Non-ferrous Metal Smelting Research Articles

Effects of the green finance policy on the green innovation efficiency of the manufacturing industry: A difference-in-difference model

This study examined the impact of green finance policy on the green innovation efficiency (GIE) of the manufacturing industry in China based on data between 2005 and 2019 using a difference-in-difference model. The results indicate that implementing the green finance policy reduced the GIE of heavy-polluting industries compared with that of non-heavy-polluting industries. In terms of industry-specific heterogeneity, the green finance policy had a significant negative effect on the GIE of the textile industry, non-metallic mineral products industry, ferrous and non-ferrous metal smelting and rolling processing industry, chemical fiber manufacturing industry, metal product industry, leather and other related industries, and pharmaceutical manufacturing industry. However, it had a significant positive effect on the GIE of the chemical raw material and chemical product manufacturing industry, agricultural and sideline food processing industry, and papermaking and paper product industry. Furthermore, it also promotes the GIE of environment-friendly industries. In terms of factor heterogeneity, the green finance policy has had a positive effect on GIE improvement in technology- and capital-intensive industries. Moreover, it has inhibited GIE improvement in labor-intensive industries. To promote the GIE in manufacturing, a series of policy recommendations have been put forward.

Contribution and Effects of PM2.5-Bound Lead to the Cardiovascular Risk of Workers in a Non-Ferrous Metal Smelting Area Considering Chemical Speciation and Bioavailability.

Lead is known to have toxic effects on the cardiovascular system. Owing to its high concentration, transmission range, and absorption efficiency in organisms, inhalation of fine particulate matter (PM2.5)-bound lead (PM2.5-Pb) may cause significant cardiovascular damage. However, the contribution and adverse effects of PM2.5-Pb on workers and residents in non-ferrous metal smelting areas are not fully understood. In this work, the concentration and chemical speciation of PM2.5-Pb were analyzed to determine its pollution characteristics at a typical non-ferrous metal smelting site. A panel study conducted among factory workers revealed that PM2.5-Pb exposure makes an important contribution to the human absorption of Pb. Although the chemical speciation of PM2.5-Pb suggested poor water solubility, a high bioavailability was observed in mice (tissue average value: 50.1%, range: 31.1-71.1%) subjected to inhalation exposure for 8 weeks. Based on the bioavailability data, the relationship between PM2.5-Pb exposure and cardiovascular damage was evaluated in animal simulation experiments. Finally, a damage threshold and cardiovascular-specific risk assessment model were established for the non-ferrous metal smelting area. Our project not only accurately estimates the risk of PM2.5-bound heavy metals on the cardiovascular system but also offers a scientific basis for future prevention and therapy of PM2.5-Pb-related diseases.

Pollution Profiles, Source Identification and Health Risk Assessment of Heavy Metals in Soil near a Non-Ferrous Metal Smelting Plant.

Heavy metal pollution related to non-ferrous metal smelting may pose a significant threat to human health. This study analyzed 58 surface soils collected from a representative non-ferrous metal smelting area to screen potentially hazardous heavy metals and evaluate their health risk in the studied area. The findings demonstrated that human activity had contributed to the pollution degrees of Cu, Cd, As, Zn, and Pb in the surrounding area of a non-ferrous metal smelting plant (NMSP). Cu, Cd, As, Zn, Pb, Ni, and Co pollution within the NMSP was serious. Combining the spatial distribution and Spearman correlations with principal component analysis (PCA), the primary sources of Cd, As, Pb, and Zn in surrounding areas were related to non-ferrous metal smelting and transportation activities. High non-cancer (THI = 4.76) and cancer risks (TCR = 2.99 × 10-4) were found for adults in the NMSP. Moreover, heavy metals in the surrounding areas posed a potential cancer risk to children (TCR = 3.62 × 10-6) and adults (TCR = 1.27 × 10-5). The significant contributions of As, Pb, and Cd to health risks requires special attention. The construction of a heavy metal pollution management system will benefit from the current study for the non-ferrous metal smelting industry.

