查找使用阿拉丁产品的科研文献

Structural design of a cellulose-based hyperbranched adsorbent for the rapid and complete removal of Cr(VI) from water

Fei Xue,Hui He,Hang Zhou,Zongyan Quan,Zhiping Chen,Qi Wu,Hongxiang Zhu,Shuangfei Wang

To solve the problem that cellulose-based adsorbents cannot remove Cr(VI) from water to the drinking water standard (US EPA, 0.05 mg/L) within 5 min due to imbalance of the high amine density and high-efficiency diffusion dynamics. A cellulose-based hyperbranched adsorbent (MCC/HBPA-0.88) was designed and prepared via cross-linking with microcrystalline cellulose (MCC) and amino-terminated hyperbranched polymers (HBP-NH 2 ). This strategy for liquid–solid phase one-step rapid conversion could effectively increase the conversion rate of the reactants (above 99%). The cellulose-based hyperbranched adsorbent possessed high amino density (10.63 mmol/g), high swelling rate (341%) and three-dimensional hyperbranched structure. It could rapidly and completely remove Cr(VI) from water with a low level of Cr(VI) (1.02 mg/L), and the residual Cr(VI) concentration satisfied the safe drinking level standards within 1 min, which exceeds the absorption rates of cellulose-based adsorbents that have been reported in the literatures.

Three dimensional flower-like magnetic polyethyleneimine@MoS2 composites for highly efficient removal of Cr(VI) and Pb(II) ions

Chengwei Sun,Gang Song,Lili Chen,Xuemei Ren,Changlun Chen

Magnetic Fe 3 O 4 nanoparticles were coated by polyethyleneimine (PEI), and then Fe 3 O 4 @PEI was further modified with MoS 2 by the hydrothermal method to fabricate 3D flower-like structured magnetic polyethyleneimine@MoS 2 (MP@MoS 2 ) composites, and the composites were served as efficient adsorbents to capture Cr(VI) and Pb(II) from aqueous solution. The effects of temperature, pH, shaking time and environmental conditions on adsorption performance of MP@MoS 2 towards Cr(VI) and Pb(II) have been conducted by batch adsorption experiments. The prepared MP@MoS 2 exhibited high adsorption capacities (192.30 mg/g for Cr(VI) at pH 3.0 and 256.41 mg/g for Pb(II) at pH 6.0) and the adsorption equilibrium could be achieved in a short time. Moreover, MP@MoS 2 composites with high saturation magnetization could be simply separated under an external magnet. Combined experiments and spectral analysis, the underlying adsorption mechanism for Cr(VI) on MP@MoS 2 was mainly attributed to the reduction of Cr(VI) to Cr(III), and the removal of Pb(II) was due to the complexation with sulfur groups and amino-groups. Consequently, the prepared 3D flower-like structured MP@MoS 2 has a great potential for the practical application in removing Cr(VI) and Pb(II) from the aquatic environment.

High-efficiency photocatalytic reduction of Cr(VI) by Z-scheme electron transfer in UiO-66-NH2@HDU-25 heterojunctions

Wen Lu,Chen Wang,Wenhui Song,Zhixiong Zhang,Chengde Xie,Jianjun Wang

The heavy metal ion hexavalent chromium (Cr(VI)) in wastewater significantly threatens public health. Heterojunction photocatalysts typically demonstrate high reduction efficiency in water for Cr(VI) contamination. Overcoming the drawbacks of single metal organic frameworks (MOFs) or covalent organic frameworks (COFs), MOF@COF heterostructures inherit the advantages of large porosity, high surface area, and multiple active sites of single components. Herein, we report novel hybrid UiO-66-NH2@HDU-25 heterojunctions based on a condensation reaction. The optimal ratio of UiO-66-NH2@HDU-25 presented significantly superior photocatalytic activity to most reported MOFs and COFs due to heterojunction formation, which promoted charge separation. Under identical conditions, the optimally formulated UiO-66-NH2@HDU-25 could remove over 99% of Cr(VI), approximately 1.8 and 2.6 times the original UiO-66-NH2 and HDU-25 levels. Furthermore, the UiO-66-NH2@HDU-25 (8 : 1) heterojunction demonstrated favorable reusability and stability over five reaction cycles. Various experiments and density functional theory (DFT) calculations investigated the charge carrier transport pathways and possible photocatalytic mechanisms. The Z-scheme mechanism for the photocatalytic Cr(VI) reduction by UiO-66-NH2@HDU-25 was proposed and validated. This work aims to open new horizons for preparing novel photocatalyst heterojunctions with excellent visible light responsiveness for environmental water remediation.

