Peroxymonosulfate enhanced antibiotic removal and synchronous electricity generation in a photocatalytic fuel cell

Advanced nanofibrous photoanode for simultaneous pharmaceutical degradation and electricity generation in a photocatalytic fuel cell

Photocatalytic fuel cell technology (PFC) has emerged as an efficient solution to address the energy crisis and environmental pollution. The development of efficient, reliable, and cost-effective photoanodes remains an urgent challenge for large-scale implementation. Herein, a novel PFC system with a nanofibrous photoanode was first fabricated for simultaneous pharmaceutical wastewater treatment and electricity generation. The TiO2/1.5 %CNTs nanofibrous photoanode achieved a Voc of 0.59 V, a Jsc of 31.73 μA/cm2, and a Pmax of 3.56 μW/cm2, which was superior to the TiO2 nanofibrous photoanode. The main intermediates of phenazopyridine degradation in the PFC process were identified using LC-MS analysis. Furthermore, phytotoxicity analysis indicated that the toxicity of wastewater was eliminated after the PFC process. The results of the economic and stability analyses confirm that the TiO2/1.5 %CNTs nanofibrous photoanode exhibits low total cost, energy consumption, and long-term stability. Therefore, the nanofibrous photoanode is introduced as a promising, cost-effective, and environmentally friendly photoanode for simultaneous wastewater treatment and energy production.

Integrated Wastewater Remediation and Energy Production: Microfluidic Photocatalytic Fuel Cells Enabled by Dye Pollutants

Directly degrading the dyes in the wastewater is a missed opportunity. Herein, we propose a solution employing a microfluidic chip to construct a photocatalytic fuel cell (PFC) system, which can efficiently degrade tetracycline while generating electricity simultaneously under visible-light irradiation. This approach utilizes the photogenerated electrons from the dye Rhodamine B (RhB), which are effectively transferred through a gold layer to activate persulfate in water, leading to enhanced tetracycline degradation. Experimental results reveal that within one hour of reaction duration, the degradation efficiency of tetracycline within the PFC system was doubled. At a persulfate (PS) concentration of 2 mM, the system's open-circuit voltage and short-circuit photocurrent density reached 0.26 V and 0.00239 mA·cm-2 respectively, both exceeding the values detected at 0.5 mM PS. Additionally, the system's power density was triple that at 0.5 mM PS. Notably, when the PS concentration in the system was elevated from 0.5 mM to 2 mM, the degradation efficiency of tetracycline witnessed a significant boost from 35.16% to 60.78%. This approach proffers a novel tactic for harnessing dye waste via microfluidic devices. The PFC system accomplishes not only the degradation of dyes and antibiotics but also the generation of electrical energy, substantially enhancing the energy utilization efficiency.

Integrating detection and degradation of bisphenol A by photocatalytic fuel cell-driven photoelectrochemical sensor

To ensure food safety and environmental protection, it is crucial to rapidly identify and remove bisphenol A (BPA), a plasticizer commonly used in the inner lining of food containers and beverage packaging. Here, a photocatalytic fuel cell (PFC)-integrated self-powered photoelectrochemical (PEC) sensor is constructed. Unlike conventional single PEC or PFC sensors, this PFC-integrated PEC sensor relies on not only the difference in Fermi energy levels between photoanode and photocathode but also charge accumulation resulted from the oxidation of BPA by photogenerated holes. Consequently, this sensor achieved a remarkable maximum output power (Pmax) of 8.58 μW cm-2, as well as a high sensitivity, wide linear detection range (0.1-200 μM), low detection limit (0.05 μM), great stability, reproducibility, and real sample detection capability. This work integrates PFC and PEC technologies successfully for the rapid identification and efficient removal of BPA.

Three dimensional nickel foam carried sea urchin-like copper-cobalt-cerium cathode for enhanced tetracycline wastewater purification in photocatalytic fuel cell

Photocatalytic fuel cells (PFCs) regarded as a potential sustainable technique, have been broadly reported. In this work, the carbon quantum dot-loaded TiO2 photoanode and sea urchin-like CuCoCe ternary metal oxide cathode materials are successfully synthesized and used to construct PFC systems for efficient tetracycline (TC) degradation (45 mg/L) and simultaneous electricity generation. The results demonstrate that the CQDs-modified TiO2 photoanode has improved absorption intensity in both the UV and visible regions, and the photocurrent density at 1.23 V vs RHE reached 1.31 mA cm-2, which is 1.3 times higher than that of the original TiO2 photoanode. The established PFC system achieves the highest removal ratio of 96.9 % for TC in 60 min with a maximum power density of 0.77 mW cm-2. The PFC system can operate efficiently over a wide pH range (3.0-9.0). Furthermore, quenching experiments and ESR spectra show that the main reactive oxygen species in the degradation process are •O2-, 1O2 and •OH. This study provides meaningful way to develop multiple metal oxides as cathode of PFC system for efficient organic pollutant degradation and energy recovery.

Sustainable degradation of pollutants, generation of electricity and hydrogen evolution via photocatalytic fuel cells: An Inclusive Review

Environmental pollution and energy crisis have recently become one of the major global concerns. Insincere discharge of massive amount of organic and inorganic wastes into the aqueous bodies causes serious impact on our environment. However, these organic substances are significant sources of carbon and energy that could be sustainably utilized rather than being discarded. Photocatalytic fuel cell (PFC) is a smart and novel energy conversion device that has the ability to achieve dual benefits: degrading the organic contaminants and simultaneously generating electricity, thereby helping in environmental remediation. This article presents a detailed study of the recent advancements in the development of PFC systems and focuses on the fundamental working principles of PFCs. The degradation of various common organic and inorganic contaminants including dyes and antibiotics with simultaneous power generation and hydrogen evolution has been outlined. The impact of various operational factors on the PFC activity has also been briefly discussed. Moreover, it provides an overview of the design guidelines of the different PFC systems that has been developed recently. It also includes a mention of the materials employed for the construction of the photo electrodes and highlights the major limitations and relevant research scopes that are anticipated to be of interest in the days to come. The review is intended to serve as a handy resource for researchers and budding scientists opting to work in this area of PFC devices.

