One-step functionalization of chitosan with rich sulfur and nitrogen adsorption sites for efficient recovery of silver ions from actual wastewater.

The recovery of silver ions from wastewater is of great importance due to their adverse environmental impact and significant economic value. This paper introduces a novel adsorbent (CS-AHMT) that can be easily synthesized via a one-step functionalization of chitosan with 4-Amino-3-hydrazino-1,2,4-triazol-5-thiol to efficiently recover silver ions from actual wastewater. CS-AHMT demonstrated superior adsorption performance, achieving an adsorption capacity of 241.4 mg·g-1 at pH 5 and 318 K, and the adsorption equilibrium was rapidly attained within 60 to 120 min. Kinetic and isotherm studies indicate that the adsorption process conforms to the pseudo-nth-order (PNO) and Sips models, suggesting a monolayer adsorption that incorporates both physical and chemical processes, with internal mass transfer being the primary rate-limiting step. Electrostatic and coordination interactions are primarily involved in the adsorption mechanism of silver ions on CS-AHMT, as further validated by density functional theory (DFT) calculations. The selectivity and practical applicability of CS-AHMT were confirmed in real wastewater containing high concentrations of competing ions. The findings underscore the potential of CS-AHMT as an effective adsorbent for silver ion recovery in wastewater treatment applications.

The design of high-efficient MOFs for selective Ag(I) capture: DFT calculations and practical applications.

Recovering silver from wastewater not only significantly reduces environmental harm but also meets the growing demand for silver in modern industry. Here, a novel metal-organic framework adsorbent (MOF-RD) using rhodanine derivatives as linkers is introduced for the efficient and selective capture of silver ions in real wastewater. The adsorption of MOF-RD followed pseudo-second-order and Sips models, and thermodynamic investigations revealed the process to be endothermic. MOF-RD demonstrated a remarkable adsorption capacity of 707.2 mg·g-1 for Ag(I) at pH 5 and 318 K. The interaction between silver ions and MOF-RD was mainly electrostatic attraction and coordination, with coordination primarily occurring at the CO and CS sites within the rhodanine motif. The practical applicability of MOF-RD for selective adsorption of Ag(I) was validated in actual wastewater with high-concentration competing metal ions. Furthermore, after 10 adsorption-desorption cycle experiments, MOF-RD still retained a strong regenerative capability. The results reveal the good potential of MOF-RD as an adsorbent for selectively recovering Ag(I) from industrial wastewater. Additionally, the strategies and methods adopted in this article also provide new perspectives and technical paths for the separation and recovery of other metal ions in wastewater.

Synthesis of metal-organic frameworks with multiple nitrogen groups for selective capturing Ag(I) from wastewater.

As a noble metal with extremely high economic benefits, the recovery of silver ions has attracted a particular deal of attention. However, it is a challenge to recover silver ions efficiently and selectively from aqueous solutions. In this research, the novel metal-organic frameworks (MOFs) adsorbent (Zr-DPHT) is prepared for the highly efficient and selective recovery of silver ions from wastewater. Experimental findings reveal that Zr-DPHT's adsorption of Ag(I) constitutes an endothermic process, with an optimal pH of 5 and exhibits a maximum adsorption capacity of 268.3 mg·g-1. Isotherm studies show that the adsorption of Ag(I) by Zr-DPHT is mainly monolayer chemical adsorption. Kinetic studies indicate that the internal diffusion of Ag(I) in Zr-DPHT may be the rate-limiting step. The mechanism for Ag(I) adsorption on Zr-DPHT involves electrostatic interactions and chelation. In competitive adsorption, Ag(I) has the largest partition coefficient (9.64 mL·mg-1), indicating a strong interaction between Zr-DPHT and Ag(I). It is proven in the adsorption-desorption cycle experiments that Zr-DPHT has good regeneration performance. The research results indicate that Zr-DPHT can serve as a potential adsorbent for efficiently and selectively capturing Ag(I), providing a new direction for MOFs in the recycling field of precious metals.

A novel magnetic Ti-MOF/chitosan composite for efficient adsorption of Pb(II) from aqueous solutions: Synthesis and investigation.

