Research on the optimal ratio of improved electrolytic manganese residue substrate about Pennisetum sinese Roxb growth effects.

Electrolytic manganese slag (EMR) is a solid waste generated in the manganese hydrometallurgy process. It not only takes up significant land space but also contains Mn2+, which can lead to environmental contamination. There is a need for research on the treatment and utilization of EMR. Improved EMR substrate for Pennisetum sinese Roxb growth was determined in pot planting experiments. The study tested the effects of leaching solution, microorganisms, leaf cell structures, and growth data. Results indicated a substrate of 45% EMR, 40% phosphogypsum, 5% Hericium erinaceus fungi residue, 5% quicklime, and 5% dolomite sand significantly increased the available phosphorus content (135.54 ± 2.88 µg·g-1) by 17.95 times, compared to pure soil, and enhanced the relative abundance of dominant bacteria. After 240 days, the plant height (147.00 ± 0.52 cm), number of tillers (6), and aerial dry weight (144.00 ± 15.99g) of Pennisetum sinese Roxb increased by 5.81%, 200%, and 32.58%, respectively. Analyses of leaves and leaching solution revealed that the highest leaf Mn content (46.84 ± 2.91 µg·g-1) being 3.38 times higher than in pure soil, and the leaching solution Mn content (0.66 ± 0.13 µg·g-1) was lowest. Our study suggested P. sinese Roxb grown in an improved EMR substrate could be a feasible option for solidification treatment and resource utilization of EMR.

The waste solid resource utilization was achieved.The growth and ecological restoration value of Pennisetum sinese Roxb in an improved EMR substrate was found.An optimal ratio of improved EMR substrate was proposed.

Synergistic solidification and mechanism research of electrolytic manganese residue and coal fly ash based on C-A-S-H gel material.

Electrolytic manganese residue (EMR) is known for high concentrations of Mn2+, NH4+, and heavy metals. Failure to undergo benign treatment and landfill disposal would undeniably lead to negative impacts on the quality of the surrounding ecological environment. This study sought to mitigate the latent environmental risks associated with EMR using a cooperative solidification/stabilization (S/S) method involving coal fly ash (CFA). Leveraging leaching toxicity tests, the leaching behavior of pollutants in electrolytic manganese residue-based geopolymer materials (EMRGM) was determined. At the same time, mechanistic insights into S/S processes were explored utilizing characterization techniques such as XRF, XRD, FT-IR, SEM-EDS, and XPS. Those results confirmed significant reductions in the leaching toxicities of Mn2+ and NH4+ to 4.64 µg/L and 0.99 mg/L, respectively, with all other heavy metal ions falling within the permissible limits set by relevant standards. Further analysis shows that most of NH4+ volatilizes into the air as NH3, and a small part is fixed in the EMRGM in the form of struvite; in addition to being oxidized to MnOOH and MnO2, Mn2+ will also be adsorbed and wrapped by silicon-aluminum gel together with other heavy metal elements in the form of ions or precipitation. This research undeniably provides a solid theoretical foundation for the benign treatment and resourceful utilization of EMR and CFA, two prominent industrial solid wastes.

A novel slag composite for the adsorption of heavy metals: Preparation, characterization and mechanisms.

The utilization of solid waste for resource recovery and production of value-added products is the theme of green chemistry. Currently, how to using solid wastes to prepare environmentally-functional materials with high performance and strength is one of the hot topics. In this research, electrolytic manganese residue (EMR) was thermally activated with calcite to prepare a silicon-based functionalized adsorbent (C-EMR) for the removal of cadmium (Cd2+, 467.14 mg/g) and lead (Pb2+, 972 mg/g). The thermodynamic results indicated that the removal process of Cd2+ and Pb2+ by C-EMR were endothermic and spontaneous. HNO3 can effectively strip the two adsorbed metals from C-EMR with the stripping efficiency of nearly 80% for Cd2+ and 99.92% for Pb2+, indicating that adsorption and ion exchange may be the main reason for the removal of the metals on C-EMR. Besides, surface precipitation was also responsible for removing some Pb2+ from the aquatic environment according to the X-ray photoelectron spectrometry (XPS) analysis. Results indicate that -SiO3- has stronger affinity with Pb2+ and Cd2+ than other groups ((-MnO2), -OH) by theoretical calculation (VASP, GGA-PBE). This study shows that this novel adsorbent (C-EMR) can be adopted as an environmentally-friendly, inexpensive and efficient adsorbent for removal of Cd2+ and Pb2+ from aquatic solution. This technique not only provides potential adsorbent for the elimination of heavy metals but also proposes an alternative route for the treatment and utilization of waste solid.

