Evaluation of copper tailings from the abandoned Messina Mine for possible reuse in recreational projects, South Africa

Historic mining of copper around Musina Town left behind a sizeable unrehabilitated tailing dump. This article reports on the study conducted to investigate the suitability of using copper tailings as sand replacement in recreational projects. The methodology used involved analyzing the particle size distribution and plasticity index (PI) of the tailings and determining their particle density, bulk density, particle shape, total porosity, and permeability coefficient. The pH of the tailings, major element oxides, and heavy metals composition were all analyzed. The tailings were classified as poorly graded sand with silt (SP-SM). Low fines (9.6%) and PI (1.4) values revealed that the copper tailings were texturally suitable for application in rootzones of sports fields, courts for beach volleyball, and bunkers of the golf courses. Their particle density (2.90 g/cm³), bulk density (1.53-1.89 g/cm³), porosity (34.62-47.04%), and permeability (1.42 x 10-3 cm/sec) were all within the recommended range for application in rootzones. The angular particles of the tailings supported their uses in the bunkers. However, their pH (7.9) and high quartz content (69% SiO2) confirmed their suitability for rootzones. However, the high concentration of Cu (1872.0 mg/kg) and Cr (159.5 mg/kg) was identified as a potential risk of using the copper tailings in rootzones. This and the relatively high Al2O3 (11%) and Fe2O3 (8%) suggested that the copper tailings should be first washed or processed before being used in any recreational projects. Developing a suitable technique for processing the studied copper tailings to enhance their properties for different recreational projects was recommended.

Image Analysis Technology in the Detection of Particle Size Distribution and the Activity Effect of Low-Silicon Copper Tailings

To speed up the comprehensive utilization and treatment of copper tailings, the digital image processing technology is proposed in this study to detect the low-silicon copper tailings (LSCT) using a scanning electron microscope (SEM), and the particle size distribution (PSD) and the activity of LSCT are analysed under the action of mechanical force. Firstly, the current status and application of copper tailings are introduced, and the influence of the particle size of LSCT on its practical application performance is explained. Secondly, the LSCT SEM image target recognition model is designed based on the convolutional neural network (CNN), and the model parameters and the reference CNN are selected. Finally, the experimental process is designed, a SEM image data set of LSCT is prepared, the model is trained through the training set, and the image recognition test is performed on the produced data set. The experimental results show that when the number of iterations of the CNN is 10, the accuracy of model recognition can be guaranteed. After the action of mechanical force, the PSD of LSCT is mainly concentrated at 1 μm~100 μm; that around 1.4 μm~10 μm is the largest, and the PSD of LSCT around 1.4 μm increases with the increase of action time of mechanical force, but the PSD of the LSCT begins to increase when the grinding time exceeds 150 minutes, and the activity of LSCT reaches the maximum (75.545%) at 150 minutes. The average accuracy of SEM image detection of the model is 86.97%, and the model based on DenseNet shows better recognition accuracy than other models. This study provides a reference for analysing the PSD of LSCT.

Methodologies for the Possible Integral Generation of Geopolymers Based on Copper Tailings

It is of interest to study the use of copper tailings as a raw material to generate geopolymers due to the exorbitant amounts of existing tailings deposits, which also produce different risks to nearby communities. Therefore, using this industrial waste as construction material would result in several environmental and economic benefits. Due to the above, it is necessary to perform laboratory tests that account for the relevant variables to obtain fresh geopolymer pastes with good consistency, and to obtain hardened geopolymers with good mechanical strength. This report gives an account of the experimental work carried out in the laboratory of the CIMS Sustainable Mining Research Center of the Engineering Consulting Company JRI, exposing the preliminary results observed in the generation of geopolymers by means of seven different methods using copper tailings and NaOH. Of the seven methods evaluated in the laboratory, it was observed that two of them deliver better results from a qualitative point of view, where the influence of the curing stage stands out, reflecting that temperature is one of the critical variables for the formation of geopolymers based on copper tailings and NaOH. The best means to work the mixtures should be studied to optimize the solubility of the NaOH and, therefore, the dissolution of the aluminosilicates in the tailings.