In situ preparation of visible-light-driven carbon quantum dots/NaBiO3 hybrid materials for the photoreduction of Cr(VI)

Yixiao Wu,Chunlong Chen,Shu He,Xuesong Zhao,Shaobin Huang,Gongchang Zeng,Yingying You,Ying Cao,Lishan Niu

In this study, different carbon quantum dots (CQDs)/NaBiO 3 hybrid materials were synthesized as photocatalysts to effectively utilize visible light for the photocatalytic degradation of contaminants effectively. These hybrid materials exhibit an enhanced photocatalytic reduction of hexavalent chromium (Cr(VI)) in the aqueous medium. Zero-dimensional nanoparticles of CQDs were embedded within the two-dimensional NaBiO 3 nanosheets by the hydrothermal process. Compared with that of the pure NaBiO 3 nanosheets, the photocatalytic performance of the hybrid catalysts was significantly high and 6 wt.% CQDs/NaBiO 3 catalyst exhibited better photocatalytic performance. We performed the first-principles density functional theory calculations to study the interfacial properties of pure NaBiO 3 nanosheets and hybrid photocatalysts, and confirmed the CQDs played an important role in the CQDs/NaBiO 3 composites. The experimental results indicated that the enhanced reduction of Cr(VI) was probably due to the high loading of CQDs (electron acceptor) on NaBiO 3, which made NaBiO 3 nanomaterials to respond in visible light and significantly improved their electron-hole separation efficiency.

Removal of Cr(VI) and Ag(I) by grafted magnetic zeolite/chitosan for water purification: Synthesis and adsorption mechanism

Xiaoqi Liu,Yanyun Zhang,Yan Liu,Ting'an Zhang

In this paper, a novel grafted zeolite/Fe 3 O 4 /chitosan (ZMC-MAH-TEPA) adsorbent was greenly synthesized and evaluated for the removal of Cr(VI) and Ag(I) in single and bi-component solutions. The characterization data of XRF , XRD, FT-IR, VSM, TGA , BET and SEM showed the successful fabrication of the adsorbent with abundant -NH 2 and -NH- as well as great recovery properties (11.70 emu/g). The effects of experimental parameters, including pH value, initial concentration, temperature, time, and coexisting ions on single and bi-component adsorption, were investigated. The results demonstrated that the adsorption capacities increased with the enhanced shaking time and concentration until equilibrium was reached. The optimum pH value was 3 for Cr(VI) adsorption and 5 for Ag(I) adsorption. The maximum adsorption capacities for Cr(VI) and Ag(I) ions, obtained by the Langmuir model, were 50.75 and 70.12 mg·g −1 in single metal solutions and 45.45 and 58.94 mg·g −1 in bi-component metal solutions (Cr(VI)/Ag(I) = 1:1), respectively. Additionally, the adsorption mechanism of Cr(VI) and Ag(I) was explained in terms of electrostatic interaction and hydrogen bonding between metal ions and -NH 2 and -NH- in ZMC-MAH-TEPA. Taken together, this study provides a clean approach to synthesizing chitosan-based adsorbents for the efficient removal of Cr(VI) and Ag(I) ions.

Enhanced Cr(VI) removal in the synergy between the hydroxyl-functionalized ball-milled ZVI/Fe3O4 composite and Na2EDTA complexation

