Cao Hongbin

Properties of water blown rigid polyurethane foams with different functionality

Water blown rigid polyurethane foams with different functionality were prepared. The physical properties of rigid foams were measured with rotational viscometer (NDJ-1), universal testing machine (Instron3365), scanning electron microscope (SEM) and differential scanning calorimeter (DSC). The results show that the viscosity of polyether polyol increases exponentially from 62 mPa·s to 6 000 mPa·s with the increase of functionality from 2 to 5.6, respectively. The overall density of foam increases slightly from 31.7 kg/m3 to 37.4 kg/m3 with increasing functionality while core density exhibited little difference. Compressive strength of foam shows the similar behavior with density except for 2-functional sample. At the same time, dimensional stability becomes better with increasing functionality except for 5.6-functional foam that has worse stability than 4.8-functional foam. From the SEM results, the functionality is not an important factor in determining distribution of cell size of foam. According to the results of thermal analysis, the glass transition temperature (Tg) shifts to a higher temperature from 128.9 ° to 166.3 ° for the 2 to 5.6 functional foam, respectively.

Double layered, one-pot hydrothermal synthesis of M-TiO2 (M = Fe3+, Ni2+, Cu2+ and Co2+) and their application in photocatalysis

A double layered, one-pot hydrothermal method was adopted in this work to prepare transition metal ions (Fe3+, Ni2+, Cu2+ and Co2+) doped TiO2. The morphology and chemical properties of TiO2 and the status of metal ions were characterized with XRD, TEM, BET, UV-Vis and XPS analysis. TEM images show that the obtained TiO2 was very uniform with an average particle size of 10.4 nm. XPS, TEM and XRD results show that transitional metals were doped onto TiO2 in the form of ions. Photocatalytic decomposition of oxalic acid under UV illumination and methylene blue degradation under visible light on these materials were conducted, respectively. The results reveal that Cu2+-TiO2 and Co2+-TiO2 showed a highest activity under UV and visible light illumination, respectively, and they were both more active than commercial P25 TiO2. With this special design of double layers, the hydrolysis of titanium precursor in the system with water can be easily controlled and metal ions are simply doped. This strategy can be further applied to synthesize metal ion doped TiO2 using various metal precursors with controllable amounts, and thus lead to better optimization of highly active photocatalyst.

Comparison of Mg2+- and Ca2+-enhancing anaerobic granulation in an expanded granular sludge-bed reactor

The mechanisms responsible for the fast granulation of anaerobic sludge caused by Mg2+ and Ca2+ addition was examined in four lab-scale expanded granular sludge bed (EGSB) reactors. Results indicated that both Mg2+ and Ca2+ accelerated the sludge-granulation process and increased the amount of polysaccharides and proteins in the sludge. Energy dispersive x-ray spectrometry (EDX) analysis revealed that, in a mature granule, both Mg2+ and Ca2+ composed as phosphate and calcium was distributed primarily in the periphery of the granule, while magnesium distributed mainly in the interior. The addition of Mg2+ was more favorable for the nuclei formation, whereas the addition of Ca2+ was more favorable for subgranule growth and maintaining the granules’ rigid structure. Results showed that the addition of Mg2+ in the nuclei formation stage and Ca2+ in the granule-growth stage accelerated granulation more than adding only one of them in the granulation process.

Application of triple potential step amperometry method for quantitative electroanalysis

A novel quantitative electroanalysis method, triple potential step amperometry (TPSA), was developed and explained with an example of nitrobenzene analyzing in water. The selectivity of TPSA was improved by controlling the potential step within a narrow interval and using enzyme-modified electrode, the narrow potential step makes the method avoid most interferents, and enzyme-modified electrode can enhance the response of target substance selectively. The peak area was investigated for quantitative calibration, such as nitrobenzene concentration showing a linear relation with the peak area, with the correlation coefficients being 0.9995. The t-test and F-test were applied to evaluating the reliability of TPSA, the results showed that there was no evidence of systematic error for TPSA, and the method was of no significant difference from CV. The merit of fast detecting and few potential changing times make the TPSA suitably applicable to low-cost automatic monitoring equipments.

Thermodynamic models based on Pitzer-NRTL and Pitzer-Margules equations for the extraction of tungstic acid with primary amine N1923

The thermodynamic model of the extraction of W with primary amine under near neutral conditions is reported in this paper. The activity coefficients of the nonelectrolytes in organic phase are calculated by the Margules and NRTL equations which are based on previously tested liquid-liquid extraction equilibrium data in combination with mass balances and charge balance formula. The activity coefficients of the electrolytes in aqueous phase are calculated by the Pitzer equation. The thermodynamic model of the extraction of W by a primary amine is constructed from the calculated activity coefficients of electrolytes and nonelectrolytes. The extraction of W using primary amine is also predicated, and the data is compared to the calculated results of the thermodynamic model. It is concluded that Margules equation proves to be suitable and reliable for calculating the activity coefficients of nonelectrolytes in complex organic phase systems.

Coagulation behaviors and in-situ flocs characteristics of composite coagulants in cyanide-containing wastewater: Role of cationic polyelectrolyte

In this paper, composite coagulants (PFS, PFSC05, PFSC1 and PFSC5), prepared by mixing polyferric sulfate (PFS) and cationic polyelectrolyte (CP) coagulants with different weight percent (Wp) of CP (Wp = 0%, 0.5%, 1% and 5%, respectively), were adopted to treat cyanide-containing wastewater. PFSC5 exhibited superior coagulation performances at optimal conditions: the removal of total cyanide (TCN) and chemical oxygen demand (COD) was 95%–97% and 50%–55%, respectively. The effects of CP on the properties and structure of flocs were investigated by laser diffraction instrument and small-angle laser light scattering (SALLS), respectively. The results show that the flocs of PFSC5 have higher growth rate, higher strength factor and lower recovery factor than other flocs. They are also much denser and more uniform owing to the higher fractal dimension (Df) and less microflocs (10–100 μm). Furthermore, the dense structure of the PFSC5 flocs can be restored after shear and is more resistant to hydraulic conditions. Particularly, detailed morphology evolution of the flocs was in-situ detected by on-line particle imaging. Due to strong ionic strength in wastewater, the CP in PFSC5 plays a significant role of adsorption, while the main mechanism of CP is electrostatic patch aggregation during the PFSC05 systems.