Photocatalytic oxidation of organic dyes and pollutants in wastewater using different modified titanium dioxides: A comparative review

Cellulose acetate membranes loaded with WO3/g-C3N4: a synergistic approach for effective photocatalysis

The objective of this study is to develop an efficient, easily recoverable membrane-based photocatalyst for removing organic pollutants from aqueous solutions. This study documents the effective synthesis of a novel composite photocatalyst comprising WO3/g-C3N4(WCN) loaded onto cellulose acetate (CA). The physicochemical properties of the synthesized nanocomposites were validated using a range of techniques, including Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy, and UV-visible diffuse reflectance spectroscopy. SEM analysis revealed that the WCN particles exhibited a well-decorated arrangement on the CA surface in the form of spherical particles. The successfully synthesized film was utilized as a potential adsorbent for removing organic pollutants such as Rhodamine B (Rh-B) and Methylene blue (MB) from aqueous solutions under UV light illumination. The results showcased the significant potential of the WCN@CA nanocomposite, achieving a remarkable 83% and 85% efficiency in eliminating Rh-B and MB. The pseudo-first-order kinetic models were found to be appropriate for both dye adsorption onto the WCN@CA nanocomposite. The WCN@CA catalyst, capable of being reused five times without significant loss of efficiency, shows great potential for decomposing toxic organic pollutants. The novelty of this work lies in the innovative combination of WCN with CA, resulting in a highly efficient and reusable photocatalyst for environmental remediation.

Atrazine degradation through a heterogeneous dual-effect process using Fe-TiO2-allophane catalysts under sunlight

This study investigated the novel application of Fe-TiO2-allophane catalysts with 6.0 % w/w of iron oxide and two TiO2 proportions (10 % and 30 % w/w) for degrading atrazine (ATZ) using the heterogeneous dual-effect (HDE) process under sunlight. Comparative analyses with Fe-allophane and TiO2-allophane catalysts were conducted in both photocatalysis (PC) and HDE processes. FTIR spectra reveal the unique hydrous feldspathoids structure of allophane, showing evidence of new bond formation between Si-O groups of allophane clays and iron hydroxyl species, as well as Si-O-Ti bonds that intensified with higher TiO2 content. The catalysts exhibited an anatase structure. In Fe-TiO2-allophane catalysts, iron oxide was incorporated through the substitution of Ti4+ by Fe3+ in the anatase crystal lattice and precipitation on the surface of allophane clays, forming small iron oxide particles. Allophane clays reduced the agglomeration and particle size of TiO2, resulting in an enhanced specific surface area and pore volume for all catalysts. Iron oxide incorporation decreased the band gap, broadening the photoresponse to visible light. In the PC process, TiO2-allophane achieves 90 % ATZ degradation, attributed to radical species from the UV component of sunlight. In the HDE process, Fe-TiO2-allophane catalysts exhibit synergistic effects, particularly with 30 % w/w TiO2, achieving 100 % ATZ degradation and 85 % COD removal, with shorter reaction time as TiO2 percentage increased. The HDE process was performed under less acidic conditions, achieving complete ATZ degradation after 6 h without iron leaching. Consequently, Fe-TiO2-allophane catalysts are proposed as a promising alternative for degrading emerging pollutants under environmentally friendly conditions.

Biogenic Punica granatum Flower Extract Assisted ZnFe2O4 and ZnFe2O4-Cu Composites for Excellent Photocatalytic Degradation of RhB Dye

Globally, the textile industry contributes to pollution through accidental discharges or discharge of contaminated wastewater into waterways, significantly affecting water quality. These pollutants, including dye molecules, are environmental hazards for aquatic and terrestrial life. The field of visible light-mediated photocatalysis has experienced rapid growth, driven by the utilization of photocatalysts that can absorb low-energy visible light and effectively degrade dyes. In the present study, we report a simple method to controllably synthesize Fe2O3, ZnO, and ZnFe2O4 using the one-pot synthesis method. In the subsequent step, copper (Cu) was deposited on the surface of ZnFe2O4 (forming ZnFe2O4-Cu) using a facile, green, and cost-effective method. The synthesized samples were characterized using various techniques, including XRD, UV-Vis DRS, FT-IR, SEM-EDX, HR-TEM, XPS, PL, and BET analysis. These techniques were employed to investigate the composition, morphology, structure, and photophysical properties of as-prepared samples. The ZnFe2O4-Cu nanocomposite demonstrated efficient photocatalytic activity for degrading RhB dye pollutants under visible light. The photocatalyst was successfully reused for three consecutive cycles without significantly decreasing performance. Furthermore, during the study, the radical scavenging test emphasized the role of different radicals in the degradation of dye pollutants. This research has the potential to enable the efficient production of high-performance photocatalysts that can rapidly eliminate ecologically harmful dyes from aqueous solutions.

Research progress of TiO2-based photocatalytic degradation of wastewater: bibliometric analysis

The pollution caused by modernization and industrialization has caused serious harm to the biodiversity of the earth. TiO2-based photocatalyst has been widely studied as an effective and sustainable water environment remediation material. In this study, we analyzed the status and research trends of TiO2-based photocatalytic degradation of wastewater in depression from 2003 to 2023 to provide a reference for further research. "Doping", "Modification" and "Heterojunction" were used as keywords, and 817 related academic literatures were screened out by using Web of Science database. Through the visualization software VOSviewer and CiteSpace, the authors, institutions and literature keywords were clustered. The results show that since 2008, the annual number of published papers on TiO2-based photocatalytic degradation of wastewater has increased from 9 to 114. Among them, China has published 432 articles and made great contributions, and there are many representative research teams. Chinese universities are the main body to study TiO2-based photocatalytic degradation of wastewater, but the cooperation between universities is not as close as that abroad. This paper comprehensively analyzes the research hotspots of TiO2-based photocatalytic degradation of wastewater, such as the doping of TiO2 and the construction of different types of heterojunctions of TiO2. It is expected that these analysis results will provide new research ideas for researchers to carry out future research on related topics and let researchers know in-depth research institutions and possible collaborators to conduct academic exchanges and discussions with active institutions.

