Synthesis and properties of nano-cadmium oxide and its size-dependent responses by barley plant.

Present study included technological methods that made it possible to synthesize CdO nanoparticles and carry out their qualitative and quantitative diagnostics, confirming the as-prepared CdO nanoparticles (NPs) were spherical and had a size of 25 nm. Then, under the conditions of the model experiment the effect of CdO in macro and nanosized particles on absorption, transformation, and structural and functional changes occurring in cells and tissues of Hordeum vulgare L. (spring barley) during its ontogenesis was analyzed. Different analytical techniques were used to detect the transformation of CdO forms: Fourier-transform infrared spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray fluorescence analysis (XRF), Scanning electron microscopy (SEM-EDXMA and TEM), X-ray diffraction (XRD), and X-ray absorption fine structure, consists of XANES - X-ray absorption near edge structure, and EXAFS - Extended X-ray absorption fine structure. Quantitative differences in the elemental chemical composition of barley root and leaf samples were observed. The predominant root uptake of Cd was revealed. CdO-NPs were found to penetrate deeply into barley plant tissues, where they accumulated and formed new mineral phases such as Cd5(PO4)3Cl and CdSO4 according to XRD analysis. The molecular-structural state of the local Cd environment in plant samples corresponding to Cd-O and Cd-Cd. The toxicity of CdO-NPs was found to significantly affect the morphology of intracellular structures are the main organelles of photosynthesis therefore, destructive changes in them obviously reduce the level of metabolic processes ensuring the growth of plants. This study is an attempt to show results how it is possible to combine some instrumental techniques to characterize and behavior of NPs in complex matrices of living organisms.

The effect of resource-saving tillage technologies on the mobility, distribution and migration of trace elements in soil.

The influence of agricultural tillage technologies on the accumulation and distribution of trace elements in the soil is poorly studied. At the same time, intensive agriculture requires large amounts of fertilizers, growth stimulators, pesticides, and other substances, which can effect the ecological safety of the plant products and soil. This paper represents studying the effect of various agricultural techniques (including resource-saving technologies) on the mobility and profile distribution of Pb, Zn, and Cu in Haplic Chernozem. No significant influence of resource-saving tillage technologies was found on the total Pb content. Contrary, the resource-saving tillage technologies was observed to promote the growth of the total Zn and Cu content depending on the cultivation method (by 26% Zn, 34% Cu at minimal tillage, and 28% for both elements using No-till in Ap horizon). Amongst different applied agrotechnologies, there was no influence found on the profile distribution of total elements content. Only two horizons showed the total Pb content accumulation: biogenic (Ap-A) and carbonate (BC-C) horizon. In contrast, the only biogenic accumulation for Zn was determined. Copper characterizes by even distribution over the soil profile. The use of resource-saving agricultural technologies increases exchangeable fraction of Zn, Pb and Cu in soil almost by 1.5-2.0 times in the Ap horizon compared to moldboard ploughing. Despite the increase in the exchangeable fraction of Zn and Cu, this amount of micronutrients is not enough for adequate plant nutrition. The use of various agricultural technologies at Haplic Chernozem led to changes in the distribution of studied elements' exchangeable fraction over the soil profile. The study results suggested a need to increase the amount of Cu and Zn fertilizers applied to the soil with resource-saving cultivation technologies.

Genotoxic and morpho-physiological responses of ZnO macro- and nano-forms in plants.

