasters and environmental pollution. Efficient secondary utilization of lead-zinc tailings is crucial. In this study, the activity of lead-zinc tailings was stimulated by thermal activation. The optimal thermal activation parameters are a thermal activation temperature of 900 °C and a holding time of 30 min. Based on the response surface methodology, the effect of raw materials content on cementitious material strength was analyzed, and the relational model between cementitious material strength and experimental variables was established. The results show that the sensitivity order of cementitious material strength at 28 days curing age is sand/cement ratio > water/cement ratio > fly ash content > tailing content. According to the relational model, the optimal materials ratio is as follows: tailing/fly ash/cement = 28.99%:14.58%:56.43%, and the sand/binder ratio and water/binder ratio are 1:1 and 0.47, respectively. The corresponding cost is CNY 290.965 per ton, which is the lowest. The strength of cementitious material with these parameters can reach 20 MPa, which meets the requirements of "Technical specification for application of solid waste cementitious material (T/CECS 689-2020)".

Fabrication of Lead-Zinc Tailings Sintered Brick and Its Effect Factors Based on an Orthogonal Experiment.

The existence of lead-zinc tailings threatens the social and ecological environment. The recycling of lead-zinc tailings is important for the all-round green transformation of economic society. In this study, the possibility of fabricating sintered ordinary bricks with lead-zinc tailings was studied based on orthogonal experimentation, and the phase composition and micromorphology of sintered products were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). With lead-zinc tailings as the main material, and clay and fly ash as additives, the effect of clay content, forming pressure, sintering temperature, and holding time on physical properties of sintered bricks was analyzed. The results show that clay content and sintering temperature have a major effect on compressive strength, while sintering temperature and holding time play an important role in water absorption. During sintering, mica, chlorite, and other components in lead-zinc tailings are decomposed to form albite, hematite, maghemite, and anhydrite, which play a role in the strength of bricks. The optimal process parameters were found to be a ratio of lead-zinc tailings:clay:fly ash = 6:3:1, forming pressure of 20 MPa, firing temperature of 1080 °C, and holding time of 60 min. The corresponding compressive strength and water absorption were 34.94 MPa and 16.02%, which meets the Chinese sintered ordinary bricks standard (GB/T 5101-2017).

Analysis of unconfined compressive strength and environmental impact of MICP-treated lead-zinc tailings sand instead of sand as embankment material

Tailings can be used as embankment materials instead of sand. However, they contain large amounts of heavy metal pollutants, which can lead to groundwater pollution. In this study, (lead-zinc) Pb-Zn tailings with five particle sizes and Sporosarcina pasteurii were used as test materials. Combined with the unconfined compressive strength (UCS) and leaching of heavy metal pollutants from Pb-Zn tailings, the feasibility of applying microbial induced carbonate precipitation (MICP)-treated Pb-Zn tailings to embankment materials was analysed from the perspective of strength and environmental performance. The results showed that the UCS and carbonate content of the specimens made of Pb-Zn tailings treated using MICP decreased with a decrease in the number of Pb-Zn tailing particles. The pH value of the leaching solution after MICP treatment of Pb-Zn tailings sand was stable at 7.83–8.03, and the fixation rate of metal ions was 90.28 %–100 %. FTIR, X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy tests showed that after the Pb-Zn tailings with particle sizes less than 100 mesh were treated using MICP, the number of carbonate crystals, crystal uniformity, and crystal overlap on the surface of the sample were considerably higher than those of the tailings with particle sizes greater than 250 mesh. The compressive strength and environmental performance of Pb-Zn tailings with particle sizes less than 100 mesh treated using MICP are good, and they are more suitable for embankment materials.

