Di-n-butyl Phthalate Degradation Research Articles

Complete degradation of di-n-butyl phthalate by Glutamicibacter sp. strain 0426 with a novel pathway.

Di-n-butyl phthalate (DBP) is widely used as plasticizer that has potential carcinogenic, teratogenic, and endocrine effects. In the present study, an efficient DBP-degrading bacterial strain 0426 was isolated and identified as a Glutamicibacter sp. strain 0426. It can utilize DBP as the sole source of carbon and energy and completely degraded 300mg/L of DBP within 12h. The optimal conditions (pH 6.9 and 31.7°C) for DBP degradation were determined by response surface methodology and DBP degradation well fitted with the first-order kinetics. Bioaugmentation of contaminated soil with strain 0426 enhanced DBP (1mg/g soil) degradation, indicating the application potential of strain 0426 for environment DBP removal. Strain 0426 harbors a distinctive DBP hydrolysis mechanism with two parallel benzoate metabolic pathways, which may account for the remarkable performance of DBP degradation. Sequences alignment has shown that an alpha/beta fold hydrolase (WP_083586847.1) contained a conserved catalytic triad and pentapeptide motif (GX1SX2G), of which function is similar to phthalic acid ester (PAEs) hydrolases and lipases that can efficiently catalyze hydrolysis of water-insoluble substrates. Furthermore, phthalic acid was converted to benzoate by decarboxylation, which entered into two different pathways: one is the protocatechuic acid pathway under the role of pca cluster, and the other is the catechol pathway. This study demonstrates a novel DBP degradation pathway, which broadens our understanding of the mechanisms of PAE biodegradation.

Endophytic Phthalate-degrading Bacillus subtilis N-1-gfp colonizing in soil-crop system shifted indigenous bacterial community to remove di-n-butyl phthalate

Endophytic bacteria can degrade toxic phthalate (PAEs). Nevertheless, the colonization and function of endophytic PAE-degrader in soil-crop system and their association mechanism with indigenous bacteria in PAE removal remain unknown. Here, endophytic PAE-degrader Bacillus subtilis N-1 was marked with green fluorescent protein gene. Inoculated strain N-1-gfp could well colonize in soil and rice plant exposed to di-n-butyl phthalate (DBP) as directly confirmed by confocal laser scanning microscopy and realtime PCR. Illumina high-throughput sequencing demonstrated that inoculated N-1-gfp shifted indigenous bacterial community in rhizosphere and endosphere of rice plants with significant increasing relative abundance of its affiliating genus Bacillus than non-inoculation. Strain N-1-gfp exhibited efficient DBP degradation with 99.7% removal in culture solutions, and significantly promoted DBP removal in soil-plant system. Strain N-1-gfp colonization help plant enrich specific functional bacteria (e.g., pollutant-degrading bacteria) with significant higher relative abundances and stimulated bacterial activities (e.g., pollutant degradation) compared with non-inoculation. Furthermore, strain N-1-gfp displayed strong interaction with indigenous bacteria for accelerating DBP degradation in soil, decreasing DBP accumulation in plants and promoting plant growth. This is the first report on well colonization of endophytic DBP-degrader Bacillus subtilis in soil-plant system and its bioaugmentation with indigenous bacteria for promoting DBP removal.

Exploring Potent Fungal Isolates from Sanitary Landfill Soil for In Vitro Degradation of Dibutyl Phthalate.

