Sb Species Research Articles

Tailoring Ruthenium(II) and Rhenium(I) Complexes for Turn-On Luminescent Sensing of Antimony(III)

Antimony (Sb) is currently a widespread element with key roles in telecommunication, sustainable energy, and military industries, among others. Its significant toxicity determines the need to realize sensors for water, air, and soil and the industrial process monitoring of Sb species. Unfortunately, no antimony sensors exist so far, and just laboratory analysis methods are in use. We aimed to contribute to the development of optical sensors for the metalloid by tailoring, for the first time, luminescent Ru(II) and Re(I) polypyridyl complexes to probe and quantify the presence of Sb(III). The molecular design of the complexes includes the multifunctional Sb-binding 2-(2,2′-bithien-5-yl)-1H-imidazo[4,5-f]-1,10-phenanthroline (btip) ligand that ensures the molecular binding of Sb(III) in organic media. The Ru(II)-btip complex is additionally endowed with one 2,2′-bipyrazine (bpz) or two 1,4,5,8-tetraazaphenanthrene (tap) ligands, namely [Ru(bpz)(btip)2]2+ and [Ru(tap)2(btip)]2+, that boost the excited state oxidation potential of the probe, leading to an intramolecular photoinduced electron transfer from btip to the Ru(II) core. The latter is suppressed upon interaction with Sb(III), leading to an 11-fold increase in both the luminescence intensity and lifetime of [Ru(bpz)(btip)2]2+ in the presence of ca. 50 μmol L−1 of SbCl3 in organic medium. The fluorescence intensity of [Re(CO)3(H2O)(btip)]+ also increases upon interaction with Sb(III) but to a much lesser extent due to the intraligand π*→π nature of its emission compared to the Ru(II) ligand-to-metal excited state deactivation. However, the weak π*→d emission band in the red spectral region of the former is quenched by the semimetallic element. The sensing mechanisms of the Ru(II)- and Re(I)-btip probes that allow luminescence intensity (Ru, Re), ratiometric (Ru), and lifetime measurements (Ru) are compared and discussed in this initial solution sensing study.

Mechanistic investigation of the suppressed N2O formation during the low-temperature NH3-SCR over the Sb-modified Mn/Ti catalyst

The formation of N2O during the NH3-SCR reaction over the Mn-based is one of the crucial factors limiting the industrial application of Mn-based catalysts. In this work, the Sb-modified Mn/Ti catalyst was prepared by the ultrasonic assistance impregnation method to control the formation of N2O during the NH3-SCR reaction. The preferred Mn3Sb/Ti catalyst had over 80 % NOx conversion at 150–300 °C, and more than 80 % N2selectivity at 150–250 °C, which were higher than that of the Mn/Ti catalyst at the same temperature window. A series of performance experiments showed that the Sb modification inhibited the oxidation of NH3to N2O and suppressed the N2O produced by the E-R mechanism in the NSCR reaction, which is the main pathway for N2O generation. Moreover, the presence of NO inhibited the oxidation of NH3 to generate N2O over the Mn3Sb/Ti catalyst. Based on the physical–chemical characterizations and DFT calculations, it was revealed that the introduced Sb species achieves a trade-off between redox ability and surface acidity over the Mn3Sb/Ti catalyst, which is beneficial to enhance the NH3-SCR performance and simultaneously suppress the over-oxidation of NH3. The high content of Mn3+caused by the electron transfer through the redox cycle of Sb3++Mn4+→Sb5++Mn3+ was beneficial in decreasing the N2O formation.The formation of NH speciesis inhibited on the Mn3Sb/Ti catalyst with a higher energy barrier of the NH2* conversion to NH* species due to the Sb modification. Meanwhile, the energy barrier of NH3*→NH2* is decreased and the energy barrier of NH2*+NO → N2 + H2O is lower than that of NH2*→NH* over the Sb-modified catalyst, indicating that the NH3-SCR reaction is more favorable than the formation of N2O on the Mn3Sb/Ti catalyst.

