JOURNAL OF MOLECULAR LIQUIDS
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2020
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IF 5.065
Yong Chen,Shah Zeb,XiuJing Peng,Yiming Zhao,Chengjin Xu,Ling Li,Yu Cui,Guoxin Sun
In this study, polystyrene microspheres with diquaternary ammonium cation structure N + -C-C-N + were designed and synthesized to realize the efficient removal of Cr(VI) in neutral wastewater. The key adsorption sites, N + -C-C-N + , can match the charge and the configuration of chromate anion, which greatly improves the ability of associating chromate anions under neutral conditions. Density functional theory (DFT) was used to compute the adsorption energies between Cr(VI) and N + -C-C-N + , which proved the structure's effectiveness. The adsorbent can work under a wide pH range and greatly improved the efficiency of removing Cr(VI) from wastewater under neutral and alkaline conditions. The adsorbent was characterized with Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Batch adsorption experiments show that the removal efficiency of Cr(VI) remains above 95% in pH values range from 2.0 to 12.0. The maximum capacity of the adsorption achieved within 40 min and conformed to the pseudo-second-order kinetic. According to the Langmuir model, the maximum capacity reached to 89.77 mg g −1 at pH 7.0. Regeneration tests show that adsorbent has good reusability and can be used in the repeated adsorption. FTIR and XPS analysis demonstrated the electrostatic interactions mechanism between the N + -C-C-N + and Cr(VI) proposed for the adsorption process.
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JOURNAL OF POROUS MATERIALS
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2020
·Vol. 27
·期 6
·1701-1710
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IF 2.183
Zhao Shifeng,Fan Xin,Yang Junshan,Huang Hanhan,Xia Caifeng,Jing Ruisen,Wu Mi,Zhang Zhilei,Liu Aiju,Zhang Qian,Meng Zilin
The application of nanoscale zero-valent iron (NZVI) in a promising remediation strategy was challenged by easy aggregation and surface passivation. To enhance their performance of Cr(VI) removal, layered double hydroxides (LDHs) supported NZVI (NZVI@LDH) with different loading amount via an in-situ way was successfully synthesized. The structural characterization and morphology revealed LDHs could stabilize and uniformly disperse NZVI on the surface of LDHs layer, however, superabundant NZVI still leaded to a visibly aggregation. Cr(VI) removal by NZVI@LDH was higher than that of the sum of NZVI and LDHs, revealing a synergistic effect within this system. The results of Cr(VI) removal displayed with the growth of iron loading amount, the removal efficiencies were raised firstly but declined afterwards. Kinetics studies for all samples showed Cr(VI) removal well fitted pseudo-second-order model and isotherm data was well described by Langmuir model. The effects of initial concentration and pH on Cr(VI) removal were also examined. Cr(VI) in the wastewater was reduced by NZVI to Cr(III), NZVI was oxidized into Fe(II) and Fe(III). The excellent removal performance suggested a promising strategy in sewage water remediation.
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ENVIRONMENTAL TECHNOLOGY
·
2020
·
IF 2.213
Lihua Liu,Zhengchi Yang,Lu Zhao,Jinyan Liu,Xiong Liu,Jianrong Xue,Anping Tang
The adsorption characteristic and mechanism of poly(N1,N1,N3,N3-tetraallylpropane-1,3-diaminium chloride) (PTAPDAC) toward Cr(VI) ions were systematically investigated. Results showed that the removal efficiency of PTAPDAC toward Cr(VI) could reach above 98% at pH = 3–6. The equilibrium data of Cr(VI) adsorbed by PTAPDAC fitted the Langmuir model well, and the maximum sorption capacity deduced from the Langmuir model at 293 K was 273.17 mg g−1. The adsorption of PTAPDAC toward Cr(VI) was rapid and reached equilibrium within 60 min, and the adsorption kinetic process was relevant to the pseudo-second-order kinetic model. Moreover, the activation energy Ea was calculated as −22.505 kJ mol−1. The adsorption processes were spontaneous and exothermic driven by an increase in entropy, which involved electrostatic attraction, ion exchange, and redox reactions. The X-ray photoelectron spectroscopy analysis revealed that approximately 64.5% of Cr(VI) reduced to be Cr(III), and 24.29% of –C–NH+ deprotonated. The combination of reduced Cr(III) with tertiary amine groups resulted in a positively charged tertiary amine group, which further promoted Cr(VI) adsorption, thereby increasing the adsorption capacity of PTAPDAC toward Cr(VI). Therefore, PTAPDAC has a broad application prospect in removing Cr(VI) ions in wastewater.
