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Electrolytic manganese metal residue (EMMR) harmless treatment has always lacked a low-cost and quick processing technology. In this study, surfactants, namely tetradecyl trimethylammonium chloride (TTC), sodium dodecyl benzene sulfonate (SDBS), sodium lignin sulfonate (SLS), and octadecyl trimethylammonium chloride (OTC), were used in the solidification of Mn2+ and removal of NH4+-N from electrolytic manganese metal residue (EMMR). The Mn2+ and NH4+-N concentrations under different reaction conditions, Mn2+ solidification and NH4+-N removal mechanisms, and leaching behavior were studied. The results revealed that the surfactants could enhance the Mn2+ solidification and NH4+-N removal from EMMR, and the order of enhancement was as follows: TTC ＞ SDBS ＞ OTC ＞ SLS. The NH4+-N and Mn2+ concentrations were 12.3 and 0.05 mg/L with the use of 60.0 mg/kg TTC under optimum conditions (solid-liquid ratio of 1.5:1, EMMR to BRM mass ratio of 100:8, temperature of 20 ℃, and reaction duration of 12 h), which met the integrated wastewater discharge standard (GB8978-1996). Mn2+ was mainly solidified as Mn(OH)2, MnOOH and MnSiO3, and NH4+-N in EMMR was mostly removed in the form of ammonia. The results of this study could provide a new idea for cost-effective EMMR harmless treatment.

Electrolytic manganese anode slime (EMAS) contains many Mn resources, and efficient Mn leaching is the key to realizing its high-value utilization. In this study, the effects of Fe2+ concentration,...

Electrolytic manganese anode slime (EMAS) is produced during the production of electrolytic manganese metal. In this study, a method based on vacuum carbothermal reduction was used for Pb removal in EMAS. A Pb-removal efficiency of 99.85% and MnO purity in EMAS of 97.34 wt.% was obtained for a reduction temperature of 950°C and a carbon mass ratio of 10% for a holding time of 100 min. The dense structure of the EMAS was destroyed, a large number of multidimensional pores and cracks were formed, and the Pd-containing compound was reduced to elemental Pb by the vacuum carbothermal reduction. A recovery efficiency for chemical MnO2 of 36.6% was obtained via preparation from Pd-removed EMAS through the “roasting-pickling disproportionation” process, with an acid washing time of 100 min, acid washing temperature of 70°C, H2SO4 concentration of 0.8 mol/L, liquid-solid mass ratio of 7 mL/g, calcination temperature of 60°C and calcination time of 2.5 h. Moreover, the crystal form of the prepared chemical MnO2 was found to be basically the same as that of electrolytic MnO2, and its specific surface area, micropore volume and discharge capacity were all higher than that of electrolytic MnO2. This study provides a new method for Pd removal and recycling for EMAS.

Electrolytic manganese residue (EMR) contains high concentrations of NH

Electrolytic manganese residue (EMR) contains large quantities of manganese (Mn2+) and ammonia nitrogen (NH4+-N). Phosphogypsum (PG) contains plenty of phosphate (PO43−), fluorine (F−) and some heavy metals. Separate storage of EMR and PG could seriously damage the ecological environment. In this study, synergistic stabilization/solidification (S/S) of EMR and PG was studied. The effects of EMR:PG mass ratio, S/S pH, solid-liquid ratio and temperature on the concentrations of NH4+-N, PO43−, Mn2+ and F− in the leaching solution, and the characteristics of EMR and PG were studied. Meanwhile, the synergistic S/S mechanisms of EMR and PG, and leaching test were investigated. The results showed that the concentrations of F−, PO43−, NH4+-N and Mn2+ in the leaching solution were 4.5 mg/L, 13.6 mg/L, 55.5 mg/L and 0.8 mg/L, respectively, when the mass ratio of EMR to PG was 1:2 and the pH was 9.0 adjusted by MgO after 20 days S/S. Manganese was mainly solidified as Mn3(PO4)2·7H2O and Mn(OH)2, and ammonia nitrogen was mainly stabilized as struvite; fluorine was mainly stabilized as (Mn, Ca, Mg)F2, and phosphate was mainly solidified as (Mn, Ca, Mg)3(PO4)2 and (Mn, Ca, Mg)HPO4. The leaching test results showed that PO43− and NH4+-N were reduced to 13.6 mg/L and 55.5 mg/L, respectively, and the concentrations of all the measured heavy metals and F− were within the permitted level for the GB8978-1996 after 20 days S/S.

