Lan S, Chen Y, Zeng L, Ji H, Liu W, Zhu M. Piezo-activation of peroxymonosulfate for benzothiazole removal in water. Journal of Hazardous Materials [Internet]. 2020;393:122448. 访问链接Abstract
Piezoelectricity, as a kind of physical phenomenon, is a coupling between a material’s mechanical and electrical behavior. Herein, the local accumulated charges on the surface of piezoelectric material were used to break OO bond of peroxymonosulfate (PMS) to induce its activation for the benzothiazole (BTH) removal. Taking BaTiO3 as a model piezocatalyst, up to 97 % of BTH was degraded within 30 min in BaTiO3/PMS/force system, which was respective 40 %, 79 %, 83 % higher than that in BaTiO3/force piezocatalysis, force/PMS oxidation, and BaTiO3/PMS adsorption. A significant synergistic effect was observed since the reaction rate constant of BaTiO3/PMS/force was 3 times higher than the sum of those later three processes. The possible activated mechanism was proposed based on reactive species analysis, DFT calculation and LCMS determination. The stability of the piezocatalyst and the treatment performance for real wastewater were studied to investigate the potential in practical applicability. All the results demonstrated that the BaTiO3 piezoelectricity can efficiently activate PMS to enhance BTH removal, which is a promising strategy for PMS activation, as well as a valuable insight for the piezoelectrical application in wastewater remediation.
Duan J, Ji H, Zhao X, Tian S, Liu X, Liu W, Zhao D. Immobilization of U(VI) by stabilized iron sulfide nanoparticles: Water chemistry effects, mechanisms, and long-term stability. Chemical Engineering Journal [Internet]. 2020;393:124692. 访问链接Abstract
Carboxymethyl cellulose stabilized iron sulfide (CMC-FeS) nanoparticles have been shown promising for reductive immobilization of U(VI) in water and soil. This work aimed to fill some critical knowledge gaps on the effects of the stabilizer and water chemistry, reaction mechanisms, and long-term stability of stabilized uranium. The optimal CMC-to-FeS molar ratio was determined to be 0.0010. CMC-FeS performed effectively over pH 6.0–9.0, with the best removal being at pH 7.0 and 8.0. The retarded first-order model adequately interpreted the kinetic data, representing a mechanistically sounder model for heterogeneous reactants of decaying reactivity. The presence of Ca2+ (1 mM) or bicarbonate (1 mM) lowered the initial rate constant by a factor of 1.6 and 9.5, respectively, while 1 mM of Na+ showed negligible effect. Humic acid at 1.0 mg/L (as total organic carbon) doubled the removal rate, but inhibited the removal at elevated concentrations (≥5.0 mg/L). Fourier transform infrared spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, and extraction studies indicated that reductive conversion of UO22+ to UO2(s) was the primary reaction mechanism, accounting for  90% of U removal at pH 7.0. S2− and S22− were the primary electron sources, whereas sorbed and structural Fe(II) acted as supplementary electron donors. The immobilized U remained stable under anoxic conditions after 180 days of aging, while  26% immobilized U was remobilized when exposed to air for 180 days. The long-term stability is attributed to the protective reduction potential of CMC-FeS, the formation of uraninite and associated structural resistance to oxidation, and the high affinity of FeS oxidation products toward U(VI).