A comparison of endosulfan removal by photocatalysis process under UV-A and visible light irradiation: optimization, degradation byproducts and reuse

In this study, the removal efficiency of endosulfan as a persistent organic pollutant and formation of its metabolites were investigated using Ag/TiO2/Fe3O4 photocatalyst under visible and UV-A light. Light intensity, catalyst amount, initial endosulfan concentration, initial pH and time were determined as controllable factors for Taguchi experimental design. The highest removal efficiencies of endosulfan were achieved as 86.14% and 85.46% for visible and UV-A light sources, respectively. According to the greatest best criterion, the level at which the highest S/N ratio was obtained for each parameter was accepted as the optimum value. As a result of the validation experiments, 94.2% and 91.9% efficiency were obtained for visible and UV-A light, respectively. The metabolite formations of endosulfan (endosulfan sulfate, ether, and lactone) remained below 7% in all experiments on a concentration basis. In the reuse experiments of the magnetically recovered photocatalyst, high removal efficiency of around 80% was obtained after four cycles. The removal efficiencies were found to be 86.7% and 84.8%, for real samples taken from the drinking water treatment plant inlet and the spring water network injected with endosulfan under optimal photocatalysis experimental conditions, respectively. It has been shown that nitrate and sulfate anions, which are in significant concentrations in raw water samples, have very little effects on endosulfan removal. The overall results showed that the Ag/TiO2/Fe3O4 photocatalyst was produced successfully, the catalyst was highly effective in the mineralization of endosulfan in synthetic and real water samples under UV and visible light, and effective yields could be obtained even with reuse.

Supplementary information

The online version contains supplementary material available at 10.1007/s40201-023-00864-z.

Photocatalytic oxidation of Reactive Red 195 by bimetallic Fe-Co catalyst: Statistical modeling and optimization via Box-Behnken design

Response surface methodology (RSM) is an effective tool for process optimization with multi-complex operational factors. The present work aims to model and optimize the photocatalytic oxidation (PCO) parameters of Reactive Red 195 (RR195) dye decoloration with the SiO2-supported Fe-Co catalyst (FCS) derived from a novel catalyst synthesis method, fluidized-bed crystallization (FBC) process, using Box-Behnken design (BBD) as the RSM statistical model. The Fe-Co@SiO2 catalyst was successfully fabricated using the FBC process, and it showed good catalytic activity and performance toward the degradation of RR195. The extent of the effects of pH, H2O2 dosage (HD), catalyst loading (CL), and operating time (t) on the decoloration of RR195 was studied. Hence, the order of variable significance follows the sequence: pH > t > CL > HD. pH has the most significant effect among the variables for RR195 decoloration. The decoloration efficiency predicted by the BBD model was 88.3% under the optimized operation conditions of initial pH of 3.15, 0.76 mM H2O2, 1.18 g L-1 FCS and 59.4 min of operating time. The actual decoloration efficiency was very close to the predicted value indicating that BBD can efficiently be utilized to optimize RR195 degradation with FCS under the PCO system.

NaBiS2 decorated polysaccharide sponges for adsorption-photocatalytic degradation of dye under visible light illumination

Dye is emissions aggravating aquatic ecosystem pollution, and photocatalysis is considered the most appealing option to remove dyes by degradation. However, the current photocatalysts suffer from agglomeration, large bandgaps, high mass transfer resistance, and high operation cost. Herein, we present a facile hydrothermally induced phase separation and in situ synthesis strategy for fabrication of sodium bismuth sulfide (NaBiS₂)-decorated chitosan/cellulose sponges (NaBiCCSs). The NaBiCCSs demonstrate unique polysaccharide cellular structure (150-500 μm), uniformly immobilized NaBiS₂ nanoparticles (70-90 nm), narrow bandgap (1.18 eV), high photocurrent (0.74 μA/cm²), and outstanding compressibility. Benefiting from the characteristics and the high affinity to dyes, the NaBiCCSs provide innovative synergistic adsorption-photocatalytic degradation model for dye removal, attaining a superior methylene blue removal rate of 98.38 % under visible light illumination and offering good reusability. This study offers a sustainable technical solution for dye contaminant removal.

Recent perspective of antibiotics remediation: A review of the principles, mechanisms, and chemistry controlling remediation from aqueous media

Antibiotic pollution is an ever-growing concern that affects the growth of plants and the well-being of animals and humans. Research on antibiotics remediation from aqueous media has grown over the years and previous reviews have highlighted recent advances in antibiotics remediation technologies, perspectives on antibiotics ecotoxicity, and the development of antibiotic-resistant genes. Nevertheless, the relationship between antibiotics solution chemistry, remediation technology, and the interactions between antibiotics and adsorbents at the molecular level is still elusive. Thus, this review summarizes recent literature on antibiotics remediation from aqueous media and the adsorption perspective. The review discusses the principles, mechanisms, and solution chemistry of antibiotics and how they affect remediation and the type of adsorbents used for antibiotic adsorption processes. The literature analysis revealed that: (i) Although antibiotics extraction and detection techniques have evolved from single-substrate-oriented to multi-substrates-oriented detection technologies, antibiotics pollution remains a great danger to the environment due to its trace level; (ii) Some of the most effective antibiotic remediation technologies are still at the laboratory scale. Thus, upscaling these technologies to field level will require funding, which brings in more constraints and doubts patterning to whether the technology will achieve the same performance as in the laboratory; and (iii) Adsorption technologies remain the most affordable for antibiotic remediation. However, the recent trends show more focus on developing high-end adsorbents which are expensive and sometimes less efficient compared to existing adsorbents. Thus, more research needs to focus on developing cheaper and less complex adsorbents from readily available raw materials. This review will be beneficial to stakeholders, researchers, and public health professionals for the efficient management of antibiotics for a refined decision.

Water remediation using titanium and zinc oxide nanomaterials through disinfection and photo catalysis process: A review

Various pesticides and organic compounds generated as a result of rapid industrialization and pharmaceutical companies pose a major threat to the environment. Novel photocatalysts based on zinc oxide and titanium oxide exhibit great potential towards absorption of these organic pollutants from wastewater. The photocatalysts possess various extraordinary properties like photocatalytic degradation potential, non-toxic and high stability. However, several limitations are also associated with the applications of these photocatalysts like poor affinity, particle agglomeration, high band gap and recovery issues. Hence, optimization is required to enhance their efficiency and at the same time make them cost effective and sustainable. The review covers the mechanism for water treatment, limitations and development of different modification strategies that improve the removal efficiency of titanium and zinc oxide based photocatalysts. Thus, further research in the field of photocatalysts can be encouraged for carrying out water remediation.

