One-pot self-assembly of 3D CdS-graphene aerogels with superior adsorption capacity and photocatalytic activity for water purification

Assessment of the effective parameters for the enhancement of light-harvesting power in the photoelectrochemical microbial fuel cell

Photo-assisted microbial fuel cells (PMFCs) are novel bioelectrochemical systems that employ light to harvest bioelectricity and efficient contaminant reduction. In this study, the impact of different operational conditions on the electricity generation outputs in a photoelectrochemical double chamber configuration Microbial fuel cell using a highly useful photocathode are evaluated and their trends are compared with the photoreduction efficiency trends. As a photocathode, a binder-free photo electrode decorated with dispersed polyaniline nanofiber (PANI)-cadmium sulphide Quantum Dots (QDs) is prepared here to catalyse the chromium (VI) reduction reaction in a cathode chamber with an improvement in power generation performance. Bioelectricity generation is examined in various process conditions like photocathode materials, pH, initial concentration of catholyte, illumination intensity and time of illumination. Results show that, despite the harmful effect of the initial contaminant concentration on the reduction efficiency of the contaminant, this parameter exhibits a superior ability for improving the power generation efficiency in a Photo-MFC. Furthermore, the calculated power density under higher light irradiation intensity has experienced a significant increase, which is due to an increment in the number of photons produced and an increase in their chance of reaching the electrodes surface. On the other hand, additional results indicate that the power generation decreases with the rise of pH and has witnessed the same trend as the photoreduction efficiency.

Investigation of operation parameters on the removal efficiency of methyl orange pollutant by cellulose/zinc oxide hybrid aerogel

In this study, Cellulose/Zinc Oxide-x (CA/ZnO-x) hybrid aerogel with various concentrations of Zn²⁺ ion is synthesized through the hydrothermal method and used for organic pollutant removal. The CA/ZnO-x hybrid aerogel was characterized by XRD, UV-Visible, DRS, FTIR, FESEM, EDS, BET, LC-MS-MS analyses. In the present study, CA/ZnO-x hybrid aerogel as photocatalyst was used to investigate the influence of the photocatalytic degradation of methyl orange (MO) from an aqueous solution under UV irradiation. The morphology of CA/ZnO-x hybrid aerogels exhibited that the ZnO rice grain-like shape were successfully synthesized on the cellulose aerogel matrix. Also, the influence of various factors such as photocatalyst dosage, pH, initial concentration of MO, and irradiation intensity was investigated on the photocatalytic degradation rate of MO. The results revealed that the highest degradation efficiency and mineralization rate of MO were about 99.02% and 51.68%, respectively, after 90 min under UV irradiation using CA/ZnO-0.4 photocatalyst when pH = 3, C₀ = 10 ppm, photocatalyst dose = 9 g L^-1 under the 300 W UV light irradiation. Furthermore, the synthesized photocatalyst exhibited a considerable firmness and easily separated from an aqueous solution for reuse.

Impact of Doping and Additive Applications on Photocatalyst Textural Properties in Removing Organic Pollutants: A Review

The effect of ion doping and the incorporation of additives on photocatalysts’ textural properties have been reviewed. Generally, it can be summarised that ion doping and additives have beneficial effects on photocatalytic efficiency and not all have an increase in the surface area. The excessive amount of dopants and additives will produce larger aggregated particles and also cover the mesoporous structures, thereby increasing the pore size (Pd) and pore volume (Pv). An excessive amount of dopants also leads to visible light shielding effects, thus influence photocatalytic performance. Ion doping also shows some increment in the surface areas, but it has been identified that synergistic effects of the surface area, porosity, and dopant amount contribute to the photocatalytic performance. It is therefore important to understand the effect of doping and the application of additives on the textural properties of photocatalysts, thus, their performance. This review will provide an insight into the development of photocatalyst with better performance for wastewater treatment applications.

Fabrication of S-scheme CdS-g-C3N4-graphene aerogel heterojunction for enhanced visible light driven photocatalysis

Constructing S-scheme heterojunction photocatalysts reveals a greatly improved separation efficiency of photogenerated carriers and enhanced harvesting ability of solar energy in photocatalytic field. Herein, a ternary CdS-g-C₃N₄-GA heterojunction has been fabricated by a facile ultrasound strategy, which behaved as a S-scheme heterojunction with an intimate interface formed, and GA played as an electronic transportation platform to promote the separation of photo-induced charge carriers, which was certified through photoelectrochemical techniques. Density functional theory calculations revealed that the different component in ternary CdS-g-C₃N₄-GA heterojunction demonstrated an obvious difference of work function, resulting in the charge transfer from CdS to g-C₃N₄ through GA with S-scheme principle. In the optimized conditions, the S-scheme CdS-g-C₃N₄-GA heterojunction not only displayed greatly enhanced photocatalytic performances for degradation of dye and antibiotic wastewater, but also improved photocatalytic H₂ production activity. In addition, the photocatalytic mechanism and driving force of charge transfer and separation in S-scheme CdS-g-C₃N₄-GA heterojunction were studied. This study offers a feasible strategy to construct a ternary S-scheme heterojunction for environmental and energy photocatalysis.

Three dimensional graphene materials doped with heteroatoms for extraction and adsorption of environmental pollutants in wastewater

Environmental pollution by heavy metal ions, organic pollutants, oils, pesticides or dyes is a ubiquitous problem adversely affecting human health and environmental ecology. Development and application novel adsorbents in full-scale treatment systems with effectiveness properties could effective ways to facilitate the extraction and adsorption of environment pollutants from wastewater. Graphene materials have drawn much attention due to their extraordinary electron mobilities, high surface areas, good thermal conductivities, and excellent mechanical properties. Three-dimensional graphene materials can provide the inherent advantages of 2D graphene sheets and exhibit micro/nanoporous structures, increased specific surface areas, high electron conductivities, fast mass transport kinetics, and strong mechanical strength. Potential applications for 3D graphene materials include environmental remediation, chemical and biological sensing, catalysis, and super capacitors. Recent advances in the applications of 3D functionalized graphene materials (3D FGMs) doped with heteroatoms for the extraction and adsorption of environmental pollutants in wastewater are summarized in this review.