Alteration of soil microbiomes in an arsenic and antimony co-contamination zone after dam failure

Arsenic (As) and antimony (Sb), two toxic metal(loid)s, behave similarly and commonly occur in mine tailings. Yet, responses of microbes to As and Sb co-contamination in tailings dam failure-affected area remain limited. Herein, soil microbiomes (archaea, bacteria and fungi) across two contrasting sites (tailing-contaminated farmland and nearby undisturbed forestland) at a Sb-Au mining district in Chizhou, China were investigated by high-throughput sequencing. Results showed that As and Sb occurred mainly in the residual form, accounting for 55.82% and 52.04%, respectively. The bioavailable form was 12.77% and 10.39% in contaminated farmland compared to 13.31% and 11.66% in undisturbed forestland, respectively. Contrary to archaea and fungi, bacterial alpha-diversity significantly increased in contaminated farmland. The taxa-taxa interactions in archaea were most robust, followed by bacteria; and fungi were the weakest, which was corresponding to the habitat niche breadth. Microbial communities were affected by the deterministic processes with a modified stochasticity ratio (MST) value of 36.36%, whereas more stochasticity (MST = 49.71%) was raised in contaminated farmland than in undisturbed forestland (MST = 36.98%). The microbial function based on taxonomy-based inference indicated that nitrogen and carbon metabolisms associated with archaea and bacteria increased in contaminated farmland, as well as plant pathogen, wood saprotroph and endophyte related with fungi. The turnover of soil microbiomes was tightly correlated with As and Sb speciation. Collectively, this study reveals that the soil microbial survival strategies to As-Sb co-contamination after dam failure, providing guidance for the development of bioremediation and tailings management strategies.

Antimony removal using zero-valent iron-manganese bimetallic nanomaterial: Adsorption behavior and mechanism

Although the effectiveness of zero-valent iron (ZVI) and zero-valent manganese (ZVMn) in heavy metal removal is well-established, their combined synergistic potential for antimony (Sb) remediation from wastewater has remained largely unexplored. Addressing this gap, this study introduced a magnetic zero-valent iron-manganese bimetallic material (ZVIM), synthesized via the borohydride reduction method, to investigate its capabilities and underlying mechanisms for Sb reduction and adsorption. The ZVIM, characterized by a high specific surface area of 220 m²/g, exhibited a high adsorption capacity (614.6 mg/g for Sb(III) and 241.7 mg/g for Sb(V)), facilitating over 96.7 % removal for both Sb(III) and Sb(V). The adsorption conformed to the pseudo-second-order kinetic model, and the isotherm data aligned with the Freundlich model, indicative of a heterogeneous adsorption process. The removal of Sb(III) predominantly occurred via surface complexation and electrostatic adsorption to the positively charged ZVIM surface, accompanied by a partial oxidation of Sb(III) to Sb(V). In contrast, the elimination of Sb(V) was primarily facilitated through surface complexation mechanism, encompassing both reduction and electrostatic adsorption. The outcomes of this study shed light on the intricate interactions between Sb species and the ZVIM, revealing the material as a promising candidate for the efficacious removal of Sb from wastewater.

Remediation of As, Sb, and Pb co-contaminated mining soils by using Fe/C based solid wastes: Synergistic effects and field applications

Existing passivators for mining soil remediation suffer from high-costs and detriment to soil health. Here we reported the iron-carbon (Fe/C) based passivators (high-Fe/C, mid-Fe/C, and low-Fe/C) prepared by composing of high-Fe steel slag, high-C coal fly ash and FeSO4 for the remediation of As, Sb, and Pb co-contaminated mining soil. High-Fe/C, and mid-Fe/C addition (5 % dosage) for 30 days decreased soil available As, Sb, and Pb content by 85.5–87.3 %, 58.3–71.2 %, and 55.3–65.7 %, respectively, with only slight degradation of stabilization efficiency with 210 days. Moreover, the labile fractions of As, Sb and Pb were transformed to residual state. After high-Fe/C and mid-Fe/C amendment, the relative abundance of microbial community (bacteria and fungi) and soil fertility were enhanced. Facilitated by the Fe/C micro-electrolysis effect, As, Sb and Pb species were well passivated via adsorption with C-containing functional groups, and precipitation (Fe-As/Sb and Ca-Sb) mechanisms. Noteworthy, the increased soil organic matter (OM), cation exchange capacity (CEC) and microbial activity also enhanced the stabilization of As, Sb, and Pb. Field application results demonstrated that the stabilization efficiency of available As and TCLP-As/Sb/Pb was over 80 % after mid-Fe/C amendment. Fe/C based solid wastes hold the potential for being cost-effective in the remediation of mining soil while achieving large-scale utilization of solid wastes.

