Biochar-assisted Fenton-like oxidation of benzo[a]pyrene-contaminated soil

Insight into the High-Efficiency Benzo(a)pyrene Degradation Ability of Pseudomonas benzopyrenica BaP3 and Its Application in the Complete Bioremediation of Benzo(a)pyrene

Polycyclic aromatic hydrocarbons (PAHs) are common carcinogens. Benzo(a)pyrene is one of the most difficult high-molecular-weight (HMW) PAHs to remove. Biodegradation has become an ideal method to eliminate PAH pollutants from the environment. The existing research is mostly limited to low-molecular-weight PAHs; there is little understanding of HMW PAHs, particularly benzo(a)pyrene. Research into the biodegradation of HMW PAHs contributes to the development of microbial metabolic mechanisms and also provides new systems for environmental treatments. Pseudomonas benzopyrenica BaP3 is a highly efficient benzo(a)pyrene-degrading strain that is isolated from soil samples, but its mechanism of degradation remains unknown. In this study, we aimed to clarify the high degradation efficiency mechanism of BaP3. The genes encoding Rhd1 and Rhd2 in strain BaP3 were characterized, and the results revealed that rhd1 was the critical factor for high degradation efficiency. Molecular docking and enzyme activity determinations confirmed this conclusion. A recombinant strain that could completely mineralize benzo(a)pyrene was also proposed for the first time. We explained the mechanism of the high-efficiency benzo(a)pyrene degradation ability of BaP3 to improve understanding of the degradation mechanism of highly toxic PAHs and to provide new solutions to practical applications via synthetic biology.

Natural iron minerals in an electrocatalytic oxidation system and in situ pollutant removal in groundwater: Applications, mechanisms, and challenges

Natural iron-bearing minerals are widely distributed in the environment and show prominent catalytic performance in pollutant removal. This work provides an overview of groundwater restoration technologies utilizing heterogeneous electro-Fenton (HEF) techniques with the aid of different iron forms as catalysts. In particular, applications of natural iron-bearing minerals in groundwater in the HEF system have been thoroughly summarized from either the view of organic pollutant removal or degradation. Based on the analysis of the catalytic mechanism in the HEF process by pyrite (FeS₂), goethite (α-FeOOH), and magnetite (Fe₃O₄) and the geochemistry analysis of these natural iron-bearing minerals in groundwater, the feasibility and challenges of HEF for organic degradation by using typical iron minerals in groundwater have been discussed, and natural factors affecting the HEF process have been analyzed so that appropriate in situ remedial measures can be applied to contaminated groundwater.

Waste to catalyst: Role of agricultural waste in water and wastewater treatment

Presently, owing to the rapid development of industrialization and urbanization activities, a huge quantity of wastewater is generated that contain toxic chemical and heavy metals, imposing higher environmental jeopardies and affecting the life of living well-being and the economy of the counties, if not treated appropriately. Subsequently, the advancement in sustainable cost-effective wastewater treatment technology has attracted more attention from policymakers, legislators, and scientific communities. Therefore, the current review intends to highlight the recent development and applications of biochars and/or green nanoparticles (NPs) produced from agricultural waste via green routes in removing the refractory pollutants from water and wastewater. This review also highlights the contemporary application and mechanism of biochar-supported advanced oxidation processes (AOPs) for the removal of organic pollutants in water and wastewater. Although, the fabrication and application of agriculture waste-derived biochar and NPs are considered a greener approach, nevertheless, before scaling up production and application, its toxicological and life-cycle challenges must be taken into account. Furthermore, future efforts should be carried out towards process engineering to enhance the performance of green catalysts to improve the economy of the process.

Biochar Effect on the Benzo[a]pyrene Degradation Rate in the Cu Co-Contaminated Haplic Chernozem under Model Vegetation Experiment Conditions

The research of the fundamentals of the behavior of behavior in the soil–plant system during their co-contamination is of high interest because of the absence of technologies for the creation of effective, environmentally friendly and cost-effective remediation methods, as well as integrated systems for predicting the quality of soils co-contaminated with HMs and PAHs. The unique model vegetation experiment was studied with Haplic Chernozem contaminated by one of the priority organic toxicants, benzo[a]pyrene (BaP), applied alone and co-contaminated with Cu with the subsequent vegetation of tomato (Solanum lycopersicum) and spring barley plants (Hordeum sativum Distichum). Biochar obtained from sunflower husks was used as a sorbent for the remediation of the contaminated soil. It was established that by increasing the BaP amount applied to the soil, the rate of BaP degradation improved. The effect was enhanced in the presence of biochar and decreased in the case of joint co-contamination with Cu, which is especially expressed for the soil of tomato plants. The half-degradation time of the BaP molecule varied from 8 up to 0.2 years for tomatoes and barley.

Efficiency of Penicillium canescens in Dissipating PAH in Industrial Aged Contaminated Soil Microcosms and Its Impact on Soil Organic Matter and Ecotoxicity

The filamentous fungus Penicillium canescens, isolated from oil-polluted soil, was evaluated for its ability to dissipate high-molecular-weight polycyclic aromatic hydrocarbons (PAH). The study was conducted in a microcosm containing 180 g of historical PAH-contaminated soil under non-sterile conditions with two incubation temperatures (14 °C and 18 °C) on a 12-h cycle. The experiment was conducted over 8 months, with four experimental conditions created by varying the volumes of the bulking agent and vegetable oil (olive oil) and the time of addition of these compounds. The PAH dissipation performance of the fungal augmentation treatment was compared with that achieved with a biostimulated soil (bulking agent and vegetable oil) and with the untreated soil as control. The greatest PAH dissipation was obtained with P. canescens bioaugmentation (35.71% ± 1.73), with 13 of the 16 US EPA PAH significantly dissipated, at rates above 18%, and particularly high-molecular-weight PAH, composed of more than three fused aromatic rings. Nematode toxicity tests indicated a significant decrease in the toxicity of soil bioaugmented by this fungus. Fulvic and humic contents were significantly increased by this treatment. All these results suggest that bioaugmentation with P. canescens can be used to restore soils with long-term PAH contamination.