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Solvent-impregnated resins (CA−12/SIRs) have been prepared by using amidoxime resin waste as a polymeric support. The process of gallium (Ga) adsorption onto CA− 12/SIRs from a hydrochloric acid solution was examined in a batch experiment. It was found that CA− 12/SIRs exhibits excellent adsorbent properties with a saturated adsorption capacity of up to 31.2 mg·g−1 (318 K). In addition, CA− 12/SIRs showed an outstanding separation ability for Ga(Ⅲ), with a partition coefficient as high as above 2500 mL·g−1. The optimum pH value was found to be 2.75. Moreover, CA− 12/SIRs maintained an excellent adsorption performance for Ga(III), even after ten adsorption-elution cycles. For practical applications, the adsorption percentage of Ga(III) onto CA− 12/SIRs reached more than 99 % when using hydrochloric acid and sulfuric acid solutions. Thus, a low-cost adsorbent has been developed in the present study by which it is possible to purify gallium. Moreover, this study has provided a new direction for also other types of waste resins in the preparation of impregnated resins. • Reuse amidoxime resin waste to prepare solvent-impregnated resins. • Coefficient as high as above 2500 mL/g for recovering gallium. • It maintain an excellent adsorption performance for Ga(III) after ten cycles. [ABSTRACT FROM AUTHOR]

In this investigation, to separate and recover indium (In), the adsorption and desorption characteristics of indium in the sulfite-sulfuric acid system using IRA-900 resin and the adsorption mechanism were explored. When sodium sulfite and sulfuric acid concentrations were 0.5 mol/L, IRA-900 resin exhibited the best adsorption selectivity to indium, with an adsorption capacity of 95.56 mg/g(318 K), while the adsorption capacities of Al, Sr, Fe, Zn and Cu were weak. In(Ⅲ) adsorption by resin conforms to the second-order kinetic model, and the Langmuir model is more suitable for adsorption. In desorption experiments, 2 mol/L hydrochloric acid was selected as the desorption agent, with a desorption rate of 82.39 %. FT-IR (Fourier-transform infrared spectroscopy), SEM-EDS (Scanning electron microscopy with energy dispersive spectroscopy), XPS (X-ray photoelectron spectroscopy) and elemental analysis results indicated that the adsorption mechanism of indium could be attributed to the formation of an anionic complex between In3+ and HSO 3 -/HSO 4 -, which could be exchanged with Cl- on the resin to adsorb the metal ions. In addition, the column experiment could efficiently separate indium from simulated indium-containing solution. In(Ⅲ) recovery yield was about 99.6%, indicating its effective separation and recovery from ITO (Indium tin oxide) film. • Recovery of indium from the sulfuric acid solution using HSO 3 -/HSO 4 - ligand. • Indium form anion complexes with HSO 3 -/HSO 4 - to improve the resin selectivity for In(Ⅲ) from ITO film leaching solution. • Column experiments show that In (III) recovery yield was about 99.6 % from ITO film. • FT-IR and XPS results confirmed the formation of anion complexes, and the adsorption mechanism was the anion exchange. [ABSTRACT FROM AUTHOR]

Large amounts of xanthate wastewater generated from mineral beneficiation significantly threaten the ecological environment. MOF photocatalysis is considered as a promising method for the removal of xanthate that is environmentally friendly and has high efficiency. However, the defects in MOFs limit their large-scale application due to poor visible light absorption efficiency and stability in water. In this study, a novel composite material composed of g-C 3 N 4 /AgCl/Ti-MOFs was prepared, and the catalytic degradation effect of butyl xanthate solution under different catalyst ratios and reaction conditions was investigated. The results showed that the composite could still maintain excellent catalytic performance (degradation rate of 99.5% within 90 min) under xenon light and low dosage. The characterization results showed that this excellent photocatalytic performance could be attributed to the following three points: 1) The material could absorb up to 670 nm visible light absorption capacity; 2) excellent stability was achieved (86% degradation efficiency after six cycles); and 3) the Schottky junctions formed by Ag0 and other materials in the composite increased the transfer rate of e−/h+. The possible photodegradation mechanism was proposed according to UV–vis DRS and trapping experiments. [ABSTRACT FROM AUTHOR]

