ABSTRACT
The adsorption behaviors of a silica-based hybrid donor adsorbent (TAMIA-EH+1-dodecanol)/SiO2-P towards Pd(II) were investigated under the effect of the contact time, temperature etc. in simulated high-level liquid waste. The adsorption rates of Pd(II) and Re(VII) were fairly fast and could reach the equilibrium state in only 1 h compared with other co-existing metal ions. The adsorption kinetics of Pd(II) was found to fit well with the pseudo-first order model. Even though with increasing the concentration of HNO3 above 1 M, the adsorption performance of (TAMIA-EH+1-dodecanol)/SiO2-P decreased gradually; it still exhibited a better selectivity towards Pd(II) when [HNO3] > 0.5 M. The adsorption isotherms of Pd(II) and Re(VII) were well-described by the Langmuir isotherm model, while the Freundlich isotherm model was considered to be more suitable for the adsorption of Ru(III), Zr(IV) and Mo(VI). A high temperature of an aqueous solution was not good for the effective recovery of Pd(II). The calculated thermodynamic parameters revealed that the adsorption of Pd(II) was exothermic in nature.
ABSTRACT
NADPH:protochlorophyllide oxidoreductase (POR) catalyzes the light-dependent reduction of protochlorophyllide. To elucidate the physiological function of three differentially regulated POR isoforms (PORA, PORB and PORC) in Arabidopsis thaliana, we isolated T-DNA tagged null mutants of porB and porC. The mature seedlings of the mutants had normal photosynthetic competencies, showing that PORB and PORC are interchangeable and functionally redundant in developed plants. In etiolated seedlings, only porB showed a reduction in the photoactive protochlorophyllide and the size of prolamellar bodies (PLBs), indicating that PORB, as well as PORA, functioned in PLB assembly and photoactive protochlorophyllide formation in etiolated seedlings. When illuminated, the etiolated porB seedling was able to green to a similar extent as the wild type, whereas the greening was significantly reduced under low light conditions. During greening, high light irradiation increased the level of PORC protein, and the greening of porC was repressed under high light conditions. The porB, but not porC, etiolated seedling was more sensitive to the far-red block of greening than the wild type, which is caused by depletion of endogenous POR proteins resulting in photo-oxidative damage. These results suggest that, at the onset of greening, PLBs are important for efficient capture of light energy for photoconversion under various light conditions, and PORC, which is induced by high light irradiation, contributes to photoprotection during greening of the etiolated seedlings.
