Characterization and Performance of Hollow Silica for Adsorption of Amoxicillin in Aqueous Solutions.

Two kinds of hollow silica materials, namely H-SiS1 and H-SiS2, were synthesized using the yeast template method and the Pickering emulsion polymerization method, respectively. The adsorbents were synthesized to adsorb amoxicillin (AMX) from an aqueous environment. Characterization results indicated that hollow silica adsorbents exhibited excellent thermal stability even at temperatures above 700 °C. Several batches of static adsorption experiments were prepared to analyze the adsorption performance on AMX. Isotherm data on different adsorbents fitted well with the Langmuir model (from 15 °C to 35 °C), indicating a monolayer molecular adsorption mechanism for AMX. The maximum adsorption capacities of H-SiS1 and H-SiS2 were 8.40 and 3.46 mg/g at 35 °C, respectively. The adsorption kinetics was described well by the pseudo-second-order model, which indicated that chemical interactions were primarily responsible for AMX adsorption and could be the rate-limiting step during adsorption. These results suggested that H-SiS1 could be significantly useful as adsorbents for removal of AMX residuals from aqueous solution.

Chitosan-based biopolyelectrolyte complexes intercalated montmorillonite: A strategy for green flame retardant and mechanical reinforcement of polypropylene composites.

Due to dwindling petroleum resources and the need for environmental protection, the development of bio-based flame retardants has received much attention. In order to explore the feasibility of fully biomass polyelectrolyte complexes (PEC) for polyolefin flame retardant applications, chitosan (CS), sodium alginate (SA), and sodium phytate (SP) were used to prepare CS-based fully biomass PEC intercalated montmorillonite (MMT) hybrid biomaterials (SA-CS@MMT and SP-CS@MMT). The effects of two hybrid biomaterials on the fire safety and mechanical properties of intumescent flame-retardant polypropylene (PP) composites were compared. The SP-CS@MMT showed the best flame retardancy and toughening effect at the same addition amount. After adding 5 wt% SP-CS@MMT, the limiting oxygen index (LOI) value of PP5 reached 30.9 %, and the peak heat release rate (pHRR) decreased from 1348 kW/m2 to 163 kW/m2. In addition, the hydrogen bonding between polyelectrolyte complexes significantly improved the mechanical properties of PP composites. Compared with PP2, the tensile strength of PP5 increased by 59 %. This study provided an efficient and eco-friendly strategy for the large-scale production of renewable biomaterials with good thermal stability and expanded the application of macromolecular biomaterials in the field of fire safety.

Fabrication of double imprinted anchor points in cellulose nanocrystals-based hierarchical porous polyHIPEs for selective separation of flavoniods under physiological pH.

Previous research had proved that molecular imprinted polymers can be used as separation material for removing Naringin (NRG) from agricultural pomelo wastes effectively. But the adsorption amounts of NRG molecules from traditional MIPs was quite low by using boronic acid as functional monomer because of single affinity interaction. Therefore, we developed the new combination of bifunctional monomers (i.e. low pKa boronate affinity monomer 2,4-difluoro-3-formylphenylboronic acid and dopamine) based on cellulose nanocrystals (CNCs) mixed with polymerized high internal phase emulsion (polyHIPE, PH) through an double layer surface imprinted method. The introduction of polyethylenimine (PEI) can offer abundant anchor units for the growth of more anchor sites to immobilization template molecules. Importantly, largely improved selective adsorption amounts (50.79 µmol g-1), which may be attribute to the fabrication of the uniform growth of double imprinted layers onto the polydopamine (PDA)/boronic acid-based surfaces. In addition, the resulting double recognition molecular imprinted polymers (MIPs) based on hypercrosslinked PH (DR-HCLPH@MIPs) not only exhibited fast adsorption kinetic of NRG molecule, but also possessed excellent selectivity and high adsorption capacities at physiological pH. Meanwhile, the coarse NRG from pomelo waste can be high selectively extracted to 94.74%. Overall, this study provides a versatile approach for fabrication of the sandwich-biscuit-like double imprinting layer porous MIPs for precise identification and ultrafast transport separation of NRG from complex samples.

Adsorption of lead(II) by silica/cell composites from aqueous solution: kinetic, equilibrium, and thermodynamics studies.

