查找使用阿拉丁产品的科研文献

Enhanced adsorptive removal of Cr(VI) in aqueous solution by polyethyleneimine modified palygorskite

Jiahong Wang,Tongtong Sun,Atif Saleem,Yao Chen

Polyethyleneimine (PEI) modified palygorskite (Pal) was used for the adsorption of Cr(VI) in aqueous solution. The absorbent was characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). Characterized results confirmed that the Pal has been successfully modified by PEI. The modification of PEI increased the Cr(VI) adsorption performance of the Pal by the adsorption combined reduction mechanism, and amino groups of the adsorbent play the main role in the enhanced Cr(VI) adsorption. The maximum adsorption capacity was 51.10 mg·g −1 at pH 4.0 and 25 °C. The adsorption kinetics of Cr(VI) on the adsorbent conforms to the Langmuir isotherm model. The maximum adsorption occurs at pH 3, and then the adsorption capacity of PEI-Pal was decreased with the increase of pH values. The adsorption kinetics of Cr(VI) on PEI-Pal was modeled with pseudo-second-order model. The addition of Cl − , SO 4 2− and PO 4 3− reduced the Cr(VI) adsorption by competition with Cr(VI) for the active sites of PEI-Pal. The Cr(VI) saturated PEI-Pal can be regenerated in alkaline solution, and the adsorption capacity can still be maintained at 30.44 mg·g −1 after 4 cycles. The results demonstrate that PEI-Pal can be used as a potential adsorbent of Cr(VI) in aqueous solutions.

Removal of Cr(VI) from Aqueous Solution by Polypyrrole/Hollow Mesoporous Silica Particles

Linlin Du,Peng Gao,Yuanli Liu,Tsuyoshi Minami,Chuanbai Yu

The removal of Cr(VI) in wastewater plays an important role in human health and environment. In this work, polypyrrole/hollow mesoporous silica particle (PPy/HMSNs) adsorbents have been newly synthesized by in-situ polymerization, which prevent the aggregation of pyrrole in the process of polymerization and exhibit highly selective and powerful adsorption ability for Cr(VI). The adsorption process was in good agreement with the quasi-second-order kinetic model and the Langmuir isotherm model. And the maximum adsorption capacity of Cr(VI) was 322 mg/g at 25 °C. Moreover, the removal rate of Cr(VI) by PPy/HMSNs was ~100% in a number of binary systems, such as Cl−/Cr(VI), NO3−/Cr(VI), SO42−/Cr(VI), Zn2+/Cr(VI), Fe3+/Cr(VI), Sn4+/Cr(VI), and Cu2+/Cr(VI). Thus, the PPy/HMSNs adsorbents have great potential for the removal of Cr(VI) in wastewater.Keywords:polypyrrole/hollow mesoporous silica particle;chromium(Cr);adsorption

Humic acid modified nano-ferrous sulfide enhances the removal efficiency of Cr(VI)

Youru Yao,Na Mi,Cheng He,Huan He,Yong Zhang,Yongcai Zhang,Li Yin,Jing Li,Shaogui Yang,Shiyin Li,Lixiao Ni

The dissolved hexavalent chromium (Cr(VI)) in natural water system poses a significant risk for public health and the environment. Nanoscale ferrous sulfide (FeS) has been widely used to treat soils, sediments, groundwater, and natural waters contaminated with Cr(VI), but the reactivity of FeS can be significantly reduced due to its easy agglomeration and therefore decreased the remove rate of the dissolved Cr(VI). To overcome this problem, the present study used humic acid (HA) to modify FeS in order to reduce its agglomeration and increase stability. Results showed that the HA modified FeS (HA-FeS) had good stability and reduced FeS agglomeration. The hydrodynamic diameter of HA-FeS was between 235 and 241 nm, which was much smaller than that of the unmodified FeS. The maximum removal quantity of Cr(VI) by HA-FeS was 7.74 and 2.35 times higher that of HA and the unmodified FeS, respectively, and the maximum removal quantity of HA-FeS was 675.03 mg/g. Further, HA-FeS performed better efficiency in removing the dissolved Cr(VI) with high or low concentration. With an increasing concentration of Ca 2+ and Mg 2+ , the efficiency of HA-FeS to remove Cr(VI) showed a decreasing trend. The removal mechanism of Cr(VI) mainly relies on the reducibility of Fe 2+ and S 2− . XPS and XRD measurements further revealed that 95.03% of Cr(VI) was converted to Cr(III) (FeCr 2 O 4 , Cr(OH) 3 and Cr 2 O 3 ), and another 4.58% of Cr(VI) was adsorbed by HA-FeS. Therefore, this study demonstrated an efficient method to improve the nano-FeS stability and reactivity for the rapid repair of Cr(VI) contamination in natural water.