Effect of goethite-loaded montmorillonite on immobilization of metal(loid)s and the micro-ecological soil response in non-ferrous metal smelting areas

In this work, the immobilization stabilization and mechanism of heavy metal(loid)s by goethite loaded montmorillonite (GMt) were investigated, and the soil microbial response was explored. The simulated acid rain leaching experiment showed that GMt had a higher acid tolerance and the more stable heavy metal(loid)s fixation ability. The soil incubation demonstrated that GMt significantly decreased the available Cd, Zn, Pb and As concentration. Interestingly, higher immobilization of heavy metals was observed by GMt in highly acid leached and acidic soils. The richness and diversity of bacterial communities improved after the addition of GMt. GMt induced the enrichment of the excellent functional bacteria of the phylum Proteobacteria as well as the genus Massilia and Sphingomonas. The main immobilization mechanisms of heavy metal(loid)s by GMt include electrostatic interaction, complexation, precipitation and oxidation. The addition of the GMt also optimizes the soil bacterial community structure, which further facilitates the immobilization of heavy metal(loid)s. Our results confirm that the novel GMt has a promising application in the immobilization and stabilization of heavy metal(loid)s contaminated soils in non-ferrous metal smelting areas.

Analysis of driving factors of spatial distribution of heavy metals in soil of non-ferrous metal smelting sites: Screening the geodetector calculation results combined with correlation analysis

Heavy metals (HMs) discharged from smelting production may pose a major threat to human health and soil ecosystems. In this study, the spatial distribution characteristics of HMs in the soil of a non-ferrous metal smelting site were assessed. This study employed the geodetector (GD) by optimizing the classification condition and supplementing the correlation analysis (CA). The contribution of driving factors, such as production workshop distributions, hydrogeological conditions, and soil physicochemical properties, to the distribution of HMs in soil in the horizontal and vertical dimensions was assessed. The results showed that the main factors underlying the spatial distribution of As, Cd, Hg, Pb, Sb, and Zn in the horizontal direction were the distance from the sintering workshop (the maximum q value of that factor, q=0.28), raw material yard (q=0.14), and electrolyzer (q=0.29), while those in the vertical direction were the soil moisture content (q=0.17), formation lithology (q=0.12), and soil pH (q=0.06). The findings revealed that the CA is a simple and effective method to supplement the GD analysis underlying the spatial distribution characteristics of HMs at site scale. This study provides useful suggestions for environmental management to prevent HMs pollution and control HMs in the soil of non-ferrous metal smelting sites.

Tracking Key Industrial Sectors for CO2 Mitigation through the Driving Effects: An Attribution Analysis.

The heavy pressure to improve CO2 emission control in industry requires the identification of key sub-sectors and the clarification of how they mitigate CO2 emissions through various actions. Focusing on 30 Chinese provincial regions, this study quantifies the contribution of each industrial sector to regional CO2 mitigation by combining the logarithmic mean Divisia index with attribution analysis and extract the key sectors of CO2 mitigation for each region. Results indicate that during 2010-2019, significant emission reduction was achieved through energy intensity (74%) in Beijing, while emission reductions were attained through industrial structure changes for Anhui (50%), Henan (45%), and Chongqing (45%). The contribution to emission reduction through energy structures is not significant. The production and supply of power and heat (PSPH) is a central factor in CO2 mitigation through all three inhibitive factors. Petroleum processing and coking (PPC) generally contributes to emission reduction through energy structures, while the smelting and pressing of ferrous metals (SPMF) through changes in industrial structures and energy intensity. PSPH and SPMF, in most regions, have not achieved the emission peak. Except in the case of coal mining and dressing (CMD), CO2 emissions in other key sectors have almost been decoupled from industrial development. CMD effectively promotes CO2 mitigation in Anhui, Henan, and Hunan, with larger contribution of PPC in Tianjin, Xinjiang, Heilongjiang, and that of smelting and pressing of nonferrous metals in Yunnan and Guangxi. The findings help to better identify key sectors across regions that can mitigate CO2 emissions, while analyzing the critical emission characteristics of these sectors, which can provide references to formulating region- and sector-specific CO2 mitigation measures for regions at different levels of development.

