Degradation Of Refractory Pollutants Research Articles

Visible-light-driven photocatalytic for degrading tetracycline wastewater by BiOI/Bi2O3 Z-scheme heterojunction

Direct Z-scheme heterojunctions can exhibit enhanced redox capacity in redox reactions compared to conventional heterojunctions. In this study, BiOI/Bi2O3 Z-scheme heterojunctions were synthesized by a facile co-precipitation and calcination method using BiOI as a precursor, and its photocatalytic activity was investigated by degrading tetracycline antibiotics in aqueous environment. Under visible light, the degradation efficiency of tetracycline reached 80.01 % and the photocatalytic degradation rate constant reached 0.0116 min−1 when the molar ratio of Bi and I in BiOI/Bi2O3 composites was 1:1, which were 2.8 and 4.8 times higher than that of pristine BiOI (0.0041 min−1) and Bi2O3 (0.0024 min−1), respectively. The heterojunctions exposed excellent stability that maintained at 78.80 % after four cyclic tests. The ascendant photocatalytic performance can be attributed to the formation of direct Z-scheme heterojunctions, which improves the separation and transfer efficiency of the photogenerated electron-hole pairs, and ·O2- is the main active substance in the degradation process. This research provides a green and convenient method for preparing photocatalytic heterojunctions, which is conducive to promoting the development of photocatalytic degradation of refractory pollutants under visible light.

Removing multiple refractory organic pollutants in wastewater by cell bioaugmentation and genetic bioaugmentation with Rhodococcus sp. strain p52

Bioaugmentation is an appealing remediation strategy to treat refractory organic pollutants in contaminated environments. In this study, activated sludge was bioaugmented with Rhodococcus sp. strain p52 to treat synthetic wastewater containing multiple refractory organic pollutants (dibenzofuran, dibenzo-p-dioxin, and phenanthrene). Bioaugmentation of activated sludge reactors with strain p52 alleviated the adverse effects of refractory pollutants on the chemical oxygen demand and ammonia nitrogen removal capacity of the reactors and enhanced the removal of the refractory organic pollutants, especially highly refractory compound dibenzo-p-dioxin. Toxicity of the refractory pollutants to activated sludge bacteria was attenuated due to contaminant degradation by strain p52. Genetic bioaugmentation mediated by catabolic plasmid transfer from strain p52 to activated sludge bacteria and cell bioaugmentation occurred along with successful colonization and proliferation of strain p52. In addition, a potential metabolically mutualistic relationship existed between strain p52 and activated sludge bacteria for refractory pollutants degradation. Both refractory organic pollutants input and strain p52 bioaugmentation profoundly influenced the structure of the activated sludge bacterial community and drove bacterial community shifts in different directions. This study provides insights into the activities of bioaugmented bacteria and bioaugmentation technology for environmental contaminant remediation.

Heterogeneous degradation of chloramphenicol antibiotic by peroxymonosulfate activated by FeS and FeS2: Mechanism and effects of catalysts dosage and pH

Antibiotics in the environmental waters pose long-term threat to ecological safety because of their persistent and potential toxic nature. FeS and FeS2 were proved to be efficient catalysts for the activation of peroxymonosulfate (PMS) and the generation of sulfate radical generation for refractory pollutant degradation. However, their performance for antibiotic degradation has not yet been comparatively and comprehensively investigated. Herein, the FeS/PMS and FeS2/PMS systems were developed to explore chloramphenicol (CAP) degradation under equal conditions. The results show that CAP was efficiently degraded in both two systems, with a removal efficiency exceeding 90 % within 120 min using 6 mM PMS and 0.6 g/L catalysts.Acceleration in degradation rate was observed in the FeS2/PMS system when the catalyst dosage ranged from 0.1 g/L to 1.0 g/L (constant PMS concentration) with a reaction rate constant (kobs) of 2.1-fold higher than that in the FeS/PMS system. However, the kobs were comparable with the PMS concentration range (constant catalyst dosage) in the two systems, suggesting that the catalysts were the rate-limiting step in CAP degradation process. The initial pH strongly affected CAP degradation in the FeS/PMS system but had little effect on that in the FeS2/PMS system. Surface Fe2+ played a dominant role in PMS activation, and S22−/S2− facilitated Fe2+ regeneration. Further, both FeS and FeS2 had stable activity for PMS activation during long-term use. This study proves the effectiveness of FeS and FeS2 for PMS activation for antibiotic degradation and differentiates their catalytic qualities, which will provide alternative heterogeneous catalysts for practical application.