In the current study, two plants, viz., Pisum sativum L. and Hordeum vulgare L., were exposed to nano- and macro-dispersed ZnO at 1, 10, and 30 times of maximal permissible concentration (MPC). The main objective of the study is to depict and compare the genotoxicity in terms of chromosomal anomalies, cytotoxicity (i.e., mitotic index), and phytotoxicity (viz., germination, morphometry, maximal quantum yield, and chlorophyll fluorescence imaging) of macro- and nano-forms of ZnO along with their accumulation and translocation. In the case of genotoxic and cytotoxic responses, the maximal effect was observed at 30 MPC, regardless of the macro- or nano-forms of ZnO. The phytotoxic observations revealed that the treatment with macro- and nano-forms of ZnO significantly affected the germination rate, germination energy, and length of roots and shoots of H. vulgare in a dose-dependent manner. The factor toxicity index of treated soil demonstrated that toxicity soared as concentrations increased and that at 30 MPC, toxicity was average and high in macro- and nano-dispersed ZnO, respectively. Furthermore, the photosynthetic parameters were observed to be negatively affected in both treatments, but the maximal effect was observed in the case of nano-dispersed form. It was noted that the mobility of nano-dispersed ZnO in the soil was higher than macro-dispersed. The increased mobility of nano-dispersed ZnO might have boosted their accumulation and translocation that subsequently led to the oxidative stress due to the accelerated production of reactive oxygen species, thus strengthen toxicity implications in plants.

Spatial distribution of heavy metals in soils of the flood plain of the Seversky Donets River (Russia) based on geostatistical methods.

Soil contamination by heavy metals (HM) is a worldwide problem for human health. To reduce risk to human health from exposure to toxic chemicals associated with soil contamination, it is necessary to monitor and assess HM concentrations in the soil for places where the concentration exceeds the acceptable levels. Spatial patterning is a necessary tool for assessment of the exposure risk of HM contamination. Soil sampling (n = 65) was carried out in technogenically polluted soils located at Rostov oblast to study the content and spatial distribution of four HM (Cu, Zn, Pb, and Cr) in the surface layer (0-20 cm) of the impact zone of former Lake Atamanskoe (floodplain of the Seversky Donets River valley, Rostov region) with an area of 3.91 km2. Extremely high values of HM concentrations were found with the maximum values of 702 mg/kg, 72,886 mg/kg, 2300 mg/kg, 259 mg/kg for Cu, Zn, Pb, and Cr, respectively. Inverse distance-weighted (IDW) interpolation was used to prepare 3D monoelement images of HM. Lognormal kriging and indicator kriging techniques were applied to create elemental spatial distribution maps and HM probability maps. The results showed that the total content of Cu, Zn, Pb, and Cr was moderately spatially dependent (nugget-to-sill ratio ranged from 31 to 38%), whereas the contamination index Zc formed strong spatial dependence patterns (nugget-to-sill ratio ranged from 0 to 21.4%). The obtained results of this study could serve as a guide to the authorities in identifying those areas which need remediation. Moreover, this study provides a tool for assessing the hygienic situation in the vicinity of Kamensk-Shakhtinsky (Rostov region) for decision making that can help to minimize the environmental risk of technogenic soil contamination of HM.

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

In the present study, the biochar derived from sunflower husks was used as a mediator in the heterogeneous Fenton process. The physical and chemical characteristics were studied in terms of specific surface area, elemental contents, surface morphology, surface functional groups, thermal stability, and X-ray crystallography. The main aim was to evaluate the effectiveness of biochar in a heterogeneous Fenton process catalyzed by hematite toward the degradation of benzo[a]pyrene (BaP) in Haplic Chernozem. The Fenton-like reaction was performed at a pH of 7.8 without pH adjustment in chernozem soil. The effects of operating parameters, such as hematite dosage and H2O2 concentrations, were investigated with respect to the removal efficiency of BaP. The overall degradation of 65% was observed at the optimized conditions where 2 mg g-1 hematite and 1.25 M H2O2 corresponded to the H2O2 to Fe ratio of 22:1. Moreover, the biochar amendment showed an increment in the removal efficiency and promotion in the growth of spring barley (Hordeum sativum distichum). The BaP removal was reached 75 and 95% after 2.5 and 5% w/w addition of biochar, respectively. The results suggested that the Fenton-like reaction's effectiveness would be greatly enhanced by the ability of biochar for activation of H2O2 and ejection of the electron to reduce Fe(III) to Fe(II). Finally, the presence of biochar could enhance the soil physicochemical properties, as evidenced by the better growth of Hordeum sativum distichum compared to the soil without biochar. These promising results open up new opportunities toward the application of a modified Fenton reaction with biochar for remediating BaP-polluted soils.