An overview of wastewater treatment using combined heterogeneous photocatalysis and membrane distillation

The need for efficient remediation solutions to wastewater has risen due to the concerning prevalence of toxic organic pollutants. It is possible for the linked photocatalysis-membrane separation system to concurrently achieve the photoreaction of pollutants and their removal from wastewater in order to accomplish the goal of completely purifying the wastewater. This investigation's objective is to provide analytical overview of the photocatalytic and membrane coupling process, photocatalytic membrane reactors, and the potential applications of these technologies in the treatment of wastewater for the persistent organic matter removal. In the review, an examination of photocatalytic and membrane processes to remove organic compounds from wastewater is presented. Based on the literature analysis, it was observed that the application of photocatalytic membrane reactors is significantly influenced by a wide variety of factors. Some of these factors include pollutant concentration, dissolved oxygen, aeration, pH, and hydraulic retention time. Light intensity is another factor that has a significant influence. It was also revealed how distillation membranes work when integrated with photocatalytic process. This brief overview will help researchers understand how successful coupled photocatalytic and membrane distillation are in the treatment of wastewater containing organic pollutants.

Photocatalytic removal of imidacloprid containing frequently applied insecticide in agriculture industry using Co3O4 modified MoO3 composites

Water pollution caused by the frequent utilization of pesticides in the agriculture industry is one of the major environmental concerns that require proper attention. In this context, the photocatalytic removal of pesticides from contaminated water in the presence of metallic oxide photocatalysts is quite in approach. In the present study, Orthorhombic MoO3 has been modified with varying amount of cobalt oxide through wet impregnation for the removal of imidacloprid and imidacloprid-containing commercially available insecticide. The solid-state absorption response and band gap evaluation of synthesized composites revealed a significant extension of absorption cross-section and absorption edge in the visible region of the light spectrum than pristine MoO3. The indirect band gap energy varied from ∼2.88 eV (MoO3) to ∼2.15 eV (10% Co3O4-MoO3). The role of Co3O4 in minimizing the photo-excitons’ recombination in MoO3 was studied using photoluminescence spectroscopy. The orthorhombic shape of MoO3 was confirmed through X-ray diffraction analysis and scanning electron microscopy. Moreover, the presence of distinct absorption edges and diffraction peaks corresponding to Co3O4 and MoO3 in absorption spectra and XRD patterns, respectively verified the composite nature of 10% Co3O4-MoO3. The photocatalytic study under natural sunlight irradiation showed higher photocatalytic removal (∼98%) of imidacloprid with relatively higher rate by 10% Co3O4-MoO3 composite among all contestants. Furthermore, the photocatalytic removal (∼93%) of commercially applied insecticide, i.e., Greeda was also explored.

Photo Energy-Enhanced Oxygen Reduction and Evolution Kinetics in Zn-Air Batteries

Harvesting solar energy directly to boost the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on an air cathode is a promising approach. Herein, we synthesize a step-scheme (S-scheme) titanium dioxide-indium selenide (TiO₂-In₂Se₃) heterojunction catalyst. The onset potential in ORR under light illumination reaches 1.28 V and the onset potential decreases to 0.48 V in OER. When an S-scheme TiO₂-In₂Se₃ heterojunction is exposed to light, photogenerated electrons at the conduction band (CB) of TiO₂ migrate to the valence band (VB) of In₂Se₃ due to the built-in electric field. The photogenerated electrons with strong reduction capability on the CB of In₂Se₃ and the holes with strong oxidation capability on the VB of TiO₂ boost the cathode reaction kinetics (ORR/OER). The excellent outcome reveals tremendous commercial potential of photo-enhanced Zn-air batteries.

Preparation of MnO2-Carbon Materials and Their Applications in Photocatalytic Water Treatment

Water pollution is one of the most important problems in the field of environmental protection in the whole world, and organic pollution is a critical one for wastewater pollution problems. How to solve the problem effectively has triggered a common concern in the area of environmental protection nowadays. Around this problem, scientists have carried out a lot of research; due to the advantages of high efficiency, a lack of secondary pollution, and low cost, photocatalytic technology has attracted more and more attention. In the past, MnO₂ was seldom used in the field of water pollution treatment due to its easy agglomeration and low catalytic activity at low temperatures. With the development of carbon materials, it was found that the composite of carbon materials and MnO₂ could overcome the above defects, and the composite had good photocatalytic performance, and the research on the photocatalytic performance of MnO₂-carbon materials has gradually become a research hotspot in recent years. This review covers recent progress on MnO₂-carbon materials for photocatalytic water treatment. We focus on the preparation methods of MnO₂ and different kinds of carbon material composites and the application of composite materials in the removal of phenolic compounds, antibiotics, organic dyes, and heavy metal ions in water. Finally, we present our perspective on the challenges and future research directions of MnO₂-carbon materials in the field of environmental applications.

In situ recombination for durable photoelectrocatalytic degradation of organic dye in wastewater

Photoelectrocatalysis (PEC) can effectively degrade organic pollutants by using photoelectrodes without secondary pollution. However, significant mass transport resistance and decreased catalytic activity caused by the shedding of active components remain a barrier to achieving the photocatalytic system with a high degradation rate and long-term durability. Here, an in situ recombination concept is presented to overcome this challenge. The bionic coral-like electrode, obtained by in situ assembly of UIO-66 around TiO₂ nanoflowers (TNF) on Ti-foam substrate, is employed as the photoanode in PEC. Ex situ evaluation of photoelectrochemical activity demonstrates that the UIO-66@TNF/Ti-foam (U@T/T) design significantly improves the light-propagation, light-absorption and charge transfer. In Situ degradation evaluations also shows that the interesting design promotes rapid and stable degradation of organic dye (e.g. Rhodamine B (RhB)). At 2.0 V of bias potential and pH 7.0 in 5 mg L^-1 RhB, under the action of active species such as ·O₂^- and ·OH (proved by the degradation mechanism experiments), the removal rate of RhB can reach 96.1% at 120 min and almost complete removal at 200 min (99.1%).