Electrolytic metal manganese residue leachate (EMMRL) was produced from long-term deposition of electrolytic metal manganese residue. EMMRL contains huge amount of manganese and ammonia nitrogen which could seriously damage the ecological environment. In this study, a chemical equilibrium model-Visual MINTEQ was used to simultaneously optimize removal of manganese and ammonia nitrogen from EMMRL with chemical precipitation methods. In the laboratory experiment, the effect of different N: P ratios and pH were investigated, and the characterization of the precipitates was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The results showed that over 99.9% manganese and 96.2% ammonia nitrogen were simultaneously removed, respectively, when molar ratio of N:P was 1:1.15 at pH 9.5. Moreover, the experimental results corresponded well with the model outputs with respect to ammonia nitrogen and manganese removal. Manganese was mainly removed in the form of MnHPO4·3H2O and manganite, and ammonia nitrogen was mainly removed in the form of struvite. Economic evaluation indicated the chemical precipitation methods can be applied in the factory when the price of precipitation was higher than 0.295 $/kg.

A comparative investigation of hydroxide precipitation, sulfide precipitation, carbonate precipitation and the struvite formation process for removing manganese and ammonia nitrogen from electrolytic metal manganese residue leachate (EMMRL) was investigated. Chemical equilibrium model-Visual MINTEQ was applied to simulate the chemical reactions and optimize chemical dosages in manganese and ammonia nitrogen removal. Phase transition, morphology, and valence state of the precipitates were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray Photoelectron Spectroscopy (XPS). Results indicated that carbonate precipitation prior to the other two methods for removal of manganese and ammonia nitrogen. The removal efficiency of manganese was 99.9%, when molar ratio of C to Mn was 1.1:1 at pH 9.5, and manganese was removed in the form of MnCO3. When molar ratio of P to N was 1.1:1 at pH 9.5, the removal efficiency of ammonia nitrogen was 97.4%, and ammonia nitrogen was removed in the form of struvite. Economic evaluation reveals that the treatment cost was 9.316 $ m−3 when carbonate and phosphate was used to remove manganese and ammonia nitrogen from EMMRL.

Electrolytic manganese residue (EMR) is a solid waste generated in the process of producing electrolytic metal manganese and contains a lot of manganese and ammonia nitrogen. In this study, electrokinetic remediation (EK) of manganese and ammonia nitrogen from EMR were carried out by using pulse electric field (PE) in different agents, and sodium dodecyl benzene sulfonate (SDBS), citric acid (CA) and ethylene diamine tetraacetic acid (EDTA) were used as enhancement agents. The removal behavior of ammonia nitrogen and manganese under direct current field (DC) and PE, and the relationship between manganese fractionation and transport behavior, as well as the energy consumption were investigated. The results demonstrated that the removal efficiency of ammonia nitrogen and manganese using PE were higher than DC. SDBS, EDTA and CA could enhance electroosmosis and electromigration, and the sequence of enhancement agent effects were CA, SDBS, EDTA, distilled water. The highest removal efficiency of manganese and ammonia nitrogen were 94.74% and 88.20%, and the effective removal amount of manganese and ammonia nitrogen was 23.93 and 1.48 mg·wh−1, when CA and SDBS+CA was used as the enhancement agents, respectively. Moreover, electromigration was the main removal mechanism of manganese and ammonia nitrogen in the EK process.

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.

In this study, electric field and ball milling were used to leach Mn2+ from low-grade pyrolusite (LGP). The effects of current density, reaction time, reaction temperature, ball-to-powder weight ratio, and ball milling time on the leaching efficiency of Mn2+ from LGP as well as the leaching mechanism were systematically studied. The results showed that the combined use of electric field and ball milling enhanced the leaching of Mn2+ from LGP. The leaching efficiency of Mn2+ reached 97.79% under the optimum conditions of LGP-to-pyrite mass ratio of 1:0.18, current density of 30 mA/cm2, LGP-to-H2SO4 mass ratio of 1:0.4, liquid-to-solid ratio of 5:1, ball-to-powder weight ratio of 1:1, ball milling time of 2 h, temperature of 80 °C, and leaching duration of 120 min. This value was 25.95% higher than that attained without ball milling and 41.45% higher than that attained when neither ball milling nor electric field was employed. Pyrite was fully oxidized to generate additional SO42− and Fe3+, and was further hydrolyzed to form jarosite (KFe3(SO4)2(OH)6) and hydronium jarosite (Fe3(SO4)2(OH)5·2H2O) via ball milling and electric field application. Moreover, the electric field changed the surface charge distribution of the mineral particles and promoted collisions between them as well as the collapse of the crystal lattice, further improving the leaching efficiency of Mn2+ from LGP. This study provided a new method for leaching Mn from LGP.