Di-n-butyl phthalate (DBP) is one of the most extensively used plasticizers for providing elasticity to plastics. Being potentially harmful to humans, investigating eco-benign options for its rapid degradation is imperative. Microbe-mediated DBP mineralization is well-recorded, but studies on the pollutant's fungal catabolism remain scarce. Thus, the present investigation was undertaken to exploit the fungal strains from toxic sanitary landfill soil for the degradation of DBP. The most efficient isolate, SDBP4, identified on a molecular basis as Aspergillus flavus, was able to mineralize 99.34% dibutyl phthalate (100 mg L-1) within 15 days of incubation. It was found that the high production of esterases by the fungal strain was responsible for the degradation. The strain also exhibited the highest biomass (1615.33 mg L-1) and total soluble protein (261.73 µg mL-1) production amongst other isolates. The DBP degradation pathway scheme was elucidated with the help of GC-MS-based characterizations that revealed the formation of intermediate metabolites such as benzyl-butyl phthalate (BBP), dimethyl-phthalate (DMP), di-iso-butyl-phthalate (DIBP) and phthalic acid (PA). This is the first report of DBP mineralization assisted with A. flavus, using it as a sole carbon source. SDBP4 will be further formulated to develop an eco-benign product for the bioremediation of DBP-contaminated toxic sanitary landfill soils.

Application of Fungus Enzymes in Spent Mushroom Composts from Edible Mushroom Cultivation for Phthalate Removal.

Spent mushroom composts (SMCs) are waste products of mushroom cultivation. The handling of large amounts of SMCs has become an important environmental issue. Phthalates are plasticizers which are widely distributed in the environment and urban wastewater, and cannot be effectively removed by conventional wastewater treatment methods. In this study, SMCs are tested for their ability to remove phthalates, including benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP), and diethyl phthalate (DEP). Batch experiments reveal that BBP, DBP, and DEP can be degraded by the SMC enzyme extracts of four edible mushrooms: Pleurotus eryngii, Pleurotus djamor, Pleurotus ostreatus, and Auricularia polytricha. Potential fungus enzymes associated with BBP, DBP, and DEP degradation in SMCs (i.e., esterases, oxygenases, and oxidases/dehydrogenases) are uncovered by metaproteomic analysis using mass spectrometry. Bioreactor experiments indicate that the direct application of SMCs can remove BBP, DBP, and DEP from wastewater, through adsorption and biodegradation. The results of this study extend the application of white-rot fungi without laccases (e.g., Auricularia sp.) for the removal of organic pollutants which are not degraded by laccases. The application of SMCs for phthalate removal can be developed into a mycoremediation-based green and sustainable technology.

Arthrobacter is a universal responder to di-n-butyl phthalate (DBP) contamination in soils from various geographical locations

Plasticizer phthalic acid esters (PAEs) are commonly found as contaminants in various soils. Previous studies indicated that their natural degradation can substantially differ among soil types; however, potential implications of the soil microbiome remained largely unexplored. Here, we have collected ten soil types from nine different geographical regions of China to investigate the degradation of DBP therein and role of bacteria in this process. Results showed that the degradation rate of DBP was lowest in nutrient-poor red soils from Jiangxi Province, while it was highest in fluvo-aquatic soil from Hebei Province. Bacterial community responses to DBP substantially differed in each of the analyzed soils. Arthrobacter is known for its broad-spectrum activity in terms of DBP degradation in soil and was therefore implemented as bioremediating inoculant in many polluted environments. In the present study, network analyses indicated that synergism between soil bacteria increased following exposure to DBP. Arthrobacter and Sphingomonas were found to expand their positive interactions with other members of the microbiome in DBP-contaminated soils. The overall findings of our study provide a basis for biomarker development for detection of DBP contaminations and an extended basis for future bioremediation approaches based on beneficial bacteria.

Fenton-like degradation of di-n-butyl phthalate in landfill leachate by endogenous catalysts or iron, copper and manganese loaded bottom sediments

The work detailed here investigated the efficiency of heterogeneous Fenton-like processes in degrading endocrine-disrupting chemicals leached from plastics to landfill leachates, as exemplified by di-n-butyl phthalate (DBP). Specifically, a heterogeneous Fenton process was applied, as catalysed by two natural/endogenous and two modified bottom sediments. While the effectiveness of DBP degradation was indeed influenced by sediment type and composition, it was also affected by the factors of type of leachate, pH, time, sediment/catalysts and H2O2 dose. Sediments modified by impregnation with FeMnCu5%i as a catalyst were characterized by the highest catalytic activity (with almost 95% DBP degradation observed). Natural, endogenous catalysts in the form of dredged bottom sediments have also proved effective in the process studied. The use of bottom sediments in the role of alternative heterogeneous catalysts in Fenton processes thus represents a promising alternative environmental remediation technology, given their abundance, low cost and environment-friendly nature.