Influence of carbon-containing and mineral sorbents on the toxicity of soil contaminated with benzo[a]pyrene during phytotesting.

Benzo[a]pyrene (BaP) is a member of polycyclic aromatic hydrocarbons known for high persistency and toxicity. Technologies of BaP sorption through solid matrixes have received relatively more attention. The present study was devoted to the phytotesting investigations of two different groups of sorbents, such as carbonaceous, including biochar and granulated activated carbon (GAC), and mineral, including tripoli and diatomite. Evaluation of the BaP removing efficiency was carried out using the phytotesting method with spring barley in Haplic Chernozem contaminated with different levels of contamination (200 and 400 µg kg-1 BaP). The sorbents' efficiency for BaP remediation was estimated in the sorbents doses from 0.5 to 2.5% per kg of soil. It was shown that biochar and GAC decreased the soil toxicity class to a greater extent than mineral sorbents ones. The effect intensified with an increase in applying sorbents doses. The optimal dose of carbonaceous sorbents into the soil contaminated with 200 µg kg-1 was 1%, decreasing the BaP content up 57-59% in the soil. Simultaneously, the optimal dose of the mineral sorbents was found to be 1.5%, which decreased the BaP content in the soil up 41-48%. Increasing the BaP contamination level up to 400 µg kg-1 showed the necessity of a sorbent dose increasing. In these conditions, among all applied sorbents, only 2% GAC could reduce the soil toxicity class to the normal level up to 0.91-1.10. It was shown that BaP tended to migrate from the soil to the roots and further into the vegetative part of barley.

Sorption of benzo[a]pyrene by Chernozem and carbonaceous sorbents: comparison of kinetics and interaction mechanisms.

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon, highly persistent and toxic and a widespread environmental pollutant. Although various technologies have been developed to remove BaP from the environment, its sorption through solid matrixes has received increasing attention due to cost-effectiveness. The present research compares the adsorption capacity of Haplic Chernozem, granular activated carbon and biochar in relation to BaP from water solution. Laboratory experiments with different initial BaP concentrations in the liquid phase and different ratios of the solid and liquid phases show that Freundlich model describes well the adsorption isotherms of BaP by the soil and both sorbents. Moreover, the BaP isotherm sorption by the Haplic Chernozem is better illustrated by the Freundlich model than the Langmuir equation. The results reveal that the sorption capacity of the carbonaceous adsorbents at a ratio 1:20 (solid to liquid phases) is orders of magnitude higher (13 368 ng mL-1 of activated carbon and 3 578 ng mL-1 of biochar) compared to the soil (57.8 ng mL-1). At the ratio of 0.5:20, the adsorption capacity of the carbonaceous sorbents was 17-45 times higher than that of the soil. This is due to the higher pore volume and specific surface area of the carbonaceous sorbents than soil particles, assessed through scanning electron microscopy. The sorption kinetic of BaP by Chernozem was compared with the adsorption kinetics by the carbonaceous sorbents. Results indicate that the adsorption dynamic involves two steps. The first one is associated with a fast BaP adsorption on the large available surface and inside macro- and meso-pores of the sorbent particles of the granular activated carbon and biochar. Then, the adsorption is followed by a slower process of BaP penetration into the microporous space and/or redistribution into a hydrophobic fraction. The effectiveness of the sorption process depends on both the sorbent properties and the solvent competition. Overall, the granular activated carbon and biochar are highly effective adsorbents for BaP, whereas the Haplic Chernozem has a rather limited capacity to remove BaP from contaminated solutions.