Biochar-Sulfate Reducing Bacteria synergy: A green approach for antimony removal and recovery from high-concentrated waters

Environments with elevated antimony (Sb) levels often result from industrial and mining activities, causing harm to ecosystems due to the inherent toxicity. Traditional treatments aim to eliminate or decrease Sb toxicity, yet they often result in the generation of secondary pollution. This study explores a novel approach for enhancing biological sulfate-reduction by biochar addition to cope with high Sb concentrations. Moreover, this research postulates sulfate-reduction bioprocess as a feasible alternative to obtain valuable antimony sulfide. The findings indicate that sulfate reduction effectively removes antimony, particularly at high concentrations, using a non-specialized inoculum. Biochar plays a pivotal role in enhancing sulfate-reduction rates, reducing lag-phase periods, and enriching the microorganisms responsible for sulfate reduction.Interestingly, lower concentrations of Sb(III) (5–40 mg/L) and Sb(V) (5–100 mg/L) exhibited a lower removal percentage compared to higher concentrations of Sb(III) (80–500 mg/L) and Sb(V) (200–1000 mg/L). This phenomenon was attributed to the excess sulfide hindering the equilibrium of the first-order reaction at lower concentrations, while at higher concentrations, the reaction proceeded more rapidly. A combination of biochemical and physicochemical reactions facilitated the removal of >95 % Sb(III) and >97 % Sb(V) using biochar.Furthermore, various taxa displayed a significant logarithmic rate of change in their abundance, influenced by the application of biochar or the introduction of distinct antimony species. The biogenic sulfide generated through the sulfate reduction process reacted with the Sb species, resulting in the precipitation of stibnite (Sb2S3), Na3SbS3, and Na3SbS4. These precipitates are considered crucial precursors in electronic applications.In conclusion, this study constitutes a pioneering exploration of elevated antimony (Sb) concentrations under sulfate-reducing conditions, significantly contributing to an advancement of knowledge in the application of biological processes.

Fast and efficient remediation of antimony-contaminated surface water and field soil using alumina supported Fe–Mn binary oxide

Antimony (Sb) pollution in surface water and soil has earned extensive attention. Our previous study synthesized a new class of alumina supported Fe–Mn binary oxide (Fe–Mn@Al2O3) and found that MnO2 in the composite oxidized Sb(III) to Sb(V) and FeOOH and Al2O3 played an indispensable role in adsorption of Sb(III) and Sb(V). This study further explored the removal of Sb in surface water and in situ sequestration of Sb in Sb-contaminated field soil via Fe–Mn@Al2O3. Sb removal from water was pH independent and the removal efficiencies of Sb(III) and total Sb kept constant at 95.4% and 60.5%, respectively, over a pH range of 5.0–10.0. Increasing dissolved organic matter (DOM) from 0 to 22.8 mg/L had negligible effect on Sb(III) removal whereas inhibited the total Sb removal from 60.5% to 51.2%. Dissolved oxygen cannot oxidize aqueous Sb(III), yet, enhanced the Sb(III) removal whereas decreased the total Sb removal. The composite performed well in natural surface water with high DOM and inorganic ligands. In addition, the composite effectively immobilized Sb in field soil. 5% of the composite significantly inhibited the H2SO4 and HNO3 leachable Sb by 93.6% after 30 d. The amendment transformed the Sb speciation from more easily available fractions (i.e., exchangeable, carbonate-bound, and Fe–Mn oxides-bound species) into more stable fractions (i.e., organic material bound and residual species), leading to declined Sb bioaccessibility and reduced environmental risk. The composite facilitated a long-term stability of Sb in soil. The study demonstrated an easy, fast, and effective strategy for efficient immobilization of Sb in water and soil.