Jiang H, Dang C, Liu W, Wang T. Radical attack and mineralization mechanisms on electrochemical oxidation of p-substituted phenols at boron-doped diamond anodes. Chemosphere [Internet]. 2020;248:126033. 访问链接Abstract
Degradation of phenols with different substituent groups (including –OCH3, –CHO, –NHCOCH3, –NO2, and −Cl) at boron-doped diamond (BDD) anodes has been studied previously based on the removal efficiency and •OH detection. Innovatively, formations of CO2 gas and various inorganic ions were examined to probe the mineralization process combined with quantitative structure-activity relationship (QSAR) analysis. As results, all phenols were efficiently degraded within 8 h with high COD removal efficiency. Three primary intermediates (hydroquinone, 1,4-benzoquinone and catechol) were identified during electrochemical oxidation and degradation pathway was proposed. More importantly, CO2 transformation efficiency ranked as: no N or Cl contained phenols (p-CHO, p-OCH3 and Ph) > N-contained phenols (p-NHCOCH3 and p-NO2) > Cl-contained phenols (p-Cl and o,p-Cl). Carbon mass balance study suggested formation of inorganic carbon (H2CO3, CO32− and HCO3−) and CO2 after organic carbon elimination. Inorganic nitrogen species (NH4+, NO3− and NO2−) and chlorine species (Cl−, ClO3− and ClO4−) were also formed after N- and Cl-contained phenols mineralization, while no volatile nitrogen species were detected. The phenols with electron-withdrawing substituents were easier to be oxidized than those with electron-donating substituents. QSAR analysis indicated that the reaction rate constant (k1) for phenols degradation was highly related to Hammett constant (∑σo,m,p) and energy gap (ELUMO - EHOMO) of the compound (R2 = 0.908), which were key parameters on evaluating the effect of structural moieties on electronic character and the chemical stability upon radical attack for a specific compound. This study presents clear evidence on mineralization mechanisms of phenols degradation at BDD anodes.
Dang C, Xia Y, Zheng M, Liu T, Liu W, Chen Q, Ni J. Metagenomic insights into the profile of antibiotic resistomes in a large drinking water reservoir. Environment International [Internet]. 2020;136:105449. 访问链接Abstract
Reservoirs play a vital role in the control and management of surface water resources. However, the long water residence time in the reservoir potentially increases the storage and accumulation of antibiotic resistant genes (ARGs). The full profiles and potential health risks of antibiotic resistomes in reservoirs are largely unknown. In this study, we investigated the antibiotic resistomes of water and sediment during different seasons in the Danjiangkou Reservoir, which is one of the largest reservoirs in China, using a metagenomic sequencing approach. A total of 436 ARG subtypes belonging to 20 ARG types were detected from 24 water and 18 sediment samples, with an average abundance of 0.138 copies/cell. The overall ARG abundance in the sediment was higher than that in the water, and bacitracin and vancomycin resistance genes were the predominant ARG types in the water and sediment, respectively. The overall ARG abundance in the dry season was higher than that in the wet season, and a significant difference in ARG subtype compositions was observed in water, but not in the sediment, between the different seasons. The potential horizontal gene transfer frequency in the water was higher than that in the sediment, and the ARGs in water mainly came from the sediment upstream of the reservoir. The metagenomic assembly identified 14 contigs as ARG-carrying pathogens including Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa, and 3 of 14 carried virulence factors. Overall, the potential public health risks posed by resistomes in the water of the Danjiangkou Reservoir were higher in the dry season than in the wet season. Based on these results, strategies including sediment control and pathogen monitoring are suggested for water safety management in drinking water reservoirs.
Tong M, Liu F, Dong Q, Ma Z, Liu W. Magnetic Fe3O4-deposited flower-like MoS2 nanocomposites for the Fenton-like Escherichia coli disinfection and diclofenac degradation. Journal of Hazardous Materials [Internet]. 2020;385:121604. 访问链接Abstract
Fenton reaction can disinfect bacteria and degrade organic pollutants via the generation of OH through the reaction of Fe(II) and H2O2. However, its high efficiency only at very acidic conditions and the formation of Fe(III) sludge limit its practical application. Herein, magnetic Fe3O4-deposited flower-like MoS2 (MF) composites were fabricated to disinfect Escherichia coli and degrade diclofenac (DCF) with addition of small amount of H2O2 at a wide pH range (from 3.5 to 9.5). MF can efficiently inactivate bacteria and remove DCF at broad pH from 3.5 to 9.5. For example, 1.2 × 106 CFU mL-1 cells are completely disinfected by MF in 30 min at pH 6 with 5 mM H2O2, while 10 mg L-1 DCF is fully degraded in 7 min at pH 6 with 1 mM H2O2. MoS2 facilitates the conversion cycle of Fe(III)/Fe(II) and improves the generation of OH. MF can be easily collected by magnet after use. Confocal image, SEM images, the leakage of K+ and DNA were employed to determine the damage of cell membrane. Meanwhile, the theoretical density functional theory and the degradation intermediates determination were employed to provide the degradation pathway of DCF. MF exhibit excellent reusability and good catalytic performance towards sanitary sewage.
