Rhodococcus erythropolis bacterium is known for its remarkable resistance characteristics that can be useful in several biotechnological processes, such as bioremediation. However, there is scarce knowledge concerning the behavior of this strain against different metals. This study sought to investigate the behavior of R. erythropolis ATCC 4277 against the residue of chalcopyrite and e-waste to verify both resistive capacities to the metals present in these residues and their potential use for biomining processes. These tests were carried out in a stirred tank bioreactor for 48 h, at 24ºC, pH 7.0, using a total volume of 2.0 L containing 2.5% (v/v) of a bacterial pre-culture. The pulp density of chalcopyrite was 5% (w/w), and agitation and oxygen flow rates were set to 250 rpm and 1.5 LO2 min-1, respectively. On the other hand, we utilized a waste of computer printed circuit board (WPCB) with a pulp density of 10% (w/w), agitation at 400 rpm, and an oxygen flow rate of 3.0 LO2 min-1. Metal concentration analyses post-fermentation showed that R. erythropolis ATCC 4277 was able to leach about 38% of the Cu present in the chalcopyrite residue (in ~ 24 h), and 49.5% of Fe, 42.3% of Ni, 27.4% of Al, and 15% Cu present in WPCB (in ~ 24 h). In addition, the strain survived well in the environment containing such metals, demonstrating the potential of using this bacterium for waste biomining processes as well as in other processes with these metals.

It is a green and sustainable path to establish cheap solid waste-based catalyst to establish peroxymonosulfate (PMS) catalytic system for the degradation of carbamazepine (CBZ) in water. In this study, durable copper tailing waste residue-based catalyst (CSWR) was prepared, and efficient CSWR/PMS system was constructed for catalytic degradation of CBZ for first time. The morphology and structure of CSWR changed from clumps to porous and loose amorphous by alkali leaching and medium temperature calcination. The reconstructed surface of the CSWR exposes more active sites promotes the catalytic reaction and increases the degradation rate of CBZ by more than 39.8 times. And the CSWR/PMS achieved a CBZ removal of nearly 99.99 % in 20 min. In particular, perovskite-type iron-calcium compounds were formed, which stimulated the production of more HO• and SO4•- in the system. DFT calculation shows that CSWR has stronger adsorption energy and electron transfer ability to PMS molecules, which improved the degradation efficiency of the system. In general, this study proposed a means of high-value waste utilization, which provided a new idea for the preparation of solid waste based environmental functional materials and is expected to be widely used in practical wastewater treatment.

Copper mining has caused serious soil contamination and threaten the balance of underground ecosystem. Effects of metal contamination on the soil microbial community assembly and their multifunctionality are still unclear. In this study, the keystone taxa and microbial metabolic potential of soil microorganisms surrounding a typical copper tailing were investigated. Results showed that pH and metal contents of adjacent soil in copper tailing increased, which largely reduced soil microbial communities\' diversity. Metal contaminated soils enriched a group of keystone taxa with metal-tolerance such as Bacteroidota (20-54%) and Firmicutes (24-48%), which were distinct from the uncontaminated background soils that dominated by Proteobacteria (19-24%) and Actinobacteria (13-24%). In the contaminated soils, these keystone taxa were identified as Alistipes, Bacteroides, and Faecalibacterium, suggesting their adaptation to the metal-rich environment. Co-occurrence network analysis showed that the microbial community was loosely connected in the metal contaminated soils with a lower number of nodes and links. Co-occurrence networks further revealed that the dynamics of keystone taxa significantly correlated with copper content. Functional gene analysis of soil microorganisms indicated that metal contamination might inhibit important microbial metabolic potentials, such as secondary metabolites biosynthesis, carbon fixation, and nitrogen fixation. Results also found the flexible adaptation strategies of soil microbial communities to metal-rich environments with metal-resistance or bio-transformation, such as efflux (CusB/CusF/CzsB and pcoB/copB) and oxidation (aoxAB). These findings provide insight into the interaction between keystone taxa and soil environment, which is helpful to reveal the microbial metabolic potential and physiological characteristics in tailing contaminated soils.

The phyllosphere and rhizosphere of plants and their living environment jointly form a complex ecosystem. Rhizosphere microorganisms are also the main driving force of the circulation of soil materials, which can provide a basis for the growth and development of plants. Phyllosphere and rhizosphere microorganisms can also be used as ecological indicators, and play significant roles in the ecological stability and recovery of mining areas. In this study, we selected a dominant species, Bothriochloa ischaemum, as the research object. We studied the characteristics of phyllosphere and rhizosphere bacterial communities in B. ischaemum from copper tailings with high-throughput sequencing methods. We explored the key ecological factors affecting the structure and diversity of phyllosphere and rhizosphere bacterial communities in B. ischaemum. The results showed that there were significant differences in the bacterial community structures between the rhizosphere and phyllosphere. The dominant phyllosphere bacterial genera of B. ischaemum included Pseudomonas, Enterobacter, and Sphingomonas. The dominant rhizosphere bacterial genera were Acidibacter and Solrubrobacter. Moreover, the Shannon diversity, abundance-based coverage estimator (ACE), and Chao1 indices of rhizosphere bacterial communities were significantly higher than those of phyllosphere communities. The key ecological factors affecting the dominant phyllosphere and rhizosphere bacterial genera included soil water content, pH, soil arsenic and zinc, total nitrogen, and sulfur of B. ischaemum, as well as plant cadmium and chromium. Furthermore, the Shannon diversity indices of rhizosphere bacterial communities were negatively correlated with root copper contents, and Simpson indices were positively correlated with root total nitrogen. There was a significant positive correlation between the ACE index and leaf total sculpture. These results provide a scientific basis for the exploration and utilization of phyllosphere and rhizosphere bacterial resources, and could improve the efficiency of ecological restoration in copper tailings.