In this investigation, a composite material comprising Ti-MOF and chitosan, denoted as BD-MOF(Ti)@CS/Fe3O4, was successfully designed for the efficient adsorption of Pb(II) from aqueous solutions. A comprehensive array of characterization techniques, including SEM, XRD, BET, FT-IR, and XPS, were meticulously employed to scrutinize the structural attributes and morphological features of the Pb(II) adsorbent. Notably, the material exhibits adaptability to a broad pH range, with adsorption efficiency reaching 99 % between pH 3 and 6. Kinetic studies reveal that the adsorption process of Pb(II) by BD-MOF(Ti)@CS/Fe3O4 adheres closely to a pseudo-second-order kinetic model. Impressively, within a short duration of 40 min, the adsorption efficiency can reach 85 %. Furthermore, the adsorption isotherm aligns with the Hill isotherm model, signifying cooperative adsorption. This observation underscores the synergistic interplay among the functional groups on the surface of BD-MOF(Ti)@CS/Fe3O4 in capturing Pb(II). As per the Hill model, the theoretical maximum capacity was an impressive 944.9 mg/g. Thermodynamic assessments suggested that the adsorption process was spontaneous, entropy increasing and exothermic. Even in the presence of various interfering ions, BD-MOF(Ti)@CS/Fe3O4 exhibited robust adsorption performance, thereby affirming its utility in complex environments. Moreover, the material demonstrates noteworthy reusability, sustaining effective Pb(II) removal across five consecutive cycles in aqueous solutions.

Selective adsorption of mercury ion from water by a novel functionalized magnetic Ti based metal-organic framework composite.

In the context of industrialization and severe wastewater pollution, mercury ions pose a major threat due to their high toxicity. However, traditional adsorbents and common metal-organic framework (MOF) materials have limited effectiveness. This study focuses on combining magnetic materials with functionalized titanium-based MOF composite (SNN-MIL-125(Ti)@Fe3O4) to improve mercury ion adsorption. Through comprehensive characterization and analysis, the adsorption performance and mechanism of the material were studied. The optimal adsorption of the material was achieved at pH 5, exhibiting a pseudo-second-order adsorption model and the Hill theoretical capacity of 668.98 mg/g. Hill and Tempkin models confirmed the presence of chemical and physical adsorption sites on the material surface. Thermodynamic experiments showed a spontaneous endothermic process. Despite the presence of interfering ions, the material exhibited high selectivity for mercury ions. After four cycles, adsorption performance decreased by only 8%, indicating excellent reusability. Nitrogen- and sulfur-containing functional groups played a key role in mercury ion adsorption. In conclusion, SNN-MIL-125(Ti)@Fe3O4, as a magnetic MOF adsorption material, showed potential for effective remediation of mercury-contaminated wastewater. This study contributes to the development of efficient adsorption materials and enhances the understanding of their mechanism.

The one-step synthesis of a novel metal-organic frameworks for efficient and selective removal of Cr(VI) and Pb(II) from wastewater: Kinetics, thermodynamics and adsorption mechanisms.

The removal of Cr(VI) and Pb(II) from wastewater is one of the methods to ensure water safety. However, it is still a difficult point to design efficient and selective adsorbent. In this work, Cr(VI) and Pb(II) were removed from water by a new metal-organic frameworks material (MOF-DFSA) with numerous adsorption sites. The max adsorption capacities of MOF-DFSA were 188.12 mg/g for Cr(VI) after 120 min and 349.09 mg/g for Pb(II) within 30 min. MOF-DFSA showed good selectivity and reusability after four cycles. The adsorption of MOF-DFSA was an irreversible process with multi-site coordination, and an active site adsorbed 1.798 Cr (VI) and 0.395 Pb (II). Kinetic fitting showed that the adsorption was chemisorption and surface diffusion was the main limiting step. Thermodynamic showed that Cr(VI) adsorption was enhanced at higher temperatures by spontaneous processes while Pb(II) was weakened. The chelation and electrostatic interaction of the hydroxyl and nitrogen-containing groups of MOF-DFSA with Cr(VI) and Pb(II) is the predominant mechanism, while the reduction of Cr(VI) also play an important role in adsorption. In conclusion, MOF-DFSA was a sorbent that can be used for the removal of Cr(VI) and Pb(II).

Design of Zr-MOFs by Introducing Multiple Ligands for Efficient and Selective Capturing of Pb(II) from Aqueous Solutions.

