Manganese Residue Research Articles

Effect of Phanerochaete chrysosporium inoculation on manganese passivation and microbial community succession during electrical manganese residue composting

Electrolytic manganese residue poses potentially threats to the environment and therefore needs eco-friendly treatment. Composting has been reported to effectively passivate heavy metals and alleviate their ecotoxicity. Observation of the Mn concentration during composting indicated that the mobility of Mn was significantly reduced, with the easily extraction fraction (acid extractable and easily reduction fraction) of Mn in the control pile (pile 1 without Phanerochaete chrysosporium inoculation) and treat pile (pile 2 with Phanerochaete chrysosporium inoculation) decreasing by 17% and 29%, respectively. The inoculation of Phanerochaete chrysosporium prompted the passivation of manganese, prolonged the thermophilic period, and enriched the microbial community structure, which was attributed to the rapid growth and reproduction of thermophilic bacteria. Moreover, Phanerochaete chrysosporium inoculation promoted the effect of pH on the stabilization of Mn, but the opposite contribution of organic matter. This study would provide a new perspective for remediating EMR contaminated soil via composting.

Utilization of electrolytic manganese residue to synthesize zeolite A and zeolite X for Mn ions adsorption

Extensive research is being carried out to efficiently utilize electrolytic manganese residue (EMR) and convert it into useful materials. In this paper, phase pure zeolite A (ZA) and zeolite X (ZX) were synthesized by EMR for the first time. The EMR-based zeolites were characterized by XRD, TG, SEM and BET, and their zero point charges were tested. Then, the adsorption capacities of ZA and ZX on Mn ions were studied. On the adsorbent concentration = 3.0 g/L and C0 = 439 mg/L, the adsorption capacities of ZA and ZX on Mn ion were 119.5 and 96.7 mg/g, respectively. In addition, the adsorption kinetics and isotherms of the adsorption process were discussed, and the adsorption mechanism was clarified by means of XRD, FTIR, SEM, and XPS. The appearance of Mn-O functional groups indicated that Mn ions did enter the binding sites of zeolites. Moreover, ZA and ZX were successfully regenerated in this work. Furthermore, the influence of coexisting cations was explored, and the maximum adsorption capacities of ZA and ZX were compared with other adsorbents, which proved the excellent adsorption of Mn ions by ZA and ZX. In conclusion, the synthesized ZA and ZX were low-cost adsorption materials with high adsorption capacity.

Mn release behaviors from electrolytic manganese residue-based slow-release fertilizer using acid/alkali-activated geopolymers as binders: A comparative study

In this study, acid/alkali-activated geopolymers and electrolytic manganese residue (EMR) were used as a binder and Mn source, respectively, to prepare EMR-based slow-release fertilizers (SRFs) and Mn release behaviors from SRFs were comparatively investigated. Mn release from SRFs prepared by acid/alkali-based geopolymers follows first-order kinetics and the Ritger-Peppas model. For alkali activator attack, the easily leachable manganese salt (MnSO4·H2O) in EMR is converted to stable fractions (such as MnO2, Mn4Si8O20, and Ca4Mn4Si8O24) in the SRFs. The K-(A)-S-H gel in SRFs prepared using alkali-based geopolymers (SRFs-alGo) restricts rapid Mn release through physical encapsulation and ion exchange. In contrast, SRFs prepared using acid-based geopolymers (SRFs-acGo) mainly limit Mn release through pediocratic NH4MnPO4·H2O formation and physical adsorption/encapsulation of phosphoric acid-activated geopolymer gel (Si–O–Si–O–P–O). Phosphoric acid attack did not significantly changed the proportion of the exchangeable fraction of Mn in SRFs, which was maintained at approximately 40%. Moreover, Mn in SRFs-alGo was uniformly distributed on the surface and bulk phases (SEM-EDS and XPS co-analysis), while most of the Mn in SRFs-acGo was distributed on the surface of particles, leading to readily released Mn and even higher Mn release concentrations of SRFs-acGo. This study provides a theoretical basis for strategically applying EMR-based SRFs to plants with different Mn requirements and guides subsequent field experiments.