One stone, two birds: A Cu-S cluster as a laccase-mimicking nanozyme and sulfite activator for phenol remediation in marine environments

Phenols are infamous pollutants in marine environments and present a grave danger to human health, which makes their efficient detection and removal serious issues. Colorimetry is a simple method for detecting phenols in water because phenols can be oxidized by natural laccase and generate a brown product. However, high cost and poor stability impede the wide-spread implementation of natural laccase in phenol detection. To reverse this adverse situation, a nanoscale Cu-S cluster, Cu₄(MPPM)₄ (Cu₄S₄, MPPM = 2-mercapto-5-n-propylpyrimidine), is synthesized. As a stable and inexpensive nanozyme, Cu₄S₄ shows excellent laccase-mimicking activity and prompts the oxidation of phenols. This characteristic makes Cu₄S₄ a perfect option for phenol detection with colorimetry. In addition, Cu₄S₄ also exhibits sulfite activation properties. It can degrade phenols and other pollutants with advanced oxidation processes (AOPs). Theoretical calculations show good laccase-mimicking and sulfite activation properties originating from appropriate interactions between Cu₄S₄ and substrates. We anticipate that the phenol detection and degradation characteristics of Cu₄S₄ make it a promising material to be used for practical phenol remediation in water environments.

Tetracycline hydrochloride degradation by activation of peroxymonosulfate with lanthanum copper Ruddlesden-Popper perovskite oxide: Performance and mechanism

ABO₃-type perovskite oxides have been regarded as a kind of potential catalyst for peroxymonosulfate (PMS) activation. But some limitations such as specific pH conditions and coexisting ion interference restrict its practical application. Herein, a lanthanum copper Ruddlesden-Popper perovskite oxide (La₂CuO₄) was successfully synthesized through the sol-gel process and applied in the activation of PMS. And for the first time the La₂CuO₄/PMS system was used for tetracycline hydrochloride (TC-HCl) degradation. Results showed that La₂CuO₄ was a potential PMS activation catalyst in the removal of antibiotics. At optimized condition (0.2 g/L catalysts, 1 mM PMS, pH₀ 6.9), 96.05% of TC-HCl was removed in 30 min. In experiments of debugging control conditions, over a wide pH range of 3-11, more than 90% of TC-HCl can be removed. In the natural water treatment process, TC-HCl removal rates of about 84.2% and 70.3% were obtained in tap water and River water, respectively. According to the reusability and stability tests and the results of FTIR and XPS analysis, La₂CuO₄ had high structural and chemical stability. Electron paramagnetic resonance (EPR) suggested that the active species including ·OH, SO₄^-· and ¹O₂ were detected in degradation reaction. Finally, reasonable reaction mechanisms and possible degradation pathways of TC-HCl were proposed. These results indicate that La₂CuO₄ can act as a potential catalyst for PMS activation to degrade TC-HCl in water.

Valorization of ball-milled waste red mud into heterogeneous catalyst as effective peroxymonosulfate activator for tetracycline hydrochloride degradation

Red mud (RM), a kind of iron-rich industrial waste produced in the alumina production process, can be utilized as a potential iron-based material for the removal of refractory organic pollutants from wastewater in advanced oxidation processes (AOPs). In this work, high-iron RM (rich in iron) was activated in a ball mill and applied as an effective activator of peroxymonosulfate (PMS) for tetracycline hydrochloride (TC-HCl) degradation. Compared with that of unmilled RM (69.7%), the TC-HCl decomposition ratios of ball-milled RM (BM-RM) (72.2%-92.0%) were all improved in the presence of PMS. Systematic characterization suggested that ball milling could optimize the physicochemical properties of RM, such as increased surface area, increased oxygen vacancies, enhanced electrical conductivity, and increased exposure of Fe(II) sites, all of which could effectively improve RM for PMS activation to degrade TC-HCl. The quenching experiments and electron paramagnetic resonance technique revealed that ¹O₂ and SO₄·^- contributed dominantly to the TC-HCl degradation. Ultra performance liquid chromatography mass spectrometry analysis combined with density functional theory calculation revealed that the degradation pathways of TC-HCl were driven by hydroxylation, N-demethylation and dehydration in BM-RM/PMS system. Based on quantitative structure-activity relationship prediction using the Toxicity Estimation Software Tool software, the toxicity of almost all intermediates was significantly reduced. An obvious inhibition effect on TC-HCl was occurred in the presence of Cl^-, whereas the presences of NO₃^- and SO₄^2- had little effect. However, HCO₃^- improved TC-HCl removal efficiency. BM-RM had a wide working pH range (pH = 3-11) and showed good stability and reusability in use. Overall, this work not only offers a simple and promising approach to improve the catalytic activity of RM, but also opens new insights into the ball-milled RM as an effective PMS activator for wastewater treatment.

Synergy of photocatalysis and fuel cells: A chronological review on efficient designs, potential materials and emerging applications

The rising demand of energy and lack of clean water are two major concerns of modern world. Renewable energy sources are the only way out in order to provide energy in a sustainable manner for the ever-increasing demands of the society. A renewable energy source which can also provide clean water will be of immense interest and that is where Photocatalytic Fuel Cells (PFCs) exactly fit in. PFCs hold the ability to produce electric power with simultaneous photocatalytic degradation of pollutants on exposure to light. Different strategies, including conventional Photoelectrochemical cell design, have been technically upgraded to exploit the advantage of PFCs and to widen their applicability. Parallel to the research on design, researchers have put an immense effort into developing materials/composites for electrodes and their unique properties. The efficient strategies and potential materials have opened up a new horizon of applications for PFCs. Recent research reports reveal this persistently broadening arena which includes hydrogen and hydrogen peroxide generation, carbon dioxide and heavy metal reduction and even sensor applications. The review reported here consolidates all the aspects of various design strategies, materials and applications of PFCs. The review provides an overall understanding of PFC systems, which possess the potential to be a marvellous renewable source of energy with a handful of simultaneous applications. The review is a read to the scientific community and early researchers interested in working on PFC systems.