Silica/cell composites were prepared for the adsorption of lead ions, Pb(II), from aqueous solution in a batch system. The silica/cell composites possessed micropores, high surface area, and abundant functional groups. Adsorption performance was investigated by analyzing the effects of such factors as the initial pH, contact time with different initial concentration, and initial Pb(II) concentration at different temperature. The kinetic data were fitted to pseudo-second-order and intraparticle diffusion kinetic models. The results were better fitted by the pseudo-second-order kinetic model. Intraparticle diffusion increased with an increase of initial concentration and the sorption process was controlled by film diffusion. The Langmuir isotherm model was fitted to the experimental data significantly better than Freundlich and Dubinin-Radushkevich isotherm models. The maximum adsorption capacity was 97.10 mg g(-1), according to the Langmuir isotherm model. Thermodynamics parameters confirmed the spontaneous, endothermic, and entropy-gained nature within the studied temperature range (from 298 to 318 K). The composites could be effectively desorbed by the 2.0 mol L(-1) HNO3 solution and would be a potential adsorbent.

Visual Analysis of International Environmental Security Management Research (1997-2021) Based on VOSviewer and CiteSpace.

To investigate the international development status and hot trends in the field of environmental security management in recent years, the published the environmental security management literature from 1997 to 2021, which was retrieved from Web of Science, with VOSviewer as the main and CiteSpace as the auxiliary, through the cooperation network of authors, scientific research institutions, and countries. The keywords were visualized by clustering, time zone analysis, and burst analysis. A total of 7596 articles were retrieved, forming six main clustering labels, including 28,144 authors. The research hotspots are from the fields of personal health, society, agriculture, ecological environment, energy, and sustainable development, as well as the development of internet environmental safety management, such as big data, Bayesian networks, and conceptual frameworks. Through cluster analysis, the cooperation of major research teams and scientific research institutions and the cooperation and development between countries were analyzed. The cooperation between scientific research institutions in various countries is relatively close. The United States currently occupies a dominant and authoritative position in this field. China has cooperated more closely with the United States, Britain, Australia, and India.

Removal of cefalexin using yeast surface-imprinted polymer prepared by atom transfer radical polymerization.

The first use of yeast as a support in the molecular imprinting field combined with atom transfer radical polymerization was described. Then, the as-prepared molecularly imprinted polymers were characterized by Fourier transmission infrared spectrometry, scanning electron microscope, thermogravimetric analysis, and elemental analysis. The obtained imprinted polymers demonstrated elliptical-shaped particles with the thickness of imprinting layer of 0.63 µm. The batch mode experiments were adopted to investigate the adsorption equilibrium, kinetics, and selectivity. The kinetic properties of imprinted polymers were well described by the pseudo-second-order kinetic equation, indicating the chemical process was the rate-limiting step for the adsorption of cefalexin (CFX). The equilibrium data were well fitted by the Freundlich isotherm, and the multimolecular layers adsorption capacity of imprinted polymers was 34.07 mg g(-1) at 298 K. The selectivity analysis suggested that the imprinted polymers exhibited excellent selective recognition for CFX in the presence of other compounds with related structure. Finally, the analytical method based on the imprinted polymers extraction coupled with high-performance liquid chromatograph was successfully used for CFX analysis in spiked pork and water samples.

Study on Preparation of Chitosan/Polyvinyl Alcohol Aerogel with Graphene-Intercalated Attapulgite(GO-ATP@CS-PVA) and Adsorption Properties of Crystal Violet Dye.

Adsorption is one of the effective methods of treating dye wastewater. However, the selection of suitable adsorbent materials is the key to treating dye wastewater. In this paper, GO-ATP was prepared by an intercalation method by inserting graphene oxide (GO) into the interlayer of alabaster attapulgite (ATP), and GO-ATP@CS-PVA aerogel was prepared by co-blending-crosslinking with chitosan (CS) and polyvinyl alcohol (PVA) for the adsorption and removal of crystalline violet dye from the solution. The physicochemical properties of the materials are characterized by various methods. The results showed that the layer spacing of the GO-ATP increased from 1.063 nm to 1.185 nm for the ATP, and the specific surface area was 187.65 m2·g-1, which was 45.7% greater than that of the ATP. The FTIR results further confirmed the success of the GO-ATP intercalation modification. The thermogravimetric analysis (TGA) results show that the aerogel has good thermal stability properties. The results of static adsorption experiments show that at 302 K and pH 9.0, the adsorption capacity of the GO-ATP@CS-PVA aerogel is 136.06 mg·g-1. The mass of the aerogel after adsorption-solution equilibrium is 11.4 times that of the initial mass, with excellent adsorption capacity. The quasi-secondary kinetic, Freundlich, and Temkin isotherm models can better describe the adsorption process of the aerogel. The biobased composite aerogel GO-ATP@CS-PVA has good swelling properties, a large specific surface area, easy collection and a low preparation cost. The good network structure gives it unique resilience. The incorporation of clay as a nano-filler can also improve the mechanical properties of the composite aerogel.