Investigating Cu-Site Doped Cu-Sb-S Nanoparticles Using Photoelectron and Electron Paramagnetic Resonance Spectroscopy.

Tetrahedrite (Cu12Sb4S13) and famatinite (Cu3SbS4) are good candidates for green energy applications because they possess promising thermoelectric and photovoltaic properties as well as contain earth-abundant and nontoxic constituents. Herein, X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and electron paramagnetic resonance spectroscopy (EPR) methods examined inherent electronic properties and interatomic magnetic interactions of Cu-site doped tetrahedrite and famatinite nanomaterials. An energy-efficient modified polyol method was utilized for the synthesis of tetrahedrite and famatinite nanoparticles doped on the Cu-site with Zn, Fe, Ni, Mn, and Co. This is the first parallel study of tetrahedrite and famatinite nanomaterials with XPS, UPS, and EPR methods alongside a systematic analysis of dopant-dependent effects on the electronic structure and magnetic interactions for each material. XPS showed that the Cu and Sb species in tetrahedrite and famatinite possess different oxidation states, while UPS characterization reveals larger dopant-dependent shifts in the work function for tetrahedrite nanoparticles (4.21 to 4.79 eV) than for famatinite nanoparticles (4.57 to 4.77 eV). Finally, all famatinite nanoparticles display an EPR signal, indicating trace amounts of paramagnetic Cu(II) present below the detection limit of XPS. For tetrahedrite, EPR signatures were observed only for the Zn-doped and Mn-doped nanoparticles, suggesting signal broadening from Cu-Cu spin exchange or spin-lattice relaxation. This study demonstrates the complementary nature of XPS and EPR techniques for studying the oxidation states of metals in solid-state nanomaterials. Comparing the electronic and magnetic properties of tetrahedrite and famatinite while studying the impact of dopant incorporation will guide future endeavors in designing sustainable, high-performance materials for renewable energy applications.

Decomposition of waterside plants greatly affects the transformation and mobility of sedimentary antimony in water–sediment systems after emergency treatment: A microcosm study

Polyferric sulfate (PFS) coagulation has proven to be effective in addressing antimony (Sb) water pollution accidents; however, the impact of waterside plant decomposition on its effectiveness has not been adequately elucidated. This study investigated the effects of Alternanthera philoxeroides (AP) and Digitaria sanguinalis (DS) decomposition on Sb cycling after PFS treatment. Without plant decomposition, the Fe(OH)3 hydrolysate-associated Sb remained stable, and the sediment continued to exhibit Sb sink properties. Plant residue decomposition facilitated sedimentary Sb release, and DS decomposition had a greater impact than AP decomposition. The strong decomposition phases triggered abiotic/biotic reduction processes, leading to Fe(OH)3 dissolution and subsequent Sb(V) release. Concurrently, sulfate reduction and dissolved organic matter (DOM) release regulated Sb mobility. In addition, Sb(V) reduction occurred, and Sb(III) was elevated in the overlying water. The Sb(III) levels gradually decreased during the later aerobic stages, however, did not completely disappear within a short timeframe. Furthermore, the role of the sediment as an Sb sink was significantly hindered, maintaining relatively high levels of dissolved Sb. Sedimentary Sb speciation analysis revealed that plant decomposition induced a shift in Fe-oxyhydroxide-bound Sb to more bioavailable and stable fractions. Our results indicate that plant residue decomposition easily deteriorates PFS efficiency and increases the risk of secondary Sb pollution in water–sediment systems.

