Biomedical subjects

Hong-xiao Tang

Publications and source records attributed to Hong-xiao Tang.

8 recordsLinked to original sources

PubMed2006

Solubilization and desorption of methyl-parathion from porous media: a comparison of hydroxypropyl-beta-cyclodextrin and two nonionic surfactants.

The removal of hydrophobic organic compounds (HOCs) from soils and sediments by water flushing is often constrained by sorption interactions. The development of improved methods for remediation of contaminated soils has emerged as a significant environmental priority. Increasing HOCs desorption and mobility in soil using surfactants is considered to be one of the most suitable on-site techniques for soil remediation. A major concern regarding the use of surfactants for environmental restoration is the potential loss to the environment of large amounts of surfactant through sorption of nonionic types. A study was conducted to investigate whether surfactants and cyclodextrins can be used to enhance the transport of methyl-parathion in a contaminated soil. At aqueous concentrations of surfactants tested, the proportion of each surfactant sorbed to the soil increased with increasing surfactant concentrations. The maximal adsorbed mass is about 5,130 and 14,200 microg/g for Brij 35 and Tween 80, respectively. In the case of nonionic surfactants, sorption attenuates surfactant effectiveness by increasing the organic carbon content of the soil matrix and retarding transport of methyl-parathion through batch and soil column experiments. However, in contrast with the surfactants, hydroxypropyl-beta-cyclodextrin (HPCD) does not interact with the soil tested. The nonreactive nature of cyclodextrins, combined with its large affinity for HOCs suggests that it should have an advantage versus adsorbing surfactants for decreasing HOC distribution coefficients in subsurface systems.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2006

[Enhanced coagulation and NOM fractionation study of a typical southern water].

Systematic studies on enhancing normal treatment processes were performed in order to remove aquatic organic matter economically and efficiently. Enhanced coagulation and polymer coagulant-aid coagulation were compared through jar tests and on-spot experiment (Pilot-scale and full-scale experiment). Fractionations of raw water and water after treatments of above two strategies were performed based on selective adsorption of resin DAX-8. It was found that matters causing UV absorbance at 254 nm were well removed by above two treatments; removals of which could be achieved 90% or more. Hydrophobic bases and acids fractions were more removed under enhanced conditions with removals 66% and 35% respectively; while hydrophilic fraction could be better removed by about 45% using polymer coagulant aids. But the whole removals of the two strategies were almost equal.

Chemical Fractionation↗

PubMed2005

Removal of natural organic matter in a typical south-China source water during enhanced coagulation with IPF-PACl.

Systematic investigation on enhancing removal of natural organic matter (NOM) using inorganic polymer flocculant (IPF), polyaluminum chloride (PACl) and polyacrylamide (PAM) was performed in a typical south-China source water. Enhanced coagulation and applying polymer flocculant-aid were compared through jar tests and pilot tests. Raw water and settled water were characterized and fractionated by resin adsorption. The results show that DOC composes major part of TOC. The DOC distribution keeps relatively stable all around the year with typical high amounts of the hydrophilic matter around 50%. The distribution between HoB, HoA and HoN varies and undergoes fluctuation with the year round. During the summer season, the HoN becomes gradually the major part in hydrophobic parts. PACI with the species being tailor-made shows little pH effect during coagulation. The enhanced coagulation dosage for PACI could be 4.5 mg/L for the typical source water. The highest TOC removal achieved 31%. To be economically, 3 mg/L dose is the optimum dosage. Although hydrophilic fractions of NOM of both treatment strategies are removed about 30%, NOM causing UV254. absorbance were well removed(about 90%). Hydrophobic bases and acids fractions are much more removed under enhanced conditions. The hydrophilic fraction could be better removed using PAM, the polymer coagulant aid.

Acrylic Resins↗

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

Kinetics study of aqueous sorption of phenanthrene to humic acids and sediments.

The sorption behavior was determined for a model polycyclic aromatic hydrocarbon (PAH), i.e., phenanthrene(PHN), from water to three humic acids (HAs) and three sediments in different reacting time. The chemical compositions of HA samples were measured using cross polarization magic angle spinning carbon-13 (CPMAS 13C NMR along with elemental analysis. The dissolved humic substances dissociating from solid HAs and sediments were characterized by 'H NMR. The experiments indicated that the sorption modes and mechanisms of natural sorbents for PHN varied significantly between short (< 7 d) and long contact time and the reaction time should be taken into consideration in studying the overall sorption process. The sorption capacity (K'f) and exponent (n) might be relative to the properties of dissolved humic materials in initial stage but the solid aromatic organic matter after long time reaction. According to the experiments performed in this investigation and the previous researches, a conceptive sorption model was established.

Adsorption↗

PubMed2004

Interaction of PACls with sulfate.

This article discusses the influential factors on Al13 separation considering the interaction of sulfate with various polyaluminum chloride (PACl). The experimental results showed that the basicity (B = [OH/[Al]), the concentration of PACl and Al/SO4 ratio exhibited significant roles in the PACl-sulfate reaction. It indicated that different species in various PACl underwent different reaction pathway with sulfate. The Alc, colloidal species, formed precipitation quickly with sulfate, while Alb, oligomers and polymers, underwent slow crystallization. And Ala, monomers, reacted with sulfate to form soluble complexes. The kinetic difference of reaction made it possible to realize the separation of Alb and further purification. The decrease of Ala resulted in the limit of ferron method was also mentioned.

Aluminum Hydroxide↗

PubMed2004

Coagulation of micro-polluted Pearl River water with IPF-PACls.

Water samples collected from early March 2001 to the end of April 2002 at the branch of Pearl River around the Guangzhou City were analyzed for its micro-polluted characteristics. The coagulation behavior of polyaluminum chlorides (PACls) was then examined focusing on the effect of primary water quality and speciation distribution. The results showed that PACls exhibit better coagulation efficiency than alum in accordance with the different speciation. The turbidity removal property of PACls is evidently better than alum at low dosage. While in neutral zone (about 6.5-7.5), the turbidity removal of PACls decreases owing to the restabilization of particles at higher dosage. The organic matters in raw water exhibit marked influence on coagulation. In acidic zone, organic matters complex with polymer species and promote the formation of flocs. With an increase in pH, the complexation of organics with polymer species gradually decreases, and the removal of organics mainly depends on adsorption. The effect is evidently improved with the raise of B value.

Adsorption↗

PubMed2003

Spectroscopic study on variations in illite surface properties after acid-base titration.

FT-IR, Raman microscopy, XRD, 29Si and 27Al MAS NMR, were used to investigate changes in surface properties of a natural illite sample after acid-base potentiometric titration. The characteristic XRD lines indicated the presence of surface Al-Si complexes, preferable to Al(OH)3 precipitates. In the microscopic Raman spectra, the vibration peaks of Si-O and Al-O bonds diminished as a result of treatment with acid, then increased after hydroxide back titration. The varied ratio of signal intensity between (IV)Al and (VI)Al species in 27Al MAS NMR spectra, together with the stable BET surface area after acidimetric titration, suggested that edge faces and basal planes in the layer structure of illite participated in dissolution of structural components. The combined spectroscopic evidence demonstrated that the reactions between illite surfaces and acid-leaching silicic acid and aluminum ions should be considered in the model description of surface acid-base properties of the aqueous illite.

Aluminum↗