27 research outputs found
New Insights into the Mechanism of the Catalytic Decomposition of Hydrogen Peroxide by Activated Carbon: Implications for Degradation of Diethyl Phthalate
This
study investigated the catalytic decomposition of H<sub>2</sub>O<sub>2</sub> by activated carbon (AC) and its implications for
degradation of diethyl phthalate (DEP). It was found that AC exhibited
excellent catalytic ability for decomposition H<sub>2</sub>O<sub>2</sub> and degradation of DEP. HNO<sub>3</sub> modification altered
the surface characteristics of AC together with the concentrations
and types of AC free radicals (FRs), which further promoted generation
of <sup>ā¢</sup>OH. Positive correlations were found between
FR concentration and generation of <sup>ā¢</sup>OH (<i>R</i><sup>2</sup> = 0.856) and between the proportion of surface-bound
hydroxyl groups (CāOH) and the decomposition rate of H<sub>2</sub>O<sub>2</sub> (<i>R</i><sup>2</sup> = 0.776), indicating
that FRs in AC were the main contributor to <sup>ā¢</sup>OH
generation, whereas CāOH groups were predominantly responsible
for decomposition of H<sub>2</sub>O<sub>2</sub>. Electron capturing
studies demonstrated that the decomposition reaction likely involves
the transfer of FR electrons to H<sub>2</sub>O<sub>2</sub> to induce
formation of <sup>ā¢</sup>OH
Thermodynamic Mechanism and Interfacial Structure of Kaolinite Intercalation and Surface Modification by Alkane Surfactants with Neutral and Ionic Head Groups
Intercalation and
surface modification of clays with surfactants
are the essential process to tailor the claysā surface chemistry
for their extended applications. A full understanding of the interaction
mechanism of surfactants with clay surfaces is crucial to engineer
clay surfaces for meeting a particular requirement of industrial applications.
In this study, the thermodynamic mechanism involved in the intercalation
and surface modification of methanol preintercalated kaolinite by
three representative alkane surfactants with different head groups,
dodecylamine, cetylĀtrimethylĀammonium chloride (CTAC),
and sodium stearate, were investigated using the adaptive biasing
force accelerated molecular dynamics simulations. In addition, the
interaction energies of surfactants with an interlayer environment
(alumina surface, siloxane surface, and interlayer methanol) of methanol
preintercalated kaolinite were also calculated. It was found that
the intercalation free energy of CTAC with a cationic head group was
relatively larger than that of stearate with an anionic head group
and dodecylamine with a neutral head group. The attractive electrostatic
and van der Waals interactions of surfactants with an interlayer environment
contributed to the intercalation and surface modification process
with the electrostatic force playing the significant role. This study
revealed the underlying mechanism involved in the intercalation and
surface modification process of methanol preintercalated kaolinite
by surfactants, which can help in further design of kaolinite-based
organic clays with desired properties for specific applications
Reduction of Carbadox Mediated by Reaction of Mn(III) with Oxalic Acid
ManganeseĀ(III) geocomponents are commonly found in the
soil environment,
yet their roles in many biogeochemical processes remain unknown. In
this study, we demonstrated that Mn<sup>III</sup> generated from the
reaction of MnO<sub>2</sub> and oxalic acid caused rapid and extensive
decompositions of a quinoxaline-di-<i>N</i>-oxide antibiotics,
viz carbadox. The reaction occurred primarily at the quinoxaline-di-<i>N</i>-oxide moiety resulting in the removal of one īøO
from N1-oxide and formation of desoxycarbadox. The reaction rate was
accelerated by increasing amounts of Mn<sup>III</sup>, carbadox and
oxalate. The critical step in the overall reaction was the formation
of a quinoxaline-di-<i>N</i>-oxide/Mn<sup>III</sup>/oxalate
ternary complex in which Mn<sup>III</sup> functioned as the central
complexing cation and electron conduit in which the arrangement of
ligands facilitated electron transfer from oxalate to carbadox. In
the complex, the CīøC bond in oxalate was cleaved to create
CO<sub>2</sub><sup>āā¢</sup> radicals, followed by electron
transfer to carbadox through the Mn<sup>III</sup> center. This proposed
reaction mechanism is supported by the reaction products formed, reaction
kinetics, and quantum mechanical calculations. The results obtained
from this study suggest that naturally occurring Mn<sup>III</sup>āoxalic
acid complexes could reductively decompose certain organic compounds
in the environment such as the antibiotic quinoxaline-di-<i>N</i>-oxide
A Mechanistic Understanding of Hydrogen Peroxide Decomposition by Vanadium Minerals for Diethyl Phthalate Degradation
The
interaction of naturally occurring minerals with H<sub>2</sub>O<sub>2</sub> affects the remediation efficiency of polluted sites
in in situ chemical oxidation (ISCO) treatments. However, interactions
between vanadiumĀ(V) minerals and H<sub>2</sub>O<sub>2</sub> have rarely
been explored. In this study, H<sub>2</sub>O<sub>2</sub> decomposition
by various vanadium-containing minerals including VĀ(III), VĀ(IV), and
VĀ(V) oxides was examined, and the mechanism of hydroxyl radical (<sup>ā¢</sup>OH) generation for contaminant degradation was studied.