Facile synthesis of defect-rich interfacial Mo/MoO2 for efficient peroxymonosulfate activation and refractory pollutants degradation

Peroxymonosulfate-based advanced oxidation process (PMS-AOP) has shown great potential in sewage purification, and catalyst development capable of efficient PMS activation is a key while challenging element. Herein we reported a facile electro-explosive route to synthesize the oxygen vacancy (Vo)-enriched Mo/MoO2 without using chemical reagents. The detailed studies suggested that the synergy of Mo active site and Vo in the catalyst significantly boosted the activation kinetics of PMS. Evidently, the Mo site of different oxidation states contributed to chemical activation of PMS, while the Vo favored the activation of PMS and the generation of non-radical 1O2 species. As a result, the Mo/MoO2-10 h/PMS system delivered a complete removal of acid orange 7 (AO7) within 4 min, significantly exceeding the activity of Mo/PMS (16%), MoO2-H/PMS (25%) and most of other PMS-based systems. Moreover, the current system showed high potential for removal of different pollutants including antibiotics and organic dyes. Radical quenching experiments and electron paramagneticresonance (EPR) studies revealed that the 1O2 species was significant for AO7 decomposition. This work provided a novel strategy to a batch-scale synthesis of high-performance PMS activator for water remediation in practice.

Nanocatalysts for the Degradation of Refractory Pollutants

Nanocatalysts for the Degradation of Refractory Pollutants

Regulating sulfur vacancies formation on mechanochemically modified pyrite to steer non-radical molecular oxygen activation for water purification

Ubiquitous pyrite (FeS2) in the earth’s crust features strong reducing capacity, presenting a promising alternative for molecular oxygen (O2) activation to facilitate water purification, but the interfacial electron transfer efficiency was remarkably retarded due to the existed passivation layer and limited reactive sites on the surface of pristine pyrite. Herein, we proposed an effective mechanochemical approach to unlock the potential of pyrite for O2 activation and refractory pollutant degradation. Compared to the inert pristine one, the ball milling-treated pyrite (BMPs) could achieve efficient sulfamethoxazole (SMX) degradation with a rate constant of 0.23 h−1. By a combination of characterizations, batch experiments, and density function theory (DFT) calculations, a clear panorama delineated the consecutive O2 adsorption and activation processes was established. Ball milling treatment could import rich sulfur vacancies (SVs) on pyrite, which unshifted the p-band center of adjacent S for improved O2 adsorption, also narrowed the band gap of BMPs to promote the interfacial electron transfer rate for O2 activation. Singlet oxygen (1O2) was identified as the dominant reactive species for SMX degradation, such non-radical oxidation feature rendered the system with remarkable activity and environmental robustness. Our work lay a foundation for constructing robust pyrite towards stable and efficient environmental remediation applications.

