Simultaneous immobilization of NH4+ and Mn2+ from electrolytic manganese residue using phosphate and magnesium sources

Study on harmless treatment of electrolytic manganese residue by low temperature thermochemical method

The Electrolytic Manganese Residue (EMR) is a by-product of the electrolytic manganese metal (EMM) industry, containing high concentrations of potential pollutants such as NH4+-N and soluble Mn2+. These components pose a serious threat to the ecological environment. To explore accurate, efficient, and harmless treatment methods for EMR, this study proposes a low-temperature thermochemical approach. The orthogonal experiment design investigates the effects of reaction temperature, reaction time, quicklime (CaO), sodium carbonate (Na2CO3), sodium phosphate (Na3PO4) (Reviewer #3), and water consumption on manganese solidified and ammonia removal from EMR. The results indicate that optimal conditions are a reaction temperature of 60 ℃ (Reviewer #3) and a reaction time of 10 min. CaO precipitates Mn2+ as manganese hydroxide (Mn(OH)2) (Reviewer #3), achieving effective manganese solidified and ammonia removal. The addition of Na2CO3 causes Mn2+ to form manganesecarbonate (MnCO3) (Reviewer #3)precipitate, while Na3PO4 makes Mn2+ form Manganese phosphate trihydrate (Mn3(PO4)2·3H2O) (Reviewer #3). Increased water consumption enhances the interaction adequacy between ions. Under optimal conditions (CaO 10%, Na2CO3 1%, Na3PO4 0.5%, and 80% water consumption), the removal rate of ammonium ions reaches 98.5%, and the solidification rate of soluble Mn2+ is 99.9%. The order of influence on ammonium ion removal is CaO > water consumption > Na3PO4 > Na2CO3. Therefore, this study provides a new method for low-cost process disposal and efficient harmless treatment of EMR (Reviewer #3).

Ammonia removal and simultaneous immobilization of manganese and magnesium from electrolytic manganese residue by a low-temperature CaO roasting process

A large amount of open-dumped electrolytic manganese residue (EMR) has posed a severe threat to the ecosystem and public health due to the leaching of ammonia (NH4+) and manganese (Mn). In this study, CaO addition coupled with low-temperature roasting was applied for the treatment of EMR. The effects of roasting temperature, roasting time, CaO-EMR mass ratio and solid-liquid ratio were investigated. The most cost-effective and practically viable condition was explored through response surface methodology. At a CaO: EMR ratio of 1:16.7, after roasting at 187 °C for 60 min, the leaching concentrations of NH4+ and Mn dropped to 10.18 mg/L and 1.05 mg/L, respectively, below their discharge standards. In addition, the magnesium hazard (MH) of EMR, which was often neglected, was studied. After treatment, the MH of the EMR leachate was reduced from 60 to 37. Mechanism analysis reveals that roasting can promote NH4+ to escape as NH3 and convert dihydrate gypsum to hemihydrate gypsum. Mn2+ and Mg2+ were mainly solidified as MnO2 and Mg(OH)2, respectively. This study proposes an efficient and low-cost approach for the treatment of EMR and provides valuable information for its practical application.

Study of microscopic properties and heavy metal solidification mechanism of electrolytic manganese residue-based cementitious materials

Electrolytic manganese residue (EMR) is a solid waste that contains a significant amount of soluble manganese and ammonia nitrogen, which can pose risks to human health if improperly disposed of. This study aimed to prepare cementitious materials containing abundant ettringite crystals by mixing EMR with various proportions of granulated blast furnace slag (GBFS) and alkaline activators (CaO, Ca(OH)2, clinker, NaOH). The resulting cementitious material not only utilized a substantial amount of EMR but also exhibited comparable strength to ordinary Portland cement. The optimal ratios were determined through mechanical testing. Additionally, the leaching toxicity of cementitious materials was assessed using ICP-MS (inductively coupled plasma mass spectrometer) tests. The microscopic properties, hydration, and mechanism of heavy metal solidification in the cementitious materials were evaluated using XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy-dispersive spectrometer), FTIR (Fourier transform infrared spectroscopy), and TG (thermogravimetric) techniques. The results showed that the optimal ratio for the cementitious materials was 60% EMR, 36% GBFS, and 4% Ca(OH)2. The hardened mortar exhibited compressive strengths of 34.43 MPa, 41.3 MPa, and 50.89 MPa at 3 days, 7 days, and 28 days, respectively, with an EMR utilization rate of 60%. The hydration products of EMR-based cementitious materials were C-(A)-S-H, AFt, and ferromanganese compounds, which contribute to the mechanical strength. The Mn2+ and NH4+-N contents of raw EMR were 1220 and 149 mg/L, respectively. Nonetheless, the leaching of Mn2+ and NH4+-N in the alkali-EMR-GBFS system was significantly below the limits set by the Chinese emission standard GB8978-1996. Within this system, C-(A)-S-H and AFt could physically adsorb and displace heavy metals, Ca6Mn2(SO4)2(SO3)2(OH)12·24H2O could replace Al ions with Mn ions, and ferromanganese compounds Fe2Mn(PO4)2(OH)2·(H2O)8 and MnFe2O4 could chemically precipitate Mn2+.

