Search

Wastewater containing organic dyes has become one of the important challenges in water treatment due to its high salt content and resistance to natural degradation. In this work, a novelty adsorbent, PEI-SMA, was prepared by grafting polyethyleneimine (PEI) onto styrene-maleic anhydride copolymer (SMA) through an amidation reaction. The various factors, such as pH, adsorbent dosage, contact time, dye concentration, and temperature, which may affect the adsorption of PEI-SMA for Reactive Black 5 (RB5), were systematically investigated by static adsorption experiments. The adsorption process of PEI-SMA for RB5 was more consistent with the Langmuir isotherm model and the pseudo-second-order model, suggesting a single-layer chemisorption. PEI-SMA exhibits excellent adsorption performance for RB5 dye, with a maximum adsorption capacity of 1749.19 mg g–1 at pH = 2. Additionally, PEI-SMA exhibited highly efficient RB5 competitive adsorption against coexisting Cl− and SO42− ions and cationic dyes. The adsorption mechanism was explored, and it can be explained as the synergistic effect of electrostatic interaction, hydrogen bonding and π–π interaction. This study demonstrates that PEI-SMA could act as a high performance and promising candidate for the effective adsorption of anionic dyes from aqueous solutions. [ABSTRACT FROM AUTHOR]

Wastewater containing dyes is frequently discharged by industrial processes and needs separation and recycling. To solve this problem, it is important to research and develop environmentally friendly, efficient adsorbent materials for pollutant separation and recovery. In this study, a poly(PEI‐catechol‐tetraethylenepentamine) (PPCT) adsorbent was synthesized using a simple catecholamine reaction. This adsorbent exhibited high adsorption capacity and excellent removal efficiency for Reactive Red 195 (RR‐195) in wastewater. The material was characterized using SEM, FT‐IR, TGA, EA, and XPS. Its performance was optimized by varying the type of polyethyleneimine and the amount added during the preparation process. The effects of temperature, pH, contact time, and salt concentration on the adsorption were systematically investigated. Additionally, the experimental data showed consistency with both the Langmuir and pseudo‐second‐order kinetic models, simultaneously. The maximum adsorption capacity can reach 1754 mg g−1 at 303 K, with a retention rate of 86.6% after two cycles. The removal rate exceeds 98% at a concentration of 400 mg g−1 or lower. Additionally, the protonated amine group in PPCT carries a positive charge under acidic conditions, enabling selective adsorption of the anionic dye RR‐195. Consequently, PPCT exhibits an excellent adsorption effect on RR‐195 and holds promising applications in pollutant removal. [ABSTRACT FROM AUTHOR]

In this work, a new AC@Catechol/PEI adsorbent was prepared via the copolymerization of catechol and polyethyleneimine (PEI) onto pretreated commercial activated carbon (AC). It achieved a high adsorption capacity of 411.52 mg/g for the anionic dye Congo red (CR), which was approximately 7 times that of pretreated AC without modification. In bath adsorption experiment, 1 g of adsorbent was used to treat 4 L of 100 mg/L CR solution, resulting in 98.5% CR removal. In addition, the prepared AC@Catechol/PEI adsorbent exhibited highly efficient CR competitive adsorption against SO42− ions and cationic malachite green dye. The adsorption mechanism was mainly attributed to electrostatic interactions, hydrogen bonding, and π–π stacking. Catecholamine modification greatly improved the adsorption capacity and adsorption selectivity of commercial AC for CR dyes. This low‐cost adsorbent may have broad prospects for the removal of anionic dyes in wastewater. [ABSTRACT FROM AUTHOR]

• A cost-effective tannin-polyethyleneimine polymer adsorbent was prepared. • The prepared TA-PEI.3.1 shows high Cr(VI) removal capacity of 707.96 mg/g. • The adsorbent displays a fast removal ability of 554.94 mg/g within 15 min. • 1 g of TA-PEI.3.1 adsorbent can treat 10 mg/L Cr(VI) solution 30 L to 40 L. A new catecholamine polymer, tannin-polyethyleneimine (TA-PEI) was fabricated via mussel-inspired polymerization for highly efficient hexavalent chromium (Cr(VI)) adsorption. The TA-PEI adsorbent was prepared with a mass ratio of TA to PEI of 3:1. This adsorbent had an ultra-high Cr(VI) removal capacity because of its amines and phenolic hydroxyl groups, with values reaching 707.96 mg/g under 308 K, which is higher than that of most PEI-based and TA-bearing adsorbents. The developed adsorbent also achieved rapid Cr(VI) adsorption, with adsorption capacity values reaching 554.94 mg/g in 15 min. Further, it displayed excellent chemical reduction ability when converting Cr(VI) to low toxicity Cr(III), as well as its good adsorption selectivity of Cr(VI) in a solution bearing coexisting ions. In a continuous adsorption experiment, the adsorbent exhibited a Cr(VI) solution treatment capacity of up to 30 L/g with a Cr(VI) concentration of 10 ppm. With its high adsorption capacity and rapid adsorption rate, this low cost and easily prepared adsorbent may have widespread potential for Cr(VI) removal and enrichment. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the dye sludge which was prepared from Congo red solution by flocculation method was further modified by catechol and 1, 6-hexanediamine before usage to remove Cr(VI) ions. This particles were characterized by multiple testing means and the effects of removal, such as contact time, pH value, initial concentration, and temperature, were studied by batch mode. The maximum adsorption capacity of Cr(VI) was 282.48 mg/g and the whole process was spontaneous and endothermic. Hopefully, with the advantages of facile preparation and high adsorption capacity, the dye-based adsorbent has broad application prospects in the field of wastewater treatment. [ABSTRACT FROM AUTHOR]