Harmless treatment of electrolytic manganese residue: Ammonia nitrogen recovery, preparation of struvite and nonsintered bricks

The ammonia nitrogen in electrolytic manganese residue (EMR) is easily transferred to water source, polluting the environment and endangering biological health. In this study, the ammonia nitrogen in EMR is removed by slaked lime, carbide slag (CS) and red mud (RM). The removal of ammonia nitrogen is influenced by the liquid–solid ratio, stirring time, and additives dosage. The removal efficiency of ammonia nitrogen of EMR pretreated with 7.4 % fresh CS for 15 min can reach 98.5 % when the liquid–solid ratio is 1.50. Under the synergistic effect of CS and RM, the ammonia nitrogen in EMR is quickly removed within 15 min, and the removal efficiency of ammonia nitrogen reaches 98.2 %. It is feasible to replace slaked lime with CS and RM to achieve the removal of ammonia nitrogen in EMR. Struvite has high quantity and good purity when the molar ratio of N, P and Mg is 1:1.6:1.6 and pH = 8.0. The remaining EMR after removal of ammonia nitrogen, blast furnace slag, Portland cement and aggregates was used as raw materials to prepare nonsintered bricks (NSB). The NSB according to the optimal formula after curing for 7 days had no free ammonia nitrogen detected. This study provided a new way to remove ammonium nitrogen in EMR by CS and RM, and demonstrated a solution to prepare struvite and nonsintered bricks.

In-situ growth of amorphous MnO2 on C-decorated Fe-based geopolymer sphere with rich structure defects for efficient solar light-induced photo-thermal-Fenton reaction

• A-MnO 2 /C-FeGS with rich structure defects was constructed as a photo-Fenton catalyst. • Highly stable and reactive A-MnO 2 was fabricated via ion exchange anchoring strategy. • Manganese residue was used as the source of Fe and Si for environmental remediation. • A-MnO 2 and C triggered photo-thermal conversion and lattice oxygen activation. • Photo-thermal synergy promoted photo-Fenton activity for tetracycline degradation. Crystalline MnO 2 exhibits excellent photo-thermal conversion and adjustability of valence states properties, but the weak near-infrared light absorption, poor charge transportation and utilization limit its environmental applications. Herein, a novel Na-doped amorphous MnO 2 /C-decorated Fe-based geopolymer sphere (A-MnO 2 /C-FeGS) with rich structure vacancies was constructed by ion exchange anchoring strategy and used to degrade tetracycline hydrochloride (TC) in solar light-induced photo-thermal-Fenton process. Manganese residue (MR), an industrial solid waste, was used as the source of Fe and Si. A-MnO 2 /C-FeGS exhibited excellent catalytic performance with TC removal of 98.2% within 30 min, being about 4.5 and 3.3 times faster than crystalline MnO 2 and C-FeGS, respectively. The improved photocatalytic activity was attributed to that rich oxygen vacancies could provide more catalytic active sites and accelerate Fe 3+ /Fe 2+ and Mn 4+ /(Mn 2+ +Mn 3+ ) conversion for more ·OH generation. Moreover, Na-doped amorphous MnO 2 and C decoration synergistically contributed to high photo-thermal conversion rate, which could in-situ heat the catalyst and induce the activation of H 2 O 2 . This promoted the activation of the surface lattice oxygen and accelerated the secondary transition and utilization of the thermal electrons captured by the defect sites. This work provides a novel strategy for the development of highly reactive catalysts and valorization of MR in the field of environmental remediation.

Manganese residue modified steel slag to improve low-temperature SCR of NOx

In this study, the denitrification performance of steel slag modified by manganese slag was studied. Different proportions of steel slag and electrolytic manganese anode mud mixtures were configured. The different proportions of the mixture would have varied physical and chemical properties. SS1+EMAM2 catalyst showed the nearly 100% NOx removal efficiency at 175°C. The specific surface area of steel slag is enhanced dramatically after modification by EMAM. Adding EMAM enhanced the weak acid sites and Brønsted-acid sites on the catalyst surface, resulting in a higher low-temperature SCR activity.

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.

A new perspective on Belite-ye'elimite-ferrite cement manufactured from electrolytic manganese residue: Production, properties, and environmental analysis

