Experimental studies of iron transformations kinetics and autocatalysis during its physicochemical removal from underground water

The mathematical model of physicochemical iron removal from groundwater was developed. It consists of three interrelated compartments. The results of the experimental research provide information in support of the first two compartments of the mathematical model. The dependencies for the concentrations of the adsorbed ferrous iron and deposited hydroxide concentrations are obtained as a result of the exact solution of the system of the mass transfer equations for two forms of iron in relation to the inlet surface of the bed. An analysis of the experimental data of the dynamics of the deposit accumulation in a small bed sample was made, using a special application that allowed to select the values of the kinetic coefficients and other model parameters based on these dependencies. We evaluated the autocatalytic effect on the dynamics of iron ferrous and ferric forms. The verification of the mathematical model was carried out involving the experimental data obtained under laboratory and industrial conditions.

Active sites provided by surface autocatalytic effect and quantum confinement for stable and efficient photocatalytic hydrogen generation

Photocatalytic hydrogen evolution from water is a promising approach for renewable energy generation and storage. However, traditional photocatalysts suffer from limited hydrogen evolution rate due to the lack of active...

Effect of Size on Degradation of Porous Poly(Lactic Acid) Scaffold

Poly (lactic acid) (PLA) scaffolds with different sizes are often fabricated for various requirements. A cellular automaton simulation was used to investigate the effect of the size on the degradation behaviors of porous PLA scaffolds. Four porous PLA scaffolds with 90% initial porosity and different sizes were established by a novel repeat unit method. Mass loss and the change in molecular weight during the degradation were simulated. The results indicate that mass loss is related to the size of the porous scaffold while molecular weight change is independent on the size. With the size of the porous scaffold increasing, the mass loss increases while the difference in mass loss between the scaffolds with different sizes decreases. All these changes can be attributed to the difference in the autocatalytic effect and corresponding oligomer diffusion ability of the porous scaffolds with different sizes.

Photochemical Synthesis of Gold Nanostructures in Different Solvents

Gold nanostructures were synthesized at room temperature under irradiation of a fluorescent lamp in mixture of gold seeds smaller than 10 nm, HAuCl4, and poly(vinylpyrrolidone) (PVP). N,N'-dimethylformamide (DMF), water or ethylene glycol (EG) was used as solvent respectively. The products were characterized by transmission electron microscopy, X-ray diffraction and absorption spectra, and the results indicated that under light irradiation at ambient, the reducibility of the three solvents for HAuCl4 ranked as: EG> water> DMF, all far weaker than that of PVP; PVP also prevented the nanostructures from precipitating; gold seeds seemed to impose an autocatalytic effect to facilitate the reduction of HAuCl4; light irradiation was essential for high-yield production of gold particles; the above factors influenced the morphology and size of the gold structures, and led to formation of particles within nano or micron scale in shape of spheroid, rod or plate.