Design and Preparation of Biomass-Derived Activated Carbon Loaded TiO2 Photocatalyst for Photocatalytic Degradation of Reactive Red 120 and Ofloxacin

Simultaneous removal of E1, E2, EE2 and levonorgestrel from water using TiO2 catalyst anchored on activated carbon: Processes optimization, materials characterization, and assessment of the estrogenicity reduction

Removal of estrogen hormones from water matrices is crucial owing to its adverse effects on aquatic ecosystems and human health. The present investigation applies an advanced approach to assess the effectiveness of combined processes (adsorption and visible-light-driven photo-degradation) for simultaneous removal of estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), and levonorgestrel (LEVO) in water, applying TiO2-activated carbon composite selected through design of experiment (DoE) for process optimization. Based on a central composite rotatable design (CCRD), composites were synthesized with percentages of activated carbon (AC) ranging from 2.93% to 17.07% (wt.) and calcination temperatures between 259 and 541 °C. The composite with the best performance TiO2-AC15%-541 (15% wt. AC, calcined at 541 °C), achieved a total removal of 98.3 ± 1.15% for E1, 99.0 ± 1% for E2, 99.3 ± 1.15% for EE2, and 96.0 ± 2.65% for LEVO at the initial concentration of 100 μg L-1 under simulated solar irradiation. Further optimization using once more CCRD involved three independent variables: pH; hormone concentration/TiO2-AC15%-541 loading ratio; and the intensity of simulated solar irradiation. Under optimized conditions (pH 2.64, hormone concentration/TiO2-AC15%-541 loading ratio of 3.8 mg g-1, and irradiation intensity of 41 W m-2 UV-A), the TiO2-AC15%-541 composite removed 99.8% of E1, 99.8% of E2, 99.0% of EE2, and 92.1% of LEVO. Furthermore, the process achieved a 99.9% reduction in estrogenic activity, assessed with yeast estrogen screen (YES) assay. These results demonstrate that TiO2-AC15%-541 is an efficient and cost-effective remediation agent for treating mixed estrogen compounds in water, with significant potential for commercial applications.

Physicochemical properties and performance of non-woody derived biochars for the sustainable removal of aquatic pollutants: A systematic review

Biochar is a carbon-rich material produced from the partial combustion of different biomass residues. It can be used as a promising material for adsorbing pollutants from soil and water and promoting environmental sustainability. Extensive research has been conducted on biochars prepared from different feedstocks used for pollutant removal. However, a comprehensive review of biochar derived from non-woody feedstocks (NWF) and its physiochemical attributes, adsorption capacities, and performance in removing heavy metals, antibiotics, and organic pollutants from water systems needs to be included. This review revealed that the biochars derived from NWF and their adsorption efficiency varied greatly according to pyrolysis temperatures. However, biochars (NWF) pyrolyzed at higher temperatures (400-800 °C) manifested excellent physiochemical and structural attributes as well as significant removal effectiveness against antibiotics, heavy metals, and organic compounds from contaminated water. This review further highlighted why biochars prepared from NWF are most valuable/beneficial for water treatment. What preparatory conditions (pyrolysis temperature, residence time, heating rate, and gas flow rate) are necessary to design a desirable biochar containing superior physiochemical and structural properties, and adsorption efficiency for aquatic pollutants? The findings of this review will provide new research directions in the field of water decontamination through the application of NWF-derived adsorbents.

Bio-based matrix photocatalysts for photodegradation of antibiotics

Antibiotics development during the last century permitted unprecedent medical advances. However, it is undeniable that there has been an abuse and misuse of antimicrobials in medicine and cosmetics, food production and food processing, in the last decades. The pay toll for human development and consumism is the emergence of extended antimicrobial resistance and omnipresent contamination of the biosphere. The One Health concept recognizes the interconnection of human, environmental and animal health, being impossible alter one without affecting the others. In this context, antibiotic decontamination from water-sources is of upmost importance, with new and more efficient strategies needed. In this framework, light-driven antibiotic degradation has gained interest in the last few years, strongly relying in semiconductor photocatalysts. To improve the semiconductor properties (i.e., efficiency, recovery, bandgap width, dispersibility, wavelength excitation, etc.), bio-based supporting material as photocatalysts matrices have been thoroughly studied, exploring synergetic effects as operating parameters that could improve the photodegradation of antibiotics. The present work describes some of the most relevant advances of the last 5 years on photodegradation of antibiotics and other antimicrobial molecules. It presents the conjugation of semiconductor photocatalysts to different organic scaffolds (biochar and biopolymers), then to describe hybrid systems based on g-C3N4 and finally addressing the emerging use of organic photocatalysts. These systems were developed for the degradation of several antibiotics and antimicrobials, and tested under different conditions, which are analyzed and thoroughly discussed along the work.