Chunfeng Wang,Yufan Wu,Tongxu Qu,Shasha Liu,Yunqing Pi,Jinyou Shen

The application of zero-valent iron (ZVI) for Cr(VI) removal often presents limitations due to its easy passivation. In this study, a column packed with hydroxyl-functionalized ball-milled ZVI/Fe 3 O 4 (HFB-ZVI/Fe 3 O 4 ) composite, assisted with Na 2 EDTA complexation, was developed to achieve sustainable treatment of Cr(VI)-containing wastewater. The results showed that at influent Cr(VI) concentration of as high as 50 mg/L, effluent Cr(VI) concentration below 0.5 mg/L was sustained for bed volume of as high as 1271 BV along with 2 g/L Na 2 EDTA concentration. Through the hydroxyl-functionalized treatment, FeOOH coating containing surface-adhering Fe(II) on the composite surface can be formed. Hydrolysis and auto-reduction of Fe(II)/Fe(III) species caused proton accumulation, resulting in remarkable attraction of anionic Cr(VI) via electrostatic interaction and exchange. Therefore, the reduction of Cr(VI) to Cr(III) was considerably enhanced. On the other hand, Na 2 EDTA complexation suppressed the growth of passivation layer and generated fresh corrosion products, thereby providing additional reactive sites for Cr(VI) removal. Additionally, Na 2 EDTA recovery and spent column regeneration were successfully proven. The remarkable effectiveness of Cr(VI) removal from actual electroplating wastewater confirmed the potential of the HFB-ZVI/Fe 3 O 4 composite-packed column and Na 2 EDTA assistance-coordinated system in full-scale application.

A cellulose-based adsorbent with pendant groups of quaternary ammonium and amino for enhanced capture of aqueous Cr(VI)

Xingtang Liang,Bin Liang,Jinyu Wei,Shuming Zhong,Ruirui Zhang,Yanzhen Yin,Yanjuan Zhang,Huayu Hu,Zuqiang Huang

As a promising candidate of Cr(VI) decontamination, cellulose is limited in the Cr(VI) uptake due to its poor accessibility. Herein, We describe the synthesis of a novel cellulose-based adsorbent (PQC, where P and QC designate the polyethylenimine and quaternized cellulose, respectively) with functional groups of quaternary ammonium and amino for enhanced capture of Cr(VI) from water. For preparing PQC, cellulose is first quaternized homogeneously, followed by grafting and/or cross-linking with polyethylenimine in the presence of epichlorohydrin. The PQC follows the Langmuir isotherm and presents a maximum Cr(VI) uptake capacity of 490.3 mg/g at 30 °C and initial pH about 2.0, much higher than many other reported cellulose-based adsorbents. The adsorption of PQC is spontaneous and endothermic, which follows the pseudo-second-order kinetic model and achieves the equilibrium after contacting about 50 min. Furthermore, the PQC, with favorable reusability, can work well in a high coexisting anion concentration. These excellent absorption performances are attributed to its physicochemical properties such as the robust porous structure and high density of functional groups including quaternary ammonium, amino and hydroxyl, which improve the availability to capture or reduce Cr(VI). This work demonstrates the significant potential of cellulose-based adsorbent for remediating aqueous Cr(VI).

Fe/C materials prepared by one-step calcination of acidified municipal sludge and their excellent adsorption of Cr(VI)

Ruixue Shi,Tianbao Liu,Jing Lu,Xiangjing Liang,Andrei Ivanets,Junqin Yao,Xintai Su

Biochar derived from municipal sludge can be applied to adsorption. But it usually requires activation and pickling due to the generation of impurities such as metal oxide particles, which is uneconomical. Here, a facile strategy, acidification-one-step calcination, was developed and sludge-based Fe–C materials with good Cr(VI) removal effect were obtained by regulating the amount of hydrochloric acid . The results show that the adsorption capacity of Fe/C-5 (the best sample) for Cr(VI) was 150.84 mg g −1 . According to the Langmuir isotherm and pseudo-second-order kinetic model, the removal of Cr(VI) by Fe/C-5 is spontaneous and endothermic chemisorption process. In addition, Fe/C-5 has good ability to remove Cr(VI) under the interference of coexisting ions, and has good cycle stability. The removal of Cr(VI) by Fe/C-5 is considered to be synergistic process of adsorption and reduction. The Fe atoms were highly dispersed in Fe/C-5 and tightly bonded with C atoms, which not only strengthened the Cr(VI) adsorption by electrostatic attraction, but also activated the C atoms in the biochar material, so that the C atoms can reduce Cr(VI) to Cr(III) under acidic conditions. This may be due to the fact that acid pretreatment converted the iron in municipal sludge in the form of Fe–O/OH to free Fe 3+ and entered the C lattice during the calcination process. In this work, Fe–C materials with excellent Cr(VI) adsorption capacity were prepared by one-step calcination method, which has important reference significance for the resource utilization of municipal sludge.

