Degradation of tetracycline under a wide pH range in a heterogeneous photo bio-electro-fenton system using FeMn-LDH/g-C3N4 cathode: Performance and mechanism.

The widespread use of antibiotics and the inefficiency of traditional degradation treatments pose threats to the environment and human health. Previous studies have reported the potential of bio-electro-Fenton (BEF) processes for antibiotic removal. However, some drawbacks, such as a strict pH range of 2-3 and iron sludge generation, limit their large-scale application. Thus, to overcome the narrow pH range of traditional BEF processes, a photo-BEF (PBEF) system was established using a novel FeMn-layered double hydroxide (LDH)/graphitic carbon nitride (g-C3N4) (FM/CN) composite cathode. The performance of the PBEF system was investigated by degrading tetracycline (TC) under low-power LED lamp irradiation. The results indicated that the pH range of the PBEF system could be expanded to 3-11 using an FM/CN cathode, which exhibited a TC removal efficiency of 63.0%-75.9%. The highest TC removal efficiency was achieved at pH 7. The efficient mineralization of TC by the PBEF system can be high, up to 67.6%. In addition, the TC removal mechanism was discussed in terms of reactive oxygen species, TC degradation intermediate analyses, and density functional theory (DFT) calculations. Strong oxidative hydroxyl radicals (·OH) were the dominant reactive oxidizing species in the PBEF system, followed by ·O2- and h+. Three pathways of TC degradation were proposed based on the analysis of intermediates, and the reactive sites attacked by electrophilic reagents were explored using DFT modeling. In addition, the overall toxicity of TC degradation intermediates effectively decreased in the PBEF system. This work offers deep insights into the TC removal mechanisms and performance of the PBEF system over a wide pH range of 3-11.

Bio-based adsorption foam composed of MOF and polyethyleneimine-modified cellulose for selective anionic dye removal.

With the increase of sustainable development goal, the bio-based adsorption materials with high and selective dye removal are important for water treatment in the dyeing industry. In this paper, a bio-based adsorption foam composed of metal-organic frameworks (MOF) and polyethyleneimine (PEI)-modified cellulose was prepared by a three-step process, i.e., PEI modification of cellulose fibers (PC), MOF decoration of PEI-modified cellulose (MIL-53@PC), and in-situ foaming with polyurethane. PEI modification provides cellulose fiber with more active sites for both dye adsorption and MOF bonding. We found that MIL-53 crystals were tightly bonded on the surface of PC through hydrogen bonding. Because of the abundant adsorption sites (e.g., amines, iron oxide group), the MIL-53@PC demonstrated high adsorption capacity and selectivity for anionic dye (e.g., 936.5 mg/g for methyl orange) through electrostatic interaction and hydrogen bonding. Finally, MIL-53@PC particles were blended with a waterborne polyurethane prepolymer to prepare a three-dimensional hydrophilic foam (MIL-53@PC/PUF), which not only maintained high adsorption capacity and selectivity of MIL-53@PC and also improved its recyclability and reusability. The MIL-53@PC/PUF offers a promising solution for dye wastewater treatment.

Two all-biomass cellulose/amino acid spherical nanoadsorbents based on a tri-aldehyde spherical nanocellulose II amino acid premodification platform for the efficient removal of Cr(VI) and Cu(II).

Adsorbents consisting of spherical nanoparticles exhibit superior adsorption performance and hence, have immense potential for various applications. In this study, a tri-aldehyde spherical nanoadsorbent premodification platform (CTNAP), which can be grafted with various amino acids, was synthesized from corn stalk. Subsequently, two all-biomass spherical nanoadsorbents, namely, cellulose/l-lysine (CTNAP-Lys) and cellulose/L-cysteine (CTNAP-Cys), were prepared. The morphologies as well as chemical and crystal structures of the two adsorbents were studied in detail. Notably, the synthesized adsorbents exhibited two important characteristics, namely, a spherical nanoparticle morphology and cellulose II crystal structure, which significantly enhanced their adsorption performance. The mechanism of the adsorption of Cr(VI) onto CTNAP-Lys and that of Cu(II) onto CTNAP-Cys were studied in detail, and the adsorption capacities were determined to be as high as 361.69 (Cr(VI)) and 252.38 mg/g (Cu(II)). Using the proposed strategy, it should be possible to prepare other all-biomass cellulose/amino acid spherical nanomaterials with high functional group density for adsorption, medical, catalytic, analytical chemistry, corrosion, and photochromic applications.

