Hierarchical porous N-doped carbon encapsulated CoFe2O4-CoO nanoparticles derived from layered double hydroxide/chitosan biocomposite for the enhanced degradation of tetracycline

Enhancing catalytic activity of CuCoFe-layered double oxide towards peroxymonosulfate activation by coupling with biochar derived from durian peel for antibiotic degradation: The role of C=O in biochar and underlying mechanism of built-in electric field

CuCoFe-LDO/BCD was successfully synthesized from CuCoFe-LDH and biochar derived from durian shell (BCD). Ciprofloxacin (CFX) degraded more than 95% mainly by O2•- and 1O2 in CuCoFe-LDO/BCD(2/1)/PMS system within 10 min with a rate constant of 0.255 min-1, which was 14.35 and 2.66 times higher than those in BCD/PMS and CuCoFe-LDO/PMS systems, respectively. The catalytic system exhibited good performance over a wide pH range (3-9) and high degradation efficiency of other antibiotics. Built-in electric field (BIEF) driven by large difference in the work function/Fermi level ratio between CuCoFe-LDO and BCD accelerated continuous electron transfer from CuCoFe-LDO to BCD to result in two different microenvironments with opposite charges at the interface, which enhanced PMS adsorption and activation via different directions. As a non-radical, 1O2 was mainly generated via PMS activation by C=O in BCD. The presence of C=O in BCD resulted in an increase in atomic charge of C in C=O and redistributed the charge density of other C atoms. As a result, strong adsorption of PMS at C atom in C=O and other C with a high positive charge was favorable for 1O2 generation, whereas an enhanced adsorption of PMS at negatively charged C accounted for the generation of •OH and SO4•-. After adsorption, electrons in C of BCD became deficient and were fulfilled with those transferred from CuCoFe-LDO driven by BIEF, which ensured the high catalytic activity of CuCoFe-LDO/BCD. O2•-, on the other hand, was generated via several pathways that involved in the transformation of •OH and SO4•- originated from PMS activation by the transition of metal species in CuCoFe-LDO and negatively charged C in BCD. This study proposed a new idea of fabricating a low-cost metal-LDH and biomass-derived catalyst with a strong synergistic effect induced by BIEF for enhancing PMS activation and antibiotic degradation.

Cerium oxide /Co-Co Prussian blue analogue composite catalyst for enhanced peroxymonosulfate activation for effective removal of tetracycline hydrochloride from water

In this paper, a novel CeO2/Co3[Co(CN)6]2 (CeO2/PBACo-Co) composite was prepared with co-precipitation and utilized to activate peroxymonosulfate (PMS) to eliminate tetracycline hydrochloride (TCH). Catalyst screening showed that the composite with a CeO2:PBACo-Co mass ratio of 1:5 (namely, 0.2-CeO2/PBACo-Co) had the best performance. The degradation efficiency of TCH in 0.2-CeO2/PBACo-Co/Oxone system was investigated. The experimental results illustrated that 98% of 50 mg/L TCH and 48.5% of TOC were degraded by 50 mg/L 0.2-CeO2/PBACo-Co and 400 mg/L Oxone within 120 min at 25 °C and initial pH 5.3. Recycling studies showed that the elimination rate of TCH can still achieve 85.8% after five cycles, suggesting that 0.2-CeO2/PBACo-Co composite processes good reusability. Trapping experiments and EPR tests revealed that the reaction system produced multiple active species (1O2, O2•-, SO4•-, and •OH). We proposed the catalytic mechanism of 0.2-CeO2/PBACo-Co for PMS activation, which mainly involves the promoted Co3+/Co2+ cycle by Ce3+ donated electrons. These results indicate that CeO2/PBACo-Co composite is an effective catalyst for wastewater remediation.