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ENVIRONMENTAL TECHNOLOGY
·
2020
·
IF 2.213
Yali He,Hongliang Sun,Weijiang Liu,Wenjie Yang,Aijun Lin
Fe/Al bimetallic particles were synthesized by chemical deposition. The materials were characterized by XRD and SEM. The structures of material with lower iron loading are solid ball like with a small amount of zero-valent iron. The structures of material with higher iron loading are porous ball like whose outer surface is almost entirely coated with zero-valent iron and provides more active sites. Different parameters affecting Cr(VI) removal rates were listed as research targets. The results showed that the removal rates can reach more than 90% under optimum conditions. In addition, Cr(VI) removal experiment was in accordance with the pseudo-first-order kinetics. SEM, FT-IR and XPS analysis were characterized after the reaction and the results proved that galvanic cell effect, the properties of reducibility of zero-valent metals, Fe(III)-Cr(III) mix phase hydroxides were the main surface reaction mechanisms for the reaction of Fe/Al bimetal with Cr(VI).
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Journal of the Taiwan Institute of Chemical Engineers
·
2020
·
IF 4.794
Qiuyue Zhang,Kaijie Dong,Qiang Liu,Qinze Liu,Jinshui Yao
Herein, we propose an excellent absorbent, poly (catechol-tetraethylenepentamine) coating onto SiO 2 NH 2 microsphere, which is fabricated via a simple synthesis route. The effect of different molar ratio of catechol on the adsorption properties of silica modified composite was studied. The poly (catechol-tetraethylenepentamine)@SiO 2 NH 2 (PCTA@AS) exhibits outstanding adsorption to Cr(VI) compared to SiO 2 NH 2 . The structural characterizations and adsorption performance of the product are analyzed by SEM, TEM, FTIR, XPS, etc. Many factors affecting the adsorption behavior of PCTA@AS were systematic explored, including pH, initial Cr(VI) concentration, contact time, adsorbent dosage, and temperature. The experimental data revealed that the adsorption behavior is suitable to be described by pseudo-second-order kinetic model and Langmuir isotherm model. The maximum uptake capacity of PCTA@AS composite up to 400.85 mg/g at 303 K, is much higher than the pure SiO 2 NH 2 , and the removal rate close to 100% when the initial concentration of the solution is below 180 mg/L. Accordingly, the removal process of the material is spontaneous and endothermic and attributed to the partial reduction of Cr(VI) to Cr(III). Based on these, it is considered that the PCTA@AS with good regeneration ability and is expected to be an ideal material on the removal of Cr(VI) from sewage.
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ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2020
·
IF 7.864
Xuyan Gao,Yue Zhang,Fengmin Li,Boyang Tian,Xiao Wang,Zhiwei Wang,Jesse C. Carozza,Zheng Zhou,Haixiang Han,Chunhua Xu
The sulfidation of zero valent iron (ZVI) to an Fe@FeSx (S-ZVI) composite has been intensively explored in the ZVI field. Yet, further benefits from the FeSx coating layer are seldom realized, especially those effectively using its intrinsic physical and chemical properties for elaborate design. Here, we demonstrate that in a traditional Cr(VI) sequestration reaction, the FeSx layer displays a great utility in immobilizing molecules containing hydroxyl groups (−OH) and hence, attracting Cr(VI) complexes chelated with carboxyl organics (RCOOH). Such intermolecular attraction readily promotes the diffusion of the Cr(VI) complexes to the S-ZVI surface, affording a higher reaction rate for the Cr(VI) sequestration process. In addition, the above mechanism was used to guide a rational selection of molecules incorporating both hydroxyl and carboxyl functional groups with a proper ratio and thereby, a significantly improved reaction efficiency was achieved. Furthermore, the FeSx phase was revealed to be consumed in the reaction, acting as a supplementary reductant. This work is the first to unveil the relationship between molecules with specific functionalization and the FeSx phase, providing a general rule in choosing appropriate reaction media for Cr(VI) sequestration and related reactions.