Impact of microplastic addition on degradation of dibutyl phthalate in offshore sediments

In this work, effects of microplastics (polypropylene and polystyrene) at four concentrations (0.2–10%, w/w) on di-n-butyl phthalate (DBP) degradation in offshore sediments were investigated. DBP degradation percentage was enhanced by 0.2% microplastics (7.3–11.0% increment) but was reduced by 2–10% microplastics (3.7–27.7% decrement). Meanwhile, addition of microplastics with higher sorption ability to DBP led to lower DBP degradation percentage. The initial concentration of bioavailable DBP in sediments decreased with the increase of microplastic sorption ability to DBP and microplastic concentration. Microbial community structure was more significantly influenced by microplastic type than by microplastic concentration. Significant positive correlation was observed between the total relative abundances of dominant DBP-degraders and DBP degradation percentage. The results indicated that the changes in DBP degradation percentage were related to both DBP bioavailability and the total relative abundances of dominant DBP-degraders. Hence, persistence of the pollutant in the coastal environment was microplastic type- and concentration-dependent.

MnFe2O4 decorated graphene as a heterogeneous catalyst for efficient degradation of di-n-butyl phthalate using catalytic ozonation in water

Magnetic, stable graphene-MnFe2O4 hybrids were synthesized by co-precipitation method for efficient degradation of di-n-butyl phthalate (DBP) using catalytic ozonation in water. The various synthesized catalysts were systematically characterized, and the catalytic activities in catalytic ozonation system were investigated. Moreover, a detailed mechanism of catalytic ozonation by synergistic function of graphene oxide (GO) and magnetic MnFe2O4 was proposed. Results showed that catalytic ozonation by 5-rGO-MFO-200 (MnFe2O4 calcined at 200 °C after 5 wt% GO doped) could significant boost the DBP degradation, which illustrated by the apparent rate constant (k = 0.0058 min−1) being nearly 4.2 times than that in ozone alone (k = 0.0241 min−1). The increased activities of 5-rGO-MFO-200 for the catalytic ozonation was attributed to its rich concentration of surface hydroxyl sites (SHSC), better charge electron transfer ability, favorable lattice structure and nanoparticles diffusion in contrast to bare MnFe2O4. All catalysts presented good recycling and stability in the repeated batch experiment, and the removal efficiency of DBP only decreased 3% after 5 times. The radical quenching tests verified that hydroxyl radicals (OH) was the dominant reactive oxygen species responsible for DBP degradation. Electrons cycling between Mn2+ and Mn3+ led to the decomposition of ozone to produce OH, which attacked DBP molecules to degrade into small molecular species and then further mineralized into CO2 and H2O. The synergistic function between magnetic MnFe2O4 and GO induced efficient ozone decomposition and more OH production.

Complete biodegradation of di-n-butyl phthalate (DBP) by a novel Pseudomonas sp. YJB6

Phthalate acid esters (PAEs) are environmentally ubiquitous and have aroused a worldwide concern due to their threats to environment and human health. Di-n-butyl phthalate (DBP) is one of the most frequently observed PAEs in the environment. In this study, a novel bacterium identified as Pseudomonas sp. YJB6 that isolated from PAEs-contaminated soil was determined to have strong DBP-degrading activity. A complete degradation of DBP in 200 mg/L was achieved within 3 days when YJB6 was cultivated at 31.4 °C with an initial inoculation size of 0.6 (OD600) in basic mineral salts liquid medium (MSM), pH 7.6. The degradation curves of DBP (50–2000 mg/L) fitted well the first-order kinetics model, with a half-life (t1/2) ranging from 0.86 to 1.88 d. The main degradation intermediates were identified as butyl-ethyl phthalate (BEP), mono-butyl phthalate (MBP), phthalic acid (PA) and benzoic acid (BA), indicating a new complex and complete biodegradation pathway presented by YJB6. DBP might be metabolized through de-esterification, β-oxidation, and hydrolysis, followed by entering the Krebs cycle of YJB6 as a final step. Strain YJB6 was successfully immobilized with sodium alginate (SA), polyvinyl alcohol (PVA), and SA-PVA. The immobilization significantly improved the stability and adaptability of the cells thus resulting in high volumetric DBP-degrading rates compared to that of the freely suspended cells. In addition, these immobilized cells can be reused for many cycles with well conserved in DBP-degrading activity. The ideal DBP degrading ability of the free and immobilized YJB6 cells suggests that strain YJB6, especially the SA-PVA+ YJB6 promises great potential to remove hazardous PAEs.

