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How to effectively recycle Ni–Co ore mining mullock (OMM) is a key means to address both local environmental pollution and resource waste. In this study, OMM and bottom ash (BA) were prepared into cementitious materials (OBM) by mechanochemical means with gentle conditions. It is mainly realized by grinding the mixture and pressing it into columnar blocks. The results show that the maximum compressive strength of OBM is 4.803 MPa in 28 day meet the standard of China mine backfilling for mine repair, and the stability efficiency of Ni2+ and Co2+ is above 90%. The mechanism studies show that the amorphous materials recombine to form silicon-aluminum polymers, while a small portion of Ni2+ and Co2+ binds to the polymer during consolidation to form massive structure. Most of the heavy metal ions are encased in the hard structure, which is relatively stable and without pollution risk. The chemical behavior of metals in the system is fitted by geochemical model. This study not only solved the problem of heavy metal contamination in OMM, but also transformed it into a cementitious material that can be used for backfilling of local pits.

Municipal solid waste incineration fly ash (MSWIFA) exsits in large quantitities and contains pollutants such as heavy metal. While solidification is one of the most effective methods for treating MSWIFA, this application is limited by cost, subsequent treatment, and simultaneous immobilization of anions and cations. This research demonstrated that under a certain initial pressure (20 MPa), a gelation reaction involving ball milling-modified tourmaline powder, a small amount of cement clinker, and MSWIFA forms a stable consolidated body and significantly reduces the risk of heavy metal dissolution. The consolidated MSWIFA can easily be formed into unfired bricks in large-scale pilot production, and a response surface model was used to optimize the experimental parameters. When the mass ratio of tourmaline: cement clinker: MSWIFA was 15:15:200 (mixed with a moisture content of 13 to 15 %), the compressive strength of the consolidated body reached 13 MPa, and the amounts of Cr and Pb leached decreased from 12 mg/L to 0.1 mg/L and 25 mg/L to 0.3 mg/L, respectively. The consolidated form contained a new mineral phase (Ca

Aiming at the existing problems of poor treatment effect and immersion stability of expansive soils, a slag soil hardener (SSH, developed by Wuhan University, China) was combined with different additives to dispose in this study. The free expansion rate, compressive strength, and immersion stability of samples were compared, and the influences of different additives, curing age, and dry density on the process and mechanism of improvement were discussed. The experimental results indicated that SSH combined with quicklime had the best improvement effect on expansive soils, in which the mass ratio of raw materials was: expansive soil/SSH/quicklime = 92/4/4, and the free expansion rate decreased from 45.90% to 4.4%, compressive strength increased from 2.53 MPa to 6.69 MPa, and there was no splitting after immersion under this ratio. FTIR spectroscopy, XPS and SEM were performed to analyze the characteristic functional groups, structural forms, and morphology of samples to study the mechanism of improvement, which showed that SSH greatly reduced the proportion of montmorillonite in the whole system and further enhanced the mechanism of ion exchange, soil particle connection, and coating protection. The research can provide theoretical reference for engineering the application of expansive soil area in rainy climate and has dual economic and environmental benefits.

Lead-zinc tailings (LZTs) are industrial by-products containing a large number of heavy metals that seriously harm the ecological environment and human health. This study was performed to propose a sustainable and efficient method for immobilizing Pb, Cr, and Cd in LZTs by using solid waste. To better assess the immobilization performance and mechanism, the leaching toxicity, fraction distribution, unconfined compressive strength, environmental risk assessment, and hydration products were explored. The LZTs were mixed and molded with different constituents of ground granulated blast furnace slag (GGBFS) and rice husk ashes (RHAs) at different curing temperatures. Results suggest that ≥99% of the Pb, Cr, and Cd were immobilized mainly in the form of residual fractions in the LZTs. The amounts of Pb, Cr, and Cd in the bioavailable fractions notably decreased by approximately 99.83%, 99.58%, and 97.05%, respectively. After stabilization/solidification (S/S) disposal, Pb, Cr, and Cd showed low to even no risk. The RHAs were effective to stabilize Pb, and GGBFS was effective to stabilize Cr. However, both materials showed almost equal effects to Cd. Ettringite, C-S-H gel, and portlandite were the main hydration products to immobilize Pb, Cr, and Cd, and these hydration products provided a source of strength. Honey-comb or reticular network C-S-H gel possessed higher specific surface area, higher pore volume, and bigger pore size than the other materials. The proposed method could explain the sustainability and efficiency of the S/S of Pb, Cr, and Cd in LZTs by using RHAs. This study opens up new perspectives for disposing heavy metal by using accessible agricultural solid waste (i.e., RHAs) in rural areas, and the solidified block shows certain economic benefits.

