Search Results (75)

Radionuclide-contaminated water is carcinogenic and poses numerous severe health risks and environmental dangers. Thus, effective removal techniques are required to ensure the safety of drinking water sources. This article overviews several methods to remove naturally occurring radioactive materials (NORMs) from water, including adsorption, coagulation, reverse osmosis, ion exchange, electrodialysis, iron manganese filtration, and membrane filtration. A search is conducted in different scientific databases to identify relevant articles, reviews, and studies on removing radionuclides from water. The overarching goal of this article is to deepen the understanding of the techniques available for radionuclide removal from water and to foster the creation of innovative solutions for water contamination concerns. Each technique is examined in terms of its efficiency, cost-effectiveness, and sustainability in removing specific radionuclides from water sources. The advantages and limitations of these techniques are discussed, highlighting the importance of selecting the most appropriate method based on the characteristics of the radionuclides and the water source. Different methods can be combined for the more effective removal of radionuclides from water, such as coagulation and filtration, reverse osmosis, and ion exchange. The treatment of water contaminated with radionuclides requires prior laboratory work and pilot-scale tests to determine the most suitable, cost-effective, and environmentally friendly method. Full article

Manganese monoxide (MnO), a versatile manganese oxide, is highly regarded for its potential to address heavy metal and radioactive contamination effectively. In this study, we investigated the adsorption mechanism of strontium nitrate solution on MnO crystal surfaces using molecular dynamics simulations. We examined the effects of adsorption and diffusion of ions and water molecules on three distinct MnO crystal surfaces. The results revealed significant differences in the adsorption capacities of Sr²⁺, NO₃⁻, and H₂O on the MnO crystal surfaces. The radial distribution function (RDF), the non-bond interaction energy (E_int), and mean square displacement (MSD) data indicate that Sr²⁺ exhibits the strongest interaction with the MnO (111) crystal surface. This results in a shift of Sr²⁺ from outer-sphere adsorption to inner-sphere adsorption. This strong interaction is primarily due to the increase in the number and prominence of non-bridging oxygen atoms on the MnO crystal surfaces. Full article

Advanced water treatment technologies must offer selective, efficient, and cost-effective contaminant removal. In this study, TPB-DMTP-COF-SH, prepared from 1,3,5-tris(4-aminophenyl)benzene (TPB) and 2,5-dimethoxyterephaldehyde (DMTP), was synthesized via a two-step method and applied for the adsorption of aluminum (Al³⁺), iron (Fe²⁺), and manganese (Mn²⁺) ions from water. Adsorption performance was influenced by pH, initial concentration, and contact time, with optimal pH values of 3 for Al³⁺, 8 for Fe²⁺, and 10 for Mn²⁺. The adsorption data followed the Langmuir isotherm model, yielding maximum capacities of 3.27 mg g⁻¹ (Al³⁺), 8.5 mg g⁻¹ (Fe²⁺), and 0.67 mg g⁻¹ (Mn²⁺). Kinetic studies indicated a pseudo-second-order mechanism, suggesting chemisorption as the dominant process. Equilibrium adsorption was reached at 15 min for Al³⁺ and Mn²⁺ and 20 min for Fe²⁺. As a proof of concept, we demonstrate that this thiol-functionalized COF not only effectively removes metals but also offers enhanced processability into composite beads and membranes, making it a strong candidate for real-world water treatment applications. These findings highlight TPB-DMTP-COF-SH as a promising and scalable solution for water purification. Full article

This study presents data on the water quality of the Guarani Aquifer based on samples collected from distinct groundwater wells in the western region of Santa Catarina State, Brazil. Among the analyses performed, the results indicated the need for treatment to ensure suitability for human consumption, particularly concerning Fe³⁺ and Mn²⁺ ions. Accordingly, natural (NCLIN) and activated clinoptilolite (ACLIN) zeolites were evaluated for ion removal from synthetic aqueous solutions through adsorption. NCLIN demonstrated excellent performance in adsorbing Fe³⁺ and Mn²⁺ ions, achieving removal efficiencies of over 98% and 95%, respectively, at a controlled pH of 6.0 (NCLIN) or 4.0 (ACLIN). A non-linear approach to modeling adsorption kinetics indicated that the pseudo-second-order model best represented the experimental data. This finding suggests that the interaction between the adsorbent and Fe³⁺ and Mn²⁺ ions occur through electron sharing and chemisorption. Equilibrium modeling analysis revealed that adsorption on NCLIN occurred in a monolayer, whereas adsorption on ACLIN followed a multilayer pattern. This behavior is attributed to the activation process with H₂SO₄, which led to dealumination and the formation of HSO₃⁻ groups on the adsorbent surface. Full article