Magnetic nanocellulose-based adsorbent for highly selective removal of malachite green from mixed dye solution.

Herein, a novel magnetic adsorbent (BC/AA/MN@Fe3O4) was successfully prepared from waste bamboo fiber tissue and montmorillonite, and subsequently applied for the highly selective removal of malachite green (MG, removal efficiency = 97.3 %) from the mixed dye solution of MG with methyl orange (MO, removal efficiency = 4.5 %). The magnetic adsorbent has a high porosity with abundant mesopores. In the single dye MG solution, the adsorbent could effectively remove MG over a wide pH range from 4 to 10, and the maximum adsorption capacity (qmax) was 2282.3 mg/g. Moreover, the magnetic adsorbent could remove MG from various solutions including mixed dye solution, high salinity solution, and real river water dye solution. The thermodynamic results proved that the adsorption process of MG was spontaneous and endothermic. The adsorption of MG was due to the comprehensive effects of electrostatic attraction, hydrogen bonding interactions and ions exchange, between the adsorbent and MG. Furthermore, the BC/AA/MN@Fe3O4 exhibited an excellent reusability with adsorption efficiency above 53.4 % after five consecutive cycles. Therefore, the prepared magnetic nanocellulose-based adsorbent was expected to be a promising material for highly selective adsorption and separation of MG from mixed dye solution.

Simple ultrasonic integration of shapeable, rebuildable, and multifunctional MIL-53(Fe)@cellulose composite for remediation of aqueous contaminants.

Metal-organic frames (MOFs) have been recognized as one of the best candidates in the remediation of aqueous contaminants, while the fragile powder shape restricts the practical implementation. In this work, a shapeable, rebuildable, and multifunctional MOF composite (MIL-53@CF) was prepared from MIL-53 (Fe) and cellulose fiber (CF) using a simple ultrasonic method for adsorption and photocatalytic degradation of organic pollutants in wastewater. The results showed MIL-53(Fe) crystals were uniformly growth on CF surfaces and bonded with surface nanofibrils of CF through physical crosslinking and hydrogen bonding. Because of the high bonding strength, the MIL-53@CF composite exhibited an excellent compressive strength (3.53 MPa). More importantly, the MIL-53@CF composite was rebuildable through mechanical destruction followed by re-ultrasonication, suggesting the excellent reusability of MIL-53@CF for water remediation. The MIL-53@CF composite also had high adsorption capacities for methyl orange (884.6 mg·g-1), methylene blue (198.3 mg·g-1), and tetracycline (106.4 mg·g-1). MIL-53@CF composite could degrade TC through photocatalysis. The photocatalytic degradation mechanism was attributed to the Fe(II)/Fe(III) transform cycle reaction of MIL-53 crystal located on MIL-53@CF. Furthermore, the mechanical property and remoldability of MIL-53@CF composite increased its practicability. Comprehensively, MIL-53@CF composite provided a possible strategy to practically apply MOF in the remediation of aqueous contaminants.

Nanocellulose-based polyurethane foam adsorbent for pressure-driven dye-contaminated water purification.

Dye-contaminated water has caused a worldwide pollution, which is threatening aquatic organisms and human health. In this work, a pressure-driven foam adsorbent (PFA) was bioinspired from the tapestry turban for purifying the dye-contaminated water. The PFA was prepared using an one-step method from nanocellulose (NC), amino-functionalized ZIF-8 (ZIF-8-NH2), and high resilience polyurethane foam (PUF). It was applied to efficiently remove methyl orange (MO) and crystal violet (CV) dyes from dye-contaminated waste solutions. The maximum adsorption capacity of PFA for MO and CV was 225.9 mg/g (25 °C, pH = 2) and 41.6 mg/g (25 °C, pH = 10), respectively, which were acceptable as compared with the reported works. The dyes could be efficiently removed from various river water samples. After 5 cycles, the removal efficiencies of MO and CV decreased from 92.0% and 85.7% to 84.7% and 76.1%, respectively. Moreover, the PFA relied on pressure-driven force to release the purified water under a low pressure.