The existence of lead ions seriously affects the quality of many metal products in metallurgical enterprises. Currently, the various methods of lead-ion removal tried by researchers will affect valuable metals in the removal process, thus resulting in low economic efficiency. In this study, a novel metal-organic framework adsorbent (UiO-FHD) which efficiently and selectively captures lead ions is developed by introducing multiple ligands. The maximum adsorption capacity of lead ions is 433.15 mg/g at pH 5. The adsorption process accords with the pseudo-second-order kinetic and the Langmuir isotherm models at room temperature. Thermodynamic experiments indicate that the removal of Pb(II) is facilitated by appropriate temperature reduction. The performance tests indicate that UiO-FHD maintains a high removal rate of 90.35% for Pb(II) after four consecutive adsorption-desorption cycles. The distribution coefficient of lead ions (26.7 L/g) shows that UiO-FHD has excellent selective adsorption for lead ions. It is revealed that the chelation of the sulfhydryl groups and the electrostatic interaction of the hydroxyl groups are the dominant factors to improve the removal rate of Pb(II) by density functional theory calculations. This study clarifies the value of self-designed novel organic ligands in metal-organic framework materials that selectively capture heavy-metal ions.

Core-shell Ni1.5Sn@Ni(OH)2 nanoflowers as battery-type supercapacitor electrodes with high rate and capacitance.

Poor conductivity and aggregation of two-dimensional Ni(OH)2 nanosheets hinder their extensive applications in supercapacitors. In the current study, a core-shell nanoflower composite is successfully synthesized using a high conductivity Ni1.5Sn alloy and Ni(OH)2 nanosheets via a facile two-step hydrothermal reaction. The alloy material enhances the conductivity of the sample and promotes electron transport for Ni(OH)2. The as-prepared core-shell structure effectively restrains the clustering of nanosheets and improves the specific surface area of active materials. The optimized NS@NL-3 displays an outstanding specific capacitance (1002.2C g-1 at 1 A g-1) and satisfactory capacitance retention rate (80.63% at 20 A g-1) by adjusting the coating amount of Ni(OH)2 nanosheets, which is significantly higher compared with the performance of pure Ni(OH)2 (609.6C g-1 at 1 A g-1 and 55.64% at 20 A g-1). The all-solid-state hybrid supercapacitor (HSC) is fabricated with activated carbon (AC) as the negative electrode and NS@NL-3 as the positive electrode, which shows a high energy density of 57.4 Wh kg-1 at 803.6 W kg-1 as well as a superior cycling stability (88.45 % after 10,000 cycles). Experiment shows that 42 LEDs are effortlessly lit by two series-wound solid-state HSC devices, which indicates its high potential for practical applications.

WS2 nanosheets@ZIF-67-derived N-doped carbon composite as sodium ion battery anode with superior rate capability.

Devising novel composite electrodes with particular structural/electrochemical characteristics becomes an efficient strategy to advance the performance of rechargeable battery. Herein, considering the homogeneous transition metal sulfide with N-doped carbon derived from zeolitic imidazolate framework-67 (ZIF-67) and WS2 with large interlayer spacing, a laurel-leaf-like Co9S8/WS2@N-doped carbon bimetallic sulfide (Co9S8/WS2@NC) is engineered and prepared via a step-by-step method. As an electrode material for sodium ion batteries (SIBs), Co9S8/WS2@NC composite delivers high capacities of 480 and 405 mA h g-1 at 0.1 and 1.0 A g-1, respectively. As the current density increases from 0.1 to 5.0 A g-1, it provides specific capacity of 359 mA h g-1 with a capacity retention rate of 78.0%, which is higher than that of Co9S8@NC (63.5%) and WS2 (58.6%). The Co9S8/WS2@NC composite anode maintains a stable specific capacity (354 mA h g-1 at 2.0 A g-1). It also exhibits a high capacitive contribution ratio of 90.8% at 1.0 mV s-1. This study provides a new and reliable insight for designing bimetallic sulfide with two-dimensional nanostructure for energy storage.

Hierarchical Carbon Nanowire/Ni@MnO2 Nanocomposites for High-Performance Asymmetric Supercapacitors.