Developing nanoporous thermal insulation materials is an effective method for solving energy consumption problems. In this study, fumed silica based thermal insulating composite was prepared using a novel dry molding method. Thermal conductivity was measured using a guarded hot plate method in the steady state. The results indicated that this composite exhibited excellent thermal insulating performance, achieving an ultra-low thermal conductivity of 0.0205 W/mK at 100 °C. By analyzing the microstructure using field emission scanning electron microscopy (FESEM), we found that the fiber surface was modified by a 12 μm-thick layer of fumed silica particles that reduced solid heat transfer. However, at high temperatures, thermal insulating performance decreased rapidly, and thermal conductivity reached up to 0.119 W/mK at 500 °C. Based on this problem, a heat transfer model was constructed to explain micro-nano scale heat transfer mechanisms of this composite. The results indicated that gas-solid coupled thermal conductivity occupied a large proportion of 78.3% at 100 °C, but the value was only 0.015 W/mK. As the serving temperature increased, radiative heat transfer gradually occupied the dominant position in total heat transfer. Radiative thermal conductivity reached up to 0.101 W/mK at 500 °C, which was approximately 93.3% of total thermal conductivity. Therefore, it was apparent that the increase in radiative heat transfer was the main cause of the decline in thermal insulating performance at high temperatures. Additionally, the effect of the fiber mass ratio on thermal conductivity was investigated at various temperatures. Empirical and simulated data were compared, and the results revealed that the heat transfer model was basically consistent with experimental findings, achieving a mean error of only 4.78%. [ABSTRACT FROM AUTHOR]

The thermal insulating performance of expanded vermiculite is closely related to expansibility. A novel method of Mg2+ modification was proposed to improve the vermiculite expansion ratio. The modification process was characterised by energy dispersive X-Ray spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric-differential scanning calorimeter and scanning electron microscopy. Moreover, the thermal expansion experiment was performed to investigate the expansion behaviours of Raw-V and Mg–V samples at various temperatures. The result indicated that the introduction of Mg2+ could increase the vermiculite interlayer water content through hydration interaction, and the expansion ratio increased 13.7% under the heating temperature of 900 °C after modification. To explain the interaction of magnesium ion and water molecules, a molecular dynamics model was developed, and the simulation results were validated using the binding energy calculation. The results of this study can provide a new perspective and theoretical guidance for the commercial process of vermiculite expansion. [ABSTRACT FROM AUTHOR]

Bentonite is an important clay for preparation of adsorbents for potential treatment of industrial effluents. However, due to its natural occurrence as fine particles and swelling after moisture absorption, bentonite is difficult to be separated from the liquid for regeneration purpose, which limits its application in effluent treatment. In this study, two different bentonite-polypropylene composites were synthesized, i.e., with and without pore-enlarging treatment. They both showed strong ability to resist hydraulic agitation damage with a small breakage rate in water. The obtained results from SEM and XRD characterization revealed that the compounding of bentonite with the polypropylene was a physical process, and the structural characteristics of bentonite particles were maintained in the new products. The granular composite adsorbents were effective in removing Pb 2+ in aqueous solution. The suggested pore-enlarging treatment was verified as a successful operation to increase greatly the adsorption rate of contaminants on the granular bentonite composite. [ABSTRACT FROM AUTHOR]

Single- or dual-cation organomontmorillonites (OMt) modified by one or two cationic surfactants, respectively and/or cysteamine hydrochloride (CSH) were used to remove Zn 2 + and/or phenol from aqueous solutions. The OMt were characterized by XRD, FTIR spectroscopy and N 2 adsorption-desorption isotherm analyses. The adsorption results of Zn 2 + and phenol showed that OMt had much larger adsorption capacities of phenol than that of Na + -Mt or CSH-Mt in the presence of Zn 2 + . Experiments with the simultaneous presence of both the contaminants showed that one did not affect the adsorption of the other with all the adsorbents. The uptakes of Zn 2 + and phenol onto dual-cation OMt increased with increasing solution pH, contact time, temperature and initial concentration of Zn 2 + and phenol. The adsorption equilibrium time was 10 min for both contaminants and the maximum adsorption capacities of Zn 2 + and phenol were found under alkaline environment. The adsorption of both Zn 2 + and phenol can be better described by Freundlich model than Langmuir isotherm. Phenol adsorption onto OMt was caused primarily by partitioning into an organic phase in the interlayers, and the uptakes of phenol increased with increasing alkyl chain length and loading amount of surfactant in single-cation OMt. Zn 2 + adsorption onto dual-cation OMt was due to ion exchange, formation of complexes and/or precipitation mechanism depending on the solution pH. [ABSTRACT FROM AUTHOR]

