High Iodine Adsorption Research Articles

One-pot synthesis of nitrogen-rich aminal- and triazine-based hierarchical porous organic polymers with highly efficient iodine adsorption

Design and preparation of porous adsorption materials for dealing with environmental issues is attractive and promising, but it remains some challenges such as effective capture of radioactive iodine. Here, two nitrogen-rich porous organic polymers named PAN-B and PAN-T containing triazine and aminal linkages were synthesized through the polycondensation of the triazine-based hexamine (TDATPA) and two aldehyde monomers (benzaldehyde and 2-thenaldehyde) by polycondensation reaction. Fourier transform infrared (FT-IR) and 13C cross polarization/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR) measurements were performed to characterize their structures. The nitrogen-rich polymers (PAN-B and PAB-T) have hierarchical porous structures, with high Brunauer−Emmett−Teller specific surfaces (SBET) of 1254 m2/g and 1273 m2/g, respectively. And their micropore volume were satisfactory (0.275 cm3/g and 0.279 cm3/g). Moreover, PAN-B and PAN-T behaved very high iodine adsorption efficiency of 237 wt% and 243 wt% in 20 min, respectively, and had high iodine adsorption capacity of above 311 wt%.

High iodine adsorption performances under off-gas conditions by bismuth-modified ZnAl-LDH layered double hydroxide.

The effective adsorption of radioactive iodine is greatly desirable, but is still a significant challenge. In this manuscript, we report the synthesis of a bismuth-modified zinc aluminium layered double hydroxide (BiZnAl-LDH) via a co-precipitation method for the highly efficient absorption of iodine. Based on the robust chemical attraction between Bi and I2, BiZnAl-LDH exhibited highly effective iodine capture. Furthermore, to evaluate BiZnAl-LDH as an effective sorbent, it was characterized via X-ray powder diffraction (XRD), scanning electron microscopy-energy dispersion spectroscopy (SEM-EDS), and Fourier-transform infrared spectroscopy (FITR). In addition, to determine the morphology and iodine adsorption properties of BiZnAl-LDH, several studies were conducted. Through experiments, its elemental composition and vibration before and after iodine adsorption were analyzed via EDS and X-ray photoelectron spectroscopy (XPS). During the capture process, I2 is reduced to I− by the intercalated Bi3+via chemical adsorption, and the maximum adsorption capacity of BiZnAl-LDH for iodine reached up to 433 mg g−1, which had a surface area, average pore diameter, and pore volume of 36.259 m2 g−1, 2.374 nm, and 0.128 m3 g−1, respectively. Compared with several previous sorbents for iodine adsorption, BiZnAl-LDH exhibited an iodine adsorption of approximately two times that of the commercial Ag-exchange zeolite X, and furthermore BiZnAl-LDH is cost-effective. Thus, the substantial iodine capture by BiZnAl-LDH indicates that it is a capable sorbent for the effective elimination of radioactive iodine from reprocessing plant emissions.

High iodine adsorption by polyethyleneimine impregnated nanosilica sorbents

Abstract In this study, several nanoporous silica of SBA-15 and Aerosil types were impregnated with branched polyethyleneimine (PEI) with the aim to evaluate their iodine adsorption performance. First, the influence of the PEI content of the sorbents on their textural, structural, thermal and chemical characteristics, was studied by different techniques including N2 porosimetry at 77 K, SAXS, FTIR/ATR, elemental analysis, and TGA. Then, I2 adsorption capacities were determined in liquid phase (cyclohexane) at 20 °C, or during static or dynamic gas-phase tests, performed at 60 and 100 °C, respectively. An exceptionally high adsorption capacity superior to 2 g/g in the 20–100 °C range was determined for the SBA-15 sorbent with 38 wt% PEI (corresponding to N content of 12.3 wt%). The adsorption capacities of the sorbents increase almost linearly with the N content below this threshold, whereas the presence of excess PEI in the pores or at the pore mouth reduces the accessibility of I2 molecules to the most buried nitrogen sites. The interaction mechanisms of iodine with amine-containing molecules were investigated both from experiments carried out in solution and from the after-test characterization of the spent solids by DR-UV-Vis, FTIR/ATR, Raman spectroscopies and iodine desorption monitored by TGA. This allowed shedding light on the nature of charge-transfer complexes and the formation of ionic and neutral iodine ad-species during iodine adsorption.

