Journal of Environmental Chemical Engineering
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2021
·
IF 5.909
Tao Li,Lin Dai,Yixin Huang,Siwen Pan,Zijun Pang,Jing Zou
Nowadays, a number of spectrophotometric methods for Cr(VI) determination have been developed. Whereas most of them are sensitive to pH, metallic ions, temperature, etc, which render them out of feasibility and may result in erroneous measurement. Therefore, to overcome these drawbacks, a new spectrophotometric method with rapid detection, high accuracy and strong anti-interference ability was established. This method is based on the oxidative coloration of N,N -diethyl- p -phenylenediamine (DPD) and Cr(VI) to generate pink-colored DPD •+ radicals which showed maximum absorbance at 551 nm. Accordingly, different reaction parameters were optimized, the calibration curves (linear range 0.85–60 µM) were established with a high sensibility of (3.05 ± 0.02) × 10 4 M −1 cm −1 . The LOD and LOQ were determined to be 0.26 µM and 0.85 µM respectively, accompanied with a stoichiometric coefficient of near 1:3 (1:2.78). The DPD method exerted a satisfactory accuracy in natural water samples and a pretty good anti-interference performance towards various common co-existing metallic ions. Moreover, this method was successfully applied in the Cr(VI)-sulfite and Cr(VI)-hydroxylamine systems. Overall, the study highlights the DPD method as a promising approach for the Cr(VI) determination and provides a new perspective for the practices of spectrophotometry .
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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
·
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 & Innovation
·
2020
·
IF 3.356
Jiahong Wang,Saleem Atif,Dan Zhang
EGTA functionalized magnetic microsphere (Fe 3 O 4 @SiO 2 @EGTA) was prepared for the removal of Cr(III) from highly saline organic wastewater environment. The synthesized adsorbent was characterized with Fourier transform infrared (FTIR), powder x-ray diffraction (XRD), thermogravimetric analysis (TGA) and x-ray photoelectron spectrometry (XPS). The characterization techniques depicted the successful surface modification of magnetic particles (Fe 3 O 4 @SiO 2 ) with the functional groups of EGTA without changing its crystal structure. The maximum adsorption amount of Cr(III) was 25.25 mg ⋅ g −1 at pH 4.0. The Langmuir isotherm was well fitted on the adsorption data, while adsorption equilibrium was achieved in first 15 min, and the equilibrium data well explained by pseudo second order model. The smaller concentrations of inorganic cations (Na + , Ca 2＋ , Mg 2 + ), organic acids (EDTA, Citric acid , Formic acid) and complexing agent with high salt system reduce the adsorption capacity to some extent, but after that the higher concentrations of these competing species have no apparent effect on the adsorption performance. According to the XPS analysis, the carboxyl and amino groups were responsible for the adsorption of Cr(III), while the main mechanism of adsorption were coordination complex and electrostatic interaction. The prepared adsorbent can be readily isolated by external magnetic field and regenerated for several times and still possess higher adsorption performance.
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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
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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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SEPARATION AND PURIFICATION TECHNOLOGY
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2020
·
IF 5.774
Meesam Ali,Usman Farooq,Shuguang Lyu,Yong Sun,Ming Li,Ayyaz Ahmad,Ali Shan,Zain Abbas
Various controlled release calcium peroxide nanoparticles (CR-nCPs) were synthesized and their characteristics and effectiveness in trichloroethylene (TCE) degradation were assessed. In this concern, calcium peroxide nanoparticles (nCPs) were initially prepared with four different surface stabilizers (PEG 200, PVP, PVA and DEGMME) to inhibit the irreversible agglomeration of nCPs by chemical precipitation method, then CR-nCPs were further synthesized by the coating of the selected polymers on nCPs. The characterizations of nCPs and CR-nCPs were performed using XRD, FESEM, TEM, FTIR, BET and TGA techniques. The results displayed the prepared nCPs in nano size with good dispersion, reliable purity, and standard surface area. The characterizations of CR-nCPs confirmed the success of polymer coating on nCPs. The H 2 O 2 release profiles of the prepared CR-nCPs were determined by UV spectrophotometer. PVA@nCP-PVA has shown the maximum H 2 O 2 controlled release efficiency (CRE) of 50.2%. The prepared CR-nCPs were tested for TCE degradation at optimum conditions of Fe(II) = 1.1 mM and CR-nCPs = 50 mg/L. The maximum removal percentages of 99.7% after 120 min and 66% after 180 min were achieved by CR-nCPs having moderate CRE (16.0–20.3%) and high CRE (50.2%) respectively. It was found that the CRE of CR-nCPs and their TCE degradation efficiencies have an inverse relationship. The CR-nCPs with moderate CRE were further employed for investigating the effect of polymer coating with increased polymer quantity (1:40). With the increase in polymer coating quantities, TCE removal percentages of 98.17%, 82.02% and 79.29% were obtained by PEG 400@nCP-DEGMME, DEGMME@nCP-DEGMME and PEG 400@nCP-PEG 200 after 360 min, respectively. In conclusion, this work suggests that CR-nCPs with moderate and high CRE are advantageous, in long term effectiveness, to potentially degrade TCE in groundwater remediation practice.
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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
·
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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DALTON TRANSACTIONS
·
2021
·Vol. 50
·期 28
·9746-9753
·
IF 4.39
Yan He,Tao Yu,Hui Wen,Rui Guo
For the electrocatalytic oxygen evolution reaction (OER) in alkaline media, there is an urgent need to optimize the adsorption strength of OH*. Here, a flower-like hybrid of Cr-doped FeOOH/Ni(OH)2 was used as an OER catalyst with a low overpotential of 291 mV at 50 mA cm−2. The results showed that faster charge transfer was achieved at the electrode/solution interface during the OER process after the FeOOH/Ni(OH)2 was modified by Cr, which facilitates the rate-determining step of the Volmer reaction. Furthermore, the results of faradaic efficiency and X-ray photoelectron spectroscopy (XPS) measurements confirmed that the synergistic effect between the ternary metal and oxygen vacancies led to excellent OER performance. This work provides a new strategy for the preparation of high-efficiency and low-cost oxygen evolution electrocatalysts.
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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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