TiO2/g-C3N4 photocatalyst for the purification of potassium butyl xanthate in mineral processing wastewater.

In the present work, TiO2-graphite-phase-carbon-nitride (TiO2/g-C3N4) was prepared through a hydrothermal method to obtain a new photocatalytic material. This material was characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray energy spectrometer (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Solid-state UV-Vis diffuse reflectance spectrometry (UV-Vis-DRS) and electron paramagnetic resonance (EPR). The synthesized TiO2/g-C3N4 exhibited homogeneous morphology, in which TiO2 nanoparticles were uniformly distributed on the g-C3N4 nanosheets. Regarding its potential use as photocatalytic material in the treatment of mineral processing wastewater, 18% TiO2/g-C3N4 showed superior photodegradation performance than TiO2 and g-C3N4, to give 97.1% degradation rate under 100 min of simulated light irradiation. The experimental results showed that the successful incorporation of TiO2 on g-C3N4 nanosheets enhanced the spectral response range of TiO2/g-C3N4, and the photocatalytic activity was improved. In view of that, it can be considered that this kind of photocatalytic material has a good prospect in the treatment of mineral processing wastewater, which would have clearly environmental relevance.

Red mud-derived iron carbon catalyst for the removal of organic pollutants in wastewater.

In order to reduce the environmental hazards of red mud (RM) and realize its resource utilization, in this study, RM-based iron-carbon micro-electrolysis material (RM-MEM) were prepared by a carbothermal reduction process using RM as raw material. The influence of the preparation conditions on the phase transformation and structural characteristics of the RM-MEM were investigated during the reduction process. The ability of RM-MEM to remove organic pollutants from wastewater was evaluated. The results showed that RM-MEM prepared at a reduction temperature of 1100 °C, a reduction time of 50 min and a coal dosage of 50% had the best removal effect for the degradation of methylene blue (MB). When the initial MB concentration was 20 mg L-1, the amount of RM-MEM material was 4 g L-1, the initial pH was 7, and the degradation efficiency reached 99.75% after 60 min. When RM-MEM is split into carbon free and iron free parts for use, the degradation effect becomes worse. Compared to other materials, RM-MEM has lower cost and better degradation. X-ray diffraction (XRD) analysis showed that hematite was transformed to zero-valent iron with the increase in the roasting temperature. Scanning electron microscopy (SEM) and energy spectroscopy (EDS) analysis showed that micron-sized ZVI particles were formed in the RM-MEM, and increasing the carbon thermal reduction temperature was beneficial to the growth of zero-valent iron particles.

Facile preparation of visible light-sensitive layered g-C3N4 for photocatalytic removal of organic pollutants.

The graphite-phase carbon nitride (g-C3N4) photocatalytic materials were prepared by one-step calcination method to degrade methylene blue (MB) and potassium butyl xanthate (PBX) under visible light irradiation. The prepared g-C3N4 photocatalytic materials were investigated in detail by various characterizations, and the experiments showed that the graphitic phase carbon nitride photocatalytic materials were successfully prepared by the one-step calcination method. The material possesses excellent optical properties and strong visible light absorption, thus achieving photocatalytic degradation of MB and PBX. The catalyst dosage, pH, the initial concentration of pollutants have important effects on photocatalytic activity of MB and PBX. The photocatalytic degradation efficiency was 98.99% for MB and 96.83% for PBX under the optimal conditions (catalyst dosage, initial pollutant concentration and pH value were 500 mg L-1, 20 mg L-1 and 7, respevtively). The photocatalytic mechanisms on MB and PBX were elucidated. ·OH was the key specie for MB, while ·O2- was the key specie for PBX. This study advances the development of photocatalytic technology for mineral wastewater.