Removal of metronidazole using a novel ZnO-CoFe2O4@Biochar heterostructure composite in an intimately coupled photocatalysis and biodegradation system under visible light.

The intimate coupling of photocatalysis and biodegradation (ICPB) technology has received much attraction because of the advantages of both photocatalytic reaction and biological treatment. In this study, ZnO-CoFe2O4@BC (ZCFC) with p-n heterojunction was prepared and used in an ICPB system to degrade metronidazole (MNZ) wastewater. The microstructure, morphology, and optical behavior of heterojunctions in ZCFC were investigated using SEM, XRD, UV-vis, FTIR, and XPS techniques. The results showed that ZCFC inherited the advantages of bamboo biochar's large pore size, and its large pore structure could provide a habitat for bacterial colonization in ICPB, thus shortening the internal mass transfer distance. The degradation of MNZ and chemical oxygen demand (COD) by the ICPB system was 86.8% and 58.5%, respectively, which was superior to single photocatalysis (72.5% for MNZ and 43.8% for COD) and single biodegradation (23.5% for MNZ and 20.1% for COD). In ICPB, photocatalysis and biodegradation showed a synergistic effect in the removal of MNZ, and the order of the major reactive oxygen species (ROS) leading to reduced toxicity of MNZ to the biofilm was •OH > h+ > O2•-. High-throughput sequencing analysis showed continuous evolution of biofilm structures in ICPB enriched a variety of functional species, among which the electroactive bacteria Alcaligenes and Brevundimonas played an important role in the degradation of MNZ. In this study, we investigated the possible mechanism of photocatalytic and microbial synergistic degradation of MNZ in the ICPB system and proposed a new technology for degrading antibiotic wastewater that combines the advantages of photocatalysis and biodegradation.

Removal of Hexamethyldisiloxane via a Novel Hydrophobic (3-Aminopropyl)Trimethoxysilane-Modified Activated Porous Carbon.

Volatile methyl siloxanes (VMS) must be removed because the formation of silica in the combustion process seriously affects the resource utilization of biogas. Herein, a series of APTMS ((3-aminopropyl)trimethoxysilane)-modified activated porous carbon (APC) adsorbents (named APTMS@APC) were prepared for VMS efficient removal. The as-prepared adsorbents were characterized using SEM, FTIR, Raman, X-ray diffraction analyses, and N2 adsorption/desorption. The results showed that the surface modification with APTMS enhanced the hydrophobicity of APC with the water contact angle increasing from 74.3° (hydrophilic) to 127.1° (hydrophobic), and meanwhile improved its texture properties with the SBET increasing from 981 to 1274 m2 g-1. The maximum breakthrough adsorption capacity of APTMS@APC for hexamethyldisiloxane (L2, model pollutant) was 360.1 mg g-1. Effects of an inlet L2 concentration (31.04-83.82 mg L-1) and a bed temperature (0-50 °C) on the removal of L2 were investigated. Meanwhile, after five adsorption-desorption cycles, the APTMS@APC demonstrated a superior cycling performance. This indicated that the hydrophobic APTMS@APC has a great significance to remove VMS.

Hexamethyldisiloxane Removal from Biogas Using a Fe3O4-Urea-Modified Three-Dimensional Graphene Aerogel.

Volatile methyl siloxanes (VMS), which are considered to be the most troublesome impurities in current biogas-cleaning technologies, need to be removed. In this study, we fabricated a series of Fe3O4-urea-modified reduced graphene-oxide aerogels (Fe3O4-urea-rGOAs) by using industrial-grade graphene oxide as the raw material. A fixed-bed dynamic adsorption setup was built, and the adsorption properties of the Fe3O4-urea-rGOAs for hexamethyldisiloxane (L2, as a VMS model pollutant) were studied. The properties of the as-prepared samples were investigated by employing various characterization techniques (SEM, TEM, FTIR, XRD, Raman spectroscopy, and N2 adsorption/desorption techniques). The results showed that the Fe3O4-urea-rGOA-0.4 had a high specific surface area (188 m2 g-1), large porous texture (0.77 cm3 g-1), and the theoretical maximum adsorption capacity for L2 (146.5 mg g-1). The adsorption capacity considerably increased with a decrease in the bed temperature of the adsorbents, as well as with an increase in the inlet concentration of L2. More importantly, the spent Fe3O4-urea-rGOA adsorbent could be readily regenerated and showed an excellent adsorption performance. Thus, the proposed Fe3O4-urea-rGOAs are promising adsorbents for removing the VMS in biogas.