Comprehensive effects of grain-size modification of electrolytic manganese residue on deep dehydration performance and microstructure of sludge.

As the by-product accompanied by sewage treatment, sludge has complex composition and high moisture content, therefore, its reutilization and disposal are still a challenge. In this paper, five kinds of quartz sand conditioners with different particle sizes (denoted as QS1, QS2, QS3, QS4 and QS5, respectively) were used to explore the effect of particle size distribution of conditioners on sludge dewatering performance. The moisture content, capillary suction time (CST), time to filter (TTF), specific resistance of filtration (SRF), particle size distribution curve, pore distribution law, scanning electron microscopy, isothermal adsorption-desorption curve and extracellular polymeric substances distribution were employed to characterize the modified sludge and explore the improvement mechanism. The results show that the particle size distribution of the conditioner significantly affects the efficiency of sludge dewatering. The wt% of sludge regulated with QS1 (QS1-S) could be reduced to 52%, and its CST value, TTF value and SRF value is 57.93 s, 278 s and 1.84 × 108 s2 g-1, respectively. The conjecture about the effect of difference of particle size distribution on sludge dewatering performance was verified with the original Electrolytic Manganese Residue (EMR) and the grain-size modified Electrolytic Manganese Residue (EMR6). Compared with those of the EMR-conditioned sludge, the CST, TTF and SRF of EMR6-conditioned sludge was decreased by 8.7%, 22.3% and 11.2%, respectively. According to analysis of surface microstructure, the surface of the sludge cake modified with QS1 is rough and sparse with rich pore structure. Compared with those of the undisturbed sludge (A0), the pore volume and specific surface area of the sludge modified with QS1 was increased by 61.65% and 38.62%, respectively. After grain-size modification, the dehydration effect of EMR6 (D10 4.25 µm, D50 19.65 µm, D90 73.26 µm) was significantly enhanced, and the D10, D50 and D90 value was close to that of QS1. It can be concluded that the particle size of QS1 (D10 3.27 µm, D50 15.66 µm, and D90 62.23 µm) can improve the dewatering performance of sludge by shearing the sludge particles to change the original sludge particle size distribution and improving the blockage of sludge dewatering channels.

Highly efficient persulfate catalyst prepared from modified electrolytic manganese residues coupled with biochar for the roxarsone removal.

The contamination of organoarsenic is becoming increasingly prominent while SR-AOPs were confirmed to be valid for their remediation. This study has found that the novel metal/carbon catalyst (Fe/C-Mn) prepared by solid waste with hierarchical pores could simultaneously degrade roxarsone (ROX) and remove As(V). A total of 95.6% of ROX (20 mg/L) could be removed at the concentration of 1.0 g/L of catalyst and 0.4 g/L of oxidant in the Fe/C-Mn/PMS system within 90 min. The scavenging experiment and electrochemical test revealed that both single-electron and two-electron pathways contributed to the ROX decomposition. Spectroscopic analysis suggested the ROX has been successfully mineralized while As(V) was fixed with the surface Fe and Mn. Density functional theory (DFT) calculation and chromatographic analysis indicated that the As7, N8, O9 and O10 sites of ROX molecule were vulnerable to being attacked by nucleophilic, electrophilic and radical, resulting in the formation of several intermediates such as phenolic compounds. Additionally, the low metal leaching concentration during recycling and high anti-interference ability in various water matrices manifested the practicability of Fe/C-Mn/PMS system.

Release characteristics of heavy metals from electrolytic manganese residue under varying environmental factors.

