Deliang Li

Ultraviolet-assisted synthesis of hourglass-like ZnO microstructure through an ultrasonic and microwave combined technology.

Well-defined hexagonal hourglass-like ZnO microstructures have been synthesized by using simultaneous ultrasound and microwave irradiation methods with the assistance of ultraviolet as well as double sonication (at 25 and 40 kHz). The structure and morphology of as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence spectrum. The results show the synergistic effect of ultrasound and microwave on the formation of ZnO microstructures. Meanwhile, the possible growth mechanism was proposed to elucidate the formation of hexagonal hourglass-like ZnO microstructures.

Dual-functional CoAl layered double hydroxide decorated α-Fe2O3 as an efficient and stable photoanode for photoelectrochemical water oxidation in neutral electrolyte

As a promising photoanode material, hematite (α-Fe2O3) can be used for photoelectrochemical (PEC) water oxidation but there are still great challenges, such as low efficiency and poor stability in neutral pH electrolyte, before it can be used in practice. Herein, a CoAl layered double hydroxide (CoAl-LDH) has been deposited in situ onto α-Fe2O3 nanoarrays. The PEC performances of the resulting composite photoanodes (CoAl-LDH/α-Fe2O3) towards water oxidation were investigated in neutral pH electrolyte. Contrastive experiments indicated that Co2+ in CoAl-LDH provided active catalytic sites for water oxidation, while Al3+ was inactive and offered support for the layered skeleton. CoAl-LDH could have a dual role as an efficient cocatalyst to lower the onset potential and enhance the photocurrent of α-Fe2O3, and as an effective protector of α-Fe2O3 from corrosion in neutral pH electrolyte. Relative to that of bare α-Fe2O3, a ∼250 mV negatively shifted onset potential and an almost 9-fold enhancement in photocurrent density at 1.23 V vs. RHE were observed with CoAl-LDH/α-Fe2O3. Moreover, CoAl-LDH/α-Fe2O3 showed excellent stability at 1.23 V vs. RHE with a steady photocurrent of ∼2 mA cm−2 even after 2 h of irradiation, which was very close to 100% of the initial value. Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance at the interface of α-Fe2O3/electrolyte was significantly decreased by CoAl-LDH decoration. Using H2O2 as a hole scavenger, the charge injection efficiency at the interface of CoAl-LDH/α-Fe2O3 and electrolyte was recorded as 84% at 1.23 V vs. RHE, which was 4-fold higher than that at the interface of α-Fe2O3 and electrolyte. This work demonstrates that CoAl-LDH decorated semiconductors have great potential as efficient and stable photoanodes towards high PEC performance in neutral pH electrolyte.

Synthesis of CdSe and CdSe/TiO2 nanoparticles under multibubble sonoluminescence condition

CdSe and CdSe/TiO(2) nanoparticles were synthesized under multibubble sonoluminescence (MBSL) condition. The influences of TiO(2) introduced as the sensitizer on the morphology and crystal transformation were investigated. The morphology, phase and optical properties of the final products have been characterized by X-ray powder diffraction, transmission electron microscope, UV-vis absorption spectroscopy and photoluminescence spectroscopy. The results showed that as-prepared nanoparticles are well-crystallized, and the suppression of crystal pattern transition as well as the control of CdSe crystal growth can be implemented by coupling of TiO(2) semiconductor. Furthermore, the possible growth mechanism for different morphologies and crystal phases of the nanocrystals were also discussed.

Removal of hexavalent chromium by using red mud activated with cetyltrimethylammonium bromide

The removal of hexavalent chromium [Cr(VI)] from aqueous solution by using red mud activated with cetyltrimethylammonium bromide (CTAB) was studied. The optimum operation parameters, such as CTAB concentration, pH values, contact time, and initial Cr(VI) concentration, were investigated. The best concentration of CTAB for modifying red mud was found to be 0.50% (mCTAB/VHCl,0.6 mol/L). The lower pH (<2) was found to be much more favourable for the removal of Cr(VI). Red mud activated with CTAB can greatly improve the removal ratio of Cr(VI) as high as four times than that of original red mud. Adsorption equilibrium was reached within 30 min under the initial Cr(VI) concentration of 100 mg L-1. The isotherm data were analysed using Langmuir and Freundlich models. The adsorption of Cr(VI) on activated red mud fitted well to the Langmuir isotherm model, and the maximum adsorption capacity was estimated as 22.20 mg g−1 (Cr/red mud). The adsorption process could be well described using the pseudo-second-order model. The result shows that activated red mud is a promising agent for low-cost water treatment.