Lead immobilization in tailings–based alkali–activated materials

Our research explores the intricate mechanisms between lead (Pb) and alkali–activated materials (AAMs) derived from lead–zinc tailings. We delve into the lead immobilization process and its impact on material behavior. Our findings indicate that Pb2+ shortened the induction period and accelerated later hydration by offering additional nucleation sites. Notably, Pb2+ manifest a dual impact on the compressive strength of AAMs: a marginal increase at low concentrations (Pb2+ = 0.5%) and a decrease at higher ones (Pb2+ = 1.5%). Micro-analysis indicates that the hydrolysis of Pb2+ forms new materials that bridge larger pores within the AAMs matrix, resulting in reduced pore size. However, an excess of Pb2+ hampers gel polymerisation, impairing the gel’s structural integrity and the stability of immobilization. The interplay of these phenomena determines the overall strength of the material. Our leaching tests demonstrate that AAMs can effective immobilize Pb2+ at concentrations up to 1%, with a remarkable containment efficiency of 99.5% at 0.5% Pb2+. This is facilitated by several mechanisms, including the formation of insoluble precipitate, ion exchange with Na+/Ca2+, covalent bonding with Si, and physical encapsulation. These insights shed light on the promising applications of tailings–based AAMs for the effective immobilization of lead.

Effect of High Temperatures on Mechanical and Shielding Properties of Lead–Zinc Tailings Concrete for Radiation Protection

Due to the high prices, the popularity of radiation shielding concrete (RSC) has been greatly limited. To solve this, this research reused the lead–zinc tailings (LZT) as a fine aggregate replacement ranging from 0% to 60% for the RSC. The results revealed that the RSC containing 30% LZT presented better workability and achieved 95.84% of the compressive strength and 98.49% of the linear attenuation coefficient of the RSC, and reached the highest splitting tensile strength values, which increased by 4.43%. Meanwhile, after the heat treatments, there were favorable correlations between the relative velocity and relative strength, as well as between the damage index and the relative linear attenuation coefficient, which could accurately reflect the degradation of not only the mechanical but also the shielding properties. Considering the temperature and shielding thickness, the reuse of LZT can bring considerable economic and environmental benefits.

Using soil tuff-modified polymetallic lead–zinc tailings sand to facilitate sustainable development of subgrade engineering

The use of soil tuff, an industrial solid waste, for the modification of lead–zinc tailings as subgrade fillers presents a sustainable solution for concurrently addressing the negative impacts of tailings accumulation and resource depletion resulting from road construction. To demonstrate this, we conducted a thorough series of macroscopic and microscopic experiments, including the physical performance, durability, and microstructural behaviors of soil tuff-modified lead–zinc tailings sand (STM-LZTS) and cement-modified LZTS with varying modifier dosages, compaction degrees, and curing ages. Furthermore, we conducted a comprehensive comparison of the sustainability performance of these two modified LZTSs in terms of cost, CO2 emissions, and energy consumption. The results indicate that the incorporated 6% soil tuff filled the voids with the hydrated calcium silicate gel generated during the hydration process, which improved the structural stability. The CBR value was further enhanced to over 4% upon modification. With an increase in compaction degree to 96%, the CBR value escalated to over 8% (＞4%). The STM-LZTS specimens exhibited compressive strengths ranging from 0.818 to 0.958 (＞0.3 MPa). The variations in shear strength ranged between 200 and 550 kPa. Meanwhile, the modification of LZTS with soil tuff considerably delayed the deterioration of specimens under dry–wet, freeze–thaw, and salt-solution immersion conditions. Furthermore, compared with the cement-modified LZTS, the modified material formed a denser binder and a more robust nonparticle gel due to its lower calcium–silica ratio and higher aluminum–silica ratio, exhibiting superior performances in terms of compressive strength and resistance to salt corrosion. In addition, the use of soil tuff substantially reduced the cost, carbon emissions, and energy consumption, making it a promising and ecofriendly alternative for waste management and achieving carbon neutrality goals in subgrade engineering.

Experimental study on the stabilization and anti-seepage treatment of lead and zinc elements in heavy metal tailings pond using cement slurry containing heavy metal stabilizing agent