Effective degradation of Di-n-butyl phthalate by reusable, magnetic Fe3O4 nanoparticle-immobilized Pseudomonas sp. W1 and its application in simulation

Di-n-butyl phthalate (DBP), one of the most widely used plasticizers, has been listed as a priority pollutant because of its toxicity to both humans and animals. In this study, Pseudomonas sp. W1, isolated from activated sludge, was capable of degrading 99.88% of DBP (1000 mg L−1) within 8 days. We immobilized the W1 strain using Fe3O4 iron nanoparticles (IONPs) coated with poly-dopamine (PDA), and further evaluated its DBP degradation efficiency. The DBP degradation performance of W1 was improved by immobilization, exhibiting 99.69% of DBP degradation efficiency on the 6th day, which was 25.68% higher than un-immobilized W1. After three cycles of magnetic recycling and utilization, W1-PDA-IONPs retained 99.6% of their original efficiency. W1-PDA-IONPs were then used to degrade DBP in landfill leachate. When the proportion of raw leachate was ≤50%, DBP could be all degraded by W1-PDA-IONPs within 6 days. In 100% landfill leachate, DBP degradation efficiency after 10 days of incubation reached 66.40%. Furthermore, W1-PDA-IONPs cells in a simulated aeration system could be effectively magnetically separated at aeration rates from 60 to 600 mL min−1. These results highlight the potential of W1-PDA-IONPs in the bioremediation of DBP-contaminated waste water.

Elevated removal of di-n-butyl phthalate by catalytic ozonation over magnetic Mn-doped ferrospinel ZnFe2O4 materials: Efficiency and mechanism

Magnetic Mn-doped ZnFe2O4 (MnxZn1-xFe2O4, x = 0, 0.2, 0.5, 0.8) were synthesized by a sol-gel method at different calcination temperature (400 °C, 500 °C, 600 °C). The as-synthesized MnxZn1-xFe2O4 were systematically characterized and evaluated as heterogeneous catalysts for the ozonation of di-n-butyl phthalate (DBP) degradation in water. Importantly, a detailed mechanism of catalytic ozonation occurring on the surface of MnxZn1-xFe2O4 was proposed. The results showed that Mn0.5Zn0.5Fe2O4 calcined at 500 °C (500-Z0.5) could greatly enhance the degradation of DBP in the presence of ozone, which indicated by the first-order kinetic constant (k = 0.086 min−1) being approximately 5.73 times than that in the ozone alone (k = 0.015 min−1) system. The improved activity of 500-Z0.5 for the catalytic ozonation was attributed to its rich active sites of surface hydroxyl groups, better electron transfer ability, and more Mn2+ content. All catalysts presented favorable recycling and stability in the repeated batch experiment. In situ Raman spectroscopy and the radical quenching tests verified that hydroxyl radical (OH) was the primary radical species responsible for DBP degradation. A synergistic function between Mn, Zn and oxygen ensured efficient ozone decomposition and more OH generation.

