Tuantuan Zhou

Novel Na2Mo4O13/α-MoO3 hybrid material as highly efficient CWAO catalyst for dye degradation at ambient conditions

We report a novel hybrid material Na2Mo4O13/α-MoO3 as highly efficient catalytic wet air oxidation (CWAO) catalyst, which showed the highest ever activity at room temperature and atmosphere pressure for the degradation of cationic red GTL. SEM and TEM analyses indicated that this hybrid catalyst has bamboo-shaped nanofiber morphology. In view of practical applications, the influence of some key parameters including operation temperature, catalyst calcination temperature, and the volume of dye wastewater have been optimized. The mechanism for the superior catalytic performance was investigated. XRD, XPS, and ESR suggested the Na2Mo4O13/α-MoO3 hybrid catalyst possesses more O2− ions in the oxygen deficient regions than neat α-MoO3, promoting the formation of active ·OH radicals and resulting in a higher activity. Considering the facile preparation and its superior activity, this novel catalyst is promising for practical dye wastewater treatment.

Layered double hydroxide/graphene oxide hybrid incorporated polysulfone substrate for thin-film nanocomposite forward osmosis membranes

Herein, we report the use of a layered double hydroxide/graphene oxide (LDH/GO) hybrid as a nanofiller for a polysulfone (PSf) substrate in the fabrication of a thin film nanocomposite (TFN) forward osmosis (FO) membrane. The influence of the incorporation of the LDH/GO hybrid on the physicochemical properties of the PSf substrate was explored and a systematic investigation of the resultant TFN membrane performance was conducted. The results demonstrate that the addition of the LDH/GO hybrid enhanced the PSf substrate with increased porosity, hydrophilicity, surface pore diameter, and mechanical strength. Consequently, all the TFN membranes obtained increased water permeability and salt rejection, as compared to the thin film composite (TFC) membrane prepared on a conventional PSf substrate. Using 1 M NaCl as the draw solution and DI water as the feed solution, the water flux of the TFN membrane with a 2 wt% LDH/GO dosage as high as 23.6 L m−2 h−1 was obtained under the pressure retarded osmosis (PRO) mode. Compared to conventional TFC membranes, the TFN membrane with a 2 wt% LDH/GO showed a very low reverse salt flux (6.2 g m−2 h−1). The improvement in FO performance is attributed to the lower structural parameters of the modified PSf substrate, and the reduction of the internal concentration polarization. This study suggests the LDH/GO hybrid is an effective additive for modifying the PSf substrate for the development of FO membranes.

Fabrication of Lithium Silicates As Highly Efficient High-Temperature CO2 Sorbents from SBA-15 Precursor

A series of lithium silicates with improved CO2 sorption capacity were successfully synthesized using SBA-15 as the silicon precursor. The influence of Li/Si ratio, calcination temperature, and calcination duration on the chemical composition and CO2 capture capacity of obtained lithium silicates was systematically investigated. The correlation between CO2 sorption performance and crystalline phase abundance was determined using X-ray diffraction and a normalized reference intensity ratio method. Under the optimized condition, Li-SBA15-4 prepared using Li/Si = 4 that contains mainly Li4SiO4 achieved an extremely high CO2 capture capacity of 36.3 wt % (corresponding to 99% of the theoretical value of 36.7 wt % for Li4SiO4), which is much higher than the Li4SiO4 synthesized from conventional SiO2 sources. It also showed very high cycling stability with only 1.0 wt % capacity loss after 15 cycles. Li-SBA15-10 (Li/Si = 10) that mainly contains Li8SiO6 displayed an extremely high CO2 uptake of 62.0 wt %, but its regeneration capacity was poor, with only 10.5 wt % of reversible CO2 capture capacity. The influence of CO2 concentration on the CO2 capture performance of Li-SBA15-4 and Li-SBA15-10 samples was also studied. With the decrease in CO2 concentration, relatively lower temperatures are needed for its maximum CO2 capture capacity. The CO2 sorption kinetics and mechanism for Li-SBA15-4 and Li-SBA15-10 samples were explored. Overall, we have shown that the lithium silicates synthesized from SBA-15 possessed much improved CO2 sorption performance than that attained from conventional SiO2.

Co3O4 nanoparticles/MWCNTs composites: a potential scaffold for hydrazine and glucose electrochemical detection

We report the successful formation of cobalt oxide (Co3O4) nanoparticles/multi-walled carbon nanotubes (Co3O4/MWCNTs) composites as efficient electrocatalytic materials for chemical sensing. Co3O4/MWCNTs composites were synthesized via a straightforward hydrothermal treatment and comprehensively characterized. Working as effective electron mediators, the prepared Co3O4/MWCNTs composites were used for the fabrication of hydrazine (N2H4) and glucose sensors. The electrochemical impedance spectroscopy (EIS) studies confirmed Co3O4/MWCNTs/glassy carbon electrode (GCE) exhibited higher conductivity than bare GCE and Co3O4/GCE, endorsing a faster electron transfer rate and a higher electrocatalytic activity. The addition of MWCNTs can not only improve the dispersion of Co3O4 nanoparticles but also facilitate the electron transfer rate. The sensitivity, selectivity, repeatability, reproducibility, linear range and detection limit of the fabricated sensors were systematically investigated. The fabricated hydrazine sensor displayed a great sensitivity of 120.26 μA mM−1, a wide linear range of 1.0–187.4 μM, and a rather low detection limit of 0.449 μM, and the fabricated glucose sensor exhibited a high sensitivity of 63.27 μA mM−1, a wide linear range of 1.70–554 μM, and a low detection limit of 0.95 μM. We demonstrated that such fabricated Co3O4/MWCNTs composites may have favorable applications in the establishment of fast and effective determination of environmental pollutants.

