High-effectively degrade the di-(2-ethylhexyl) phthalate via biochemical system: Resistant bacterial flora and persulfate oxidation activated by BC@Fe3O4

Structure-dependent degradation of phthalate esters with persulfate oxidation activated by thermal in soil

Phthalate esters (PAEs) have become one of the most concerned emerging organic pollutants in the world, due to the toxicity to human health, and hard to remove it efficiently. In this study, the degradation performance of DBP and DEHP in the soil by water bath heating activated sodium persulfate (PS) method under different factors were studied, in which the degradation rate of DBP and DEHP were improved with the increasing of temperature, PS concentration and water/soil ratio, and higher diffusion efficiency treatments methods, due to the improved mass transfer from organic phase to aqueous media. However, the degradation rate of DEHP was much lower than that of DBP, because DEHP in the soil was more difficult to contact with SO4•- for reaction on soil surface, and the degradation rate of PAEs in soil was significantly lower than that in water. Redundancy analysis of degradation rate of DBP and DEHP in water demonstrated that the key factors that determine the degradation rate is time for DBP, and cosolvent dosage for DEHP, indicating that the solubility and diffusion rate of PAEs from soil to aqueous are predominance function. This study provides comprehensive scenes in PAEs degradation with persulfate oxidation activated by thermal in soil, reveal the difference of degradation between DBP and DEHP is structure-dependent. So that we provide fundamental understanding and theoretical operation for subsequent filed treatment of various structural emerging pollutants PAEs contaminated soil with thermal activated persulfate.

Mechanisms of biochar assisted di-2-ethylhexyl phthalate (DEHP) biodegradation in tomato rhizosphere by metabolic and metagenomic analysis

The intensive accumulation of di-2-ethylhexyl phthalate (DEHP) in agricultural soils has resulted in severe environmental pollution that endangers ecosystem and human health. Biochar is an eco-friendly material that can help in accelerating organic pollutant degradation; nevertheless, its roles in enhancing DEHP removal in rhizosphere remain unclear. This work investigated the impacts of biochar dosage (0%-2.0%) on DEHP degradation performance in tomato rhizosphere by comprehensively exploring the change in DEHP metabolites, bacterial communities and DEHP-degrading genes. Our results showed a significant increase of rhizosphere pH, organic matter and humus by biochar amendment, which achieved a satisfactorily higher DEHP removal efficiency, maximally 77.53% in treatments with 1.0% of biochar. Biochar addition also remarkably changed rhizosphere bacterial communities by enriching some potential DEHP degraders of Nocardioides, Sphingomonas, Bradyrhizobium and Rhodanobacter. The abundance of genes encoding key enzymes (hydrolase, esterase and cytochrome P450) and DEHP-degrading genes (pht3, pht4, pht5, benC-xylZ and benD-xylL) were increased after biochar amendment, leading to the change in DEHP degradation metabolism, primarily from benzoic acid pathway to protocatechuic acid pathway. Our findings evidenced that biochar amendment could accelerate DEHP degradation by altering rhizosphere soil physicochemical variables, bacterial community composition and metabolic genes, providing clues for the mechanisms of biochar-assisted DEHP degradation in organic contaminated farmland soils.

Effect of aging on the release of di-(2-ethylhexyl) phthalate from biodegradable and petroleum-based microplastics into soil

Due to microplastics (MPs) being widely distributed in soil, the use of advanced oxidation to remediate organic-contaminated soils may accelerate the aging of MPs in soil and impact the release of di-(2-ethylhexyl) phthalate (DEHP), a potential carcinogen used as a plasticizer in plastics, from MPs. In this study, persulfate oxidation (PO) and temperature treatment (TT) were used to treat biodegradable and petroleum-based MPs, including polylactic acid (PLA), polyvinyl chloride (PVC), and polystyrene (PS). The methods used for evaluating the characteristics changes of MP were X-ray diffraction (XRD) analysis and water contact angle measurement. The effects of aging on DEHP release from MPs were investigated via soil incubation. The results showed PO and TT led to increased surface roughness, oxygen-containing functional group content, and hydrophilicity of the MPs with prolonged aging, consequently accelerating the release of DEHP from the MPs. Interestingly, PLA aged faster than PVC and PS under similar conditions. After 30 days of PO treatment, DEHP release from PLA into the soil increased 0.789-fold, exceeding the increase from PVC (0.454-fold) and PS (0.287-fold). This suggests that aged PLA poses a higher ecological risk than aged PVC or PS. Furthermore, PO treatment resulted in the oxidation and degradation of DEHP on the MP surface. After 30 days of PO treatment, the DEHP content in PLA, PVC, and PS decreased by 19.1%, 25.8%, and 23.5%, respectively. Specifying the types of MPs studied and the environmental conditions would provide a more precise context for the results. These findings provide novel insights into the fate of biodegradable and petroleum-based MPs and the potential ecotoxicity arising from advanced oxidation remediation in contaminated soils.