Ophiorrhiza mungos-Mediated Silver Nanoparticles as Effective and Reusable Adsorbents for the Removal of Methylene Blue from Water

Green synthesis of silver nanoparticles (AgNPs) using a plant extract has attracted significant attention in recent years. It is found as an alternative for other physicochemical approaches because of its simplicity, low cost, and eco-friendly rapid steps. In the present study, Ophiorrhiza mungos (Om)-mediated AgNPs have been shown to be effective bioadsorbents for methylene blue (MB) dye removal (88.1 ± 1.74%) just after 1 h at room temperature in the dark from an aqueous medium for the first time. Langmuir and Freundlich isotherms fit the experimental results having the correlation coefficient constants R2 = 0.9956 and R2 = 0.9838, respectively. From the Langmuir fittings, the maximum adsorption capacity and adsorption intensity were found to be 80.451 mg/g and 0.041, respectively, indicating the excellent performance and spontaneity of the process. Taking both models under consideration, interestingly, our findings indicated a fairly cooperative multilayer adsorption that might have been governed by chemisorption and physisorption, whereas the adsorption kinetics followed the pseudo-second-order kinetics mechanism. The positive and low values of enthalpy (ΔH0 = 4.91 kJ/mol) confirmed that adsorption is endothermic and physical in nature; however, the negative free energy and positive entropy value (ΔS0 = 53.69 J/mol K) suggested that the adsorption is spontaneous. The biosynthesized adsorbent was successfully reused up to the fifth cycle. A proposed reaction mechanism for the adsorption process of MB dye onto Om-AgNPs is suggested. The present study may offer a novel finding such as an effective and sustainable approach for the removal of MB dye from water using biosynthesized Om-AgNPs as reusable adsorbents at a comparatively faster rate at a low dose for industrial applications.

Natural waste-derived nano photocatalysts for azo dye degradation

Due to their widespread application in water purification, there is a significant interest in synthesising nanoscale photocatalysts. Nanophotocatalysts are primarily manufactured through chemical methods, which can lead to side effects like pollution, high-energy usage, and even health issues. To address these issues, "green synthesis" was developed, which involves using plant extracts as reductants or capping agents rather than industrial chemical agents. Green fabrication has the benefits of costs less, pollution reduction, environmental protection and human health safety, compared to the traditional methods. This article summarises recent advances in the environmentally friendly synthesis of various nanophotocatalysts employed in the degradation of azo dyes. This study compiles critical findings on natural and artificial methods to achieve the goal. Green synthesis is constrained by the time and place of production and issues with low purity and poor yield, reflecting the complexity of plants' geographical and seasonal distributions and their compositions. However, green photocatalyst synthesis provides additional growth opportunities and potential uses.

Solar light driven enhanced photocatalytic treatment of azo dye contaminated water based on Co-doped ZnO/ g-C3N4 nanocomposite

The current research concentrated on the Co-precipitation synthesis of g-C3N4 (CN), ZnO, ZnO/CN, and Co-doped ZnO/CN nanocomposite, as well as the solar light enhanced photocatalytic treatment of Reactive Red 120 (RR120) from genuine wool textile effluent. The 3D flower-like structure of Co-doped ZnO distributed on the surface of CN thin sheets, according to structural studies employing XRD and SEM examinations Electrochemical experiments exhibited that the Co-doped ZnO/CN nanocomposite has a large electroactive surface area. The optical band-gap values of CN, ZnO, ZnO/CN, and Co-doped ZnO/CN nanocomposites were 2.68, 3.13, 2.38, and 2.23 eV, respectively, according to optical characterizations. The synergistic effects and heterojunction produced by Co-doped ZnO and CN can be linked to the narrow gap in nanocomposites. After 75, 60, 50, and 40 min of exposure to solar light, photocatalytic degradation assays for 250 mL of 20 mg/L RR120 solution in the presence of CN, ZnO, ZnO/CN, and Co-doped ZnO/CN nanocomposites demonstrated 100% dye treatment. The applicability of photocatalysts for decolorization of 250 mL of 10 mg/L RR120 prepared from actual wool textile wastewater was investigated, and the results showed that Co-doped ZnO/CN nanocomposites for treatment of RR120 from actual wool textile wastewater were highly efficient at photocatalytic degradation.