Studies on Reactive Extraction of Meta‐Aminophenol Using Trialkylphosphine‐Oxide

Abstract Distribution of meta‐aminophenol (MAP) between water and trialkylphosphine oxide (TRPO), dissolved in different diluents (1‐octanol and kerosene), as well as a comparison with the extraction equilibrium of pure diluent alone has been studied. The influence of the pH value of aqueous solutions, the TRPO concentration and diluents on the distribution ratio D has been discussed. The results indicate that the pH value and the TRPO concentration are the key factors that affect D. The non‐polar diluent (kerosene) is favorable for extracting MAP when TRPO is used as extractant. MAP can be extracted with both acidic and neutral extractants (Di(2‐ethylhexyl)phosphoric and TRPO) efficiently in kerosene while the basic one (Alamine 336) in 1‐octanol, and their efficient pH region is 2.5–3.5, 4.5–6.5, and 6.5–7.8, respectively. The extraction ability shows the order of TRPO/kerosene ≥Di(2‐ethylhexyl)phosphoric/kerosene>Alamine 336/1‐octanol. The best selection is TRPO/kerosene with initial pH at 5.5–9.5.

Extraction Equilibria of 4-Hydroxypyridine using Di (2-ethylhexyl) Phosphoric Acid

Extractions of 4-Hydroxpyridine (4HP) from aqueous solutions using Di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant in 1-octanol and kerosene were studied. The factors that affected the distribution coefficient (D), such as equilibrium pH, the concentration of D2EHPA, and the type of diluents were discussed. The interaction mechanism between 4HP and D2EHPA was validated by infrared spectroscopic analysis. D increased with the increase of the concentration of D2EHPA and peak values appeared at equilibrium pH = 3.6–5.0. D in the polar diluent (1-octanol) was much higher than those in the non-polar diluent (kerosene). The extraction reaction was found to be a proton-transfer process and D2EHPA mainly reacted through its –OH with –N– of 4HP. The apparent reactive extraction equilibrium constants K 11 and K 12 were obtained by fitting the experimental data of extraction equilibrium. By comparing calculated D values from the proposed model with the experimental ones, the accuracy of the proposed model was examined.

Synthesis and characterisation of W–Bi–S-tridoped TiO2 nanoparticles with enhanced photocatalytic activity

In the present work, W–Bi–S-tridoped TiO2 nanoparticles were synthesised by a simple sol–gel method. The structure and morphology of as-prepared W–Bi–S-tridoped TiO2 were characterised by using X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy and UV–Vis diffuse reflectance spectrum. It was found that the W–Bi–S-tridoped TiO2 nanoparticles were well crystallised with a small size distribution. The absorption edge of TiO2 was extended into visible-light region obviously after being doped with W, Bi and S. The photocatalytic degradation of methylene blue was used as a probe reaction to evaluate the efficiency of W, Bi and S doping. The W–Bi–S-tridoped TiO2 exhibited the best photocatalytic activity, compared with TiO2, S-TiO2, W–S–TiO2 and Bi–S–TiO2. The mechanism that enhanced photocatalytic activity might be attributed to the synergistic effect of W, Bi and S.

Technical Studies on Hazardfree Treatment and Resource Recovery of Hydrazine Hydrate Solid Waste

Technology of direct hot melt, concentration and crystallization to manufacture hydrazine hydrate solid waste into Na₂CO₃·H₂O and Na₂CO₃ was researched, and principle of process was discussed. Effects of available chlorine dosage, pH value on hydrazine removal rate and crystallization temperature, water evaporation, crystallization time on purity and yield of Na₂CO₃ were investigated, finding out the optimal technological conditions. This technical process did not cause secondary pollution, products reached standard of GB/T22404-2008 and GB210.2-2004 respectively.

Separation science and technology

The focus of this project is the demonstration and advancement of membrane-based separation and destruction technologies. The authors are exploring development of membrane systems for gas separations, selective metal ion recovery, and for separation or destruction of hazardous organics. They evaluated existing polymers and polymer formulations for recovery of toxic oxyanionic metals such as chromate and arsenate from selected waste streams and developed second-generation water-soluble polymeric systems for highly selective oxyanion removal and recovery. They optimized the simultaneous removal of radioactive strontium and cesium from aqueous solutions using the new nonhazardous separations agents, and developed recyclable, redox-active extractants that permitted recovery of the radioactive ions into a minimal waste volume. They produced hollow fibers and fabricated prototype hollow-fiber membrane modules for applications to gas separations and the liquid-liquid extraction and recovery of actinides and nuclear materials from process streams. They developed and fabricated cyclodextrin-based microporous materials that selectively absorb organic compounds in an aqueous environment; the resultant products gave pure water with organics at less than 0.05 parts per billion. They developed new, more efficient, membrane-based electrochemical reactors for use in organic destruction in process waste treatment. They addressed the need for advanced oxidation technologies based on molecular-level materials designs that selectively remove or destroy target species. They prepared and characterized surface-modified TiO{sub 2} thin films using different linking approaches to attach ruthenium photosensitizers, and they started the measurement of the photo-degradation products generated using surface modified TiO{sub 2} films in reaction with chlorophenol.