High levels of manganese (Mn) and other heavy metals from electrolytic manganese residue (EMR) stockpiled would be released into the environment under natural conditions. A batch-leaching test was carried out to investigate the release characteristics of heavy metals from EMR with different storage times under simulated environmental conditions such as acid rain with different pH (3.0, 4.5, 5.6, and 7.0) at contact times of 1, 2, 4, 6, and 12 h; liquid to solid ratio (L/S) (5:1, 10:1, 20:1, and 30:1); and temperature (15, 25, 35, and 45 °C). The results showed that low pH (3.0 and 4.5) and high temperature (35 and 45 °C) could significantly promote heavy metal leaching from EMRs and increasing the L/S ratio above 20:1 mL/g significantly decreased heavy metal leachate concentrations due to dilution effect. Cr, Mn, and Pb concentrations in leachate increased almost continuously throughout the leaching process, while Zn decreased slightly at the 12th hour. Meanwhile, heavy metal concentrations in EMR1 (fresh EMR) were higher than in EMR2 (out stockpiled for more than 3 months). The concentrations of Mn, Pb, and Zn in leachates from EMRs at pH 3.0 and 4.5 leaching far exceeded the allowable maximum discharge concentrations for pollutants of the integrated wastewater discharge standard in China (GB8978-1996) by 57.5-59.0, 1.3-4.3, and 1.1-1.8 and 53.5-56.0, 3.04-7.25, and 1.0-1.91 times, respectively. Additionally, the Mn concentrations from both EMR leachates at pH 7.0 were above the national safe emission threshold. The morphological structure of EMRs changed after leaching, and XRD analysis showed the disappearance of MnO2, SiO2, FeS2, and CaSO4. The XPS revealed that Cr, Mn, Pb, and Zn existed as Cr3+, MnO, PbSO4, and ZnSiO3, respectively, after leaching. The study concluded that Mn, Pb, and Zn from EMRS leached by acid rain might pose a high potential environmental risk. Therefore, developing appropriate disposal techniques for EMR is necessary to prevent heavy metal pollution.

Screening of silicon-activating bacteria and the activation mechanism of silicon in electrolytic manganese residue.

Electrolytic manganese residue (EMR) is a kind of solid waste with a high silicon content. Most of the silicon in EMR, however, exist in the state of SiO2, which cannot be directly absorbed by plants. Currently, it is very challenge to recover the silicon from EMR. In this study, a preliminary screening of strains with silicon-activating ability was conducted, and four strains were screened out and isolated from the soil around the tailings pond of EMR. Then, single factor experiments were conducted to obtain the optimal growth conditions of the four strains, and the results indicated that the Ochrobactrum sp. T-07 had the best silicon-activating ability from EMR after nitrosoguanidine mutagenesis (Ochrobactrum sp. T-07-B). The available silicon (in terms of SiO2) in the leaching solution was up to 123.88 mg L-1, which was significantly higher than that produced by Bacillus circulans and Paenibacillus mucilaginosus, the two commercial available pure culture strains. Results of direct/indirect contact experiments between Ochrobactrum sp. T-07-B and EMR revealed that bioleaching was promoted under the synergistic effect of bacteria growth on the surface of and metabolism within EMR. The newly isolated strains with silicon-activating effect are different from the existing-known silicate bacteria and may be used for more efficient silicon activation in silicate minerals.

A novel method for the stabilization of soluble contaminants in electrolytic manganese residue: Using low-cost phosphogypsum leachate and magnesia/calcium oxide.

Electrolytic manganese residue (EMR) contains a large amount of NH4+-N and Mn2+ and can negatively impact the environment. A stabilization treatment of soluble contaminants in the EMR is necessary for its reuse and safe stacking. This study presents experimental results for the stabilization of NH4+-N and Mn2+ in the EMR using phosphogypsum leachate as a low-cost phosphate source and MgO/CaO (PLMC) process. The results demonstrated that the stabilization efficiency of NH4+-N and Mn2+ was 93.65% and 99.99%, respectively, under the following conditions: a phosphogypsum leachate dose of 1.5 mL g-1, an added MgO dose of 0.036 g g-1, an added CaO dose of 0.1 g g-1 and a reaction time of 2 h. The stabilization effect of the PLMC process was higher and more cost effective than that of using Na3PO4·12H2O and MgO/CaO. The concentration of NH4+-N and Mn2+ in the leaching liquor decreased to 80 mg L-1 and 0.5 mg L-1, respectively, after the stabilization under the optimum conditions. The stabilization characteristics indicated that NH4+-N was stabilized to form NH4MgPO4·6H2O (struvite) and that Mn2+ was stabilized to form Mn5(PO4)2(OH)4, Mn3(PO4)2·3H2O and Mn(OH)2. PO43--P, F-, and heavy metal ions of the phosphogypsum leachate were removed from the leaching liquor and stabilized in the treated EMR.

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.

Enhanced electrokinetic remediation of manganese and ammonia nitrogen from electrolytic manganese residue using pulsed electric field in different enhancement agents.

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.