UVA-irradiated dual photoanodes and dual cathodes photocatalytic fuel cell: mechanisms and Reactive Red 120 degradation pathways

To enhance dye removal and energy recovery efficiencies in single-pair electrode photocatalytic fuel cell (PFC-AC), dual cathodes PFC (PFC-ACC) and dual photoanodes PFC (PFC-AAC) were established. Results revealed that PFC-AAC yielded the highest decolorization rate (1.44 h-1) due to the promotion of active species such as superoxide radical (•O2-) and hydroxyl radical (•OH) when the number of photoanode was doubled. The results from scavenging test and UV-Vis spectrophotometry disclosed that •OH was the primary active species in dye degradation of PFC. Additionally, PFC-AAC also exhibited the highest power output (17.99 μW) but the experimental power output was much lower than the theoretical power output (28.24 μW) due to the strong competition of electron donors of doubled photoanodes to electron acceptors at the single cathode and its high internal resistance. Besides, it was found that the increments of dye volume and initial dye concentration decreased the decolorization rate but increased the power output due to the higher amount of sacrificial agents presented in PFC. Based on the abovementioned findings and the respective dye intermediate products identified from gas chromatography-mass spectrometry (GC-MS), the possible degradation pathway of RR120 was scrutinized and proposed.

Efficient degradation of antibiotics over Co(II)-doped Bi2MoO6 nanohybrid via the synergy of peroxymonosulfate activation and photocatalytic reaction under visible irradiation

Developing efficient photocatalysts based on the peroxymonosulfate (PMS) activation for effective degradation of threatening antibiotic contamination under visible light is still a challenging subject. Herein, a Co-doped Bi₂MoO₆ (CBMO) spherical crystals were synthesized via a facile hydrothermal method and used to degrade artificial antibiotic wastewater via PMS activation under visible light. The obtained 3 wt% Co-doped B₂MoO₆ (3CBMO) can effectively remove 98.95% of norfloxacin (NOF) within 40 min, 100% of tetracycline (TC) and metronidazole (MNZ) within 30 min. Compared with the contrasting catalysts, the superior catalytic activity of 3CBMO was attributed to the synergistic effect of photocatalytic and Co(II) activated PMS degradations. Quenching tests in combination with EPR measurements revealed that the hole (h⁺), sulfate (SO₄^-•) and hydroxyl (•OH) were the primary radicals all contributed to NOF degradation. The influences of initial concentration, catalyst dosage, PMS dosage and various interfering ions (NO₃^-, Cl^-, SO₄^2-, and HCO₃^-) on the degradation efficiency of NOF were systematically examined. Furthermore, possible degradation pathways of NOF were proposed by LC-MS. This novel 3CBMO catalyst might be a promising candidate for degradation of the main sources of antibiotic contamination in pharmaceutical wastewater.

Kinetic and mechanistic insights into the degradation of clofibric acid in saline wastewater by Co2+/PMS process: a modeling and theoretical study

Recently, the degradation of non-chlorinated organic pollutants in saline pharmaceutical wastewater by SO₄˙⁻-based advanced oxidation processes (AOPs) has received widespread attention. However, little is known about the oxidation of chlorinated compounds in SO₄˙⁻-based AOPs. This study chose clofibric acid (CA) as a chlorinated pollutant model; the oxidation kinetics and mechanistic pathway were explored in the Co²⁺/peroxymonosulfate (PMS) system. Notably, a high removal efficiency (81.0%) but low mineralization rate (9.15%) of CA within 120 min were observed at pH 3.0 during Co²⁺/PMS treatment. Exogenic Cl⁻ had a dual effect (inhibitory then promoting) on CA degradation. Several undesirable chlorinated by-products were formed in the Co²⁺/PMS system. This demonstrated endogenic chlorine and exogenic Cl⁻ both reacted with SO₄˙⁻ to generate chlorine radicals, which participated in the dechlorination and rechlorination of CA and its by-products. Furthermore, SO₄˙⁻ was the dominant species responsible for CA degradation at low Cl⁻ concentrations (≤1 mM), whereas Cl₂˙⁻ was the predominant radical at [Cl⁻]₀ > 1 mM. A possible degradation pathway of CA was proposed. Our findings suggested that chlorinated compounds in highly saline pharmaceutical wastewater will be more resistant and deserve more attention.

Recently, the degradation of non-chlorinated organic pollutants in saline pharmaceutical wastewater by SO₄˙⁻-based advanced oxidation processes (AOPs) has received widespread attention.

Peroxymonosulfate Activation by Photoelectroactive Nanohybrid Filter towards Effective Micropollutant Decontamination

Herein, we report and demonstrate a photoelectrochemical filtration system that enables the effective decontamination of micropollutants from water. The key to this system was a photoelectric–active nanohybrid filter consisting of a carbon nanotube (CNT) and MIL–101(Fe). Various advanced characterization techniques were employed to obtain detailed information on the microstructure, morphology, and defect states of the nanohybrid filter. The results suggest that both radical and nonradical pathways collectively contributed to the degradation of antibiotic tetracycline, a model refractory micropollutant. The underlying working mechanism was proposed based on solid experimental evidences. This study provides new insights into the effective removal of micropollutants from water by integrating state–of–the–art advanced oxidation and microfiltration techniques.