New Process Combining Fe-Based Chemical Looping and Biomass Pyrolysis for Cogeneration of Hydrogen, Biochar, Bio-Oil and Electricity with In-Suit CO2 Separation.

Fe-based chemical looping gasification is a clean biomass technology, which has the advantage of reducing CO2 emissions and the potential of self-sustaining operation without supplemental heating. A novel process combining Fe-based chemical looping and biomass pyrolysis was proposed and simulated using Aspen Plus. The biomass was first subjected to pyrolysis to coproduce biochar, bio-oil and pyrolysis gas; the pyrolysis gas was subjected to an Fe looping process to obtain high-purity hydrogen and carbon dioxide. The influences of the pyrolysis reactor operating temperature and fuel reactor operation temperature, and the steam reactor and air reactor on the process performance are researched. The results showed that, under the operating condition of the established process, 23.07 kg/h of bio-oil, 24.18 kg/h of biochar, 3.35 kg/h of hydrogen and a net electricity of 3 kW can be generated from 100 kg/h of rice straw, and the outlet CO2 concentration of the fuel reactor was as high as 80%. Moreover, the whole exergy efficiency and total exergy loss of the proposed process was 58.98% and 221 kW, respectively. Additionally, compared to biomass direct chemical looping hydrogen generation technology, the new process in this paper, using biomass pyrolysis gas as a reactant in the chemical looping hydrogen generation process, can enhance the efficiency of hydrogen generation.

Egg White-Mediated Fabrication of Mg/Al-LDH-Hard Biochar Composite for Phosphate Adsorption.

Phosphorus is one of the main causes of water eutrophication. Hard biochar is considered a promising phosphate adsorbent, but its application is limited by its textural properties and low adsorption capacity. Here, an adhesion approach in a mixed suspension containing egg white is proposed for preparing the hybrid material of Mg/Al-layered double hydroxide (LDH) and almond shell biochar (ASB), named L-AE or L-A (with or without egg white). Several techniques, including XRD, SEM/EDS, FTIR and N2 adsorption/desorption, were used to characterize the structure and adsorption behavior of the modified adsorbents. The filament-like material contained nitrogen elements at a noticed level, indicating that egg white was the crosslinker that mediated the formation of the L-AE hybrid material. The L-AE had a higher phosphate adsorption rate with a higher equilibrium adsorption capacity than the L-A. The saturation phosphate adsorption capacity of L-AE was nearly three times higher than that of L-A. Furthermore, the number of surface groups and the density of the positively charged surface sites follow the ASB < L-A < L-AE order, which is consistent with their phosphate adsorption performance. The study may offer an efficient approach to improving hard biochar's adsorption performance in wastewater treatment.

Efficient Removal of Siloxane from Biogas by Using ß-Cyclodextrin-Modified Reduced Graphene Oxide Aerogels.

In this study, ß-cyclodextrin-modified reduced graphene oxide aerogels (ß-CD-rGOAs) were synthesized via a one-step hydrothermal method and were used to remove hexamethyldisiloxane (L2) from biogas. The ß-CD-rGOAs were characterized by the Brunner-Emmet-Teller technique, using Fourier-transform infrared spectroscopy, Raman spectrometry, scanning electron microscopy (SEM), contact angle measurements, and X-ray diffraction. The results of the characterizations indicate that ß-CD was grafted onto the surface of rGOAs as a cross-linking modifier. The ß-CD-rGOA had a three-dimensional, cross-linked porous structure. The maximum breakthrough adsorption capacity of L2 on ß-CD-rGOA at 273 K was 111.8 mg g-1. A low inlet concentration and bed temperature facilitated the adsorption of L2. Moreover, the ß-CD-rGOA was regenerated by annealing at 80 °C, which renders this a promising material for removing L2 from biogas.