Supramolecular structure of microwave treated bamboo for production of lignin-containing nanocellulose by oxalic acid dihydrate.

Supramolecular structure of cellulosic materials from microwave treatment were throughly investigated for production of lignin-containing nanocellulose. The results revealed that both the intermolecular and intramolecular hydrogen bonds were altered by microwave irradiation. Cellulose Iß was the main component in microwave treated bamboo (MTB) with smaller interplanar spacing, and the cellulose molecules were loosely connected resulting in a loose structure. Thereafter, MTB was used to produce lignin-containing nanocellulose by using oxalic acid dihydrate (OAD) to test the feasibility on its efficiency. The chemical consumed for the preparation of lignin-containing nanocellulose (LCN) with a comparable yield (68.08-82.33 %) from MTB was merely 1/10 that from conventional cellulosic materials, indicating the supramolecular structural changes of bamboo cellulose induced by microwave treatment provided suitable conditions for the subsequent hydrolysis of OAD to prepare LCN. The LCN was further added into the polyvinyl alcohol (PVA) matrix endowed excellent UV shielding property and thermal stability for the PVA/LCN films. This study was aimed to provide an environmentally friendly method on the production and application of LCN from bamboo by employing microwave treatment from the perspective of supramolecular level.

Analysis of Components and Properties of Extractives from Alnus cremastogyne Pods from Different Provenances.

Chemical components with anti-oxidant, anti-inflammatory, and anti-cancer properties extracted from Alnus bark and leaves have been extensively studied. However, less attention has been paid to extractives from Alnus pods, which are mostly treated as waste. Here, extractives of Alnus cremastogyne pods from 12 provenances in Sichuan Province were studied for high value-added utilization of Alnus waste. The extractives were analyzed by Gas Chromatography-Mass Spectrometer (GC-MS), Ultraviolet-visible spectroscopy (UV-Vis spectra), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity. A total of 58, 49, and 51 chemical components were found when the organic solvents of ethanol, petroleum ether, and ethyl acetate were used to collect extractives, respectively. These chemical components including Phytol, CIS-5,8,11,14,17-eicosapentaenoic acid, Germacrene D, Lupeol, and ß-sitosterol, etc., have wide applications in the fields of pharmacy and cosmetics. Moreover, it was also found that extractives in ethanol and ethyl acetate had impressive UV resistance, especially for UV-C and UV-B blocking. The results showed that the maximum block ratio towards UV-C and UV-B could reach 99%. In addition, the ethanol extract showed good anti-oxidant activity with a maximum free radical scavenging rate of 96.19%. This comprehensive and systematic study on extractives from Alnus cremastogyne pods promotes the development of high-value utilization of Alnus components.

Synthesis of cellulose II-based spherical nanoparticle microcluster adsorbent for removal of toxic hexavalent chromium.

Since natural cellulose is mostly cellulose I and has a fibrous form, most cellulose-based adsorbents are fibrous/rod-shaped and exhibit the cellulose I crystal structure. This study reports a cellulose II-based spherical nanoparticle microcluster adsorbent (SNMA), synthesized from biomass by a bottom-up approach, for removing toxic hexavalent chromium (Cr(VI)). The basic structure of SNMA was investigated. Notably, the prepared adsorbent was a microcluster composed of spherical nanoparticles, while exhibiting cellulose II crystal structure, resulting in higher thermal stability and significantly enhanced adsorption performance. The adsorption process and mechanism of SNMA on Cr(VI) were studied in detail. The SNMA achieved a high adsorption capacity (225.94 mg/g) and receptor site density. The SNMA is expected to be used as a bio-based spherical nanoparticle microcluster adsorbent platform for the adsorption of different toxic substances by changing the surface functional groups of its components, spherical nanoparticles.