Transition metal doped CeO2 for photocatalytic removal of 2-chlorophenol in the exposure of indoor white light and antifungal activity

Besides natural sunlight and expensive artificial lights, economical indoor white light can play a significant role in activating a catalyst for photocatalytic removal of organic toxins from contaminated water. In the current effort, CeO₂ has been modified with Ni, Cu, and Fe through doping methodology to study the removal of 2-chlorophenol (2-CP) in the illumination of 70 W indoor LED white light. The absence of additional diffractions due to the dopants and few changes such as reduction in peaks' height, minor peak shift at 2θ (28.525°) and peaks' broadening in XRD patterns of modified CeO₂ verifies the successful doping of CeO₂. The solid-state absorption spectra revealed higher absorbance of Cu-doped CeO₂ whereas a lower absorption response was observed for Ni-doped CeO₂. An interesting observation regarding the lowering of indirect bandgap energy of Fe-doped CeO₂ (∼2.7 eV) and an increase in Ni-doped CeO₂ (∼3.0 eV) in comparison to pristine CeO₂ (∼2.9 eV) was noticed. The process of e ^-- h ⁺ recombination in the synthesized photocatalysts was also investigated through photoluminescence spectroscopy. The photocatalytic studies revealed the greater photocatalytic activity of Fe-doped CeO₂ with a higher rate (∼3.9 × 10^-3 min^-1) among all other materials. Moreover, kinetic studies also revealed the validation of the Langmuir-Hinshelwood kinetic model (R² = 0.9839) while removing 2-CP in the exposure of indoor light with a Fe-doped CeO₂ photocatalyst. The XPS analysis revealed the existence of Fe³⁺, Cu²⁺ and Ni²⁺ core levels in doped CeO₂. Using the agar well-diffusion method, the antifungal activity was assessed against the fungus M. fructicola and F. oxysporum. Compared to CeO₂, Ni-doped CeO₂, and Cu-doped CeO₂ nanoparticles, the Fe-doped CeO₂ nanoparticles have outstanding antifungal properties.

Enhanced photocatalytic activity of nano-silica/copper plasmon by aminofunctional silane for dye pollutant degradation

The synthesis of silica gel nanostructures and loading it with copper specie via a hydrothermal process were performed. The sample is treated with an amino-functional reagent 3-aminopropyl triethoxysilane (APTES). The products were characterized by X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), TGA/DSC measurements, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the nanostructures were studied for degradation of methylene blue dye (as a classic dye contaminant) in aqueous solution utilizing visible light source. The results displayed that the sample treated with APTES is much more effective in photocatalytic degradation of methylene blue. This modified catalyst could eliminate methylene blue dye (50 mL, 18 µg mL^-1) within 60 min under visible light. The degradation efficiency was increased by shortening the degradation time to 30 min in the alkaline medium. The pseudo-first-order model well describes the kinetics of the reaction.

A review on bismuth-based materials for the removal of organic and inorganic pollutants

Modernized lifestyle and increased industrialization threaten living organisms because of the pollutants released from industries and household wastes. The presence of even small amounts of pollutants (organic pollutants (OPs) and inorganic pollutants-heavy metals (HMs)) shows significant effects. Thus wastewater treatment is urgently needed before being subjected to use. Many methods and materials have been developed and reported for the removal of pollutants from wastewater. This review focused on the removal of both OPs and HMs using bismuth-based (Bi-based) materials because of their low toxicity and excellent properties compared to other metals. Bi-based materials as a photocatalyst for photodegradation of OPs are discussed in detail with synthesis methods. Further, since few reviews are available on the Bi-based material for the removal and sensing of HMs, this topic was intentionally summarized. About 200 published articles and reviews have been reviewed here. Additionally, the key point that needs to be focused on the development of Bi-based photocatalysts for the removal of OPs and for upgrading the Bi-based materials as adsorbents for HMs are conferred in the outlook. This will help many researchers in their upcoming work.

Silicon carbide catalytic ceramic membranes with nano-wire structure for enhanced anti-fouling performance

Membrane fouling is a critical challenge for current ceramic membranes, which suffer from low flux and insufficient removal. Development of self-cleaning catalytic ceramic membranes is promising to address this challenge. Herein, we design heterogeneous silicon carbide ceramic membranes featuring a novel structure of g-C₃N₄-decorated β-SiC nano-wire catalytic functional layer, which enables enhanced anti-fouling self-cleaning performance. At chemical harsh (alkaline or especially acidic) conditions, the nano-wire membrane exhibits catalysis-enhanced removal performance for organic contaminants. Unlike conventional particle-packing membrane structure, such a nano-wire network membrane structure has not only high porosity (56.1%), but exceptional water permeance (110 L·m^-2·h^-1·bar^-1) and removal (100%) of organic substance under simulated sunlight, outperforming state-of-the-art organic membranes and ceramic membranes. Superoxide radical (∙O₂^-) was experimentally confirmed to be major reactive species responsible for self-cleaning function. We also propose a catalytic mechanism model with radical formation pathway, enabled by the as-formed g-C₃N₄@β-SiC heterojunction structure with reduced electron-hole recombination. This work would provide new insights into not only rational design of next-generation ceramic membranes with self-cleaning function but also more applications of efficient treatment of refractory wastewaters containing degradable organic substances by using such membranes.

Photocatalytic evaluation and characterization of TiO2-riboflavin phosphate film: analysis of reactive oxygen species

The effect of Riboflavin-5'-phosphate (RFPO₄) sensitization on photocatalytic properties of TiO₂ film was studied. RFPO₄ was adsorbed on film surface to investigate the photophysical properties of TiO₂ upon blue-light photoexcitation. The film was characterized through scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and diffuse reflectance spectroscopy. The efficiency of the TiO₂/RFPO₄ film was tested for pollutant elimination in aqueous media in a visible-light-driven system. The phenol paradigmatic model was employed in an aqueous solution as a contaminant target. TiO₂/RFPO₄ sensitized photodegradation of phenol, which produces catechol, hydroquinone, and benzophenone, was monitored by absorption spectroscopy and HPLC. The results indicated that phenol degradation with TiO₂/RFPO₄ film was due to the photogeneration of two reactive oxygen species, singlet molecular oxygen (O₂(¹Δ_g)) and superoxide radical anion (O₂^·-) identified through specific detection techniques. The presence of O₂(¹Δ_g) is reported here for the first time as generated from a sensitized TiO₂ film upon visible-light photoirradiation. Based on the photophysical determinations, a photocatalytic mechanism for TiO₂/RFPO₄ was established.