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SEPARATION AND PURIFICATION TECHNOLOGY
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2021
·
IF 7.312
Shanshan Mao,Tao Shen,Tong Han,Fan Ding,Qing Zhao,Manglai Gao
The functionalized organo-vermiculite (BDIEP-Vt) is prepared by combining the imidazole-ether-containing gemini surfactant into vermiculite, and serves as adsorbent for single and simultaneous removal of triclosan (TCS), p -chlorophenol (4-CP) as well as Cr(VI) from aqueous solution. The physicochemical properties of the resultant BDIEP-Vt are characterized via FT-IR, XRD, TG-DTG, SEM, TEM as well as BET analysises. In single system, the results of standard batch adsorption experiment represent that BDIEP-Vt could adsorb the three contaminants (220.4 mg/g for TCS, 74.6 mg/g for 4-CP, 18.4 mg/g for Cr(VI)) effectively as well as rapidly within 5–10 min. The adsorption process is in great pertinence with pseudo second-order model, and the equilibrium data are befitted Freundlich model greatly for TCS and Cr(VI), while Langmuir model suites for 4-CP. In TCS-Cr(VI)/4-CP-Cr(VI) binary system, the maximum adsorption capacity of BDIEP-Vt for TCS, 4-CP as well as Cr(VI) is 182.1, 44.1 and 12.7 mg/g, respectively. The trend variation of φ value indicates an antagonism effect is exerted by Cr(VI) ions on TCS/4-CP removal whereas Cr(VI) uptake is slightly affected. Interestingly, the impact sequence of Cr(VI) on the removal of TCS/4-CP follows as: TCS < 4-CP. The adsorption mechanism is clarified by means of the characterization of spent adsorbent together with theoretical calculations: (i) Expect for hydrophobic interaction, the adsorption of TCS/4-CP is mainly driven by π-π along with π-π stacking interactions; (ii) Both π-π (betwixt imidazole ring and orthogonally benzene) and π-π stacking interactions (among the orthogonally benzenes) are more stronger than imidazole-isolated benzene/isolated benzene-isolated benzene systems; (iii) The removal of Cr(VI) is controlled by electrostatic interaction. The study proves that BDIEP-Vt as an effective multifunctional adsorbent has a momentous application prospect in potential environmental remediation.
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Polymers
·
2021
·Vol. 13
·期 21
·3691
·
IF 4.329
Norah Salem Alsaiari,Khadijah Mohammedsaleh Katubi,Fatimah Mohammed Alzahrani,Abdelfattah Amari,Haitham Osman,Faouzi Ben Rebah,Mohamed A. Tahoon
Heavy metals are toxic substances that pose a real danger to humans and organisms, even at low concentration. Therefore, there is an urgent need to remove heavy metals. Herein, the nanocellulose (NC) was synthesized by the hydrolysis of cellulose using sulfuric acid, and then functionalized using polypyrrole (ppy) through a polymerization reaction to produce polypyrrole/nanocellulose (ppy/NC) nanocomposite. The synthesized nanocomposite was characterized using familiar techniques including XRD, FT-IR, SEM, TEM, and TGA. The obtained results showed a well-constructed nanocomposite with excellent thermal stability in the nano-sized scale. The adsorption experiments showed that the ppy/NC nanocomposite was able to adsorb hexavalent chromium (Cr(VI)). The optimum pH for the removal of the heavy metal was pH 2. The interfering ions showed minor effect on the adsorption of Cr(VI) resulted from the competition between ions for the adsorption sites. The adsorption kinetics were studied using pseudo 1st order and pseudo 2nd order models indicating that the pseudo second order model showed the best fit to the experimental data, signifying that the adsorption process is controlled by the chemisorption mechanism. Additionally, the nanocomposite showed a maximum adsorption capacity of 560 mg/g according to Langmuir isotherm. The study of the removal mechanism showed that Cr(VI) ions were removed via the reduction of high toxic Cr(VI) to lower toxic Cr(III) and the electrostatic attraction between protonated ppy and Cr(VI). Interestingly, the ppy/NC nanocomposite was reused for Cr(VI) uptake up to six cycles showing excellent regeneration results. Subsequently, Cr(VI) ions can be effectively removed from aqueous solution using the synthesized nanocomposite as reusable and cost-effective adsorbent.Keywords:adsorption;cellulose;polypyrrole;nanomaterials;Cr(VI);water treatment
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JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2021
·
IF 8.128
Dingliang Dai,Jianhao Qiu,Lu Zhang,Hong Ma,Jianfeng Yao
A subtle flower-like MIL-125-NH 2 @BiOI was fabricated by a facile solvothermal method for simultaneously eliminating Cr(VI)/tetracycline mixed pollutants under visible light . The strong interaction between amino in MIL-125-NH 2 and Bi 3+ of BiOI promotes the formation of this unique inlaid structure and enables the favorable contact between MIL-125-NH 2 and BiOI, thus accelerating the transfer of charge carriers. Remarkably, MIL-125-NH 2 @BiOI displays a superior activity compared with that of two monomers for the photocatalytic reduction of Cr(VI) and degradation of tetracycline . More significantly, the photocatalytic efficiency can be further boosted in the coexistence of Cr(VI) and tetracycline , which is 1.8 and 1.6 times that of single Cr(VI) and tetracycline, respectively. The synergistic effect between Cr(VI) reduction and tetracycline oxidative degradation can further facilitate the separation of photo-induced electrons and holes, resulting in the improved efficiencies in the Cr(VI)/tetracycline coexistent environment. This work sheds light on that MOF-based photocatalysts possess huge potential for practical environmental remediation.