Li Y-X, Fu H, Wang P, Zhao C, Liu W, Wang C-C. Porous tube-like ZnS derived from rod-like ZIF-L for photocatalytic Cr(VI) reduction and organic pollutants degradation. Environmental Pollution [Internet]. 2020;256:113417. 访问链接Abstract
A facile method was developed to fabricate porous tube-like ZnS by sulfurizing rod-like ZIF-L with thioacetamide (TAA) at different durations and the formation mechanism of the porous tube-like ZnS was discussed in detail. The series of sulfide products (ZS-X) were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance spectroscopy (SSNMR), transmission electron microscopy (TEM), UV–visible diffuse-reflectance spectroscopy (UV–vis DRS). The photocatalytic performances of ZS-X toward Cr(VI) reduction and organic pollutant degradation were explored. It was discovered that ZS-3 (porous tube-like ZnS) exhibited excellent activities under UV light and displayed good reusability and stability after several experimental cycles. In addition, Cr(VI) reduction and organic pollutant degradation were investigated under different pH values and existence of different foreign ions. The photocatalytic activities of ZS-3 were tested toward the matrix of Cr(VI) and reactive red X–3B. The mechanism was proposed and verified by both electrochemical analysis and electron spin resonance (ESR) measurement.
Ji H, Xie W, Liu W, Liu X, Zhao D. Sorption of dispersed petroleum hydrocarbons by activated charcoals: Effects of oil dispersants. Environmental Pollution [Internet]. 2020;256:113416. 访问链接Abstract
Marine oil spill often causes contamination of drinking water sources in coastal areas. As the use of oil dispersants has become one of the main practices in remediation of oil spill, the effect of oil dispersants on the treatment effectiveness remains unexplored. Specifically, little is known on the removal of dispersed oil from contaminated water using conventional adsorbents. This study investigated sorption behavior of three prototype activated charcoals (ACs) of different particle sizes (4–12, 12–20 and 100 mesh) for removal of dispersed oil hydrocarbons, and effects of two model oil dispersants (Corexit EC9500A and Corexit EC9527A). The oil content was measured as n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and total petroleum hydrocarbons (TPHs). Characterization results showed that the smallest AC (PAC100) offered the highest BET surface area of 889 m2/g and pore volume of 0.95 cm3/g (pHPZC = 6.1). Sorption kinetic data revealed that all three ACs can efficiently adsorb Corexit EC9500A and oil dispersed by the two dispersants (DWAO-I and DWAO-II), and the adsorption capacity followed the trend: PAC100 > GAC12 × 20 > GAC4 × 12. Sorption isotherms confirmed PAC100 showed the highest adsorption capacity for dispersed oil in DWAO-I with a Freundlich KF value of 10.90 mg/g∙(L/mg)1/n (n = 1.38). Furthermore, the presence of Corexit EC9500A showed two contrasting effects on the oil sorption, i.e., adsolubilization and solubilization depending on the dispersant concentration. Increasing solution pH from 6.0 to 9.0 and salinity from 2 to 8 wt% showed only modest effect on the sorption. The results are useful for effective treatment of dispersed oil in contaminated water and for understanding roles of oil dispersants.