Integrated process approach for degradation of p-cresol pollutant under photocatalytic reactor using activated carbon/TiO2 nanocomposite: application in wastewater treatment

Over the years, biodegradation has been an effective technique for waste water treatment; however, it has its own limitations. In order to achieve a higher degradation efficacy, integrated processes are being focus in this area. Therefore, the present study is targeted towards the coupling of biodegradation and photocatalytic degradation of p-cresol. The biodegradation of p-cresol was performed via lab isolate Serratia marcescens ABHI001. The obtained results confirmed that ~85% degradation of p-cresol was accomplished using Serratia marcescens ABHI001 strain in 18 h. Consequently, degradation of remaining residue (remaining p-cresol concentration initially used) was also examined in a batch reactor using activated carbon-TiO₂ nanocomposite (AC/TiO₂-NC) as a catalyst under the exposure of UV radiation. The AC/TiO₂-NC was processed via sol-gel technique and characterized by various techniques, namely Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transformed infrared spectroscopy (FT-IR). The investigation allowed p-cresol degradation further augment up to ~96% with the help of spectrophotometer trailed by high performance liquid chromatography (HPLC). This study demonstrates that integrated process (biodegradation-photodegradation) is the cost-effective bioremediation process to overcome such kinds of pollutant issues.

Biogenic Photo-Catalyst TiO2 Nanoparticles for Remediation of Environment Pollutants

This article reports a benign environmentally friendly fabrication method of titanium dioxide (TDO) nanoparticles (named TDO NPs3, TDO NPs5, and TDO NPs8) using aqueous extract of durva herb waste. This synthesis process avoids use of harmful substances and persistent chemicals throughout the order and enables us to control the size of the nanomaterials. Characterization of TDO nanoparticles was analyzed by ultraviolet-visible spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The morphological nature of the TDO samples was inspected by transmission electron microscopy, which indicated that the TDO NPs3, TDO NPs5, and TDO NPs8 were spherical in shape, with average sizes of 5.14, 12.54, and 29.61 nm, respectively. The stability of TDO nanoparticles was assessed using thermogravimetric analysis and dynamic light scattering analysis. These samples could be used for degradation of polluting industrial textile dyes, such as methylene blue (MB) and rhodamine B (Rh-B). Remarkably, the TDO NPs3 sample (5.14 nm size) exhibits a noticeable degradation of the MB dye in a shorter time period (50 min) than the TDO NPs8 sample with a size of 29.61 nm (120 min). The TDO NPs3 sample was also tested for degradation of Rh-B dye, showing high degradation efficiency over a short period of time (60 min). In contrast, the TDO NPs8 sample showed degradation of the Rh-B dye in 120 min. The effect of the dye concentration and the catalyst dose to remove dye pollutants has also been investigated. The synthesized TDO NPs act as exceptional catalysts for the degradation of dyes, and they are promising materials for the degradation of industrial polluting dyes.

Noble metal-doped TiO2 thin films in the efficient removal of Mordant Orange-1: insights of degradation process

Nanocomposite Ag⁰(NPs)/TiO₂ is synthesised in a facile template method enabling nanoparticles of reduced Ag evenly distributed within the titania network. The morphological studies of nanocomposites were extensively performed employing SEM/EDX (scanning electron microscopy/energy dispersive X-ray), TEM (transmission electron microscopy) and AFM (atomic force microscopy). Moreover, the bandgap energies of materials were obtained using the diffuse reflectance spectrometer (DRS). The newer insights in the photocatalytic elimination of Mordant Orange-1 (MO1) was obtained using the nanocomposite thin film for various parametric studies utilising the UV-A and LED illuminations. The kinetics of degradation of MO1 was performed, and the rate constant was favoured at lower concentrations of MO1. Moreover, the elimination efficiency of MO1 was favoured with a decrease in solution pH. The NPOC results inferred that a fairly good extent of MO1 was mineralised using a thin-film catalyst for both the UV-A and LED illuminations. The minimal effect of several co-ions demonstrated the applicability of thin films in the elimination of MO1, and the stability of the thin film has shown the potential applicability of thin-film catalysts. Further, the mechanism of photocatalytic degradation was demonstrated with the radical scavenger studies and ascertained the reaction pathways.

Olive Mill Wastewater (OMW) Treatment Using Photocatalyst Media

A new nanophotocatalysts series of M2Zr2O7 (M = Mn, Cu, and Fe) and doped Fe2Zr2O7 systems were prepared via sol-gel using the pechini method, characterized, and tested in photocatalytic degradation of olive mill wastewater (OMW). The photocatalytic degradation of the prepared materials was evaluated by measuring total phenolic compounds (TPCs) using the Folin-Ciocalteu method for variable pH under a commercial LED lamp (45 W). The removal of TPCs was measured at different contact times ranging from 2 h to 6 days. X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis approved the nano size of (5–17 nm) and quasi-spherical morphology of the prepared materials. ICP-OES analysis confirmed the XRD analysis and approved the structure of the prepared materials. Aggregation of the nanomaterials was observed using TEM imaging. Brunauer-Emmett-Teller (BET) analysis measured a 67 m2/g surface area for Fe2Zr2O7. Doping Fe with Mn increased the surface area to 173 m2/g and increased to 187 m2/g with a further increase of the Mn dopant. Increasing the Mn dopant concentration increased both surface area and photocatalytic degradation. The highest degradation of TPCs was observed for Mn2Zr2O7 around 70% at pH 10 and exposure time up to one day.

Green Biosynthesis of Tin Oxide Nanomaterials Mediated by Agro-Waste Cotton Boll Peel Extracts for the Remediation of Environmental Pollutant Dyes

The sustainable synthesis of metal oxide materials provides an ecofriendly and more exciting approach in the domain of a clean environment. Besides, plant extracts to synthesize nanoparticles have been considered one of the more superior ecofriendly methods. This paper describes the biosynthetic preparation route of three different sizes of tetragonal structure SnO₂ nanoparticles (SNPs) from the agro-waste cotton boll peel aqueous extract at 200, 500, and 800 °C for 3 h and represents a low-cost and alternative preparation method. The samples were characterized by X-ray diffraction, Fourier transform infrared spectrophotometry, ultraviolet-visible absorption spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy. Surface area and porosity size distribution were identified by nitrogen adsorption-desorption isotherms and Brunauer-Emmett-Teller analysis. The photocatalytic properties of the SNP samples were studied against methylene blue (MB) and methyl orange (MO), and the degradation was evaluated with three different size nanomaterials of 3.97, 8.48, and 13.43 nm. Photocatalytic activities were carried out under a multilamp (125 W Hg lamps) photoreactor. The smallest size sample exhibited the highest MB degradation efficiency within 30 min than the most significant size sample, which lasted 80 min. Similarly, in the case of MO, the smallest sample showed a more superior degradation efficiency with a shorter period (40 min) than the large-size samples (100 min). Therefore, our studies suggested that the developed SNP nanomaterials could be potential, promising photocatalysts against the degradation of industrial effluents.