Reactive Adsorption Performance and Behavior of Gaseous Cumene on MCM-41 Supported Sulfuric Acid.

Efficient removal of cumene from gaseous streams and recovery of its derivatives was accomplished using a MCM-41-supported sulfuric acid (SSA/MCM-41) adsorbent. The results indicated that the removal performance of the SSA/MCM-41 for cumene was significantly influenced by the process conditions such as bed temperature, inlet concentration, bed height, and flow rate. The dose-response model could perfectly describe the collected breakthrough adsorption data. The SSA/MCM-41 adsorbent exhibited a reactive temperature region of 120-170 °C, in which the cumene removal ratios (Xc) were greater than 97%. Rising the bed height or reducing the flow rate enhanced the theoretical adsorption performance metrics, such as theoretical breakthrough time (tB,th) and theoretical breakthrough adsorption capacity (QB,th), whereas increasing the inlet concentration resulted in tB,th shortening and QB,th rising. As demonstrated in this paper, the highest tB,th and QB,th were 69.60 min and 324.50 mg g-1, respectively. Meanwhile, the spent SSA/MCM-41 could be desorbed and regenerated for cyclic reuse. Moreover, two recoverable adsorbed products, 4-isopropylbenzenesulfonic acid and 4, 4'-sulfonyl bis(isopropyl-benzene), were successfully separated and identified using FTIR and 1H/13C NMR characterization. Accordingly, the relevance of a reactive adsorption mechanism was confirmed. This study suggests that the SSA/MCM-41 has remarkable potential for application as an adsorbent for the resource treatment of cumene pollutants.

Utilization of Hematite Particles for Economical Removal of o-xylene in a High-Temperature Gas-Solid Reactor.

To establish a novel approach for VOCs resource utilization, coupled o-xylene oxidation and hematite reduction was investigated in this study in a high-temperature gas-solid reactor in the temperature range 300-700 °C. As the o-xylene-containing inert gas (N2) stream traveled through the hematite particle bed, its reaction behavior was determined in programmed heating and constant temperature modes. Consequently, the effect of bed temperature, flow rate and o-xylene inlet concentration on both o-xylene removal performance and degree of hematite reduction was studied. The raw hematite and solid products were analyzed by TGA, XRF, XRD and SEM-EDS. The results showed that a temperature above 300 °C was required to completely eliminate o-xylene by hematite, and both o-xylene removal capacity and degree of hematite reduction at 5% breakthrough points enhanced on increasing the temperature and decreasing the flow rate. The increment in temperature from 300 °C to 700 °C led to a gradual reduction of Fe2O3 to Fe3O4, FeO and metallic iron. Thus, this study provides a novel, economic and promising technology for treating the VOC pollutants.

Fabrication of magnetic CuFe2O4@PBC composite and efficient removal of metronidazole by the photo-Fenton process in a wide pH range.

CuFe2O4-coated pretreated biochars (CuFe2O4@PBC) were synthesized for the first time via a facile method by impregnating and calcinating Cu-Fe-ethanol solution to activate H2O2 for the degradation of metronidazole (MNZ) at a wide pH range. CuFe2O4@PBC samples were characterized by XRD, SEM, VSM, XPS, and BET. The results showed that CuFe2O4 coating, which is evenly distributed on the surface of HNO3-pretreated biochar, can provide more active sites to enable CuFe2O4@PBC to be activated by visible light. The introduction of biochar by impregnating and calcinating method effectively suppressed the aggregation of CuFe2O4 and maintained its high surface area and pore structure. CuFe2O4@PBC composite can be separated easily by an external magnetic field. The PBC-400CuFe sample calcined under 400 °C showed superior photo-Fenton catalytic ability in MNZ degradation at a wide pH range (pH = 3-7) and exhibited high-efficiency degradation of about 96.3% with the dosage concentration of catalyst 0.4 g/L in the presence of H2O2 at pH 3.0 within 60 min. While, at pH 7.0, the PBC-400CuFe material removed 91.1% MNZ within 120 min, and the degradation efficiency was still higher than that of traditional Fenton reaction and some Fenton-like reaction. The PBC-400CuFe showed good stability. After 5 times of repeated use, its removal rate was still above 89.1%. This study confirmed that O2•- and h+ are both important radicals, but the •OH played a key role in the visible photo/CuFe2O4@PBC- H2O2 system. The results indicate that CuFe2O4@PBC is highly suitable for the wastewaters with high MNZ content under mild conditions.

