[Virus adsorption onto nano-sized iron oxides as affected by different background solutions].

Batch adsorption studies were conducted to investigate virus adsorption onto four commercial nanoparticles of iron oxide as affected by different background solutions, using bacteriophage phiX174 as virus indicator. When artificial ground water was used, the 4 studied nanoparticles showed high virus adsorption capacity, among which alpha-Fe2O3 was the most effective, with the adsorption percent reaching 100% at low initial virus concentration (i.e. 1E + 03 PFU x mL(-1)). Virus adsorption results were described using the Langmuir and Freundlich adsorption isotherms. The estimated adsorption parameters indicated the presence of multilayer adsorption and favorable adsorption. The adsorption percentage by the studied nanoparticles increased with decreasing virus initial concentration. Our results further showed that higher ionic strength of the background solution reduced the virus adsorption, indicating that electrostatic interaction likely dominated the virus adsorption. The presence of anions in the background solution reduced the virus adsorption, probably because of the competitive adsorption between the viruses and anions for sorption sites available, among which HPO4(2-) showed more reduced than HCO3(-). On the other hand, the presence of multivalent cations was favorable for virus adsorption, with bivalent cations (e.g. Ca2+ and Mg2+) showing more favorable than monovalent cations (e.g. Na+ and K+). Results of this study suggest that nanoparticles of iron oxide may be potentially useful for virus removal from infecting water, while other anions or cations in the water should be considered.

[Numerical simulation of isothermal equilibrium adsorption of virus onto typical soils in China].

An isothermal batch experiment was conducted in the laboratory to compare adsorption of bacteriophages MS2 and phiX174 onto 6 different soils (red loam soil, red clay soil, wushan soil, huangni soil, sandy fluvo-aquic soil and loamy fluvo-aquic soil) in China. Soils with sterilized or non-sterilized treatment were used. Relative coefficients of each numerical simulation of the isotherms using three models were evaluated. The results show that the properties of the soil and virus, and presence/absence of the soil autochthonous microorganisms have pronounced effect on the virus adsorption. Both MS2 and phiX174 are almost completely adsorbed by the red clay soil, but minimal adsorption is observed in the two fluvo-aquic soils. Adsorption of phiX174 to all the non-sterilized soils is generally much greater than that of MS2, while sterilization leads to opposite results. Freundlich and Langmuir isotherms are found to have better coefficients to simulate the apparent steady-state virus concentrations. Freundlich isotherm is capable of demonstrating the effect of virus concentration on adsorption behavior. Langmuir isotherms can be used to compare relative adsorption among treatments, while the present study suggests that maximum adsorption can not be calculated when using the Langmuir isotherms.

[Virus adsorption from batch experiments as influenced by air-water interface].

The presence of air-water interface in batch sorption experiments may result in inaccurate estimation of virus adsorption onto various soils. A batch sorption experiment was conducted to compare the adsorption results of MS2 in different soils under presence/absence of air-water interface. Soils with sterilization/nonterilization treatment were used. Virus recovery efficiency in a blank experiment (no soil) was also evaluated as affected by different amount of air-water interface. The presence of air-water interface altered the results of virus adsorption in different soils with different extent, with Sandy fluvo-aquic soil being the most considerably affected, followed by Red loam soil, and the least being Red clay soil, probably because of different soil properties associated with virus adsorption/inactivation. Soil sterilization resulted in more significant difference of virus adsorption onto the Sandy fluvo-aquic soil between the presence and absence of air-water interface, while a reduced difference was observed in the Red loam soil. The presence of air-water interface significantly decreased virus recovery efficiency, with the values being decreased with increase in the amount of air-water interface. Soil particles likely prohibit viruses from reaching the air-water interface or alter the forces at the solid-water-air interface so that the results from the blank experiment did not truly represent results from control blank, which probably resulted in adsorption difference between presence and absence of the air-water interface.