Biomedical subjects

Zhao-kun Luan

Publications and source records attributed to Zhao-kun Luan.

12 recordsLinked to original sources

PubMed2006

[Atomic force microscope analysis of adsorption and flocculation behaviors of polydiallyldimethylammonium salts: influence of counterion].

High molecular weight polydiallyldimethylammonium nitrate (PDADMANO3) and polydiallyldimethylammonium sulfate (PDADMASO4) were prepared from polydiallyldimethylammonium chloride (PDADMAC). The effects of univalent counterions (Cl-, ON3-) and bivalent counterion (SO4(2-) on solution, absorption and flocculation properties of polydiallyldimethylammonium salts (PDADMAX) were investigated by conductivity, reduced viscosity, atomic force microscopy (AFM), residual turbidity, distributions of zeta potential and flocculation index of kaolin suspension. The results show that different counterions possess significant effects on solution properties, absorption and flocculation behaviors of PDADMAX. PDADMANO3 shows stronger flocculation efficiency and "neutralization action", whereas PDADMASO4 shows the wider optimum dosage and larger floc size, as well as "bridging action". In particular, AFM image of single polyelectrolyte polymer is a valuable tool for the analysis of the absorption and flocculation mechanism of polyelectrolye.

Adsorption↗

PubMed2006

[Electrocatalytic reduction of nitrate from drinking water by porous titanium loaded Pd-Cu cathode].

We investigated performances as well as influencing factors of electrocatalytic denitrification of a porous titanium loaded Pd-Cu (4:1) cathode, from drinking water. Up to 96.9% of NO3(-)-N may be reduced to N2 with electrocatalytic activity as 16.69 mg/ (g x h). The Nitrate reduction presented an apparent first order reaction at lower nitrate concentration, while a zero order reaction at higher nitrate concentration. Little nitrate reduction was observed when cell voltage (or current) was lower than 1.5 V (or 5 mA); the side reaction of ammonium production became noticeable if the cell voltage (or current) was higher than 4.2 V (or 30 mA). Both the activity and the selectivity were good at a neutral pH; at acidic pH, the activity increased while the selectivity decreased. Mass transfer in solution was found little effect on the reactions in the tests. Other anions such as ClO4-, HCO3-, Cl- did somewhat harms to NO3(-)-N removal with sequence of ClO4- < HCO3- < Cl-.

Catalysis↗

PubMed2005

A cleaner two-step synthesis of high purity diallyldimethylammonium chloride monomers for flocculant preparation.

In order to improve the flocculation efficiency of polydiallyldimethylammonium chloride (PDADMAC), high molecular weight PDADMAC should be prepared from high purity diallyldimethylammonium chloride(DADMAC) monomers. In this paper, a cleaner method with microwave irradiation and alkali solidification was proposed for preparing high pure DADMAC by selective heating under low temperature, and the prepared high purity DADMAC is characterized using FTIR and atomic absorption spectrometry. The new method provides a solution to the key technical problem of PDADMAC synthesis. Comparing with the conventional methods, the results showed that the advantages of the novel synthesis include: (a) high purity DADMAC is improved from 57% to 71%; (b) reaction time of tertiary amine preparation is shortened from 6 h to 7 min; (c) water instead of acetone was used as reaction medium; (d) toxic by-products, wastewater and waste gas are eliminated. Flocculant made from the synthesized high purity DADMAC monomers was proved more efficient in flocculation tests.

Allyl Compounds↗

PubMed2004

Bubble performance of a novel dissolved air flotation(DAF) unit.

ES-DAF, a novel DAF with low cost, high reliability and easy controllability, was studied. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied in detail by using a newly developed CCD imagination through a microscope. Compared with M-DAF under the same saturation pressure, ES-DAF can produce smaller bubble size and higher bubble volume concentration, especially in lower pressure. In addition, the bubble size decreases with the increase of reflux ratio or decrease of superficial air-water ratio. These results suggested that smaller bubbles will be formed when the initial number of nucleation sites increases by enhancing the turbulence intensity in the saturation system.

Air↗

PubMed2004

Removal of heavy metals from aqueous solution by carbon nanotubes: adsorption equilibrium and kinetics.

Carbon nanotubes prepared by catalytic chemical vapor deposition of hydrocarbon at 650 degrees C show good adsorption capability of Pb2+, Cu2+ and Cd2+ ions from aqueous solution after oxidized with concentrated nitric acid at 140 degrees C for 1 h. The specific surface area and particle size distribution of the as-grown and oxidized CNTs were studied by BET method and laser particle analyzer. Three kinetic models, that is, first-, pseudo second- and second-order, were used to investigate the adsorption data and the pseudo second-order model can represent the experimental data better than two others. The equilibriumdata fitted well with the Langmuir model and showed the following adsorption order: Pb2+ > Cu2+ > Cd2+.

Adsorption↗

PubMed2004

Physicochemical interaction and its influence on deep bed filtration process.

