Baochang Sun

Ozonation of azo dye Acid Red 14 in a microporous tube-in-tube microchannel reactor: decolorization and mechanism.

The ozonation of synthetic wastewater containing azo dye Acid Red 14 (AR 14) was investigated in a high-throughput microporous tube-in-tube microchannel reactor. The effects of design and operating parameters such as micropore size, annular channel width, liquid volumetric flow rate, ozone-containing gas volumetric flow rate, initial pH of the solution and initial AR 14 concentration on decolorization efficiency and ozone utilization efficiency were studied with the aim to optimize the operation conditions. An increase of the ozone-containing gas or liquid flow rate could greatly intensify the gas-liquid mass transfer. Reducing the micropore size and the annular channel width led to a higher mass transfer rate and was beneficial to decolorization. Decolorization efficiency increased with an increasing ozone-containing gas volumetric flow rate, as well as a decreasing liquid volumetric flow rate and initial AR 14 concentration. The optimum initial pH for AR 14 ozonation was determined as 9.0. The degradation kinetics was observed to be a pseudo-first-order reaction with respect to AR 14 concentration. The difference between the decolorization and COD removal efficiency indicated that many intermediates existed in AR 14 ozonation. The formation of six organic intermediates during ozonation was detected by GC/MS, while the concentration of nitrate and sulfate ions was determined by ion chromatography. The possible degradation mechanism of AR 14 in aqueous solution was proposed.

The Advanced Oxidation Process of Phenol Solution by O3/H2O2 in a Rotating Packed Bed

This article presents experimental investigation on the oxidative treatment of phenol in water by O3/H2O2 in a rotating packed bed (RPB). It was found that the phenol degradation ratio increased with increasing rotation speed, initial pH value of phenol solution, and temperature. The degradation ratio of phenol had a peak value with increasing H2O2 concentration. The optimum operating conditions in this study were determined as an H2O2 concentration of 6.5 mM and a rotation speed of 1200 rpm. Phenol degradation ratio reached 100% at an initial phenol concentration of 40 mg/L in the O3/H2O2 process.

Treatment of wastewater containing o-phenylenediamine by ozone in a rotor-stator reactor

This work employed a novel rotor-stator reactor (RSR) to intensify the degradation process of o-phenylenediamine (o-PDA) by ozone. The effects of different operating parameters including initial pH, temperature, rotation speed, liquid volumetric flow rate and inlet ozone concentration on the removal efficiency of o-PDA were investigated in an attempt to establish the optimum conditions. The removal efficiency was evaluated in terms of degradation ratio and chemical oxygen demand (COD) reduction ratio of the o-PDA wastewater. Results indicate that the removal efficiency decreased with increasing liquid volumetric flow rate but increased with an increase in pH and inlet ozone concentration. Also, the removal efficiency increased up to a certain level with an increase in rotation speed and temperature. Additionally, a comparison experiment was carried out in a stirred tank reactor (STR), and the results show that the degradation and COD reduction ratios reached a maximum of 94.6% and 61.2% in the RSR as compared to 45.3% and 28.6% in the STR, respectively. This work demonstrates that ozone oxidation carried out in RSR may be a promising alternative for pre-treatment of o-PDA wastewater.

Study on the treatment of simulated coking wastewater by O3 and O3/Fenton processes in a rotating packed bed

In this study, simulated coking wastewater was treated by the O3/Fenton process in a rotating packed bed (RPB) and the results were compared with those by the O3 process. Contrast experiments indicated that the degradation rates of phenol, aniline, quinoline and NH3–N in the wastewater reached 100%, 100%, 95.68% and 100% respectively under the optimum operating conditions in the O3/Fenton process and were much higher than those in the O3 process. The BOD5/COD value of the simulated coking wastewater treated in the O3/Fenton process reached 0.46 and was 135% higher than that in the O3 process. The degradation pathways of phenol, aniline, quinoline and NH3–N in the simulated coking wastewater were also discussed. The results indicated that a combination of the advanced oxidation processes and the RPB can enhance the treatment efficiency of coking wastewater.

Facile synthesis of CdTe-based quantum dots promoted by mercaptosuccinic acid and hydrazine

CdTe-based quantum dots (QDs) with high photoluminescence quantum yields (PL QYs) were synthesized in a short time (less than 45 minutes). Mercaptosuccinic acid (MSA) was employed as a stabilizer and N2H4 as a growth promoter to accelerate the growth of CdTe and CdSexTe1−x QDs. Red-emitting CdTe QDs with a PL QY of 25% were obtained and the highest PL QY reached 55%. CdSexTe1−x QDs with emission peak positions of 518 nm to 750 nm were obtained. The rapid growth of QDs depends on the interaction between MSA and Cd2+, and N2H4 plays a key role in accelerating the growth to a certain level. Thus, the QD particle size can be controlled by manipulating N2H4 concentration in solution. A low N2H4 concentration seems feasible to obtain high-quality QDs.

Synthesis and optimization of CdTe quantum dots with the help of erythorbic acid and ethanol

The effects of erythorbic acid (EA) and ethanol on the aqueous formation of cadmium telluride (CdTe) quantum dots (QDs) were explored in this work. Without N2 protection, CdTe QDs were synthesized with cadmium chloride and sodium hydrogen telluride as the Cd source and Te source, respectively, together with EA and with 3-mercaptopropionic acid (MPA) as the co-passivating ligand. The experimental results indicated that the use of the oxygen scavenger, i.e., EA, was critical for the formation of the CdTe QDs with reasonably good optical properties. Including ethanol during the synthesis improved the photoluminescence intensity. To attain good optical properties, it is also important to tune experimental parameters such as pH, temperature, reaction time, molar ratio of MPA/Cd, and sodium borohydride dosage. The very reason that EA promoted formation of CdTe QDs is because of its reducibility and passivation on the QD surface. The present study suggests that the use of EA and ethanol could be a practical means to promote the photoluminescence of CdTe.

Synthesis of protein/hydroxyapatite nano-composites by a high-gravity co-precipitation method

This study explored potential use of a high-gravity co-precipitation strategy to synthesize gelatin/hydroxyapatite (Gel/HAP) nano-composites with high protein adsorption efficiencies. The physicochemical properties were characterized using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectra, thermal gravimetric analysis and Brunauer–Emmett–Teller. Biocompatibility was determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assays on hFOB 1.19 osteoblast cells. The results confirmed formation of Gel/HAP composites exhibiting nano-rod-like morphologies with high protein adsorption efficiencies and biocompatibilities. In addition, the Gel/HAP nano-composites were molded into cylindrical shaped Calcium Phosphate Cements (CPC), displaying an average compressive modulus of ∼0.6 GPa. The compressive modulus was comparable with that of a human cancellous bone, suggestive of great potential of the Gel/HAP nano-composites in various biomedical applications through serving as bone substitute materials. The high-gravity co-precipitation technique was also applied to synthesize Silk/HAP nano-composites. Therefore, the high-gravity co-precipitation method provides a novel approach for synthesis of various protein/HAP materials.