Ji H, Du P, Zhao D, Li S, Sun F, Duin EC, Liu W. 2D/1D graphitic carbon nitride/titanate nanotubes heterostructure for efficient photocatalysis of sulfamethazine under solar light: Catalytic “hot spots” at the rutile–anatase–titanate interfaces. Applied Catalysis B: Environmental [Internet]. 2020;263:118357. 访问链接Abstract
2D/1D graphitic carbon nitride hybridized with titanate nanotubes (g-C3N4/TNTs) was prepared through a hydrothermal reaction–calcination method. The photocatalyst exhibited high degradation efficiency for sulfamethazine (SMT) through photocatalysis under simulated solar light. The optimized material was composed of anatase, rutile, titanate and g-C3N4 crystalline phases. In situ transformation of titanate to anatase and rutile with specific content proportion (∼80:20, P25-type composition) leaded to formation of nanoscale “hot spots” at rutile–anatase–titanate interfaces, and then subsequent charge transfer occurred. Large specific surface area of TNTs as skeleton resulted in high-efficient interface reaction, while heterojunction with g-C3N4 further extended the adsorption to visible light region and retarded electron-hole pairs recombination. Density functional theory (DFT) calculation indicated the SMT sites with high Fukui nucleophilic (f-) index prefered to be attacked by radacils. Reduced toxicity of SMT degradation intermediates, good reusability and stability of g-C3N4/TNTs all suggested the great application potential in practical water treatment area.
Zhao C, Liao Z, Liu W, Liu F, Ye J, Liang J, Li Y. Carbon quantum dots modified tubular g-C3N4 with enhanced photocatalytic activity for carbamazepine elimination: Mechanisms, degradation pathway and DFT calculation. Journal of Hazardous Materials [Internet]. 2020;381:120957. 访问链接Abstract
A novel tubular graphitic carbon nitride (g-C3N4) modified with carbon quantum dots (CQDs) was fabricated and employed for the elimination of carbamazepine (CBZ) under visible light irradiation. The as-fabricated metal-free catalysts exhibited tubular morphologies due to the preforming of tubular protonated melamine with CQDs surface adsorption as the polymerization precursors. The surface bonded CQDs did not alter the band gap structure of g-C3N4, but greatly inhibited the charge recombination. Therefore, the CBZ degradation kinetics of tubular g-C3N4 were increased by over 5 times by the incorporation of CQDs. The main active species for CBZ degradation were found to be superoxide radical (O2−) and photo-generated holes (h+), which were further confirmed by electron spin resonance (ESR) analysis. In addition, the degradation pathways of CBZ were clarified via intermediates identification and quantum chemical computation using density functional theory (DFT) and wave function analysis. The olefinic double bond with the highest condensed Fukui index (f 0 = 0.108) in CBZ molecule was found to be the most preferable sites for radical attack. Moreover, good stability of the as-prepared photocatalysts was observed in the consecutive recycling cycles, while the slight decline of photocatalytic activity was attributed to the minimal surface oxidation.
Lin Y, Ma J, Liu W, Li Z, He K. Efficient removal of dyes from dyeing wastewater by powder activated charcoal/titanate nanotube nanocomposites: adsorption and photoregeneration. Environmental Science and Pollution Research [Internet]. 2019;26:10263–10273. 访问链接Abstract
Effective removal of dyes has been widely investigated by the adsorption of powder activated carbon and photodegradation by titanate nanotubes (TNTs). In this study, a facile one-step alkaline-hydrothermal method was applied to synthesize powder activated charcoal–supported TNTs (TNTs@PAC). Adsorption of three representative dyes, i.e., cationic methylene blue (MB), cationic rhodamine B (RhB), and anionic methyl orange (MO), onto TNTs@PAC was evaluated by the adsorption kinetic experiments and adsorption isotherms. The first 30 min is the main time phase of adsorption, and MB, RhB, and MO obtained the experimental equilibrium uptake of 173.30, 115.06, and 106.85 mg/g, respectively, indicating their final removal efficiencies of 100%, 69.36%, and 64.11%, respectively. The increase of pH value reduced adsorption capacity of MO (from 149.35 mg/g at pH of 2 to 96.99 mg/g at pH of 10), but facilitated MB adsorption, which was attributed to the charge distribution on the surface of TNTs@PAC and the charge of dyes at different pH. Furthermore, good capacity recoveries of MB by TNTs@PAC (>þinspace}99%) were observed after UV irradiation treatment, indicating the used TNTs@PAC can be easily recycled for the adsorption of MB by UV irradiation. Overall, TNTs@PAC is an effective process for remediation of dye-contaminated water because of its adsorption performance for all selected dyes and good regeneration capacity for MB.
