Photocatalytic degradation of VOCs from air stream using Mo:TiO2/GAC nanocomposites

Modification of TiO2 is one of the techniques used to enhance its photodegradation efficiency and to make it visible-light-active. In this study, Mo-doped TiO2 nanoparticles were synthesized using a fast sol-gel technique, and then coated on granular activated carbon (GAC) as both substrate and adsorbent to obtain Mo:TiO2/GAC composite. The fabricated composite was characterized using powder XRD, SEM, EDAX, FTIR, and BET analysis. Then the composite was applied to photodegrade volatile organic compounds (VOCs) under both UV and visible light irradiation. The characterization results showed high crystallinity and purity. Mo:TiO2/GAC composite had higher photodegradation efficiency compared with bare TiO2 and bare GAC. Moreover, studying operational parameters showed that the optimum condition for photodegradation efficiency of VOCs was at flowrate of 1 l/min, VOCs concentration of 20 ppm, and light intensity of 400 and 600 W/m2 for UV and visible light respectively. The results suggest that Mo:TiO2/GAC is a visible-light-active composite and can be acceptably used to decompose VOCs under visible light with adequate efficiency and without the generation of harmful by-products such as O3 as compared with UV.

Photocatalytic Reduction of CO2 to Methanol by Cu2O/TiO2 Heterojunctions

The conversion of CO2 to low-carbon fuels using solar energy is considered an economically attractive and environmentally friendly route. The development of novel catalysts and the use of solar energy via photocatalysis are key to achieving the goal of chemically reducing CO2 under mild conditions. TiO2 is not very effective for the photocatalytic reduction of CO2 to low-carbon chemicals such as methanol (CH3OH). Thus, in this work, novel Cu2O/TiO2 heterojunctions that can effectively separate photogenerated electrons and holes were prepared for photocatalytic CO2-to-CH3OH. More visible light-active Cu2O in the Cu2O/TiO2 heterojunctions favors the formation of methanol under visible light irradiation. On the other hand, under UV-Vis irradiation for 6 h, the CH3OH yielded from the photocatalytic CO2-to-CH3OH by the Cu2O/TiO2 heterojunctions is 21.0–70.6 µmol/g-catalyst. In contrast, the yield of CH3OH decreases with an increase in the Cu2O fraction in the Cu2O/TiO2 heterojunctions. It seems that excess Cu2O in Cu2O/TiO2 heterojunctions may lead to less UV light exposure for the photocatalysts, and may decrease the conversion efficiency of CO2 to CH3OH.

New Aptamer/MoS2/Ni-Fe LDH Photoelectric Sensor for Bisphenol A Determination

Here, a new type of PEC aptamer sensor for bisphenol A (BPA) detection was developed, in which visible-light active MoS2/Ni-Fe LDH (layered double hydroxide) heterostructure and aptamer were used as photosensitive materials and biometric elements, respectively. The combination of an appropriate amount of MoS2 and Ni-Fe LDH enhances the photocurrent response, thereby promoting the construction of the PEC sensor. Therefore, we used a simple in situ growth method to fabricate a MoS2/Ni-Fe LDH sensor to detect the BPA content. The aptasensor based on aptamer/MoS2/Ni-Fe LDH displayed a linear range toward a BPA of 0.05–10 to 50–40,000 ng L−1, and it has excellent stability, selectivity and reproducibility. In addition, the proposed aptamer sensor is effective in evaluating real water samples, indicating that it has great potential for detecting BPA in real samples.

Antibiotics Contaminated Irrigation Water: An Overview on Its Impact on Edible Crops and Visible Light Active Titania as Potential Photocatalysts for Irrigation Water Treatment

Sub-therapeutic levels of antibiotics (ABs) are given to animals and poultry to promote growth and reduce disease. In agricultural environments, ABs reach croplands via animal manure used as fertilizer and/or ABs-contaminated water used for irrigation. The continuous discharge of ABs into the ecosystem raises growing concerns on the ABs contamination of edible crops. Tetracyclines (TCs) are among the most widely used ABs around the world. In this review, we discuss the contamination of irrigation water with TCs, its impact on edible crops, and the potential risks of crop contamination with TCs on human health. We propose solar-mediated photocatalytic degradation using Titania (TiO2) photocatalyst as a promising method to remove TCs from irrigation water. The photocatalytic activity of TiO2 can be enhanced by chemical modification to expand its activity under visible light irradiation. Herein, we aim for providing literature-based guidance on developing a visible light–active TiO2-based system to degrade TCs and other ABs in water streams. We include a summary of recent advances on this topic based on three main modification methods of Titania: metal/non-metal/mixed doping, composite formation, and heterojunction construction. Among the investigated photocatalysts, Fe2O3-TiO2/Fe-zeolite and the N-doped TiO2/rGO immobilized composite catalysts were found to be very efficient in the degradation of TCs under visible light irradiation (i.e., 98% degradation within 60 min). Most immobilized TiO2 based composite systems exhibited improved performances and hence we highlight these as efficient, cost effective and ecofriendly photocatalysts for the degradation of TCs in irrigation water.