Yuru Kang

Facile self-assembly of Au nanoparticles on a magnetic attapulgite/Fe3O4 composite for fast catalytic decoloration of dye

In this paper, we employed a simple and efficient electrostatic self-assembly strategy to fabricate superparamagnetic attapulgite/Fe3O4/Au nanoparticles (APT/Fe3O4/AuNPs) nanocomposites with a well-dispersed distribution of AuNPs using natural chitosan (CTS) as a “bridge”. The “toruloid” APT/Fe3O4 composite with negative surface charges was firstly prepared by a one-step solvent-thermal reaction between APT, FeCl3 and ethylene glycol, and then the positively charged CTS was used as a “double sided tape” to tightly adhere APT/Fe3O4 and AuNPs through electrostatic interaction. UV-vis, XRD and TEM analyses proved that the “toruloid” structure was formed, and AuNPs were successfully attached on the APT surface with good dispersion. The formation of the “toruloid” composite structure can not only bring stronger magnetism, but also facilitate the attachment of AuNPs. The APT/Fe3O4/AuNPs nanocomposite shows excellent catalytic activity, which can rapidly catalytically decolor a solution of Congo red (20 mg L−1) within 2 min at a low dosage of 0.3 g L−1. In addition, the nanocomposite shows strong magnetism with a maximum magnetization rate of 33.6 emu g−1. This makes the nanocomposite prone to be magnetically separated and recycled.

Preparation of a polyelectrolyte-coated magnetic attapulgite composite for the adsorption of precious metals

By the layer-by-layer self-assembly of chitosan and cysteine modified β-cyclodextrin on the surface of Fe3O4 nanoparticle-decorated attapulgite, the polyelectrolyte-coated magnetic attapulgite composite (Fe3O4/ATP@(CS/Cys-β-CD)8) was prepared for the adsorption of precious metals. The as-synthesized Fe3O4/ATP@(CS/Cys-β-CD)8 composite was characterized by zeta potential measurements, Fourier transform infrared spectroscopy, X-ray diffraction and vibrating sample magnetometry. The Fe3O4/ATP@(CS/Cys-β-CD)8 composite has an adsorption yield of about 90% for Ag+, 90% for Pd2+ and 60% for Pt4+. Moreover, it was found that the adsorption of Ag+ and Pd2+ was preferential to that of Pt4+. The results of X-ray photoelectron spectroscopy indicated that the precious metals accept electrons provided by the N, O or S atoms of the Fe3O4/ATP@(CS/Cys-β-CD)8 composite during the process of adsorption. Therefore, the Fe3O4/ATP@(CS/Cys-β-CD)8 composite is a promising recyclable and low-cost adsorbent for the adsorption of trace precious metal ions.

Synthesis, characterization and swelling properties of guar gum-g-poly(sodium acrylate-co-styrene)/muscovite superabsorbent composites

Abstract A series of novel guar gum-g-poly(sodium acrylate-co-styrene)/muscovite (GG-g-P(NaA-co-St)/MVT) superabsorbent composites were prepared by free-radical grafting copolymerization of natural guar gum (GG), partially neutralized acrylic acid (NaA), styrene (St) and muscovite (MVT) using ammonium persulfate (APS) as the initiator and N,N-methylene-bis-acrylamide (MBA) as the crosslinker. Optical absorption spectra confirmed that NaA and St had been grafted onto the GG main chain and MVT participated in the polymerization reaction. The simultaneous introduction of St and MVT into the GG-g-PNaA matrix could clearly improve the surface morphologies of the composites, and MVT led to better dispersion in the polymeric matrix without agglomeration, as revealed by electron microscopy. The effects of St and MVT on the water absorption and swelling behavior in various saline solutions, aqueous solutions of hydrophilic organic solvents and surfactant solutions were investigated. Results indicated that the swelling rate and capabilities of the composites were markedly enhanced by the incorporation of the hydrophobic monomer St and inorganic MVT clay mineral. The superabsorbent composite showed a clearer deswelling characteristic in solutions of multivalent saline, acetone and ethanol, and cationic surfactant than that in the solutions of multivalent saline, methanol and anionic surfactant.