Zhang M, Yi K, Zhang X, Han P, Liu W, Tong M. Modification of zero valent iron nanoparticles by sodium alginate and bentonite: Enhanced transport, effective hexavalent chromium removal and reduced bacterial toxicity. Journal of Hazardous Materials [Internet]. 2019:121822. 访问链接Abstract
The rapid aggregation/sedimentation and decreased transport of nanoscale zero-valent iron (nZVI) particles limit their application in groundwater remediation. To decrease the aggregation/sedimentation and increase the transport of nZVI, sodium alginate (a natural polysaccharide) and bentonite (one type of ubiquitous clay) were employed to modify nZVI. Different techniques were utilized to characterize the modified nZVI. We found that modification with either sodium alginate or bentonite could disperse nZVI and shifted their zeta potentials from positive to negative. Comparing with the bare nZVI, the sedimentation rates of modified nZVI either by sodium alginate or bentonite are greatly decreased and their transport are significantly increased. The transport of modified nZVI can be greatly increased by increasing flow rate. Furthermore, Cr(VI) can be efficiently removed by the modified nZVI (both sodium alginate and bentonite modified nZVI). Comparing with bare nZVI, the two types of modified nZVI contain lower toxicities to Escherichia coli. The results of this study indicate that both sodium alginate and bentonite can be employed as potential stabilizers to disperse nZVI and improve their application feasibility for in situ groundwater remediation.
Ji H, Zhu Y, Duan J, Liu W, Zhao D. Reductive immobilization and long-term remobilization of radioactive pertechnetate using bio-macromolecules stabilized zero valent iron nanoparticles. Chinese Chemical Letters [Internet]. 2019;30:2163 - 2168. 访问链接Abstract
Reductive immobilization of radioactive pertechnetate (99TcO4−) in simulated groundwater was studied by prepared carboxymethyl cellulose (CMC) and starch stabilized zero valent iron nanoparticles (nZVI), and long-term remobilization of reduced Tc was also evaluated under anoxic and oxic conditions. The stabilized nZVI can effectively reduce soluble 99Tc(VII) to insoluble 99Tc(IV), and they can be easily delivered into a contaminated groundwater zone and facilitate in situ remediation. In this study, CMC-stabilized nZVI showed higher reactivity than that using starch as the stabilizer. Batch experiments indicated that more than 99% of 99Tc(VII) (C0=12mg/mL) was reduced and removed from groundwater by CMC-stabilized nZVI with a CMC content of 0.2% (w/w) at a broad pH of 5–8. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses further confirmed that 99Tc(VII)O4− transformed into 99Tc(IV)O2 (s). The presence of bicarbonate exhibited insignificant effect on Tc immobilization, while humic acid (HA) inhibited reaction mainly due to retardation on electron transfer and formation of Tc(IV)-HA complexes. More interesting, the immobilized Tc(IV) remained insoluble even after 120 d under anoxic condition, while only ∼21% was remobilized when exposed to air. Therefore, bio-macromolecules stabilized nZVI nanoparticles could be a viable alternative for in situ remediation of radioactive contamination in groundwater.
Liu W, Zhang W, Liu M, Du P, Dang C, Liang J, Li Y. Fabrication of niobium doped titanate nanoflakes with enhanced visible-light-driven photocatalytic activity for efficient ibuprofen degradation. Chinese Chemical Letters [Internet]. 2019;30:2177 - 2180. 访问链接Abstract
In this study, a novel class of niobium (Nb) doped titanate nanoflakes (TNFs) are fabricated through a one-step hydrothermal method. Nb doping affects the curving of titanate nanosheet, leading to the formation of nanoflake structure. In addition, Nb5+ filled in the interlayers of [TiO6] alters the light adsorption property of pristine titanate. The band gap of Nb-TNFs is narrowed to 2.85 eV, while neat titanate nanotubes (TNTs) is 3.4 eV. The enhanced visible light adsorption significantly enhances the visible-light-driven activity of Nb-TNFs for ibuprofen (IBP) degradation. The pseudo-first order kinetics constant for Nb-TNFs is calculated to be 1.04 h−1, while no obvious removal is observed for TNTs. Photo-generated holes (h+) and hydroxyl radicals (OH) are responsible for IBP degradation. The photocatalytic activity of Nb-TNFs depends on pH condition, and the optimal pH value is found to be 5. In addition, Nb-TNFs exhibited superior photo-stability during the reuse cycles. The results demonstrated Nb-TNFs are very promising in photocatalytic water purification.