Enhanced nitrogen electroreduction to ammonia activities on Sb2S3 electrocatalyst by sulfur defects coupled with carbon doping

Exploiting effective, robust while cheap catalysts for the nitrogen reduction reaction (NRR) is of great significance in the scalability and renewability of electrochemical NH3 synthesis. Herein, a synergetic strategy of C dopants and S vacancies was employed into Sb2S3 (marked as C-Sb2S3-x) to boost the electrochemical NRR performance. The induced effects of C dopants and S vacancies of Sb2S3 on the physical and electrochemical behaviors were throughly investigated. Experiments verify that, the content of low oxidation state in Sb species are remarkably enhanced after introducing C dopants and S vacancies, this facilitate the enhanced electric conductivity and NRR activities of C-Sb2S3-x, together with the encouraged reaction kinetics. The prepared C-Sb2S3-x delivered an optimized NH3 yield rate of 47.2 μg h−1 mg−1cat. at −0.6 V along with a high Faradaic efficiency value of 6.4 % at −0.5 V in acid, outperforming than those of Sb2S3 and most disclosed sulfid NRR electrocatalysts. Density functional theory calculations validate that, cooperation of C doping and S vacancy could achieve the elevated NH3 yield rate, Faradaic efficiency as well as competitive stability. This approach puts forward an effective strategy for transition metal compounds to be more suitable for efficient electrocatalysis.

Characteristics of Pollution and Microbial Community Structure in the Antimony Mining Area of Longnan, Gansu Province

Antimony （Sb） is a major pollutant that poses a serious threat to the environment in the mining and processing of nonferrous metals, coexisting with sulfide and oxide of arsenic （As）. Microorganisms play an important role in the migration, transformation, and repair of metals in soil. The ecological effects of bioavailable Sb and As on the microbial community in antimony mining areas（mining and smelting areas）are still poorly understood. The Wenzel method and high-throughput 16S rDNA amplicon were used to characterize soil pollution characteristics in different functional areas, and the relationship between the bacterial community and bioavailable concentrations have been investigated comprehensively. The results showed that： Chemical speciation of Sb and As were amorphous, and poorly crystalline hydrous oxides of Fe and Al （F3） &gt; well-crystallized hydrous oxides of Fe and Al （F4） &gt; residual phases （F5） &gt; specifically adsorbed （F2） &gt; non-specifically adsorbed （F1）. According to the estimation of the potential ecological risk index （RI） and geo-accumulation index （Igeo）, the Sb pollution degree was： smelting area &gt; mining area &gt; contrast area, in which the smelting area showed serious pollution, and the mining area showed moderate to severe pollution. The As pollution degree was： mining area &gt; smelting area &gt; contrast area, in which the mining area and smelting area showed moderate to severe pollution. High-throughput 16S rDNA amplicon showed that Proteobacteria was the most abundant phylum in mining and smelting areas； Kaistobacter, Pseudomonas, Sphingomonas, and Lysobacter were the most abundant microbial genera； Geobacter and Luteolibacter had a high LDA score in mining areas； and Thiobacillus had a high LDA score in antimony-contaminated areas. Spearman correlation analysis, variation partitioning analysis （VPA）, and random forest （RF） analysis showed that Sb, As, bioavailable antimony [Sb （Bio）], and bioavailable arsenic [As （Bio）]were the main factors affecting the microbial community structure in different functional areas of antimony ore. Redundancy analysis （RDA） indicated that Sb and its bioavailable concentrations showed uniformly negative associations with the relative abundance of bacteria Nitrospirae and showed a significant positive correlation with Thiobacillus （P<0.05）. The in-depth research on the ecological effects of bioavailable Sb and As on the bacterial community provides references and new perspectives for environmental monitoring and management.

Optimizing Antimony Speciation Analysis via Frontal Chromatography-ICP-MS to Explore the Release of PET Additives.

Antimony (Sb) contamination poses significant environmental and health concerns due to its toxic nature and widespread presence, largely from anthropogenic activities. This study addresses the urgent need for an accurate speciation analysis of Sb, particularly in water sources, emphasizing its migration from polyethylene terephthalate (PET) plastic materials. Current methodologies primarily focus on total Sb content, leaving a critical knowledge gap for its speciation. Here, we present a novel analytical approach utilizing frontal chromatography coupled with inductively coupled plasma mass spectrometry (FC-ICP-MS) for the rapid speciation analysis of Sb(III) and Sb(V) in water. Systematic optimization of the FC-ICP-MS method was achieved through multivariate data analysis, resulting in a remarkably short analysis time of 150 s with a limit of detection below 1 ng kg-1. The optimized method was then applied to characterize PET leaching, revealing a marked effect of the plastic aging and manufacturing process not only on the total amount of Sb released but also on the nature of leached Sb species. This evidence demonstrates the effectiveness of the FC-ICP-MS approach in addressing such an environmental concern, benchmarking a new standard for Sb speciation analysis in consideration of its simplicity, cost effectiveness, greenness, and broad applicability in environmental and health monitoring.