The release of heavy metal elements in heavy metal tailings ponds not only causes environmental pollution but also poses potential hazards to human health. Therefore, it is of great significance to stabilize heavy metals and apply anti-seepage treatment to tailings ponds. In this paper, the tailings in the Shenxiandong lead-zinc tailings pond in Yunnan Province, Southwest China, were analyzed. The adsorption effects of different natural stabilizing agents on lead (Pb) and zinc (Zn) in tailings were investigated. Orthogonal and modification experiments were used to identify the most effective stabilizing agent. This agent was then combined with a high-pressure rotary jet cement slurry to investigate the properties of the resulting consolidation body and its effect on heavy metal solidification. The results show that the tailings are more likely to release heavy metal elements into the environment. The results of the orthogonal experiments show that the stabilizing agent CCA, which is a combination of fly ash, attapulgite, and Na-bentonite in a 2:1:2 ratio, effectively adsorbs Pb and Zn elements in the tailings. The stabilizing agent CCAPT is created by modifying CCA with 7% H3PO4 at pH of 12 and heat treating at 200 °C. CCAPT demonstrates a 97.2% improvement in stabilization efficiency for Pb and a 94.1% improvement for Zn compared to CCA. The combination of CCAPT and cement slurry resulted in a 25.6% increase in compressive strength and a 29.5% decrease in permeability coefficient compared to the cement slurry formed consolidation body. The core-flooding experiment shows that the residual leachate after consolidation of “5% CCAPT + cementitious slurry” contains only 35.6 μg/L of Pb and 29.2 μg/L of Zn. These concentrations are significantly lower than the national emission requirements. This study presents an experimental foundation for further investigation into the use of high-pressure jet grouting technology to seal tailings ponds.

The effects and solidification characteristics of municipal solid waste incineration fly ash-slag-tailing based backfill blocks in underground mine condition

Currently, there is a limited understanding of the material performance effects and hydration mechanisms of solidified waste-based binder filling materials containing municipal solid waste incineration fly ash in the actual underground filling environment. This study utilized the Circulating Fluidized Bed (CFB) and Grate Furnace (GF) techniques to produce quadri-component uncalcined binder fill materials from municipal solid waste incineration fly ash (MSWI FA), blast furnace slag (BFS), flue gas desulfurization (FGD) gypsum, and tailings. The solidified test blocks were then cured in-situ in a void space of a certain iron underground mine in Hebei with conditions (temperature: 25-30℃, humidity: 18-19%, mine water influx: annual average of 150m3/h). The research results indicate that the mechanical performance and heavy metal solidification outcomes of these blocks surpassed those samples cured under laboratory conditions (temperature: (20±1)℃, humidity: not less than 90%), demonstrating the feasibility of using MSWI FA for underground binding and backfilling in mines. Building upon preliminary research, a binder mix proportion was established: 20wt.% MSWI FA, 70wt.% BFS, and 10wt.% FGD gypsum. Test blocks were fabricated using lead-zinc tailings sand and iron mine tailings as aggregates. All blocks met the 28-day strength requirements for typical mine backfills ranging from 1 to 6.5MPa, with the strength of the XB-M group reaching 24MPa (when cured underground). The leaching concentrations of heavy metals were all below the limits set for class III groundwater standards, with Pb, Zn, Cr, and As achieving a solidification rate of over 98% at 28 days. Microscopic hydration mechanisms indicate that the primary hydration products in the solidified body were ettringite, Friedel's salt, and C-S-H gel. The high content of reactive Al2O3 in the CFB fly ash enables the [AlO4]5- to substitute [SiO4]4-, leading to the formation of a long-chain, high polymerization C-A-S-H phase. Additionally, the abundant Cl- in GF fly ash readily reacted with [Al(OH)6]3−, forming Friedel's salt. The hydration products in the blocks cured under mine conditions significantly increased in their degree of polymerization. This provides a practical application approach for the future treatment and reuse of MSWI FA. Environmental implicationMSWI FA is classified as hazardous waste (HW18) due to its content of harmful components such as chlorides, dioxins, and soluble heavy metals, which pose potential environmental pollution risks. This study, for the first time, solidified test specimens were sent to an underground mining void in a certain iron mine in Hebei, China, for on-site curing (temperature range: 25-30°C, humidity: 18-19%, annual average mine water inflow rate: 150m3/h). The mechanical properties and the solidification performance of heavy metals in the test specimens were superior to those under laboratory curing conditions (temperature: (20±1)°C, humidity not less than 90%).