In this research, the electrolytic manganese residue (EMR) based belite-ye'elimite-ferrite (E-BYF) clinker composed of 51.6 % belite, 25.6 % iron phase, 15.8 % ye'elimite and 6.5 % over-burned anhydrite phase was manufactured successfully at 1200 °C _ 30 min by utilizing EMR (45.5 %) and additional CaO and Al2O3. The existence of iron-rich and heavy metal phases was a potential driving force for achieving near complete calcination at 1200 °C _30 min. The iron ions (8.4 %) and the over-burned anhydrite phase partially replaced the Al3+ ions by entering the ye'elimite lattice and provided enough SO3 (5.9 %) to help stabilize ye'elimite and β-C2S formation, respectively. Layered double hydroxides such as AFm phase and strätlingite formed dense microstructure and improved pastes strength as a new rigid skeleton. The formation of rigid solid skeleton-flexible gel embedded co-support system provided a reliable solution for eliminating inherent strength plateau (3-day of 45.9 MPa and 60-day of 107.0 MPa). In this system, the solid-phase hydrates as the main skeleton offered sufficient rigid-supporting, while the gels hydrates as the auxiliary fluid that filled into the pores of the formed skeleton gave the adequately flexible-supporting. In addition, thepastes showed an excellent stabilization ability of heavy metals. The E-BYF system has great potential in reducing CO2 emissions (0.58 kg/kg and 1.36 kg·/MPa·m3) and cost. This work provides a new perspective for a high-quality solution to the strength plateau while achieving a high value-added utilization of EMR.

Characteristic pollutants risk assessment of modified manganese residue utilization in sintered product.

The resource disposal of electrolytic manganese residue can effectively solve the problem of environmental pollution caused by it, among which the problem of heavy metal pollution is the most prominent. In this study, a new type of eco-friendly brick mixed with electrolytic manganese residue was designed. The influence of the content of electrolytic manganese residue on its macroscopic properties, microscopic properties, and leaching characteristics was analyzed by test methods such as compressive strength test, radioactivity test, XRF, XRD, FTIR, and ICP test of bricks. The results showed that the manganese content in the EMR leachate was 8120mg/L, which exceeded the Chinese standard. The leaching experiment of ordinary aqueous solution of sintered bricks mixed with 20% EMR showed that the content of heavy metals was far lower than the Chinese national standard. There was no non-carcinogenic risk of heavy metals in the strong acid leaching solution of sintered bricks mixed with 20% EMR. Only the carcinogenic risk values of Cr for adults and children were 4.21 × 10-4 and 9.82 × 10-4 respectively, both exceeding the USEPA limit, but the application scene of sintered bricks was difficult to achieve strong acidity, so it was judged that it had no carcinogenic risk to the human body. Characteristic heavy metals such as Mn, Cr, and As existed stably in sintered bricks through substitution and encapsulation. In addition, the compressive strength and radioactivity of EMR sintered bricks met the requirements of the Chinese national standard "Fired Ordinary Bricks." This product can be used as national standard MU20 grade brick. This study provided an efficient method for the safe and environmentally friendly disposal of EMR in a sustainable control system.

Cooperative removal of Mn2+, NH4+−N, PO43−−P and F− from electrolytic manganese residue leachate and phosphogypsum leachate

Cooperative removal of Mn2+, NH4+−N, PO43−−P and F− from electrolytic manganese residue leachate and phosphogypsum leachate

A novel multi-components hierarchical porous composite prepared from solid wastes for benzohydroxamic acid degradation

In this study, a novel carbon-wrapped-iron hierarchical porous catalyst (Fe/C-Mn800) was prepared from electrolytic manganese residue (EMR) and sewage sludge (SS), which showed outstanding degradation ability toward benzohydroxamic acid (BHA, nearly 90 % was removed within 60 min) with low metal leaching rate. Mechanism exploration found transition metal ions (Fe and Mn) can serve as electron acceptors and facilitate the generation of persistent free radicals (PFRs). These transition metal ions and PFRs mainly participated in the single-electron pathway via activating PMS to generate a large amount of reactive oxygen species (ROS). While the electron negative graphitic N and CO groups not only improve the electronegatively of catalyst, but also acted as the electron sacrificers to favor the electron transfer and directly oxidized the absorbed BHA through the ternary activated outer-sphere complexes. Eley–Rideal (E-R) and Langmuir–Hinshelwood (L-H) analysis further demonstrated the crucial role of pre-adsorption during the degradation process. This work provided a deep insight into the degradation mechanism of metal/carbon composite and promising opportunity widened the horizon of the high-value utilization of EMR and SS.