A Novel Graphene Oxide Functionalized Hydrocalumite/Cellulose Composite for the Selective and Simultaneous Removal of Tetracycline and Cr(VI)

Soodamani Periyasamy,Jun Hou,Natrayasamy Visawanathan,Yang Li,Zijun Yang,Guoxiang You

Tetracycline antibiotic and hexavalent chromium removal from the wastewater is crucial for preventing future environmental trouble. This study aimed to develop an eco-friendly biocomposite made from an enhanced graphene oxide-functionalized hydrocalumite/cellulose composite for co-adsorbative removal of TC antibiotic and toxic Cr(VI). The synthesized GO@CellHC composite was characterized using various microscopic techniques. The GO@CellHC composite possessed the superior removal for TC and Cr(VI), achieving 27.4 and 42.6 mg/g in single systems, and 24.8 and 39.6 mg/g in binary systems, all within 40 minutes. In pH results, the maximum removal was observed at an acidic pH of 3 for Cr(VI) and 5 for TC, respectively. The co-ions results demonstrated that the composite efficiently removed both pollutants, except in the presence of PO 4 3- and CO 3 2- . The Langmuir isotherm indicated the strongest adsorption capacity and favored both systems. Thermodynamic studies revealed that the adsorption of both systems onto the GO@CellHC composite removes TC and Cr(VI) by endothermic and spontaneous system. Kinetic results demonstrated that TC adsorption shows a higher rate constant k 2 (single: 0.01676 min -1 and binary: 0.0138 min -1 ) compared to Cr(VI) adsorption (single: 0.01478 min -1 and binary: 0.01007 min -1 ). The GO@CellHC composite retained more than 80 % after three cycles, and field results suggesting that the biocomposite can be utilized for the removal of binary water pollutants.

Nano zero-valent iron supported by macroporous styrene ion exchange resin for enhanced Cr(VI) removal from aqueous solution

Wei Gao,Dengjie Zhong,Yunlan Xu,Han Luo,Sijing Zeng

Microwave-assisted synthesis of Zr-based metal-organic polyhedron: Serving as efficient visible-light photocatalyst for Cr(VI) reduction

Yu-Teng Zhang,Juan Zhu,Zhao-Yang Liu,Shuang-Bao Li,He Huang,Bao-Xu Jiang

For the first time, a microwave-assisted synthesis approach was used to prepare an amino-functionalized Zr-based metal–organic polyhedron (denoted as MW-ZrT-1-NH 2 ). The reaction time was shortened from 12 h to 2 min when compared to the traditional solvothermal method, resulting in crystalline products with good yield and purity. Herein, MW-ZrT-1-NH 2 was utilized as a photocatalyst for the catalytic reduction of Cr(VI) under visible-light irradiation. The results revealed that MW-ZrT-1-NH 2 exhibits better photocatalytic performance for Cr(VI) reduction. Furthermore, a plausible photocatalytic mechanism was proposed via electron spin resonance (ESR) measurements and radical trapping tests.

Efficient adsorption H3AsO4 and Cr(VI) from strongly acidic solutions by La-Zr bimetallic MOFs: Crystallinity role and mechanism

Caiyun Han,Jing Xie,Xize Min

Due to the non-degradable of heavy metal, adsorption has been extensively applied to abatement it. Most studies were focused on uptake metal ions via electrostatic attraction and ion exchange, and load molecule H 3 AsO 4 from strongly acidic wastewater was still challenging. To solve the problem, bimetallic La–Zr MOFs was facilely fabricated in this work, and the fcu topology structure of La-Zr MOFs was remained well under the investigate crystallization time and crystallization temperature. However, the crystallinity of the obtained La-Zr MOFs was influenced by the synthesized factors. The obtained La–Zr MOFs was employed as adsorbent to removal Cr(VI) and As(V), and the performance was evaluated by the batch experiment. The result indicated that the adsorption performance of Cr(VI) and As(V) was positively correlated with the crystallinity , and the optimal sample was 1LaUN 12 . From the XPS characterization, it was found that H 3 AsO 4 was successfully uptake over 1LaUN 12 surface, and the maximum monolayer adsorption capacity was 83.40 mgH 3 AsO 4 /g via ligand exchange and coordination reactions with La−OH and Zr−OH. In addition, the sample 1LaUN 12 also exhibited the excellent Cr(VI) load performance, and the maximum monolayer adsorption capacity of Cr(VI) was 222.5 mg/g. Above 40% Cr(VI) was reduced to Cr(III) by amino groups, and immobilized over the surface of 1LaUN 12 . Eventually, 1LaUN 12 displayed a good structural stability in the acidic medium, which was in favor of removing Cr(VI) and As(V) efficiently from strongly acidic solutions.