The capillary model was used to analyze the hydraulic conditions in the deep bed filtration process. The physicochemical interaction forces between the filter media and suspended particles and their influence on deep bed filtration process were also studied theoretically. Through the comparison of the hydraulic and physicochemical forces, the key influencing factors on the filtration process were proposed and investigated. Pilot study of the microflocculation deep bed filtration was carried out in the No. 9 Potable Water Treatment Plant of Beijing, and the experimental results of hydraulic head loss, particle distribution and entrapment were presented. The theoretical prediction was reasonably consistent with the experimental results under different conditions, which indicated that the regulation and control of micro-flocculation and deep bed filtration could be realized by the evaluation of the physicochemical interactions. Further theoretical and experimental research should be carried out to investigate the interaction mechanism and its application in the deep bed filtration and other cases.

Filtration↗

PubMed2004

[Preparation of polyaluminum silicate chloride (PASC) from tetraethylorthosilicate (TEOS) and its physicochemical characteristics].

A new type of polyaluminum silicate chloride [PASC(A)] was prepared by employing tetraethylorthosilicate (TEOS) as silicon source. By comparing PASC(A) with the conventional product [PASC(B)], the effects of B value and Si/Al molar ratio on the pH value and the Zeta potential of PASC(A) were investigated. The influence of the incorporation of silicon into PASC on the molecular structure and aluminium species was also studied by acidification method and 27Al NMR spectroscopy. The results show that the PASC(A) has higher polymerization degree, narrow distribution of molecular weight and symmetrical distribution of aluminium and silicon in PASC molecule. It is more difficult to be acidified, and moreover, it can reduce the loss of Al13 species. All the above advantages of PASC(A) are due to its special synthesis method.

Aluminum Silicates↗

PubMed2004

[Removal of turbidity and effect of humic acid in flocculation by polyferric chloride].

The removals of humic acid and turbidity by polyferric chloride under different coagulation conditions were studied (pH = 4, 7, 10). Zeta potential, turbidity and humic acid removal efficiency were analyzed. Experimental results showed that the dosage and scope of polyferric chloride (PFC) is the narrowest and the residual turbidity is biggest when pH = 4, the dosage and scope of PFC is the broadest and the residual turbidity is the least when pH = 10; Fe(III) can complex with humic acid under acidic condition; The effect of flocculation is not influenced by the presence of humic acid.

Chlorides↗

PubMed2004

[Characterization of bubble size distribution in ES-DAF unit].

ES-DAF unit was introduced and studied in this paper. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied by using a CCD imagination through a microscope. The bubble size decreased with the increase of cycle ratio or the decrease of superficial air-water ratio. These results suggest that smaller bubbles would be formed when the initial number of nucleation sites increase by enhancing the turbulence intensity in the saturation system. The bubble size distribution became lower and wider with the increase of saturation pressure because of more frequent bubble collision and coalescence.

Air↗

PubMed2004

[Synthesis of high-concentration polyaluminum chloride and its aluminium species distribution and transformation].

Using solid CaO as basification agent, the high-concentration polyaluminum chloride (PAC) was prepared by feeding total alkali at a time. The characteristics of the reaction and the distribution and transformation of the aluminium species were also studied. The experimental results show that the distinctive hydration of CaO can contribute to the high-concentration PAC whose Al concentration (Al(T)) and basicity (B) can reach 2.1 mol/L and 2.1 respectively. There is an optimal B value in any concentration of PAC, at which the Al(b) content is the highest. The optimal B value and the highest Al(b) content drops with the increasing of Al(T). The predominant reaction is the formation of Al(b) if B is less than the optimal B value, and the formation of Al(c) if B is more than the optimal B value.

Aluminum↗

PubMed2003

Watershed protection and landscape enhancement by utilization of river water.

A scheme for watershed protection and landscape enhancement (WPLE) by utilization of river water was proposed to renovate water resources and protect ecological environment in Qiongshan City, Hainan Province, China. Utilization of river water may diminish the drought and flood risks. The scheme is beneficial to solve the problems of water resources shortage, groundwater declines and saltwater intrusion in the watershed. The object of the WPLE scheme is to achieve a sustainable integrated development of environment, ecology, economy and society. A kind of physically beautiful and functionally vivid landscape may exert its synthetical function on the diversity of landscape and the enjoyment of inhabitants. Feasibility of the scheme will be demonstrated by more experiments and tests, as well as observations in a long term.

China↗

PubMed2003

Assessment of the environmental impact of artificial effluent lagoon in Jiayuguan City of China.

An artificial effluent lagoon for storing wastewater were excavated in Jiayuguan City since 1994. As a part of a demonstration project of Sino-Australia cooperation, an assessment of the environmental impact of the lagoon was carried out. The assessment was based on field and laboratory tests and predictive model. The main impacts from the lagoon site are likely to be on the groundwater system, and, to a lesser extent, on ambient air quality in the vicinity. Currently it is expected that groundwater is being polluted with effluent from the effluent lagoon. Air pollution (odor nuisance) is mainly caused by untreated effluent in the irrigation channel. The impact of high total dissolved salt (TDS) on groundwater is likely to be significant in the long run if the lagoon is continuously used. There is, consequently, no likelihood of contamination of surface water system, particularly of the city water supply system, from infiltration of effluent at the lagoon.

China↗