Reclaimable MoS2 Sponge Absorbent for Drinking Water Purification Driven by Solar Energy

The static and dynamic adsorptive performance of a nitrogen and sulfur functionalized 3D chitosan sponge for mercury and its machine learning evaluation

The use of chitosan-based sponge materials for Hg(II) removal has gained attention recently due to their effectiveness. However, the complex preparation, limited performance, and poor acid resistance remained major drawbacks. Herein, a nitrogen‑sulfur functionalized macroporous chitosan sponge was successfully synthesized via two mild amidation reactions and exhibited abundant interconnected mesopores. These features endowed the functionalized chitosan-based sponge with high adsorption capacity (1227.15 mg g-1), fast reaction rate (8.27 × 10-3 g mg-1·min-1), broad pH adaptability (1-7), and high selectivity, even in the artificial chlor-alkali wastewater. Furthermore, the impressive saturation capacity of 1329.24 mg g-1 was achieved in various heights and injection rates in the fixed-bed column test, and the good removal efficiency (>85 %) was maintained after six dynamic regeneration cycles. The excellent performance was primarily attributed to the chemisorption of CS groups. Among the three machine learning models, the ANFIS algorithm owned the best results of the smallest RMSE (0.00315) and highest R2 (0.9752) for predicting dynamic adsorptive behaviors. Overall, this research provided a reference for preparing a promising mesoporous sponge as an alternative recyclable and efficient candidate for industrial wastewater treatment and offered a machine learning model to predict the dynamic adsorptive performance.

High efficiency Hg(II) electrochemical detection based on the number of defect engineering on MoS2: Insight in synergistic action of sulfur vacancies and undercoordinated Mo

Defects on nanomaterials can effectively enhance the performance of electrochemical detection, but an excessive number of defects may have an adverse effect. In this study, MoS2 nanosheets were synthesized using a hydrothermal synthesis method. By controlling the calcination temperature, MoS2-7H, calcined at 700 °C under H2/Ar2, exhibited an optimal ratio of "point" defects to "plane" defects, resulting in excellent detection performance for mercury ions (Hg(II)). In general, the sulfur vacancies (SV) and undercoordinated Mo generated after calcination of MoS2 significantly promotes the adsorption process and redox of Hg(II) by increasing surface chemical activity, providing additional adsorption sites and adjusting surface charge status to accelerate the catalytic redox of Hg(II). The prepared MoS2-7H-modified electrode showed a sensitivity of 18.25 μA μM-1 and a low limit of detection (LOD) of 6.60 nM towards Hg(II). MoS2-7H also demonstrated a good anti-interference, stability, and exhibited a strong current response in real water samples. The modulation to obtain appropriate number of defects in MoS2 holds promise as a prospective electrode modification material for the electroanalysis.

Crystalline Phase Regulates Microbial Methylation Potential of Mercury Bound to MoS2 Nanosheets: Implications for Safe Design of Mercury Removal Materials

Transition-metal dichalcogenides (TMDs) have shown great promise as selective and high-capacity sorbents for Hg(II) removal from water. Yet, their design should consider safe disposal of spent materials, particularly the subsequent formation of methylmercury (MeHg), a highly potent and bioaccumulative neurotoxin. Here, we show that microbial methylation of mercury bound to MoS2 nanosheets (a representative TMD material) is significant under anoxic conditions commonly encountered in landfills. Notably, the methylation potential is highly dependent on the phase compositions of MoS2. MeHg production was higher for 1T MoS2, as mercury bound to this phase primarily exists as surface complexes that are available for ligand exchange. In comparison, mercury on 2H MoS2 occurs largely in the form of precipitates, particularly monovalent mercury minerals (e.g., Hg2MoO4 and Hg2SO4) that are minimally bioavailable. Thus, even though 1T MoS2 is more effective in Hg(II) removal from aqueous solution due to its higher adsorption affinity and reductive ability, it poses a higher risk of MeHg formation after landfill disposal. These findings highlight the critical role of nanoscale surfaces in enriching heavy metals and subsequently regulating their bioavailability and risks and shed light on the safe design of heavy metal sorbent materials through surface structural modulation.