In acidic medium, hazardous heavy metals of lead-zinc tailing (LZT) are easily leachable and mobilizable. Thus, the hazard, amount, form, and complexity of the leached heavy metals under acidic precipitation become a major environmental concern. This work investigates the gangue minerals, toxicity, speciation, leaching characteristics of heavy metals in LZT under simulated acid rain, as well as immobilization effects and mechanisms using a sustainable binder. In LZT, dolomite, quartz, calcite, and muscovite are the main gangue minerals, tiny hazardous metallic minerals were absorbed in the surface. The results revealed that Pb, Zn, Cr, and Cd were the predominant harmful elements, particularly Pb and Zn. Zn is leached completely and is the concerned hazardous element under simulated acid rain. In the acid rain neutralization ability test, the amount of leachable Pb, Cr, Ca, and Si maintained in equilibrium, leached Zn, Cd, Al, and Mg depended on the addition of acid. Pb and Ca were sedimented in residues. Immobilization of Pb, Zn, Cr, and Cd depended on the stability of Ca(OH)

From 12 mining areas surrounding a manganese mining area in Guangxi, soil samples were collected at different distances from the center of the mining area and different sampling points at the same distance. 16S rRNA gene sequencing was used in extracting and amplifying DNA in the soil samples, and double-terminal gene sequence library comparison was performed. Through OUT clustering, species community, species diversity, and inter-group difference analyses, the composition of microbial community and biological diversity in the mining soil was evaluated. Results showed that the soil around the mining area was affected by heavy metals, and species complexity was positively correlated with distance. Proteobacteria, Firmicutes, Bacteroidetes, and Acidobacteria were the dominant species with high abundance in some soil samples because of their pollution tolerance. The samples closer to the center were more disturbed by mining activities, and species diversity sequencing based on observed species index and Shannon index was consistent with that of cluster analysis. Differences among the sample groups at 2 km from the center were the smallest, and species diversity had the highest similarity. Differences among the sample groups at 1 km from the center were the largest, and species composition significantly varied. Microorganism distribution is an important indicator of soil ecological characteristics, and the analysis of species and diversity of soil microorganisms is important to the assessment of the impact of mining activities and the extent of soil contamination.

Phthalic acid esters (PAEs) are teratogenic and carcinogenic and mainly metabolized by microorganisms in sediment. A novel strain, Cupriavidus oxalaticus strain E3, was isolated and characterized from sediment for PAEs degradation. The transformation of dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) as the sole carbon source by strain E3 was systematically studied in the darkness through the kinetic studies and analysis of intermediates. After the initial lag pause of 5 h–8 h, the strain efficiently degraded 87.4%–94.4% of DBP and 82.5%–85.6% of DEHP at an initial amount of each phthalate of 200 mg/L after 60 h of incubation. The biodegradation rate of DBP and DEHP followed a first-order kinetic model, and degradation rate constants (k) of them by E3 were 1.37 and 0.86 d−1, respectively. Gas chromatography–mass spectrometry (GC–MS) results revealed that the tentative PAEs degradation pathway, included the transformation from PAEs to phthalic acid (PA) and the complete mineralization of PA. In the phase of PAEs to PA, DBP with short sides reduced the chain length via hydrolyzation, and DEHP with long sides reduced the chain length via hydrolyzation and β-oxidation. The 3D model of monoester hydrolase from C. oxalaticus was predicted and used for docking with mono-2-ethylhexyl phthalate (MEHP) and mono-n-butyl phthalate (MBP). The docking results showed that the conserved catalytic triplet structure (Ser140, His284, and Asp254) acted as active sites and participated in degrading PMEs. This study provided novel insights into the mechanisms of PAEs degradation at a molecular level and widened the scope of functional bacteria by isolating strain E3.