Ultrafast catalytic reduction of organic pollutants using ternary zinc–copper–nickel layered double hydroxide

Water is the utmost essential commodity for the support of life process in animals. In recent decades, rapid industrialization and uncontrolled agricultural practices have led to increased level of toxic pollutants in groundwater, including organic pollutants (dyes, nitroarene compounds, antibiotics, etc.), inorganic pollutants (heavy metals, nanoparticles, etc.), and pesticides, posing a serious threat to human health and the environment. Although various technologies such as adsorption, photocatalysis, reverse osmosis, filtration, sedimentation, flocculation, and precipitation are available for the elimination of toxic pollutants from wastewater, issues such as their cost and efficacy limit their usage. Recently, catalysis has been found to be the most effective approach since it exhibits significant capability to eliminate almost all the pollutants and offers the benefit of simple design and low initial cost. In the present study, ternary zinc–copper–nickel layered double hydroxide (ZnCuNi‐LDH) synthesized using facile acid hydrolysis method was employed as an efficacious heterogeneous catalyst for the reduction of NACs (para‐nitrophenol and para‐nitroaniline) and degradation of organic azo dyes (methyl orange, amaranth, and brilliant black). ZnCuNi‐LDH exhibited superior catalytic activity for the reduction of all five model pollutants with reduction efficiency of more than 95% within a short time span of 5 min. Therefore, keeping in view the layered structure, high specific surface area, and remarkable catalytic performance, ZnCuNi‐LDH holds immense potential for the large‐scale catalytic degradation of refractory pollutants.

A Highly Synergistic Dual-Cathode Electro-Fenton Process with Self-Regulation of pH and Coating Stability for the Effective Degradation of Refractory Pollutants

As a result of issues related to pH control and the competition between H2O2 production and activation at the same sites, the applications of electro-Fenton (EF) pollutant remediation systems are limited. This work designed a synergistic dual-cathode EF system that exhibits self-adjustment of pH and stable electrode coatings. This system is based on using biomass as the active cathode material for H2O2 generation and the interaction between a stainless-steel mesh and FeOCl to reduce Fe3+ ions. The synergistic factor for this dual-cathode system was calculated to be 85.2%. Significantly, the production and activation of H2O2 in this composite system are unaffected by pH and the pH value can be adjusted between 9.67 and 3.7 without adding any acidic reagents. This process allows for the degradation of recalcitrant organic pollutants over the pH range of 3 to 9 without pre-acidification or challenges related to iron sludge and effluent chromaticity. Various organic pollutants, including antibiotics and organic dyes, can be effectively decomposed using this technology, which also exhibits good stability throughout 22 continuous trials over 1400 min. This work demonstrates a novel yet viable approach to highly efficient, inexpensive pollutant treatment with good reusability, a wide pH range and no iron leaching.

Harmonizing the cyano-group and Na to enhance selective photocatalytic O2 activation on carbon nitride for refractory pollutant degradation

Manipulating exciton dissociation and charge-carrier transfer processes to selectively generate free radicals of more robust photocatalytic oxidation capacity for mineralizing refractory pollutants remains challenging. Herein, we propose a strategy by simultaneously introducing the cyano-group and Na into graphitic carbon nitride (CN) to obtain CN-Cy-Na, which makes the charge-carrier transfer pathways the dominant process and consequently achieves the selective generation of free radicals. Briefly, the cyano-group intensifies the local charge density of CN, offering a potential well to attract the hole of exciton, which accelerates the exciton dissociation. Meanwhile, the separated electron transfers efficiently under the robust built-in electric field induced by the cyano-group and Na, and eventually accumulates in the heptazine ring of CN for the following O2 reduction due to the reinforced electron sink effect caused by Na. As a result, CN-Cy-Na exhibits 4.42 mmol L-1 h-1 productivity with 97.6% selectivity for free radicals and achieves 82.1% total organic carbon removal efficiency in the tetracycline photodegradation within 6 h. Additionally, CN-Cy-Na also shows outstanding photodegradation efficiency of refractory pollutants, including antibiotics, pesticide plastic additives, and dyes. This work presents an innovative approach to manipulating the exciton effect and enhancing charge-carrier mobility within two-dimensional photocatalysts, opening an avenue for precise control of free radical generation.

Insights into the performance of binary heterojunction photocatalysts for degradation of refractory pollutants.