A Flower-like In2O3 Catalyst Derived via Metal-Organic Frameworks for Photocatalytic Applications

The most pressing concerns in environmental remediation are the design and development of catalysts with benign, low-cost, and efficient photocatalytic activity. The present study effectively generated a flower-like indium oxide (In₂O₃-MF) catalyst employing a convenient MOF-based solvothermal self-assembly technique. The In₂O₃-MF photocatalyst exhibits a flower-like structure, according to morphology and structural analysis. The enhanced photocatalytic activity of the In₂O₃-MF catalyst for 4-nitrophenol (4-NP) and methylene blue (MB) is likely due to its unique 3D structure, which includes a large surface area (486.95 m² g^-1), a wide spectrum response, and the prevention of electron-hole recombination compared to In₂O₃-MR (indium oxide-micro rod) and In₂O₃-MD (indium oxide-micro disc). In the presence of NaBH₄ and visible light, the catalytic performances of the In₂O₃-MF, In₂O₃-MR, and In₂O₃-MD catalysts for the reduction of 4-NP and MB degradation were investigated. Using In₂O₃-MF as a catalyst, we were able to achieve a 99.32 percent reduction of 4-NP in 20 min and 99.2 percent degradation of MB in 3 min. Interestingly, the conversion rates of catalytic 4-NP and MB were still larger than 95 and 96 percent after five consecutive cycles of catalytic tests, suggesting that the In₂O₃-MF catalyst has outstanding catalytic performance and a high reutilization rate.

Scale-Up of a Heterogeneous Photocatalytic Degradation Using a Photochemical Rotor-Stator Spinning Disk Reactor

Many chemical reactions contain heterogeneous reagents, products, byproducts, or catalysts, making their transposition from batch to continuous-flow processing challenging. Herein, we report the use of a photochemical rotor–stator spinning disk reactor (pRS-SDR) that can handle and scale solid-containing photochemical reaction conditions in flow. Its ability to handle slurries was showcased for the TiO₂-mediated aerobic photodegradation of aqueous methylene blue. The use of a fast rotating disk imposes high shear forces on the multiphase reaction mixture, ensuring its homogenization, increasing the mass transfer, and improving the irradiation profile of the reaction mixture. The pRS-SDR performance was also compared to other lab-scale reactors in terms of water treated per reactor volume and light power input.

Synthesis of Polyaniline Supported CdS/CdS-ZnS/CdS-TiO2 Nanocomposite for Efficient Photocatalytic Applications

Photocatalytic degradation can be increased by improving photo-generated electrons and broadening the region of light absorption through conductive polymers. In that view, we have synthesized Polyaniline (PANI) with CdS, CdS-ZnS, and CdS-TiO₂ nanocomposites using the chemical precipitation method, characterized and verified for the photo-degradation of Acid blue-29 dye. This paper provides a methodical conception about in what way conductive polymers “PANI” enhances the performance rate of composite photocatalysts (CdS, CdS-ZnS and CdS-TiO₂). The nanocomposites charge transfer, molar ratio, surface morphology, particle size, diffraction pattern, thermal stability, optical and recombination of photo-generated charge carrier properties were determined. The production of nanocomposites and their efficient photocatalytic capabilities were observed. The mechanism of photocatalysis involved with PC, CZP and CTP nanocomposites are well presented by suitable diagrams representing the exchange of electrons and protons among themselves with supported equations. We discovered that increasing the number of nanocomposites in the membranes boosted both photocatalytic activity and degradation rate. CdS-Zinc-PANI (CZP) and CdS-TiO₂-PANI(CTP) nanocomposites show entrapment at the surface defects of Zinc and TiO₂ nanoparticles due to the demolition of unfavorable electron kinetics, and by reducing the charge recombination, greater photocatalytic activity than CdS-PANI (CP) with the same nanoparticle loading was achieved. With repeated use, the photocatalysts’ efficiency dropped very little, hinting that they may be used to remove organic pollutants from water. The photocatalytic activity of CZP and CTP photocatalytic membranes was greater when compared to CdS-PANI, which may be due to the good compatibility between CdS and Zinc and TiO₂, as well efficient charge carrier separation. PANI can also increase the split-up of photo-excited charge carriers and extend the absorption zone when combined with these nanoparticles. As a result, the development of outrageous performance photocatalysts and their potential uses in ecological purification and solar power conversion has been facilitated. The novelty of this article is to present the degradation of AB-29 Dye using nanocomposites with polymers and study the enhanced degradation rate. Few studies have been carried out on polymer nanocomposites and their application in the degradation of AB-29 dyes and remediation of water purposes. Nanoparticle CdS is a very effective photocatalyst, commonly used for water purification along with nanoparticle ZnS and TiO₂; but cadmium ion-leaching makes it ineffective for practical and commercial use. In the present work, we have reduced the leaching of hazardous cadmium ions by trapping them in a polyaniline matrix, hence making it suitable for commercial use. We have embedded ZnS and TiO₂ along with CdS in a polyaniline matrix and compared their photocatalytic activity, stability, and reusability, proving our nano-composites suitable for commercial purposes with enhanced activities and stabilities, which is a novelty. All synthesized nanocomposites are active within the near-ultraviolet to deep infrared (i.e., 340–850 nm). This gives us full efficiency of the photocatalysts in the sunlight and further proves the commercial utility of our nanocomposites.

Adsorption of Sodium Diclofenac in Functionalized Palygoskite Clays

The effects of acid and organo-functionalizations on the surface of Brazilian palygorskite clay was investigated, evaluating its potential in the adsorptive capacity of the drug sodium diclofenac present in wastewaters. The modifications on the clay structure were investigated by X-ray diffraction, X-ray fluorescence, thermogravimetric, differential thermal analysis, Fourier transform infrared spectroscopy, surface area by N₂ adsorption (77.5 K) and Zeta potential. The experimental design was carried out to find the best conditions for the adsorption tests, in which concentration, mass and pH were significant. In the kinetic study, the pseudo-second-order model better described the adsorption process for acid and organo-functionalized samples. Such results indicate that the adsorption behavior probably occurs due to the phenomenon of chemisorption. Regarding the adsorption isotherms, the Langmuir model was the one that best adjusted both the experimental data of acid and the organo-functionalized samples, whose maximum adsorption capacity were 179.88 and 253.34 mg/g, respectively. This model also indicates that the sodium diclofenac is adsorbed to monolayers homogeneously through chemisorption. In general, the studied clays proved to be suitable adsorbents for the removal of sodium diclofenac.