Labor rate setting as a framework for enhancing efficiency of mining industry

Production engineering in mines of the Norilsk Division of Norilsk Nickel is experiencing considerable modification. Under conditions of continuous retrofit, production improvement and digitalization and unmanned machinery phase-in, the efficient labor management is a prerequisite of production in a transition period. It is emphasized that the Company’s top managers pay peculiar attention to the primary pitch of the production chain—exploration and extraction of rich ore to be concentrated later on and sent to smelting of nonferrous metals (palladium, nickel, platinum copper, as well as silver and gold). The increase in available ore reserves and the gain in production output are amongst the top priority trends of advancing the Norilsk Division of the Company. The article describes the labor rate setting systems adopted at Norilsk Nickel’s Polar Division and generalizes the experience gained in labor rate setting in the mining industry. The photo chronometry observations are illustrated, and the structure of the work time expenditures and losses is analyzed. The elaborated local regulatory documentation enabled a precision computation of labor force as per the actual labor conditions, labor management and occupational safety at a specific production unit. Labor rate setting almost always entails organizational changes—adjustment of operating regime, shift planning, etc., and is often a catalyzer of innovations to be introduced. Furthermore, labor rate setting enables planning, budgeting and real-time management of operations toward meeting strategic challenges in the today’s business environment.

Highly effective remediation of high arsenic-bearing wastewater using aluminum-containing waste residue

Wastewater from non-ferrous metal smelting is known as one of the most dangerous sources of arsenic (As) due to its high acidity and high arsenic content. Herein, we propose a new environmental protection process for the efficient purification and removal of arsenic from wastewater by the formation of an AlAsO4@silicate core-shell structure based on the characteristics of aluminum-containing waste residue (AWR). At room temperature, the investigation with AWR almost achieved 100% As removal efficiency from wastewater, reducing the arsenic concentration from 5500 mg/L to 52 μg/L. With Al/As molar ratio of 3.5, the structural properties of AWR provided good adsorption sites for arsenic adsorption, leading to the formation of arsenate and insoluble aluminum arsenate with As. As-containing AWR silicate shells were produced under alkaline conditions, resulting in an arsenic leaching concentration of 1.32 mg/L in the TCLP test. AWR, as an efficient As removal and fixation agent, shows great potential in the treatment of copper smelting wastewater, and is expected to achieve large-scale industrial As removal.

Development of selective mercury recovery technology by using iron iodide from waste sludge of non-ferrous metal smelting process

The waste sludge from non-ferrous metal smelter contains high concentrations of mercury (Hg), arsenic (As) and sulfur (S). The Article 11 of the Minamata Convention on Mercury mandates the recovery of Hg before the disposal stage of Hg waste. However, As compounds have similar boiling points with Hg compounds, and they are considered interfering substances in the recovery of Hg. Moreover, a high concentration of S requires significant energy to volatilize Hg. This study examined the optimal conditions for selective recovery of Hg and energy reduction by introducing FeI2 as an additive during thermal treatment. Thermogravimetric analysis was utilized to evaluate the conversion of HgS to HgI2 under the influence of FeI2. The optimal conditions for thermal treatment such as temperature, treatment time, and molar ratio of [Hg]:[As]:[FeI2] were explored. The simulated waste indicated that the maximum separation efficiency of Hg was ∼95%, thereby allowing a selective separation of 81.5% of Hg from waste sludge with an Hg content of 0.33%, As content of 23.8%, and S content of 30.7%. Sequential extraction procedure was applied to evaluate the stability of Hg and As for residues. As a result, most Hg was vaporized and As was stabilized in sulfide, crystalline, and amorphous forms.