The uncontrolled discharge of industry- and consumer-derived micropollutants and synthetic contaminants into freshwater bodies represents a severe threat to human health and aquatic ecosystem. Inexpensive and highly efficient wastewater treatment methods are, therefore, urgently required to eliminate such non-biodegradable, recalcitrant, and toxic organic pollutants. In this context, advanced oxidation processes, particularly heterogenous photocatalysis, have received enormous attention over the past few decades. Among the different classes of photocatalysts explored by the scientific community, heterojunction photocatalysts, in general, and binary heterojunction photocatalysts, in particular, have shown tremendous promise, attributed to their many distinct advantages. As such, the present review highlights the application of diverse array of binary heterojunction photocatalysts for eliminating water-borne contaminants. Specifically, a bibliometric analysis has been conducted to identify the ongoing research trend and future prospects of heterojunction photocatalysts. It appears that metal oxide/metal oxide-based heterojunctions have superior thermal and mechanical stability compared to other heterojunction photocatalysts. In contrast, metal oxide/non-metal semiconductor-based heterojunctions are extremely effective in pollutant degradation without significant leaching of metal ions. The review concludes by proposing novel strategic research guidelines in order to make further advances in this rapidly evolving cross-disciplinary field of topical interest.

Novel Z-scheme Nb2O5/C3N5 photocatalyst for boosted degradation of tetracycline antibiotics by visible light-assisted activation of persulfate system

Photocatalytic-assisted activation of persulfate (PDS) is regarded as a promising method for the rapid and efficient degradation of refractory pollutants in the water environment. In this study, a novel Nb2O5/C3N5 (NOCN) p-n heterojunctions composite was created by loading n-type Nb2O5 onto p-type C3N5 via an in-situ facile one-step calcination method. The NOCN/PDS system exhibited excellent performance in degrading tetracycline (TC) antibiotics under visible light and had great cyclic stability. The degradation efficiency of the coupled system reached 95 %, surpassing the pure C3N5 and PDS systems by 3.5 times and 2.4 times, respectively. The degradation rate of target pollutants was improved by the coupled system with the photocatalytic activation of PDS. The photogenerated electrons (e-) in NOCN were able to activate PDS effectively, which facilitated the creation of more reactive species. The Photoluminescence (PL) and other photoelectrochemical data demonstrated that the interfacial charge separation and photoresponsivity were remarkably enhanced in the coupled system. According to Mott-Schooky and electron spin resonance (ESR) characterization, it was confirmed that the reaction mechanism was the Z-scheme charge transfer mechanism based on p-n heterojunctions in the NOCN/PDS system. In addition, LC-MS analyses, TOC monitoring and biotoxicity analyses detected that the target pollutants were degraded to weakly bio-toxic micromolecules. In conclusion, this work provides valuable insights into the application of visible light-activated PDS technology in the degradation of organic pollutants, highlighting its potential for practical implementation.

CuFeS2 supported on dendritic mesoporous silica-titania for persulfate-assisted degradation of sulfamethoxazole under visible light

Sulfamethoxazole (SMX) is a prevalent sulfonamide antibiotic found in the environment, and it has a variety of detrimental effects on environmental sustainability and water safety. Recently, the combination of photocatalysis and sulfate radical-based advanced oxidation processes (SR-AOPs) has attracted a lot of interest as a viable technique for degradation of refractory pollutants. In this study, a visible light active CuFeS2 supported on dendritic mesoporous silica-titania (CuFeS2-DMST) photocatalyst was synthesized to improve the ability of TiO2 to activate persulfate (PS) by introducing CuFeS2 (Fe2+/Fe3+, Cu+/Cu2+ redox cycles). The CuFeS2-DMST/PS/Vis system demonstrated superior SMX degradation efficiency (88.9%, 0.0146 min−1) than TiO2 because of reduced e-/h+ recombination, excellent charge separation and mobility, and a greater surface area than TiO2. Furthermore, after four consecutive photocatalytic cycles, the system demonstrated moderate stability. From chemical quenching tests, O2●-, h+, 1O2, SO4●- and ●OH were found to be the main reactive oxidizing species. The formed intermediates during the degradation process were identified, and degradation mechanisms were proposed. This study proposes a viable technique for activating PS using a low-cost, stable, and high-surface-area TiO2-based photocatalyst, and this concept can be applied to design photocatalysts for water treatment.