Zero-carbon inertization processes of hazardous mine tailings: Mineral physicochemical properties, transformation mechanism, and long-term stability

Hazardous mine tailings (HMTs) dam failures can cause devastation to the ecology environment, people's lives and property, which require expensive and complicated remediation engineering systematacially. A cheap and sustainable inertization disposal is proposed for de-risking HMTs without any carbon emissions, stabilizing hazardous heavy metal cations within safety minerals and also sequestering CO2 in the process, simultaneously. Herein, lead-zinc tailings as target HMTs were inertized by using waste rice husk ashes (RHAs) and carbide slag (CS) with a certain ratio, and lead-zinc tailings hardened pastes (LZTHPs) were investigated based on the experimental performance, analytical characteristics, and simulation diffusion methods, to deeply unveil the minerals transformation mechanisms and long-term stability from the cation perspectives. Results revealed that LZTHPs’ compressive strength ranged from 1.04–4.73 MPa and leaching toxicity concentrations of Pb, Zn, Cr, and Cd reached 0.03 mg/L, 1.78 mg/L, 0.01 mg/L, and 0.01 mg/L, respectively. C-S-H gels (Type I and II), cation hydroxides and CO2 mineralization carbonates were the hydrates in LZTHPs. Pb (86%), Zn (78%), Cr (76%), and Cd (65%) were immobilized as residual state, and CO2 mineralization capacity was 0.16 kg/kg. The diffusion coefficient of Pb, Zn, Cr, and Cd below 4.48 × 10−10 cm2/s, 1.39 × 10−10 cm2/s, 4.72 × 10−10 cm2/s, and 0.30 × 10−12 cm2/s, which would be sufficient in most scenarios to adequately stabilize tailings. Diffusion control is the leaching mechanism of cations. After 100 years of simulation diffusion, the diffusion areas of Pb, Zn, Cr, and Cd are 1.33 × 10−3∼1.49 cm2, 2.47 × 10−4∼0.48 cm2, 2.47–8.61 × 10−4 cm2, and 1.49 cm2, respectively, and the environmental impact of LZTHPs was negligible. This study provides promising solutions for alleviating hazardous tailings dangerous, achieving sustainable development with zero-carbon emission, implying the concept of eliminating waste by waste, synchronously.

Sasa argenteostriata – A potential plant for phytostabilization remediation of lead-zinc tailing-contaminated soil

Phytoremediation is an effective way to remediate metal-contaminated soils. During phytoremediation, plants immobilize heavy metals through the roots to reduce the mobility, toxicity and dispersal of the metals, and the changes in the activity of the roots are often accompanied by changes in the rhizosphere ecosystems, in which rhizobacteria are essential components and interact with roots to maintain the stability of the rhizosphere ecosystem and improve soil health. In this study, the phytoremediation potential of Sasa argenteostriata (Regel) E.G. Camu and the response of rhizobacteria were revealed with different levels of lead-zinc tailing contamination (Pb, Zn, and Cd concentrations of 1197.53, 3243.40, and 185.44 mg/kg for M1 and 2301.71, 6087.95, and 364.00 mg/kg for M2, respectively). The BCF of Sasa argenteostriata increased with increasing soil pollution, and the BCFPb, BCFZn, and BCFCd were 0.19, 0.27, and 0.08, respectively, under the M2 treatment; in contrast, the TF decreased with increasing soil pollution, and the TFPb, TFZn, and TFCd were 0.39, 0.85, and 0.07, respectively, under the M1 treatment. The mobility of Pb in the rhizosphere was higher than that of Zn and Cd, and the percentage of residual (Res) Zn and Cd in the rhizosphere increased, while the acid-soluble (Aci) Pb was significantly higher, leading to obvious uptake of Pb by the roots. Correlation analysis showed that Sasa argenteostriata affected the rhizobacterial community by changing the rhizosphere soil pH, the contents of organic matter and NRFM, and bacteria such as Proteobacteria and MND1, which are highly resistant to heavy metals (HMs), became the dominant species in the community. Further PICRUSt2 analysis showed that reducing metal transport across the membranes and increasing the efficiency of cellular reproduction were the main metabolic mechanisms of bacterial tolerance to HMs. Overall, the roots of Sasa argenteostriata were able to immobilize more heavy metals in PbZn tailing-contaminated soil, reducing the toxicity of HMs in the soil, and then influencing the rhizobacteria to change the community structure and metabolism mechanism to adapt to the HM-contaminated environment, and the soil fertility was increased, which together promoted the health and stability of the soil. This study is the first to illustrate the phytoremediation potential and response of the rhizobacterial community of Sasa argenteostriata under multimetal contamination of PbZn tailings. The results of the study provide some guidance for the practice of lead-zinc tailing-phytoremediation and soil health.

