Zinc-doped and biochar support strategies to enhance the catalytic activity of CuFe2O4 to persulfate for crystal violet degradation.

Sulfate radicals-based Fenton-like technology has placed more emphasis on effectively dealing with the threat of dye wastewater. In this work, the Zn-doped CuFe2O4@biochar composite (Cu0.9Zn0.1Fe2O4@BC) was prepared through the convenient sol-gel pyrolysis process and applied as heterogeneous persulfate (PS) activator for crystal violet (CV) degradation. The crystal morphology and physicochemical properties of Cu0.9Zn0.1Fe2O4@BC were investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), Brunauer-Emmett-Teller method (BET), and X-ray photoelectron spectroscopy (XPS). The morphology of the catalyst changed before and after Zn doping. The crystallite size, lattice constant, saturation magnetization, and oxygen vacancy content increased after doping Zn. Compared with CuFe2O4@BC, the CV degradation efficiency of Cu0.9Zn0.1Fe2O4@BC activating PS increased from 87.7 to 96.9%, and the corresponding reaction rate constant increased by about 3.69 times. The effect of experimental conditions was systematically studied on the degradation progress. The degradation efficiency of CV was 91% after five times cycle experiments. Multiple experiments indicated that SO4•-, •OH and O2•- predominated for CV degradation. The degradation mechanism of CV in the Cu0.9Zn0.1Fe2O4@BC/PS system involved both free radical (SO4•-, •OH and O2•-) and non-free radical pathways (electron transfer). The possible degradation pathways were investigated according to the ultra-performance liquid chromatography mass spectrometry (UPLC-MS) analysis of degradation intermediates. The result showed that Cu0.9Zn0.1Fe2O4@BC have an excellent catalyst performance, which provides a new strategy for improving catalytic activity.

Nitrogen-doped carbon dots for dual-wavelength excitation fluorimetric assay for ratiometric determination of phosalone.

N-doped carbon dots (N-CDs) were fabricated in a simple procedure by hydrothermal treatment of cellobiose and urea. When excited at 235 nm or 327 nm, only one emission peak at around 420 nm has been observed. With the addition of phosalone, the excitation band at 235 nm was efficiently quenched within 1 min, while the excitation band at 327 nm showed little change. Accordingly, the fluorescence of the N-CDs-phosalone mixture showed quenching under 254-nm UV light, while nearly no fluorescence quenching could be observed under 365-nm UV light. This phenomenon provides a novel anti-false-positive mechanism for phosalone identification. Therefore, the label-free ratiometric sensor for rapid, naked-eye, and anti-false-positive detection of phosalone was proposed for the first time based on the intrinsic dual-excitation N-CDs. Under the optimum experimental conditions, the linear ranges of the excitation-based ratiometric assay were 0.08~4.0 µg/mL and 4.0~14.0 µg/mL; the limit of detection was 28.5 ng/mL. The as-constructed sensor was applied to detect phosalone residue in actual samples, and results were compared with the standard gas chromatographic (GC) method. The recoveries of the established sensor were between 90.0% and 110.0% with RSD lower than 6.6%, while that for the GC method was between 92.5% and 113.0% with RSD lower than 5.8%. Results reveal that the accuracy (recovery) and precision (RSD) of the as-constructed method are comparable to the standard GC method. In this paper, dual-excitation N-doped carbon dots (N-CDs) were synthesized by a simply one-step hydrothermal method for the first time. The novel dual-excitation ratiometric sensor based on the sole intrinsic N-CDs was constructed for phosalone sensing.

Determination of melamine in milk based on ß-cyclodextrin modified carbon nanoparticles via host-guest recognition.