Water column leaching recovery manganese and ammonium sulfate from electrolytic manganese residue: extremely low water consumption toward practical applications

Regional contamination by electrolytic manganese residue (EMR) not only composes a serious environmental problem but also leads to severe valuable resources waste. Directly recovering manganese and ammonium sulfate is a promising way, but it is still challenging to efficiently recover without high water consumption. Herein, a recovery method based on water column leaching under extremely low water consumption was firstly reported. The effect of continuous leaching and intermittent leaching on leaching behaviors, leaching trends, and spatial variations of (NH₄)₂SO₄ and Mn with depth after leaching were fully investigated. Results indicated that some Mn-bearing soluble salts which covered on the surface of SiO₂ in the micropores could be fully dissolved and transported out of the micropores in the EMR with the help of rest periods in the method of intermittent leaching, resulting in higher leaching efficiencies with comparison to continuous leaching, 73.50% of Mn and 67.71% of (NH₄)₂SO₄ and 71.57% of Mn and 65.40% of (NH₄)₂SO₄ were recovered by intermittent leaching and continuous leaching, respectively. This work demonstrates a practical approach to recover valuable materials from industrial solid wastes.

Electrolytic manganese residue disposal based on basic burning raw material: Heavy metals solidification/stabilization and long-term stability

Solidification/stabilization (S/S) is an option for the treatment of electrolytic manganese residue (EMR). Basic burning raw material (BRM) could successfully solidify/stabilize EMR, though heavy metals S/S mechanism and long-term stability remain unclear. Herein, Mn²⁺ and NH₄⁺ S/S behavior, hydrated BRM and S/S EMR characterization, Mn²⁺ long-term leaching behavior, phase and morphology changes for long-term leaching were discussed in detail to clarify these mechanisms. Mn²⁺ and NH₄⁺ leaching concentrations as well as pH value in S/S EMR were respectively 0.02 mg/L, 0.68 mg/L and 8.75, meeting the regulations of Chinese standard GB 8978-1996. Long-term stability of EMR was significantly enhanced after S/S. Mn²⁺ leaching concentration, Mn²⁺ migration, Mn²⁺ cumulative release, Mn²⁺ apparent diffusion coefficient and conductivity of EMR reduced to 0.05 mg/L, 5.5 × 10^-6 mg/(m²·s), ~ 9 mg/m², 6.30 × 10^-15 m²/s and 435 μs/cm. Mechanism studies showed that the hydration of BRM forms OH^-, calcium silicate hydrate gels (C-S-H) and ettringite. Therefore, during S/S process, NH₄⁺ was escaped as NH₃, Mn²⁺ was solidified/stabilized as tephroite (Mn₂SiO₄), johannsenite (CaMnSi₂O₆) and davreuxite (MnAl₆Si₄O₁₇(OH)₂), and Pb²⁺, Cu²⁺, Ni²⁺, Zn²⁺ were solidified/stabilized by C-S-H and ettringite via substitution and encapsulation. This study provides a good choice for EMR long-term stable storage.

Synergistic solidification/stabilization of electrolytic manganese residue and carbide slag

Electrolytic manganese residue (EMR) contains high concentrations of NH₄⁺ and heavy metals, such as Mn²⁺, Zn²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Co²⁺, while carbide slag (CS) contains high amount of OH^- and CO₃^2-, both posing a serious threat to the ecosystem. In this study, EMR and CS synergistic stabilization/solidification (S/S) was discussed science CS could stabilize or solidify EMR and simultaneously reduce its corrosive. The results showed that after the synergistic S/S for 24 h when liquid-solid ratio was 17.5% and CS dosage was 7%, Mn²⁺ and NH₄⁺ leaching concentrations of the S/S EMR were below the detection limits (0.02 mg/L and 0.10 mg/L) with a pH value of 8.8, meeting the requirements of the Chinese integrated wastewater discharge standard (GB 8978-1996). Mn²⁺ was stabilized as MnFe₂O₄, Mn₂SiO₄, CaMnSi₂O₆, and NH₄⁺ escaped as NH₃. Zn²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Co²⁺ in EMR can also be stabilized/solidified because of the react with OH^- and CO₃^2- in CS. Chemical cost was only $ 0.54 for per ton of EMR synergistic harmless treatment with CS. This study provided a new idea for EMR cost-effective and environment-friendly harmless treatment.