Tissue-specific deposition, speciation and transport of antimony in rice.

Rice (Oryza sativa) as a staple food is a potential intake source of antimony (Sb), a toxic metalloid. However, how rice accumulates this element is still poorly understood. Here, we investigated tissue-specific deposition, speciation, and transport of Sb in rice. We found that Sb(III) is the preferential form of Sb uptake in rice, but most Sb accumulates in the roots, resulting in a very low root-to-shoot translocation (less than 2%). Analysis of Sb deposition with laser ablation-inductively coupled plasma-mass spectrometry showed that most Sb deposits at the root exodermis. Furthermore, we found that Sb is mainly present as Sb(III) in the root cell sap after uptake. Further characterization showed that Sb(III) uptake is mediated by Low silicon rice 1 (Lsi1), a Si permeable transporter. Lsi1 showed transport activity for Sb(III) rather than Sb(V) in yeast (Saccharomyces cerevisiae). Knockout of Lsi1 resulted in a significant decrease in Sb accumulation in both roots and shoots. Sb concentration in the root cell sap of two independent lsi1 mutants decreased to less than 3% of that in wild-type rice, indicating that Lsi1 is a major transporter for Sb(III) uptake. Knockout of Lsi1 also enhanced rice tolerance to Sb toxicity. However, knockout of Si efflux transporter genes, including Lsi2 and Lsi3, did not affect Sb accumulation. Taken together, our results showed that Sb(III) is taken up by Lsi1 localized at the root exodermis and is deposited at this cell layer due to lack of Sb efflux transporters in rice.

Speciation of antimony and vanadium in municipal solid waste incineration ashes analyzed by XANES spectroscopy

The use of ashes from municipal solid waste incineration as secondary building materials is an important pillar for the circular economy in Germany. However, leaching of potential toxic elements from these materials must be at environmentally acceptable levels. Normally, a three-month ageing period immobilizes most hazardous heavy metals, but antimony (Sb) and vanadium (V) showed previously unusual leaching. In order to clarify the mechanisms, we analyzed the Sb and V species in various bottom and fly ashes from municipal waste incineration by XANES spectroscopy. Antimony oxidizes from Sb(+ III) species used as flame retardants in plastics to Sb(+ V) compounds during waste incineration. However, owing to the similarity of different Sb(+ V) compound in the Sb K- and L-edge XANES spectra, it was not possible to accurately identify an exact Sb(+ V) species. Moreover, V is mainly present as oxidation state + V compound in the analyzed ashes. However, the coarse and magnetic fraction of the bottom ashes contain larger amounts of V(+ III) and V(+ IV) compounds which might enter the waste incineration from vanadium carbide containing steel tools. Thus, Sb and V could be critical potential toxic elements in secondary building materials and long-term monitoring of the release should be taken into account in the future.

Effective immobilization and biosafety assessment of antimony in soil with zeolite-supported nanoscale zero-valent iron