Heavy metal pollution in groundwater and the environment poses a serious threat to ecosystems and human health. In particular, heavy metal ions, such as copper (Cu), zinc (Zn) and manganese (Mn), in the leachate of metal mine tailings ponds have attracted much attention due to their high toxicity and bioaccumulation. In order to solve the problem of heavy metal pollution in groundwater caused by leachate from tailings pond of a polymetallic mine, carbon/hydroxyapatite (CHAP) prepared from animal bones was used as the medium material to systematically study its removal effect on heavy metal ions in water under static and dynamic conditions. The static experiment results showed that CHAP had excellent adsorption properties for copper, zinc, manganese and mixed ions, and the adsorption capacities were up to 80 mg/g, 67.86 mg/g and 49.29 mg/g, respectively. Dynamic experiments further confirmed the application potential of CHAP as a Permeable Reactive Barrier (PRB) medium material, which can effectively remove heavy metal ions from flowing water, having a long service life. This study provides a theoretical basis and experimental reference for the in situ remediation of heavy metal-contaminated groundwater and shows the application prospect of CHAP in the field of environmental remediation. Full article

Although the hopcalite catalyst, primarily composed of manganese oxide and copper oxide, has been extensively studied for carbon monoxide (CO) elimination, there remains significant potential to optimize its structure and activity. Herein, Cu-doped Mn₃O₂@MnO₂ catalysts featuring highly exposed interfacial regions were prepared. The correlation between interfacial exposure and catalytic activity indicates that the interfacial region serves as the active site for CO catalytic oxidation. The characteristic adsorption of CO by Cu species significantly enhances the catalytic activity of the catalyst. And XPS and ICP-OES analyses reveal that Cu ions coexist in both the interlayer and lattice of δ-MnO₂. Furthermore, XPS analysis was employed to quantify the average oxidation state (AOS) of Mn and the molar ratios of oxygen species, demonstrating that both surface-adsorbed oxygen and surface lattice oxygen act as reactive oxygen species in the catalytic reaction, playing a crucial role in CO oxidation. Notably, the surface reactive oxygen species influence the adsorption of CO onto Cu species, and the replenishment of these reactive species is identified as the rate-limiting step in the CO catalytic oxidation process. Full article

In this work, the origin of the synergetic effect in mixed Mn_xCo_3-xO₄ oxides with the spinel structure in the CO oxidation reaction was tested. A series of Mn_xCo_3-x oxide catalysts were synthesized by the coprecipitation method with further calcination at 600 °C and varying manganese content from x = 0 to x = 3. The catalysts were characterized using XRD, TEM, N₂ adsorption, TPR, EXAFS, and XPS. The catalytic activity of Mn_xCo_3-x oxide catalysts was tested in CO oxidation reactions. The addition of manganese to cobalt oxide results in the formation of mixed Mn-Co oxides based on a cubic or tetragonal spinel structure, a change in microstructural properties, such as surface area and crystal size, as well as local distortions and a decrease in the surface concentration of Co ions and Co in the octahedral sites in spinel structure; it also decreases catalyst reducibility. For all catalysts, the activity of CO oxidation decreases as follows: Mn_0.1Co_2.9 > Co₃O₄~Mn_0.3Co_2.7 > Mn_0.5Co_2.5 > MnO_x > Mn_0.7Co_2.3 > Mn_0.9Co_2.1~Mn_1.1Co_1.9~Mn_2.5Co_0.5 > Mn_2.9Co_0.1 > Mn_1.7Co_1.3 > Mn_2.1Co_0.9 > Mn_1.3Co_1.7~Mn_1.5Co_1.5~Mn_2.3Co_0.7. The Mn_0.1Co_2.9 catalyst displays the best catalytic activity, which is attributed to its small crystal size and the maximum surface ratio between Co³⁺ and Co²⁺. A further increase in the manganese content (x > 0.3) provokes drastic changes in the catalytic properties due to a decrease in the cobalt content on the surface and in the volume of mixed oxide, changes in the oxidation states of cations, and structure transformation. Full article