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 (Mn

In industrial electrolytic manganese metal process, the energy consumption closely related to the electrolysis of cathode and anode. The effect of Cl- concentration on electrochemical oscillation a...

In this study, a new electrochemical method was used to simultaneously efficient removal of Mn

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, Mn

This study examined simultaneous stabilization and solidification (S/S) of Mn2+ and NH4+-N from electrolytic manganese residue (EMR) using MgO and different phosphate resource. The characteristics of EMR NH4+-N and Mn2+ S/S behavior, S/S mechanisms, leaching test and economic analysis, were investigated. The results show that the S/S efficiency of Mn2+ and NH4+-N could reach 91.58% and 99.98%, respectively, and the pH value is 8.75 when the molar ratio of Mg:P is 3:1 and the dose of PM (MgO and Na3PO4·12H2O) is 8wt%. In this process, Mn2+ could mainly be stabilized in the forms of Mn(H2PO4)2·2H2O, Mn3(PO4)2·3H2O, Mn(OH)2, and MnOOH, and NH4+-N in the form of NH4MgPO4·6H2O. Economic evaluation indicates that using PM process has a lower cost than HPM and HOM process for the S/S of Mn2+ and NH4+-N from EMR at the same stabilization agent dose. Leaching test values of all the measured metals are within the permitted level for the GB8978-1996 test suggested when the dose of PM, HPM and HOM is 8wt%.

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore. In this work, modified electrolytic manganese residue (MEMR) as a high-efficiency adsorbent for the removal of methylene blue (MB) was synthesized via hydrothermal method. The characterizations of MEMR were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption/desorption isotherms, and scanning electron microscope. The results showed that with the BET specific surface area of 500.8 m2/g the MEMR reached the maximum adsorption capacity (548.15 m2/g) within 50 min when the pH of initial solution was 6.05 and the initial concentration of MB was 1600 mg/L. The adsorption kinetics and equilibrium isotherms were accurately described by the pseudo-second-order model and Langmuir isotherm, respectively. The FTIR spectra indicated that electrostatic attraction and stacking interaction were the main adsorption mechanisms. Thermodynamic analyses showed that the adsorption of MB on MEMR was a spontaneous and exothermic physisorption process. This study revealed that MEMR can be used as a low cost and eco-friendly potential adsorbent for removing MB from wastewater.

Electrolytic manganese anode slime (EMAS) is a kind of waste produced by anode chambers in the process of electrolytic manganese production. In this study, the surface of EMAS was hydroxylated with EDTA-2Na, and a new adsorbent for removing methylene blue (MB) was obtained. The hydroxylation of EMAS (H-EMAS) was characterized by XRD, XRF, FTIR, BET, SEM and XPS. The results showed that H-EMAS contains many pores and cracks and that the specific surface area of H-EMAS was 53.17 m2/g. The maximum adsorption capacity of H-EMAS for MB was 70.74 mg/g when the initial pH was 6.00, the initial MB concentration was 500 mg/L, the reaction time was 120 min and the reaction temperature was 298 K. Adsorption kinetics and isotherms showed that the adsorption of MB on H-EMAS conformed to pseudosecond-order kinetic model and Langmuir isotherm, respectively. Thermodynamic analysis showed that the adsorption process was a spontaneous and exothermic physical adsorption process. Moreover, H-EMAS adsorbent recycling showed that the adsorption capacity of H-EMAS was 55.35 mg/g after four cycles and that the adsorption efficiency for MB only decreased by 21.75%. This study provides a new method for the resource utilization of EMAS.