Simultaneous improvement in tensile strength and adsorption capacity of activated carbon fibers during stabilization and activation of acrylic fibers

Simultaneous effects of stabilization degree, activation temperature and activation stretching on the adsorption and mechanical properties of acrylic-based activated carbon fibers (ACFs) were studied. ACFs were prepared by the stabilization of the acrylic fibers with different conditions; subsequently, they were impregnated in the KOH solution and activated at three different temperatures under three distinct imposed stretches. Tensile strength index, aromatization index, elemental analysis and density were used to evaluate the degree of the stabilization of the oxidized acrylic fibers prior to activation. The optimum conditions that led to the fabrication of high iodine adsorption and tensile strength ACFs were the stabilization degree of 56.2%, the activation temperature of 800 °C, and the stretching of 1%. The experimental iodine number and tensile strength of ACFs in the mentioned conditions were about 865 mg/g and 423 MPa, respectively. The results of the BET analysis for the optimized sample showed a surface area of 561 m2/g with an average pore diameter of 2.7361 nm. Moreover, the obtained ACFs were well characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscope and CCL4 adsorption test. Simultaneous improvement in the tensile strength and the adsorption capacity could make them suitable for possible high performance applications.

A Sponge‐Like 3D‐PPy Monolithic Material for Reversible Adsorption of Radioactive Iodine

3D polypyrrole (3D‐PPy) monolith is prepared by a simple chemical oxidation of pyrrole monomer using FeCl3 as an oxidant. The as‐prepared PPy monolith exhibits an abundant porosity and with a mesopore size of about 9.1 nm in diameter. Taking advantage of its mesoprous feature as well as the unique chemical composition, the 3D‐PPy is employed as the porous medium for adsorption and removal of radioactive iodine from environment. A high iodine adsorption capacity of 1.6 g g−1 for 3D‐PPy is obtained which is competing with that of those reported porous organic polymers. Besides, the adsorption kinetics and adsorption thermodynamic experiments show that the adsorption is dominated by the pseudosecond‐order kinetics and Langmuir models. Considering its simple and low cost‐effective preparing method, unique monolithic porous as well as π–π conjugated chemical structure, the resulted 3D‐PPy may be found useful applications for removal of radioactive iodine to address environmental issues.

Box-Behnken statistical design to optimize preparation of activated carbon from Limonia acidissima shell with desirability approach

Response surface methodology (RSM) coupled with Box-Behnken design (BBD) was employed to optimize the experimental conditions for the preparation of activated carbon from lignocellulosic biomass, Limonia acidissima shell by chemical activation method using phosphoric acid (H3PO4) as the activating agent. The effects of impregnation ratio, activation temperature and activation time were studied extensively. The obtained activated carbon was evaluated based on the total yield and iodine adsorption value. Each response had been described by a second-order polynomial regression model developed by ANOVA, which could properly determine the experimental data. Using desirability approach in multi-response optimization technique, following optimal conditions had been found such as impregnation ratio (24.21%), activation time (39.83min) and activation temperature (432.35°C). The carbon yield and iodine adsorption value approached 42.6324% and 951.889mg/g under these experimental conditions. The predicted responses presented a good agreement with the experimental data. The results showed that activated carbons prepared by chemical activation method had a high yield as well as high iodine adsorption value. The optimized activated carbon was further characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR).

Optimization of preparation process of activated carbon from chestnut burs assisted by microwave and pore structural characterization analysis

In this study, activated carbon was prepared from Chinese chestnut burs assisted by microwave irradiation with potassium hydroxide (KOH) as activator, and the process conditions were optimized employing Box-Behnken design (BBD) and response surface methodology (RSM). The optimized variables were irradiation time, impregnation time, and mass ratio of alkali-to-carbon, and the iodine adsorption value was used to evaluate the adsorption property of activated carbon. The optimal preparation conditions were determined as follows: irradiation time 17 min, impregnation time 240 min, and mass ratio of alkali-to-char 1.5:1. Meanwhile, the relatively high iodine adsorption value (1141.4 mg/g) was also obtained. Furthermore, the pore structural characterization of activated carbon was analyzed. The analyzed results showed a larger Brunauer-Emmett-Teller (BET) specific surface area (1254.5 m2/g) and a higher microporosity ratio (87.2%), a bigger total pore volume (0.6565 m3/g), but a smaller average pore size (2.093 nm), which demonstrated the obtained activated carbon possessed strong adsorption capacity and well-developed microporous structure. This research could not only establish the foundation of utilizing chestnut burs to prepare activated carbon, but also provide the basis for exploitation of Chinese chestnut by-products.Implications: Because Chinese chestnut burs are the by-products and usually discarded upon harvesting subsequently, the utilization of chestnut burs as a potential source of activated carbon is of great profit to the chestnut processing industries.