The Effects of Hydrophobicity and Textural Properties on Hexamethyldisiloxane Adsorption in Reduced Graphene Oxide Aerogels.

To expand the applications of graphene-based materials to biogas purification, a series of reduced graphene oxide aerogels (rGOAs) were prepared from industrial grade graphene oxide using a simple hydrothermal method. The influences of the hydrothermal preparation temperature on the textural properties, hydrophobicity and physisorption behavior of the rGOAs were investigated using a range of physical and spectroscopic techniques. The results showed that the rGOAs had a macro-porous three-dimensional network structure. Raising the hydrothermal treatment temperature reduced the number of oxygen-containing groups, whereas the specific surface area (SBET), micropore volume (Vmicro) and water contact angle values of the rGOAs all increased. The dynamic adsorption properties of the rGOAs towards hexamethyldisiloxane (L2) increased with increasing hydrothermal treatment temperature and the breakthrough adsorption capacity showed a significant linear association with SBET, Vmicro and contact angle. There was a significant negative association between the breakthrough time and inlet concentration of L2, and the relationship could be reliably predicted with a simple empirical formula. L2 adsorption also increased with decreasing bed temperature. Saturated rGOAs were readily regenerated by a brief heat-treatment at 100 °C. This study has demonstrated the potential of novel rGOA for applications using adsorbents to remove siloxanes from biogas.

Structural Tunability on Naphthalimide-Based Dendrimer Gelators via Glaser Coupling Interaction with Tailored Gelation Solvent Polarity and Stimuli-Responsive Properties.

To date, most of the low-molecular-weight gels are found serendipitously, and modification on known gelator structures via organic synthesis is an efficient methodology to prepare gel series. However, a simple, direct, and rational modification method for a known gelator is still a challenge. Herein, we employ Glaser coupling reaction to synthesize a novel dendrimer gelator BisDEC with the (ALS2)2 structure, starting from terminal alkyne-based gelator DEC with the ALS2 structure. This structural change results in gels with distinct gelation solvents, mechanical properties, and stimuli-responsive abilities. The gelation abilities of DEC and BisDEC in nonpolar and polar solvents, respectively, have been examined and discussed by several experiments and Hansen constants. It is also shown that the BisDEC gel system shows intriguing self-healing, self-supporting, and grinding chromism properties.

A comparative study of the removal of o-xylene from gas streams using mesoporous silicas and their silica supported sulfuric acids.

The three types of silica supported sulfuric acids (SSA), with the same sulfuric acid loading of 9.25 mmol g-1, were prepared by a wet impregnation method from silica gel (SG), SBA-15 and MCM-41. Characterization of the prepared SSA showed that two anchoring states coexisted for sulfuric acid supported on the surface of the silicas: A physiosorbed (P)-state sulfuric acid; and a chemically bonded (C)-state sulfuric acid. Dynamic adsorption results showed that each SSA had a significant removal capacity for o-xylene gas in the reactive temperature regions. The ranges of the reactive regions were 120-220 °C (SSA/SG), 120-230 °C (SSA/SBA-15) and 120-250 °C (SSA/MCM-41), and this could be attributed to the sulfonation reaction between o-xylene and the anchored sulfuric acid. SSA/MCM-41 showed the highest theoretical breakthrough adsorption capacity (QB, th, 526.71 mg g-1) compared with SSA/SBA-15 (363.54 mg g-1) and SSA/SG (239.15 mg g-1). QB, th was closely associated with the amount or proportion of the C-state sulfuric acid on the surface of each SSA. Optimum breakthrough time and QB, th was obtained by increasing the bed height and decreasing flow rate and inlet concentration. The SSA exhibited excellent recyclability and reuse performance over eight consecutive adsorption/desorption/regeneration cycles. The results suggested that the SSA, especially SSA/MCM-41, might have good potential in applications using adsorbents for the removal of BTEX pollutants.