Ma M, Chen L, Zhao J, Liu W, Ji H. Efficient activation of peroxymonosulfate by hollow cobalt hydroxide for degradation of ibuprofen and theoretical study. Chinese Chemical Letters [Internet]. 2019;30:2191 - 2195. 访问链接Abstract
Hollow microsphere structure cobalt hydroxide (h-Co(OH)2) was synthesized via an optimized solvothermal-hydrothermal process and applied to activate peroxymonosulfate (PMS) for degradation of a typical pharmaceutically active compound, ibuprofen (IBP). The material characterizations confirmed the presence of the microscale hollow spheres with thin nanosheets shell in h-Co(OH)2, and the crystalline phase was assigned to α-Co(OH)2. h-Co(OH)2 could efficiently activate PMS for radicals production, and 98.6% of IBP was degraded at 10 min. The activation of PMS by h-Co(OH)2 was a pH-independent process, and pH 7 was the optimum condition for the activation-degradation system. Scavenger quenching test indicated that the sulfate radical (SO4• −) was the primary reactive oxygen species for IBP degradation, which contributed to 75.7%. Fukui index (f −) based on density functional theory (DFT) calculation predicted the active sites of IBP molecule for SO4• − attack, and then IBP degradation pathway was proposed by means of intermediates identification and theoretical calculation. The developed hollow Co(OH)2 used to efficiently activate PMS is promising and innovative alternative for organic contaminants removal from water and wastewater.
Kim J, Zhang T, Liu W, Du P, Dobson JT, Huang C-H. Advanced Oxidation Process with Peracetic Acid and Fe(II) for Contaminant Degradation. Environmental Science & Technology [Internet]. 2019;53:13312-13322. 访问链接Abstract
Fe(II) is an excellent promoter for advanced oxidation processes (AOPs) because of its environmental ubiquity and low toxicity. This study is among the first to characterize the reaction of peracetic acid (PAA) with Fe(II) ion and apply the Fe(II)/PAA AOP for degradation of micropollutants. PAA reacts with Fe(II) (k = 1.10 × 105–1.56 × 104 M–1 s–1 at pH 3.0–8.1) much more rapidly than H2O2 and outperforms the coexistent H2O2 for reaction with Fe(II). While PAA alone showed minimal reactivity with methylene blue, naproxen, and bisphenol-A, significant abatement (48–98%) of compounds was observed by Fe(II)/PAA at initial pH of 3.0–8.2. The micropollutant degradation by Fe(II)/PAA exhibited two kinetic phases (very rapid then slow) related to PAA and H2O2, respectively. Based on experimental evidence, formation of carbon-centered radicals (CH3C(O)O•, CH3C(O)•, and •CH3), •OH, and Fe(IV) reactive intermediate species from the PAA and Fe(II) reactions in the presence of H2O2 is hypothesized. The carbon-centered radicals and/or Fe(IV) likely played an important role in micropollutant degradation in the initial kinetic phase, while •OH was important in the second reaction phase. The transformation products of micropollutants showed lower model-predicted toxicity than their parent compounds. This study significantly advances the understanding of PAA and Fe(II) reaction and demonstrates Fe(II)/PAA to be a feasible advanced oxidation technology.