The lead-zinc areas of China have faced serious foulteousqulated heavy metal pollution. In this study, data on As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn concentrations in China's lead-zinc mine tailings were collected and screened from published literature (2015-2020). The contamination assessments, geographical distributions, and health risk assessments of the eight heavy metals were analyzed. The results revealed that the mean concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn exceeded the corresponding background values for soils. Moreover, most of the lead-zinc mine tailing areas contaminated by heavy metals were located in the southern and eastern regions of China. The health risk assessment results indicated that oral ingestion was the main exposure route of heavy metals in the mine tailings, and children were more vulnerable to adverse effects. For a single metal, As and Pb presented high non-carcinogenic risks, and As and Cu presented the unacceptable carcinogenic risks. This study provides a timely analysis proving the urgent necessity of the treatment of heavy metal pollution in lead-zinc tailings in China.

The increasing accumulation of electrolytic manganese residue (EMR) with high ammonium nitrogen and heavy metals has become the biggest obstacle restricting the sustainable development of electrolytic manganese industry. A novel method for efficient recovery of ammonium nitrogen as well as solidification of Mn and other heavy metals in the process of preparation of EMR based baking-free brick (B-EMR) was invented by mechanical milling in the coexistence of water and calcium oxide for the first time. It was demonstrated that the solidification/recovery efficiency of Mn and ammonium nitrogen can reach more than 98%. And the compressive of B-EMR was higher than 12 Mpa, which met the requirement of China's national industry standard of stronger than 9.6 Mpa (JC/T 239–2001). Mechanochemical action breaked the Si–O bond and promoted the calcium silicate-like cementitious structure, which contributed to the compressive strength of B-EMR and the solidification of heavy metals. CaO plays a key role in the conversion of ammonium nitrogen in EMR to NH3 and enhanced by mechanical milling. This study provided a feasible path for the resource disposal of EMR. And demonstrated a solution for the limitation of ammonium nitrogen and heavy metals in the large-scale utilization of EMR.

Phthalic acid esters (PAEs) are a class of biologically accumulated carcinogenic and teratogenic toxic chemicals that exist widely in the environment. This study, Pseudarthrobacter defluvii E5 was isolated from agricultural soils and showed efficient PAEs-degradation and -mineralization abilities for five PAEs, and encouraging PAEs tolerance and bioavailable range for dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) (0.25-1200 mg/L). The complete catalytic system in E5 genome enables PAEs to be degraded into monoester, phthalate (PA) and Protocatechuic acid (PCA), which eventually enter the tricarboxylic acid cycle (TCA cycle). The preferred PAEs-metabolic pathway in soil by E5 is the metabolism induced by enzymes encoded by pehA, mehpH, pht Operon and pca Operon. For the first time, two para-homologous pht gene clusters were found to coexist on the plasmid and contribute to PAEs degradation. Further study showed that P. defluvii E5 has a broad application prospect in microplastics-contaminated environments.

Soil contamination by multiple heavy metals and As is one of the major environmental hazards recognized worldwide. In this study, pinecone-biochar was used for stabilization and passivation of Pb, Cu, Zn, Cr, and As in contaminated soil around a smelter in Hubei province, China. The stabilization rate of heavy metals in soil can exceed 99%, and the leaching amount can meet the national standard of China (GB/T 5085.3-2007, less than 5, 100, 100, 15, and 5 mg/L, respectively.) within 90 days. The study confirmed that the addition of pinecone-biochar and the coexistence of indigenous microorganisms can effectively reduce the bioavailability of heavy metals. Among the heavy metals, As(III) can be oxidized to As(V) and then stabilized, and other heavy metals can be stabilized in a complex and chelated state characterized by X-ray photoelectron spectroscopy. After pinecone-biochar was added, the abundance of microbial community and intensity of metabolic activities became vigorous, the types and contents of dissolved organic matter increased significantly. A novel innovation is that the addition of pinecone-biochar increased the Bacillus and Acinetobacter in soil, which enhanced the function of inorganic ion transport and metabolism to promote the passivation and stabilization of heavy metals throughout the remediation process.