Metabolic process of di-n-butyl phthalate (DBP) by Enterobacter sp. DNB-S2, isolated from Mollisol region in China

The accumulation of phthalate acid esters (PAEs) in the environment has aroused a global concern. Microbial degradation is the most promising method for removing PAEs from polluted environment. Di-n-butyl phthalate (DBP) is one of the most widely used PAEs. In this study, a highly efficient DBP-degrading strain, Enterobacter sp. DNB-S2 was isolated from Mollisol in northeast China, and the degradation rate of 500 mg L−1 DBP reached 44.10% at 5 °C and 91.08% at 50 °C within 7 days. A new intermediate, n-butyl benzoate BP, was detected, implying a new degradation pathway. The complete genome of the strain DNB-S2 was successfully sequenced to comprehensively understand of the entire DBP catabolic process. Key genes were proposed to be involved in DBP degradation, such as esterases, 3,4-dihydroxybenzoate decarboxylase and catechol 2,3-dioxygenase genes. Intermediate-utilization tests and real-time quantitative polymerase chain reaction (RT-qPCR) validated the proposed DBP catabolic pathway. The aboriginal bacterium DNB-S2 is a promising germplasm for restoring PAE-contaminated Mollisol regions at low temperature. This study provides novel insight into the catabolic mechanisms and abundant gene resources of PAE biodegradation.

Reservoir bottom sediments as heterogeneous catalysts for effective degradation of a selected endocrine-disrupting chemical via a Fenton-like process

The work detailed here investigated the efficiency of Fenton-like processes in degrading endocrine-disrupting chemicals, as exemplified by di-n-butyl phthalate (DBP). Specifically, a heterogeneous Fenton process was applied, as catalyzed by natural or modified bottom sediments collected from Rzeszów and Solina Reservoirs (Poland). A number of sediments with different physicochemical properties and different contents of Fe, Mn and Cu were in fact obtained and used, with “modification” entailing ion-exchange reaction and impregnation. It thus proved possible to demonstrate the possibility and legitimacy of Fenton's reagent being modified by natural bottom sediments that may therefore be regarded as heterogeneous catalysts, given a status as endogenous sources of iron, manganese and copper ions. While the effectiveness of DBP degradation was indeed influenced by sediment type and composition (and modification thereof), it was also affected by the factors of time, pH, DBP concentration, sediment dose and H2O2. The use of natural bottom sediments in the role of solid catalysts in heterogeneous Fenton processes represents a promising alternative to environmental remediation technology, given their abundance, low cost and environment-friendly nature.

The use of alternative catalysts in processes of the chemical degradation of di-n-butyl phthalate in aqueous solutions

The work detailed here investigated the efficiency of oxidising technologies in clearing aqueous solutions of di-n-butyl phthalate (DBP), a known endocrine-disrupting compound (EDCs). Specifically, this paper addresses the use of the classic Fenton process, and the development of a modification of Fenton's reagent targeted at the degradation of di-n-butyl phthalate in aqueous solution. The modification in question entailed the use of alternative catalysts or a mixture thereof. Hence oxidation by hydrogen peroxide (at various different concentrations), the classic Fenton process, was tested for the removal of DBP, alongside versions modified in terms of the quantitative and qualitative composition of a mixture of catalysts, and the presence of metal ions, as well as the factors of time, pH and initial DBP concentration. Given that it did not exceed 31%, the degradation of DBP we achieved using H2O2 could not be regarded as satisfactory. In contrast, the addition of 2.5 mM L−1 of Fe2+ was found to mediate almost complete elimination of the phthalate from the model solution. Also confirmed by experimentation were the benefits of using homogeneous catalysts (compounds of copper(II) and manganese(II)) as alternatives to Fe2+ in the Fenton reagent. A key experimental achievement was to confirm the applicability of a catalyst formed from a mixture of 2 or 3 types of transition metal ion. A Fenton reaction extended to ions like Mn2+ and Cu2+ in particular is seen to eliminate factors/parameters discouraging practical industrial use of the classic Fenton process.