Enhanced Adsorptive Removal of Methylene Blue from Aqueous Solution by Alkali-Activated Palygorskite

Silicate clay materials are promising natural adsorbents with abundant, low cost, stable, and eco-friendly advantages, but the limited adsorption capacity restricts their applications in many fields. Herein, palygorskite (PAL) was facilely activated with alkali to enhance its adsorptive removal capability for methylene blue (MB). The effects of alkali activation on the microstructure, physicochemical, and adsorption properties of PAL for MB were intensively investigated. It was found that the moderate alkali activation can partially remove the metal cations (i.e., Al3+, Mg2+) and Si in the crystal backbone of PAL by which new “adsorption sites” were created and the surface negative charges increased. The adsorption capacity and rate of PAL for MB were evidently enhanced due to the effective activation. The adsorption isotherms were described by Freundlich isotherm model very well, and the adsorption kinetics can be accurately presented by a pseudo-second-order model. It can be inferred from the fitting results that the overall adsorption process was controlled by external mass transfer and intra-particle diffusion (the dominant role). The multiple adsorption interactions (hydrogen bonding, electrostatic interactions, mesopore filling, and complexing) were turned out to be the dominant factors to improve the adsorption properties. It was revealed that the activated PAL could be used as a potential adsorption candidate for environmental applications.

Efficient Adsorption and Recovery of Pb(II) from Aqueous Solution by a Granular pH-Sensitive Chitosan-based Semi-IPN Hydrogel

A series of granular pH-sensitive semi-interpenetrating polymer network (semi-IPN) hydrogels based on chitosan (CTS), acrylic acid (AA) and gelatine (GE) were utilized for the adsorption and recycle of Pb(II) from aqueous solutions. The composite hydrogels have been characterized by FT-IR and TGA. The effects of contact time, pH value and initial Pb(II) concentration on the adsorption were investigated. Results indicated that the adsorption capacity of the hydrogel increased with increasing pH value and initial Pb(II) concentration, and a pH-sensitive adsorption characteristic was presented. The adsorption rate of the semi-IPN hydrogels on Pb(II) is fast with an adsorption rate constant of 14.9790 mg/(g·s), and adsorption equilibrium could be reached within 10 min. The adsorption isotherms of the hydrogels for Pb(II) could be described well by the Langmuir equation, rather than the Freundlich equation. The as-prepared hydrogels showed good reusability with 0.05 mol/l HNO3 solutions as the desorbing agent and 0.1 mol/l NaOH solutions as the regeneration agent, respectively. After five consecutive adsorption-desorption processes, the semi-IPN hydrogel with 20 wt% GE may reach 85.26% of its initial adsorption capacity. In addition, the adsorbed Pb(II) can be quantitatively recovered by simply eluting the hydrogel with dilute HNO3 solution, and a recovery ratio of 89.27% was reached for the semi-IPN hydrogel. The satisfactory adsorption amount is mainly derived from the chelating of functional groups (i.e. –COO− and –NH2) with Pb(II) ions. The hydrogel adsorbents exhibited excellent affinity for Pb(II), and can be applied to treat wastewater containing heavy metal ion and simultaneously recover the valuable metal sources.

Attapulgite Modified with Silane Coupling Agent for Phosphorus Adsorption and Deep Bleaching of Refined Palm Oil

Attapulgite (ATP) clay was modified with different silane coupling agents [3-triethoxysilylpropylamine (KH550), γ-glycidoxypropyltrimethoxysilane (KH560) and γ-methacryloxypropyltrimethoxysilane (KH570)] and used as a decolourizer for bleaching of refined palm oil. The effects of different silane coupling agents on the structure, surface charges and pore structure of ATP were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, Zeta potential and nitrogen adsorption-desorption isotherm techniques, and the decolourization efficiency of the modified ATP was evaluated by UV-Vis absorbance and Lovibond colour. The results show that the KH550-modified ATP exhibits the best decolourization performance, which can decrease the red-yellow value of refined palm oil by 31.96% and the phosphorus content by 77.69% after bleaching; while the unmodified ATP can only decrease these values by 17.30% and 62.31%, respectively.

Effects of synbiotic supplementation on growth performance, carcass characteristics, meat quality and muscular antioxidant capacity and mineral contents in broilers

BACKGROUND The present study aimed to investigate the effects of dietary synbiotic supplementation on growth performance, carcass composition, meat quality and muscular antioxidant capacity, and mineral contents in broilers. Accordingly, 96 day-old male broiler chicks (Arbor Acres Plus; Aviagen, Huntsville, AL, USA) were randomly allocated to two groups, and each group consisted of six replicates with eight chicks each. Birds were fed a corn-soybean meal basal diet supplemented with either 0 or 1.5 g kg-1 synbiotic, consisting of probiotics (Bacillus subtilis, Bacillus licheniformis and Clostridium butyricum) and prebiotics (yeast cell wall and xylooligosaccharide) from 1 to 42 days of age. RESULTS Compared with the control group, supplementation with a synbiotic increased average daily gain (P < 0.05) but reduced feed/gain ratio (P < 0.01) in broilers from 1 to 42 days of age. Similalrly, dietary synbiotic inclusion increased breast yield (P < 0.05) but decreased abdominal fat (P < 0.01) in broilers. The breast muscle pH value at 24 h postmortem in broilers was elevated with the incorporation of synbiotic (P < 0.05). By contrast, synbiotic supplementation lowered the cooking loss during heat treatment in a water bath, malondialdehyde content, and total Cr content in the thigh muscle in broilers (P < 0.05). CONCLUSION Dietary synbiotic supplementation into the diet of broilers may be an effective method for improving growth performance and carcass compositions, resulting in the production of meat with a favorable quality and oxidative stability.