Physical conditioners or skeleton builders are usually used to improve the dewaterability of sewage sludge. In this study, low-cost rice husk (RH) was evaluated as an alternative skeleton builder and combined with Fe2+ and sodium persulfate (SPS) for sewage sludge conditioning. The results show that the sewage sludge conditioned with RH and Fe2+/SPS showed good dewaterability, and the capillary suction time was reduced by 92.8% under optimal conditions. With use of response surface methodology, the optimal composite conditioner concentrations were 151.5 mg/g dry solid (DS) of SPS, 46 mg/g DS of Fe2+, and 333 mg/g DS of RH. After the sludge was conditioned with Fe2+/SPS, some extracellular polymeric substances (EPS) were destroyed, which resulted in the dissolved protein and polysaccharide amounts in the filtrate increasing. The water content analysis indicated the bound water was converted to free water because of the EPS degradation. The particle size analysis showed that the sludge flocs became smaller....

Coal bottom ash (CBA) was modified on the basis of the engineering problems of low resource utilization of CBA and difficulty in treating HMS through alkali activation to synthesize geopolymers and solidify heavy metal-contaminated soil (HMS). The optimal values of geopolymers were selected through response surface methodology. Their mineral compositions, microstructure, and binding energy were determined through X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy tests, respectively. The stress–strain curve, the leaching concentration and fraction of heavy metals, and the solidifying mechanism for remolded soil were determined through unconfined compressive strength, leaching toxicity, sequential chemical extraction, and infrared (IR) spectroscopy tests, respectively. Based on these experiments, the following conclusions were presented. The optimum ratios of CBA-based geopolymers were n(Si) : n(Al) = 2.666, n(Na) : n(Al) = 0.687, and n(water) : n(binder) = 2.422. The X-ray curves of the geopolymers were obvious hump-like protuberances at diffraction angles of 20–35° and had a dense amorphous structure on the surface. The maximum binding energies of Si 2p and Al 2p decreased to 101.03 and 72.89 eV, respectively. A 3D network polymerized because of strong geopolymerization. The maximum axial stress of the remolded soil was 104.91% higher than that of the undisturbed soil, and the leaching concentration decreased by more than 45.88%. The leaching toxicity met the requirements of standard GB 5085.3-2007. The proportion of the acid-extractable fraction of heavy metals in the remolded soil decreased, whereas the proportion of residual fraction increased. The stretching vibration of Si–O–Si (Al) and the bending vibration of Si–O–Si appeared in the IR spectrum. The soil particles were completely encapsulated by a hardened geopolymer structure, thereby forming a multilayer space-skeleton barrier structure that could greatly improve the mechanical properties.

This research aimed to address the issue of residual manganese in electrolytic manganese residue (EMR), which is difficult to recycle and can easily become an environmental hazard and resource waste. This research developed a method for the efficient and selective recovery of manganese from EMR and the removal of ammonia nitrogen (ammonium sulfate) under the combined action of ball milling and oxalic acid. The optimum process parameters of this method were obtained through single-factor experiment and response-surface model. Results showed that the recovery rate of manganese can exceed 98%, the leaching rate of iron was much lower than 2%, and the leaching rates of manganese and ammonia nitrogen after EMR ball grinding were 1.01 and 13.65 mg/L, respectively. Kinetics and mechanism studies revealed that ammonium salts were primarily removed in the form of ammonia, and that insoluble manganese (MnO2) was recovered by the reduction of FeS and FeS2 in EMR under the action of oxalic acid. Iron was solidified in the form of Fe2O3 and Fe2(SiO3)3. The technology proposed in this research has great industrial application value for the recycling and harmless treatment of EMR.

Industrial solid waste (ISW) poses a huge potential threat to human health and the environment. To prevent pollution at its source, it is necessary to analyze the socioeconomic drivers and identify the key supply chains that cause changes in ISW generation. In this study, based on monetary input–output tables (MIOTs) in China from 2011 to 2015, structural decomposition analysis (SDA) was used to study the influence of socioeconomic drivers on common industrial solid waste (CISW) and hazardous waste (HW) generation. Structural path decomposition (SPD) was used to further trace the effects of drivers at the supply chain level and obtain more meaningful results for policy formulation. Economic expansion was found to play the most crucial role in the increase in total ISW generation while the reduction of generation intensity effectively slowed the growth trend. From the final demand perspective, fixed capital formation contributed the most to ISW generation growth, accounting for 65.05% of the total final demand effect. Construction was the primary trigger. For CISW, the supply chain with the greatest overall influence was “metal ore mining industry → fixed capital formation” (including intermediate consumption of metal smelting, general and special machinery, and construction), reflecting how fixed capital formation indirectly affected the metal ore mining industry. The supply chain with the greatest influence on HW generation was “paper industry → exports.” Based on the findings, corresponding policy adjustments are proposed.