Electrocatalytic degradation of p-nitrophenol on metal-free cathode: Superoxide radical (O2•−) production via molecular oxygen activation

Although metal-free electrodes in molecular oxygen-activated Fenton-like wastewater treatment technologies have been developed, the reactive oxygen species (ROS) generation mechanisms are still not sufficiently clear. As a typical example of refractory phenolic wastewater, p-nitrophenol (PNP) has been widely studied. This study demonstrated the critical role of superoxide radicals (O2•−) in PNP degradation by metal-free electrodes through electron spin resonance (ESR), ROS quenching, and density functional theory (DFT) tests. The most superior metal-free electrode exhibited a mass activity of approximately 133.5 h−1 gcatalyst−1. Experimental and theoretical studies revealed the mechanism of O2•− generation via oxygen activation, including one- and three-electron transfer pathways, and found that O2•− mainly attacked the nitro group of PNP to degrade and transform the pollutant. This study enhances the mechanistic understanding of metal-free materials in the electrochemical degradation of refractory pollutants.

A novel Co–CoAl2O4/exfoliated montmorillonite composite with improved nanoparticle dispersion for methyl orange removal via coupling peroxydisulfate

The degradation of refractory pollutants via the activation of peroxydisulfate (PDS) by Co-based nanostructures as catalysts has been gaining significant attention. However, most cobalt-based catalysts suffer from severe aggregation and metal ion leakage, resulting in a loss of activity and potential environmental threats. In this study, exfoliated montmorillonite (EMMT) loaded Co–CoAl2O4 composites were elaborately constructed through a facile coprecipitation-reduction method. The effects of the calcination temperature, the EMMT addition content, the pH of the precursor, and the reduction temperature on the microstructure of the Co–CoAl2O4/EMMT composites were investigated, and the optimum synthesis conditions were determined. In the optimal sample, well-crystallized CoAl2O4 nanoparticles were uniformly deposited onto the EMMT nanosheets with a considerably large specific surface area, while ultrafine metallic Co nanoparticles were homogeneously immobilized on the CoAl2O4 surface. This sample exhibited a superior activity (90% within 70 min) and reusability during methyl orange (MO) degradation. In the catalytic reaction, the superior adsorption property of EMMT facilitated the rapid transfer of MO molecules to the catalytically active sites. Moreover, CoAl2O4 acted as a transition layer which provided a cobalt source for the subsequent reduction process and regulated the growth of metallic Co nanoparticles, which increased the number of active sites for catalysis. Simultaneously, the metallic Co can not only activate PDS by being an electron donor, but also initiate the formation of Co-based redox pairs. This study offers new insights into the synthesis of efficient and cost-effective supported Co-based catalysts.

Efficient degradation of refractory pollutant boosted by combining heterogeneous electro-Fenton on the hydrophobic modified gas diffusion electrode with anodic oxidation

To boost refractory pollutant removal over a broad pH range, we here proposed an integrated electrocatalytic process combining electrochemical anodic oxidation (AO) with cathodic electro-Fenton (EF) based on a hydrophobic modified gas diffusion electrode and heterogeneous Fenton catalyst of FeOCl. Total organic carbon (TOC) removal of refractory levofloxacin by EF + AO process was 85% in 120 min under the applied potential of −0.6 V and pH ∼6.7, obviously higher than that of only AO (22%) or EF (62%) process. Significantly, EF+AO process was demonstrated to be efficient and stable for actual wastewater treatment that chemical oxygen demand (COD) value of refinery wastewater after EF + AO treatment was steadily met the discharge standard (GB 18918–2002) for sewage treatment plants in China (I-A: COD < 50 mg/L) during 100 h of consecutive runs. Our results provide new insights into developing an energy-efficient electrocatalytic technology for enhancing refractory pollutant removal.