Prediction of heavy metal ion distribution and Pb and Zn ion concentrations in the tailing pond area.

The pollution caused by tailings ponds has resulted in ecological damage, with soil contamination significantly impacting the daily lives of residents in the vicinity of mining areas and the future development of mining areas. This study assesses the transport status of heavy metal pollution in tailings areas and predicts its impact on future pollution levels. This study focused on lead-zinc tailing ponds, exploring the spatial and chemical distribution characteristics of heavy metals based on the distributions of Pb, Zn, As, Cu, Cr, Cd, Hg, and Ge ions. The concentrations of the major heavy metal ions Pb and Zn in tailings ponds were predicted via the exponential smoothing method. ① The total accumulation of Pb and Zn in the mine tailings ranges from 936.74~1212.61 mg/kg and 1611.85~2191.47 mg/kg, much greater than the total accumulation of the remaining six heavy metals. The total accumulation of associated heavy metal Cu was high, and the lowest total heavy metals were Hg and Ge at only 0.19 mg/kg and 1.05 mg/kg. ② The analyses of soil heavy metal chemical forms reveal that the heavy metals Pb and Zn had the highest exchangeable state content and state ratio and the strongest transport activity in the industrial plaza and village soils. Pb and Zn are the heavy metals with the greatest eco-environmental impacts in the mining area. ③ The predicted results show that the soil concentrations of the heavy metals Pb and Zn around the tailings area in 2026 are 1.335 and 1.191 times the predicted time starting values. The concentrations of the heavy metals Pb and Zn at the starting point of the forecast are already 3.34 and 3.02 times the upper limits of the environmental standard (according to environmental standards for gravelly grey calcium soils). These results have significant implications for heavy metal pollution risk management.

Study on barrier mechanism and application of silico-alkaline sol-modified bentonite cutoff wall materials to lead pollution in lead-zinc tailings pond

In this paper, the barrier mechanism of silico-alkaline sol-modified bentonite as cutoff wall materials for lead ions in lead‑zinc tailings ponds was investigated. Mechanical property tests, adsorption capacity tests, and permeability tests were conducted to assess the performance of the materials. The results indicated that the addition of silico-alkaline sol at a proportion of 20% by weight of bentonite improved the mechanical strength, anti-seepage ability, and adsorption capacity of the materials towards lead ions. The modification process of bentonite using silico-alkaline sol was confirmed through XED analysis. It was observed that silico-alkaline sol particles adsorbed onto the end face of montmorillonite crystal layer, altering its charge properties. This modification enhanced the adsorption capacity of bentonite towards metal cations. The interaction between the cutoff walls and lead ions was primarily governed by ion exchange. Through the utilization of CT and the finite element method (FEM), demonstrated the exiguity of connected flow lines in the vertical direction within the cutoff walls. Furthermore, column tests revealed that lead ions permeating through the cutoff walls gradually transformed into residuals and were immobilized within the wall. Visual Modflow analysis confirmed the effective application of the cutoff wall in remediating contaminated sites and the potential for practical implementation.

Geochemical properties, heavy metals and soil microbial community during revegetation process in a production Pb-Zn tailings

Lead-zinc (Pb-Zn) tailings pose a significant environmental threat from heavy metals (HMs) contamination. Revegetation is considered as a green path for HM remediation. However, the interplay between HM transport processes and soil microbial community in Pb-Zn tailings (especially those in production) remain unclear. This study investigated the spatial distribution of HMs as well as the crucial roles of the soil microbial community (i.e., structure, richness, and diversity) during a three-year revegetation of production Pb-Zn tailings in northern Guangdong province, China. Prolonged tailings stockpiling exacerbated Pb contamination, elevating concentrations (from 10.11 to 11.53 g/kg) in long-term weathering. However, revegetation effectively alleviated Pb, reducing its concentrations of 9.81 g/kg. Through 16 S rRNA gene amplicon sequencing, the dominant genera shifted from Weissella (44%) to Thiobacillus (17%) and then to Pseudomonas (comprising 44% of the sequences) during the revegetation process. The structural equation model suggested that Pseudomonas, with its potential to transform bioavailable Pb into a more stable form, emerged as a potential Pb remediator. This study provides essential evidence of HMs contamination and microbial community dynamics during Pb-Zn tailings revegetation, contributing to the development of sustainable microbial technologies for tailings management.