Phosphorus-Induced Adaptation Mechanisms of Rye Grown on Post-Flotation Copper Tailings

Although a considerable effort has been made over the last decades to develop cost-effective phytotechnologies as an alternative to conventional techniques for the management of contaminated lands, successful revegetation of the tailings still represents a major challenge. Here, we evaluate the potential of rye (Secale cereale L.) for growth and survival on the tailings after copper (Cu) ore processing. Four rye varieties were cultivated in a pot experiment on the post-flotation sediment with increasing phosphorus (P) doses (22, 44, 66, 88, and 110 mg·kg−1). The resistance of the studied rye genotypes to stress was assessed by observing the growth and development of plants, determining the dry mass accumulation, the Cu and P uptake and content, and a number of physiological parameters related mainly to P mobilisation. Exposure of tested rye varieties to high Cu concentrations in the tailings did not result in any significant plant mortality, with the intracellular Cu concentrations being below the critical toxic level. In contrast, the low availability of P due to alkaline properties of the tailings and the mechanisms involved in the mobilisation of sparingly soluble forms of this element (i.e., H+-ATPase-driven proton efflux in roots and organic acid exudation), were identified as main factor determining the level of tolerance. The efficiency of the photosynthetic activity was a key determinant for the P-mobilising capacity of rye. We further showed that rye varieties with more primitive genetic background might be potentially more suitable for growth on the post-flotation copper tailings. The results provide important and novel knowledge that will certainly support future works in developing strategies for successful revitalisation of degraded lands.

Characterization of Copper Tailings In Murgul Copper Plant (Artvin/Turkey) And Utilization Potential In Cement Mortar With Nano And Micro Silica

Due to the increasing demand for copper day by day, copper tailings (CT) are the wastes that mining and human-induced activities caused have become a problem all over the world due to the increasing demand for copper. This study evaluates the effect of using CT together with nano silica (NS) and micro silica (MS) in mortars as a partial substitution for cement on mechanical strength properties. Physical, morphological, chemical, mineralogical thermo gravimetric analyzes of CT have been made. In addition, heavy metal concentrations were determined. The mechanical features of the mortars produced by replacing by weight with different proportions of (5%, 10%, 15%) CT, 2% NS and 10% MS cement were determined. As a result, it has been observed that the sum of SiO2, Al2O3 and Fe2O3 of the CT, which has a mostly crystalline structure, is 91.40% and its ignition loss is 4.04%. An improvement in compressive strength (compared to the reference mixture) was observed with the use of 5% CT. Up to 10% of CT has provided standard compressive strength values in both NS and MS combinations.

Feasibility Evaluation of Replacing River Sand with Copper Tailings

This study aims to realize the resource regeneration application of copper tailing (as fine aggregates for partial replacement of natural fine aggregates), which avoid environmental pollution due to many landfills of copper tailings. The compressive strength and durability (dry shrinkage and sulfate attack) tests were carried out to evaluate the effect of copper tailings replacement on the performance of mortar. The results show that the mortar with copper tailings has higher compressive strength than the one with natural sand. More than 14% improvement in compressive strength can be achieved by adding copper tailings with no more than 40% replacement level. The dry shrinkage of mortar was increased with the copper tailings due to the increase of micro pores in mortar by using copper tailings. Compared with the mortar with natural sand, the dry shrinkage can be reduced by adding copper tailings with no more than 20% replacement level. The sulfate attack resistance is improved by using copper tailings, when the replacement rate is more than 20%. In fact, the micro-aggregate filler effect of copper tailings effectively refines the pore structure and forms more stable, uniform and fine interface micro pores, which is of vital significance for mortar to resist external forces and sulfate ion erosion. However, copper tailings, as a porous material, have water release characteristics in cement mortar. This characteristic is not conducive to the filler effect, which decreases the filling rate in later hydration, leading to higher porosity of copper tailings mortar. More importantly, mortar can solidify heavy metals in copper tailings, which prevents loss of heavy metal such as Cu, Zn, Sr, Zr, As, Ga due to environmental problems.