• A novel adsorbent material was simply fabricated for Cr (VI) removal. • The as-prepared PPTD exhibits a rapid adsorption rate for Cr (VI) at low concentrations. • The PPTD adsorbent presents a high adsorption capacity for Cr (VI). • The PPTD adsorbent manifests excellent adsorption selectivity for Cr (VI). Background: In order to remedy the pollution of chromium(VI), it is of great significance to develop high-efficiency adsorbents. Methods: Heren, excellent adsorbents poly(polyethyleneimine-tannin-diethylenetriamine) (PPTD) were synthesized using a simple route and utilized for the removal of Cr (VI) from aqueous solutions. The effect of various factors on the adsorption behavior of PPTD was studied, such as polyethyleneimine content, temperature, initial pH, initial concentration, adsorbent dosage, contact time, and foreign ions. The optimized experiments were performed under the conditions of polyethyleneimine content (35%), temperature (30 °C), initial pH (2), initial concentration (200 mg L −1), and contact time (24 h) using 25 mg PPTD to remove Cr(VI) for 100 mL solution. Significant Findings: The results not only showed rapid removal efficiency which is close to 100% at low concentrations (20∼120 mg L −1), but also exhibited favorable selectivity for Cr (VI) even in the presence of coexisting ions (such as Cl−, Cd (II), and Cu (II)). Its maximum capacity reached the value of 757.6 mg g −1 at 30 °C, which was close to the experiment data (751.6 mg g −1). Besides, the adsorption behavior of Cr (VI) can be described by the pseudo-second-order kinetic model and the Langmuir isothermal model. Following satisfactory fitting with the Langmuir isotherm model. [Display omitted] [ABSTRACT FROM AUTHOR]

Synthesis of covalently linked porous polymers with high surface area and larger pore volume for two or more task‐specific functionalities is always a big challenge. In this article, the facile Friedel–Crafts reaction is employed to construct the hierarchical hybrid porous polymers (HPPs) from tetraphenyladamantane and octavinylsilsesquioxane. The resulting polymers, HPP‐1 to HPP‐3, possessed the surface areas from 1356 to 1511 m2 g−1, and the pore volumes from 2.05 to 2.67 cm3 g−1. All these polymers feature micropores, mesopores, and macropores in nature. The resultant polymers exhibit high CO2 adsorption capacity up to 2.0 mmol g−1 (8.82 wt %), at 273 K, 1.0 bar, and the maximum Rhodamine B (RB) sorption capacity of 653.6 mg g−1. To illustrate the adsorption process, the effects of factors, contact time, initial concentration, temperature, and pH value on the adsorption capacity of RB were studied. The adsorption equilibrium data displayed a better fitting to the Langmuir isotherm model than the Freundlich model and the adsorption kinetics fitted well with the pseudo‐second‐order kinetic model. The recycle experiments displayed that the capacity recovery was still higher than 95% after four cycles. Theses polymers are promising to be the adsorbents for capturing CO2 and removing RB. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 136, 48572. [ABSTRACT FROM AUTHOR]

Antibacterial β-cyclodextrin-based nanoparticles (E - β-CDN) were first fabricated through one-pot method, which exhibited superfast, broad-spectrum adsorption towards pollutants. The current water treatment technology is still based on low energy efficient processes due to the complex composition of wastewater. To achieve high energy efficiency, many micro-porous materials with complex functional groups have been fabricated because of their high pollutant adsorption capabilities. In this work, antibacterial β-cyclodextrin-based nanoparticles (E-β-CDN) were prepared via one-pot method to explore their adsorption performance to pollutants in wastewater. The resulting nanoparticles exhibited superfast adsorption kinetics to pollutants with removal efficiency of over 95% within 10 s. The nanoparticles also presented broad-spectrum adsorption to organic pollutants and heavy metal ions, and their maximum adsorption capacity was 3289.6 mg g−1 towards methyl orange (MO) and 970.8 mg g−1 towards Pb(II), much higher than that of many other adsorbents. Easy cyclic adsorption-desorption was another distinguishing feature of the nanoparticles, whose removal efficiency to these pollutants hardly varied after 10 cycles of regeneration. Interestingly, the resulting nanoparticles showed prominent antibacterial activity of 99.99% bacterial inhibitive rate against both gram-negative bacteria Escherichia coli (E. coli) and gram-positive bacteria Staphylococcus aureus (S. aureus). These results suggest that the resulting nanoparticles have great potential in the purification of the wastewater. [ABSTRACT FROM AUTHOR]