Mechanisms for synergistically enhancing cadmium remediation performance of biochar: Silicon activation and functional group effects

This work proposes an advanced biochar material (β-CD@SiBC) for controllable transformation of specific silicon (Si) forms through endogenous Si activation and functional group introduction for efficient cadmium (Cd) immobilization and removal. The maximum adsorption capacity of β-CD@SiBC for Cd(II) reached 137.6 mg g-1 with a remarkable removal efficiency of 99 % for 200 mg L-1Cd(II). Moreover, the developed β-CD@SiBC flow column exhibited excellent performance at the environmental Cd concentration, with the final concentration meeting the environmental standard for surface water quality (0.05 mg L-1). The remediation mechanism of β-CD@SiBC could be mainly attributed to mineral precipitation and ion exchange, which accounted for 42 % and 29 % of the remediation effect, respectively, while functional group introduction enhanced its binding stability with Cd. Overall, this work proposes the role and principle of transformation of Si forms within biochar, providing new strategies for better utilizing endogenous components in biomass.

Revealing the interaction forms between Hg(II) and group types (-Cl, -CN, -NH2, -OH, -COOH) in functionalized Poly(pyrrole methane)s for efficient mercury removal

To explore the impact of different functional groups on Hg(II) adsorption, a range of poly(pyrrole methane)s functionalized by -Cl, -CN, -NH2, -OH and -COOH were synthesized and applied to reveal the interaction between different functional groups and mercury ions in water, and the adsorption mechanism was revealed through combined FT-IR, XPS, and DFT calculations. The adsorption performance can be improved to varying degrees by the incorporation of functional groups. Among them, the oxygen-containing functional groups (-OH and -COOH) exhibit stronger affinity for Hg(II) and can increase the adsorption capacity from 180 mg g-1 to more than 1400 mg g-1 at 318 K, with distribution coefficient (Kd) exceeding 105 mL g-1. The variations in the capture and immobilization capabilities of functionalized poly(pyrrole methane)s predominantly stem from the unique interactions between their functional groups and mercury ions. In particular, oxygen-containing -OH and -COOH effectively capture Hg(OH)2 through hydrogen bonding, and further deprotonate to form the -O-Hg-OH and -COO-Hg-OH complexes which are more stable than those obtained from other functionalized groups. Finally, the ecological safety has been fully demonstrated through bactericidal and bacteriostatic experiments to prove the functionalized poly(pyrrole methane)s can be as an environmentally friendly adsorbent for purifying contaminated water.

An all-in-one FeOx-rGO sponge fabricated by solid-phase microwave thermal shock for water evaporation and purification

Developing high-efficiency photothermal seawater desalination devices is of significant importance in addressing the shortage of freshwater. Despite much effort made into photothermal materials, there is an urgent need to design a rapidly synthesized photothermal evaporator for the comprehensive purification of complex seawater. Therefore, we report on all-in-one FeOx-rGO photothermal sponges synthesized via solid-phase microwave thermal shock. The narrow band gap of the semiconductor material Fe3O4 greatly reduces the recombination of electron-hole pairs, enhancing non-radiative relaxation light absorption. The abundant π orbitals in rGO promote electron excitation and thermal vibration between the lattices. Control of the surface hydrophilicity and hydrophobicity promotes salt resistance while simultaneously achieving the purification of various complex polluted waters. The optimized GFM-3 sponge exhibitedan enhanced photothermal conversion rate of 97.3% and a water evaporation rate of 2.04 kg/(m2·hr), showing promising synergistic water purification properties. These findings provide a highly efficient photothermal sponge for practical applicationsof seawater desalination and purification,as well as develop a super-rapid processing methodology for evaporation devices.

Recent progress in surface engineering methods and advanced applications of flexible polymeric foams

Polymeric foams, also known as three-dimensional (3D) polymeric sponges, are lightweight, flexible, compressible, and possess a high surface area compared with other bulk polymers. These sponges have traditionally been used for mattresses or seat cushions in homes, offices, aircraft, automobiles, and trains, and to insulate against heat, electricity, and noise. Recently, the demand for modern materials has expanded the application of polymeric foams to various high-value technologies, including in areas that need high flame retardancy, flame sensors, oil/water separation, metal adsorption, solar steam generation, piezoresistivity, electromagnetic interference shielding, thermal energy storage, catalysis, supercapacitors, batteries, and triboelectric energy harvesting. Proper modification of foams is a prerequisite for their use in high-value applications. Several new strategies for the surface coating of 3D porous foams and novel emerging applications have been recently developed. Therefore, in this review, current advances in the field of surface coating and the application of 3D polymeric foams are discussed. A brief background on 3D polymeric foams, including the unique properties and benefits of polymeric sponges and their routes of synthesis, is presented. Different coating strategies for polymeric sponges are discussed, and their advantages and drawbacks are highlighted. Different advanced applications of polymeric sponges, in conjunction with specific and detailed examples of the above-mentioned applications, are also described. Finally, challenges and potential applications related to the coating of polymeric foams are discussed. We envisage that this review will be useful to facilitate further research, promote continued efforts on the advanced applications mentioned above, and provide new stimuli for the design of novel polymeric sponges for future modern applications.