Peroxymonosulfate activated by photocatalytic fuel cell with g-C3N4/BiOI/Ti photoanode to enhance rhodamine B degradation and electricity generation

The development of traditional photocatalytic fuel cell (PFC) is severely hindered by poor visible-light response and limited reaction space. In this study, a visible-light responsive PFC with g-C₃N₄/BiOI/Ti photoanode was proposed and applied to activate peroxymonosulfate (PMS) to degrade rhodamine B. The degradation rate, maximum power density and maximum photocurrent density of the PMS/PFC system were respectively 95.39%, 103.87 μW cm^-2 and 0.62 mA cm^-2, which was respectively 1.28, 2.18, and 1.98 times that of PFC. The excellent performance is attributed to the production of more reactive oxygen species and the extension of the reaction space range after the activation of PMS. The activation pathway of PMS and charge transfer pathway of the photoanode were discussed in detail, and it was proposed that PMS was activated by Z-scheme heterojunction g-C₃N₄/BiOI/Ti photoanode.

Hematite/selenium disulfide hybrid catalyst for enhanced Fe(III)/Fe(II) redox cycling in advanced oxidation processes

Regeneration of Fe(II) is a key issue for heterogeneous advanced oxidation processes (AOPs) using iron-based catalysts. Herein, a hybrid catalyst was developed from α-Fe₂O₃ and SeS₂ to enhance the Fe(III)/Fe(II) redox cycling in both hydrogen peroxide (H₂O₂) system and persulfate (PS) system. The regeneration of Fe(II) was evidenced by the increased Fe(II)/Fe(III) ratio in the used catalyst (205.8% in the H₂O₂ system or 125.4% in the PS system), compared to 68.4% in the fresh hybrid catalyst Fe/Se-3. Methyl orange was used as a model pollutant to evaluate the degradation performance of the hybrid catalyst. Owing to the promotion of Fe(II) regeneration, Fe/Se-3 achieved a pollutant removal efficiency of 100.0% in 12 min in both systems, significantly higher than that with pure α-Fe₂O₃ (33.9 ± 3.6% in the H₂O₂ system or 30.7 ± 2.8% in the PS system). The dominant active species were identified as hydroxyl radicals in the H₂O₂ system and sulfate radicals in the PS system. In the proposed mechanism, soluble and surface-bound Fe species are provided by α-Fe₂O₃ to activate H₂O₂ or PS to radicals, and SeS₂ participates in the reactions via Se(IV) reducing Fe(III) to Fe(II) and S atoms being released through protonation to expose more active Se sites.

Novel NbCo-MOF as an advanced peroxymonosulfate catalyst for organic pollutants removal: Growth, performance and mechanism study

Multivariate metal-organic frameworks (MTV-MOFs) are expected as catalyst to apply to the advanced oxidation processes (AOPs) based on sulfate radical (SO₄·^-) to treat wastewater containing organic pollutants. Mixing metals de novo method was combined with stringent solvothermal conditions to synthesize macaroon-like NbCo-MOF catalyst. NbCo-MOF catalyst prepared with different atom ratios and growth time presented various morphology, structure, performance, and distinctive MTV-MOFs growth law which were confirmed by SEM, TEM, EDS, XRD, FTIR, raman spectra and UV-vis spectra. Besides, optimum peroxymonosulfate (PMS) catalytic activation conditions were studied. Furthermore, the effects of anions (Cl^-, NO₃^-, HCO₃^-, and C₂O₄^2-) on NbCo-MOF catalytic activation were explored which were proved very limited. Particularly, the Co²⁺/Co³⁺ cycle combining with the Nb⁴⁺/Nb⁵⁺ cycle for PMS activation were verified by XPS. EPR and quenching experiment results indicated exists non-radical pathway (¹O₂), but radical pathways are dominant (SO₄·^- O₂·^-, and ·OH). Moreover, the TC removal rate exhibited no significant reduce after three times run. Furthermore, NbCo-MOF exhibited excellent decomposing ability towards methylene blue, tylosin tartrate, rhodamine B, and tetracycline with the removal rate reaching to 100%, 98.4%, 99.7%, and 99.7% in 30 min respectively and also maintained good performance in actual water environment.

Enhanced bezafibrate degradation and power generation via the simultaneous PMS activation in visible light photocatalytic fuel cell

A collaborative system including peroxymonosulfate (PMS) activation in a photocatalytic fuel cell (PFC) with an BiOI/TiO₂ nanotube arrays p-n type heterojunction as photoanode under visible light (PFC(BiOI/TNA)/PMS/vis system) was established. Xenon lamp was used as the light source of visible light. A 4.6 times higher pseudo-first-order bezafibrate (BZF) degradation rate constant was achieved in this system compared with the single PFC(BiOI/TNA)/vis system. The radical quenching experiments revealed that the contribution of reactive oxidative species (ROS) followed the order of ¹O₂ ≈ h⁺ >> •OH > SO₄^•- >>O₂^•-. The EPR tests demonstrated that PMS addition enlarged the formation of ¹O₂, •OH and SO₄^•-, but suppressed O₂^•- yield. Interestingly, ¹O₂ was further proved to dominantly originated from the priority reaction between positive photoinduced holes (h⁺) and negatively charged PMS. Besides, N₂-purging tests and density functional theory calculation indicated that PMS probably reacted with residual photoinduced electron (e^-) on the more negative conduction band (CB) of BiOI to form •OH and SO₄^•-, but competed with dissolved oxygen. Other e^- transferred to the less negative CB of TNA through p-n junction will efficiently move to cathode through the external circuit. The greatly promoted power generation of PFC system was observed after PMS addition due to extra h⁺ consumption and efficient e^- separation and transfer. Besides, three possible pathways for BZF degradation were proposed including hydroxylation, fibrate chain substituent and amino bond fracture. This study can provide new insights into the mechanisms of PMS assisted photocatalysis and accompanying energy recovery.