Electrolytic manganese anode slime (EMAS) is a solid waste found in the anode chamber during the production of electrolytic manganese metal, which mainly contains high concentration of manganese and other impurities. In EMAS, γ-MnO2 and δ-MnO2 turned into α-MnO2 after calcination, and the oxide can be dissolved by pickling. The results showed that the specific surface area of EMAS increased from 33.11 m2·g− 1 to 93.53 m2·g− 1, and the micropore volume increased from 0.0129 cm3·g− 1 to 0.0362 cm3·g− 1, as well as the specific capacity and the Open Circuit Voltage (OCV) of EMAS were 249.65 mAh·g− 1 and 1.60 V, respectively, under the condition of calcination temperature 400 °C, calcination time 1 h, sulfuric acid 1 mol·L− 1, pickling temperature 25 °C, pickling time 0.5 h, and liquid-to-solid ratio 8:1.

In this study, a new combination method for Mn2+ and NH4+-N removal from electrolytic manganese metal residue (EMMR) using washing and electrolytic oxidation processes was studied. The effects of washing pH, the dosage of sodium hypochlorite, current density, reaction time and reaction temperature on the concentrations of Mn2+ and NH4+-N were investigated. The results showed that the concentrations of NH4+-N and Mn2+ were 6.79 mg/L and 0.05 mg/L, respectively, which were lower than the integrated wastewater discharge standard (GB8978-1996), when the current density was 35 mA/cm2, the sodium hypochlorite dosage was 2%, and the initial pH was 9.5 after reacting for 2 h at 20℃. Mn2+ was mainly removed in the forms of MnO2, Mn2O3, MnOOH and Mn3O4. NH4+-N was mainly oxidised to N2. This study provides a new harmless treatment technology for EMMR.

High concentrations of manganese (Mn2+) and ammonia nitrogen (NH4+-N) in electrolytic manganese residue leachate (EMRL) have seriously polluted the environment. In this study, electric field and phosphorus ore flotation tailings (POFTs) were used for Mn2+ and NH4+-N removal in EMRL firstly. The effects of the liquid acid ratios, reaction temperature, current density, initial pH and stable pH of the solution, characteristics of EMRL and POFTs, and removal mechanism of NH4+-N and Mn2+ were investigated. The results indicated that an electric field enhanced the leaching of POFTs and promoted the adsorption and precipitation of Mn2+ and NH4+-N. The concentrations of Mn2+, NH4+-N, PO43− and F− in EMRL were 0.12 mg/L, 9.2 mg/L, 0.09 mg/L, and 0.24 mg/L, respectively, which were within the permitted level for the integrated wastewater discharge standard (GB8978-1996) after adjusting the second stable pH to 10.0. Mn2+ was mostly remove in the form of Mn(OH)2, MnOOH, Mn5(OH)4(PO4)2 and MnO2. NH4+-N was mostly remove as NH4MgPO4·6H2O. The phosphate precipitation obtained could be used as market fertilizer. This study provided a new research idea for EMRL harmless disposal and POFTs resource utilization.

Ammonia and manganese were simultaneously removed from electrolytic metal manganese residue leachate using phosphate salt. The influence of different N:P ratios and pH were investigated. Phase transition and decomposing behavior of precipitates and the characterization of the precipitates pyrolysis were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, and scanning electron microscope. In the laboratory experiment, under the condition of 1:1.15 N:P ratio and 9.5 pH value, removal efficiencies of ammonia and manganese from the residue leachate were achieved 95.0% and 99.9%, respectively, and remaining concentration of orthophosphate was as low as 12 mg L−1. In the process, manganese was first removed as Mn3(PO4)2·7H2O, and then ammonia was removed as NH4MgPO4·6H2O. In addition, MgNaPO4, MgHPO4, Mg2P2O7, Na3PO4 and MnO2 were generated during precipitate pyrolysis process, and the ammonia removal efficiency decreased from 84.0% in the first cycle to 66.0% in the fifth, and manganese removal efficiency was approximately 99.0%. Economic evaluation shows that recycling the precipitates for three times could save 68.4% cost on average, compared to the use of pure chemicals.

