Study on the leaching toxicity and performance of manganese slag-based cementitious materials

With the rapid development of electrolytic manganese industry, the environmental problems caused by the storage of electrolytic manganese slag are particularly prominent. It not only occupies land resources, but also easily causes heavy metal pollution in soil, surface water and groundwater. Therefore, it is necessary to treat electrolytic manganese slag safely and effectively. The paper mainly studies the solidification / stabilization of electrolytic manganese slag and its environmental safety for road filling, in order to open up a new way of harmless and resource utilization of electrolytic manganese slag. In this paper, lime and fly ash were used as stabilizers and cement was used as curing agent to stabilize manganese slag, and the stabilization effect of Mn and Pb in manganese slag was studied. The stabilization effect of manganese (Mn) and lead (Pb) in manganese slag was studied. The results show that the dosage of stabilizer quicklime is 2.5%, fly ash is 3%, and the dosage of solidifying agent cement is 12%, the solidification/stabilization effect is the best compared with other ratios, then the leaching concentrations of Mn and Pb meets the requirements of China's surface water environmental quality standards for category III water sources, which can be used as domestic water after treatment. Under the optimal ratio of stabilization effect, the compressive strength and slump are 13.8MPa and 50mm, respectively. The research results of the paper can provide a new way for the harmless treatment of manganese slag and the resource utilization of new materials.

Research Status and Environmental Protection Disposal of Recycled Electrolytic Manganese Residue

Electrolytic manganese residue (EMR) is a common industrial solid waste. The ammonia and manganese components contained in it will pollute the soil environment and have potential risks to human health. Under the premise of investigating the production of electrolytic manganese slag and conventional processes, it is found that the traditional harmless treatment methods of electrolytic manganese slag are still mainly lime solidification, cement solidification, and fly ash solidification, and the resource utilization directions such as cement, concrete, non-sintered bricks, road bases, etc. are mainly used. But, EMR contains ammonia nitrogen, and manganese (prone to leaching) that difficult to meeting environmental protection requirements by using general cement cementitious material solidification. Therefore, this study focused on manufacturing new eco-friendly bricks with EMR using calcination process. Specifically, the physical performance and environmental characterization of the sintered bricks were investigated. Furthermore, the sintering behavior and crystallization of all bricks containing EMR were studied using XRD, FT-IR, and SEM. The results showed the EMR leaching solution contained 1256 mg/L and 8120 mg/L of ammonia nitrogen and manganese, respectively, both of them exceeds Chinese standards (GB 8978-1996). Because of EMR is rich in Fe2O3 and K2O, it greatly promotes particle rearrangement and transfer in the EMR system, reducing the sintering temperature. The compressive strength, leaching performance and radioactivity of sintered bricks with EMR all met the state standard requirement for "sintered common bricks" (GB/T 5101-2017) and (GB 8978). The product can be used as bricks of MU20 grade of Chinese standard. The study provides an effective method for the safe and environmentally friendly disposal of EMR.

Re-Use of Silico-Manganese Slag

The world’s rapidly growing demand for raw manganese has made it increasingly important to develop methods for the economic recovery of manganese from secondary sources. The current study aims to present possible ways for the recycling and reuse of silico-manganese slag landfilled in Tulcea, City on the Danube River close to the Danube Delta Biosphere Reserve in order to save the natural resources raw of manganese. In the last three decades, the ferroalloy production plant has over 2.6 million tons of slag. Slag dumping constitutes a significant source of air, water and soil pollution, which adversely affects the environment and human health. Mn present in the slag dump is an environmental pollutant with potentially toxic effects. The results obtained with a leaching method to recover manganese from slag shows two efficient ways to valorize manganese from solid fraction (54%) with size particles between 80 and 315 µm and/or reuse the leaching medium (56% Mn) with a slag size of <80 µm. The motivation of our research is the possibility to recover manganese from slag by saving natural resources of raw of manganese and the remaining fraction can be used as aggregate sources (construction and road rehabilitation by saving extract mineral aggregates and agriculture), in order to decommission the slag dump. The proposed research is in concordance with the sustainable use of natural resources for the achievement of sustainable development of the 2030 Agenda and Waste Management Legislation due of the huge ecological costs regarding non-conforming waste dumping. If we consider the cost-benefit analysis, the environmental future is more important the human health and the benefits on the quality of the population’s health and the environment which are not non-measurable in monetary value.