Illegal addition of melamine (MEL) to milk has caused serious food safety accident. It is urgent to develop a highly sensitive method for detecting MEL in milk. ß-Cyclodextrin with inner hydrophobic and outer hydrophilic cavities have been widely used in smart sensors design. In this study, an "ON-OFF-ON" sensor for MEL detection was constructed based on ß-cyclodextrin modified carbon nanoparticles (ß-CD-CNPs). The sensor is switched "OFF" when Fe3+ interacts with ß-CD-CNPs and switched "ON" when MEL replaces Fe3+. Fluorescence recovery of ß-CD-CNPs exhibits good linear correlations with MEL concentration ranging from 10.00 ng/mL ~ 180.00 ng/mL and 180.00 ~ 1000.00 ng/mL, the detection limit is 6.82 ng/mL. The sensor was applied to analysis melamine in milk samples with recovery between 94.80% ~ 102.05%, and RSD bellow 12.61%. The results show that this method can meet the requirements of real sample analysis.

Preparation of a Stable Nanoscale Manganese Residue-Derived FeS@Starch-Derived Carbon Composite for the Adsorption of Safranine T.

To develop a novel, low-cost adsorbent with natural material and industrial waste as raw materials, nanoscale manganese residue-derived FeS@starch-derived carbon (MR-FeS@SC) composite was prepared by the carbonization of starch-manganese residue gel. Manganese residue-derived FeS (MR-FeS) and starch-derived carbon (SC) were also prepared as contrasts for comparative studies. The MR-FeS@SC nanocomposite exhibited relatively large specific surface area and micropore volume, appropriate pore size, abundant functional groups, strong interaction between the functional groups of SC and MR-FeS, and the immobilization and uniform distribution of MR-FeS nanoparticles onto SC support material, which contributed to better adsorption properties for the removal of Safranine T (ST) from the aqueous solution compared with those of MR-FeS and SC. The adsorption could be conducted at a wide range of pH and temperature to achieve a satisfy removal efficiency of ST with MR-FeS@SC nanocomposite as adsorbent. The adsorption kinetics well followed the pseudo-second-order model, and the dominant mechanism was chemisorption. The adsorption behavior was well described by the Langmuir isotherm model. Due to the strong interaction between MR-FeS nanoparticles and SC support, MR-FeS@SC nanocomposite exhibited better reusability and stability even after fifteen cycles. This study provides a facile method of preparing effective and stable adsorbents for the treatment of dye wastewater.

Damaged starch derived carbon foam-supported heteropolyacid for catalytic conversion of cellulose: Improved catalytic performance and efficient reusability.

To develop an efficient heterogeneous catalyst with good stability and reusability for catalytic conversion of cellulose to platform compounds, carbon foam (CF) was used to immobilize phosphotungstic acid (HPW) to prepare CF-supported HPW (HPW/CF) catalyst. Three-dimensional CF was prepared by carbonization of bread (precursor of CF) with mechanical activation (MA)-damaged starch, gluten protein, and yeast as materials. CF30 (30 wt% of gluten protein) exhibited good mechanical strength, relatively high specific surface area, and desired hierarchical porous structure. HPW was successfully anchored onto CF30 by grafting to prepare HPW/CF30 catalyst, which could effectively catalyze the hydrolysis of cellulose to produce glucose, especially for the hydrolysis of MA-pretreated cellulose with small granules and amorphous structure. The affinity between free hydroxyl groups of MA-pretreated cellulose and oxygen-containing groups of CF30 enhanced the catalytic efficiency of HPW/CF30. In addition, HPW/CF30 catalyst exhibited good reusability and was easily separated from reaction system for recycling.

Single-step synthesis of eucalyptus sawdust magnetic activated carbon and its adsorption behavior for methylene blue.