Enhanced manganese leaching from electrolytic manganese residue by electrochemical process and Na2SO3

Electrolytic manganese residue (EMR) is a general industrial solid waste containing manganese (Mn) and heavy metals that is produced in the process of electrolytic metal manganese. In this study, the leaching efficiency of Mn from EMR was improved by using Na2SO3 and electric field. The results showed that Mn leaching efficiency reached 96.63 % (333 K, 8 wt% H2SO4, 60 mA/cm2 current density and 0.16 mol/L Na2SO3), which was 30.56 % higher than leaching with H2SO4 and 12.76 % higher than leaching by using electric field. The kinetic results based on the unreacted contraction nucleus model showed that the process is controlled by a mixture of external diffusion interfaces and chemical reactions, with a calculated activation energy of 19.68 kJ/mol. Na2SO3 and electric field enhanced the leaching of Mn by removing the compound salts layer wrapped around the outside of Mn and reducing the release of high-valent Mn to divalent Mn. This study provide a novel approach for the utilisation of EMR.

Geopolymer synthesized from electrolytic manganese residue and lead-zinc smelting slag: Compressive strength and heavy metal immobilization

In order to follow the growing trend towards waste re-utilization and clean production, geopolymers were synthesized to immobilize Pb2+ and Zn2+ by simultaneously using electrolytic manganese residue (EMR) and lead-zinc smelting slag (LZSS) as raw aluminosilicate materials. Different contents of supplementary cementitious materials (i.e., blast furnace slag, sodium aluminate and silica-gel powder) were respectively employed to study the influences of Ca, Al and Si on compressive strengths of geopolymers. Moreover, the geopolymers can be used to immobilize heavy metals including Pb and Zn. The effects of heavy metals on compressive strength and leaching concentration were explored. Results showed that, geopolymers with 1% Pb(NO3)2 loading had a highest 7-day compressive strength of 28.5 MPa and a low heavy metal leaching concentration below the limit (total Pb < 5 mg/L, total Zn < 100 mg/L). Proved by XRD, FTIR, SEM-EDS, XPS analyses and theoretical calculation, the immobilization of Pb/Zn in EMR/LZSS based geopolymers was realized by physical encapsulation and chemical bonding. The proposed technology can be potentially used to convert Pb/Zn-containing solid wastes into less hazardous or nonhazardous solids for environmentally acceptable construction applications.

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.

Roasting mechanism of lightweight low-aluminum–silicon ceramisite derived from municipal solid waste incineration fly ash and electrolytic manganese residue

Municipal solid waste incineration (MSWI) fly ash and electrolytic manganese residue (EMR) belong to hazardous waste, and must be disposed of before processing. It was found that the low content of silicon and aluminum at low roasting temperature can meet the expansion mechanism of lightweight aggregates. A low-aluminum–silicon lightweight ceramisite was successfully prepared from MSWI fly and EMR, the formation mechanism of which was that the viscosity of molten stuffs in pellet was the function of temperature and chemical composition and had enough capacity of capturing the emerged gas over roasting. The resulting ceramisite met with the requirement of Lytag commercial lightweight aggregate. The content of heavy metal in ceramisite accorded with the requirement of soil environmental quality for development GB 36600–2018 Class I, and PCDD/Fs in ceramisite was 2.0 ng I-TEQ/kg, which was safe. The collaboration of thermal simulation and characterization (SEM-EDS, FTIR and XRD) elaborated the formation mechanism of ceramisite, with six stages provided.

Effects of electrolytic manganese residue (EMR) to co‐sintering mechanism of ceramic aggregate

AbstractThe influences of co‐sintering temperature on the physical properties of EMR (electrolytic manganese residue) ceramic aggregate were investigated over the gradient of co‐sintering by EMR, CFA (coal fly ash), and P (perlite) that were used as raw materials. Seven EMR samples were prepared to sinter at different temperatures that were decided by the data of a thermal mass spectrometer, and four ceramic aggregate embryos were sintered at 1120, 1140, 1160, and 1180°C. The mechanisms of co‐sintering temperature action on performance were determined by means of X‐ray diffraction and scanning electron microscopy with energy‐dispersive X‐ray spectroscopy. The optimal temperature of 1160°C and the temperature increment lead to an enhancement of cylinder compressive strength and a damping of 1‐h water absorption, softening coefficient, and grain shape coefficient was discovered. Gypsum of EMR dissolved and exhausted gas during co‐sintering resulted in CaO. The crystalline transformation of wollastonite and gehlenite produced anorthite, which boosts the strength of aggregate and the content of anorthite, was proportional to the co‐sintering temperature and the pressure strength of cylinder. The liquid phase of “overfiring”‐coated crystal contributed to the further improvement of strength, but the aggregate sphere deformation generated a reduction of comprehensive performance. The formation of bustamite calcian in co‐sintered ceramic aggregate realized the solidification of Mn, and the solidification rate of leaching toxicity test was 99.92%, and the absence of radioactivity was demonstrated.