Preparation of flexible and UV-blocking films from lignin-containing cellulose incorporated with tea polyphenol/citric acid.

Lignin-containing bamboo cellulose, fractionated from a pilot-scale microwave liquefaction of bamboo was dissolved in tetrabutylammonium acetate/dimethyl sulfoxide (TBAA/DMSO) for the fabrication of highly flexible, transparent and UV-blocking films. Tea polyphenol (TP) or citric acid (CA) was added during the dissolving process in order to modify the film's properties. The results showed that the addition of TP obviously improved the elongation at break (triple that of the control) and UV-blocking ability of the films. Both the addition of TP and CA could increase the water contact angle of the films. The films incorporated with TP and CA were much more thermal stable than previously reported similar films. The proposed film fabrication mechanism revealed that stable hydrogen bonds formed between the lignin-cellulose matrix and TP/CA, resulting in the enhancement on the properties of the films. This present study showed that lignin-containing cellulose with the incorporation of TP/CA had great potential in the preparation of films in place of plastic.

Thermal Degradation Kinetics of Urea-Formaldehyde Resins Modified by Almond Shells.

Almond shell-modified urea-formaldehyde resins (AUF) were prepared in this study. The optimal addition amount of almond shells was selected by formaldehyde emission and wet shear strength. The activation energy (E a) values at different conversion rates and the reaction kinetics were estimated based on the Flynn-Wall-Ozawa method. The results indicated that almond shells can significantly reduce the formaldehyde emission and increase wet shear strength and thermal stability of the urea-formaldehyde resin adhesive. The optimal addition of almond shells is 3 wt %.

Kinetics and Thermodynamic Analysis of Recent and Ancient Buried Phoebe zhennan Wood.

Kinetics and thermogravimetric analysis of recent Phoebe zhennan wood (RZ) and ancient buried P. zhennan wood (ABZ) were investigated under a nitrogen atmosphere at different heating rates of 5, 10, 15, and 20 K/min. The activation energy values were estimated based on the Flynn-Wall-Ozawa model-free method, and then, the Coats-Redfern model-fitting method was used to predict the reaction mechanism. The best model of RZ for regions 1 and 2 was based on the diffusional and reaction order (second-order) mechanism, respectively, while a diffusional (Jander equation) mechanism is the best model for ABZ. The change in enthalpy and activation energy of the RZ was lower than that of the ABZ at different conversion rates. When the conversion rate was less than 0.4, the RZ may require lower thermal decomposition reaction energy, but the overall energy of thermal decomposition reactions and the degree of disorder was not much different.

Characterization of Ethyl Acetate and Trichloromethane Extracts from Phoebe zhennan Wood Residues and Application on the Preparation of UV Shielding Films.

In this work, ethyl acetate (EA) and trichloromethane (TR) extracts were extracted from Phoebe zhennan wood residues and the extracts were then applied to the preparation of UV shielding films (UV-SF). The results revealed that substances including olefins, phenols and alcohols were found in both EA and TR extracts, accounting for about 45% of all the detected substances. The two extracts had similar thermal stability and both had strong UV shielding ability. When the relative percentage of the extract is 1 wt% in solution, the extract solution almost blocked 100% of the UV-B (280-315 nm), and UV-A (315-400 nm). Two kinds of UV-SF were successfully prepared by adding the two extracts into polylactic acid (PLA) matrix. The UV-SF with the addition of 24 wt% of the extractive blocked 100% of the UV-B (280-315 nm) and more than 80% of the UV-A (315-400 nm). Moreover, the UV shielding performance of the UV-SF was still stable even after strong UV irradiation. Though the addition of extracts could somewhat decrease the thermal stability of the film, its effect on the end-use of the film was ignorable. EA extracts had less effect on the tensile properties of the films than TR extracts as the content of the extract reached 18%. The results of this study could provide fundamental information on the potential utilization of the extracts from Phoebe zhennan wood residues on the preparation of biobased UV shielding materials.