Enhanced sludge dewaterability by Fe-rich biochar activating hydrogen peroxide: Co-hydrothermal red mud and reed straw

This study proposed Fe-rich biochar (RMRS-BC) produced by the co-hydrothermal treatment of red mud and reed straw, industrial waste and agricultural waste, as a novel sludge conditioner. It had been proven that heterogeneous and homogeneous Fenton reactions occurred during the sludge conditioning process, in which RMRS-BC activated H₂O₂ to improve sludge dewaterability. Results demonstrated that the optimal condition was 7.5 wt% dry solids (DS) of RMRS-BC at a mass ratio of 1:1 combined with H₂O₂. The corresponding water content of sludge cakes and the capillary suction time reduction efficiency were 57.88 wt% and 69.76%, respectively. The Fe₃O₄ supported in the RMRS-BC structure was used as a catalyst to produce heterogeneous reaction, and the Fe²⁺ leached from the RMRS-BC after acidification happened homogeneous reaction. Double Fenton reaction in sludge conditioning enhanced the production efficiency of ·OH, the sludge flocs were dispersed into smaller particles, more bound water from the extracellular polymeric substances (EPS) was released, and sludge dewaterability performance was improved. Another main mechanism for enhancing dewaterability was to use RMRS-BC as a skeleton builder to reduce the compressibility of sludge cakes and facilitated free water to flow out. In summary, the Fenton oxidation method activated by RMRS-BC is feasible in improving sludge dewatering.

Complete solar-driven dual-photoelectrode fuel cell for water purification and power generation in the presence of peroxymonosulfate

This study reports the development of complete solar-driven dual-photoelectrode fuel cell (PFC) based on WO₃ photoanode and Cu₂O photocathode with peroxymonosulfate (PMS) serving as cathodic electron acceptor. As indicated by photoelectrochemical measurements, the PMS was able to improve thermodynamic properties of photocathode, achieving an increased open circuit potential from 0.42 V to 0.65 V vs standard hydrogen electrode (SHE). Under simulated sunlight irradiation (~100 mW cm^-2), the maximum power density of 0.12 mW cm^-2 could be obtained at current density of 0.34 mA cm^-2, which was 8.57 times of that produced by PFC without PMS (0.014 mW cm^-2). Correspondingly, adding PMS (1.0 mM) increased overall removal efficiency of 4-chlorophenol (4-CP) from 39.8% to 96.8%, accounting for the first-order kinetic constant (k=0.056 min^-1) being 6.67 times of that in the absence of PMS (k=0.0084 min^-1). Radical quenching and electron spin-resonance (ESR) results suggested the contribution of free radicals (•OH and SO₄^•-) and non-radical pathway associated with direct activation of PMS by Cu₂O photocathode. Fourier transformed infrared (FTIR) analysis confirmed the strong non-radical interaction between Cu₂O photocathode and PMS, resulting in 4-CP removal via activation of PMS by surface complex on Cu₂O. The proof-in-concept complete solar-driven dual-photoelectrode fuel cell may offer an effective manner to realize water purification and power generation, making wastewater treatment more economical and more sustainable.

The removal of tetracycline with biogenic CeO2 nanoparticles in combination with US/PMS process from aqueous solutions: kinetics and mechanism

Antibiotics have received great attention because of their abuse and potential hazards to the human health and environment. In the current work, peroxymonosulfate (PMS) was added to a cerium oxide (CeO₂)/ultrasonic (US) system for tetracycline (TC) degradation. CeO₂ nanoparticles (NPs) were synthesized by a simple and cost-effective method using Stevia rebaudiana leaf extract and cerium nitrate as precursors. The as-synthesized CeO₂ NPs were characterized by X-ray diffraction, field emission scanning electron microscopy, and Fourier-transform infrared spectroscopy analysis. The effects of catalyst dosage, PMS concentration, US power, initial antibiotic concentration, and pH on TC removal were investigated. The results confirmed the formation of CeO₂ NPs with a fluorite structure, spherical shape, and average particle size of 29 nm. The removal efficiency of TC was 92.6% in the optimum oxidation conditions ([TC] = 15 mg/L, [PMS] = 50 mM, [CeO₂] = 0.6 g/L, pH = 6, and US = 70 W) and followed the zero-order kinetics. Experiment scavenger demonstrated both sulfate and hydroxyl radicals (SO₄^•-, ^•OH) were responsible for degrading antibiotics. Biogenic CeO₂ NPs and ultrasound waves-activated PMS is a promising technology for water pollution caused by contaminants such as pharmaceuticals.

Visible-light harvesting innovative W6+/Yb3+/TiO2 materials as a green methodology photocatalyst for the photodegradation of pharmaceutical pollutants

In this work, we report on the synthesis of a new-age reusable visible-light photocatalyst using a heterojunction nanocomposite of W⁶⁺/Yb³⁺ on a mixed-phase mesoporous network of monolithic TiO₂. The structural properties of the monolithic photocatalysts are characterized using p-XRD, SEM-EDAX, TEM-SAED, XPS, PLS, UV-Vis-DRS, FT-IR, micro-Raman, TG-DTA, and N₂ isotherm analysis. The electron microscopic analysis reveals a mesoporous network of ordered worm-like monolithic design, with a polycrystalline mixed-phase (anatase/rutile) TiO₂ composite, as indicated by diffraction studies. The UV-Vis-DRS analysis reveals a redshift in the light absorption characteristics of the mixed-phase TiO₂ monolith as a function of W⁶⁺/Yb³⁺ co-doping. It is observed that the use of (8.0 mol%)W⁶⁺/0.4 (mole%)Yb³⁺ co-doped monolithic TiO₂ photocatalyst, with an energy bandgap of 2.77 eV demonstrates superior visible-light photocatalysis, which corroborates with the PLS studies in terms of voluminous e^-/h⁺ pair formation. The practical application of the photocatalyst has been investigated through a time-dependent dissipation of enrofloxacin, a widely employed antimicrobial drug, and its degradation pathway has been monitored by LC-MS-ESI and TOC analysis. The impact of physio-chemical parameters such as solution pH, sensitizers, drug concentration, dopant/codopant stoichiometry, catalyst quantity, and light intensity has been comprehensively studied to monitor the process efficiency.