Zhou N, Dang C, Zhao Z, He S, Zheng M, Liu W, Wang X. Role of sludge retention time in mitigation of nitrous oxide emission from a pilot-scale oxidation ditch. Bioresource Technology [Internet]. 2019;292:121961. 访问链接Abstract
Nitrous oxide (N2O) emission from wastewater treatment plants (WWTPs) has become a focus of attention due to its significant greenhouse effect. In this study, the role of sludge retention time (SRT) in mitigation of N2O emission from a pilot-scale oxidation ditch was systematically investigated. The activated sludge system that operated at SRT of 25 days demonstrated significantly lower N2O emission factor, higher resistance to ammonia overload and aeration failure shock than those obtained at SRT of 15 days no matter which hydraulic retention time (HRT) was adopted. Batch experiments revealed that nitrifier denitrification (ND) was the primary mechanism of N2O generation. However, more microbes affiliated with Nitrospira genera were harbored in the system at SRT 25 d, which could effectively avoid nitrite accumulation, a key factor promoting N2O generation by ND. PICRUSt results further suggested the system at SRT 25 d possessed higher genetic potential for N2O reduction reflected by the more abundant nitrous-oxide reductase.
Xu X, Liu Y, Wang T, Ji H, Chen L, Li S, Liu W. Co-adsorption of ciprofloxacin and Cu(II) onto titanate nanotubes: Speciation variation and metal-organic complexation. Journal of Molecular Liquids [Internet]. 2019;292:111375. 访问链接Abstract
Titanate nanotubes (TNTs) have been reported to show good adsorption performance for heavy metals, but researches on organic contaminants adsorption by TNTs are limited. In this study, co-adsorption of a heavy metal (Cu) and an emerging organic contaminant (ciprofloxacin, CIP) by TNTs was investigated in binary systems. TNTs could simultaneously remove the two contaminants, with a high adsorption capacity of 234.5 μmol/g for Cu(II) and 237.0 μmol/g for CIP at pH 4 in the binary system. pH greatly affected adsorption due to speciation variation of the contaminants and surface charge change of TNTs. Cu(II)-CIP complexes dominated adsorption capacity and mechanism. Adsorption of CIP was promoted by high concentration of Cu(II) at pH 3–8 due to formation of abundant Cu(CIP±)2+, while inhibited by low concentration of Cu(II) because of competitive adsorption. The adsorption affinity of CIP species to TNTs was ranked as: Cu(CIP±)2+ > CIP+ > CIP± > Cu(CIP±)2+ > Cu(CIP−·CIP±)+ > CIP−. In comparison, the co-existence of CIP slightly affected Cu(II) adsorption considering the strong affinity of Cu2+ to TNTs. X-ray photoelectron spectrometer (XPS) and Fourier transform infrared spectroscopy (FTIR) results further confirmed the formation of Cu(II)-CIP complexes through –NH2Cu/–COOCu linkages. This work not only proposed a feasible technology for co-removal of heavy metals and organics from water, but also presented insight into interaction mechanisms of different contaminants with nanomaterials during adsorption.
Cai Z, Hao X, Sun X, Du P, Liu W, Fu J. Highly active WO3@anatase-SiO2 aerogel for solar-light-driven phenanthrene degradation: Mechanism insight and toxicity assessment. Water Research [Internet]. 2019;162:369 - 382. 访问链接Abstract
The global energy crisis and water pollution drive the researchers to develop highly effective and less energy intensive water purification technologies. In this study, a highly active WO3@TiO2–SiO2 nanocomposite was synthesized and used for photocatalytic degradation of persistent organic pollutants under simulated solar light. The optimum WO3@TiO2–SiO2 prepared with 2 wt% WO3 loading and calcination at 800 °C exhibited higher photocatalytic activity, as the rate constant (k1) for phenanthrene degradation was ∼7.1 times of that for the commercial TiO2 (P25). The extremely large specific surface area (>400 m2/g) of WO3@TiO2–SiO2 afforded it with enlarged pollutants adsorption performance and abundant active surface sites. The heterojunction of anatase with SiO2 as well as loading of WO3 decreased the band gap energy (Eg) of TiO2, which extended the utilization spectrum of TiO2 to visible region. Formation of Ti–O–Si band indicated the excess charges can cause Brønsted acidity due to the absorption of protons to compensate the charges. Moreover, the migration of photo-excited electrons from the conduction band of anatase to WO3 and holes in the opposite direction restrained the electron-hole recombination. The photocatalytic degradation mechanism and pathway for phenanthrene degradation were proposed based on experimental analysis and density functional theory (DFT) calculation, and the toxicities of the degradation intermediates were evaluated by quantitative structure–activity relationship (QSAR) analysis. WO3@TiO2–SiO2 also showed good separation (settling) performance and high stability. Our work is expected to offer new insight into the photocatalytic mechanism for WO3, TiO2 and SiO2 based heterojunctions, and rational design and synthesis of highly efficient photocatalysts for environmental application.