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SCIENCE OF THE TOTAL ENVIRONMENT
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2021
·
IF 7.963
Yunfei Zhang,Qiang Zhao,Baoliang Chen
In materials science, “green” synthesis has gotten a lot of interest as a reliable, long-lasting, and ecofriendly way to make a variety of materials/nanomaterials, including metal/metal oxide nanomaterials . To accommodate various biological materials, green synthesis of metallic nanoparticles has been used (e.g., bacteria, fungi, algae, and plant extracts). In this work, Shewanella oneidensis MR-1 was used to biosynthesize palladium nanoparticles (bio Pd) under aerobic conditions for the Cr(VI) bio-reduction. The size and distribution of bio-Pd are controlled by adjusting the ratio of microbial biomass and palladium precursors. The high cell: Pd ratio has the smallest average particle size of 6.33 ± 1.69 nm. And it has the lowest electrocatalytic potential (−0.132 V) for the oxidation of formic acid , which is 0.158 V lower than commercial Pd/C (5%). Our results revealed that the small size and uniformly distributed extracellular bio-Pd could achieve completely catalytic reduction of 200 mg/L Cr(VI) solution within 10 min, while the commercial Pd/C (5%) need at least 45 min. The bio-Pd materials maintain a high reduction during five cycles. Microorganisms play an important role in the whole process, which can fully disperse palladium nanoparticles, completely reduce Cr(VI), and effectively adsorb Cr(III). This work expands our understanding and provides a reference for the design and development of efficient and green bio-Pd catalysts for environmental pollution control under simple and mild conditions.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2021
·
IF 3.764
Liming Zhao,Lijun Guo,Yuling Tang,Jianfei Zhou,Bi Shi
Research on the rational design of photocatalysts for efficient hexavalent chromium (Cr(VI)) reduction from Cr(VI)-containing wastewater has attracted widespread attention. In this paper, a novel g-C3N4/C/Fe2O3 photocatalyst was successfully synthesized by anchoring g-C3N4 nanosheets onto C/Fe2O3 that was prepared using collagen fiber as the biochar resource following the Fe tanning mechanism to reduce Cr(VI) under artificial solar irradiation. Under the same conditions, the as-prepared g-C3N4/C/Fe2O3 photocatalyst exhibited higher Cr(VI) reduction efficiency than g-C3N4, and the Cr(VI) reduction efficiency increased as Fe content in the g-C3N4/C/Fe2O3 photocatalyst increased. The enhanced photocatalytic performance was primarily ascribed to the formation of an indirect Z-scheme heterojunction between C/Fe2O3 and g-C3N4, which improved the separation efficiency of the photogenerated charge carrier. Furthermore, radical trapping indicated that photoinduced electrons (e–) were the main factor for Cr(VI) reduction. This work provides guidance for high value-added utilization of collagen fiber in constructing efficient light-driven photocatalysts and practical Cr(VI) removal from wastewater.
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SCIENCE OF THE TOTAL ENVIRONMENT
·
2019
·
IF 5.589
Yalan Wang,Nan Zhang,Danni Chen,Dan Ma,Guoguang Liu,Xuegang Zou,Yuping Chen,Ranjun Shu,Qingyun Song,Wenying Lv
The adsorption behavior and mechanism of Cr(VI) on different acid-modified UiO-66s (Form-UiO-66 and Ac-UiO-66) were systematically investigated for the first time through a series of characterizations, and theoretical calculations of batch experiments. The characterization results demonstrate that acid-modified UiO-66 exhibited a larger specific surface area than did unmodified UiO-66. In addition, since the regulator (formic acid) of Form-UiO-66 was the stronger competition, the specific surface area of Form-UiO-66 (1138 m 2 g −1 ) was larger than that of Ac-UiO-66 (915 m 2 g −1 ). Under optimal experimental conditions, the maximum adsorption capacity of Cr(VI) was 243.9 mg g −1 on Form-UiO-66, and 151.52 mg g −1 on Ac-UiO-66, which was far higher than on the reported unmodified UiO-66 (36.4 mg g −1 ). The results of pH testing, zeta potential, and X-ray photoelectron spectroscopy analysis indicate that Cr(VI) ions were fixed to adsorbent surfaces via electrostatic adsorption. Acid-modified UiO-66 increased the surface active site via the increase in its specific surface area to enhance adsorption capacity of Cr(VI). These results indicated that both the surface charge and specific surface area of the adsorbent primarily determined the Cr(VI) adsorption capacity. Acid modified UiO-66 exhibited enhanced adsorption capacity, stability, and regeneration, compared to traditional adsorbents, and these results provide new insights into adsorption by MOFs.
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