Hydroxy-Al pillaring agent was prepared and used to modify montmorillonite (Mt), and the effects of temperature, initial Al 3 + concentration and contact time were investigated by using a batch technique. The results showed that the uptake of Al 13 by Mt increased with increasing temperature, initial Al 3 + concentration and contact time. The adsorption equilibrium was achieved in 12 h as determined by kinetics. The adsorption kinetics demonstrated that the adsorption of Al 13 by Mt followed the pseudo-second-order kinetic model. The adsorption isotherms at the temperatures of 40, 60, 80 and 90 °C were determined and simulated using Langmuir, Freundlich and Redlich-Peterson models. The three kinds of isotherms could represent the experimental data well. The specific surface areas and pillar density increased while the total porous volumes slightly decreased with increasing Al 3 + concentrations. The XRD result showed that adsorbed Al 13 ions were located in the Mt interlayer spaces through monolayer adsorption. Thermodynamic analysis of adsorption process showed that the adsorption of Al 13 by Mt was spontaneous, endothermic with increasing disorder during the adsorption process and mainly physical in nature. [ABSTRACT FROM AUTHOR]

Various montmorillonite (Mt) nanocomposite adsorbents were prepared with Al 13 cations, dodecyl trimethyl ammonium chloride (DTAC) or dodecyl amine (DA) and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and BET surface area and pore size analyses. The adsorption of hexavalent chromium, Cr(VI) onto various Mt nanocomposites as a function of adsorbent dosage, initial Cr(VI) concentration, contact time and solution pH was investigated. The results showed that the obtained nanocomposites had large basal spacing and good porous structure, and the specific surface areas followed the order: OH-Al-Mt > DA-Al-Mt > DTAC-Al-Mt > Na + -Mt > DTAC-Mt > DA-Mt. The removal efficiency of Cr(VI) ions increased with increasing the adsorbent dosage and contact time, but decreased with increasing initial Cr(VI) concentration, as expected. The adsorption of Cr(VI) was highly pH-dependent and the maximum removal efficiency of Cr(VI) was found in the acid environment. The adsorption equilibrium time was 2 h and the adsorption kinetic data of Cr(VI) on various adsorbents were well described by the pseudo-second-order kinetics model, which indicated that the adsorption reaction of Cr(VI) ions with the adsorbents was mainly due to chemical adsorption. Both the Langmuir model and Freundlich model fitted the equilibrium data well, which suggested that the Cr(VI) adsorption onto various adsorbents was both as monolayer and on heterogeneous surface conditions. The adsorption results indicated that among all the adsorbents used in this experiment, the dodecyl amine and Al 13 cations composited with Mt (DA-Al-Mt) was the most effective for removing Cr(VI) from wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel humidity self-regulating interior wall coating composite based on red mud was prepared. • The hygroscopicity of HRCRM were systematically investigated and analyzed. • Various properties of HRCRM were tested and the moisture absorption mechanism was analyzed. Aimed to resolve the problem of excessively high indoor humidity in subtropical areas and develop a new resource disposal technique for red mud, a novel humidity self-regulating interior wall coating composite based on red mud (HRCRM) was successfully prepared using red mud as a matrix material and vermiculite as a humidity regulator. The effects of component proportion, ambient humidity, exposure time on hygroscopicity of this composite were systematically investigated. This composite exhibited good humidity regulating ability with the largest water absorption rate of 16.38% under experimental conditions. Moreover, various properties were tested including surface drying time, hardness, adhesion, coating appearance, water resistance and reusability, meeting the national standard requirements well. The mechanism was comprehensively analyzed by XRD, TG-DTG, FESEM, and FTIR, indicating that the humidity self-adjusting function of HRCRM was realized by regulating the interlayer water storage of vermiculite. This study can provide theoretical and technical guidance for residential environment improvement in subtropical areas and comprehensive utilization of red mud. [ABSTRACT FROM AUTHOR]

Spent potliner (SPL) has been listed as a hazardous waste derived from aluminum electrolysis production with high cyanide content. In this study, a novel microwave-sensitizer synergistic technique was proposed to rapidly remove cyanides in SPL. The occurrence states and removal behavior of cyanide in SPL were studied systematically. The results show that cyanide in SPL mainly exists in the form of sodium cyanide and ferricyanide. The maximum cyanide removal rate of 96.67% was successfully achieved under the experimental conditions. Meanwhile, the synergistic removal mechanisms were comprehensively investigated by XRD, XRF, TG-DTA, TG-MS, and FactSage thermal simulation software. The sensitizer Fe 2 O 3 can accelerate the decyanation reaction by decreasing activation energy and acting as an oxidant. This study not only develops a high-efficiency and rapid cyanide removal technique, but also provides theoretical guidance for non-hazardous treatment of other cyanogens-containing wastes. [Display omitted] [ABSTRACT FROM AUTHOR]