Adsorption of Cr (VI) onto Attapulgite/UiO-66-NH2 Composites from Aqueous Solution

Peiyi Bao,Haiying Du,Xiangning Xu,Junya Li,Yao Wu,Shaojiang Zhou,Lingyun Li,Ningfei Lei

Electrospun Cellulose Acetate/Polyethylenimine Porous Fibers toward Highly Efficient Removal of Cr(VI)

Dan Luo,Shao-zhong Hu,Ting Huang,Nan Zhang,Yan-zhou Lei,Yong Wang

The development of an efficient, economical, and environmentally friendly monolithic adsorbent for the removal of toxic hexavalent chromium Cr(VI) has invariably been a topic of great concern to researchers. In this paper, cellulose acetate (CA) and polyethylenimine (PEI) homogeneously blending porous fiber membranes with high porosity were successfully prepared by electrospinning, and PEI was further immobilized by cross-linking to form a stable biological adsorbent. The adsorption behavior and eliminating mechanism toward Cr(VI) by the CA-c-PEI fibrous membranes were comprehensively explored. The maximum adsorption capacity was up to 285.7 mg/g (25 °C), higher than most of the biomass-based adsorbents. Specifically, the concentration of Cr(VI) could be dramatically reduced from the initial 50 mg/L to 0.03 mg/L, much lower than the concentration standard for drinking water recommended by the World Health Organization. Even after being reused several times, the fibrous membrane still exhibited high removal efficiency.

Preparation of covalent triazine-based framework for efficient Cr(VI) removal from water

Shuangxi Zhou,Ziming Zhou,Donghai Zhu,Huanhuan Jiang,Yue Qi,Shiyi Wang,Ye Jia,Wei Wang

To overcome problems associated with heavy metal pollution, lots of new functional materials have been used. As potential emerging environmental materials, covalent triazine frameworks (CTFs) have received extensive attention because of their high nitrogen content and the feature of pre-design to obtain the required molecular framework for specific applications. In this study, three CTFs were synthesized by terephthalonitrile (TPA) with the catalyzer of ZnCl 2 under different temperatures from 300 °C to 500 °C. Preparation temperature significantly affected the adsorption kinetics and capacity of CTFs. The CTF prepared under 500 °C (CTF500) showed the highest Cr(VI) adsorption capacity of 97.84 mg g −1 . The CTF500 was characterized with three different types of N, including pyrrolic N, pyridinic N, and quaternary N, thus providing support for the efficient adsorption of Cr(VI) from water. The mechanism of Cr(VI) removal was verified by a strong ion exchange interaction driving with the structure of quaternary N on CTF500. In addition, CTF500 also showed a stable Cr(VI) removal rate under a high ionic strength surrounding. In this study, CTFs with pre-designed functional groups could efficiently remove Cr(VI) by controlling their synthesis progress and showed great potential in future environmental applications.