A 3D hierarchical carbon cloth/nitrogen-doped carbon nanowires/Ni@MnO2 (CC/N-CNWs/Ni@MnO2 ) nanocomposite electrode was rationally designed and prepared by electrodeposition. The N-CNWs derived from polypyrrole (PPy) nanowires on the carbon cloth have an open framework structure, which greatly increases the contact area between the electrode and electrolyte and provides short diffusion paths. The incorporation of the Ni layer between the N-CNWs and MnO2 is beneficial for significantly enhancing the electrical conductivity and boosting fast charge transfer as well as improving the charge-collection capacity. Thus, the as-prepared 3D hierarchical CC/N-CNWs/Ni@MnO2 electrode exhibits a higher specific capacitance of 571.4 F g-1 compared with those of CC/N-CNWs@MnO2 (311 F g-1 ), CC/Ni@MnO2 (196.6 F g-1 ), and CC@MnO2 (186.1 F g-1 ) at 1 A g-1 and remarkable rate capability (367.5 F g-1 at 10 A g-1 ). Moreover, asymmetric supercapacitors constructed with CC/N-CNWs/Ni@MnO2 as cathode material and activated carbon as anode material deliver an impressive energy density of 36.4 W h kg-1 at a power density of 900 W kg-1 and a good cycling life (72.8 % capacitance retention after 3500 cycles). This study paves a low-cost and simple way to design a hierarchical nanocomposite electrode with large surface area and superior electrical conductivity, which has wide application prospects in high-performance supercapacitors.

Selective removal behavior and mechanism of trace Hg(II) using modified corn husk leaves.

Removal of Hg(II) from wastewater was beneficial to satisfy the discharge standards of China's mercury-containing wastewater (50 ppb). An adsorbent was prepared via modifying corn husk leaves with bismuthiol I. The results revealed that the mercury removal rate was more than 98.5% at pH 1.0-7.0. Moreover, the removal rate reached 96% at 5 min and the residual concentration decreased from 10 ppm to approximately 30 ppb. In addition, the adsorbent owned a conspicuous selective absorbability for trace Hg(II) from wastewater. The adsorption process followed a Hill isotherm model. The actual saturated adsorption quantity of the adsorbent was 707 mg/g. The repeatability experiment indicated that the mercury removal efficiency was still beyond 99% after three cycles. The X-ray photoelectron spectroscopy suggested that the main adsorption mechanism was chelation between nitrogen/sulfur groups and Hg(II). The adsorbent was hopeful to remove mercury from wastewater in a sustainability perspective.

Post-functionalization of UiO-66-NH2 by 2,5-Dimercapto-1,3,4-thiadiazole for the high efficient removal of Hg(II) in water.

A new MOFs adsorbent was prepared by post-functionalization of UiO-66-NH2 with 2,5-Dimercapto-1,3,4-thiadiazole and utilized to remove the Hg(II) in water selectively. The UiO-66-types were detected by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), Brunauer-Emmett-Teller (BET) and zeta potential instruments. The adsorption properties of the new MOFs adsorbent were investigated by batch experiments. The actual maximum adsorption amount was 670.5 mg/g at the optimal pH of 3. Adsorption kinetic and isotherm models were exceedingly fitted to pseudo-second-order and Langmuir/Dubinin-Radushkevich, respectively. The adsorption process and mode were geared to monolayer and chemisorption, the removal rate was directly proportional to the square of mercury ions concentration. The UiO-66-DMTD adsorbent was easy to be regenerated and the removal rate decreased by only 13.5% after ten consecutive cycles. The results of FTIR, XRD and XPS suggested that the adsorption mechanism lay on the complexation reaction between Hg(II) and thiol/nitrogen-containing groups. Moreover, compared with other competitive metal ions, viz., Zn(II), Co(IV), Ni(II), Cd(II), Mg(II), Fe(III), Ca(II) and Cu(II), the UiO-66-DMTD demonstrated an outstanding selective adsorption for Hg(II). These results manifested that the UiO-66-DMTD was a latent adsorbent for the efficient and selective removal of Hg(II) in wastewater.

Enhanced and selective adsorption of Hg2+ to a trace level using trithiocyanuric acid-functionalized corn bract.

A novel trithiocyanuric acid-modified corn bract (TCA-CCB) was prepared, and its removal properties for Hg2+ were investigated. TCA-CCB showed a remarkable absorbability for Hg2+ in mixed ion solutions. Adsorption kinetics experiments indicated that the removal of Hg2+ on TCA-CCB was quick, with a removal rate of 99.07% within 5 min. In addition, the removal rate of Hg2+ exceeded 98% over all pH conditions. The adsorption process can be best described by pseudo-second-order kinetic and Hill isotherm models. The saturated adsorption capacity of TCA-CCB for Hg2+ was 390 mg/g. The TCA-CCB could efficiently adsorb Hg2+ from the simulated wastewater and reduce the Hg2+ concentration from 10 ppm to 12.35 ppb, which was lower than the greatest allowable value of 50 ppb and satisfied the emission standards required by the Chinese government. Moreover, the removal rate of Hg2+ was beyond 99% after three cycles. The results of the zeta potential and X-ray photoelectron spectroscopy (XPS) implied that the chelation and ion exchange between amino/thiol groups and Hg2+ played a significant role in the improvement of the adsorption properties. The corn bract modified by trithiocyanuric acid exhibits apparent advantages in the removal of Hg2+ from ppm to ppb due to its high selectivity, adsorption capacity and stability.