The stabilization mechanism of high-efficiency magnesium phosphate cement for arsenic remediation in lollingite polluted environments

Industrial non-ferrous metal smelting and processing activities are a major contributor to the migration of arsenic-containing minerals throughout the environment, such as lollingite, which poses a severe threat to human health due to its rapid oxidation and subsequent release of arsenic (As). Herein, two phosphate mineral systems (potassium phosphate and calcium phosphate) were used to explore the potential for As solidification and establish the As immobilization mechanisms. Experimental results show that the compressive strength of the calcium phosphate system was higher than that of the potassium phosphate system due to the higher bond energy of the Ca–O–Mg–O–P–O system (31109 kJ /mol), as compared to the K–O–Mg–O–P–O system (16189.2 kJ /mol). Furthermore, the coordination capability of arsenic oxyanions with Ca or Fe ions was stronger than that of phosphorus oxyanions with Ca or Fe ions. The main mechanism of inhibition of As migration by magnesium phosphate cement (MPC) binders, was the formation of FeAsO4.H2O, Ca3(AsO4)2.H2O, MgHAsO4.H2O, CaMgAsO4(OH) and KMgAsO4.6H2O coprecipitates, with physical encapsulation by MgKPO4·6H2O (K-struvite), Ca2Mg(PO4)2·2H2O (Ca-struvite) and Mg2PO4(OH) phosphate-gel. Using Fe2O3-modified MPC binders with a Fe/As molar ratio of 3, the As immobilization efficiency reached 98.73%. The results of toxicity characteristic leaching procedure (TCLP) analysis confirmed that the maximum leached As concentrations from MPC binders cured for 7 days and 28 days were 0.31 mg/L and 0.06 mg/L, respectively, both of which were below the maximum permitted value for safe disposal (5 mg/L). These results verify the potential of MPC binders to be utilized as low-environmental impact and high-efficiency cementitious matrices for As pollution control and environmental remediation.

In situ mechanochemical activation of reduced iron powder for arsenic stabilization in high content arsenic sulfide sludge

Arsenic sulfide slag (ASS) with high content of arsenic is a common industrial waste in nonferrous metal smelting. Because of the high potential of arsenic leaching under environmental conditions, it brings serious ecological threat during storage. Stabilization of the unstable arsenic in ASS is urgently needed for its safe disposal. Current stabilization methods such as hydrothermal treatment, stabilization/solidification, and thermal copolymerization still face challenges including high energy consumption, poor stabilize efficiency and large volume increase after treatment. Here we developed a mechanochemical strategy to stabilize the bleachable arsenic using reduced iron powder as stabilizer. The arsenic leaching concentration was decreased from 18484.9 mg /L to only 56.3 mg/L after treatment, achieving a stabilization efficiency of 99.7 %. The mechanism study proved that MC treatment triggered the corrosion of Fe powder and dissolution of As2O3 with the help of acidic water in the ASS. An integration of the rapid reduction and oxidation then happened for the soluble arsenic. The produced As(II) and As(V) reacted with sulfide and iron oxides, greatly reducing the arsenic leaching concentration. The BCR sequential extraction results further conformed most of the arsenics (83.7 %) in ASS were stabilization into the environmental stable residual fraction.

Particle collection and heavy metals migration during high-temperature electrostatic precipitation in copper smelting: A pilot-scale study

Recently, large amounts of particulate matter (PM) and heavy metals (HMs) have been generated in the processes of non-ferrous metal smelting (NFMS). High-temperature electrostatic precipitator (HT-ESP) was the key method to capturing PM while extensive HMs enriched. In this work, the PM collection and migration of HMs in the HT-ESP process of copper smelting were investigated through an established pilot-scale platform. The excellent performance of the pilot-scale HT-ESP could achieve a particle collection efficiency of 99.5 %. The distribution patterns of HMs in various particle sizes revealed that the volatile heavy metals, arsenic (As) and selenium (Se) were predominantly distributed in PM1.0 and PM1-2.5 with a moderately dispersed distribution, whereas copper (Cu) and lead (Pb) were densely concentrated on particles. When the temperature difference between the inlet and the outlet of the HT-ESP narrowed to 23 K, the original As and Se enriched in hopper particles partially volatilized and migrated into the gas phase and adhered to tiny size particles. The enrichment ratio in the gas phase (ERG) of As and Se increased by 2.7 % and 18.5 %, respectively. The results were beneficial to reducing the enrichment of volatile HMs in copper smelting ash and provided guidance for resource utilization of the copper smelting industry.

