Synthesis of thiourea-immobilized polystyrene nanoparticles and their sorption behavior with respect to silver ions in aqueous phase.

Although a thiourea-immobilized polystyrene sorbent has been reported to exhibit high Ag+ sorption capacity (135mg/g), it is not stable under the acidic conditions commonly employed for desorption. In this research, we synthesized novel thiourea-immobilized polystyrene (TA-PS) nanoparticles to be highly acid resistant via a two-step procedure from polystyrene nanoparticles: acetylation and the subsequent immobilization of thiourea. We investigated the influences of pH, contact time, and initial concentration of AgNO3 solution on the Ag+ sorption of the polymer nanoparticles and estimated the maximum Ag+ sorption capacity to be 190±5mg/g at a pH of 6. The sorption performance did not significantly decrease in tap water containing competing ions. The sorption kinetic data were well fitted to the pseudo-second-order kinetic model. Overall, the TA-PS nanoparticles exhibited a high Ag+ sorption capacity and high selectivity against alkaline and alkaline earth-metal ions. In particular, their high acid resistance allows them to be used for long time periods in sorption-desorption processes.

Mutation of rpoS enhances Pseudomonas sp. KL28 growth at higher concentrations of m-cresol and changes its surface-related phenotypes.

A Tn5 transposon mutant was isolated of the alkylphenol degrader Pseudomonas sp. KL28 that showed increased growth at higher levels of m-cresol on solid and in liquid cultures. The transposon was inserted at the 5'-terminus of rpoS, which encodes a stationary-phase sigma factor. When grown on agar plates, the rpoS mutant developed prominent wrinkles, especially at lower temperatures, and spread faster on soft agar. In addition, the rpoS mutant had enhanced biofilm-forming ability that was not due to self-produced diffusible signals.