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Contamination of soils with persistent organic pollutants (POPs), such as organochlorine pesticide, polybrominated diphenyl ethers, halohydrocarbon, polycyclic aromatic hydrocarbons (PAHs) is of increasing concern. Microbial degradation is potential mechanism for the removal of POPs, but it is often restricted by low bioavailability of POPs. Thus, it is important to enhance bioavailability of POPs in soil bioremediation. A series of reviews on bioavailability of POPs has been published in the past few years. However, bioavailability of POPs in relation to soil organic matter, minerals and soil microbes has been little studied. To fully understand POPs bioavailability in soil, research on interactions of POPs with soil components and microbial responses in bioavailability limitation conditions are needed. This review focuses on bioavailability mechanisms of POPs in terms of sorption, transport and microbial adaptation, which is particularly novel. In consideration of the significance of bioavailability, further studies should investigate the influence of various bioremediation strategies on POPs bioavailability. [ABSTRACT FROM AUTHOR]

The presence of exogenous carbonaceous materials (ECMs) in organic contaminated soil is widespread because of their intentional application as carbonaceous amendments (e.g. biochar and activated carbon) or unintentional discharge (e.g. carbon nanomaterials). Most research so far has focused on the sorption behaviors of ECMs in soil. However, the impact of ECMs on the bioavailability of organic pollutants (OPs) and their ecological damages remain unclear. This paper presents an overview on how the ECMs affect bioavailability of OPs to different organisms, such as microorganisms, plants and earthworms. This is affected by different biological response and properties of ECMs. Moreover, the possible risks of ECMs on soil biota are also discussed at different level. This review presents a unique insight into risk assessment of ECMs. Further researches should focus on possible change in physicochemical characteristics of ECMs when exposed to the natural environment and the consequent influence on their sorption ability and ecotoxicity outcomes. [ABSTRACT FROM AUTHOR]

Fishbone is a major by-product of fishing processing and how to deal with the increasingly generated fishbone has been a big challenge. In an effort to convert the low-value waste into valuable material, this research explores the valorization of fishbone biowaste, which can be transformed into biochar as a persulfate activator for phenol removal. The fishbone derived biochar (FBBC) was prepared by one-step pyrolysis without additional template. The catalytic efficiency of FBBC increases with pyrolysis temperature, with FBBC-800 (pyrolyzed at 800 °C) exhibiting the best performance of 100% phenol (20 mg/L) removal within 60 min at the catalyst dosage of 0.1 g/L, which is comparable to other recently reported carbon-based catalysts but with the advantage of easy preparation, low cost and wastes valorization. The high efficacy of FBBC-800 is related to its large surface area (758.44 m2/g), carbonyl group and defective structure. In the FBBC-800/peroxydisulfate/phenol system, both radical and non-radical pathways are involved, among which hydroxyl radical is more important in radical pathway while singlet oxygen dominates in non-radical pathway. Electron transfer plays a key role in this process through electron capture experiment and electrochemical characterization. This study proposes a new strategy for the valorization of fishbone, and provides the guidance for the structure design of carbon-based catalyst for persulfate activation. Image 1 • A new strategy for fishbone valorization was developed. • The fishbone derived biochar is cost effective and easy to prepare. • High surface area, carbonyl group and defective structure contribute to the catalytic activity. • SO 4 · −, · OH, O 2 · − and 1O 2 were identified in the catalytic reaction. • Electron transfer mechanism for pollutant degradation was proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • CNMs have been of scientific and technological interest in photocatalysis. • Selective preparation processes of CNMs are summarized. • CNM reveals size- and surface-dependent properties in photocatalytic process. • The role of CNMs play in the enhancement of photocatalytic performance is discussed. Abstract Highly-efficient materials and technologies for environmental pollutant treatment and hydrogen production are urgently needed in "green" 21st century. Notably, photocatalytic process over carbon nanomaterials (CNMs)-modified photocatalysts is an effective solution for these crises. CNMs (e.g., fullerenes, carbon nanotubes, graphene, carbon nanofibers, and carbon quantum dots) reveal remarkable morphological, mechanical, electrical and optical properties, which have been of significantly scientific and technological interest in photocatalysis. Until now, many efforts have been made to take advantage of these unique size- and surface-dependent properties of CNMs for photocatalytic process. In this review, we firstly summarize selective preparation of CNMs that has a great impact on their photocatalytic performance. Then we provide an updated outline of advanced photocatalytic application of CNMs in addressing both environmental pollution and hydrogen energy crisis. The difference in the role of various CNMs play in the enhancement of photocatalytic performance is also discussed. Lastly, we discuss the limitations of CNMs applied in photocatalysis or even wider fields. We hope this review will project a fast developmental path with providing a wide view of recent preparation methods, applications, prospects and challenges. [ABSTRACT FROM AUTHOR]

To develop a metal-free biochar with high and inherent catalytic activity towards refractory and highly toxic contaminants in advanced oxidation processes, it is necessary to explore its reaction pathways and responsible catalytic sites. Herein, a metal-free biochar derived from corn cob (CCBC) was prepared and used for reaction pathway analysis during peroxydisulfate (PDS) activation. The pyrolysis temperature played an important role for regulating the biochar structure and properties, and CCBC obtained at 800 °C showed the best adsorption capacity and catalytic activity towards five typical organic pollutants, including 2, 4-dichlorophenol, Tetracycline hydrochloride, Ciprofloxacin, Methyl orange and Rhodamine B, due to its richer pore and defect structure. Further treatment of pharmaceutical wastewater demonstrated the good efficiency and potential of this metal-free catalyst for practical application. Radical (58% contribution) and non-radical (42% contribution) pathways were both found in CCBC/PDS system. More importantly, further redox experiments manifested that the carbon framework (defects, sp 2 -hybrid carbon, etc.) only made a contribution to the free radical pathway, while the ketone group (C O) of CCBC was proved to be mainly responsible for the non-radical pathway, namely the generation of singlet oxygen (1O 2). Image 1 • Porosity and defects facilitate adsorption and catalytic performance. • Radical and non-radical pathways were both found in the system. • C=O and defects on the carbon framework were two key active sites. • Carbon frame only contributed to free radicals and 1O 2 was mainly generated by C=O. • CCBC was effective to pharmaceutical wastewater and organics degradation. [ABSTRACT FROM AUTHOR]