Molecules

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13 pages, 2535 KiB

Open AccessArticle

The Carboxyl Functionalized UiO-66-(COOH)₂ for Selective Adsorption of Sr²⁺

by Yuan Gao, Yinhai Pan, Zihan Zhou, Quanzhi Tian and Rongli Jiang

Molecules 2022, 27(4), 1208; https://doi.org/10.3390/molecules27041208 - 11 Feb 2022

Cited by 10 | Viewed by 3264

Efficient and selective removal of ⁹⁰Sr is an important process for the safe use of nuclear energy. Herein, we investigate and assess the Sr²⁺ adsorption properties of a metal-organic framework UiO-66-(COOH)₂ functionalized by non-bonded carboxylic groups. This MOF is an [...] Read more.

Efficient and selective removal of ⁹⁰Sr is an important process for the safe use of nuclear energy. Herein, we investigate and assess the Sr²⁺ adsorption properties of a metal-organic framework UiO-66-(COOH)₂ functionalized by non-bonded carboxylic groups. This MOF is an exciting class of free carboxylic functionalized MOFs that combine chemical stability with gas sorption, dye elimination, and conductivity. Specifically, we show that uniformly distributed carboxyl and water stability make it accessible for loading Sr²⁺ without structural changes. The FTIR spectroscopy, PXRD analysis, XPS, and SEM-EDS studies show excellent stability as well as the strong affinity between -COOH active site and Sr²⁺. This strong coordination interaction guarantees a high adsorption capacity of 114 mg g⁻¹ within 5 h (pH 5 and 298 K). Combined kinetic and thermodynamic studies show that the surface complexation is strong chemisorption and cost-effective spontaneous process (ΔG = −5.49 kJ mol⁻¹~−2.16 kJ mol⁻¹). The fact that UiO-66-(COOH)₂ not only possesses a high adsorption capacity, but also enables selectivity to Sr²⁺ in the presence of similar radius ions Na⁺ and K⁺, prefigures its great potential for the practical treatment of radioactive Sr²⁺ in polluted water. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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12 pages, 2619 KiB

Open AccessArticle

Speciation Characteristics and Ecological Risk Assessment of Heavy Metals in Municipal Sludge of Huainan, China

by Mu You, Yunhu Hu, Yule Yan and Jie Yao

Molecules 2021, 26(21), 6711; https://doi.org/10.3390/molecules26216711 - 5 Nov 2021

Cited by 13 | Viewed by 2087

Abstract

In order to fully understand the morphological characteristics and pollution status of heavy metals in the dewatered sludge of Huainan Municipal sewage treatment plant, the physical and chemical properties were analyzed, and the content and occurrence forms of heavy metals (As, Cu, Zn, [...] Read more.

In order to fully understand the morphological characteristics and pollution status of heavy metals in the dewatered sludge of Huainan Municipal sewage treatment plant, the physical and chemical properties were analyzed, and the content and occurrence forms of heavy metals (As, Cu, Zn, Pb, Cd, Cr, and Ni) in the sludge were studied using the geological accumulation method (Igeo), risk assessment coding method (RAC), and potential ecological risk index method to evaluate the ecological risk. The results showed that the municipal sludge in Huainan was rich in nutrients, with good prospects for agricultural utilization. There were differences in the morphological distributions of different heavy metals. The Igeo values for Ni, As, Cr, and Pb were below 0. The results of RAC indicated that the risk level of Cr in sludge was a low risk, and those of other heavy metals were moderate risks. The potential ecological risk of Cd had the highest potential ecological risk, and the other six metals were of low ecological risk. This conclusion can provide basic data and a theoretical reference for the comprehensive utilization of sludge in sewage treatment plants. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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14 pages, 2328 KiB

Open AccessArticle

Synthesis of Calcium Silicate Hydrate from Coal Gangue for Cr(VI) and Cu(II) Removal from Aqueous Solution

by Qing Zhang, Guijian Liu, Shuchuan Peng and Chuncai Zhou

Molecules 2021, 26(20), 6192; https://doi.org/10.3390/molecules26206192 - 14 Oct 2021

Cited by 8 | Viewed by 2159

Abstract

Both the accumulation of coal gangue and potentially toxic elements in aqueous solution have caused biological damage to the surrounding ecosystem of the Huainan coal mining field. In this study, coal gangue was used to synthesize calcium silicate hydrate (C-S-H) to remove Cr(VI) [...] Read more.