A carbon-based material was synthesized using potato peels (BPP) and banana pseudo-stems (BPS), both of which were modified with manganese to produce BPP-Mn and BPS-Mn, respectively. These materials were assessed for their ability to activate peroxymonosulfate (PMS) in the presence of MnCO₃ to degrade acetaminophen (ACE), an emerging water contaminant. The materials underwent characterization using spectroscopic, textural, and electrochemical techniques. Manganese served a dual function: enhancing adsorption properties and facilitating the breaking of peroxide bonds. Additionally, carbonate ions played a structural role in the materials, transforming into CO₂ at high temperatures and thereby increasing material porosity, which improved adsorption capabilities. This presents a notable advantage for materials that have not undergone de-lignification. Among the materials tested, BPS exhibited the highest efficiency in the carbocatalytic degradation of ACE, achieving a synergy index of 1.31 within just 5 min, with 42% ACE degradation in BPS compared to BPS-Mn, which achieved 100% ACE removal through adsorption. Reactive oxygen species such as sulfate, hydroxyl, and superoxide anion radicals were identified as the primary contributors to pollutant degradation. In contrast, no degradation was observed for BPP and BPP-Mn, which is likely linked to the lower lignin content in their precursor material. This work addressed the challenge of revalorizing lignocellulosic waste by highlighting its potential as an oxidant for emerging pollutants. Furthermore, the study demonstrated the coexistence of various reactive oxygen species, confirming the capacity of carbon-based matrices to activate PMS. Full article

In recent years, with the development of the new energy industry, lithium resources need to be supplied in large quantities. The lithium-ion sieve (LIS) is regarded as an ideal adsorbent for recovering lithium resources from brine because of its excellent lithium adsorption capacity and structural stability. However, because it is powdery after molding, and there will be problems such as dissolution loss of manganese, which limits its industrial development. In this study, in the process of preparing hydrogels of acrylic acid (AA), acrylamide (AM) and chitosan (CS), an LIS hydrogel with high mechanical properties, strong adsorption capacity and low dissolution loss was prepared by doping LIS and Al ions. Among them, the stress of the prepared chitosan–acrylic acid–acrylamide hydrogel (PASA-1) with an Al doping content of 1% reached 603 KPa, and the maximum strain reached 189%, which showed excellent damage resistance. In addition, the adsorption performance of PASA-1 reached 43.2 mg/g, which was excellent, which was attributed to the addition of Al ions, which inhibited the dissolution loss of manganese ions. This idea has great potential in the direction of lithium resource recovery and provides a new method for the use of hydrogel in the direction of lithium-ion sieves. Full article