There are complex interrelationships between plant microorganisms (phyllosphere and rhizosphere) and host plants, which can promote plant growth and enhance the tolerance of host plants to stress. In this study, we selected the dominant species Bothriochloa ischaemum as the research subject in a copper tailings dam. Using high-throughput sequencing, we investigated the structures of the fungal communities and diversities in the phyllosphere and rhizosphere of B. ischaemum. This study also explored the effects of heavy metal content on fungal community characteristics. The results showed that Ascomycota and Basidiomycota were the dominant phyla in the phyllosphere and rhizosphere of B. ischaemum. The diversities and richness of the rhizosphere fungal community were higher than that of the phyllosphere fungal community. The diversities of rhizosphere and phyllosphere fungal communities was affected by different heavy metals. Phyllosphere fungal diversity was mainly affected by the content of Zn and Cu in leaves, and the content of Pb in roots was the key factor affecting the diversity of the rhizophere fungal community. Furthermore, Pleosporaceae had a very significant positive correlation with Cd in the phyllosphere, and Nectriaceae had a significant positive correlation with Zn in the rhizosphere. These fungal communities could be used as indicators of ecological recovery in areas with heavy metal pollution. The results could provide an ecological basis for the exploration and utilization of phyllosphere or rhizosphere fungi resources during ecological restoration processes. This study also provides guidance for selecting the plant-microbial symbionts during ecological restoration in areas with heavy metal pollution.

With the increasing proportions of copper tailings of concrete in the Qinghai Salt Lake area of China, there arises the problem of corrosion of steel reinforcement in concrete structures. In this study, we determine the corrosion rate (CR), crack width, and corrosion potential of the steel reinforcement with copper tailing. This was achieved by conducting the constant-current accelerated corrosion test with different proportions of copper tailing in the brine environment of the Qinghai province. The results demonstrate that the corrosion potential (Ecorr) and the passivation area of the polarization curve decrease with the increase in the corrosion time, and the corrosion rate and crack width increase with the increase in the corrosion time. When the corrosion time is the same, the corrosion potential, crack width, and corrosion depth of the reinforcement decrease first and then increase with the increase in the copper tailing powder content. When the copper tailing powder content is 20%, the above parameters reach the minimum value. In the salt lake environment of Qinghai, China, the copper tailing powder content is recommended to be 20%.

Heavy metal resistance genes (MRGs) and antibiotic resistance genes (ARGs) in bacteria can respond to the inducement of heavy metals. However, the co-occurrence of MRGs and ARGs in the long-term heavy metal contaminated area is still poorly understood. Here, we investigated the relationship between the abundance of soil bacteria MRGs, ARGs and heavy metal pollution in a copper tailing dam area of northern China. We found that arsC and ereA genes coding for resistance mechanisms to arsenic and to macrolides, respectively, are the most abundant MRG and ARG in the study area. The abundance of MRGs is positively correlated with cadmium (Cd) concentration, and this indicates the importance of Cd in the selection of MRGs. The network analysis results show that sulII and MRGs co-occur and copB occur with ARGs, which suggests that MRGs and ARGs can be co-selected in the soil contaminated by heavy metal. The network analysis also reveals the co-occurrence of Cd and MRGs, and thus heavy metal with a high \'toxic-response\' factor can be used as the indicator of MRGs. This study improves the understanding of the relationship between bacterial resistance and multi-metal contamination, and underlies the exploration of the adaptive mechanism of microbes in the multi-metal contaminated environment.

This study investigates the effect of micr-oaggregate filling with copper tailing on the pore structure of cement paste containing copper tailing (CPCT). The particle size of the CPCT and the pore structure of CPCT were analyzed by laser particle size analysis and mercury instruction porosimetry (MIP). Results showed that at the early stage of curing time, with increasing copper tailing content, the compressive strength of cement mortar with copper tailing (CMCT) was lower, and the porosity and pore diameter of CPCT were higher and greater; with the extension of curing age, when the content of copper tailing was less than 30%, the compressive strength of CMCT and the porosity of CPCT changed slightly with the increase of the content of copper tailing. However, the maximum hole diameter of CPCT decreased gradually (a curing age between 7 d and 365 d under standard conditions). Scanning electron microscopy analysis showed that at the early stage of cement hydration in the CPCT, the copper tailing did not fill the pores in CPCT well, while in the later stage of cement hydration, the microaggregates of copper tailing filled the pores well and closely combined with the surrounding hydration products. In the later stage of cement hydration, the microaggregate filling of copper tailing was primarily responsible for the strength increase of the CMCT.

Mining for metal and mineral resources lead to the rapid rise of tailings dams and caused serious damage to the ecological environment of the mining area. Soil physicochemical characteristics and enzyme activities were important indexes for ecosystem functions, and they were also important factors in evaluating soil restoration qualities. We selected nine sub-dams of the Eighteen River copper tailings in Yuanqu County, and analyzed the relationship between soil physicochemical properties and soil enzyme activities. The results showed that there were great differences in soil physicochemical properties over different reclaimed years, and as the reclaimed years passed, soil nutrient contents significantly increased. There were significant negative correlations between catalase and the ratio of soil carbon and nitrogen, and urease was positively correlated to total nitrogen and soil moisture. Phosphatase and sucrose demonstrated no significant relationships with soil physicochemical factors. Copper content gradually accumulated in soil as the restoration period of sub-dams increased. Arsenic and cadmium content increased initially and then decreased before they gradually reached a stable level. In addition, there was no significant difference in zinc content among different sub-dams. Together, these results provide the ecological basis for further studies in soil ecosystem restoration and degradation mechanisms in copper tailings.