As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

http://faculty.wwu.edu/~shulld/ESCI%20101/Andrady2011Plastics.pdf

Microplastics in the marine environment

Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

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Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry

Biochar as a sorbent for contaminant management in soil and water: a review.

http://hywr.kuciv.kyoto-u.ac.jp/lecture/gss/SBabel/E3-20130118PM/Hazardous%20material_2003.pdf

Low-cost adsorbents for heavy metals uptake from contaminated water: a review.

Recombination-assisted megaprimer (RAM) cloning.

This study investigates a simple method for the preparation of floating photocatalysts in which the surface of expanded polystyrene (EPS) is partially dissolved using a diluted solvent that contains TiO2 particles. The acetone volume content (v/v) and TiO2 weight content (w/v) of the diluted solvent and the stirring time of the diluted solvent and EPS were optimized through methylene blue (MB) oxidation experiments. The surface morphology, TiO2 weight ratio, and functional group of the EPS–TiO2 composite (TiEPS) were characterized. Ethyl acetate, benzene, and acetone were selected as suitable solvents for dilution using this simple preparation method. MB degradation efficiency of the TiEPS remained stable over 20 reuse cycles, and minimal TiO2 leaching was observed (up to 3.6 μg L−1 of titanium). Photocatalytic reduction of Cr(VI) in wastewater from a plating plant was evaluated via a composite prepared using waste expanded polystyrene (W-TiEPS). More than 99% of the Cr(VI) was reduced to Cr(III) within 75 min by W-TiEPS amended with citric acid under UV-A irradiation (λmax = 350 nm, 3.93 × 10−9 einstein per cm2 s−1). These results suggest that the floating photocatalyst produced via this simple and scalable method should be considered to remove Cr(VI) and perhaps other water and wastewater contaminants.

Simple preparation method for Styrofoam–TiO2 composites and their photocatalytic application for dye oxidation and Cr(VI) reduction in industrial wastewater

Introduction to Bioremediation

Given the widespread use of TiO2, its release into aquatic systems and complexation with dissolved organic matter (DOM) are highly possible, making it important to understand how such interactions affect photocatalytic activity under visible light. Here, we show that humic acid/TiO2 complexes (HA/TiO2) exhibit photoactivity (without significant electron-hole activation) under visible light through ligand-to-metal charge transfer (LMCT). The observed visible-light activities for pollutant removal and bacterial inactivation are primarily linked to the generation of H2O2 via the conduction band. By systematically considering molecular-scale interactions between TiO2 and organic functional groups in HA, we find a key role of phenolic groups in visible-light absorption and H2O2 photogeneration. The photochemical formation of H2O2 in river waters spiked with TiO2 is notably elevated above naturally occurring H2O2 generated from background organic constituents due to LMCT contribution. Our findings suggest that H2O2 generation by HA/TiO2 is related to the quantity and functional group chemistry of DOM, which provides chemical insights into photocatalytic activity and potential ecotoxicity of TiO2 in environmental and engineered systems.

Visible-Light Activation of a Dissolved Organic Matter-TiO2 Complex Mediated via Ligand-to-Metal Charge Transfer.

The laboratory-scale aerobic sludge process was used to treat municipal sewage using a novel energy-saving aeration strategy. For comparison, two strategies of regulation (reducing the aeration directly and reducing the aeration gradually) were operated in parallel. Results showed that using an operation strategy with reduced aeration during the famine period led to a significant reduction of energy consumption (p < 0.01). Much of the aerobic sludge was washed out and granular sludge disintegrated irreversibly when the direct reduction of aeration was applied; the MLSS dropped gradually from 6.33 g L−1 to 1.94 g L−1 and the SVI reached 325 mL g−1. At the same time, the zeta potential and sludge yield rose from −17.3 mV and 1.13 kg MLSS per kg COD to −20.7 mV and 1.96 kg MLSS per kg COD, respectively. The removal efficiency of NH4+-N, TN and COD decreased to 61%, 48% and 82%, respectively. Leadbetterella spp., which belongs to the phylum Sphingobacteria, became the dominant microorganism in the bioreactor. By contrast, when the gradient reduced aeration strategy was applied, Shannon diversity indices increased significantly (p < 0.01) and the aerobic granular structure remained stable, revealing that the richness and diversity of the aerobic sludge were retained. FISH results revealed that the enrichment of functional microorganisms such as Zoogloea spp. for EPS secretion enriched in the inner part of the granular sludge. Results of 2-DE demonstrated that four extracellular proteins PPIase, pyrophosphate phosphohydrolase, OprF and OMP, which can secrete EPS, were enriched in the stable granules under the condition of gradient reduced aeration. Therefore, a scientific method to regulate the structural stability of the aerobic granular sludge was achieved in this study.

Pedro J. J. Alvarez

Papers

Recombination-assisted megaprimer (RAM) cloning.

Simple preparation method for Styrofoam–TiO2 composites and their photocatalytic application for dye oxidation and Cr(VI) reduction in industrial wastewater

Introduction to Bioremediation

Visible-Light Activation of a Dissolved Organic Matter-TiO2 Complex Mediated via Ligand-to-Metal Charge Transfer.

Gradient reduced aeration in an enhanced aerobic granular sludge process optimizes the dominant microbial community and its function