Vanadium minerals were found to catalyze H<sub>2</sub>O<sub>2</sub> decomposition efficiently to produce <sup>ā¢</sup>OH for diethyl
phthalate (DEP) degradation in both aqueous solutions with a wide
pH range and in soil slurry. Electron paramagnetic resonance (EPR),
X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) analyses,
and free radical quenching studies suggested that <sup>ā¢</sup>OH was produced via single electron transfer from VĀ(III)/VĀ(IV) to
H<sub>2</sub>O<sub>2</sub> followed a Fenton-like pathway on the surface
of V<sub>2</sub>O<sub>3</sub> and VO<sub>2</sub> particles, whereas
the oxygen vacancy (OV) was mainly responsible for <sup>ā¢</sup>OH formation on the surface of V<sub>2</sub>O<sub>5</sub> particles.
This study provides new insight into the mechanism of interactions
between vanadium minerals and H<sub>2</sub>O<sub>2</sub> during H<sub>2</sub>O<sub>2</sub>-based ISCO
Key Role of Persistent Free Radicals in Hydrogen Peroxide Activation by Biochar: Implications to Organic Contaminant Degradation
We
investigated the activation of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) by biochars (produced from pine needles, wheat, and
maize straw) for 2-chlorobiphenyl (2-CB) degradation in the present
study. It was found that H<sub>2</sub>O<sub>2</sub> can be effectively
activated by biochar, which produces hydroxyl radical (<sup>ā¢</sup>OH) to degrade 2-CB. Furthermore, the activation mechanism was elucidated
by electron paramagnetic resonance (EPR) and salicylic acid (SA) trapping
techniques. The results showed that biochar contains persistent free
radicals (PFRs), typically ā¼10<sup>18</sup> unpaired spins/gram.
Higher trapped [<sup>ā¢</sup>OH] concentrations were observed
with larger decreases in PFRs concentration, when H<sub>2</sub>O<sub>2</sub> was added to biochar, indicating that PFRs were the main
contributor to the formation of <sup>ā¢</sup>OH. This hypothesis
was supported by the linear correlations between PFRs concentration
and trapped [<sup>ā¢</sup>OH], as well as <i>k</i><sub>obs</sub> of 2-CB degradation. The correlation coefficients
(<i>R</i><sup>2</sup>) were 0.723 and 0.668 for PFRs concentration
vs trapped [<sup>ā¢</sup>OH], and PFRs concentration vs <i>k</i><sub>obs</sub>, respectively, when all biochars pyrolyzed
at different temperatures were included. For the same biochar washed
by different organic solvents (methanol, hexane, dichloromethane,
and toluene), the correlation coefficients markedly increased to 0.818ā0.907.