Comprehensive assessment of environmental and health risks of metal(loid)s pollution from non-ferrous metal mining and smelting activities

Abandoned non-ferrous metal mining and smelting sites have left a degraded environmental legacy, threatening the ecosystem and human health, particularly by the presence of As, Cd, Pb, and Cu as major contaminants. The health of the metal-contaminated soils was assessed by combining physicochemical parameters and microbial metabolism activity analyses. Low microbial metabolic activity indicated that soil microorganisms were inhibited by the presence of heavy metals. The content and speciation distribution of metals were closely linked to the measured microbial metabolic indicators. The invertase (INV) activity and peak time (Tpeak) were identified as sensitive bio-indicators for assessing soil health conditions. Combination environmental assessment (CEA) pollution, considering the total content and chemical form of metal(loid)s, revealed Cd, As, Pb, and Cu all reached high pollution degrees at the surrounding area, while Cr, Mn, Sb, Zn, Ni, and V were low pollution degrees. Different research sites ranked by potential ecological risk index (RI) as follows Pollution site (24621.22) > East site (19330.32) > West site (12989.49) > South site (9281.05), while different sites were sorted in reverse order by microbial indicators. The analyses revealed that the main human health risk was linked to As, threatening the local population with non-carcinogenic and carcinogenic hazards, particularly for children.

Characteristics and source analysis of potentially toxic elements pollution in atmospheric fallout around non-ferrous metal smelting slag sites-taking southwest China as an example.

More accurate source analysis of potentially toxic elements (PTEs) in atmospheric fallout that endanger biodiversity and human health remains needed. This study determined the concentrations of seven PTEs, including Pb, Cd, As, Cu, Zn, Ni, and Cr, by inductively coupled plasma mass spectrometry (ICP-MS), and the sources of PTE pollution were quantified using multivariate statistical analysis, including principal component analysis (PCA), cluster analysis (CA), and Pearson correlation analysis, and Moran index was applied for mutual verification and supplementation. PCA and CA revealed that the same mixed sources of Pb, Cd, As, Cu, and Zn were found in the atmospheric dust fall in the study area, while Ni and Cr had the same source of pollution. Pearson correlation analysis provided that there were strong correlations between Pb-Cd, Pb-As, Pb-Cu, Cd-As, Cd-Cu, As-Cu, and Ni-Cr, indicating commonality between the two sources of heavy metal pollution. Additionally, the Moran index showed that strong spatial correlations were observed between Pb, Cd, As, Cu, and Zn, whose sources were mainly related to non-ferrous metal processing smelter smelting slag sites and an environmental company in the study area. However, no spatial correlation was found between Ni and Cr, which mainly originated from the local geological background.

Evaluating the dynamic effects of mitigation instruments on CO2 emissions in China's nonferrous metal industry: A vector autoregression analysis

Reducing carbon dioxide (CO2) emissions in China's nonferrous metal industry is important for reaching China's ambitious goals for carbon peaking and neutrality. Prior research identified several carbon abatement instruments for the industry. However, the dynamic influence of different mechanisms on CO2 emissions in the industry remains unclear, and few studies have researched CO2 emission reductions in two nonferrous metal related industrial subsectors: nonferrous metal ore mining and nonferrous metal smelting. This research evaluated the dynamic effect of abatement instruments on the CO2 emissions in these two subsectors. The research discovered the factors that are highly linked with CO2 emissions by using an enhanced Stochastic Impacts by Regression on Population, Affluence, and Technology model. The dynamic influence of these factors on CO2 emissions in the two subsectors was investigated using a vector autoregressive model. Findings show that in the two subsectors, labour productivity and industrial value-added are the most important factors explaining CO2 changes. The two variables have a negative long-term effect on CO2 emissions in the nonferrous metal ores mining, and increase CO2 emissions in the smelting of nonferrous metals. Improving energy efficiency in the nonferrous metal smelting industry decreases the CO2 emissions only in the short term. In all sectors, lowering the electrical carbon emission factors and changing the energy structure using different techniques are expected to help reduce long-term CO2 emissions. These results are critical for the Chinese government in creating long- and short-term energy plans for the nonferrous metal sector.