There are a large number of tailings left over by industrial development the world over and the tailings are harmful to the environment for a long time, so it is very important to study how to reduce environmental pollution from tailings. Here, the acid producing potential of three types of tin polymetallic tailings from the same locality with different degrees of weathering and the forms of heavy metals that exist in these tailings were studied. The effects of pH of simulated acid rain, temperature and time on the leaching of heavy metals from the different tailings were investigated along with their leaching characteristics. In addition, stabilization mechanism of heavy metals was analyzed from the kinetic and microscopic aspects. The potential application of sodium diethyldithiocarbamate intercalated montmorillonite (DDTC-Mt) was studied for stabilizing tin polymetallic tailings. The leaching of heavy metals in tailings is mainly due to the oxidation of tailings, which in turn is closely related to the acid producing potential of tailings and the existing forms of heavy metals in them. The stabilization of heavy metals by DDTC-Mt is mainly due to coordination between DDTC and heavy metals in the interlayer of montmorillonite. DDTC-Mt revealed a superior stabilization property in remediation of heavy metals from tin-polymetallic tailings with high acid producing potential by enhancing the stability of heavy metals in tailings, for example, the stabilization rates of Mn and Zn were 89.11% and 93.89%, respectively. [Display omitted] • Na diethyldithiocarbamate intercalated montmorillonite (DDTC-Mt) was prepared. • Studied DDTC-Mt for stabilizing tin tailings for remediating acid mine drainage. • Stabilization rates of DDTC-Mt for Mn and Zn were 89.11 and 93.89%, respectively. • Metal stabilization by DDTC-Mt is mainly by coordination between DDTC and metals. • Mn and Zn leaching with or without DDTC-Mt conforms to acid production of tailings. [ABSTRACT FROM AUTHOR]

Abstract: This work investigated thermal stability of fumed silica based thermal insulating composites prepared by dry molding technology. The results showed that the composites could keep excellent thermal stability at the temperatures below 800°C. However, when the samples were used at higher temperatures (>800°C), the volume shrinkage increased sharply, which directly led to a serious deformation and then affected thermal insulating properties in applications. The utilization of fumed alumina could significantly improve thermal stability of the composites. When 5wt.% fumed alumina was added, the volume shrinkage decreased from 10.49% to 3.47% at 1000°C. The desirable results would be achieved by adjusting the amount of fumed alumina according to practical using temperature. In addition, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase transformations of the composites treated at different temperatures. [Copyright &y& Elsevier]

In this study, a sugarcane bagasse biochar/nano-iron oxide composite was prepared via a one-pot pyrolysis method by using the sugarcane bagasse-based solid waste and microwave as the raw material and energy source, respectively. The developed composite was characterized by BET, XRD, FT-IR and TEM and was applied for the removal of Cr (VI) from water. The composite was observed to be mainly composed of amorphous carbon, Fe 3 O 4 and Fe 2 O 3. The iron oxides were uniformly embedded on the surface of the carbon layer by van der Waals force. The sugarcane bagasse-based biochar/nano-iron oxide composite material exhibited an optimal Cr (VI) adsorption capacity of 55 mg/g under the experimental conditions specified in this study. The Cr (VI) adsorption mechanism of the Fe 2 O 3 /Fe 3 O 4 /WBC composite was explained through FTIR, XPS, charge transfer analyses, and density functional theory calculations (DFT). The deposition of Cr (VI) on the surface of the composite was attributed to electrostatic interaction, redox reactions and complexation between the Fe 2 O 3 /Fe 3 O 4 /WBC composite and Cr (VI) contained in the solution. [Display omitted] • A sugarcane bagasse-based biochar/nano-iron oxide composite was prepared via a one-pot pyrolysis method. • This composite features a more uniform distribution of iron oxides and a significantly improved Cr (VI) adsorption capacity. • The Cr (VI) adsorption of this composite is attributed to electrostatic interaction, complexation and redox reactions. [ABSTRACT FROM AUTHOR]