Antimony (Sb) contamination in certain areas caused by activities such as antimony mining and smelting poses significant risks to human health and ecosystems. In this study, a stable composite material consisting of natural zeolite-supported nanoscale zero-valent iron (Z-ZVI) was successfully prepared. The immobilization effect of Z-ZVI on Sb in contaminated soil was investigated. Experimental results showed that Z-ZVI exhibited superior performance compared to pure nano zero-valent iron (nZVI) in terms of stability, with a lower zeta potential (−25.16 mV) at a pH of 7 and a higher specific surface area (54.54 m2/g). It can be easily applied and dispersed in contaminated soils. Additionally, Z-ZVI demonstrated a more abundant porous structure. After 60 days of treatment with 3% Z-ZVI, the leaching concentration of Sb in the contaminated soil decreased from 1.32 mg/L to 0.31 mg/L (a reduction of 76%), and the concentration of available Sb species decreased from 19.84 mg/kg to 0.71 mg/kg, achieving a fixation efficiency of up to 90%. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis confirmed the effective immobilization of Sb in the soil through reduction of antimonate to antimonite, precipitation, and adsorption processes facilitated by Z-ZVI. Moreover, the addition of Z-ZVI effectively reduced the bioavailability of Sb in the contaminated soil, thereby mitigating its toxicity to earthworms. In conclusion, Z-ZVI can be utilized as a promising material for the safe remediation and antimony and other heavy metal-contaminated soils.

The removal of Sb from mine wastewater using biosynthesized Fe-Mn nanoparticles: Function and mechanism

Antimony (Sb) in mine wastewater poses a serious threat to surrounding ecosystems. In this study, biosynthesized iron-manganese nanoparticles (Fe-Mn NPs) were devised to remove Sb species. The resultant removal efficiencies were 100% for Sb(III) and 82.6% for Sb(V) utilizing a Sb(III) and Sb(V) concentration of 1 mg·L−1. To understand the removal process, Fe-Mn NPs before and after exposure to Sb species were characterized by various advanced techniques, which indicated that while both Sb(III) and Sb(V) were adsorbed onto the surface of Fe-Mn NPs, Sb(III) was also partly oxidized to Sb(V). Furthermore, removal of both Sb(III) and Sb(V) followed pseudo-second-order kinetics and best fit the Freundlich adsorption isotherm model, suggesting that the removal process involved non-homogeneous chemisorption. These studies provided the evidence for an adsorption and oxidation mechanism for Sb(III) removal and an adsorption-dominated mechanism for Sb(V) removal by Fe-Mn NPs. When the produced Fe-Mn NPs were applied to remove Sb from mine wastewater, 92.7% removal was attained, demonstrating the significant practical potential of these nanoparticles to Sb species from mine wastewaters. This study provides novel insights for future exploration for Sb removal from mine wastewaters.

Facile synthesis of Ce(III)-rich cerium oxyhydroxide and its unselective adsorption of Sb(III) and Sb(V) via oxygen vacancies

The introduction of oxygen vacancies (OVs) into metal oxide materials is an effective method for modifying the surface properties of environmentally functional materials. However, limited attention has been paid to their roles as pollutant adsorbent. In this study, Ce(III)-enriched cerium oxyhydroxide particles (CeO(OH)2-OVs@CS) were prepared using a drop-in phase separation method and then used as adsorbents to address the challenges of conventional metal oxides that display notably lower adsorption efficiencies for Sb(V) than Sb(III). Within 60 min, more than 96 % of both Sb(III) and Sb(V) with an initial concentration of 50 mg/L were removed, with only a 2 % difference between them. XRD, XPS, EPR, and FT-IR results demonstrated that chitosan served as a carrier for Ce nanoparticles and, due to its reductive characteristics, enhanced the air stability of Ce(III), thereby creating more OVs. Meanwhile, chitosan's abundant functional groups such as OH, NH2, and CO in its structure can also facilitate the binding of Sb species onto CeO(OH)2. Density functional theory (DFT) calculations also indicated that antimonate ions were more prone to binding with OVs compared with defect-free crystal surfaces. Additionally, CeO(OH)2-OVs@CS showed great removal performance for organic ligands in antimony(III) potassium tartrate solution, and about 97 % of tartaric acid was removed simultaneously.