Preparation of pitch‐based carbon materials using a template and an orthogonal array design for super capacitors

Coal tar pitches (CTPs) are used as a supercapacitor precursor because they are of low cost and produce high carbon yields. In this reported work, a simple and feasible method for the fabrication of pitch-based carbon electrode materials with high capacitance was established using nanosized oxides as a template and the potassium hydroxide (KOH) activation method. The preparation conditions were optimised using an orthogonal array design. The electrochemical performance of the electrode materials was examined by constructing a single electrode capacitor in 6 mol l−1 KOH electrolyte; specific surface area was determined by N2 adsorption–desorption analysis and textural characterisation was conducted by transmission electron microscopy. Results showed that the synthetic carbon material possessed the highest iodine adsorption value of 2238 mg g−1 under optimum conditions (Al2O3 used as the template, an activation temperature of 700°C and a CTP/template mass ratio of 1:1), a high capacitance of 258 F g−1 at a current density of 0.5 A g−1 and good cycle stability.

SYNTHESIS OF ACTIVATED CARBON FROM JATROPHA SEED COAT AND APPLICATION TO ADSORPTION OF IODINE AND METHYLENE BLUE

This article provides evidence that jatropha seed coat residues can be used as a carbon source for preparing activated carbons that have good adsorption properties for iodine and methylene blue. Activated carbons were prepared using three different methods of activation, physical, chemical, and physico-chemical, for a range of activation temperatures (600°, 700°, 800°, and 900°C) and activation hold times (1, 2, and 3 h). The highest BET surface area (1479 m2 g−1) and the highest iodine adsorption (1511 mg g−1) were obtained with physico-chemical activation at a temperature of 900°C and a hold time of 2 h. This activated carbon gave higher BET surface area and iodine adsorption than commercial activated carbon (1169.1 m2 g−1 and 1076 mg g−1). The activated carbons prepared by physico-chemical activation at 900°C and 2 h were then tested for adsorption of methylene blue at a range of concentrations of methylene blue (100, 200, 300, 400, and 500 mg L−1). It was found that a Langmuir isotherm gave a better fit (R 2 = 0.999) to the observed adsorptions than a Freundlich isotherm (R 2 = 0.884). For the adsorption kinetics, a pseudo-second-order model gave a better fit (R 2 > 0.998, Δq e = 3.7%) than a pseudo-first-order model (R 2 ≈ 0.95, Δq e = 85.6%). These results suggest that chemisorption is the rate-controlling step for the adsorption of methylene blue. The experimental results show that jatropha seed coat is a lignocellulosic waste precursor for preparation of activated carbon that is an alternative source for preparation of commercial-grade activated carbons.

The comparison of two activation techniques to prepare activated carbon from corn cob

We report on the preparation of biomass-based activated carbons by the steam physical activation and KOH chemical activation methods. In addition, we also investigate their adsorption performance. By adjusting the reaction parameters, different carbon materials are prepared from corn residues and characterized using instrumental analyses such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Brunauer–Emmett–Teller (BET). It is found that the synthesized activated carbons exhibit high surface area (1600 m2 g−1) and large pore volume (2.01 cm3 g−1). Furthermore, the high methylene blue and iodine adsorption value and a considerable CO2 uptake (exceeding 1.5 mmol g−1) are attained with the activated carbons, showing their potential usage for the CO2 adsorbent.

A comparison of adsorption characteristics of various activated carbons

AbstractThe physico‐chemical characteristics of activated carbons obtained from different agricultural by‐products by pyrolysis in a stream of water vapor have been investigated. It was established that under the same conditions of treatment the physico‐chemical and adsorption characteristics of activated carbons depend on the composition of the initial raw materials. Activated carbon obtained from apricot stones has the best properties. It is characterized by a large specific surface area and micropores volume and high iodine and methylene blue adsorption activity. The activated carbons produced from cherry stones and grape seeds are characterized by predominating meso‐ and macropores structure. It can be supposed this is related to the larger content of lignin in those materials.