Effect of nanomaterials on remediation of polycyclic aromatic hydrocarbons-contaminated soils: A review.

The remediation of toxic polycyclic aromatic hydrocarbons (PAHs) in the soil is always an important topic since exposure to contaminated soil with carcinogenic, mutagenic, and teratogenic potential can result in serious health effects. With respect to the remediation of PAHs contaminated soil, nanomaterials (NMs) have recently received a great deal of attention due to the special characteristics arising from their nanoscale sizes. However, the usefulness and potency of these NMs depend on their adaption to specific site conditions and soil properties. Since there is no comprehensive review of the applications of NMs, it is of great importance to analyze, discuss, and interpret the latest progress in the application of NMs for the remediation of contaminated soils containing PAHs. This overview essentially captures the novel advances made in nano zero valent-iron (nZVI), metal oxides, carbon-based NMs, and polymer-based materials. Each characteristic of NMs that contributes to the enhancement of the process is highlighted. Moreover, operational conditions in which the best-obtained results are achieved qualitatively summarize. This review is also given special attention to the type of soil and pollutant, which are major influential factors to affect the performance of the process. Furthermore, the potential implication of NMs and PAHs on soil properties is reviewed in terms of the changes in migration behavior of pollutants, plant phytotoxicity, and soil microbial community composition. Discussion on future perspectives is presented on the use and prospects for the application of NMs in contaminated soils.

Subcritical water extraction of organic acids from chicken manure.

BACKGROUND: Chicken manure waste has a wide range of organic substances and mineral elements. This enriched source has stimulated great scientific interest in finding cleaner and more environmentally benign nutrient recovery options. This study aimed to determine an effective and eco-friendly method (i.e. subcritical water extraction) for processing fresh poultry manure. RESULTS: The high content of total organic carbon, including humic acids carbon and fulvic acids carbon, in extract was found to release under subcritical conditions. The organic compounds obtained by extraction with subcritical water correspond to humic acid in composition because of the presence in the sample of all the functional groups: polymer bonded by molecular hydrogen bond (3400 cm-1 ), the presence of CH2 and CH3 groups (2870 cm-1 ), the presence of carboxyl groups (1720 cm-1 ) and quinones (1640-1680 cm-1 ). The solid phase left over was characterized by a high content of organic carbon, phosphorus, potassium, and microelements. The maximum extraction of humic acid and fulvic acid carbon was found between 210 and 250 °C at a pressure of 50-60 atm, and the content was a maximum of 3647.2 × 10-6 g kg-1 at an extraction temperature of 250 °C. CONCLUSION: Given the high content of humic acid found in the extracted medium, the proposed subcritical extraction opens up new opportunities for nutrients recovery in the poultry industry. © 2020 Society of Chemical Industry.

Nitrogen state of Haplic Chernozem of the European part of Southern Russia in the implementation of resource-saving technologies.

BACKGROUND: The prolonged use of traditional moldboard ploughing often results in soil degradation and, ultimately, has an impact on national food security. Therefore, the implementation of resource-saving technologies (minimal and No-till) is a promising approach in the development of agriculture, especially in drought regions. The present study reports the results of long-term research on the effect of various tillage methods (moldboard ploughing, minimal tillage and No-till technique) on the nitrogen content of Haplic Chernozem of the European part of Southern Russia. The revealed regularities can be used as a theoretical basis for the effective use of resource-saving technologies, including No-till, in the zone of insufficient moisture. RESULTS: Long-term (59 years) cultivation of winter wheat using traditional moldboard ploughing has decreased the soil organic material (SOM) by 35% and total nitrogen by 32% in the soil. Minimization of tillage, in contrast, recovers the nitrogen potential of the soil in winter wheat agrocenoses. There is a statistically confirmed dependence of the content of SOM and total nitrogen on the tillage method of the upper soil horizon, with no significant effect of the tillage methods on intensity ammonification and nitrification. However, the content of nitrate-nitrogen during resource-saving tillage methods (22.8-24.4 mg kg-1 ) was higher than that after ploughing (20.3 mg kg-1 ) during all the years of the study, indicating the higher content of easily mineralizable nitrogen-containing compounds in the soil after minimal tillage. CONCLUSION: The use of resource-saving tillage technologies under conditions of insufficient moisture stabilizes the nitrogen content in soil and can improve nitrogen nutrition of plants. © 2020 Society of Chemical Industry.