On-site monitoring of dissolved Sb species in natural waters by an automatic system using flow injection coupled with hydride generation atomic fluorescence spectrometer

Antimony (Sb) is a toxic and potentially carcinogenic element in the environment. The toxicity of Sb(III) is ten times that of Sb(V). Therefore, on-site monitoring technique for dissolved Sb species is crucial for the study of Sb environmental processes. In this study, an automated, portable, and cost-effective system was developed for field simultaneous analysis of Sb(III) and Sb(III + V) in natural waters. The system comprised a portable atomic fluorescence spectrometer equipped with a built-in electrochemical H2 generator to reduce the consumption of acid/borohydride solution and make the atomizer more stable for on-site analysis. Flow injection technique was also used to achieve on-line pretreatment of water samples, including filtration, acidification, pre-reduction, and hydride generation procedures. Under the optimal conditions, the limits of detection (3σ, n = 11) of the developed method were 0.015 μg/L and the linear ranges were 0.05–5.0 μg/L for both Sb(III) and Sb(III + V). The relative standard deviations (n = 11) of the spiked samples of Sb(V) were 3.2% (0.05 μg/L), 3.3% (0.2 μg/L), and 1.7% (0.5 μg/L), respectively. The spiked recoveries of lake water, treated wastewater, and seawater ranged from 97.0% to 108.5%. The novel system of flow injection coupled with hydride generation atomic fluorescence spectrometer (FI-HG-AFS) was applied to carry out an 18-h fixed-point monitoring at a secondary settling tank of a wastewater treatment facility in Xiamen University, and a 6-h real-time underway analysis in the surface seawater of Dongshan Bay, China, proving that the system was capable of long-term monitoring in the field.

Mushroom residue derived magnetic hydrochar for antimony removal from wastewater: Mechanisms insights and practicality assessment

The magnetic mushroom residue hydrochar (MMRH) was synthesized using mushroom waste and K2FeO4, and then applied for antimony (Sb) removal from wastewater. The maximum adsorption capacity of Sb(III) and Sb(V) by MMRH reached 636.9 and 814.3 mg/g, respectively. According to characterizations, the existence of K+ in MMRH significantly increased the ion exchange of Sb species. Further, the Fenton-like reactions could generate additional •OH species to effectively oxidize Sb(III) into Sb(V), while other mechanisms including complexation, co-precipitation, and physical adsorption were also comprehensively investigated. The practicality of this MMRH was also assessed by recycling and column experiments. This study is expected to offer novel perspectives on mushroom residue reutilization and Sb-polluted wastewater purification for a greener environment.

The uptake, transportation, and chemical speciation of Sb(III) and Sb(V) by wetland plants Arundinoideae (Phragmites australis) and Potamogetonaceae (Potamogeton crispus)

Antimony (Sb) is increasingly released and poses a risk to the environment and human health. Antimonite (Sb(III)) oxidation can decrease Sb toxicity, but the current knowledge regarding the effects of Sb(III) and antimonate (Sb(V)) exposure is limited to wetland plants, especially the Sb speciation in plants. In this study, Phragmites australis and Potamogeton crispus were exposed to 10 and 30 mg/L Sb(III) or Sb(V) for 20 days. The total concentration, subcellular distribution, and concentration in the iron plaque of Sb were determined. The Sb speciation in plants was analyzed by HPLC-ICP-MS. It illustrated that Sb(III) exposure led to more Sb accumulation in plants than Sb(V) treatments, with the highest Sb concentration of 405.35 and 3218 mg/kg in Phragmites australis and Potamogeton crispus, respectively. In the subcellular distribution of Sb, accumulation of Sb mainly occurred in cell walls and cell cytosol. In Phragmites australis, the transport factor in the Sb(V) treatments was about 3 times higher than the Sb(III) treatments, however, it was lower in the Sb(V) treatments than Sb(III) treatments for Potamogeton crispus. Sb(V) was detected in the plants of Sb(III) treatments with different Sb(V)-total Sb vitro (Phragmites australis: 34 % and, Potamogeton crispus: 15 %), moreover, Sb(V) was also detected in the nutrient solution of Sb(III) treatments. Antimony exposure caused a reduction of the iron plaque formation, at the same time, the root aerenchyma formation was disrupted, and this phenomenon is more pronounced in the Sb(III) treatments. Moreover, the iron plaque has a higher sorption potential to Sb under Sb(III) exposure than that under Sb(V) exposure. The results can fill the gap for antinomy speciation in wetland plants and expand the current knowledge regarding the Sb translocation in wetland systems.