Bioremediation of acid mine drainage (AMD) was often challenged by poor tolerance of sulfate-reducing bacteria (SRB) to heavy metals and low bioactivity. The highly active immobilized particles with Fe⁰/Fe²⁺ enhanced SRB (Fe^0/2+-SRB) were prepared by the microorganism immobilization technique. Three dynamic columns were constructed to investigate the adsorption capacity of Fe^0/2+-SRB for Mn²⁺ under varying adsorption layer heights, inflow velocity, and initial Mn²⁺ concentrations. The role of each matrix material in the immobilized particles was explored, the mechanism of AMD remediation by Fe^0/2+-SRB was revealed, and the adaptability of Fe^0/2+-SRB to AMD under various initial conditions was investigated. The results showed that the prepared Fe^0/2+-SRB exhibited a well-developed surface pore structure. When the adsorption layer height was 200 mm, the influent flow rate was 5 × 10⁻⁵ m³/s, and the initial manganese ion concentration was 10 mg/L, the maximum dynamic adsorption capacities (q_e) of Mn²⁺ for each dynamic column were 7.8430, 4.7627, and 8.7677 mg/g, respectively. Compared to dynamic columns 1# and 2#, dynamic column 3# showed the best performance in treating AMD, and the Thomas model effectively described the adsorption kinetics of Mn²⁺ by Fe^0/2+-SRB(3#). Microstructural analysis indicated that chemical adsorption, ion exchange, dissimilation–reduction reaction, and surface complexation occurred between the various matrix materials in Fe^0/2+-SRB(3#). Mn²⁺ was primarily removed in the form of metal sulfide (MnS), and Fe⁰/Fe²⁺ could promote the dissimilatory reduction of SO₄²⁻ by SRB to form S²⁻. Fe^0/2+-SRB(3#) was able to adapt to AMD with initial conditions of pH was 2~4, SO₄²⁻ < 2500 mg/L, and Mn²⁺ < 20 mg/L. The research results provide new insights into the remediation of AMD, using a combined microbial-adsorption technology. Full article

Silicon (Si) is one of the main biogenic elements in the aquatic ecosystem of lakes, significantly affecting the primary productivity of lakes. Lake sediment is an important sink of Si, which exists in different Si forms and will be released and participate in the recycling of Si when the sediment environment changes. Compared to carbon (C), nitrogen (N) and phosphorus (P), the understanding of different Si forms in sediments and their biogeochemical cycling is currently insufficient. Dianchi Lake, a typical eutrophic lake in southwest China, was selected as an example, and the contents of different Si forms and biogenic silicon (BSi), as well as their correlations with total organic carbon (TOC), total nitrogen (TN), and chlorophyll a in the surface sediments, were systematically investigated to explore Si’s recycling characteristics. The results showed that the coupling relationship of the four different Si forms in the surface sediments of Dianchi Lake was poor (p > 0.05), indicating that their sources were relatively independent. Moreover, their formation may be greatly influenced by the adsorption, fixation and redistribution of dissolved silicon by different lake substances. The contents of different Si forms in the surface sediments of Dianchi Lake were ranked as iron-manganese-oxide-bonded silicon (IMOF-Si) > organic sulfide-bonded silicon (OSF-Si) > ion-exchangeable silicon (IEF-Si) > carbonate-bound silicon (CF-Si). In particular, the contents of IMOF-Si and OSF-Si reached 2983.7~3434.7 mg/kg and 1067.6~1324.3 mg/kg, respectively, suggesting that the release and recycling of Si in surface sediments may be more sensitive to changes in redox conditions at the sediment–water interface, which become the main pathway for Si recycling, and the slow degradation of organic matter rich in OSF-Si may lead to long-term and continuous endogenous Si recycling. The low proportion (0.3~0.6%) and spatial differences of biogenic silicon (BSi) in the surface sediments of Dianchi Lake, as well as the poor correlation between BSi and TOC, TN, and chlorophyll a, indicated that the primary productivity of Dianchi Lake was still dominated by cyanobacteria and other algal blooms, while the relative abundance of siliceous organisms such as diatoms was low and closer to the central area of Dianchi Lake. Additionally, BSi may have a faster release capability relative to TOC and may participate in Si recycling. Full article

This study aimed to assess the sorption capacity of a natural sorbent, specifically birch bark (BB), and its modification using chemical reagents, including nitric and hydrochloric acid, sodium hydroxide, and chloride. The objective of the chemical modification was to enhance the sorption capacity of the heavy metals cadmium(II), chromium(VI), and manganese(II). The most effective modification for adsorbing cadmium and manganese from aqueous solutions was achieved by treating the sorbent with a 0.1 M sodium hydroxide solution (BBNa). Conversely, in the case of chromium, each modification adversely affected its adsorption by the sorbent. Concentrations of the solutions were analyzed using atomic absorption spectrometry at appropriate time intervals. The adsorption process was described using Langmuir, Freundlich, and Temkin isotherms. The Freundlich isotherm provided the best fit for cadmium and chromium (R² = 0.988 and 0.986, respectively), while the Langmuir isotherm was most suitable for manganese (R² = 0.996). The sorption capacity varied for each metal ion: Cd (II)—33.13 mg/g, Cr (VI)—35.98 mg/g, and Mn (II)—24 mg/g for the highest concentration tested. This study employed pseudo–first-rate order, pseudo–second-rate order model kinetics, and the Weber–Morris model to examine the adsorption kinetics. The pseudo–second-rate order kinetics demonstrated the best fit (R² > 0.94) for each heavy metal, which underlines the process’s chemical nature. Full article