Eucalyptus wood-based magnetic activated carbon (MAC) was prepared using single-step carbonization activation magnetization with FeCl3 and utilized for the adsorption of methylene blue (MB). The MAC was prepared using the following conditions: the mass ratio of FeCl3 to eucalyptus sawdust was controlled to 2 : 1, the one-step carbonated activated magnetization temperature and time was 700 °C and 75 min. The prepared MAC was evaluated for textural characteristics such as the adsorption capacity, pore structure, surface chemical functional groups, magnetic properties, microcrystalline structure, and the surface morphology using the test methods described in the National Standard of China, these were N2-adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR), value stream mapping (VSM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Batch experiments were carried out to evaluate the adsorption behavior of MB on the prepared MAC at different temperatures of 298-328 K and MB initial concentration of 50.0-500.0 mg L-1. The results were as follows: the iodine number, methylene blue adsorption and phenol adsorption of the prepared MAC were 473.14, 228.22 and 70.90 mg g-1, respectively; MAC exhibited a microporous and mesoporous structure with a mesoporosity of 36%, the BET specific surface area, average pore diameter and pore volume were 645.23 m2 g-1, 2.71 nm and 0.44 cm3 g-1, respectively, and for the magnetic parameters the following results were found, a H c of 108.51 Oe, M s of 30.37 emu g-1 and M r of 2.46 emu g-1; there were OH, C-O, C[double bond, length as m-dash]O, C[double bond, length as m-dash]C, COO, C-N, and Fe-O groups on the MAC surface, and Fe3O4 existed in the pores and surfaces of the MAC. The MB adsorption on the MAC followed the Langmuir isotherm and Dubinin-Radushkevich isotherm model, the adsorption process was a spontaneous, endothermic chemisorption progress, followed by the pseudo-second-order model, and the adsorption process was influenced by multiple diffusion steps, the pore diffusion process was the rate-controlling step, however, the adsorption process was also affected by the film diffusion and surface adsorption. The results reveal that MAC efficiently adsorbs MB and can be easily separated and recovered by an external magnetic field. The as-prepared MAC could be used as a potential adsorbent for organic pollutant wastewater treatment.

Synthesis of a magnetic polystyrene-based cation-exchange resin and its utilization for the efficient removal of cadmium (II).

A magnetic cation-exchange resin (MCER) was prepared by copolymerization of oleic acid-grafted magnetite with styrene, divinylbenzene (DVB), and triallylisocyanurate (TAIC) for removing Cd(II) from wastewater. A non-magnetic cation-exchange polystyrene resin (CEPR) was also prepared as a reference. Structural and morphological analyses revealed that the MCER and CEPR were mesoporous microspheres; the MCER contained about 25% Fe3O4. The influence of temperature, pH, contact time, and the initial concentration of Cd(II) on the adsorption of Cd(II) was investigated. The maximum adsorption capacity of the MCER reached 88.56 mg/g, which was achieved at 343 K using a Cd(II) initial concentration of 200 mg/L. The adsorption processes attained equilibrium within 120 min for the MCER and 300 min for the CEPR, and were well described by a pseudo-second-order kinetic model. Furthermore, the equilibrium adsorption data fitted the Freundlich isotherm model better than the Langmuir model. The superior magnetic response and regeneration of the MCER make it a good candidate as an adsorbent for removing Cd(II) from wastewater.

Alkaline pretreatment and the synergic effect of water and tetralin enhances the liquefaction efficiency of bagasse.

Bagasse liquefaction (BL) in water, tetralin, and water/tetralin mixed solvents (WTMS) was investigated, and effects of tetralin content in WTMS, temperature, and alkaline pretreatment of bagasse on liquefaction efficiency were studied. At 300°C, bagasse conversion in WTMS with tetralin content higher than 50 wt% was 86-87 wt%, whereas bagasse conversion in water or tetralin was 67 wt% or 84 wt%, respectively. Because the solid conversion from liquefaction in WTMS with tetralin content higher than 50 wt% was always higher than that in water or tetralin at temperatures between 250 and 300°C, a synergic effect between water and tetralin is suggested. Alkaline pretreatment of bagasse resulted in significantly higher conversion and heavy oil yield from BL in water or WTMS. The effect of deoxygenation by the present liquefaction method is demonstrated by lower oxygen contents (16.01-19.59 wt%) and higher heating values (31.9-34.8 MJ/kg) in the produced oils.