Flower-like hierarchical porous MgO was obtained via a modified gas-liquid interfacial reaction. These resulting MgO powders showed superb adsorption properties, with a notable adsorption capacity of 5051 mg g−1 for Congo red. • Flower-like porous MgO was obtained via a gas-liquid interfacial reaction. • This porous MgO displayed an ultra-high adsorption capacity for Congo red (5051 mg g−1). • The possible formation mechanism of basic magnesium carbonate microspheres using ammonium carbonate and aqueous ammonia has been proposed. The flower-like porous MgO was obtained via a interfacial reaction following by further calcination. In the interfacial reaction, flower-like basic magnesium carbonate microspheres (precursor) were prepared by using magnesium chloride hexahydrate, ammonium carbonate, aqueous ammonia and water as starting materials. The formation mechanism of these basic magnesium carbonate microspheres has been proposed. The as-obtained hierarchical porous MgO showed an ultra-high adsorption capacity for Congo red (5051 mg g−1). This study provides a convenient strategy for synthesizing hierarchical porous MgO microspheres with great adsorption ability. [ABSTRACT FROM AUTHOR]

The dyeing wastewater contains amounts of refractory organic compounds, and severely endangers the ecosystem and human health. To alleviate this problem, in this study, the low-cost broad-spectrum nano-adsorbent (denoted as CD/CA -g- CS) with strong antibacterial activity has been synthesized by chemical binding of β -cyclodextrin (β -CD) with chitosan (CS) and citric acid (CA) for high-efficient dyes scavenger. Taking advantage of the extraordinary water insolubility, porous nature and abundant surface groups, the synthesized CD/CA -g- CS outperforms the previously reported adsorbents in terms of adsorption performance. The CD/CA -g- CS exhibits ultrahigh adsorption capacities of 801.66, 770.50 and 946.66 mg/g, respectively mg/g for the cationic dyes of malachite green (MG), basic red (BR) and methylene blue (MB), respectively, while 389.64, 619.60 and 429.22 mg/g for the anionic dyes of acid blue (AB), acid red (AR) and acid yellow (AY), respectively. The chemical monolayer absorption is further demonstrated by the analysis based on the pseudo-second-order adsorption kinetics and Langmuir isotherm models. The regenerable CD/CA -g- CS not only performs well in one-step removal of the mixed dyes in the simulated sewage, but also exhibits superior performance in purifying real industrial wastewater. Moreover, CD/CA- g -CS endowed with antibacterial activity leads to an inhibition rate of over 99.99 % for E. coli. The newly developed CD/CA -g- CS adsorbents are highly promising for high-efficient dyeing wastewater remediation. [Display omitted] ● The low-cost yet high-efficiency CD/CA- g -CS is developed to treat dyeing effluents. ● Diverse active groups endow CD/CA- g -CS with broad-spectrum adsorption capability. ● Involvement of chitosan endows CD/CA- g -CS with superior antibacterial property. ● Regeneration ability promotes at least five-cycle-use of CD/CA -g- CS. ● The CD/CA- g -CS adsorbent is valid in both static and dynamic real sewage remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-cost cyclodextrin-based nanocubes with controllable morphology are prepared. • cl-CD@CA shows superior adsorption capacity for cationic dyes and heavy metal ions. • cl-CD@CA displays high performance in real industrial effluents remediation tests. Water contamination caused by the discharge of textile dyeing wastewater is a thorny issue that cannot be ignored nowadays. In this work, eco-friendly β -cyclodextrin based nanocubes (cl-CD@CA) with low cost and exceptional adsorption capacity were fabricated by a facile method to treat textile dyeing effluents. The prepared adsorbents showed high water insolubility and extraordinary adsorption capacity towards methylene blue, crystal violet, neutral red, Pb2+, Cd2+, and Sb3+ ions with corresponding maximum adsorption capacity of 1523.6, 1012.2, 419.2, 758.7, 525.3, and 398.1 mg/g, much higher than that of some other adsorbents. The adsorption kinetic and isotherm studies indicated that the adsorption process of cl-CD@CA fit pseudo-second-order adsorption kinetic model and Langmuir isotherm model well, manifesting its monolayer chemisorption. Remarkably, the cl-CD@CA, presenting high selective adsorption toward cationic rather than anionic dyes, was potential for mixed dye separation. Moreover, the cl-CD@CA maintained excellent recyclability after 10 regeneration cycles. Excitingly, cl-CD@CA exhibited high static and dynamic adsorption capacity for actual dyeing wastewater, with a 79.3 % reduction in COD and 95 %, 29 % and 16 % concentration reduction of Pb2+, Cd2+ and Sb3+. Therefore, the