A novel hybrid of β-cyclodextrin grafted onto activated carbon for rapid adsorption of naphthalene from aqueous solution

A Review of Applications of Solid-State Nuclear Magnetic Resonance (ssNMR) for the Analysis of Cyclodextrin-Including Systems

Cyclodextrins, cyclic oligosaccharides composed of five or more α-D-glucopyranoside units linked by α-1,4 glycosidic bonds, are widely used both in their native forms as well as the components of more sophisticated materials. Over the last 30 years, solid-state nuclear magnetic resonance (ssNMR) has been used to characterize cyclodextrins (CDs) and CD-including systems, such as host-guest complexes or even more sophisticated macromolecules. In this review, the examples of such studies have been gathered and discussed. Due to the variety of possible ssNMR experiments, the most common approaches have been presented to provide the overview of the strategies employed to characterize those useful materials.

Adsorption of naphthalene polycyclic aromatic hydrocarbon from wastewater by a green magnetic composite based on chitosan and graphene oxide

A green magnetic composite mCS/GO was synthesized using water hyacinth extract, as a reducing agent, and proanthocyanidin, as a crosslinking agent, for the adsorption of naphthalene from effluents. The green composite was evaluated using different characterization techniques to determine its thermal (TG/DTG), structural (BET, XPS and FTIR), crystallographic (XRD), and textural (SEM) properties in natura and post-adsorption. The results obtained through a central composite design (CCD) experiment indicated that the initial concentration of NAP and the adsorbent dosage are significant for the adsorption capacity. The adsorption assays indicated that physisorption, through π-π and hydrophobic interactions, were the main mechanism involved in the NAP adsorption. However, the adjustment to the PSO and Freundlich models, obtained through kinetic and equilibrium studies, indicated that chemisorption also influences the adsorptive process. The thermodynamic study indicated physisorption as the mechanism responsible for the NAP adsorption. Also, the adsorbent has high affinity for the adsorbate and the process is spontaneous and endothermic. The maximum adsorption capacity (q_max) of the green mCS/GO was 334.37 mg g^-1 at 20 °C. Furthermore, the green mCS/GO was effectively regenerated with methanol and reused for five consecutive cycles, the percentage of NAP recovery went from approximately 91 to 75% after the fifth cycle. The green composite was also applied in the adsorption of NAP from river water samples, aiming to evaluate the feasibility of the method in real applications. The adsorption efficiency was approximately 70%. From what we know, this it is the first time that a green adsorbent was recycled after the polycyclic aromatic hydrocarbon (PAHs) adsorption process.

Efficient reclamation phosphate by alginate-g-BMOF using poly(N-isopropyl acrylamide-co-acrylamide) as coating for temperature-responsive slow-release P-fertilizer

Poly(N-isopropyl acrylamide) and its derived copolymer, as a temperature-responsive material, are widely used in the field of anticancer drug carrier. And it also plays an important role as carrier in slow-release fertilizer in recent years. In this paper, a smart poly(N-isopropyl acrylamide-co-acrylamide)-coated Alg-BMOF (PABMOF) was fabricated in ionic liquids microemulsion ([Bmim]PF₆/TX-100/water) as nano-reactor. The structure and morphology of PABMOF were characterized by FT-IR, XRD, XPS, SEM, TG and BET. The resultant PABMOF was used as a adsorbent for H₂PO₄^- adsorption. The adsorption kinetics, isotherms and mechanism of H₂PO₄^- onto the resultant PABMOF were studied. The adsorption kinetic data was well suitable for pseudo-second-order kinetic model, and adsorption isotherm results demonstrated that the equilibrium data was fitted for Freundlich model. The water-holding and water-retention capacity of soil with TRSRFs addition of 2 wt% were74.3% and 52.13% at 30th day, respectively. Moreover, the release behavior of TRSRFs in water show that the cumulative release rate (C_r%) were 81.4% at 45 °C and 97.6% at 25 °C within 172 h, which displayed the excellent temperature-responsive property. The effect of TRSRFs on the growth of Chinese cabbage was investigated, which was indexed with the germination rate, plant height and root length of the crop.

Treatment of Gaseous Ammonia Emissions Using Date Palm Pits Based Granular Activated Carbon

The present work investigated the application of granular activated carbon (GAC) derived from date palm pits (DPP) agricultural waste for treating gaseous ammonia. Respective findings indicate increased breakthrough time (run time at which 5% of influent ammonia is exiting with the effluent gas) with a decrease in influent ammonia and increase in GAC bed depth. At a gas flow rate of 1.1 L/min and GAC column length of 8 cm, the following breakthrough trend was noted: 1295 min (2.5 ppmv) > 712 min (5 ppmv) > 532 min (7.5 ppmv). A qualitatively similar trend was also noted for the exhaustion time results (run time at which 95% of influent ammonia is exiting with the effluent gas). The Fourier Transform Infrared Spectroscopy (FTIR) findings for the produced GAC indicated some salient functional groups at the produced GAC surface including O–H, C–H, C–O, and S=O groups. Ammonia adsorption was suggested to result from its interaction with the respective surface functional groups via different mechanisms. Comparison with a commercial GAC showed the date palm pits based GAC to be having slightly higher breakthrough and exhaustion capacity.