In this study, P-LGMgO (low-grade MgO and NaH 2 PO 4 ·2H 2 O), P-CaO (CaO and NaH 2 PO 4 ·2H 2 O), and P-MgCa (low-grade MgO, CaO and NaH 2 PO 4 ·2H 2 O) were used for the solidification/stabilization (S/S) of electrolytic manganese residue (EMR). Relevant characteristics such as ammonia nitrogen and manganese stabilization behavior, unconfined compressive strength (UCS), probable S/S mechanisms, and EMR leaching test were investigated. The results demonstrate that using P-LGMgO had higher stabilization efficiency than P-CaO and P-MgCa for the S/S of EMR at the same stabilization agent dose. The stabilization efficiency of ammonia nitrogen and manganese in the EMR were 84.0% and 99.9%, respectively, and the UCS of EMR was 5.1 MPa using P-LGMgO process after curing for 28 days when the molar ratio of Mg:P was 5:1 and dose of stabilization agent was 12 wt%. In this process, ammonia nitrogen was stabilized by struvite (NH 4 MgPO 4 ·6H 2 O), and manganese by bermanite (Mn 3 (PO 4 ) 2 (OH) 2 ·4H 2 O) and pyrochroite (Mn(OH) 2 ). The leaching test results show that the values of all the measured metals on the 28th day were within the permitted level for the GB8978-1996 test suggested by China’s environmental protection law and the concentration of ammonia nitrogen can be reduced from 504.0 mg L −1 to 76.6 mg L −1 .

High-valent manganese was hard to be extracted from electrolytic manganese residues. To strengthen the extraction of Mn, electrochemical extraction method was investigated in this work. The mechanisms of the electrochemical extraction were examined along with the electrochemical performance of the reaction system via X-ray diffraction, scanning electron microscopy, X-ray Fluorescence, and BET. Results show that high-valent manganese can be reduced effectively under an electric field. The extraction efficiencyof manganese reached 96.2% under the optimum conditions of current density 25 mA/cm 2 , 9.2 wt% H 2 SO 4 , solid-to-liquid ratio of 1:5, room temperature, 1:1.0 M ratio of Mn to Fe 2 + and 60 min extraction. The extraction efficiency of manganese is 51.8% higher than that attained under the same conditions without an electric field and Fe 2 + . Meanwhile, the manganese content in residue decreased from 2.34% to 0.09%.

In this study, an improved process for leaching manganese from electrolytic manganese residue (EMR) by electro-reduction was developed. The mechanisms of the electro-reduction leaching were investigated through X-ray diffraction, scanning electron microscopy, X-ray fluorescence, and Brunauer Emmett Teller. The results show that the electric field could change the surface charge distribution of EMR particles, and the high-valent manganese can be reduced by electric field. The leaching efficient of manganese reached 84.1% under the optimal leaching condition: 9.2 wt% H2SO4, current density of 25 mA/cm2, solid-to-liquid ratio of 1:5, and leaching time for 1 h. It is 37.9% higher than that attained without an electric field. Meanwhile, the manganese content in EMR decreased from 2.57% to 0.48%.

Ammonia nitrogen- and manganese-contaminated water poses a considerable threat on the safety of water resources. In this work, pulse current (PC) electrolysis, a novel process, was developed to recover manganese and remove ammonia nitrogen from simulation wastewater simultaneously. Accordingly, the parameters of pulse electrolysis, and technological conditions, including temperature, initial pH, and concentration of addition NaCl, were investigated. The results showed that the concentration of manganese in simulation wastewater could be reduced from 160 mg L−1 to 0.2 mg L−1, meanwhile, ammonia nitrogen could be removed from 80 mg L−1 to 0.1 mg L−1 for 2.5 h PC electrolysis at 30 mA cm−2, 1000 Hz, and duty cycle 50% where settled with Ti/SnO2 IrO2 RuO2 electrodes, when the initial pH was 10.0 and NaCl addition was 0.008 mol L−1 at room temperature. Moreover, XRD and SEM analysis showed that manganese dioxide was deposited on the anode, and manganese in simulation wastewater was mainly recovered in the form of manganese dioxide.

In this work, nitrite was developed to simultaneously remove manganese and ammonia nitrogen from wastewater by the electrochemical method. The characteristics of electrolytic reaction were observed via cyclic voltammograms. Moreover, the mole ratio of nitrite and ammonia nitrogen, voltage, and initial pH value, which affected the removal efficiency of ammonia nitrogen and manganese, were investigated. The results showed that the concentration of ammonia nitrogen in wastewater could be reduced from 120.2 to 6.0 mg L−1, and manganese could be simultaneously removed from 302.4 to 1.5 mg L−1 at initial pH of 8.0, the mole ratios of nitrite and ammonia nitrogen of 1.5:1, and voltage of 20 V direct current electrolysis for 4.0 h. XRD analysis showed that manganese dioxide was deposited on the anode, and manganese was mainly removed in the form of manganese hydroxide precipitation in the cathode chamber.