The Mechanical and Tribological Properties of Epoxy-Based Composites Filled with Manganese-Containing Waste

Waste from large-scale production processes is a growing environmental problem that can potentially be solved by using this waste as fillers in polymeric composites to improve the mechanical and tribological properties of polymeric matrixes. This paper presents research concerning how the introduction of fillers in the form of manganese residue and manganese(II) oxide changes the mechanical and tribological properties of epoxy composites produced by gravity casting. The research was carried out for composites with 2.5 wt.%, 5 wt.%, and 10 wt.% of fillers. Properties such as the density, hardness, resilience, flexural strength, deflection, flexural modulus, tensile strength, elongation at break, and Young's modulus were determined. Moreover, based on the ball-on-plate test, the wear volume and friction coefficients of the tested materials were determined. Microscopic images of the abrasion profiles were also obtained. The geometry of the wear paths was measured with a profilometer, and the results showed that introducing fillers reduced the abrasive wear of the composites; however, in all cases, the fillers decreased the strength of the tested materials.

Multi-step purification of electrolytic manganese residue leachate using hydroxide sedimentation, struvite precipitation, chlorination and coagulation: Advanced removal of manganese, ammonium, and phosphate

Water pollution caused by the release of manganese (Mn²⁺) and ammonia nitrogen (NH₄⁺-N) from electrolytic manganese residue (EMR) generated from industrial activities poses a serious threat to ecosystems and human health. In this study, an integrated process consisting sequentially of hydroxide sedimentation, struvite precipitation, breakpoint chlorination, and ferric chloride coagulation was optimized to remove Mn²⁺ and NH₄⁺-N from EMR leachate, and to address the issue of residual orthophosphate caused by struvite precipitation. The precipitates were characterized using X-ray diffraction, scanning electron microscopy, and thermogravimetric analyses. Results show that Mn²⁺ ions and the resulting chemical oxygen demand (COD) were mainly removed using hydroxide precipitation at a sedimentation pH of 10.2, with poor-crystalline manganese hydroxide as the main precipitate. NH₄⁺-N was primarily removed and recovered using struvite precipitation with well crystalline struvite as the main product, and then further eliminated using breakpoint chlorination. The residual orthophosphate introduced by struvite precipitation is successfully removed with ferric coagulation, and the effluent pH (7.5) is also lowered to discharge limits by means of hydrolysis of ferric coagulant. The concentration of COD, Mn²⁺, NH₄⁺-N, and orthophosphate concentrations in the final effluent were 30.52 ± 9.38, 0.026 ± 0.013, 0.87 ± 0.01, and 0.06 ± 0.002 mg/L, respectively, meeting all local discharge standards. This combined process has robust pollutant removal efficiency, high resource recovery potential and few environmental constraints; thus, it is recommended as a potential solution for the treatment of Mn²⁺- and NH₄⁺-N-rich acid mine drainage.

A critical review on approaches for electrolytic manganese residue treatment and disposal technology: Reduction, pretreatment, and reuse

Electrolytic manganese residue (EMR) has become a barrier to the sustainable development of the electrolytic metallic manganese (EMM) industry. EMR has a great potential to harm local ecosystems and human health, due to it contains high concentrations of soluble pollutant, especially NH₄⁺ and Mn²⁺, and also the possible dam break risk because of its huge storage. There seems to be not a mature and stable industrial solution for EMR, though a lot of researches have been done in this area. Hence, by fully considering the EMM ecosystem, we analyzed the characteristics and eco-environmental impact of EMR, highlighted state-of-the-art technologies for EMR reduction, pretreatment, and reuse; indicated the factors that block EMR treatment and disposal; and proposed plausible and feasible suggestions to solve this problem. We hope that the results of this review could help solve the problem of EMR and thus promote the sustainable development of EMM industry.

A low cost of phosphate-based binder for Mn2+ and NH4+-N simultaneous stabilization in electrolytic manganese residue

Electrolytic manganese residue (EMR) is a solid waste remained in filters after using sulfuric acid to leaching manganese carbonate ore. EMR contains high concentration of soluble manganese (Mn²⁺) and ammonia nitrogen (NH₄⁺-N), which seriously pollutes the environment. In this study, a low cost of phosphate based binder for Mn²⁺ and NH₄⁺-N stabilization in EMR by low grade-MgO (LG-MgO) and superphosphate was studied. The effects of different types of stabilizing agent on the concentrations of NH₄⁺-N and Mn²⁺, the pH of the EMR leaching solution, stabilizing mechanisms of NH₄⁺-N and Mn²⁺, leaching test and economic analysis were investigated. The results shown that the pH of the EMR leaching solution was 8.07, and the concentration of Mn²⁺ was 1.58 mg/L, both of which met the integrated wastewater discharge standard (GB8978-1996), as well as the concentration of NH₄⁺-N decreased from 523.46 mg/L to 32 mg/L, when 4.5 wt.% LG-MgO and 8 wt.% superphosphate dosage were simultaneously used for the stabilization of EMR for 50 d Mn²⁺ and NH₄⁺-N were mainly stabilized by Mn₃(PO₄)₂·2H₂O, MnOOH, Mn₃O₄, Mn(H₂PO₄)₂·2H₂O and NH₄MgPO₄·6H₂O. Economic evaluation revealed that the treatment cost of EMR was $ 11.89/t. This study provides a low-cost materials for NH₄⁺-N and Mn²⁺ stabilization in EMR.