Single-electron transfer from PFRs to H<sub>2</sub>O<sub>2</sub> was
a possible mechanism for H<sub>2</sub>O<sub>2</sub> activation by
biochars, which was supported by free radical quenching studies. The
findings of this study provide a new pathway for biochar implication
and insight into the mechanism of H<sub>2</sub>O<sub>2</sub> activation
by carbonaceous materials (e.g., activated carbon and graphite)
Reductive Hexachloroethane Degradation by S<sub>2</sub>O<sub>8</sub><sup>ā¢ā</sup> with Thermal Activation of Persulfate under Anaerobic Conditions
Despite
that persulfate radical (S<sub>2</sub>O<sub>8</sub><sup>ā¢ā</sup>) is an important radical species formed from
the persulfate (PS) activation process, its reactivity toward contaminant
degradation has rarely been explored. In this study, we found that
S<sub>2</sub>O<sub>8</sub><sup>ā¢ā</sup> efficiently
degrades the contaminant hexachloroethane (HCA) under anaerobic conditions,
whereas HCA degradation is negligible in the presence of oxygen. We
observed dechlorination products such as pentachloroethane, tetrachloroethylene,
and Cl<sup>ā</sup> during HCA degradation, which suggest that
HCA degradation is mainly a reductive process under anaerobic conditions.
Using free radical quenching and electron paramagnetic resonance (EPR)
experiments, we confirmed that S<sub>2</sub>O<sub>8</sub><sup>ā¢ā</sup> forms from the reaction between sulfate radical (SO<sub>4</sub><sup>ā¢ā</sup>) and S<sub>2</sub>O<sub>8</sub><sup>2ā</sup>, which are the dominant reactive species in HCA degradation. Density
functional theory (DFT) calculations were used to elucidate the pathways
of HCA degradation and S<sub>2</sub>O<sub>8</sub><sup>ā¢ā</sup> radical decomposition. Further investigation showed that S<sub>2</sub>O<sub>8</sub><sup>ā¢ā</sup> can efficiently degrade
HCA and DDTs in soil via reduction during the thermal activation of
PS under anaerobic conditions. The finding of this study provide a
novel strategy for the reductive degradation of contaminant when PS-based
in situ chemical oxidation used in the remediation of soil and groundwater,
particularly those contaminated with highly halogenated compounds
Degradation of Organic Dyes via Bismuth Silver Oxide Initiated Direct Oxidation Coupled with Sodium Bismuthate Based Visible Light Photocatalysis
Organic dye degradation was achieved via direct oxidation
by bismuth
silver oxide coupled with visible light photocatalysis by sodium bismuthate.
Crystal violet dye decomposition by each reagent proceeded via two
distinct pathways, each involving different active oxygen species.
A comparison of each treatment method alone and in combination demonstrated
that using the combined methods in sequence achieved a higher degree
of degradation, and especially mineralization, than that obtained
using either method alone. In the combined process direct oxidation
acts as a pretreatment to rapidly bleach the dye solution which substantially
facilitates subsequent visible light photocatalytic processes. The
integrated sequential direct oxidation and visible light photocatalysis
are complementary manifesting <i>a</i> > 100% increase
in
TOC removal, compared to either isolated method. The combined process
is proposed as a novel and effective technology based on one primary
material, sodium bismuthate, for treating wastewaters contaminated
by high concentrations of organic dyes
Table_3_From tumor mutational burden to characteristic targets analysis: Identifying the predictive biomarkers and natural product interventions in cancer management.DOCX
High-throughput next-generation sequencing (NGS) provides insights into genome-wide mutations and can be used to identify biomarkers for the prediction of immune and targeted responses. A deeper understanding of the molecular biological significance of genetic variation and effective interventions is required and ultimately needs to be associated with clinical benefits. We conducted a retrospective observational study of patients in two cancer cohorts who underwent NGS in a āreal-worldā setting. The association between differences in tumor mutational burden (TMB) and clinical presentation was evaluated. We aimed to identify several key mutation targets and describe their biological characteristics and potential clinical value. A pan-cancer dataset was downloaded as a verification set for further analysis and summary. Natural product screening for the targeted intervention of key markers was also achieved. The majority of tumor patients were younger adult males with advanced cancer. The gene identified with the highest mutation rate was TP53, followed by PIK3CA, EGFR, and LRP1B. The association of TMB (0ā103.7 muts/Mb) with various clinical subgroups was determined. More frequent mutations, such as in LRP1B, as well as higher levels of ferritin and neuron-specific enolase, led to higher TMB levels. Further analysis of the key targets, LRP1B and APC, was performed, and mutations in LRP1B led to better immune benefits compared to APC. APC, one of the most frequently mutated genes in gastrointestinal tumors, was further investigated, and the potential interventions by cochinchinone B and rottlerin were clarified. In summary, based on the analysis of the characteristics of gene mutations in the āreal world,ā we obtained the potential association indicators of TMB, found the key signatures LRP1B and APC, and further described their biological significance and potential interventions.</p