Effective removal of Cr(VI) from aqueous solution by biochar supported manganese sulfide

Shiqiu Zhang,Haiqing Zhang,Fang Liu,Fan Yang,Shengnan Zhou,Kui Zheng,Chunli Chu,Le Liu,Meiting Ju

In order to remove hexavalent chromium (Cr(VI)) efficiently and simplify the adsorbent preparation process, we employed a single step method to prepare a new biochar supported manganese sulfide material. The nanoscale MnS particles were highly soldered on the biochar support surface, and this adsorbent displayed the effective removal of Cr(VI) (98.15 mg L−1) via synergistic effect between adsorption and reduction/precipitation under weak acid conditions (pH = 5.0–6.0). The adsorption kinetic data were described well by the pseudo second-order kinetic model, suggesting that the reaction process was a chemisorption process. The adsorption isotherm data were described well by the Redlich–Peterson model, further suggesting that this reaction was a hybrid chemical reaction-sorption process. In addition, the Dubinin–Radushkevich isotherm model with 8.28, 8.57, and 12.91 kJ mol−1 adsorption energy also suggests that it was a chemisorption process. The simple and eco-friendly preparation process, low-cost, and the high removal efficiency could make it a promising material for the purification of Cr(VI)-contaminated wastewater.

Facile synthesis of hollow globular Cr(VI)-adsorbents inspired from assembly to polymerization

Song Gao,Qinze Liu,Qiang Liu,Chengbing Yuan,Tingting Gao,Jinshui Yao

In this work, hollow globular Cr(VI)-adsorbents were successively fabricated via the assembly of tannic acid (TA) and 1, 6-hexanediamine (HA) converting to polymerization using polyvinyl alcohol (PVA) as precursor. PVA@poly(tannic acid - 1, 6-hexanediamine) (PVA@PTHA) with hollow structure can chelate Cr on their bodies accompanying of reduction of Cr(VI) to Cr(III) caused by phenolic hydroxyl groups, which is proved by means of TEM , XPS , SEM and EDX, etc . Many factors affecting the adsorption of Cr(VI) were studied systematically, i.e. , initial Cr(VI) concentration (20–260 mg/L), contact time (0–48 h), foreign ions (Cu 2+ , Fe 3+ , Mn 2+ ), and pH value (2–7). The adsorption-reduction process followed the Langmuir isotherm model (R 2  = 0.9994) and fitted well with the pseudo-second-order kinetic model (R 2  = 0.9984). Besides, the removal capabilities of PVA@PTHA for Cr(VI) were affected insignificantly by nitrate ion (NO 3 − ) or sulfate ion (SO 4 2− ) as a competitive ion. In brief, PVA@PTHA is low-cost green adsorbent with the maximum adsorption capacity of 434.0 mg/g for Cr(VI)-sewage treatment.

Reusable and removable PmPD/PVA membrane for effective Cr(VI) adsorption and reduction

Yao Chen,Shihao Xu,Shuai Han,Suyun Chu,Liang Yang,Changlong Jiang

Poly(m-phenylenediamine) (PmPD) is an efficient material for the adsorption of Cr(VI). However, it is facile to aggregate in water, which reduces its adsorption capacity, and it is not facile to be separated from water. Hence, magnetic or membrane structures by compositing PmPD with other functional materials are usually synthesized to solve the above problems. Here, we utilized polyvinyl alcohol (PVA) chains to obtain a dense network structure, which embedded and constrained PmPD into the network to form a membrane. PmPD constrained in the membrane existed stably and was facilely separated from water due to the large size of the membrane. Meanwhile, the PmPD/PVA membranes showed good mechanical properties and combined both the extraordinary adsorption capacity and reusability. In this study, the maximum Cr(VI) adsorption capacity of the composite membrane structures was 498.87 mg g−1 at room temperature. The adsorption and removal mechanism can be explained by the fact that the protonated imine units adsorb Cr(VI) via electrostatic attraction; following this, Cr(VI) changed to Cr(III) by reduction and chelated on the imine units. This study demonstrated that the PmPD/PVA membrane has a great potential for the separation of Cr(VI) from wastewater due to its low-cost and high adsorption capacity.