A reusable visible driven N and C-N doped TiO2 magnetic nanocomposites for photodegradation of direct red 16 azo dye in water and wastewater

The visible active N-doped TiO₂/ZnFe₂O₄ (urea-TiO₂/ZnFe₂O₄) and CN-codoped TiO₂/ZnFe₂O₄ (L-asparagine-TiO₂/ZnFe₂O₄) nanocomposites were successfully synthesized by the sol-gel-hydrothermal method for direct red 16 (DR16) photodegradation. Their properties of the prepared nanocomposites were analysed using XRD, FT-IR, FE-SEM, EDX, DRS and PL tests. The DRS and PL results confirmed a narrow band-gap energy and low recombination rate of photo-produced electron and hole pairs, respectively. The effect of adding various dopant agents (urea and L-asparagine) with different loadings and magnetic nanoparticle (ZnFe₂O₄) into TiO₂ sol on the photodegradation of DR16 was also evaluated. As a result, the L-asparagine (2 wt. %)-TiO₂/ZnFe₂O₄ is the best photocatalyst compared to the other modified TiO₂ nanocomposites due to its narrow band gap and high quantum efficiency. The catalyst concentration (1-2 g/L), DR16 concentration (25-45 ppm), initial pH (4-10), and irradiation time (30-90 min) as numerical variables were also considered for photocatalytic process analysis and moulding by central composite design (CCD). The increase in the pH and dye concentration reduces the photodegradation efficiency while irradiation time and catalyst concentration effectively improved its photodegradation efficiency. The DR16 was completely removed at 25 ppm of DR16, initial pH of 4 and 1.5 g/L of photocatalyst after 90-min irradiation. The photoactivity test was also repeated four times by reused L-asparagine-TiO₂/ZnFe₂O₄ photocatalyst at optimum conditions. The decrease of dye degradation and loss of photocatalyst were not significant which was approved by the good performance and high recovery capability of the prepared nanocomposite.

Combined Analytical Study on Chemical Transformations and Detoxification of Model Phenolic Pollutants during Various Advanced Oxidation Treatment Processes

Advanced oxidation processes (AOPs) have been introduced to deal with different types of water pollution. They cause effective chemical destruction of pollutants, yet leading to a mixture of transformation by-products, rather than complete mineralization. Therefore, the aim of our study was to understand complex degradation processes induced by different AOPs from chemical and ecotoxicological point of view. Phenol, 2,4-dichlorophenol, and pentachlorophenol were used as model pollutants since they are still common industrial chemicals and thus encountered in the aquatic environment. A comprehensive study of efficiency of several AOPs was undertaken by using instrumental analyses along with ecotoxicological assessment. Four approaches were compared: ozonation, photocatalytic oxidation with immobilized nitrogen-doped TiO₂ thin films, the sequence of both, as well as electrooxidation on boron-doped diamond (BDD) and mixed metal oxide (MMO) anodes. The monitored parameters were: removal of target phenols, dechlorination, transformation products, and ecotoxicological impact. Therefore, HPLC–DAD, GC–MS, UHPLC–MS/MS, ion chromatography, and 48 h inhibition tests on Daphnia magna were applied. In addition, pH and total organic carbon (TOC) were measured. Results show that ozonation provides by far the most suitable pattern of degradation accompanied by rapid detoxification. In contrast, photocatalysis was found to be slow and mild, marked by the accumulation of aromatic products. Preozonation reinforces the photocatalytic process. Regarding the electrooxidations, BDD is more effective than MMO, while the degradation pattern and transformation products formed depend on supporting electrolyte.

Comparison Study on Sonodirect and Sonoalternate Current Electrocoagulation Process for Domestic Wastewater Treatment

Nowadays, there is a problem related to wastewater handling which is released from different activities. The electrocoagulation method has been a dominant treatment method for wastewater treatment. There are different forms of electrocoagulation methods for wastewater treatment. Nevertheless, there was no comparison made for the removal efficiency of the sonoalternate current (SAC), alternate current (AC), sonodirect current (SDC), and direct current (DC) electrocoagulation process. The efficiency of electrocoagulation methods was compared for their removal of chemical oxygen demand (COD) from Jimma University domestic wastewater. Batch Reactor DC/AC electrocoagulation cell was used to determine the removal efficiency. During the comparison, the response surface methodology (RSM) was used to analyze and optimize the data taken from the laboratory. Besides, ANOVA was used to analyze the interaction effects of different parameters. The removal of COD from domestic wastewater was achieved with DCE, ACE, SDCE, and SACE which were 82.6%, 86.58%, 88.6%, and 92.5%, respectively, under optimal experimental conditions. From the finding, SACE was more successful at removing % COD than the DCE, ACE, and SDCE methods. For DCE and SDCE, the formation of an impermeable oxide layer at the cathode and the occurrence of corrosion at the anode due to oxidation made the COD removal process less efficient compared with SACE processes. From the experimental results it can be concluded that the SACE has the lowest power consumption and higher process efficiency than the other EC methods and can be a promising solution for removing pollutants from domestic wastewater.

Synthesis of carbon-based nanomaterials and their application in pollution management

With the fast development of industry, large amounts of organic and inorganic pollutants are inevitably released into the natural environment, which results in the pollution of the environment and are thereby dangerous to human health. The efficient elimination of these pollutants is crucial to environment protection and human health. The high sorption capacity of carbon-based materials and high photocatalytic ability of carbon-based composites result in the application of carbon-based materials in environmental pollution cleanup. In this review article, we summarized recent studies on the synthesis of carbon-based materials, and their application in the sorption of organic and inorganic pollutants, the photocatalytic degradation of organic pollutants, and the in situ photocatalytic reduction-solidification of heavy metal ions. The sorption method is useful to remove pollutants from aqueous solutions. The sorption-photocatalytic degradation of organic pollutants is applicable, especially at low concentrations, whereas the catalytic reduction of metal ions is the best method for the in situ immobilization of high valent metal ions under complicated conditions. The interaction mechanism is discussed using advanced spectroscopy analysis and theoretical calculations, and at the end the challenges in the future are described.