Chemical composition, UV/vis absorptivity, and antioxidant activity of essential oils from bark and leaf of phoebe zhennan S. K. Lee & F. N. Wei.

The chemical composition of essential oils (EO) from bark and leaf of P. zhennan was identified by GC-MS. The compounds of α-calacorene, τ-cadinol, ß-eudesmol and d-cadinene were found in the essential oils from both bark and leaf. The UV-Vis spectra results indicated the EO could completely absorbed the UV light at the wavelength range of 200-370 nm, revealing that EO had great potential as additives for manufacturing UV light blocking products. The radical DPPH scavenging activity assay showed that both the bark and leaf EO possessed strong DPPH radical scavenging activity of 90.25% and 82.10% respectively, which provides an important theoretical guiding in exploiting the value of P. zhennan bark and leaf.[Formula: see text].

Bio-based UV protective films prepared with polylactic acid (PLA) and Phoebe zhennan extractives.

In this study, diethyl ether extractives were isolated from Phoebe zhennan wood and then added into PLA matrix for the preparation of UV protective films (UV-PF). The results revealed that the diethyl ether extractives had good compatibility with PLA. The prepared UV-PF with the addition of 24 wt% extractives showed complete absorption of UV-C (200-280 nm) and UV-B (280-315 nm) and more than 90% absorption of UV-A (315-400 nm), indicating the addition of extractives into PLA contributed to the super UV resistant ability of the PLA based films. The UV-PF still exhibited excellent UV absorbability after strong UV light irradiation. The differential Scanning Calorimetry (DSC) analysis of the films showed that the UV-PF had relatively low thermal degradation temperature compared to the neat PLA films (PF), while the UV-PF showed stronger tensile strength with comparison to that of the PF. The results on the chemical composition analysis of the diethyl ether extractives revealed that the UV absorbability of the UV-PF may own to the benzene structure, CO bonds, CC bonds in the constituents of the extractives, which all have strong absorption in the near UV-region (200-400 nm).

Adsorptive removal of As(III) from aqueous solution by waste litchi pericarps.

The present study investigated the removal of arsenite anions (AsO33-, referred to as As(III)) from aqueous solutions by waste litchi pericarps (LPs). Influential factors such as the adsorbent dose, contact time, solution pH, and initial As(III) concentration were investigated. The optimum conditions for As(III) adsorption by the LPs occurred at a contact time of 60 min, adsorbent dose of 10.0 g/L, solution pH of 5.0, and initial As(III) concentration of 1 mg/L. A Box-Behnken design with three variables (adsorbent dose, contact time, and solution pH) at three different levels was studied to identify the correlations between the influential factors and the As(III) adsorption; the results showed a significant interaction between the adsorbent dosage and pH. Additionally, adsorption isotherms, kinetics, and thermodynamics were investigated to explore the As(III) adsorption mechanism. Adsorption by the LPs conformed to the Langmuir, Redlich-Peterson, and Koble-Corrigan isotherm models, suggesting that the process proceeds via monolayer, homogeneous adsorption. In addition, the As(III) adsorption could be characterized by a pseudo-second-order mechanism, revealing that the rate-limiting step might be chemisorption. The thermodynamic studies showed that As(III) adsorption by the LPs was spontaneous and endothermic, and disorder at the solid-liquid interface increased in the adsorption process.

Isolation and characterization of cellulose nanofibers from bamboo using microwave liquefaction combined with chemical treatment and ultrasonication.

Cellulose nanofibers were successfully isolated from bamboo using microwave liquefaction combined with chemical treatment and ultrasonic nanofibrillation processes. The microwave liquefaction could eliminate almost all the lignin in bamboo, resulting in high cellulose content residues within 7min, and the cellulose enriched residues could be readily purified by subsequent chemical treatments with lower chemical charging and quickly. The results of wet chemistry analyses, SEM images, and FTIR and X-ray spectra indicated the combination of microwave liquefaction and chemical treatment was significantly efficient in removing non-cellulosic compounds. Ultrasonication was used to separate the nanofibrils from the purified residues to extract nanofibers. The TEM images confirmed the presence of elementary fibrils, nano-sized fibril bundles, and aggregated fibril bundles. As evidenced by the TGA analysis, cellulose nanofibers isolated by this novel technique had high thermal stability indicating that the isolated nanofibers could possibly be applied as reinforcing elements in biomaterials.