Impact of humic acid on degradation of benzo(a)pyrene polluted Haplic Chernozem triggered by modified Fenton-like process.

In this study, the applicability of a modified Fenton reaction for remediation of polycyclic aromatic hydrocarbons (PAHs) was demonstrated in chernozem soil. The main aim was to investigate the impact of variation of humic acid (HA) on the modified Fenton capabilities to degrade of benzo(a)pyrene (BaP). Experimental was designed with two independent variables, including hydrogen peroxide (H2O2) and hematite (α-Fe2O3), to determine the most effective BaP treatment conditions with exploring natural and an extra added amount of HA. For modified Fenton reaction at Haplic Chernozem, the best BaP degradation conditions resulted in an overall degradation of 68% with the following conditions: 0.95 M H2O2; 17.54 mg/g hematite; pH 7.8 without adjustment; 24 h; unsaturated (soil: water ratio 1:0.5). In the soil supplemented with 1% HA, Fenton-like reaction was found to perform better and resulted in 76% BaP degradation with less amount of hematite dosage (16.71 mg). The fact that HA, a significant class of naturally occurring compounds in soil, supports the Fenton reaction has strong relevance in the field of enhancing PAHs degradation field to obtain a more economical route.

Heavy metals drive microbial community assembly process in farmland with long-term biosolids application.

Biosolids are considered an alternative to chemical fertilizers due to their rich nutrients. However, long-term biosolids application can lead to heavy metals accumulation, which severely affects soil microbial community compositions. The factors influencing soil microbial community assembly were explored under a 16-year long-term experiment with biosolids applications. Our results indicated that biosolids application significantly increased fungal richness while not for bacterial and arbuscular mycorrhizal (AM) fungal richness. Besides, biosolids application significantly affected soil bacterial, fungal compositions and AM fungal community. Soil microorganisms were clustered into different modules with bacterial and AM fungal communities were affected by both organic matter and heavy metals, while fungal communities were affected by heavy metals (Cr, Ni, and As). The soil bacterial community assembly was dominated by stochastic processes while the fungal and AM fungal community assemblies were mainly driven by deterministic processes. Random forest analysis showed that heavy metals were identified as major drivers (Hg, Cu, Cd, and Zn for bacteria, Pb and Cr for fungi, and As and Ni for AM fungi) of the community assembly process. Overall, our study highlights the significant role of heavy metals in shaping microbial community dynamics and gives a guide for controlling biosolids application.

From feedstock to digestion: Unraveling the impact of humic acid composition on anaerobic digestion.

In the anaerobic digestion (AD) process, the effects of humic acid (HA) derived from different feedstocks on AD are influenced by the variations in their structural composition and oxygen-containing functional groups. Thus, clarifying the structural differences of HA obtained from different feedstocks is crucial for understanding their impact on AD. In this study, the structure of five humic acids (HAs) derived from liquid digestate, food waste, silage corn straw, lignite and commercial HA, and their effects on AD were investigated. The study found that HA from food waste had more carboxyl groups, while straw-derived HA had more phenolic hydroxyl groups. Both types of HA had higher aromaticity and humification degree and showed significant inhibition effect on AD. HA from food waste had an average methanogenic inhibition rate of 43.5 % with 1 g/L HA added. In addition, commercial HA and HA derived from lignite had similar functional group types and aromaticity, with an average methanogenic inhibition rate of about 20 %. The study revealed that HAs with more carboxyl groups exhibited greater effectiveness in inhibiting AD, thereby confirming the influence of HA structures derived from different feedstocks on AD. In conclusion, this study provides valuable insights into the mechanism of HA effect on AD and offers guidance for future research focused on enhancing AD efficiency.