Biosorption of Pb(II) by biomass of KC-2: kinetic, equilibrium and characteristic studies.

Performance and characteristics of biosorption of Pb(II) had been studied in a batch system using the fungal strain biomass, KC-2. The biosorption performance was investigated by analysing the effects of such factors as the initial pH, initial Pb(II) concentration, and contact time at 303 K. The maximum Pb(II) adsorption was obtained at pH 5.0. The experimental data were described by the pseudo first-order, pseudo second-order and intraparticle diffusion kinetic models, and were closely followed the pseudo second-order kinetic model. The equilibrium experimental data were well fitted to Langmuir model and the maximum biosorption capacity was 84.03 mg g(-1). The adsorption mechanism was examined by FTIR, SEM and EDAX analysis. Results indicated that carboxylic, hydroxyl and amine groups were involved in the biosorption and ion exchange mechanism existed.

Boronate affinity imprinted hydrogel sorbent from biphasic synergistic high internal phase emulsions reactor for specific enrichment of Luteolin.

The dynamic coexistence of heterostructures is crucial for the synergistic function of molecularly imprinted polymers (MIPs) derived from high internal phase emulsions (HIPEs). In this work, hydrophilic boronate affinity imprinted hydrogel sorbents (H-UIO-66-NH2-IHIPEs) were prepared by biphasic synergistic HIPEs droplet reactors filled with reactive microencapsulation system, and used to capture and separate cis-diol containing luteolin (LTL) from complex extraction samples with high selectivity. As the main solid emulsifier, UiO-66-NH2, prototype zirconium-based metal-organic frameworks (MOFs) greatly improves the mechanical performance of the hydrogel, whilst preventing overuse of surfactants. Space-confined formation of imprinted sites in the external phase is realized in the presence of hydrophilic acrylamide phenylboric acid monomer (H-BA), which endows the specific affinity with pH responsiveness to LTL. In addition, the filled microinclusion compound containing elastic monomer octadecyl methacrylate (SMA) and functional monomer glycidyl methacrylate (GMA) simultaneously added interfacial cross-linking reaction to provide stable pore volume and pore shape. Combined with these excellent properties, H-UIO-66-NH2-IHIPEs showed fast capture kinetics (75 min) and large uptake amount (39.77 mg g-1) at 298 K, and confirmed the existence of a uniform chemisorption monolayer. Moreover, excellent recyclability of 6.24% loss in adsorption amount after five adsorption-desorption cycles was observed. Finally, the LTL content of the purified product (about 97.38%) was higher than that of the crude extract (about 85.0%). This study sheds a new light for the design of novel imprinted hydrogel sorbents combined with binary synergistic components.

Prominent adsorption of Cr(VI) with graphene oxide aerogel twined with creeper-like polymer based on chitosan oligosaccharide.

Low-density aerogels with three-dimensional porous structure were synthesized using soluble chitosan oligosaccharide (COS) and graphene oxide (GO) as raw materials under mild conditions. Tetraethylenepentamine was used as the crosslinker of COS and the bridge between GO and COS, as well as the provider of functional groups. Structural characterizations revealed that crosslinked COS polymers firmly fixed on the surfaces of GO sheets and abundant amino groups homogeneously distributed in the pores. The adsorption capacity of the aerogel for Cr(VI) can reach up to 519.8 mg/g, while the adsorption efficiency for trace Cr(VI) adsorption can also reach 100% especially. The adsorption mechanism was investigated with X-ray photoelectron spectroscopy and zeta potential analysis. The superb properties suggested that the strategy of using COS as a raw material for the fabrication of adsorbents with controllable structure and form is meaningful.

Construction of lanthanum modified MOFs graphene oxide composite membrane for high selective phosphorus recovery and water purification.