Variation in metabolism and degradation of di-n-butyl phthalate (DBP) by high- and low-DBP accumulating cultivars of rice (Oryza sativa L.) and crude enzyme extracts

Crops can take up and accumulate di-n-butyl phthalate (DBP), an extensively used plasticizer with endocrine disrupting effect, which poses potential risk to human health. Our previous study found the genotype variation in accumulation of DBP by different cultivars of rice (Oryza sativa L.). Nevertheless, the effect of DBP metabolism in vivo on the accumulation variation among different plant cultivars remains unknown. In this study, metabolism variation of DBP by low (Fengyousimiao) and high (Peizataifeng) DBP-accumulating cultivars of rice and the key enzymes involving in DBP metabolism in rice plants were investigated using in vivo exposure of rice plants and in vitro exposure of root crude enzyme extracts. Both mono-n-butyl phthalate (MBP) and phthalic acid (PA) were detected as DBP metabolites in all rice tissues (i.e., roots, stems, leaves) and crude enzyme extracts with MBP predominance. DBP metabolism occurred simultaneously when DBP uptake with the highest metabolism in roots in vivo. Degradation of DBP in root crude enzyme extracts fitted well with the first order kinetics (R2 = 0.49–0.76, P < 0.05). The activity of carboxylesterase (CXE) in root crude enzyme extracts was significantly positively correlated with DBP degradation rates. CXE played an important role in DBP metabolism of rice plants, confirming by the fact that triphenyl phosphate of CXE inhibitor could inhibit DBP metabolism of in vivo and in vitro exposure. This result was further confirmed by in vitro degradation of DBP with the commercial pure CXE. The crude enzyme solution from roots of Fengyousimiao with higher CXE activity had significantly higher DBP degradation rates than that of Peizataifeng. However, Fengyousimiao with lower tolerance to DBP stress and higher inhibition by triphenyl phosphate displayed lower DBP metabolism ability in vivo than Peizataifeng.

Effects of microphytobenthos Cylindrotheca closterium on the fate of di-n-butyl phthalate in an aquatic microcosm

Effects of Cylindrotheca closterium, a marine benthic diatom, on the fate of di-n-butyl phthalate (DBP) in a water-sediment system were investigated. Model calculation results showed that DBP residue was 38.5% lower in the system with C. closterium than in the system without C. closterium. The net flux from water to sediment increased by 7.3 times in the presence of C. closterium. As a result, the total biodegradation flux of DBP in the system with C. closterium was increased by 25.6%. According to the 16 s rDNA sequencing, the presence of C. closterium decreased the bacterial population as well as bacterial community diversity in sediments. Moreover, the population of C. closterium, capable of efficiently degrading DBP, was much higher than that of the dominant DBP-degrading bacteria, demonstrating that degradation of DBP by C. closterium should be the main reason for the degradation enhancement in sediments.

Biodegradation of di‑n‑butyl phthalate by psychrotolerant Sphingobium yanoikuyae strain P4 and protein structural analysis of carboxylesterase involved in the pathway

A priority pollutant Phthalate Esters (PAEs) are widely used as plasticizers and are responsible mainly for carcinogenicity and endocrine disruption in human. For the bioremediation of PAEs, a psychrotolerant Sphingobium yanoikuyae strain P4, capable of utilizing many phthalates di‑methyl phthalate (DMP), di‑ethyl phthalate (DEP), di‑n‑butyl phthalate (DBP), di‑isobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), and few Polycyclic Aromatic Hydrocarbons as the sole source of carbon and energy was isolated from Palampur, Kangra, Himachal Pradesh, India. 100% utilization of DBP (1 g L−1) by the strain was observed within 24 h of incubation at 28 °C. Interestingly the strain also degraded DBP completely at 20 °C and 15 °C within 36 h and 60 h, respectively. Esterase involved in DBP degradation was found to be inducible in nature and intracellular. Comparative sequence analysis of carboxylesterase enzyme sequences revealed conserved motifs: G-X-S-X-G and -HGG- which were the characteristic peptide motifs reported in different esterases. Structural analysis showed that the enzyme belongs to serine hydrolase superfamily, which has an α/β hydrolase fold. Interaction and binding of DBP to a catalytic Ser184 residue in the esterase enzyme were also analysed. In conclusion, carboxylesterase possess the required active site which may be involved in the catabolism of DBP.