Bioleaching of silicon in electrolytic manganese residue using single and mixed silicate bacteria.

Electrolytic manganese residue (EMR) is a type of industrial solid waste with a high silicon content. The silicon in EMR can be used as an essential nutrient for plant growth, but most of the silicon is found in silicate minerals with very low water solubility, that is, it is inactive silicon and cannot be absorbed and used by plants directly. Thus, developing a highly effective and environmentally friendly process for the activation of silicon in EMR is important both for reusing solid waste and environmental sustainability. The aim of this study was to investigate the desilication of EMR using cultures of Paenibacillus mucilaginosus (PM) and Bacillus circulans (BC). The results showed that the two types of silicate bacteria and a mixed strain of them were all able to extract silicon from EMR with a high efficiency, but the desilication performance of the mixed PM and BC was the best. Fourier transform infrared spectroscopy indicated that silicate bacteria can induce a suitable micro-environment near the EMR particles and release Si into the solution through their metabolism. X-ray diffraction analysis confirmed that layered crystal minerals, such as muscovite and diopside, were more likely to be destroyed by the bacterial action than quartz, which has a frame structure. Scanning electron microscopy-energy dispersive spectrometry proved that the silicate structures were destroyed and that Si in the residue was decreased, indicating the dissolution of silicon under the action of these microorganisms. This study suggests that bioleaching may be a promising method for the activation of silicon in EMR.

Simultaneous stabilization/solidification of Mn2+ and NH4+-N from electrolytic manganese residue using MgO and different phosphate resource.

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%.

Simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese from electrolytic manganese residue by air under calcium oxide assist.

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).

Investigating the Dewatering Efficiency of Sewage Sludge with Optimized Ratios of Electrolytic Manganese Residue Components.

As an industrial waste residue, Electrolytic Manganese Residue (EMR) can greatly promote sludge dewatering and further particle-size optimization can significantly strengthen sludge dewaterability. In this study, the effects of ammonium sulfate, calcium sulphate dihydrate, and manganese carbonate in EMR on sludge dewatering performance were investigated using the response surface optimization method. It was found that the optimized ratio of three components in EMR was 1.0:1.6:2.2 based on capillary suction time (CST), specific resistance of filtration (SRF), and zeta potential of dewatered sludge. The composition ratio of particle-size optimized EMR was modified based on the above optimization, resulting in a significant increase in sludge dewatering performance (CST and SRF reduced by 8.7% and 11.2%, respectively). Compared with those in original sludge, the content of bound extracellular polymeric substances in the conditioned sludge with optimized ratio was drastically reduced while that of soluble extracellular polymeric substances was slightly increased, which was in accordance with the decline of fluorescence intensity. These findings indicated the disintegration of extracellular polymeric substances, the enhancement of hydrophobicity, and dewatering properties of the sludge. In summary, optimized EMR can effectively intensify the dewaterability of sludge, providing a competitive solution for dewatering and further disposal of sludge.

Synthesis of Electrolytic Manganese Slag-Solid Waste-Based Geopolymers: Compressive Strength and Mn Immobilization.

The massive stockpiling of electrolytic manganese residue (EMR) has caused serious environmental pollution. In this study, EMR, coal gangue (CG), and fly ash (FA) were used as raw materials to obtain the optimal mix ratio based on Design-Expert mixture design. The effects of activator modulus, liquid-solid (L/S) ratio, and curing temperature on the mechanical properties of geopolymers were investigated. The results showed that the compressive strength of the prepared geopolymer was 12.0 MPa, and the 28d leaching of Mn was 0.123 mg/L under the conditions of EMR:CG:FA = 0.43:0.34:0.23, L/S = 0.9, a curing temperature of 60 °C, and a curing time of 24 h. This indicates that the geopolymer is an environmentally friendly material with high compressive strength. The mineral composition of the geopolymer is mainly hydrated calcium silicate and geopolymer gel. In addition, a more stable new mineral phase, MnSiO3, was generated. The Fourier transform infrared (FTIR) spectrogram showed that the peak at 1100 m-1 was shifted to 1112 cm-1, which indicated that a geopolymerization reaction had occurred. Through scanning electron microscopy (SEM) and energy dispersive spectrum (EDS) analysis, it was identified that the geopolymerization produced a large amount of amorphous gelatinous substances with a relatively dense structure, the major elements being oxygen, silicon, aluminum, calcium, and sodium.