Novel microbial consortia facilitate metalliferous immobilization in non-ferrous metal(loid)s contaminated smelter soil: Efficiency and mechanisms

Exposure to toxic metals from nonferrous metal(loid) smelter soils can pose serious threats to the surrounding ecosystems, crop production, and human health. Bioremediation using microorganisms is a promising strategy for treating metal(loid)-contaminated soils. Here, a native microbial consortium with sulfate-reducing function (SRB1) enriched from smelter soils can tolerate exposures to mixtures of heavy metal(loid)s (e.g., As and Pb) or various organic flotation reagents (e.g., ethylthionocarbamate). The addition of Fe2+ greatly increased As3+ immobilization compared to treatment without Fe2+, with the immobilization efficiencies of 81.0% and 58.9%, respectively. Scanning electronic microscopy-energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy confirmed that the As3+ immobilizing activity was related to the formation of arsenic sulfides (AsS, As4S4, and As2S3) and sorption/co-precipitation of pyrite (FeS2). High-throughput 16S rRNA gene sequencing of SRB1 suggests that members of Clostridium, Desulfosporosinus, and Desulfovibrio genera play an important role in maintaining and stabilizing As3+ immobilization activity. Metal(loid)s immobilizing activity of SRB1 was not observed at high and toxic total exposure concentrations (220–1181 mg As/kg or 63–222 mg Pb/kg). However, at lower concentrations, SRB1 treatment decreased bioavailable fractions of As (9.0%) and Pb (28.6%) compared to without treatment. Results indicate that enriched native SRB1 consortia exhibited metal(loid) transformation capacities under non-toxic concentrations of metal(loid)s for future bioremediation strategies to decrease mixed metal(loid)s exposure from smelter polluted soils.

Lability, bioaccessibility, and ecological and health risks of anthropogenic toxic heavy metals in the arid calcareous soil around a nonferrous metal smelting area

Lability and bioaccessibility of anthropogenic toxic heavy metals in arid calcareous soils are critical to understand their ecological and health risks. This study examined toxic heavy metal speciation in the calcareous soil contaminated by nonferrous metal smelting. Results demonstrated that approximately 70 years’ nonferrous metal smelting and mining in Baiyin led to significant contamination of nearby soil down to about 200 cm depth by cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn), with more serious contamination in the downwind areas of smelting or mining. More than half of Cd, Cu, Pb, and Zn in the soil was present in the labile fractions while more than 75% of cobalt (Co), chromium (Cr), nickel (Ni), and vanadium (V) was present in the residual fraction. Carbonate minerals in this calcareous soil play an important role in the labile fractions, with approximate 25% of Cd and Pb and 15% of Cu and Zn bound in carbonates. Bioaccessible Cd, Cu, Pb, and Zn in the soil were approximately 49.8%, 29.4%, 12.2%, and 33.8% in gastric phase and 13.5%, 15.9%, 4.3%, and 9.1% in intestinal phase of their total concentrations, respectively. Therefore, Cd and Zn were removed from gastric solution to a greater extent than Cu and Pb by neutral intestine environment. However, bioaccessible Co, Cr, Ni, and V in the soil were less than 3% of their total concentrations. Bioaccessibility of these metals but Cu in this calcareous soil was significantly lower than that for the acidic Ultisols and Alfisols in U.S. The concentrations of Cd, Cu, Pb, Zn, and Ni in each chemical and bioaccessible forms were significantly correlated linearly with their total concentrations in the calcareous soil, while only residual concentration was significantly correlated with the total concentration for Co, Cr, and V. These linear slopes showed that relative lability and bioaccessibility increased for Cd, but decreased for Cu, Pb, and Zn with the increase in their total concentrations in the calcareous soil. Direct oral soil ingestion would not pose a non-carcinogenic health risk to local children. However, very high potential ecological risk would be caused by these metals in the soil. These results provide improved insights into the biogeochemical processes of anthropogenic toxic heavy metals in the arid calcareous soils worldwide.