Fabrication of lanthanum-mediated carbon quantum dots for the fluorescent detection of aniline and enhancement in photocatalytic degradation efficiency of zirconium oxide nanoparticles

A unique and efficient fluorescent sensor was developed by doping carbon quantum dots (CQDs) with La(III) ions by microwave treatment. The La-CQDs exhibit an average particle size of 4.8 nm, a quantum yield of 16 % and blue fluorescence emission when excited at 360 nm. Furthermore, the La-CQDs were successfully incorporated into zirconium oxide nanoparticles (La-CQD-ZrO2) and designed as a superior photocatalyst for the degradation of refractory pollutants. Both the sensor and photocatalyst were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman analysis, ultraviolet–visible (UV–Vis) spectroscopy, Photoluminescence (PL) spectroscopy, zeta potential analysis, dynamic light scattering (DLS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry analysis. As a PL-based sensor, the La-CQDs displayed outstanding selectivity towards toxic chemical aniline with a limit of detection (LOD) of 10 nM within the linear range 0–2 μM. The excellent results obtained in real sample analysis promise the use of La-CQDs as an aniline sensor in industrial-level applications. The photocatalytic performance of La-CQD-ZrO2 was superior to that of pure ZrO2 and CQD-ZrO2 with more than 90 % degradation efficiency towards rhodamine B (Rh B), sunset yellow (SY), methyl orange (MO), 2,4-dichloro phenoxy acetic acid (2,4-D), and cefalexin. The synthesized composite showed excellent promise as a quick and affordable solution for removing industrial dye from wastewater.

Caffeic acid accelerated the Fe(II) reinvention in Fe(III)/PMS system for bisphenol A degradation: Oxidation intermediates and inherent mechanism

Fe(II)-catalyzed PMS process was widely used in the degradation of refractory pollutants in wastewater, while its performance was restricted by the slow regeneration efficiency of Fe(II). Herein, caffeic acid (CFA), a representative of hydroxycinnamic acids, was introduced into Fe(III)/PMS system to accelerate the transformation of Fe(III) to Fe(II) and promote the removal of bisphenol A (BPA). Under optimum condition of 0.1 mM CFA, 0.05 mM Fe(III), and 0.5 mM PMS, almost complete removal of BPA can be achieved within 20 min, which was roughly 6.2 times higher than that in Fe(III)/PMS system. As the addition of CFA into Fe(III)/PMS system, pH application range was widened from acidic to alkaline conditions. The reduction and chelation of CFA expedited the Fe(III)/Fe(II) cycle by forming CFA-Fe chelate, thereby facilitating the PMS activation. Based on LC-MS analysis and DFT calculation, the intermediate products of CFA were found to play a decisive role in boosting the regeneration of Fe(II), and the toxicity of these intermediates towards organisms was evaluated by ECOSAR. The alcohol-scavenging and chemical probe tests certified that hydroxyl radical (•OH), sulfate radical (SO4•-), and Fe(IV) coexisted in Fe(III)/CFA/PMS system, and the second-order reaction rate constants of •OH and SO4•- reacted with CFA were calculated to be 3.16✕109 and 2.30✕1010 M−1 s−1, respectively. Two major degradation pathways of BPA, •OH addition and SO4•- induced hydroxylation reaction, were proposed. This work presented a novel green phenolic compound that expedited the Fe(II)-catalyzed PMS activation process for the treatment of organic contaminants.