Ultrafast absorption mechanism of oil-emulsified micelles onto ferrous absorbents with dielectrophoresis force in the presence of polarization

Absorption and desorption rates were generally dependent on the concentration gradient from bulk to absorbents. A novel methodology based on a capacitor with an alternating electric field (AEF) is developed to accelerate the absorption and desorption rates with the frequency manipulation. Ferrous polystyrene microspheres (PISMs) are synthesized as absorbents, which could enhance the complex permittivities as well as dielectric properties. Theoretically, the attractive force and viscous force predominately determine the particle and micelles movement in the medium under an AEF. Oil-emulsified micelles (OEM) with various viscosities were selected as absorbates. Both the OEM and microspherical absorbents assembled through the external attractive force in the presence of the AEF. When the attractive force is equal to viscous force in the medium at the characteristic frequency, the optimal absorption rate could be obtained. The absorption rate constants of pseudo-first-order for OEMs under the polarization at 50 V and 120 kHz of frequency are ca. 10 times higher than that in absence of the polarization. The desorption rate as well as recycling efficiency could be also improved at 800 kHz. The ferrous PISMs with high complex permittivity prevented the damage from the AEF, which could be recycled 10 times of absorption and desorption with frequency manipulation under the AEF. Our methodology provides novel insights for ultrafast wastewater treatment.

Efficient and selective removal of Hg(II) from water using recyclable hierarchical MoS2/Fe3O4 nanocomposites

Developing practical and cost-effective adsorbents with satisfactory mercury (Hg) remediation capability is indispensable for aquatic environment safety and public health. Herein, a recyclable hierarchical MoS₂/Fe₃O₄ nanocomposite (by in-situ growth of MoS₂ nanosheets on the surface of Fe₃O₄ nanospheres) is presented for the selective removal of Hg(II) from aquatic samples. It exhibited high adsorption capacity (∼1923.5 mg g ^-1), fast kinetics (k₂ ∼ 0.56 mg g ^-1 min^-1), broad working pH range (2-11), excellent selectivity (K_d > 1.0 × 10⁷ mL g ^-1), and great reusability (removal efficiency > 90% after 20 cycles). In particular, removal efficiencies of up to ∼97% for different Hg(II) concentrations (10-1000 μg L ^-1) in natural water and industrial effluents confirmed the practicability of MoS₂/Fe₃O₄. The possible mechanism for effective Hg(II) removal was discussed by a series of characterization analyses, which was attributed to the alteration of the MoS₂ structure and the surface coordination of Hg-S. The accessibility of surface sulfur sites and the diffusion of Hg(II) in the solid-liquid system were enhanced due to the advantage of the expanded interlayer spacing (0.96 nm) and the hierarchical structure. This study suggests that MoS₂/Fe₃O₄ is a promising material for Hg(II) removal in actual scenarios and provides a feasible approach by rationally constructing hierarchical structures to promote the practical applications of MoS₂ in sustainable water treatments.

Microwave-Assisted Synthesis of MoS2/BiVO4 Heterojunction for Photocatalytic Degradation of Tetracycline Hydrochloride

Compared with traditional hydrothermal synthesis, microwave-assisted synthesis has the advantages of being faster and more energy efficient. In this work, the MoS₂/BiVO₄ heterojunction photocatalyst was synthesized by the microwave-assisted hydrothermal method within 30 min. The morphology, structure and chemical composition were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM). The results of characterizations demonstrated that the synthesized MoS₂/BiVO₄ heterojunction was a spherical structure with dimensions in the nanorange. In addition, the photocatalytic activity of the samples was investigated by degrading tetracycline hydrochloride (TC) under visible light irradiation. Results indicated that the MoS₂/BiVO₄ heterojunction significantly improved the photocatalytic performance compared with BiVO₄ and MoS₂, in which the degradation rate of TC (5 mg L^-1) by compound where the mass ratio of MoS₂/BiVO₄ was 5 wt% (MB5) was 93.7% in 90 min, which was 2.36 times of BiVO₄. The active species capture experiments indicated that •OH, •O₂^- and h⁺ active species play a major role in the degradation of TC. The degradation mechanism and pathway of the photocatalysts were proposed through the analysis of the band structure and element valence state. Therefore, microwave technology provided a quick and efficient way to prepare MoS₂/BiVO₄ heterojunction photocatalytic efficiently.