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.

In this study, a new electrochemical method was used to simultaneously efficient removal of Mn2+ and NH4+-N in wastewater with Cu plate as cathode. The effects of various reaction parameters on the concentrations of Mn2+, NH4+-N and by-products (NO3−-N and NO2−-N, free chlorine and residual chlorine), as well as the removal mechanism were investigated. The results showed that the removal efficiencies of Mn2+ and NH4+-N were 99.1% and 92.9%, and the concentrations of NO3−-N, NO2−-N, free chlorine and residue chlorine were 0.73 mg/L, 0.15 mg/L, 0.13 mg/L and 0.63 mg/L reacting for 3 h at room temperature, respectively, when the current density was 10 mA/cm2, the mass ratio of ClO− and Cl− was 1:1, the initial pH was 9. The concentrations of Mn2+, NH4+-N and by-products in wastewater met the integrated wastewater discharge standard (GB8978-1996). In addition, spherical manganese oxide was deposited on the anode plate, and spherical manganese oxide collapsed over electrolysis time. Manganese was mainly removed in the form of MnO, Mn(OH)2 and MnO2. NH4+-N was mainly oxidized to N2. Economic evalution revealed that the treatment cost was 2.93 $/m3.

High concentrations of manganese (Mn2+) and ammonia nitrogen (NH4+-N) in electrolytic manganese residue (EMR) have seriously hindered the sustainable development of electrolytic manganese industry. In this study, an innovative basic burning raw material (BRM) was used to stabilize/solidify Mn2+ and NH4+-N in EMR. The characteristics of EMR and BRM, stabilize mechanism of NH4+-N and Mn2+, and leaching test were investigated. The concentrations of NH4+-N and Mn2+ were 12.8 mg/L and 0.1 mg/L, respectively, when the solid liquid ratio was 1.5:1, and the mass ratio of EMR and BRM was 100:10, at the temperature of 20 °C reacting for 12 h Mn2+ was mostly solidified as bustamite ((Mn,Ca)Si2O6), groutite (MnOOH) and ramsdellite (MnO2). NH4+-N was mostly recycled by (NH4)2SO4 and (NH4)3H(SO4)2. Leaching test results indicated that the concentrations of heavy metals were within the permitted level for the integrated wastewater discharge standard (GB8978-1996). Economic evaluation revealed that the cost of EMR treatment was $ 10.15/t by BRM. This study provided a new research idea for EMR harmless disposal.

Electrolytic manganese residue (EMR) contains a lot of manganese (Mn2+) and ammonia nitrogen (NH4+-N), which can cause environmental pollution. In this study, surfactant and anode iron plate were used to synergistically enhance NH4+-N and Mn2+ leaching from EMR. The Characteristics of EMR, Mn2+ and NH4+-N leaching mechanism, and the leaching test were systematically studied. The results showed that the leaching efficiencies of Mn2+ and NH4+-N were 89.4% and 65.9%, respectively, when the current density was 20 mA/cm2 and iron as the anode plate, the mass of H2SO4 was 13 wt%, solid-to-liquid ratio of 1:5 at 20 °C reacting for 120 min. In addition, when the surfactant concentration of tetradecyl trimethylammonium chloride (TTC) was 100 mg/L, the leaching efficiency of Mn2+ and NH4+-N in EMR respectively increased from 89.4% to 97.1% and from 65.9% to 98.4% by adding electric field. The leaching efficiencies of Mn2+ and NH4+-N were 28.5% and 93.7%, respectively, which was higher than that attained under the same condition without an electric field and TTC surfactant. Meanwhile, electric field changed the movement and charge distribution of charged particles on the surface of SiO2 and CaSO4·2H2O particles and released soluble compound salt containing Mn2+ and NH4+-N. TTC surfactant also improved the hydrophilic and hydrophobic properties of the EMR surface and promoted the wetting ability of the particles and the leaching of Mn2+ and NH4+-N. This study shows that TTC surfactant and anode iron plate can enhance NH4+-N and Mn2+leaching from EMR.