High-efficiency refractory organic pollutants removal boosted by combining heterogeneous electro-Fenton with electrochemical anodic oxidation over a broad pH range

Electrochemical anodic oxidation (AO) is a green and efficient treatment process for refractory pollutants degradation. The cathode in AO process generally serves as the counter electrode, and does not contribute significantly for pollutants removal. The heterogeneous electro-Fenton (EF) process uses the bifunctional catalytic material as cathode to produce H2O2 via 2e- oxygen reduction reaction and activate H2O2 decomposition to generate •OH for degrading pollutants. Herein, we investigated an integrated electrocatalytic process between heterogeneous EF and AO (EF+AO) to enhance refractory pollutants removal over a broad pH range without the production of iron-containing sludge. Total organic carbon removal of phenol by EF+AO was 98.2 % in 180 min under pH ∼5.9 and the applied current density of 1.0 mA cm−2, obviously higher than that of only EF (48.8 %) or AO (56.9 %). Significantly, EF+AO process can efficiently treat the actual coking wastewater that the chemical oxygen demand (COD) value gradually decreased from 312.3 mg L−1 to 47.8 mg L−1 with the low specific energy consumption of 14.0 – 25.7 kWh·(kg COD)−1. This process delivered excellent long-term durability in flow mode, retaining efficient degradation performance for phenol during 100 h of consecutive runs. Our results provide new insights into developing an energy-efficient electrocatalytic process for pollutants removal.

Promoting photocatalytic performance of TiO2 nanomaterials by structural and electronic modulation

Titanium dioxide (TiO2) possessing excellent visible light response and high separation efficiency of charges without sacrificing its redox ability predicts significant opportunities for an efficient solar energy conversion system. Herein, novel TiO2 nanomaterials with upward-shifted conduction bands and tunable crystal phases were prepared by a lysine doping method. Lysine-doped TiO2 (LDT) showed enhanced reduction potential, efficient charge separation, and improved visible-light absorption. As photocatalysts, LDTs exhibited boosting photocatalytic ability both in light-to-chemical conversion and in refractory pollutant degradation. They can convert visible light to chemical energy and store in nicotinamide adenine dinucleotide (NADH) independent of any electron mediator with a yield of ca. 90%, far beyond that of the undoped TiO2 (13%). As for the refractory pollutant removal, compared to the negligible effect over the undoped TiO2 and commercial titania P25, lysine doping in TiO2 performs as a reaction switch to enable the photodegradation of 4-chlorophenol (4-CP) to proceed. More than 80% of 4-CP was removed with a kinetic constant of 0.8801 h−1. This work presents a distinctive strategy to precisely control the structure of TiO2 nanomaterials and provides a fresh insight into the structural and electronic modulation to promote their photocatalytic performance.

Insights into degradation of pharmaceutical pollutant atenolol via electrochemical advanced oxidation processes with modified Ti4O7 electrode: Efficiency, stability and mechanism

A novel active Ce-doped Ti4O7 (Ti/Ti4O7–Ce) electrode was prepared and evaluated for improvement of the refractory pollutants degradation efficiency in Electrochemical advanced oxidation processes (EAOPs). The results showed that the addition of Ce in Ti/Ti4O7 electrode leading to great impact on •OH generation rate and electrode stability compared to pristine Ti/Ti4O7 electrode. Ti/Ti4O7–Ce electrode presented efficient oxidation capacity for pharmaceutical pollutant atenolol (ATL) in EAOPs, which could be attributed to the improvement of indirect oxidation mediated by electro-generated •OH, as the amount of •OH production was 16.5% higher than that in Ti/Ti4O7 within 120 min. The operational conditions greatly influenced the ATL degradation. The degradation efficiency of ATL increased as the current density, the degradation efficiency reached 100% under pH 4, but it just removed 81% of ATL under pH 10 after 120 min treatment. Results also suggested that the inhibiting effect from the ATL degradation was mostly associated with the decreased oxidation capacity induced by water hardness and natural organic matter (NOM). It displayed a satisfactory durability after 40 cycles of experimental detections in this research. The results of study suggested that Ti/Ti4O7–Ce was a promising electrode for the efficient degradation of PPCPs-polluted wastewater and provided constructive suggestion for the refractory pollutants of EAOPs.