Efficient Removal of Polycyclic Aromatic Hydrocarbons and Heavy Metals from Water by Electrospun Nanofibrous Polycyclodextrin Membranes

Here, a highly efficient membrane based on electrospun polycyclodextrin (poly-CD) nanofibers was prepared and exploited for the scavenging of various polycyclic aromatic hydrocarbons (PAHs) and heavy metals from water. The poly-CD nanofibers were produced by the electrospinning of CD molecules in the presence of a cross-linker (i.e., 1,2,3,4-butanetetracarboxylic acid), followed by heat treatment to obtain an insoluble poly-CD nanofibrous membrane. The membrane was used for the removal of several PAH compounds (i.e., acenaphthene, fluorene, fluoranthene, phenanthrene, and pyrene) and heavy metals (i.e., Pb²⁺, Ni²⁺, Mn²⁺, Cd²⁺, Zn²⁺, and Cu²⁺) from water over time. Experiments were made on the batch sorption of PAHs and heavy metals from contaminated water to explore the binding affinity of PAHs and heavy metals to the poly-CD membrane. The equilibrium sorption capacity (q _e) of the poly-CD nanofibrous membrane was found to be 0.43 ± 0.045 mg/g for PAHs and 4.54 ± 0.063 mg/g for heavy metals, and the sorption kinetics fitted well with the pseudo-second-order model for both types of pollutants. The membrane could be recycled after treatment with acetonitrile or a 2% nitric acid solution and reused up to four times with similar performance. Further, dead-end filtration experiments showed that the PAH removal efficiencies were as high as 92.6 ± 1.6 and 89.9 ± 4.8% in 40 s for the solutions of 400 and 600 μg/L PAHs, respectively. On the other hand, the removal efficiencies for heavy metals during the filtration were 94.3 ± 5.3 and 72.4 ± 23.4% for 10 and 50 mg/L solutions, respectively, suggesting rapid and efficient filtration of heavy metals and PAHs by the nanofibrous poly-CD membrane.

Fabrication of interlayer β-CD/g-C3N4@MoS2 for highly enhanced photodegradation of glyphosate under simulated sunlight irradiation

Graphitic carbon nitride (g-C₃N₄) has been considered to be a promising metal-free photocatalyst, although the high recombination rate of charge carriers and poor absorption of visible light have limited its applications. In order to overcome these problems, an interlayer composite photocatalyst that comprised β-cyclodextrin (β-CD), oxygen-doped C₃N₄ (O-C₃N₄) and molybdenum disulfide (MoS₂) was successfully constructed for the highly enhanced photodegradation of glyphosate in this study. The structure and morphology, optical properties, and photoelectrochemical properties of the prepared photocatalyst were characterized via a series of characterization techniques. The average fluorescence lifetime of the composite photocatalyst was extended from 6.67 ns to 7.30 ns in comparison with that of g-C₃N₄, which indicated that the composite photocatalyst enhanced the absorption of visible light and also inhibited the recombination of electron–hole pairs. The mass ratio of MoS₂ that corresponded to O-C₃N₄/MoS₂-5 enabled the highest removal rate under simulated sunlight irradiation, which was almost twice that achieved using pure g-C₃N₄. Relative species scavenging experiments revealed that ·O₂⁻ was the main species during the process of photodegradation. Besides, a toxicity test indicated that glyphosate became less toxic or non-toxic after photodegradation. This study provided an effective, feasible and stable photocatalyst driven by simulated sunlight irradiation for the highly enhanced photodegradation of glyphosate.

The fabrication of an interlayer β-CD/g-C₃N₄@MoS₂ composite photocatalyst for highly enhanced photodegradation of glyphosate and a toxicity test.

Removal Effect of Atrazine in Co-Solution with Bisphenol A or Humic Acid by Different Activated Carbons

Activated carbons (ACs) based on apricot shells (AS), wood (W), and walnut shells (WS) were applied to adsorb atrazine in co-solutions. To study the effect of Bisphenol A (BPA) on the adsorption behavior of atrazine, the adsorption performance of ACs for BPA in single solution was studied. The results demonstrated that the adsorption kinetics of BPA fitted the pseudo-second-order model, the adsorption isotherms of BPA followed the Langmuir model. Meanwhile, the adsorption kinetics of atrazine fitted the pseudo-second-order kinetics model and the isotherm was consistent with the Freundlich model both in single solution and co-solution. In addition, competitive adsorption was observed when atrazine coexisted with BPA or humic acid. For the adsorption capacity, the adsorption amount of ASAC, WAC, and WSAC for atrazine obviously decreased by 18.0%, 30.0%, and 30.3% in the presence of BPA, respectively, which was due to the π−π interactions, hydrophobic interactions, and H-bonds, resulting in the competitive adsorption between atrazine and BPA. This study contributes to the further understanding of the adsorption behavior for atrazine in co-solution.

Adsorption behavior and mechanism of β-cyclodextrin–styrene-based polymer for cationic dyes

These figures show that the cyclodextrin polymer was synthesized successfully and possessed good thermal stability.