This study examined simultaneous stabilization and solidification (S/S) of Mn

Electrolytic manganese residue (EMR) is a solid waste generated in filters after sulfuric acid leaching of manganese carbonate ore, which contains manganese, ammonia nitrogen and heavy metals that cause damage to environment. In fact, leaching and recovery of manganese and ammonia nitrogen from EMR is the key to the harmless treatment and resource utilization of EMR. In this study, electric field was applied to leach manganese and ammonia nitrogen from EMR. In addition, carbonate precipitation and struvite precipitation methods were used to recover manganese and ammonia nitrogen from leaching solution. The results showed that the leaching efficiencies of manganese and ammonia nitrogen were 88.07% and 91.50%, respectively, when the current density was 35 mA/cm2, the mass of H2SO4 and H2O2 were 9.15 wt% and 3.33 wt%, solid-liquid ratio was 1:5 at temperature of 40 °C leached for 120 min. All heavy metals content in leached EMR except Ni and Cd were below national standard (GB 15618–2018) by electric field enhanced leaching. Meanwhile, manganese and ammonia nitrogen in leaching solution were fractional recovered by MnCO3 and struvite, and the recovery efficiency of manganese and ammonia nitrogen was 98.6% and 98.0%, respectively. This study provides a direction for the effective harmless treatment and resource utilization of EMR.

The objective of this work was the immobilization of soluble manganese (Mn) and ammonium nitrogen (NH4 +-N) leached from electrolytic manganese residue (EMR). Immobilization of Mn was investigated via carbonation using carbon dioxide (CO2) and alkaline additives. NH4 +-N immobilization was evaluated via struvite precipitation using magnesium and phosphate sources. Results indicated that the immobilization efficiency of Mn using CO2 and quicklime (CaO) was higher than using CO2 and sodium hydroxide (NaOH). This higher efficiency was likely due to the slower release of OH− during CaO hydrolysis. The immobilization efficiency of Mn was >99.99 % at the CaO:EMR mass ratio of 0.05:1 for 20-min reaction time. The struvite precipitation of NH4 +-N was conducted in the carbonated EMR slurry and the immobilization efficiency was 89 % using MgCl2 · 6H2O + Na3PO4 · 12H2O at the Mg:P:N molar ratio of 1.5:1.5:1 for 90-min reaction time. A leaching test showed that the concentrations of Mn and NH4 +-N in the filtrate of the treated EMR were 0.2 and 9 mg/L, respectively. The combined immobilization of Mn and NH4 +-N was an effective pretreatment method in the harmless treatment of the EMR.

Leaching tests of electrolytic manganese residue (EMR) indicated that high contents of soluble manganese and ammonia-nitrogen posed a high environmental risk. This work reports the results of simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese by air under calcium oxide assist. The ammonia-nitrogen stripping rate increased with the dosage of CaO, the air flow rate and the temperature of EMR slurry. Stripped ammonia-nitrogen was absorbed by a solution of sulfuric acid and formed soluble (NH4)2SO4 and (NH4)3H(SO4)3. The major parameters that effected soluble manganese precipitation were the dosage of added CaO and the slurry temperature. Considering these two aspects, the efficient operation conditions should be conducted with 8 wt.% added CaO, 60°C, 800 mL min(-1) air flow rate and 60-min reaction time. Under these conditions 99.99% of the soluble manganese was precipitated as Mn3O4, which was confirmed by XRD and SEM-EDS analyses. In addition, the stripping rate of ammonia-nitrogen was 99.73%. Leaching tests showed the leached toxic substances concentrations of the treated EMR met the integrated wastewater discharge standard of China (GB8978-1996).

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore, which mainly contains manganese and ammonia nitrogen and seriously damages the ecological environment. This work demonstrated the use of electrokinetic (EK) remediation to remove ammonia nitrogen and manganese from EMR. The transport behavior of manganese and ammonia nitrogen from EMR during electrokinetics, Mn fractionation before and after EK treatment, the relationship between Mn fractionation and transport behavior, as well as the effects of electrolyte and pretreatment solutions on removal efficiency and energy consumption were investigated. The results indicated that the use of H2SO4 and Na2SO4 as electrolytes and pretreatment of EMR with citric acid and KCl can reduce energy consumption, and the removal efficiencies of manganese and ammonia nitrogen were 27.5 and 94.1 %, respectively. In these systems, electromigration and electroosmosis were the main mechanisms of manganese and ammonia nitrogen transport. Moreover, ammonia nitrogen in EMR reached the regulated level, and the concentration of manganese in EMR could be reduced from 455 to 37 mg/L. In general, the electrokinetic remediation of EMR is a promising technology in the future.