All-into-one strategy to synthesize mesoporous hybrid silicate microspheres from naturally rich red palygorskite clay as high-efficient adsorbents

A mesoporous hybrid silicate microsphere with superior adsorption performance has been successfully synthesized by employing an “all-into-one” strategy and a simple one-pot hydrothermal process using naturally abundant low-grade red palygorskite (PAL) clay as raw material in the presence of non-toxic SiO32− and Mg2+ ions. As is expected, both the PAL and associated minerals transformed into a new amorphous mesoporous hybrid silicate microsphere without using any additional pore-forming template. The mesoporous silicate microsphere shows a large pore size of 37.74 nm, high specific surface area of 489.81 m2/g (only 54.67 m2/g for raw PAL) and negative surface potential of −43.3 mV, and its maximum adsorption capabilities for Methylene bule (MB) and Crystal violet (CV) reach 407.95 mg/g and 397.22 mg/g, respectively. Meanwhile, 99.8% of MB (only 53% for raw PAL) and 99.7% of CV (only 43% for raw PAL) were sucessfully removed from 200 mg/L of initial dye solution by only using 1 g/L of the adsorbent. In addition, the spent adsorbent can be easily regenerated and repeatly reused for muptiple cycles. The study on adsorption mechanism revealed that electrostatic attraction, hydrogen bonding and chemical complexing interactions are the main factors contributed to the high dye adsorption.

Ag(I)-triggered one-pot synthesis of Ag nanoparticles onto natural nanorods as a multifunctional nanocomposite for efficient catalysis and adsorption.

A multifunctional palygorskite/polyaniline/Ag nanoparticles (PAL/PANI/AgNPs) nanocomposite was prepared at room temperature using a simple one-pot in-situ polymerization reaction of aniline monomers triggered by Ag(I) on the surface of natural PAL nanorods. Ag(I) served as both the oxidant and the precursor of the AgNPs, which initiated the polymerization of aniline monomers on PAL nanorods while simultaneously being reduced to form Ag(0) nanoparticles (AgNPs). The in-situ formed AgNPs were evenly distributed on the surface of the PAL nanorods because the interfacial effect of PAL prevents their aggregation. The density and size of the AgNPs and the catalytic activity of the nanocomposites could be controlled by altering the molar ratio of aniline to Ag(I). The performance evaluation revealed that the nanocomposites could be used as highly active catalysts, which rapidly catalyzed the reduction of 4-nitrophenol (4-NP) within 2min and Congo red (CR) within 10min. The nanocomposites are also an effective adsorbent for H2PO4(-) able to remove 99.40% of H2PO4(-) (only 61.77% for raw PAL) from a solution with an initial concentration of 50mg/L. This multifunctional nanocomposite synthesized by a simple one-pot approach is a promising material for environmental applications.

Glycine-assisted evolution of palygorskite via a one-step hydrothermal process to give an efficient adsorbent for capturing Pb(II) ions

As the materials of “green 21st century material worlds”, natural silicates have received unprecedented attention by virtue of their abundance, low-cost, stability, and non-toxic and eco-friendly nature compared to other synthetic materials. With the aim to develop a new hybrid silicate adsorbent with improved adsorption properties, the naturally abundant palygorskite (PAL) was functionalized with glycine (GLY) via a simple one-step hydrothermal process and used for capturing Pb(II) ions from aqueous solution. The main reaction parameters, e.g., the pH values of the reaction medium, solid-to-liquid ratio, reaction time and dosage of GLY, were systematically optimized, and the as-prepared adsorbent was characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmittance electronic microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The results reveal that the PAL crystal was converted to a hybrid silicate material with the assistance of GLY, and simultaneously the functional groups were introduced during the hydrothermal reaction, which caused an evident enhancement in the adsorption capacity of PAL for Pb(II) ions from 55.76 mg g−1 to 123.24 mg g−1. Almost 99.60% of Pb(II) could be captured and removed from a 40 mg L−1 Pb(II) solution using the as-prepared GLY-PAL silicate adsorbent, which is obviously higher than the 83.85% achieved by raw PAL. The intensified complexation of the functional groups on the silicate with Pb(II), the electrostatic attraction and the pore adsorption are responsible for the enhancement in the adsorption capability.