Effect of Fluoride on the Morphology and Electrochemical Property of Co3O4 Nanostructures for Hydrazine Detection

In this paper, we systematically investigated the influence of fluoride on the morphology and electrochemical property of Co3O4 nanostructures for hydrazine detection. The results showed that with the introduction of NH4F during the synthesis process of Co3O4, both Co(CO3)0.5(OH)·0.11H2O and Co(OH)F precursors would be generated. To understand the influence of F on the morphology and electrochemical property of Co3O4, three Co3O4 nanostructures that were respectively obtained from bare Co(CO3)0.5(OH)·0.11H2O, Co(OH)F and Co(CO3)0.5(OH)·0.11H2O mixtures and bare Co(OH)F were successfully synthesized. The electrochemical tests revealed the sensing performance of prepared Co3O4 nanostructures decreased with the increase in the fluoride contents of precursors. The more that dosages of NH4F were used, the higher crystallinity and smaller specific surface area of Co3O4 was gained. Among these three Co3O4 nanostructures, the Co3O4 that was obtained from bare Co(CO3)0.5(OH)·0.11H2O-based hydrazine sensor displayed the best performances, which exhibited a great sensitivity (32.42 μA·mM−1), a low detection limit (9.7 μΜ), and a wide linear range (0.010–2.380 mM), together with good selectivity, great reproducibility and longtime stability. To the best of our knowledge, it was revealed for the first time that the sensing performance of prepared Co3O4 nanostructures decreased with the increase in fluoride contents of precursors.

Synthesis and characterization of alkali metal molybdates with high catalytic activity for dye degradation

In this contribution, the synthesis and catalytic activity of alkali metal molybdates for the degradation of cationic dyes under ambient conditions were systematically studied. The influences of Na and Mo precursors, Na/Mo ratio, and calcination temperature on the chemical composition and catalytic activity of sodium molybdates were investigated. Among all the obtained sodium molybdates, Na2Mo2O7 showed the highest catalytic activity for the degradation of cationic red GTL, safranine T, and methylene blue, etc. Particularly for cationic red GTL, a degradation efficiency of 98.5% could be achieved within 5 min. The optimal synthesis conditions for the formation of pure Na2Mo2O7 are also presented. The morphology and structure of Na2Mo2O7 were carefully characterized using XRD, SEM, HR-TEM and SAED, and FT-IR. In addition to sodium molybdates, potassium and lithium molybdates were also similarly synthesized, which also showed excellent catalytic activities for dye degradation. This work will shed light on the synthesis of novel active catalysts for the catalytic wet air oxidation of dyes.

High Aspect Ratio Perforated Co3O4 Nanowires Derived from Cobalt-Carbonate-Hydroxide Nanowires with Enhanced Sensing Performance

Herein, we report the facile synthesis of high-aspect ratio perforated Co3O4 nanowires derived from cobalt-carbonate-hydroxide (Co(CO3)0.5(OH) 0.11H2O) nanowires. The Co(CO3)0.5(OH) 0.11H2O nanowires were synthesized by simple hydrothermal process at 120 °C while annealing of such nanowires at 400 °C leads the formation of perforated Co3O4 nanowires. The prepared nanowires were characterized by several techniques which confirmed the high aspect ratio and well-crystallinity for the synthesized nanowires. For application point of view, the prepared perforated Co3O4 nanowires were used as efficient electrode material to fabricate highly sensitive and selective hydrazine chemical sensor. The electrochemical impedance spectroscopy (EIS) technique was employed to confirm the successful modification of the electrode. The key parameters of chemical sensor, such as detection limit, sensitivity, and linear range, have been systematically explored. The fabricated hydrazine sensor displayed a rather low detection limit of 4.52 μM (S/N = 3), a good sensitivity of 25.70 μA · mM-1, and a wide linear range of 16.97-358.34 μM.

Flower-Shaped Mg3Al1−xFex–CO3 Layered Double Hydroxides Derived Adsorbents with Tunable Memory Effect for Environmental Remediation

Herein, flower-shaped ternary layered double hydroxides (LDHs) Mg3Al1-xFex-CO3 with tunable memory effect as promising adsorbents was developed for the removal of acid red 88 anionic dye. All the samples were prepared using a co-precipitation method and were thoroughly characterized using several analytical techniques. The influence of Fe/(Al + Fe) ratio on the memory effect and dye adsorption capacity of Mg3Al1-xFex-CO3 LDHs was evaluated. Among all samples, Mg3Fe0.1Al0.9CO3 LDH resulted in the best adsorption capacity of 2709 mg/g in the first cycle. Comparing to Mg3Al1-CO3 and Mg3Fe1-CO3 LDHs, it also showed much better cycling performance during 4 cycles at 30 °C and atmospheric pressure. The influence of regeneration temperature was also investigated and found that 400 °C exhibit best performance. The detailed studies demonstrated that the adsorption capacity of Mg3Al1-CO3 can be improved by partially replacing Al by Fe.