Synthesis and Evaluation of 8-Aminoquinoline-Grafted Poly(glycidyl methacrylate) for the Recovery of Pd(II) from Highly Acidic Aqueous Solutions.

A new adsorbent was prepared via modified poly(glycidyl methacrylate) with 8-aminoquinoline (AQ-PGMA) for the recovery of Pd(II) from solution. The practical application values of AQ-PGMA, including efficiency, selectivity and reusability for the recovery of Pd(II), are proved by the various experiment parameters. The parameters include HCl concentration, adsorption time, initial Pd(II) concentration, coexisting ions and reused cycles. The prepared AQ-PGMA showed a high adsorbing capacity for Pd(II) (up to 267.90 mg/g) when the concentration of HCl is higher than 0.4 mol/L. The analysis of the adsorption process indicated that the adsorption kinetics followed a pseudo-second-order kinetic model and the adsorption isotherms obeyed the Hill model. The Hill model showed that one adsorption site on the AQ-PGMA could combine 1.45 Pd(II). In addition, the obtained adsorbent demonstrated good regenerative ability and satisfying selectivity for the recovery of Pd(II). The adsorption mechanism was dominated by the chelation and ion exchange reactions between amines/hydroxyl groups and Pd(II). The experiments confirmed that AQ-PGMA was efficient for recovery of Pd(II) from highly acidic aqueous solutions.

Synergistic extraction of gold from the refractory gold ore via ultrasound and chlorination-oxidation.

A synergistic extraction method for gold from the refractory gold ores via ultrasound and chlorination-oxidation was developed. The effects of solid-liquid ratio, extraction time, ultrasound power, NaClO concentration and NaOH concentration on the extraction rate of gold from the refractory gold ore were investigated. The optimum conditions were as follows: NaClO concentration of 1.5mol/L, NaOH concentration of 1.5mol/L, solid-liquid ratio of 5, ultrasound power of 200W and ultrasound time of 2h. Under the optimal conditions, 68.55% of gold was extracted. However, only 45.8% of gold was extracted after 6h without the ultrasound-assisted extraction. XRD and SEM were used to analyze the influence of ultrasound on the mineral properties and strengthening mechanism. The results showed that the interface layer was peeled, new surface was exposed, reaction resistance was reduced, the liquid-solid reaction was promoted and reaction speed was greatly improved under ultrasound. According to the results of range and variance analysis, the optimum leaching experiment with orthogonal design was almost identical with the optimum experiment of single factor. Among them, the ultrasound power was the most significant factors affecting leaching rate of gold. Compared with other extraction method, the synergistic extraction process decomposed completely sulfide and improved significantly the extraction rate of gold.

Selective Adsorption of Ag⁺ on a New Cyanuric-Thiosemicarbazide Chelating Resin with High Capacity from Acid Solutions.

A new cyanuric-thiosemicarbazid (TSC-CC) chelating resin was synthesized and employed to selectively adsorb Ag⁺ from acid solutions. The effects of acid concentration, initial concentration of Ag⁺, contact time and coexisting ions were investigated. The optimal acid concentration was 0.5 mol/L. The adsorption capacity of Ag⁺ reached 872.63 mg/g at acid concentration of 0.5 mol/L. The adsorption isotherm was fitted well with the Langmuir isotherm model and the kinetic data preferably followed the pseudo-second order model. The chelating resin showed a good selectivity for the Ag⁺ adsorption from acid solutions. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy/energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) were used to study the adsorption mechanism. The chelating and ionic interaction was mainly adsorption mechanism. The adsorbent presents a great potential in selective recovery Ag⁺ from acid solutions due to the advantage of high adsorption capacity and adapting strongly acidic condition. The recyclability indicated that the (TSC-CC) resin had a good stability and can be recycled as a promising agent for removal of Ag⁺.