Study on acid resistance and high temperature resistance of composite geopolymer-stabilized lead–zinc tailing

Geopolymer is regarded as a potential environmentally friendly substitute for ordinary Portland cement, applicable in construction materials. A cementitious material based on coal gangue and blast furnace slag was employed for the solidification/stabilization of heavy metals from lead-zinc tailings, while multi-walled carbon nanotubes were incorporated to enhance the strength of the solidified matrices. The durability of the solidified bodies was assessed against heating at various temperatures (300 °C, 500 °C, 700 °C, 900 °C, and 1100 °C) and exposure to an acid rain simulation solution with varying pH levels (3, 4, and 5). When subjected to heating and immersion in the erosion solution, the inclusion of lead–zinc tailings led to an augmentation in shrinkage, mass loss, strength reduction, and the leaching of heavy metals from the specimens. X-ray diffraction analysis was performed to characterize the phase transformations in the exposed specimens. The compressive strength of the solidified bodies containing 70 wt% lead–zinc tailings decreased significantly under severe conditions. The leaching test results revealed that the leaching concentrations of these specimens remained well below the standard limits. This suggests that the solidified bodies, which were enhanced with multi-walled carbon nanotubes, exhibited good stability.

Mineralization performance and crystal characteristics of microbial induced carbonate precipitation in lead–zinc tailings under multiple factors

Exploring a low-cost and environmentally friendly cementation method to replace cement bond is a hot topic in tailings cementation backfills. In this study, microbially induced carbonate precipitation technology was used in tailings environment and the mechanisms of mineralization and precipitation of microorganisms were studied, including ambient temperature, pH, cementing solution concentration, and the ratio of bacteria to cement solution. The considered factors are based on tailings backfill site compared to the grouting method, the bacterial liquid and tailings were mixed only once to obtain enough calcium carbonate. The yield and surface morphology of crystal under different parameter conditions were obtained. The experiment results showed that temperature was the most critical factor controlling the yield and morphology of calcium carbonate crystals. The crystal productivity at 35 °C was 92.67%, which was 5.34–14.0% higher than that obtained at other temperatures. Compared with other temperature conditions, the crystal grain size was 2.03–5.57 μm at 35 °C and the crystal structure was irregular and rough, which was more conducive to adhesion and bonding effect with other materials. The bacterium exhibited higher activity and a greater ability to precipitate crystals within the pH range of 6.0 to 8.0, while the environment at a pH of 9.0 had an obvious inhibitory effect on bacterial activity. There was an inversely proportional relationship between the cementing solution concentration and the amount of crystal precipitation. The utilization rate of bacteria and calcium ions reached the highest when the ratio of bacterial liquid to cementing solution was 1:1. The optimal experimental parameters were determined based on a comprehensive consideration of the crystal yield and experimental cost. The research process provided a theoretical basis for the application of microbial tailings backfill.

Synergistic assisted hydrogen production of tailings slurry and coal slurry: Process and mechanism investigation

This study investigated the process and mechanism of synergistically assisted hydrogen production from tailings and coal slurry. We have identified the optimal tailings as lead-zinc tailings through experimentation with different tailings mixed with pulverized coal. Furthermore, we have analyzed the electrochemical properties of Fe2+ and Fe3+ at different concentration gradients in a hydrochloric acid environment and our results have confirmed that the presence of Fe3+ in the simplified environment does not affect the electrochemical processes. to determine the respective roles and effects of the extract and residue of the lead-zinc tailings slurry with equal amounts of coal dust added to them, which has confirmed that it is the lead-zinc tailings extract that has the primary influence. In addition, the electrocatalysis of Fe3+ in the presence of both lead-zinc tailings and coal results in a small increase in current density, and the improvement in current density due to direct and indirect oxidation of coal particles is also extremely limited. Based on our analysis, we have concluded that the increase in current density brought about by the synergistic hydrogen production from lead-zinc tailings-supported coal is mainly due to the different oxidation processes of Fe2+.