Zhou N, Zhao Z, Wang H, Chen X, Wang M, He S, Liu W, Zheng M. The effects of graphene oxide on nitrification and N2O emission: Dose and exposure time dependent. Environmental Pollution [Internet]. 2019;252:960 - 966. 访问链接Abstract
With the extensive application of graphene oxide (GO), its leakage and release into wastewater treatment plants become inevitable. However, the toxicity of graphene oxide (GO) on nitrification process and the underlying mechanisms still remain unclear. In this study, the toxic effects of GO at concentration of 10 and 100 mg/L in 4 h and 10 days were evaluated with sealed reactors operated in sequencing batch mode. In the initial 4 h, both GO concentrations showed no negative effect on nitrogen conversion. However, the exposure to 100 mg/L GO significantly weakened the NH+ 4-N and NO- 2-N conversion capabilities and intensified the nitrous oxide (N2O) generation after 10 days. Extracellular polymeric substance (EPS) analysis suggested that 100 mg/L GO decreased the protein content of the nitrifying activated sludge. Moreover, reactive oxygen species (ROS) level was promoted by 100 mg/L GO owing to the impaired endogenous antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT), which caused oxidative stress to bacteria. Finally, quantitative PCR results confirmed that nitrite-oxidizing bacteria (NOB) and complete ammonia oxidizing bacteria (CAOB) were more sensitive to GO, which was the primary cause for the significant promotion of N2O generation in the high GO concentration. This study offered new insights in the toxicity of GO on nitrification and N2O generation in the terms of dose and exposure time.
Chen Q, Chen L, Qi J, Tong Y, Lv Y, Xu C, Ni J, Liu W. Photocatalytic degradation of amoxicillin by carbon quantum dots modified K2Ti6O13 nanotubes: Effect of light wavelength. Chinese Chemical Letters [Internet]. 2019;30:1214 - 1218. 访问链接Abstract
A novel carbon quantum dots modified potassium titanate nanotubes (CQDs/K2Ti6O13) composite photocatalyst was synthesized by hydrothermal treatment combined with calcination. X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) indicated formation of potassium titanate nanotubes and successful deposition of CQDs onto K2Ti6O13. The photocatalytic performance of CQDs/K2Ti6O13 composite was evaluated by degradation of amoxicillin (AMX) under the irradiation of visible light and lights with the wavelengths of 365, 385, 420, 450, 485, 520, 595 and 630 nm. The results showed that the photocatalytic activity of CQDs/K2Ti6O13 hybrid material was greatly enhanced compared with the neat K2Ti6O13 calcined at 300 °C. The narrowed band gap energy (Eg) and transfer of photo-excited electron by CQDs inhibited the immediate combination of electron-hole pairs, thus promoting photocatalytic activity. Moreover, CQDs/K2Ti6O13 exhibited a broad spectrum of photocatalytic ability and it was interesting that the photocatalytic activity decreased with the increase of the irradiation wavelength. Reactive oxygen species (ROS) quenching tests suggested the hole (h+) and hydroxyl radical (OH) played the primary roles in photocatalytic degradation of AMX. Moreover, CQDs/K2Ti6O13 showed good reusability for AMX photocatalytic degradation after five successive runs. This study proposed an available method for titanate nanomaterials modification, and the developed novel CQDs/K2Ti6O13 hybrid material is promising for potential application on antibiotics removal from water and wastewater.