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1.
Chemosphere ; 341: 139932, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37619744

ABSTRACT

Birnessite plays a crucial role in regulating the fate of contaminants in soil, which is affected by the crystal structure of birnessite. In this study, the transformation of triclinic birnessite to hexagonal birnessite was examined at various pH values, and their reactivity towards norfloxacin was investigated. The findings indicate that the conversion from triclinic birnessite to hexagonal birnessite occurs under pH conditions lower than 7. The lower of the solution pH where the birnessite formed, the higher the surface reactivity. Throughout the transformation process, the migration of Mn3+ and the increased interlayer protons generated more reactive oxygen species, which enhanced the surface reactivity towards norfloxacin. Specifically, at a conversion pH of 1, the norfloxacin removal rate significantly increases from 14% to 97% compared to triclinic birnessite. The mechanism of norfloxacin removal by triclinic and hexagonal birnessite is illustrated. These findings provide valuable insights into the dynamic transformation of birnessites in aqueous environments with varying pH values and their impact on norfloxacin removal.


Subject(s)
Manganese , Norfloxacin , Oxidation-Reduction , Manganese/chemistry , Oxides/chemistry , Hydrogen-Ion Concentration
2.
Chemosphere ; 305: 135326, 2022 Oct.
Article in English | MEDLINE | ID: mdl-35709846

ABSTRACT

In this study, a new low-cost carbon-based material was prepared via the carbonization of methylene blue adsorbed halloysite (CMH) at different temperatures in a nitrogen atmosphere, which was named CMH-T (T-Temperature). The performance of CMH-T was explored and the effects of initial pH values, catalyst dosage, phenol (PE) concentrations, peroxymonosulfate (PMS) concentrations, and water background compounds on PE degradation were investigated systematically. The results indicated that CMH800 exhibited the best performance to activate PMS for degrading PE. Specifically, 92% PE was degraded within 30 min with a constant rate (kobs) of 0.1186 min-1 in the CMH800/PMS system. Furthermore, CMH800 was efficient over a wide pH range (pH 3-9) and showed a slight inhibition to inorganic anions. Quenching experiments, electron spin resonance (ESR) analysis, and electrochemical analysis confirmed that PE was degraded through non-radical pathways dominated by single oxygen (1O2) and mediated electron transfer processes in the CMH800/PMS system. In addition, the predicted toxicity of intermediates through ECOSAR software based on QSAR (Quantitative Structure - Activity Relationship) model indicated that most of the intermediates had a low risk to water environment. Therefore, the CMH800 has a good potential for wastewater treatment applications.


Subject(s)
Methylene Blue , Phenol , Clay , Peroxides/chemistry , Phenols , Water
3.
Water Res ; 219: 118529, 2022 Jul 01.
Article in English | MEDLINE | ID: mdl-35569277

ABSTRACT

A system of Cu2+/calcite/PDS was constructed to degrade sulfadiazine (SDZ). Different from the traditional Cu-mediated activation, a low concentration of Cu2+ that met drinking water standards (≤ 1 mg/L) transformed into Cu(Ⅱ) solid in the presence of calcite, and then enhanced the degradation of SDZ via PDS activation over a pH range from 3 to 9. According to scavenger and chemical probe experiments, Cu(Ⅲ), rather than radicals (hydroxyl radicals and sulfate radicals) and singlet oxygen, was the predominant reactive species, which was responsible for the degradation of SDZ. Based on the results of XRD, ATR-FTIR, and CV curves et al., CuCO3 was the main complex with high reactivity for PDS activation to form Cu(Ⅲ). Moreover, detailed degradation pathways of sulfadiazine were proposed according to the UPLC-ESI-MS/MS and their toxicity was predicted by ECOSAR. Besides, the real water matrix would not seriously affect the degradation of SDZ in the Cu2+/calcite/PDS system. In summary, this study reveals a new insight into the synergistic effect of Cu2+ and calcite on the SDZ degradation, and promotes an understanding of the environmental benefits of natural calcite.