Conventional and emerging technologies for removal of antibiotics from wastewater

Antibiotics and pharmaceuticals related products are used to enhance public health and quality of life. The wastewater that is produced from pharmaceutical industries still contains noticeable amount of antibiotics, and this has remained one of the major environmental problems facing public health. The conventional wastewater remediation approach employed by the pharmaceutical industries for the antibiotics wastewater removal is unable to remove the antibiotics completely. Besides, municipal and livestock wastewater also contain unmetabolized antibiotics released by human and animal, respectively. The antibiotic found in wastewater leads to antibiotic resistance challenges, also emergence of superbugs. Currently, numerous technological approaches have been developed to remove antibiotics from the wastewater. Therefore, it was imperative to critically review the weakness and strength of these current advanced technological approaches in use. Besides, the conventional methods for removal of antibiotics such as Klavaroti et al., Homem and Santos also discussed. Although, membrane treatment is discovered as the ultimate choice of approach, to completely remove the antibiotics, while the filtered antibiotics are still retained on the membrane. This study found, hybrid processes to be the best solution antibiotics removal from wastewater. Nevertheless, real-time monitoring system is also recommended to ascertain that, wastewater is cleared of antibiotics.

Applications of anodized TiO2 nanotube arrays on the removal of aqueous contaminants of emerging concern: A review

The presence of contaminants of emerging concern (CECs) in various water bodies and the associated threats to eco-system and human society have raised increasing concerns. To fight against such a problem, TiO₂ photocatalysis is considered to be a powerful tool. In recent decades, TiO₂ nanotube array (TNA) fabricated by electrochemical anodization emerged as a viable immobilized catalyst and its applications on CECs removal have gained a considerable amount of research interest. We herein present a critical review on the development of TNA and its applications on the removal of aqueous CECs. In this work, the CECs removal in different TNA based processes, the CECs removal mechanisms, the role of TNA properties, the role of operational parameters, and the role of water matrices are discussed. Moreover, perspectives on the current research progress are presented and recommendations on future research are elaborated.

Enhanced photoelectrocatalytic degradation of bisphenol a by BiVO4 photoanode coupling with peroxymonosulfate

Peroxymonosulfate (PMS) was introduced into a photoelectrocatalytic (PEC) system with a bismuth vanadate (BiVO₄) photoanode to enhance the PEC oxidation of bisphenol A (BPA). With the addition of 5 mM PMS, the degradation efficiency of 10 mg/L BPA was significantly improved from 24.2% to 100.0% within 120 min and the side reaction of O₂ evolution was avoided at a potential as low as 0.25 V. The electron spin resonance and radicals quenching results suggested that photogenerated holes instead of SO₄^•- and OH were primarily responsible for the BPA degradation. To further explore the role of PMS, a photocatalytic fuel cell with the structure of BiVO₄ (photoanode)|10 mg/L BPA|proton exchange membrane (separator)|5 mM PMS|Pt (cathode) was constructed and demonstrated that PMS played a key role as electrons acceptor instead of the precursor of SO₄^•-. The PEC tests including open-circuit potential, linear sweep voltammetry and electrochemical impedance spectroscopy indicated that a more efficient separation of photogenerated charges was achieved in the PEC process with the help of PMS, thus generating more photogenerated holes for enhanced BPA degradation. This work may provide a novel way to enhance the separation of photogenerated charges at the photoanode.

Greywater and bacteria removal with synchronized energy production in photocatalytic fuel cell based on anodic TiO2/ZnO/Zn and cathodic CuO/Cu

An approach that can recuperate of energy from wastewater treatment process is highly necessitate and would help to surmount the both environmental pollution and energy crisis issues. A photocatalytic fuel cell (PFC) employing an anodic TiO₂/ZnO/Zn and a cathodic CuO/Cu has been applied to degrade the raw greywater, which realized advanced organics destruction, bacteria disinfection, and synchronously electricity production. The improved photocatalytic performance has been observed when the cell was incorporated with anodic TiO₂/ZnO/Zn under UV and sunlight irradiation due to the enhanced electric field conductivity of the catalysts and heterojunction interface of TiO₂. In the constructed UV-activated PFC system, the electricity production capability was observed with the measured voltage and power density of 868 mV and 0.0172 mW cm^-2, respectively. Advanced chemical oxygen demand (COD) removal efficiency of greywater achieved a 100% completion within 60 min of light irradiation. The Escherichia coli (E. coli) colonies decreased significantly and accounted ∼99% disinfection efficiency. Moreover, the photoelectrochemical and photoluminescence (PL) experiments elucidated that the charge carrier separation efficiency were higher when TiO₂ was coupled to ZnO. The organic matter elimination principle was assessed by radical trapping experiment, and the findings indicated that the hydroxyl (OH) radical and hole (h⁺) appeared as major functions in the reaction. The stable cycle operation of the cell has been also obtained owing to the stable and film-type materials of anodic material. This performance was among the highest documented for PFC using real wastewater effluent as the fuel source.