Fundamental research on selective arsenic removal from high-salinity alkaline wastewater

The alkaline leaching process of arsenic-containing solid waste discharged during nonferrous metal smelting affords typical high-salinity alkaline arsenic-containing wastewater (HSAW). In this study, for the first time, Me (Ca2+ and Mg2+)–AsO43−–OH−–H2O and Me (Ca2+ and Mg2+)–AsO43−–CO32−–H2O systems are studied based on a thermodynamic equilibrium diagram and an arsenic removal experiment, proving that the removal of arsenic using single metal ions in the presence of CO32− is infeasible because of carbonate coprecipitation. Based on this observation, a new method that uses magnesium ammonium complex salts (MACSs) for HSAW treatment is proposed. Based on the thermodynamic calculations of the Mg2+–AsO43−–NH4+–CO32−–H2O system and the arsenic removal experiment, carbonate and arsenate can be selectively separated by the formation of magnesium ammonium arsenate (NH4MgAsO4·6H2O). In an arsenic solution containing 150-g/L Na2CO3, the arsenic removal rate and the arsenic grade of the precipitation product reach 90.16% and 27.13%, respectively, when the molar ratios of Mg2+/NH4+:As(V) are 1.8:1 and 2:1, respectively. The proposed method is successfully employed for treating a leaching solution of alkaline arsenic slag discharged during antimony smelting. The findings of this study will broaden the basic theory of HSAW treatment and lay a foundation for the resource treatment of arsenic-containing solid waste.

Recovery of matte from copper slag by using rubber seed oil as green reductant

The traditional fossil reductant used in the copper slag cleaning process cannot fulfill the requirements of sustainable development of the copper industry and environmental protection. Therefore, a new approach of employing renewable rubber seed oil (RSO) instead of a non-renewable fossil reductant to clean copper slag (reduce magnetite concentration and improve matte recovery) was put forward in this study. The cracking characteristics of RSO at high temperature and the effects of technical parameters (such as reduction temperature, oil amount and settling time) on the copper loss, magnetite concentration and RSO utilization degree were thoroughly investigated. The results indicated that the cracking products of RSO at high temperature were mainly composed of C and H2. Under the conditions of a temperature of 1250 °C, an injection of 4 mL of RSO, and a settling time of no less than 1.5 h, the content of magnetite was reduced to less than 1 wt.%, and the content of copper in the upper level of the slag was lowered to be less than 0.57 wt.%, which met the criteria for discarding slag industrially. The copper slag cleaning by RSO is a process of carbon neutrality. The results provide a theoretic basis for the application of bioenergy in non-ferrous metal smelting process.

Biochar enhanced Cd and Pb immobilization by sulfate-reducing bacterium isolated from acid mine drainage environment

Sulfate reducing bacteria (SRB) is considered to be the most promising alternative biological treatment for immobilization of heavy metals due to its high efficiency and low cost. However, the mechanism underlying the biomineralization process has remained unclear. The strain used in this study was isolated from a nonferrous metal smelter, and it was immobilized on biochar to produce biochar inoculated bacterium(BIC); the Cd2+ and Pb2+ immobilization efficacy of BIC were investigated under differing reaction times, temperatures, pH, solid liquid ratios and heavy metal concentrations. Moreover, the BIC immobilization products were analyzed by a series of characterization techniques. The results indicated that the strain identified as Clostridium sulfidigenes HY-1 was found to exhibit high resistances to Cd2+ and Pb2+. The immobilization efficiency of BIC was much better than that of separate strain HY-1 and biochar. Altogether, the optimal immobilization conditions of BIC were found to be 3 d, pH 8.0, 30 °C, biochar addition of 0.6 g/L, and initial Cd2+ and Pb2+ concentrations of 5 and 30 mg/L, respectively. Under these conditions, the immobilization efficiencies of Cd2+ and Pb2+ were 67.9%, 95.7%, respectively. In addition, the BIC immobilization products were analyzed by Fourier transform infrared spectrometer, scanning electron microscope, energy dispersive spectroscopy and further confirmed to be CdS and PbS by X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that biochar could enhance the bacterial immobilization effect; strain HY-1 produced S2− during sulfate reduction, which could accumulate and react with Cd2+ and Pb2+ to form metal sulfide precipitates, mainly in the form of CdS and PbS that were immobilized and removed. These results suggest that BIC shows promise as an efficient means of immobilizing Cd2+ and Pb2+ from acid mine drainage (AMD).