Subject(s)
Calcium Carbonate , Sulfadiazine , Tandem Mass Spectrometry
4.
Environ Sci Pollut Res Int ; 29(25): 38006-38016, 2022 May.
Article in English | MEDLINE | ID: mdl-35067884

ABSTRACT

Naturally occurring Mn-rich limonite mainly composed of goethite and manganese oxides was used to remove tetracycline (TC) from the aqueous solution. The effects of dosage, initial solution pH, temperature, and coexisting anions on TC removal were investigated. Results showed that 95% of TC (30.0 mg·L-1) was removed in a wide pH range of 3.0-9.0 by limonite with high specific surface area (145.0 m2·g-1) and mesoporous structure. The presence of Cl-, NO3-, and SO42- in the studied concentration range did not influence TC removal efficiency significantly, while PO43- inhibited the adsorption of TC over limonite due to the competition with TC for active sites. Integrated with the FT-IR analysis, electrostatic interaction and complexation were proved to be the adsorption mechanisms of TC by limonite. The quenching experiments and ESR analysis revealed that singlet oxygen (1O2) also was involved in TC degradation. In addition, limonite displayed an efficient recycling performance and stability after four cycles. This study revealed that the Mn-rich limonite was a promising adsorbent for TC removal from aqueous solutions and promoted the application of natural mineral material in the environmental field.


Subject(s)
Water Pollutants, Chemical , Water Purification , Adsorption , Anti-Bacterial Agents/chemistry , Ferric Compounds/chemistry , Hydrogen-Ion Concentration , Kinetics , Spectroscopy, Fourier Transform Infrared , Tetracycline/chemistry , Water Pollutants, Chemical/analysis , Water Purification/methods
5.
Chemosphere ; 282: 131091, 2021 Nov.
Article in English | MEDLINE | ID: mdl-34119731

ABSTRACT

In this study, calcite was investigated as an activator for the norfloxacin (NOR) degradation by peroxymonosulfate (PMS). Under optimum conditions, the NOR removal percentage was 99.7% within 60 min, and the pseudo-first-order kinetics effectively described the two-stage oxidation process. The NOR removal percentage improved from 10.4% to 91.5% and the reaction rate constant elevated from 0.0010 to 0.1217 min-1 when 0.5 g/L calcite was added compared to that without calcite addition. Furthermore, the results of radical scavenger and electron spin resonance trapping indicated that the favorable alkaline environment and a proper level of carbonate in the Calcite/PMS system facilitated the activation of PMS to generate 1O2 for rapid NOR degradation. Compared with NaOH, calcite was able to maintain the pH (8-9) of the reaction system stable. Besides, the content of anions with buffering capacity and organic matter in the water matrix influenced the removal percentage of NOR. Seven intermediates were identified and the NOR degradation pathways were suggested. The findings of this research provided an environmentally friendly activator for remediation of organic wastewater and deepened the understanding of the interaction between calcium carbonate and PMS.


Subject(s)
Calcium Carbonate , Norfloxacin , Peroxides , Wastewater
6.
Sci Total Environ ; 784: 147117, 2021 Aug 25.
Article in English | MEDLINE | ID: mdl-33895517

ABSTRACT

Occurring naturally siderite (FeCO3) was used as the heterogeneous catalyst to activate peroxodisulfate (PDS) for the degradation of sulfadiazine under different initial pH values. The findings of this system exhibited various ROS (e.g. 1O2, SO4- and OH) present during a wide range of pH values. Among them, 1O2 could significantly facilitate the initial degradation rate, and the increased pH enhanced the role of 1O2. The factors including initial pH values, siderite dosage, PDS concentration, initial contaminants concentration, and water matrix were discussed. The role of each ROS was investigated through quenching test and electron paramagnetic resonance (EPR). Furthermore, the comprehensive degradation process was proposed based on the LC-MS results. And the cycle test demonstrates the reusability of siderite at a pH of 3. Accordingly, this study is of great significance for understanding the degradation of such sulfonamide pollutants in the siderite/PDS system.

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