This study was aimed at removing and stabilizing heavy metals (HgII, ZnII, CuII, and CdII). A novel material (named A-EMS) for heavy metal removal was proposed by ball grinding activated electrolytic manganese slag (EMS) with low content of sodium hydroxide. For different application scenarios, the two physical properties of the materials were developed: the powdery A-EMS (powder) was used to remove heavy metals from wastewater. In addition, the blocky A-EMS (porous brick) was used to build barrier walls for tailings ponds to prevent heavy metals from flowing out. The maximum removal amount of Hg(II) Cd(II), Zn(II), and Cu(II) by A-EMS were 475.35, 77.72, 259.70, and 203.20 mg/g in 30 min. The heavy metals ions were removed and fixed on A-EMS mainly through ion exchange and some forms of electrostatic adsorption and hydroxyl complexation. After consolidating the heavy metals, the compressive strength of the materials can reach 20 Mpa and the leaching toxicity met the national standard of China (GB/T 3838-2002) in 60 days. These excellent properties made A-EMS widely used to remove heavy metals in wastewater and to intercept and solidify heavy metals in mine wastewater.

For evaluating the effect of the blast furnace cinder–based geopolymer solidified pile mud, the relationship of the solidified blocks between the compressive strength and the n(silicon):n(aluminum) (n[Si]:n[Al]), n(sodium):n(aluminum) (n[Na]:n[Al]) and n(water):n(binder) are fitted using the Box–Behnken experimental design, and the optimal values of the solidified block are selected. The mineral compositions, microstructure, and pore structure are determined through X-ray analysis, micromorphology, and static equilibrium adsorption test, respectively. Based on these experiments, the following conclusions are presented. The response surface model can well evaluate the relationship between the compressive strength and multiple factors. The theoretical maximum strength of the block is 1.90 MPa when the n(Si):n(Al), n(Na):n(Al), and n(water):n(binder) are 2.873, 0.706, and 2.329, respectively. The compressive properties of the blocks meet the requirements of the China Standards JTG E30-2005, Test Method of Cement and Concrete for Highway Engineering. Zeolite A, krohnkite, rankinite, sidorenkite, and berthierite are formed through geopolymerization. The dense lamellar particles have disappeared into the microstructure, and the amorphous substances are clearly observed. The isotherms of the pile mud and the solidified blocks belong to Category IV with an H3-type hysteresis loop. The absorbance and the specific surface area (SBET) of the specimen in optimal ratio are 14.24 g/cm3 and 2.314 m2/g, respectively. The total pore volume decreases by 67.19–77.08 %. In the process, Si–O–Si and Al–O–Si are broken down during hydration, and polymers such as Si–O–Na, Si–OH, Al(OH)4−, Al(OH)52−, and Al(OH)63− were formed.

The potential of clay containing 0~5% sewage sludge ash (SSA) is assessed for use as a landfill liner-soil material. Low temperature N2adsorption, batch adsorption, permeability, and unconfined compressive strength tests are performed to evaluate pore structure, adsorption capacity, hydraulic conductivity, and unconfined compressive strength of the clays. The pore size distribution of the modified clay containing SSA is mainly composed of micropores (−8to 2.17 × 10−8 cm/s. At SSA = 3%, the unconfined compressive strength of the clay reaches the maximum value of 601.1 kPa. After the clay containing SSA is contaminated by acid and alkali chemical solutions, the amount of mesopores and hydraulic conductivity increase. The adsorption capacity and unconfined compressive strength of contaminated clay decrease about 2∼44% and 25.7∼38.2%, respectively. The modified clay containing SSA can meet the adsorption and geotechnical requirement of landfill liners.