Porous-carbon/manganese composite catalyst transformed from waste biomass as peroxymonosulfate activator for carbamazepine degradation

Activation of peroxymonosulfate (PMS) with solid catalysts for organic pharmaceutical degradation still faces challenge due to the demand of inexpensive catalysts. In this study, manganese-oxidizing microalgae (MOM) and its associated biogenic manganese oxides (BMO) were employed to prepare biomass-transformed porous-carbon/manganese (B-PC/Mn) catalyst through high-temperature calcination (850 °C). Remarkably, 100 % of carbamazepine (CBZ) was degraded within 30 min in the B-PC/Mn/PMS system. The degradation kinetic constant was 0.1718 min-1, which was 44.0 times higher than that of the biomass-transformed porous carbon mixed with MnOx activated PMS system. 1O2 was generated in the B-PC/Mn/PMS system, which is responsible for CBZ degradation. The MOM-BMO-associated structure greatly increased the specific surface areas and the contents of the C = O and pyrrolic-N groups, which facilitated PMS activation. The structure also induced the generation of Mn5C2, which exhibited a strong adsorption towards PMS. This study provides a novel strategy for preparing catalysts by using waste biomass.

Architecture engineering of Fe/Fe2O3@MoS2 enables highly efficient tetracycline remediation via peroxymonosulfate activation: Critical roles of adsorption capacity and redox cycle regulation

Design and synthesis of high-efficiency multicomponent nanostructure for activating peroxymonosulfate (PMS) to destruct emerging antibiotics remains a daunting challenge. We report herein the simplest one-step hydrothermal construction of hierarchical Fe/Fe2O3@MoS2 architecture composed of MoS2 nanosheets integrated commercial Fe2O3 nanoparticles. The fabricated Fe/Fe2O3@MoS2 architecture can be utilized as an efficient PMS activator to destruct tetracycline hydrochloride (TCH) with a removal efficiency of 90.3 % within 40 min, outperforming Fe2O3 nanoparticles, MoS2 nanosheets analogues and many MoS2-based materials. The Fe/Fe2O3@MoS2/PMS works well under various reaction conditions, and SO4•- and 1O2 are identified as major reactive oxygen species. Thirteen intermediates towards TCH destruction are detected via four pathways, and their acute/chronic toxicity and phytotoxicity are assessed. The origins of Fe/Fe2O3@MoS2/PMS system for efficient degrading TCH are ascribed to the synergy catalysis between Fe2O3 and MoS2, which originate from: (a) the exposed Mo4+ sites on catalyst surface facilitating high-speed electron transfer from MoS2 to Fe3+ and accelerating the Fe2+ regeneration; (b) the generated Fe0 serving as an excellent electron donor to jointly promote Fe3+/Fe2+ redox cycle. This study provides a simple way to establish architecture for synergistically promoting PMS-mediated degradation.

A co-precipitation route for the preparation of eco-friendly Cu-Al-layered double hydroxides with efficient tetracycline degradation

The construction of novel efficient catalysts for the treatment of organic pollutants in the aqueous environment is essential. The lamellar-like Cu-Al layered double hydroxides (CuAl-LDHs) with various mole ratios were synthesized by a simple route of co-precipitation, and the corresponding degradation characteristic was tested for the removal of tetracycline (TC) using PMS activation. The degradation efficiency of TC over CuAl-LDHs increased up to 93% within 10 min for the Cu/Al mole ratio of 3:1 and almost not changed at a higher mole ratio. For further calcining the optimal catalyst at 300 ℃, the degradation efficiency of TC was found to be increased to 96%. Sulfuric radicals and singlet oxygen were analyzed to be the main reason for the change in degradation characteristics, which was proved by radical quenching experiments and electron paramagnetic resonance technique. The parameters including PMS concentration, catalyst dosage, and reaction temperature on the TC degradation as well as the degradation mechanism for PMS activation were elaborated. The best proportion of CuAl-LDHs owned splendid stability and catalytic activity after reusing, which showed enormous potential in practical application.