Analysis of Basic Physical and Chemical Characteristics of Manganese Slag before and after Solidification and Its Feasibility as Highway Slope

Manganese slag is a kind of industrial waste produced by electrolytic production of manganese metal. The traditional method of stacking manganese slag not only causes waste of resources, but also produces environmental pollution. Finding harmless, effective, and economical disposal technology of manganese slag has gradually become a research hotspot and difficulty in the field of electrolytic manganese industry and environmental protection. To verify the feasibility of using manganese slag as roadbed material, the basic physical and chemical properties of manganese slag were analyzed based on X-ray diffraction, X-ray fluorescence spectrum, SEM scanning electron microscope, and particle analysis, the basic engineering characteristics of raw materials of manganese slag and solidified manganese slag mixed with quicklime were analyzed through a compaction test and a CBR test. Finally, based on the Monte Carlo method, the stability of a highway slope in the Guizhou Province of China is simulated by the finite element method, considering the spatial variability of manganese slag material strength parameters. The results show that the solidified manganese slag material can be used as highway subgrade material. This study has important reference significance for manganese slag highway construction projects.

Behavior of Slag in Ferromanganese and Silicomanganese Smelting Process

A review of studies by Safarian et al. and Kim show that the smelting reaction at equilibrium for ferromanganese and silicomanganese alloys is defined by the coupled reaction in the carbon-saturated condition $$ 2\underline{\text{Mn}} + \, \left( {{\text{SiO}}_{ 2} } \right) \, = { 2 }\left( {\text{MnO}} \right) \, + \underline{\text{Si}} $$ 2 Mn ̲ + SiO 2 = 2 MnO + Si ̲ . The behavior of slag at equilibrium is described by MnO and SiO2 as dependent variables and by non-reacting species, CaO, MgO, and Al2O3, as independent variables. Its characteristic behaviors are assessed in the pseudobinary system of MnO and SiO2 fixed by non-reacting components with analyses of ferromanganese and silicomanganese slag from one-month smelting operations. The behavior of fluid slag is defined by their melting temperature provided by phase equilibria of slag system. Liquidus of manganese slag systems by Kang et al., Zhao et al., and Roghani et al. is reconstructed in coordinates of MnO and SiO2 at fixed contents of CaO, MgO, and Al2O3. Conditions for fluid smelting slag are examined by referencing characteristic behaviors of smelting slag to liquidus of manganese slag systems to assess the effect of MgO and Al2O3. MgO facilitates fluid silicomanganese slag but would make ferromanganese slag viscous. Al2O3 makes silicomanganese slag fluid at Al2O3 content with 0.41 by weight ratio to SiO2. At higher contents of Al2O3, silicomanganese slag would be viscous with low MnO contents in slag. Al2O3 facilitates the development of fluid ferromanganese slag.

Utilization of both Electronical Manganese Slag and Silicate Tailings as Raw Materials for Fabrication of Cost-effective Porous Ceramics

Herein, porous wollastonite ceramics with high porosity and low density were successfully fabricated with silicate tailings and electrolytic manganese slag (MS) as primary raw materials. The influences of calcination temperature, SiC and MS addition amounts on porosity, water adsorption, pore distribution, bulk density and bending strength were systematically studied. The results showed that 0.4 wt% of SiC was optimal for the ceramic foaming at the sintering temperature of 1140 ℃. The addition of MS promoted the foaming of ceramic matrix at low temperature. The porosity of ceramics reduced from 78.4–63.7%, bulk density elevated from 0.96 to 1.13 g/cm3, and bending strength increased from 8.43 to 11.22 MPa as the MS increased from 8.33 wt% to 46.67 wt%. Moreover, the best corrosion resistance performance reached to 99.55% with 8.33 wt% MS content and sintering temperature of 1160 ℃. This work is of significance for the solid waste utilization.

Study On Solidification Treatment of Electrolytic Manganese Slag And Numerical Simulation of Slope Stability

Manganese slag contains a large number of easily migrated heavy metals and ammonia nitrogen and other pollutants, which have a negative impact on the ecological environment. To verify the feasibility of manganese slag as highway subgrade material, manganese slag samples were solidified by mixing fly ash, cement and quicklime, and the solidification effect was compared. The permeability coefficient, cohesion and internal friction angle of manganese slag were measured by permeability test and triaxial test. On this basis, optimization of manganese slag road sections under different slope heights and different slope ratios in a total of 50 schemes was carried out. GeoStudio software is used to perform finite element simulation on the slope stability of manganese slag slopes under dead weight and rainfall. This study provides a reference for highway construction projects using manganese slag.