A smart enzyme reactor based on a photo-responsive hydrogel for purifying water from phenol contaminated sources

In this paper, a smart enzyme reactor (SER) was synthesized using immobilized tyrosinase (Tyr) in a photo-responsive hydrogel via a polydopamine-assisted self-assembly strategy for purifying water from phenol contaminated water. PDA was not only utilized as a binder between Tyr and the hydrogel to prevent the leakage of Tyr with relatively high enzymatic activity from the SER, but also acted as a light absorber to trigger the hydrophilic/hydrophobic switching of PNIPAm hydrogels to realize the efficient reclamation of clean water. Experimental results showed that the SER maintained a well-defined porous structure with excellent elasticity, which was beneficial for water transport and enzyme accessibility. And the stability and reusability of Tyr in the degradation of phenol were all improved. Furthermore, clean water could be reclaimed completely and facilely by light irradiation after enzymatic remediation in the SER.

CQDs/ZnO composites based on waste rice noodles: preparation and photocatalytic capability

To provide a low-cost photocatalyst and new methodology for the utilization of waste rice noodle (WRN), a carbon quantum dots/zinc oxide (CQDs/ZnO) composite using WRN as the raw material was synthesized and characterized. The CQDs/ZnO composite based on WRN exhibited a highly efficient photocatalytic degradation effect on various organic pollutants and could be a good alternative for commercial ZnO. For methylene blue, the CQDs/ZnO composite showed a good degradation rate of 99.58% within 40 min, a high degradation rate constant of 0.2630 min⁻¹, and could be recycled and reused for ten photocatalytic cycles without an appreciable decrease in the degradation effect, which was much better than that of commercial ZnO. The resulting CQDs/ZnO composite also displayed a nice photocatalytic degradation effect on other common organic pollutants, such as malachite green, methyl violet, basic fuchsin, rhodamine B, aniline and tetracycline. In particular, it could achieve excellent photocatalytic degradation on malachite green with an extremely high degradation rate constant of 1.9260 min⁻¹. Besides, the CQDs/ZnO composite could also be used to control the pollution of tetracycline or aniline. The introduction of CQDs based on WRN to ZnO resulted in efficient electron–hole pair separation and enabled more photogenerated electrons to reduce O₂ and more photogenerated holes to oxidize H₂O, which caused stronger abilities in producing radicals (such as O₂˙⁻ and ˙OH) and a better photocatalytic degradation effect to organic pollutants.

A CQDs/ZnO composite based on waste rice noodles displayed a highly efficient photocatalytic degradation effect on various organic pollutants.

Homogeneous photocatalytic degradation of azo dye Reactive Black 5 using Fe(III) ions under visible light

Efficient and cost-effective method to destroy complex dyes is warranted to combat increasing water pollution. In the present study, homogeneous photocatalytic oxidation (PCO) of Reactive Black 5 (RB5) dye was studied using ferric ions (Fe(III)) under visible light (VL) irradiation and sunlight (SL). In the presence of 5 mM ferric ions and at pH 2.6, more than 80% of initial 20 mg/L RB5 was decolourized in 60 min under artificial VL. Decolourization followed pseudo first-order kinetics with the reaction rate constant 0.0356 min^-1. 79% of initial COD was removed at the end of 60 min, suggesting mineralization of RB5 as the main cause of decolourization. Using similar experimental conditions under SL, more than 90% RB5 was decolourized in 15 min with an almost 10-fold increase in the reaction rate constant (0.34 min^-1). Rate and extent of RB5 destruction significantly decreased in the presence of •OH scavenger indicating photoreduction of Fe-hydroxo species and generation of •OH as the main mechanism of RB5 degradation. RB5 removal increased from ca. 30% to 84% with the increase in Fe(III) concentration from 0.5 to 5 mM. The corresponding 1st-order rate constants increased linearly from 0.006 to 0.036 min^-1. RB5 degradation decreased linearly (R² = 0.98) from 91.7% to 63.3% with the increase in initial RB5 concentration from 10 to 40 mg/L. Fe(III) induced homogenous PCO appears to be a reliable and low-cost method of advanced oxidation without the need for costly reagent such as H₂O₂.

Upcycling discarded cellulosic surgical masks into catalytically active freestanding materials

ABSTRACT

The COVID-19 pandemic outbreak has resulted in the massive fabrication of disposable surgical masks. As the accumulation of discarded face masks represents a booming threat to the environment, here we propose a solution to reuse and upcycle surgical masks according to one of the cornerstones of the circular economy. Specifically, the non-woven cellulosic layer of the masks is used as an environmentally sustainable and highly porous solid support for the controlled deposition of catalytically active metal-oxide nanoparticles. The native cellulosic fibers from the surgical masks are decorated by titanium dioxide (TiO₂), iron oxide (Fe_xO_y), and cobalt oxide (CoO_x) nanoparticles following a simple and scalable approach. The abundant surface -OH groups of cellulose enable the controlled deposition of metal-oxide nanoparticles that are photocatalytically active or shown enzyme-mimetic activities. Importantly, the hydrophilic highly porous character of the cellulosic non-woven offers higher accessibility of the pollutant to the catalytically active surfaces and high retention in its interior. As a result, good catalytic activities with long-term stability and reusability are achieved. Additionally, developed free-standing hybrids avoid undesired media contamination effects originating from the release of nanoscale particles. The upcycling of discarded cellulosic materials, such as the ones of masks, into high-added-value catalytic materials, results an efficient approach to lessen the waste´s hazards of plastics while enhancing their functionality. Interestingly, this procedure can be extended to the upcycling of other systems (cellulosic or not), opening the path to greener manufacturing approaches of catalytic materials.

GRAPHICAL ABSTRACT

A novel approach to upcycle discarded cellulosic surgical masks is proposed, providing a solution to reduce the undesired accumulation of discarded face masks originating from the COVID-19 pandemic. The non-woven cellulosic layer formed by fibers is used as solid support for the controlled deposition of catalytically active titanium dioxide (TiO₂), iron oxide (Fe_xO_y), and cobalt oxide (CoO_x) nanoparticles. Cellulosic porous materials are proven useful for the photocatalytic decomposition of organic dyes, while their peroxidase-like activity opens the door to advanced applications such as electrochemical sensors. The upcycling of cellulose nonwoven fabrics into value-added catalytic materials lessens the waste´s hazards of discarded materials while enhancing their functionality.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10570-022-04441-9.