Cadmium (Cd) water pollution threatens environmental systems and human health. Adsorption is the preferred method for purifying water bodies polluted by Cd, and the development of effective adsorption materials is critical. The performance of original phosphate rock powder (PRP) as an adsorption medium for purifying water bodies polluted by Cd was compared with that of phosphate rock powder modified with fulvic acid, chitosan, MnO₂, and sulfhydryl, respectively, and their appearance and adsorption properties were investigated. The surface structures of all modified powders were rougher than the original, and their functional groups were richer. The greatest Cd²⁺ adsorption capacity, 1.88 mg g⁻¹, was achieved with chitosan-modified PRP (CMPRP). This was 106.59% greater than that of PRP. The capacities of fulvic acid and MnO₂ were 15.38% and 4.40% greater than that of the original, respectively. When the fulvic acid-modified PRP, CMPRP, and manganese dioxide PRP reached adsorption equilibrium, the removal rates of Cd²⁺ were 51.86%, 93.26%, and 46.70%, respectively. Moreover, the removal rate of Cd²⁺ by CMPRP was 104.43% higher than that of PRP. The main Cd²⁺ adsorption mechanisms for the MPRPs were electrostatic interactions, ion exchange, co-precipitation, and complexation. Moreover, the processing of the phosphate rock powder was straightforward, harmless to the environment, and could be effectively used for the removal of Cd. These results show that CMPRP is promising as a new adsorption material to treat Cd-contaminated water. Full article

Metal–organic frameworks (MOFs) are porous materials assembled using metal and organic linkers, showing a high specific surface area and a tunable pore size. Large portions of metal open sites in MOFs can be exposed to electrolyte ions, meaning they have high potential to be used as electrode materials in energy storage devices such as supercapacitors. Also, they can be easily converted into porous metal oxides by heat treatment. In this study, we obtained high energy storage performance by preparing electrode materials through applying heat treatment to manganese MOFs (Mn-MOFs) under air. The chemical and structural properties of synthesized and thermally treated Mn-MOFs were measured by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The surface area and porosity were investigated by nitrogen adsorption/desorption isotherms. The electrochemical properties were studied by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) using a three-electrode cell. It was found that Mn-MOF electrodes that underwent heat treatment at 400 °C under air consisted of Mn₂O₃ with high specific surface area and porosity. They also showed a superior specific capacitance of 214.0 F g⁻¹ and an energy density value of 29.7 Wh kg⁻¹ (at 0.1 A g⁻¹) compared to non-treated Mn-MOFs. Full article

The present study focuses on the synthesis of a manganese dioxide lithium ion sieve and its application for the extraction of lithium from coal fly ash. The preparation and adsorption experiments of the manganese dioxide lithium ion sieve were carried out using the orthogonal method, while the HCl elution experiment was carried out using the single factor method. The results showed that the optimum preparation conditions under which the average lithium adsorption efficiency reached 99.98% were a 10:1 mass ratio of manganese dioxide to lithium hydroxide, calcination at 800 °C for 60 min, 1.5 mol/L HCl, soaking for 24 h and stirring for 18 h. Additionally, the optimum adsorption efficiency was observed with an adsorption time of 30 min, KOH pH of 8 and KOH scrubbing time of 10 min, resulting in 100% lithium adsorption efficiency. The optimum elution conditions for lithium were determined to be an HCl concentration of 0.01 mol/L and an elution time of 40 min, giving 100% lithium elution efficiency. Full article