Image_2_From tumor mutational burden to characteristic targets analysis: Identifying the predictive biomarkers and natural product interventions in cancer management.JPEG
High-throughput next-generation sequencing (NGS) provides insights into genome-wide mutations and can be used to identify biomarkers for the prediction of immune and targeted responses. A deeper understanding of the molecular biological significance of genetic variation and effective interventions is required and ultimately needs to be associated with clinical benefits. We conducted a retrospective observational study of patients in two cancer cohorts who underwent NGS in a āreal-worldā setting. The association between differences in tumor mutational burden (TMB) and clinical presentation was evaluated. We aimed to identify several key mutation targets and describe their biological characteristics and potential clinical value. A pan-cancer dataset was downloaded as a verification set for further analysis and summary. Natural product screening for the targeted intervention of key markers was also achieved. The majority of tumor patients were younger adult males with advanced cancer. The gene identified with the highest mutation rate was TP53, followed by PIK3CA, EGFR, and LRP1B. The association of TMB (0ā103.7 muts/Mb) with various clinical subgroups was determined. More frequent mutations, such as in LRP1B, as well as higher levels of ferritin and neuron-specific enolase, led to higher TMB levels. Further analysis of the key targets, LRP1B and APC, was performed, and mutations in LRP1B led to better immune benefits compared to APC. APC, one of the most frequently mutated genes in gastrointestinal tumors, was further investigated, and the potential interventions by cochinchinone B and rottlerin were clarified. In summary, based on the analysis of the characteristics of gene mutations in the āreal world,ā we obtained the potential association indicators of TMB, found the key signatures LRP1B and APC, and further described their biological significance and potential interventions.</p
Table_7_From tumor mutational burden to characteristic targets analysis: Identifying the predictive biomarkers and natural product interventions in cancer management.DOCX
High-throughput next-generation sequencing (NGS) provides insights into genome-wide mutations and can be used to identify biomarkers for the prediction of immune and targeted responses. A deeper understanding of the molecular biological significance of genetic variation and effective interventions is required and ultimately needs to be associated with clinical benefits. We conducted a retrospective observational study of patients in two cancer cohorts who underwent NGS in a āreal-worldā setting. The association between differences in tumor mutational burden (TMB) and clinical presentation was evaluated. We aimed to identify several key mutation targets and describe their biological characteristics and potential clinical value. A pan-cancer dataset was downloaded as a verification set for further analysis and summary. Natural product screening for the targeted intervention of key markers was also achieved. The majority of tumor patients were younger adult males with advanced cancer. The gene identified with the highest mutation rate was TP53, followed by PIK3CA, EGFR, and LRP1B. The association of TMB (0ā103.7 muts/Mb) with various clinical subgroups was determined. More frequent mutations, such as in LRP1B, as well as higher levels of ferritin and neuron-specific enolase, led to higher TMB levels. Further analysis of the key targets, LRP1B and APC, was performed, and mutations in LRP1B led to better immune benefits compared to APC. APC, one of the most frequently mutated genes in gastrointestinal tumors, was further investigated, and the potential interventions by cochinchinone B and rottlerin were clarified. In summary, based on the analysis of the characteristics of gene mutations in the āreal world,ā we obtained the potential association indicators of TMB, found the key signatures LRP1B and APC, and further described their biological significance and potential interventions.</p