Application of compost assisted by Fe3O4 nanoparticles in di (2-ethylhexyl) phthalate-contaminated soil remediation: Biostimulation strategy, Soil responses, and RSM/CCD Optimization

Globally, contamination of agricultural soils by phthalate esters (PAEs) caused by direct consumption of plastic mulch films has been confirmed. The most widely used plasticizer is di (2-ethylhexyl) phthalate (DEHP), which is a more recalcitrant endocrine-disrupting chemical (EDC). Because of its low solubility and hydrophobicity, it remains in the soil longer, causes bioaccumulation in agricultural products, and has negative repercussions for food safety. In this study, the performance of kitchen organic waste compost assisted by Fe3O4 nanoparticles in DEHP removal efficiency (%) and soil C:N ratio (two responses) was optimized using Response Surface Methodology (RSM) based on Central Composite Design (CCD) in Design-Expert software (11.0.3.0). Under optimum conditions, a DEHP concentration of 10 mg·kg-1 (dw soil), a retention time of 35 days, an NPs dose of 0.99 g·kg-1 (media), a removal efficiency of 91.6 %, and a soil C:N ratio of 10.5 with a desirability of 0.963 were determined. A quadratic model (P-value <0.0001, adjusted R2 = 0.974 (Y1), 0.943 (Y2)) was used to predict the variables and their interactions. The agricultural soil responses in the treatments amended by compost and Fe3O4 NPs (SCN) showed a significant increase in SOM, TC, TN, AP, K, and Fe nutrients when compared to the control (P < 0.05). After 35 days, in the SC1N3 treatment (DEHP concentration = 10 mg·kg-1, NPs dose =1.2 g·kg-1), with higher DEHP removal efficiency (89.57 %), the C:N:P ratio was equal to 100: 9.75:0.69, and the total microbial colony count was 3.6 × 109 CFU/ml at pH 7.45. The study found that compost nutrients and Fe-based nanoparticle micronutrients can enhance DEHP degradation by stimulating the soil's native microflora. As a result, the synergistic potential of compost and Fe3O4 nanoparticles can be considered a promising, cost-effective, and agri-environmentally friendly approach in the "assisted bioremediation" strategy of DEHP-contaminated soils.

Reutilization of scrap tyre for the enhanced removal of phthalate esters from water: immobilization performance, interaction mechanisms, and application

Waste scrap tyre as microbial immobilization matrix enhanced degradation of phthalate esters (PAEs), di (2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and diethyl phthalate (DEP). The hybrid (physical adsorption and microbial immobilization) degradation process performance of scrap tyres was examined for the PAEs degradation. The scrap tyre was shown with competitive adsorption capacity toward PAEs, influenced by pH, temperature, dosage of adsorbent (scrap tyre), and concentration of PAE. The primary adsorption mechanism for tyres toward PAEs was considered hydrophobic. The immobilization of previously isolated Bacillus sp. MY156 on tyre surface significantly enhanced PAEs degradation as well as bacterial growth. The enzymatic activity results implied immobilization promoted dehydrogenase activity and decreased esterase activity. The cell surface response during PAEs degradation, in terms of morphological observation, FTIR and XRD analyses, and extracellular polymeric substance (EPS) release, was further assessed to better understand the interactions between microorganisms and tyre surface. Waste scrap tyres could be a promising potential candidate to be reused for sustainable environmental management, including contaminants removal.