Study on the Adsorption of CuFe2O4-Loaded Corncob Biochar for Pb(II).

A series of the magnetic CuFe2O4-loaded corncob biochar (CuFe2O4@CCBC) materials was obtained by combining the two-step impregnation of the corncob biochar with the pyrolysis of oxalate. CuFe2O4@CCBC and the pristine corncob biochar (CCBC) were characterized using XRD, SEM, VSM, BET, as well as pHZPC measurements. The results revealed that CuFe2O4 had a face-centered cubic crystalline phase and was homogeneously coated on the surface of CCBC. The as-prepared CuFe2O4@CCBC(5%) demonstrated a specific surface area of 74.98 m2·g-1, saturation magnetization of 5.75 emu·g-1 and pHZPC of 7.0. The adsorption dynamics and thermodynamic behavior of Pb(II) on CuFe2O4@CCBC and CCBC were investigated. The findings indicated that the pseudo-second kinetic and Langmuir equations suitably fitted the Pb(II) adsorption by CuFe2O4@CCBC or CCBC. At 30 °C and pH = 5.0, CuFe2O4@CCBC(5%) displayed an excellent performance in terms of the process rate and adsorption capacity towards Pb(II), for which the theoretical rate constant (k2) and maximum adsorption capacity (qm) were 7.68 × 10-3 g·mg-1··min-1 and 132.10 mg·g-1 separately, which were obviously higher than those of CCBC (4.38 × 10-3 g·mg-1·min-1 and 15.66 mg·g-1). The thermodynamic analyses exhibited that the adsorption reaction of the materials was endothermic and entropy-driven. The XPS and FTIR results revealed that the removal mechanism could be mainly attributed to the replacement of Pb2+ for H+ in Fe/Cu-OH and -COOH to form the inner surface complexes. Overall, the magnetic CuFe2O4-loaded biochar presents a high potential for use as an eco-friendly adsorbent to eliminate the heavy metals from the wastewater streams.

Determination of berberine in Rhizoma coptidis using a ß-cyclodextrin-sensitized fluorescence method.

In this work, a method for the determination of berberine in Rhizoma coptidis using ß-cyclodextrin-sensitized fluorescence technology is established. Berberine is the main extract of Rhizoma coptidis, a medicinal material, which causes an envelope reaction with ß-cyclodextrin to generate fluorescence sensitization. In the environment of its own aqueous extract, with 0.0065 mol L-1 of ß-cyclodextrin, a fluorescence excitation wavelength (λ ex) of 345 nm and an emission wavelength (λ em) of 540 nm were selected to avoid interference from other distractors. The fluorescent sensor for the detection of berberine exhibits a low limit of detection (3.59 × 10-9 mol L-1) and a wide linear range from 2.7 × 10-7 mol L-1 to 2.7 × 10-6 mol L-1. Our sensor can be also used to detect berberine in real medicinal materials. The content of berberine in Rhizoma coptidis medicinal material was found to be 7.60% using this method with an average recovery rate of 99.5%. The result obtained by thin-layer chromatography with fluorescence detection was 7.61%, which is consistent with the result from the ß-cyclodextrin sensitized fluorescence method. This method is simple and environmentally friendly with high sensitivity and good selectivity and gives reliable results, which is promising for practical application.

Immobilization of TiO2 Nanoparticles on Chlorella pyrenoidosa Cells for Enhanced Visible-Light-Driven Photocatalysis.

TiO2 nanoparticles are immobilized on chlorella cells using the hydrothermal method. The morphology, structure, and the visible-light-driven photocatalytic activity of the prepared chlorella/TiO2 composite are investigated by various methods. The chlorella/TiO2 composite is found to exhibit larger average sizes and higher visible-light intensities. The sensitization of the photosynthesis pigment originating from chlorella cells provides the anatase TiO2 with higher photocatalytic activities under the visible-light irradiation. The latter is linked to the highly efficient charge separation of the electron/hole pairs. The results also suggest that the photocatalytic activity of the composite remains substantial after four cycles, suggesting a good stability.

Catalytic ozonation of sulfosalicylic acid over manganese oxide supported on mesoporous ceria.