newly developed lost-cost yet high-efficiency cl-CD@CA can serve as promising adsorbents to alleviate the water pollution caused by dyeing wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Water-insoluble cyclodextrin-based nanocubes with uniform morphology were developed for the first time. • CL-CD@PNC displayed superior adsorption capacity and recyclability. • Real water tests verified the outstanding adsorption performance of CL-CD@PNC. Cyclodextrin (CD), as a naturally green starch derivative, is a promising candidate for water treatment through adsorption. Unfortunately, the soluble nature of CD in water limits its application greatly. In this work, a water-insoluble CD-based nanocube (CL-CD@PNC) with high adsorption performance toward dissolved pollutants is first developed through a facile two-step route. The prepared CL-CD@PNC has high water stability and well-defined cubic morphology with a porous structure. Additionally, the CL-CD@PNC nanocubes present prominent adsorption performance with the maximum adsorption capacities of 2173.21, 998.54, and 966.06 mg g−1 towards methylene blue (MB), bisphenol A (BPA), and Pb(Ⅱ), respectively, which is much higher than those of many other adsorbents. The adsorption equilibrium can be achieved within 10 and 30 s for MB and Pb(Ⅱ) adsorption, respectively, indicating the ultrafast adsorption rate. These adsorption processes are ascribed to the pseudo-second-order adsorption kinetics and Langmuir isotherm model, signifying the chemical and monolayer adsorption process. Moreover, the removal efficiency of the CL-CD@PNC nanocubes towards three different pollutants remains over 85% even after 10 recycles of regeneration. The superior adsorption performance of our CL-CD@PNC is attributed to the synergetic effect of host–guest interaction, electrostatic adsorption, hydrogen bond interaction, and chelation. More importantly, the applicability of CL-CD@PNC is successfully demonstrated under real industrial wastewater conditions. This work provides a promising strategy to prepare the water-insoluble CD-based adsorbent with a regular cubic structure, which can be potentially applied in the practical applications of industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Few-layer Ti 2 CT x was synthesized by selective etching and ultrasonic exfoliation. • Ti 2 CT x showed excellent adsorption selectivity towards methylene blue removal. • The maximum adsorption capacity could reach as high as 2460.9 mg g−1. • The primary adsorption mechanism was associated with electrostatic interaction. Exploring versatile materials that efficiently adsorb pollutants from wastewater is of critical importance for environmental remediation. As an emerging 2D material, MXene features a hydrophilic surface with abundant oxygen-containing groups that render a negatively charged surface, implying its great potential for removing cationic pollutants from wastewater. Given its remarkable properties, a novel Ti 2 CT x MXene as an adsorbent is synthesized through selective etching of Al layer from Ti 2 AlC and then ultrasonic exfoliation. The adsorption studies indicate that Ti 2 CT x exhibits highly efficient methylene blue (MB, cationic dye) removal performance, the maximum adsorption capacity can reach as high as 2460.9 mg g−1, which is considerably higher than the values of graphene (83.2 mg g−1) and anionic dye removal (methyl orange, 122.6 mg g−1). Furthermore, the adsorption behavior fits well with the pseudo-second-order kinetic and Langmuir isotherm models, and thermodynamic analysis indicates that the adsorption is spontaneous and endothermic. Based on scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra analysis, the principal adsorption mechanism is related to the electrostatic interaction between Ti 2 CT x and MB molecules. Meanwhile, the result is also confirmed by adsorption experiments at different pH values and background ions. This work shows that the MXene family materials can be applied as high efficiency adsorbent for removing cationic dyes from wastewater. [ABSTRACT FROM AUTHOR]

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 (Cu2+, Fe3+, Mn2+), and pH value (2–7). The adsorption-reduction process followed the Langmuir isotherm model (R2 = 0.9994) and fitted well with the pseudo-second-order kinetic model (R2 = 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. Image 1 • Hollow globular Cr(VI)-adsorbents were fabricated via assembly to polymerization. • Reduction of Cr(VI) to nontoxic Cr(III) exists in PVA@PTHA adsorption procedure. • Approximately 100% of removal efficiency is detected at initial Cr(VI) concentration below 160 mg/L. • Adsorption-reduction of Cr(VI) over PVA@PTHA is little affected by foreign ions. [ABSTRACT FROM AUTHOR]