Composting pig manure with nano-zero-valent iron amendment: Insights into the carbon cycle and balance.

The effectiveness of nano-zero-valent-iron (NZVI) addition during composting of pig manure (PM) was investigated. Different dosages of NZVI were mixed with PM substrate during a 50 days composting process. The results revealed that the higher share of NZVI addition, the higher OM degradation rate is. On contrary, it was observed that the higher share of NZVI addition, the lower the fulvic acid and the humin degradation rate is. Meanwhile, NZVI amendment increased the CO2 and CH4 emissions by 29-47 % and 53-57 %, respectively. The in-depth analysis showed that NZVI addition increased the activity of Sphaerobacter and Luteimonas, which eventually led to the degradation of hard-to-degrade OM faster. Additionally, NZVI was found to increase the filtration of microorganisms, reducing the toxicity and hygiene of compost products. No significant improvement in humic substance enhancement was observed during composting with NZVI addition but improved OM degradation.

Nanomaterials in biochar: Review of their effectiveness in remediating heavy metal-contaminated soils.

Biochar can be used for soil remediation in environmentally beneficial manner, especially when combined with nanomaterials. After a decade of research, still, no comprehensive review was conducted on the effectiveness of biochar-based nanocomposites in controlling heavy metal immobilization at soil interfaces. In this paper, the recent progress in immobilizing heavy metals using biochar-based nanocomposite materials were reviewed and compared their efficacy against that of biochar alone. In details, an overview of results on the immobilization of Pb, Cd, Cu, Zn, Cr, and As was presented by different nanocomposites made by various biochars derived from kenaf bar, green tea, residual bark, cornstalk, wheat straw, sawdust, palm fiber, and bagasse. Biochar nanocomposite was found to be most effective when combined with metallic nanoparticles (Fe3O4 and FeS) and carbonaceous nanomaterials (graphene oxide and chitosan). This study also devoted special consideration to different remediation mechanisms by which the nanomaterials affect the effectiveness of the immobilization process. The effects of nanocomposites on soil characteristics related to pollution migration, phytotoxicity, and soil microbial composition were assessed. A future perspective on nanocomposites' use in contaminated soils was presented.

Fabrication of biochar derived from different types of feedstocks as an efficient adsorbent for soil heavy metal removal.

For effective soil remediation, it is vital to apply environmentally friendly and cost-effective technologies following the notion of green sustainable development. In the context of recycling waste and preserving nutrients in the soil, biochar production and utilization have become widespread. There is an urgent need to develop high-efficiency biochar-based sorbents for pollution removal from soil. This research examined the efficacy of soil remediation using biochar made from three distinct sources: wood, and agricultural residues (sunflower and rice husks). The generated biochars were characterized by SEM/SCEM, XRF, XRD, FTIR, BET Specific Surface Area, and elemental compositions. The presence of hydroxyl and phenolic functional groups and esters in wood, sunflower and rice husk biochar were noted. The total volume of pores was in the following descending order: rice husk > wood > sunflower husk. However, wood biochar had more thermally stable, heterogeneous, irregular-shaped pores than other samples. Adsorption of soil-heavy metals into biochars differed depending on the type of adsorbent, according to data derived from distribution coefficients, sorption degree, Freundlich, and Langmuir adsorption models. The input of biochars to Calcaric Fluvic Arenosol increased its adsorption ability under contamination by Cu(II), Zn(II), and Pb(II) in the following order: wood > rice husk > sunflower husk. The addition of sunflower husk, wood, and rice husk biochar to the soil led to an increase in the removal efficiency of metals in all cases (more than 77%). The increase in the percentage adsorption of Cu and Pb was 9-19%, of Zn was 11-21%. The present results indicated that all biochars functioned well as an absorbent for removing heavy metals from soils. The tailor-made surface chemistry properties and the high sorption efficiency of the biochar from sunflower and rice husks could potentially be used for soil remediation.