Both the accumulation of coal gangue and potentially toxic elements in aqueous solution have caused biological damage to the surrounding ecosystem of the Huainan coal mining field. In this study, coal gangue was used to synthesize calcium silicate hydrate (C-S-H) to remove Cr(VI) and Cu(II)from aqueous solutions and aqueous solution. The optimum parameters for C-S-H synthesis were 700 °C for 1 h and a Ca/Si molar ratio of 1.0. Quantitative sorption analysis was done at variable temperature, C-S-H dosages, solution pH, initial concentrations of metals, and reaction time. The solution pH was precisely controlled by a pH meter. The adsorption temperature was controlled by a thermostatic gas bath oscillator. The error of solution temperature was controlled at ± 0.3, compared with the adsorption temperature. For Cr(VI) and Cu(II), the optimum initial concentration, temperature, and reaction time were 200 mg/L, 40 °C and 90 min, pH 2 and 0.1 g C-S-H for Cr(VI), pH 6 and 0.07 g C-S-H for Cu(II), respectively. The maximum adsorption capacities of Cr(VI) and Cu(II) were 68.03 and 70.42 mg·g⁻¹, respectively. Furthermore, the concentrations of Cu(II) and Cr(VI) in aqueous solution could meet the surface water quality standards in China. The adsorption mechanism of Cu(II) and Cr(VI) onto C-S-H were reduction, electrostatic interaction, chelation interaction, and surface complexation. It was found that C-S-H is an environmentally friendly adsorbent for effective removal of metals from aqueous solution through different mechanisms. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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16 pages, 3456 KiB

Open AccessArticle

Synthesis of Porous Material from Coal Gasification Fine Slag Residual Carbon and Its Application in Removal of Methylene Blue

by Yixin Zhang, Rumeng Wang, Guofeng Qiu, Wenke Jia, Yang Guo, Fanhui Guo and Jianjun Wu

Molecules 2021, 26(20), 6116; https://doi.org/10.3390/molecules26206116 - 10 Oct 2021

Cited by 36 | Viewed by 2999

Abstract

A large amount of coal gasification slag is produced every year in China. However, most of the current disposal is into landfills, which causes serious harm to the environment. In this research, coal gasification fine slag residual carbon porous material (GFSA) was prepared [...] Read more.

A large amount of coal gasification slag is produced every year in China. However, most of the current disposal is into landfills, which causes serious harm to the environment. In this research, coal gasification fine slag residual carbon porous material (GFSA) was prepared using gasification fine slag foam flotation obtained carbon residue (GFSF) as raw material and an adsorbent to carry out an adsorption test on waste liquid containing methylene blue (MB). The effects of activation parameters (GFSF/KOH ratio mass ratio, activation temperature, and activation time) on the cation exchange capacity (CEC) of GFSA were investigated. The total specific surface area and pore volume of GSFA with the highest CEC were 574.02 m²/g and 0.467 cm³/g, respectively. The degree of pore formation had an important effect on CEC. The maximum adsorption capacity of GFSA on MB was 19.18 mg/g in the MB adsorption test. The effects of pH, adsorption time, amount of adsorbent, and initial MB concentration on adsorption efficiency were studied. Langmuir isotherm and quasi second-order kinetic model have a good fitting effect on the adsorption isotherm and kinetic model of MB. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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15 pages, 6373 KiB

Open AccessArticle

Preparation of Bamboo-Based Hierarchical Porous Carbon Modulated by FeCl₃ towards Efficient Copper Adsorption

by Yixin Zhang, Guofeng Qiu, Rumeng Wang, Yang Guo, Fanhui Guo and Jianjun Wu

Molecules 2021, 26(19), 6014; https://doi.org/10.3390/molecules26196014 - 3 Oct 2021

Cited by 9 | Viewed by 2583

Abstract

Using bamboo powder biochar as raw material, high-quality meso/microporous controlled hierarchical porous carbon was prepared—through the catalysis of Fe³⁺ ions loading, in addition to a chemical activation method—and then used to adsorb copper ions in an aqueous solution. The preparation process mainly [...] Read more.

Using bamboo powder biochar as raw material, high-quality meso/microporous controlled hierarchical porous carbon was prepared—through the catalysis of Fe³⁺ ions loading, in addition to a chemical activation method—and then used to adsorb copper ions in an aqueous solution. The preparation process mainly included two steps: load-alkali leaching and chemical activation. The porosity characteristics (specific surface area and mesopore ratio) were controlled by changing the K₂CO₃ impregnation ratio, activation temperature, and Fe³⁺ ions loading during the activation process. Additionally, three FBPC samples with different pore structures and characteristics were studied for copper adsorption. The results indicate that the adsorption performance of the bamboo powder biochar FBPC material was greatly affected by the meso/micropore ratio. FBPC _2.5-900-2%, impregnated at a K₂CO₃: biochar ratio of 2.5 and a Fe³⁺: biochar mass ratio of 2%, and activated at 900 °C for 2 h in N₂ atmosphere, has a very high specific surface area of 1996 m² g⁻¹ with a 58.1% mesoporous ratio. Moreover, it exhibits an excellent adsorption capacity of 256 mg g⁻¹ and rapid adsorption kinetics for copper ions. The experimental results show that it is feasible to control the hierarchical pore structure of bamboo biochar-derived carbons as a high-performance adsorbent to remove copper ions from water. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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11 pages, 3929 KiB

Open AccessArticle

Geochemical Anomaly Characteristics of Cd in Soils around Abandoned Lime Mines: Evidence from Multiple Technical Methods

by Lu Wei, Meichen Wang, Guijian Liu and Dun Wu

Molecules 2021, 26(17), 5127; https://doi.org/10.3390/molecules26175127 - 24 Aug 2021

Cited by 1 | Viewed by 1800

Abstract

Lime mines are a potential source of pollution, and the surrounding soil environment is generally at threat, especially in abandoned lime mines. This paper focuses on the study area in eastern Anhui, attempting to analyze whether Cd enrichment is related to abandoned mines. [...] Read more.