Synergistic coupling Co3Fe7 alloy and CoFe2O4 spinel for highly efficient removal of 2,4-dichlorophenol by activating peroxymonosulfate

Efficient wastewater restoration depends on the robustness and capability of the catalyst to promote sophisticated decontamination technologies. In this study, Co₃Fe₇-CoFe₂O₄ nanoparticles (NPs) prepared by facile pyrolysis were completely characterized and used to decompose 2,4-dichlorophenol (2,4-DCP). Furthermore, the catalytic performance and relevant mechanisms involved in the activation of peroxymonosulfate (PMS) were also investigated. The optimal conditions were achieved at the catalyst loading of 0.05 g L^-1, PMS dosage of 1.26 g L^-1, and pH of 7.7 through the response surface methodology by using the Box-Behnken design model. Under optimal conditions, 97.1% efficiency of 2,4-DCP removal was obtained within 30 min. Moreover, the quenching experiments and electron paramagnetic resonance result indicated that sulfate (SO₄^•-) and hydroxyl (HO^•) radicals were considered as the dominant reactive oxygen species, which resulted in the effective removal of 2,4-DCP in the Co₃Fe₇-CoFe₂O₄/PMS system. Moreover, Co₃Fe₇-CoFe₂O₄ showed efficient catalytic performance in continuous five runs and exhibited less metal leaching of 0.052 and 0.036 mg L^-1 for Co and Fe species, respectively. Furthermore, no considerable change was observed in the structural characteristics of the fresh and used Co₃Fe₇-CoFe₂O₄ catalytic system. The above-mentioned results indicated that the synergistic effects between Co₃Fe₇ alloy and CoFe₂O₄ spinel not only significantly improved the activity and long-term durability of the catalyst, but also accelerated the Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺ redox cycles. Overall, the Co₃Fe₇-CoFe₂O₄/PMS system provides a novel advanced oxidation approach to further develop multifunctional transition metal-based nanomaterials responsible for producing surface-bound radicals and enhancing the remediation of refractory pollutants in the environmental application.

Influence of pH and DO on the ofloxacin degradation in water by UVA-LED/TiO2 nanotube arrays photocatalytic fuel cell: mechanism, ROSs contribution and power generation

The influence of pH and dissolved oxygen (DO) on the degradation of ofloxacin (OFX) in water by UVA-LED/TiO₂ nanotube arrays photocatalytic fuel cell (UVA-LED/TNA PFC) was investigated. The degradation pathway depended on the location of OFX frontier orbital with different ionization states and the role of reactive oxidative species (ROSs) played with varied pH and DO values. In presence of DO, the quencher tests revealed that O₂^- played a key role at pH 3.0, 7.0 and 11.0, while OH made its greatest contribution at pH 3.0 and the effect of h⁺ was largely inhibited at pH 11.0. Hydroxylation for cationic OFX was more significant, while demethylation and piperazinyl ring oxidation for anionic OFX occurred more quickly compared to other forms. Besides, zwitterionic OFX underwent decarboxylation and combination of demethylation & hydroxylation more easily. Much higher power generation was observed in presence of DO at pH 7.0, probably due to the enhanced adsorption of OFX on the TNA, and DO could amplify the electric potential between the two electrodes. The degradation efficiencies were almost the same in presence or absence of DO, but the pathways were different and e-_aq may replace O₂- as the leading ROSs in absence of DO.

Study on the internal electric field in the Cu2O/g-C3N4 p–n heterojunction structure for enhancing visible light photocatalytic activity

A Cu₂O/g-C₃N₄ p–n heterojunction efficiently removes tetracycline in the presence of a built-in electric field.

Comparative study of persulfate oxidants promoted photocatalytic fuel cell performance: Simultaneous dye removal and electricity generation

Introducing peroxymonosulfate (PMS) and peroxydisulfate (PDS) into the photocatalytic fuel cell (PFC) system were investigated by comparing the Reactive Brilliant Blue (KN-R) degradation and synchronous electricity production. The two persulfates (PS) themselves are strong oxidant, and could be activated and as electron sacrificial agent in the PFCs, facilitating the photoelectrocatalysis and expanding redox to the entire cell space. Hence, the two established PFC/PS systems manifested prominent cell performances, enhancing the KN-R decomposition and electric power production relative to the virgin PFC. Thereinto, the KN-R removal rate of PFC/PMS was faster than that of PFC/PDS, but an opposite trend appeared in the electricity generation. Besides, the cell performances of the two cooperative systems were evaluated at different operation conditions, including PS dosage, solution pH, and irradiation strength. Moreover, the dye elimination principle was explored by radicals scavenging experiment, and the consequence revealed that hydroxyl radical (HO^•), sulfate radical (SO₄^•-) and singlet oxygen were chief active species in the PFC/PMS, and HO^•, SO₄^•- and superoxide anion played the key roles in the PFC/PDS. Furthermore, the calculated economic indicator demonstrated that the economy of the two synergistic processes were greater than that of UV/PS and solo PFC, and the PFC/PDS was more cost-effective than PFC/PMS.

Efficient Degradation of Norfloxacin and Simultaneous Electricity Generation in a Persulfate-Photocatalytic Fuel Cell System

Photocatalytic fuel cell (PFC) has been verified to be a promising technique to treat organic matter and recover energy synchronously. Sulfate radicals (SO4·−), as a strong oxidant, have obvious advantages in the degradation of refractory pollutants compared with hydroxyl radicals (·OH), which is the dominant radical in PFC. This study reports a coupling method of PFC and persulfate (PS) activation to promote the degradation of antibiotic norfloxacin (NOR) and simultaneous electricity generation. The added PS as an electron acceptor could be activated by photoelectric effects to produce SO4·− at the electrodes-electrolyte interface. In the solution, PS as supporting electrolyte could accelerate the electron transfer and also be activated by ultraviolet (UV) light irradiation, which could extend the radical oxidation reaction to the whole solution and improve the PFC performance. The performance comparison among different systems indicated the excellent synergistic effect of PFC and PS activation for improving NOR degradation and electricity generation. The effects of influencing factors including initial pH, PS concentration, and initial NOR concentration on the degradation of NOR were investigated extensively to find out the optimal conditions. Moreover, according to the results of radical capture experiments, the significantly contribution of both SO4·− and ·OH to the degradation of NOR was demonstrated and a tentative function mechanism for the NOR degradation in the proposed system was provided. Finally, total organic carbon and real wastewater treatment confirmed the high mineralization and practical applicability of the proposed PFC/PS system.