Photochemical Formation Process of Schwertmannite on Montmorillonite and Corresponding Cr(VI) Adsorption Capacity

Zhipeng Shu,Lihu Liu,Guohong Qiu,Xiong Yang,Mingzhe Zhang,Wenfeng Tan,Chengshuai Liu,Fei Wu

The formation and transformation of schwertmannite affect the migration, conversion, and toxicity of chromium (Cr) in soils and sediments. Schwertmannite could be obtained from the oxidation of Fe(II) by hydroxyl radicals (OH•) and superoxide radicals (O2•–) generated from the photolysis of NO3– under acidic and sulfate-rich conditions. As one of the most abundant components, montmorillonite is widely distributed in soils and sediments. However, the effect of montmorillonite on the photochemical formation process and corresponding Cr adsorption behaviors of schwertmannite remains elusive. This study indicates that schwertmannite could be formed on the montmorillonite surface during the photocatalytic oxidation of dissolved Fe(II). The formation rate, particle size, and crystallinity degree of schwertmannite formed on montmorillonite surface increased with increasing FeSO4 concentration (1.0–5.0 mmol L–1). The presence of montmorillonite led to a decrease in the particle size of schwertmannite. When the initial concentration of Fe(II) was 5.0 mmol L–1, the specific surface area of schwertmannite–montmorillonite aggregates reached 243.3 m2 g–1, which was remarkably larger than that of single-phase schwertmannite (24.6 m2 g–1) and montmorillonite (138.1 m2 g–1). The schwertmannite–montmorillonite aggregates showed a higher adsorption capacity for Cr(VI) (97.4 mg Cr g–1 Fe) than single-phase schwertmannite (72.9 mg Cr g–1 Fe). This work reveals the possible formation pathway and Cr adsorption behavior of schwertmannite on the surface of montmorillonite in waters and soils.

A novel tetraethylenepentamine crosslinked chitosan oligosaccharide hydrogel for total adsorption of Cr(VI)

Jinfeng Mei,Hui Zhang,Zhongyu Li,Hongxiang Ou

A kind of water-soluble chitosan, chitosan oligosaccharide, was used to synthesize a crosslinking hydrogel using a simple method, and the outstanding adsorption property of the hydrogel for Cr(VI) was investigated. The three-dimensional structure of the synthetic material was analyzed by means of 13 C solid state nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) measurements. The hydrogel also exhibited high thermal stability and mechanical strength. Its adsorption capacity for Cr(VI) reached 148.1 ± 2.4 mg/g with a fast adsorption rate. Pseudo-second-order kinetic model and Langmuir isotherm well described the adsorption process. Notably, the hydrogel still showed 100% removal efficiency for Cr(VI) at low concentration (0.02–1 mg/L) in the detectable range. The simple preparation process, high mechanical strength and excellent adsorption property indicate that the hydrogel has great potential for the removal of Cr(VI) ions from water and wastewater.

Structure-enhanced removal of Cr(VI) in aqueous solutions using MoS2 ultrathin nanosheets

Huating Sun,Tianxing Wu,Yunxia Zhang,Dickon H. L. Ng,Guozhong Wang

Molybdenum disulfide (MoS2) was successfully synthesized via a facile one-step hydrothermal method without addition of templates or surfactants. The obtained MoS2 product was characterized via various techniques including FESEM, HRTEM, XRD, BET and XPS analyses. Their application in capturing Cr(VI) ions in water was investigated. The results showed that the MoS2 nanosheets were ultrathin with a thickness of 5–10 nm and had a uniform lateral size of 100–200 nm. Impressively, these MoS2 nanosheets not only possessed enlarged interlayer spacing, but also had multiple defects on the basal planes, which were proved to be crucial in the removal of Cr(VI). The kinetics of chromium adsorption was found to follow the pseudo-second-order rate equation and the adsorption isotherm data were well fitted to the Langmuir model with a chromium in-take capacity of about 84.03 mg g−1. This structure-enhanced removal was likely related to the synergism of adsorption and reduction, in which the anionic Cr(VI) was adsorbed on the surface of D-MoS2via electrostatic interaction. At the same time, some fraction of the adsorbed Cr(VI) was reduced to low toxic Cr(III) and the generated Cr(III) species were adsorbed by the adsorbent. More significantly, the adsorption and reduction processes not only transferred the Cr(VI) from the aqueous environment to the surface of solid adsorbents but also alleviated the toxicity of Cr(VI). It was evident that this study may promote the application of other transition metal dichalcogenides in environmental remediation.