Metal organic framework materials (MOFs) are kinds of hybrid materials with intra-molecular pores formed by self-assembly of organic ligands and metal ions through coordination bonds. In the paper, a type of MOFs named as [Zn(µ-L)(µ-1,3-dpp)](mof-1), using Zn2+ as metal ions, 4,4'-oxybis(benzoic acid) and 1,3-di(4-pyridyl)propane as organic ligands was synthesized. The rare earth element lanthanum, which has specific adsorption for phosphorus, is intercalated into mof-1 by the impregnation method in order to remove phosphorus-containing wastewater. In order to optimize the nano-sized La-mof-1 materials to facilitate separation, we prepared a membrane by blending MOFs materials with graphene oxide (GO) by pressure application. The addition of GO not only facilitates the separation of materials, but also has excellent removal ability for water purification. After a series of structural characterization, the adsorption properties of materials were tested. The experimental results showed that the total phosphorus in the water can get to the maximum adsorption capacity when pH = 4.0. It can be viewed in thermodynamic studies that increasing the temperature favors the adsorption reaction. Increasing the temperature to the 318 K, the equilibrium adsorption capacity of the membrane to total phosphorus in the water reached 139.51 mg/g. The adsorption removal rate of total phosphorus can reach 100% when its concentration is lower than 100 mg/L. This highlights the advantages of intercalating lanthanum into MOFs. The penetration curve was drawn by dynamic adsorption experiments to understand the mass transfer mechanism of La-mof-1GO membrane. Since GO also has a large specific surface area, it is another excellent adsorption material. Experimental data showed that compared with the original water sample, the removal rate of COD in the water reached 73.9%.

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

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 13C 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.

Selective removal of erythromycin by magnetic imprinted polymers synthesized from chitosan-stabilized Pickering emulsion.

Magnetic imprinted polymers (MIPs) were synthesized by Pickering emulsion polymerization and used to adsorb erythromycin (ERY) from aqueous solution. The oil-in-water Pickering emulsion was stabilized by chitosan nanoparticles with hydrophobic Fe3O4 nanoparticles as magnetic carrier. The imprinting system was fabricated by radical polymerization with functional and crosslinked monomer in the oil phase. Batches of static and dynamic adsorption experiments were conducted to analyze the adsorption performance on ERY. Isotherm data of MIPs well fitted the Freundlich model (from 15 °C to 35 °C), which indicated heterogeneous adsorption for ERY. The ERY adsorption capacity of MIPs was about 52.32 µmol/g at 15 °C. The adsorption kinetics was well described by the pseudo-first-order model, which suggested that physical interactions were primarily responsible for ERY adsorption. The Thomas model used in the fixed-bed adsorption design provided a better fit to the experimental data. Meanwhile, ERY exhibited higher affinity during adsorption on the MIPs compared with the adsorption capacity of azithromycin and chloramphenicol. The MIPs also exhibited excellent regeneration capacity with only about 5.04% adsorption efficiency loss in at least three repeated adsorption-desorption cycles.

Synthesis of chitosan/γ-Fe2O3/fly-ash-cenospheres composites for the fast removal of bisphenol A and 2,4,6-trichlorophenol from aqueous solutions.

The chitosan/fly-ash-cenospheres/γ-Fe(2)O(3) (CTS/γ-Fe(2)O(3)/FACs) magnetic composites were prepared by microemulsion process. The resulting composites were characterized by XRD, FT-IR, SEM, TGA, DTG and VSM, and the results indicated that CTS/γ-Fe(2)O(3)/FACs exhibited magnetic property (M(s)=6.553 emu g(-1)) and thermal stability, and composed of chitosan wrapping magnetic γ-Fe(2)O(3) and fly-ash-cenospheres (thickness of the cross-linked chitosan was about 5.2 µm). Then the CTS/γ-Fe(2)O(3)/FACs were employed as adsorbents for the fast removal of bisphenol A (BPA) and 2,4,6-trichlorophenol (TCP) from aqueous solutions. The adsorption performances of CTS/γ-Fe(2)O(3)/FACs were investigated by batch mode experiments with respect to pH, temperature, initial concentration, contact time and binary solution system. The Langmuir isotherm model was fitted to the equilibrium data better than the Freundlich model, and the kinetic properties were well described by the pseudo-second-order equation. The effects of binary solution systems also demonstrated that BPA adsorption onto CTS/γ-Fe(2)O(3)/FACs was more affected by the simultaneous presence of competitive phenolic compound than that of TCP. In addition, the resulting composite reusability without obviously deterioration in performance was demonstrated by at least three repeated cycles.