Substrate-enzyme interactions and catalytic mechanism in a novel family VI esterase with dibutyl phthalate-hydrolyzing activity

Microbial degradation has been confirmed as effective and environmentally friendly approach to remediate phthalates from the environment, and hydrolase is an effective element for contaminant degradation. In the present study, a novel dibutyl phthalate (DBP)-hydrolyzing carboxylesterase (named PS06828) from Pseudomonas sp. PS1 was heterogeneously expressed in E. coli, which was identified as a new member of the lipolytic family VI. Purified PS06828 could efficiently degrade DBP with a wide range of temperature (25-37 °C) and pH (6.5-9.0). Multi-spectroscopy methods combined with molecular docking were employed to study the interaction of PS06828 with DBP. Fluorescence and UV-visible absorption spectra revealed the simultaneous presence of static and dynamic component in the fluorescence quenching of PS06828 by DBP. Synchronous fluorescence and circular dichroism spectra showed inconspicuous alteration in micro-environmental polarity around amino acid residues but obvious increasing of α-helix and reducing of β-sheet and random coil in protein conformation. Based on the information on exact binding sites of DBP on PS06828 provided by molecular docking, the catalytic mechanism mediated by key residues (Ser113, Asp166, and His197) was proposed and subsequently confirmed by site-directed mutagenesis. The results can strengthen our mechanistic understanding of family VI esterase involved in hydrolysis of phthalic acid esters, and provide a solid foundation for further enzymatic modification.

Degradation of oxytetracycline by iron-manganese modified industrial lignin-based biochar activated peroxy-disulfate: Pathway and mechanistic analysis

In this study, high-performance Fe-Mn-modified industrial lignin-based biochar (FMBC) was successfully prepared to facilitate the efficient degradation of oxytetracycline by its driven sulfate radical-based advanced oxidation process with 90% degradation within 30 min. The results showed that oxygenated functional groups (e. g. hydroxyl, carbonyl, etc.) in industrial lignin-based biochar, the synergistic effect of transition metals Fe and Mn, and defective structures were the active sites for activation of peroxy-disulfate. SO₄^·- produced during the degradation process assumed a key function. Significantly, 38 intermediates were innovatively proposed for the first time in the system, and oxytetracycline was degraded in 7 ways, including deamidation, demethylation, hydroxylation, secondary alcohol oxidation, ring opening, dehydration, and carbonylation. A new perspective on the application of industrial lignin in the advanced oxidative degradation of organic pollutants was provided by this study.

Biodegradation of high di-(2-Ethylhexyl) phthalate (DEHP) concentration by food waste composting and its toxicity assessment using seed germination test

Di-(2-ethylhexyl) phthalate (DEHP), a plasticizer derived from phthalate ester, is used as an additive in industrial products such as plastics, paints, and medical devices. However, DEHP is known as an endocrine-disrupting chemical, causing cancers and adverse effects on human health. This study evaluated DEHP biodegradation efficiency via food waste composting during 35 days of incubation. At high DEHP concentrations (2167 mg kg^-1) in food waste compost mixture, the DEHP biodegradation efficiency was 99% after 35 days. The highest degradation efficiency was recorded at the thermophilic phase (day 3 - day 11) with the biodegradation rate reached 187 mg kg^-1 day^-1. DEHP was metabolized to dibutyl phthalate (DBP) and dimethyl phthalate (DMP) and would be oxidized to benzyl alcohol (BA) and mineralized into CO₂ and water via various metabolisms. Finally, the compost's quality with residual DEHP was evaluated using Brassica chinensis L. seeds via 96 h of germination tests. The compost (at day 35) with a trace amount of DEHP as the end product showed no significant effect on the germination rate of Brassica chinensis L. seeds (88%) compared to that without DEHP (94%), indicating that the compost can be reused as fertilizer in agricultural applications. These results provide an improved understanding of the DEHP biodegradation via food waste composting without bioaugmentation and hence facilitating its green remediation and conversion into value-added products. Nevertheless, further studies are needed on DEHP biodegradation in large-scale food waste composting or industrial applications.