Adsorption of malachite green by magnetic litchi pericarps: A response surface methodology investigation.

In this work, we synthesized a novel magnetic adsorbent containing litchi pericarps, denoted as MLP, for the removal of malachite green (MG) from solution. The factors influencing MG adsorption, such as contact time, adsorbent dosage, and initial dye concentration, were optimized using the Box-Behnken response surface methodology (RSM). The adsorption isotherms as well as the kinetics and thermodynamics of the adsorption of MG onto MLP are discussed. The results showed that MLP has a maximum adsorption efficiency of 99.5% when the temperature, pH, contact time, adsorbent dosage, and initial MG concentration were optimally set as 25 °C, 6.0, 66.69 min, 5.14 g/L, and 150 mg/L, respectively. The best model to describe this process is the Langmuir isotherm, with the maximum adsorption capacity being 70.42 mg/g. In addition, the kinetics of MG adsorption onto MLP followed a pseudo-second-order model; moreover, thermodynamic analysis suggested that MG adsorption onto MLP is spontaneous and endothermic. Finally, it was found that the new magnetic adsorbent can be separated easily and rapidly from mixed solutions in the presence of an external magnetic field.

Simultaneous removal of methylene blue and copper(II) ions by photoelectron catalytic oxidation using stannic oxide modified iron(III) oxide composite electrodes.

Stannic oxide modified Fe(III) oxide composite electrodes (SnO2/Fe2O3) were synthesized for simultaneously removing methylene blue (MB) and Cu(II) from wastewater using photoelectron catalytic oxidation (PEO). The SnO2/Fe2O3 electrodes were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoelectrochemical techniques. The removal of MB and Cu(II) by PEO using the SnO2/Fe2O3 composite electrodes was studied in terms of reaction time, electric current density, and pH of the electrolyte. The kinetics of the reactions were investigated using batch assays. The optimal reaction time, pH, and electric current density of the PEO process were determined to be 30 min, 6.0, and 10 mA/cm(2), respectively. The removal rates of MB from wastewater treated by PEO and electron catalytic oxidation process were 84.87% and 70.64%, respectively, while the recovery rates of Cu(II) were 91.75% and 96.78%, respectively. The results suggest that PEO is an effective method for the simultaneous removal of MB and Cu(II) from wastewater, and the PEO process exhibits a much higher removal rate for MB and Cu(II) compared to the electron catalytic oxidation process. Furthermore, the removal of MB was found to follow the Langmuir-Freundlich-Hinshelwood kinetic model, whereas the removal of Cu(II) fitted well to the first-order reaction model.

A novel magnetic adsorbent based on waste litchi peels for removing Pb(II) from aqueous solution.

A new magnetic bioadsorbent, magnetic litchi peel (MLP), was synthesized by coating powdered litchi peel with Fe3O4, and was used for removing Pb(II) from aqueous solutions. The influencing factors, adsorption isotherms, kinetics, and thermodynamics of Pb(II) adsorption by MLP were investigated using batch assays. Optimum Pb(II) adsorption by MLP was achieved using a contact time of 120 min, an adsorbent dose of 5 g/L, and pH of 6.0. The adsorption equilibrium data conformed to the Langmuir isotherm model, yielding a maximum Pb(II) adsorption capacity of 78.74 mg/g. The adsorption kinetics for Pb(II) adsorption by MLP followed a pseudo-second-order model. The thermodynamic results suggested that Pb(II) adsorption by MLP was spontaneous and exothermic. Additionally, the magnetic adsorbent was easily and rapidly separated out of solution under an external magnetic field.