Exploring carbon conversion and balance with magnetite-amended during pig manure composting.

This study was designed to explore the magnetite in maturation and humification during pig manure (PM) and wolfberry branch fillings (BF) composting. Different proportions of magnetite (T1, 0%; T2, 2.5%; T3, 5%; T4, 7.5%;) were blended with PM for 50 days of composting. The findings indicated magnetite amendment has no influence on the maturity, and the 5% ratio significantly promoted humic acid (HA) formation and fulvic acid (FA) decomposition compared to other treatments. Compared to T1, magnetite addition significantly increased CO2 and CH4 emissions by 106.39%-191.69% and 6.88-13.72 times. The further analysis suggested that magnetite improved Ruminofilibacter activity were significantly positively associated with HA, and C emissions. The further PICRUSt 2 analysis showed membrane transport may enhance environmental information processing by magnetite. Overall, these results demonstrated higher organic matter (OM) degradation and HA formation with an additional increase in microbial activity highlighted advantages of using magnetite during PM composting.

Decrypting the synergistic action of the Fenton process and biochar addition for sustainable remediation of real technogenic soil from PAHs and heavy metals.

The objective of this study was to demonstrate the feasibility and the relevance of combining biochar with the Fenton process for the simultaneous improvement of polycyclic aromatic hydrocarbons (PAHs) degradation and immobilization of heavy metals (HMs) in real soil remediation processes at circumneutral pH. The evaluation of PAHs degradation results was performed through multivariate statistical tools, including principal component analysis (PCA) and partial least squares (PLS). PCA showed that the level of biochar amendment decisively affected the degree of degradation of total PAHs, highlighting the role of biochar in catalyzing the Fenton reaction. Moreover, the PLS model was used to interpret the important features of each PAH's physico-chemical properties and its correlation to degradation efficiency. The electron affinity of PAHs correlated positively with the degradation efficiency only if the level of biochar amendment sat at 5%, explained by the ability of biochar to transfer the electrons to PAHs, improving the Fenton-like degradation. Moreover, the addition of biochar reduced the mobilization of HMs by their fixation on their surface, reducing the Fenton-induced metal leaching from the destruction of metal-organic complexes. In overall, these results on the high immobilization rate of HMs accompanied with additional moderate PAHs degradation highlighted the advantages of using a biochar-assisted Fenton-like reaction for sustainable remediation of technogenic soil.

Visible-Light-Driven Reduced Graphite Oxide as a Metal-Free Catalyst for Degradation of Colored Wastewater.

Reduced graphite oxide (rGO)-based materials have demonstrated promising potential for advanced oxidation processes. Along with its distinctive 2D characteristics, rGO offers the prospect of catalytic degradation of various kinds of organic pollutants from aqueous environments. The practical application of rGO as a metal-free catalyst material to promote the Fenton reaction depends on the degree of rGO reduction. In this regard, the rGO was prepared according to oxidation by modified Hummers' method and two-step reduction via hydrothermal and calcination in the N2 atmosphere. The as-prepared rGO was characterized in terms of X-ray diffraction, Fourier-transform infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, UV-vis absorption spectroscopy, and transmission electron microscopy. The effectiveness of as-prepared rGO as a photocatalyst and the metal-free catalyst to decolorize different textile dyes, including basic red 46, basic red 18, and methylene blue, was investigated in visible/rGO and visible/rGO/H2O2 systems. The impact of operational factors such as catalyst dose, pH, and initial dye concentration was examined. The dye degradation process was investigated by the pseudo-first-order kinetic model. In addition, the recyclability of rGO in the visible/rGO/H2O2 system was examined.