Magnetically modified in-situ N-doped Enteromorpha prolifera derived biochar for peroxydisulfate activation: Electron transfer induced singlet oxygen non-radical pathway

Herein, in-situ N-doped Enteromorpha prolifera derived magnetic biochar (MBC) was prepared by loading Fe₃O₄. It can effectively activate peroxodisulfate (PDS) to degrade tetracycline (TC) and easy recycling. The removal rate of TC reached 87.2%, and its possible degradation pathway was revealed through a liquid chromatography-mass spectrometer. This work first proposes the mechanism of in-situ N-doping and Fe synergistic effect on PDS activation. Unlike the well-reported role of N doping in activating PDS, except for the edge pyridine N plays a significant role in the activation of PDS. After the load of Fe, the synergistic effect of Fe and graphite N induces a non-radical path dominated by singlet oxygen (¹O₂) due to the excellent electron transfer function. Through chemical quenching experiment, electron spin detection, and electrochemical analysis, the mechanism of PDS activation by MBC was thoroughly investigate. This research will deepen the understanding of the mechanism of transition metals and carbon materials in synergistically driving PDS activation, and guide biochar-mediated PDS activation in environmental remediation.

Effects of Fe-Mn impregnated biochar on enzymatic activity and bacterial community in phthalate-polluted brown soil planted with wheat

A pot experiment was carried out on brown soil polluted by dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) to investigate the effects of biochar (BC) derived from corn straw and Fe-Mn oxide modified biochar composites (FMBC) on the bioavailability of DBP and DEHP, as well as ecosystem responses in rhizosphere soil after wheat ripening. The results indicate that the application of BC and FMBC significantly increases soil organic matter, pH, available nitrogen (AN), Olsen phosphorus, and available potassium (AK); reduces the bioavailability of DBP and DEHP; enhances the activities of dehydrogenase, urease, protease, β-glucosidase, and polyphenol oxidase; and decreases acid phosphatase activity. No changes in richness and diversity, which were measured by Illumina MiSeq sequencing, were observed following BC and FMBC application. The bacterial community structure and composition varied with DBP/DEHP concentrations and BC/FMBC additions in a nonsystematic way and no significant trends were observed. In addition, FMBC exhibited better performance in increasing soil properties and decreasing the bioavailability of DBP and DEHP compared with BC. Hence, the FMBC amendment may be a promising way of developing sustainable agricultural environmental management.

A review on efficient removal of phthalic acid esters via biochars and transition metals-activated persulfate systems

As emerging contaminants, PAEs (Phthalic Acid Esters or Phthalate Esters) have been extensively utilized in industrial production to soften the rigid plastics (plasticizers), and their related products are widely distributed in our daily life. The PAEs can readily transfer from the products to the surrounding environment due to not being chemically bound to the products. In this study, we analyzed the PAEs' properties, usage, and consumption in the world, as well as toxicity to human beings. As endocrine-disrupting chemicals (EDCs), PAEs can disturb the normal hormones reactions, resulting in developmental and reproductive problems. Thus, we have to concern the removal strategies of PAEs. We summarized two novel approaches, including biochars and persulfate (PS) oxidation for effectively removing PAEs in the literature. Their characteristics, removal mechanisms, and the main impact factors on the removal of PAEs were highlighted. Moreover, transition metal-activated PS showed good performance on PAEs degradation. Furthermore, the synergy of biochars and transition metals-PS can overcome the disadvantages of a single approach, and show better performance on the removal of PAEs. Finally, we put forward vital strategies to update two approaches (including the combined) for enhancing the removal of PAEs. It is expected that the researchers or scientists can get a hint on effectively remediating PAEs-contaminated sites via the biochars' sorption/transition metals-PS or the combined two from this review paper.

Recent Advances in Magnetic Nanoparticles and Nanocomposites for the Remediation of Water Resources

Water resources are of extreme importance for both human society and the environment. However, human activity has increasingly resulted in the contamination of these resources with a wide range of materials that can prevent their use. Nanomaterials provide a possible means to reduce this contamination, but their removal from water after use may be difficult. The addition of a magnetic character to nanomaterials makes their retrieval after use much easier. The following review comprises a short survey of the most recent reports in this field. It comprises five sections, an introduction into the theme, reports on single magnetic nanoparticles, magnetic nanocomposites containing two of more nanomaterials, magnetic nanocomposites containing material of a biologic origin and finally, observations about the reported research with a view to future developments. This review should provide a snapshot of developments in what is a vibrant and fast-moving area of research.