Tianyuan Xu

Ag3PO4 immobilized on hydroxy-metal pillared montmorillonite for the visible light driven degradation of acid red 18

This work reports the facile fabrication of Ag3PO4/Fe–Al/Mt and Ag3PO4/Al/Mt by loading Ag3PO4 on hydroxy-iron–aluminum pillared montmorillonite (Fe–Al/Mt) and hydroxy-aluminum pillared montmorillonite (Al/Mt). The structural characteristics of the resulting materials were studied with XRD, SEM-EDS, XPS, ICP, nitrogen adsorption–desorption isotherms, and UV-vis diffuse reflectance spectra; the photocatalytic activity of the obtained catalysts was tested using acid red 18 (AR18) as a model contaminant under visible light irradiation. The obtained results illustrate that Ag3PO4 of a high dispersity and smaller size was successfully loaded on hydroxy-metal pillared montmorillonite. The photocatalytic activity and structural stability of the three synthesized catalysts were in the order Ag3PO4/Fe–Al/Mt > Ag3PO4/Al/Mt > Ag3PO4. An efficiency of 98.5% was achieved for AR18 degradation by Ag3PO4/Fe–Al/Mt after recycling seven times, while only 54.9% was achieved for Ag3PO4. The superoxide radical anion (O2˙−) was confirmed to be the dominant reactive species in all the three degradation systems, and the Ag3PO4/Fe–Al/Mt system formed the largest amount of O2˙−. Except for the larger specific surface area and smaller particle size, the high removal efficiency of AR18, remarkable O2˙− generation performance, and good stability of Ag3PO4/Fe–Al/Mt could be attributed to the presence of Fe3+ as well, which can act as an electron acceptor for photo-induced electrons from Ag3PO4 during the photocatalytic process and then inhibit the transformation of Ag+ into metallic Ag.

Fullerene modification of Ag3PO4 for the visible-light-driven degradation of acid red 18

This work synthesized a C60/Ag3PO4 composite via the modification of Ag3PO4, by incorporation of an acid treated fullerene (C60), with the aim of improving the photocatalytic activity and stability of Ag3PO4. XRD, SEM, Raman, XPS, PL, and UV-vis DRS were used to study the structural characteristics of the obtained photocatalysts. Acid red 18 (AR18) was adopted to evaluate the photocatalytic activity of the as-prepared photocatalysts under visible light irradiation. The results showed that C60 was successfully hybridized with Ag3PO4, and the C60/Ag3PO4 composite showed higher photocatalytic activity and better stability than Ag3PO4. The enhancement of photocatalytic activity strongly depended on the amount of C60 on Ag3PO4, and the optimum amount was found to be a weight ratio of 2% (C60/Ag3PO4). Superoxide radical anions (O2˙−) were confirmed to be the main participants in the degradation of AR18, determined by the active free radical capture experiments, and O2˙− production by 2% C60/Ag3PO4 was nearly 1.5 times higher than that by Ag3PO4. The superior photocatalytic activity and stability of C60/Ag3PO4 could be attributed to the presence of C60, which can not only be used as an electron acceptor for photo-induced electrons from Ag3PO4 to reduce the recombination of photo-induced electron–hole pairs, but also to improve O2˙− production during the photocatalysis process.

Pyrite Passivation by Triethylenetetramine: An Electrochemical Study

The potential of triethylenetetramine (TETA) to inhibit the oxidation of pyrite in H2SO4 solution had been investigated by using the open-circuit potential (OCP), cyclic voltammetry (CV), potentiodynamic polarization, and electrochemical impedance (EIS), respectively. Experimental results indicate that TETA is an efficient coating agent in preventing the oxidation of pyrite and that the inhibition efficiency is more pronounced with the increase of TETA. The data from potentiodynamic polarization show that the inhibition efficiency (η%) increases from 42.08% to 80.98% with the concentration of TETA increasing from 1% to 5%. These results are consistent with the measurement of EIS (43.09% to 82.55%). The information obtained from potentiodynamic polarization also displays that the TETA is a kind of mixed type inhibitor.

Interaction of polyhydroxy fullerenes with ferrihydrite: adsorption and aggregation

The rapid development of nanoscience and nanotechnology, with thousands types of nanomaterials being produced, will lead to various environmental impacts. Thus, understanding the behaviors and fate of these nanomaterials is essential. This study focused on the interaction between polyhydroxy fullerenes (PHF) and ferrihydrite (Fh), a widespread iron (oxyhydr)oxide nanomineral and geosorbent. Our results showed that PHF were effectively adsorbed by Fh. The adsorption isotherm fitted the D-R model well, with an adsorption capacity of 67.1mg/g. The adsorption mean free energy of 10.72kJ/mol suggested that PHF were chemisorbed on Fh. An increase in the solution pH and a decrease of the Fh surface zeta potential were observed after the adsorption of PHF on Fh; moreover, increasing initial solution pH led to a reduction of adsorption. The Fourier transform infrared spectra detected a red shift of C-O stretching from 1075 to 1062cm-1 and a decrease of Fe-O bending, implying the interaction between PHF oxygenic functional groups and Fh surface hydroxyls. On the other hand, PHF affected the aggregation and reactivity of Fh by changing its surface physicochemical properties. Aggregation of PHF and Fh with individual particle sizes increasing from 2nm to larger than 5nm was measured by atomic force microscopy. The uniform distribution of C and Fe suggested that the aggregates of Fh were possibly bridged by PHF. Our results indicated that the interaction between PHF and Fh could evidently influence the migration of PHF, as well as the aggregation and reactivity of Fh.