Enhanced catalytic ozonation treatment of dibutyl phthalate enabled by porous magnetic Ag-doped ferrospinel MnFe2O4 materials: Performance and mechanism

Enhanced catalytic ozonation of di-n-butyl phthalate (DBP), a recalcitrant waterborne pollutant, was enabled by a family of novel Ag-doped spinel ferrites (MnFe2O4) materials. A sol-gel approach was used to synthesize the Ag-doped MnFe2O4 catalysts, resulting in a highly porous structure with good magnetic property. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the incorporation of Ag into the MnFe2O4 structure. The Ag-doped MnFe2O4 significantly accelerated ozonation of DBP, and a Ag doping of 0.5% (relative to Mn) enhanced the apparent rate constants by a factor of three and two under circumneutral conditions, compared to the ozone-alone and undoped MnFe2O4 systems, respectively. Catalyst surface hydroxyl groups were identified as a critical factor for ozone decomposition and the subsequent hydroxyl radical production. Spectroscopic and electrochemical measurements showed that Ag doping enhanced DBP degradation by increasing the density of surface hydroxyl groups and promoting the electron transfer and cycling between the catalyst and ozone. The Ag-doped MnFe2O4 catalysts exhibited high stability and can be used for multiple cycles.

Catalytic ozonation of di-n-butyl phthalate degradation using manganese ferrite/reduced graphene oxide nanofiber as catalyst in the water

Graphene oxide doping MnFe2O4 (rGO-MnFe2O4) nanofibers were synthesized via electrospinning method and applied to degrade refractory Di-n-butyl Phthalate (DBP) by catalytic ozonation in the water. Characterizations and effect of various conditions on DBP removal were investigated. Meanwhile, the mechanism of enhanced DBP degradation after rGO incorporation was explored intensively. Results showed that 5 wt% GO doping into MnFe2O4 improved the concentration of surface hydroxyl sites (SHSC), the oxidation potential, material diffusion and charge electronic transfer ability in contrast to MnFe2O4 nanofibers, resulting in significantly enhanced DBP degradation compared with ozonation alone. Chemisorbed oxygen groups (MnOH, COH or COOH) on the surface of rGO-MnFe2O4 played a key role in generating radicals, which was the origin of catalytic ozonation reaction. Moreover, a good positive linear relation between SHSC and DBP removal was found. The electrons cycle between Mn2+ and Mn3+ induced the ozone decomposition to produce hydroxyl radicals, which was the major impetus for DBP degradation in 5%rGO-MnFe2O4/O3 system. Composite nanofiber of 5%rGO-MnFe2O4 had a good stability and removal rate only decreased for 4% after five times reuse.

Removal mechanism of di-n-butyl phthalate and oxytetracycline from aqueous solutions by nano-manganese dioxide modified biochar.

In this work, nano-manganese dioxide (nMnO2)-modified biochar (BC) was synthesized in order to improve BC's adsorption capacity for di-n-butyl phthalate (DBP) and oxytetracycline (OTC). The results showed that nMnO2 on the BC surface exhibited a poor crystallinity and oxidation state (Mn (IV)). Sorption experiments showed that, compared to BC, DBP sorption capacity of nMnO2-BC (1:20) and OTC sorption capacity of nMnO2-BC (1:10) were 0.0364 and 0.0867mmol/g, respectively, which are significantly higher than that of BC (0.0141 and 0.0151mmol/g). Kinetics and isotherm experiments indicated that physical adsorption and chemical interactions have both exerted their impacts on the adsorption process. Further X-ray photoelectron spectroscopy (XPS) analysis showed that part of the Mn (IV) in nMnO2-BC was reduced to Mn (III) and Mn (II) after DBP or OTC adsorption. Therefore, we suggest the nMnO2 also acted as an oxidizer on modified BC, which may accelerate the degradation of DBP and OTC.