Lime mines are a potential source of pollution, and the surrounding soil environment is generally at threat, especially in abandoned lime mines. This paper focuses on the study area in eastern Anhui, attempting to analyze whether Cd enrichment is related to abandoned mines. On the basis of geological investigation, this study systematically used XRD, XRF, GTS and universal Kriging interpolation to determine the distribution law of Cd in the study area, and evaluated the potential ecological risk of Cd. The results showed that the main mineral types of soil samples of red clastic rock soil parent material (RdcPm) and soil samples of carbonate soil parent material (CPm) were not completely the same. Correlation analysis showed that CaO, MgO and Cd were positively correlated with the CPm. Human activities led to the accumulation of Cd in the study area. High Cd was mainly concentrated in the northwest of the study area, which was correlated with abandoned mines and soil parent materials. The study area was dominated by slight potential risks, although some areas had medium potential risks and high potential risks. All potential high risks were in the CPm field. This study provides a scientific basis for the comprehensive utilization and development planning of soil in the study area. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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15 pages, 57990 KiB

Open AccessArticle

Study on the Mechanical Properties of Fly-Ash-Based Light-Weighted Porous Geopolymer and Its Utilization in Roof-Adaptive End Filling Technology

by Luchang Xiong, Bowen Fan, Zhijun Wan, Zhaoyang Zhang, Yuan Zhang and Peng Shi

Molecules 2021, 26(15), 4450; https://doi.org/10.3390/molecules26154450 - 23 Jul 2021

Cited by 3 | Viewed by 1742

Abstract

This paper aims to study the porous structure and the mechanical properties of fly-ash-based light-weighted porous geopolymer (FBLPG), exploring the feasibility of using it in roof-adaptive end filling technology based on its in-situ foaming characteristics and plastic yielding performance. A porous structure model [...] Read more.

This paper aims to study the porous structure and the mechanical properties of fly-ash-based light-weighted porous geopolymer (FBLPG), exploring the feasibility of using it in roof-adaptive end filling technology based on its in-situ foaming characteristics and plastic yielding performance. A porous structure model of FBLPG during both the slurry and solid period was established to study their influence factor. In addition, this study also built a planar structure model in the shape of a honeycomb with bore walls, proving that the bore walls possess the characteristics of isotropic force. FBLPG shows a peculiar plastic yielding performance in the experiment where its stress stays stable with the gradual increase of the deformation, which can guarantee the stability of a filling body under the cycled load from the roof. At the same time, the in-situ foaming process combined with the unique filling technique can make the FBLPG filling body fully in contact with the irregular roof. This roof-adaptive end filling technology makes it a successful application in plugging the 1305 working face, which avoids problems of the low tight-connection ratio and secondary air-leakage channel resulted from the traditional filling technology, effectively improving coal production in terms of safety and high efficiency. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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14 pages, 2992 KiB

Open AccessArticle

Thermochemical and Toxic Element Behavior during Co-Combustion of Coal and Municipal Sludge

by Yongchun Chen, Herong Gui, Ziwei Xia, Xing Chen and Liugen Zheng

Molecules 2021, 26(14), 4170; https://doi.org/10.3390/molecules26144170 - 9 Jul 2021

Cited by 9 | Viewed by 2460

Abstract

The thermochemical and kinetic behavior of co-combustion of coal, municipal sludge (MS) and their blends at different ratios were investigated by thermogravimetric analysis. Simulation experiments were performed in a vacuum tube furnace to determine the conversion behavior of toxic elements. The results show [...] Read more.

The thermochemical and kinetic behavior of co-combustion of coal, municipal sludge (MS) and their blends at different ratios were investigated by thermogravimetric analysis. Simulation experiments were performed in a vacuum tube furnace to determine the conversion behavior of toxic elements. The results show that the combustion processes of the blends of coal and municipal sludge are divided into three stages and the combustion curves of the blends are located between those of individual coal and municipal sludge samples. The DTG_max of the sample with 10% sludge addition reaches a maximum at the heating rate of 20 °C/min, indicating that the combustion characteristics of coal can be improved during co-combustion. Strong interactions were observed between coal and municipal sludge during the co-combustion. The volatilization rates of toxic elements decrease with an increasing proportion of sludge in the blends during co-combustion, which indicates that the co-combustion of coal and sludge can effectively reduce the volatilization rate of toxic elements. The study reflects the potential of municipal sludge as a blended fuel and the environmental effects of co-combustion of coal and municipal sludge. Full article

(This article belongs to the Special Issue Barrier and Functional Materials from Waste Materials for Pollutants)

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