Manganese oxide supported on mesoporous ceria was prepared and used as catalyst for catalytic ozonation of sulfosalicylic acid (SA). Characterization results indicated that the manganese oxide was mostly incorporated into the pores of ceria. The synthesized catalyst exhibited high activity and stability for the mineralization of SA in aqueous solution by ozone, and more than 95% of total organic carbon was removed in 30 min under various conditions. Mechanism studies indicated that SA was mainly degraded by ozone molecules, and hydroxyl radical reaction played an important role for the degradation of its ozonation products (small molecular organic acids). The manganese oxide in the pores of CeO2 improved the adsorption of small molecular organic acids and the generation of hydroxyl radicals from ozone decomposition, resulting in high TOC removal efficiency.

Sugar based nanotube assembly for the construction of sonication triggered hydrogel: an application of the entrapment of tetracycline hydrochloride.

A sugar functionalized naphthalimide derivative (H1) self-assembles into supramolecular nanotubes (25 nm pore diameter) by the reaction of 4-N-ethylaminenaphthalimide-N-propinyl and delta-gluconolactone in refluxed ethanol. The suspension of the tube assembly in water can directly form hydrogels when triggered by sonication, without change in morphology or molecular aggregates in the pH range of 5-8. Modified with aminocarproic acid, H2 with more hydrogen bonding sites can form pH tolerant hydrogels in the widest range of pH values from 1-14 accelerated by sonication. The gelation mechanism was studied in detail. To the best of our knowledge, this is the first paradigm wherein hydrogels were constructed from naphthalimide derivatives. Finally, the potential of the hydrogel as a drug delivery and release system for hydrophilic medicine was explored.

An "off-on" fluorescent and colorimetric probe bearing fluorescein moiety for Mg(2+) and Ca(2+) via a controlled supramolecular approach.

In the present work, a new kind of fluorescein-based chemosensor L was designed and synthesized to selectively recognize Ca(2+) or Mg(2+) over other competing ions. The chemosensor showed "off-on" fluorescent and color changes upon the addition of Ca(2+) and Mg(2+). The dynamic binding events with the formation of 1:1(L/M) and 1:2(L/M) complexes were examined. The cation-driven conformation changes of L were understood and proposed rationally by the UV-vis, FL, and (1)HNMR titrations. By this allosteric effect, Ca(2+) and Mg(2+) could be selectively recognized with the 1:2 stoichiometry by fluorescent changes, which were different from other known reports on chemosensors that the host-cation complexion was exploited for controlling chromophore interaction as the model of signaling.

Intramolecular proton transfer through the adjoining π-conjugated system in Shiff base: application for colorimetric sensing of fluoride anion.

In this paper, a new kind of phenol-based chemsensor L2 comprised of a Schiff base and azo groups was rationally designed and synthesized. It could selectively recognize fluoride anion among tested anions such as F(-), AcO(-), H2PO4(-), Cl(-), Br(-), and I(-) with obvious color changes from yellow to fuchsia. The intramolecular PT (proton transfer) in L1 and L2 was responsible for the sensing ability, which was certified by the (1)H NMR and Uv-vis experiments.

Synthesis of MnFe2O4@Mn-Co oxide core-shell nanoparticles and their excellent performance for heavy metal removal.

Magnetic nanomaterials that can be easily separated and recycled due to their magnetic properties have received considerable attention in the field of water treatment. However, these nanomaterials usually tend to aggregate and alter their properties. Herein, we report an economical and environmentally friendly method for the synthesis of magnetic nanoparticles with core-shell structure. MnFe2O4 nanoparticles have been successfully coated with amorphous Mn-Co oxide shells. The synthesized MnFe2O4@Mn-Co oxide nanoparticles have highly negatively charged surface in aqueous solution over a wide pH range, thus preventing their aggregation and enhancing their performance for heavy metal cation removal. The adsorption isotherms are well fitted to a Langmuir adsorption model, and the maximal adsorption capacities of Pb(II), Cu(II) and Cd(II) on MnFe2O4@Mn-Co oxide are 481.2, 386.2 and 345.5 mg g(-1), respectively. All the metal ions can be completely removed from the mixed metal ion solutions in a short time. Desorption studies confirm that the adsorbent can be effectively regenerated and reused.