Poly (3, 4-ethylenedioxythiophene) modified polyvinylidene fluoride membrane for visible photoelectrocatalysis and filtration

A polyvinylidene fluoride (PVDF) organic conductive membrane with photoelectric activity was successfully developed via printing of oxidant (FeCl₃·6H₂O) layer by layer and then chemical vapor deposition (CVD) of Poly (3, 4-ethylenedioxythiophene) (PEDOT). Four kinds of membranes were prepared by changing the number of oxidant coatings layers. The structure and photoelectric properties of four membranes were well characterized. The photocurrent density of 3.7 × 10^-4 A indicated that the four-oxidant coating layers membrane achieved the best performance in photo-electricity activity. A comprehensive study of degradation efficiency under different photoelectric conditions was carried out. Results showed that the photoelectrocatalytic removal of tetracycline hydrochloride was 1.6 and 7.9 times higher than that of photocatalysis and photolysis, respectively, under a voltage of 3 V assisted with visible light irradiation. The anti-interference and stability tests in continuous filtration process demonstrated that the dissolved organic matters (DOMs) can result in a 30% fluctuation on removal rate. The streaming potential tests of DOMs adsorption on membrane surface indicated that the more obvious the adsorption phenomenon was, the degradation of tetracycline hydrochloride was weaker. The degradation intermediates were identified and pathways were proposed in this work. The photoelectrocatalysis of PEDOT modified PVDF membrane provided a new potential for water purification.

Pulsed discharge plasma induced WO3 catalysis for synergetic degradation of ciprofloxacin in water: Synergetic mechanism and degradation pathway

Pulsed discharge plasma (PDP) was adopted to induce WO₃ for synergetic degradation of ciprofloxacin (CIP) in water. WO₃ was firstly characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), Photocurrents and Photoluminescence. The degradation results showed that PDP could induce WO₃ photocatalysis successfully, and a synergetic effect was established in PDP/WO₃ system. After 60 min treatment time, 0.16 g/L WO₃ increased the CIP removal from 71.3% to 99.6%, with the enhancement of the first-order kinetic constant from 0.020 min^-1 to 0.081 min^-1. Then, the effect of peak voltage, air flow rate and pH on CIP removal was evaluated. Active species trapping test verified that ·OH and ·O₂^- played the major role for plasma-degradation of CIP degradation, whereas OH and h⁺ were conductive to catalytic degrade CIP. WO₃ addition lead to the decline of O₃ and enhancement of OH no matter in deionized water or CIP solution. The degradation process was explored using fluorescence spectrograph, liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC). Finally, the possible degradation pathways of CIP degradation were proposed. The reuse test suggested WO₃ possessed excellent catalytic performance as well as good stability.

Improved degradation of anthraquinone dye by electrochemical activation of PDS

Electrochemical oxidation (EO) coupled with peroxydisulfate (PDS) activation as a synergistic wastewater treatment process (PDS/EO) was performed to degrade anthraquinone dye-Reactive Brilliant Blue (RBB) in aqueous solution. Introducing PDS into the EO improved the RBB removal than the sole PDS and conventional EO systems. The RBB could activate PDS to a certain degree by itself. By the comparison of various inorganic ions addition, it showed that adding NO₃^- as the background electrolyte was more effective than the systems using the Cl^- and SO₄^2-, respectively. In this PDS/EO-NO₃^- system, increasing PDS concentration (1-5 mmol L^-1) and current density (5-10 mA cm^-2) considerably promoted the degradation of RBB. The adjustment of the solution pH displayed that the acidic and neutral condition was beneficial to the RBB removal, and the synergistic effect was inverse ratio to the RBB initial concentration. Furthermore, the scavenger experiments verified that both SO₄^·- and HO· were the major active substances in the RBB decomposition, and other reactive oxygen species also had considerable contributions. Thereinto NO₃^- only act a catalytic agent to improve the generation of active matters in the PDS/EO-NO₃^-. Overall, the proposed synergistic process could serve as an efficient method for the degradation of anthraquinone dye.

Degradation of antibiotic chloramphenicol in water by pulsed discharge plasma combined with TiO2/WO3 composites: mechanism and degradation pathway

Pulsed discharge plasma (PDP) combined with TiO₂/WO₃ composites for chloramphenicol (CAP) degradation was investigated. The prepared TiO₂/WO₃ composites were characterized by scanning electron microscope, transmission electron microscope, nitrogen adsorption apparatus, zeta sizer, X-ray diffraction, Raman spectra, UV-Vis absorption spectroscopy, X-ray photoelectron spectroscopy, photocurrent and electrochemical impedance spectroscopy. The degradation performance showed that the addition of TiO₂/WO₃ composites significantly enhanced the removal efficiency of CAP in PDP system. At a peak voltage of 18 kV, the highest removal efficiency of CAP could reach 88.1% in PDP system with 4 wt% TiO₂/WO₃, which was 36.8% and 26.0% higher than that in sole PDP system and PDP/TiO₂ system, respectively. The TiO₂/WO₃ composites significantly accelerated interfacial charge transfer process compared to the pure TiO₂. Besides, the effect of catalyst dosage and peak voltage on CAP removal was evaluated. OH, O₃O₂^-, h⁺ and high-energy electrons contributed to CAP degradation in PDP-TiO₂/WO₃ system. Addition of TiO₂/WO₃ composites can decompose O₃ and produce more OH and H₂O₂. The degradation intermediates were measured by liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC). The cycling degradation experiment showed that the TiO₂/WO₃ composites have good reusability as well as stability.

Data-Mining for Processes in Chemistry, Materials, and Engineering

With the rapid development of machine learning techniques, data-mining for processes in chemistry, materials, and engineering has been widely reported in recent years. In this discussion, we summarize some typical applications for process optimization, design, and evaluation of chemistry, materials, and engineering. Although the research and application targets are various, many important common points still exist in their data-mining. We then propose a generalized strategy based on the philosophy of data-mining, which should be applicable for the design and optimization targets for processes in various fields with both scientific and industrial purposes.