Radiological Atmospheric Risk Modelling of NORM Repositories in Hungary

The human population is continuously exposed to natural radionuclides in environmental elements. The concentration of these nuclides is usually low, but different technological processes and activities can concentrate them in products, by-products, or wastes. These activities are, for example, coal mining, fertilizer production, ore mining, metal production, etc. These materials are labelled as NORM (Naturally Occurring Radioactive Material). The most common method of disposal for NORMs is deposition in different types of depositories. The long-term effects of these depositories on the environment and on human health are hard to estimate. The aim of the study is to assess radiation risk from the five selected NORM depositories (Ajka coal ash, Ajka red mud, Almásfüzitő red mud, Zalatárnok drilling mud, and Úrkút manganese residue) for members of the public and biota. The radionuclide concentrations were determined by HPGe gamma-spectrometry. The measured concentration was between 31 Bq/kg and 1997 Bq/kg for Ra-226, between 33 Bq/kg and 283 Bq/kg for Th-232, and between 48 Bq/kg and 607 Bq/kg for K-40. The dose estimation was investigated using RESRAD-ONSITE and RESRAD BIOTA, which are computer codes developed by the Argonne National Laboratory (USA). RESRAD-ONSITE can estimate the radiation risk from the radionuclides in the contaminated sites. The highest dose was observed in the case of the Ajka coal ash depository–without cover (12.38 mSv/y), and the lowest was in the case of Zalatárnok (0.53 mSv/y). The most significant contributors to the population dose are the uptakes through plants and external pathways, which account for more than 80% of the total dose on average. RESRAD-BIOTA code was used to estimate the radiation exposure of terrestrial organisms (plants and animals). During this work, the values of sum ratio factor (SRF), biota concentration guide (BCG), external dose, internal dose, and total dose were determined.

Co-stabilization/solidification of heavy metals in municipal solid waste incineration fly ash and electrolytic manganese residue based on self-bonding characteristics

Municipal solid waste incineration (MSWI) fly ash and electrolytic manganese residue (EMR) were classified as hazardous waste, must be harmlessly processed prior to subsequent treatment or disposal. The competition between massive free manganese ions of raw EMR and other heavy metals was found, thus raw EMR was pretreated by calcining to eliminate competition of manganese with other heavy metals for stabilizer complexation. MSWI fly ash was successfully solidified with 6% NaH2PO4, 6% H2NCSNH2 and 20% sintered EMR (800 °C). The addition of sintered EMR enhanced solidification/stabilization of heavy metals in fly ash and the resulting product had a higher compressive strength for further reutilization like trench backfilling, structural fill and void filling. The stabilization/solidification mechanism of heavy metals was attributed to the combined interaction of heavy metal precipitation in stabilizers and ion exchange or physical encapsulation in silicate compounds like calcium silicate, which is a feasible and valuable approach to co-disposal of MSWI fly ash and EMR.

Effects of different silicate minerals on silicon activation by Ochrobactium sp. T-07-B.

As a kind of solid waste with a high silicon content, electrolytic manganese residue (EMR) can be utilized as silicon source by plants through bioleaching processes. EMR contains a variety of silicate minerals. In order to determine the source of available silicon in the bioleaching process of EMR, it is necessary to investigate the influence of silicate minerals in EMR on silicon-activating behavior of specific minerals. In this study, Ochrobactium sp. T-07-B was used to conduct bioleaching experiments on five kinds of silicate minerals with different structures (quartz, muscovite, biotite, olivine, and rhodonite); the growth of Ochrobactium sp. T-07-B, their acid- and polysaccharide-producing capacity, and evolution of surface morphology and structure of the silicate minerals in different systems were determined, so as to explore the silicon-activating capacity of Ochrobactium sp. T-07-B and the selectivity toward different minerals in the bioleaching process. Results showed that the effects of Ochrobactium sp. T-07-B for different silicate minerals were obviously different, and the sequence of silicon-activating efficiency from high to low was as follows: muscovite (65.84mg·L-1) > biotite (63.84mg·L-1) > olivine (55.76mg·L-1) > rhodonite (50.98mg·L-1) > quartz (23.63mg·L-1). Results of this study may be of guiding significance for the future research on the silicon-activating behavior of solid waste.

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.