Synergistic preparation and application in PCU of α-calcium sulfate hemihydrate whiskers from phosphogypsum and electrolytic manganese residue.

The α-calcium sulfate hemihydrate whiskers (α-CSHWs) were first prepared using phosphogypsum (PG) and electrolytic manganese residue (EMR) as raw materials for coating urea, demonstrating excellent controlled-release properties. The effects of different reaction conditions on α-CSHWs, achieved by optimizing the reaction time, the concentrations of NH4+, Mn2+, and other factors, were discussed. Results showed that when the EMR content was 25 wt%, the reaction temperature was 100 °C, and the reaction time was 3 h, α-CSHWs with a length-to-diameter ratio of 39 were obtained. Through experiments and density functional theory (DFT), the mechanism of α-CSHWs preparation was elucidated. The results show that the addition of EMR reduces the content of impurity ions PO43- and F- in PG while introducing NH4+ and Mn2+. Interestingly, both NH4+ and Mn2+ can reduce the nucleation time of α-CSHWs, while PO43-, Mn2+, and F- are more likely to adsorb on the (0 0 6) crystal plane of α-CSHWs, NH4+ readily adsorbs on the (4 0 0) crystal plane. The controlled-release performance of modified α-CSHWs incorporated into polyurethane-coated urea (PCU) was investigated, and it was found that the addition of Mα significantly prolonged the nutrient release period, with the period extending up to 116 days for coatings of 5wt% and above. This work not only enhances the efficiency of PG and EMR utilization but also serves as a reference for the straightforward synthesis and application of α-CSHWs.

Highly efficient Mn2+, Mg2+, and NH4+ recovery from electrolytic manganese residue via leaching, solvent extraction, coprecipitation, and atmospheric oxidation.

Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, exhibits substantial leaching toxicity owing to its elevated levels of soluble Mn2+ and NH4+. The leaching and recovery of valuable metal ions and NH4+ from EMR are key to the hazard-free treatment and resource utilization of EMR. In this study, two-stage countercurrent leaching with water was used to leach Mn2+, Mg2+, and NH4+ from EMR. Subsequently, two-stage countercurrent extraction was conducted using α-hydroxy-2-ethylhexyl phosphinic acid (α-H-2-EHA) as an extractant to enrich Mn2+, and Mg2+, and NH4+ were recovered via coprecipitation. Based on the calculations for a single leaching-extraction process, the recoveries of Mn2+, Mg2+, and NH4+ ions exceeded 80%, 99%, and 90%, respectively. In addition, high-purity Mn3O4 with an Mn content of 71.61% and struvite were produced. This process represents a win-win strategy that facilitates the hazard-free treatment of EMR while simultaneously recovering valuable Mn2+, Mg2+, and NH4+ resources from waste. Thus, this study provides a novel approach to the hazard-free and resourceful management of solid waste. ENVIRONMENTAL IMPLICATION: Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, poses significant environmental risks due to its soluble heavy metals and ammonia nitrogen content. Efforts have been made to address this issue, but there has been no mature industrial application due to cost or processing capacity constraints. In this work, solvent extraction was first used to enrich Mn2+ from EMR leachate, and a novel α­hydroxy­2­ethylhexyl phosphinic acid was used as extractant. High purity Mn3O4 and struvite was synthesized through this process. The win­win strategy offers a novel approach for the hazard­free and resourceful utilization of solid waste.

Adsorption of Phosphate by Two-Step Synthesis of Ceramsite from Electrolytic Manganese Residue/Dredged Sludge.

Carrying out research on the management of electrolytic manganese residue (EMR) is necessary to maintain the environment and human health. The dredged sludge (DS) and water hyacinth (WH) generated from dredging projects are potential environmental threats, and therefore suitable methods need to be found for their treatment. In this study, ceramsite was prepared by a two-step low-temperature firing method using DS and EMR as raw materials, WH as a pore-forming additive, and aluminate cement as a binder for the adsorption of phosphorus from wastewater. The optimal ratio and process parameters of the ceramsite were determined by mechanical and adsorption properties. The static adsorption experiments were conducted to study the effect of ceramsite dosage and solution pH on the removal of phosphorus. At the same time, dynamic adsorption experiments were designed to consider the influence of flow rate on its actual absorption effect, to explore the actual effect of ceramsite in wastewater treatment, and to derive a dynamic adsorption model that can provide technical support and theoretical guidance for environmental management.

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.