Photocatalytic Performance of Sol-Gel Prepared TiO2 Thin Films Annealed at Various Temperatures

Titanium dioxide (TiO2) in the form of thin films has attracted enormous attention for photocatalysis. It combines the fundamental properties of TiO2 as a large bandgap semiconductor with the advantage of thin films, making it competitive with TiO2 powders for recycling and maintenance in photocatalytic applications. There are many aspects affecting the photocatalytic performance of thin film structures, such as the nanocrystalline size, surface morphology, and phase composition. However, the quantification of each influencing aspect needs to be better studied and correlated. Here, we prepared a series of TiO2 thin films using a sol-gel process and spin-coated on p-type, (100)-oriented silicon substrates with a native oxide layer. The as-deposited TiO2 thin films were then annealed at different temperatures from 400 °C to 800 °C for 3 h in an ambient atmosphere. This sample synthesis provided systemic parameter variation regarding the aspects mentioned above. To characterize thin films, several techniques were used. Spectroscopic ellipsometry (SE) was employed for the investigation of the film thickness and the optical properties. The results revealed that an increasing annealing temperature reduced the film thickness with an increase in the refractive index. Atomic force microscopy (AFM) was utilized to examine the surface morphology, revealing an increased surface roughness and grain sizes. X-ray diffractometry (XRD) and UV-Raman spectroscopy were used to study the phase composition and crystallite size. The annealing process initially led to the formation of pure anatase, followed by a transformation from anatase to rutile as the annealing temperature increased. An overall enhancement in crystallinity was also observed. The photocatalytic properties of the thin films were tested using the photocatalytic decomposition of acetone gas in a home-built solid (photocatalyst)-gas (reactant) reactor. The composition of the gas mixture in the reaction chamber was monitored using in situ Fourier transform infrared spectroscopy. Finally, all of the structural and spectroscopic characteristics of the TiO2 thin films were quantified and correlated with their photocatalytic properties using a correlation matrix. This provided a good overview of which film properties affect the photocatalytic efficiency the most.

Biomass-derived carbon deposited TiO2 nanotube photocatalysts for enhanced hydrogen production

In this study, titanium oxide nanotubes (TiO₂NTs) were deposited on the surface of activated carbon (AC) by varying the wt% of AC. The physicochemical properties of synthesized TiO₂NTs-AC nanocomposites were analysed by various characterization techniques such as XRD, FT-IR, Raman, DRUV-vis, HR-TEM, XPS, PL, and N₂ physisorption. The FT-IR, EDX, and XPS analyses proved the existence of interaction between AC and TiO₂NTs. This study found that as the content of AC increases, the surface area and pore volume increase while the energy bandgap decreases. The TiO₂NTs-AC nanocomposite with 40% AC exhibited a surface area of 291 m² g^-1, pore volume of 0.045 cm³ g^-1 and half pore width = 8.4 Å and had a wide band gap energy (3.15 eV). In addition, the photocatalytic application of the prepared nanocomposites for photocatalytic H₂ production was investigated. The H₂ was produced via photo-reforming in the presence of a sacrificial agent (methanol) under sunlight irradiation. It was found that the prepared TiO₂NTs-AC nanocomposite with 40% AC acted as an efficient photocatalyst for aqueous-methanol reforming under various optimization conditions. Approximately 18 000 μmol^-1 hydrogen gas was produced via aqueous-methanol reforming under optimized conditions (catalyst dose = 100 mg, temperature = 25 °C, time = 12 hours, vol. of methanol = 20% (v/v), and pH = 7). The reusability of the TiO₂NTs-AC nanocomposite was also investigated for 5 consecutive cycles, and the results suggested only a slight decline in efficiency even after the fifth cycle. This study demonstrates the ability of an activated carbon deposited TiO₂NT catalyst to produce hydrogen effectively under sunlight.

Novel environmental method for enhanced biodegradation of contaminated wastewater via immobilizing nanoparticles on a new bacterial strain isolated industrial textile

Biological processes comprising bacteria, fungi, yeast, and algae received increasing interest for dye degradation due to their cost-effectiveness and eco-friendly nature. Hence, the current study aims to investigate the ability of the photocatalytic performance of N-S co-doped anatase TiO₂ (NSTO) nanoparticles immobilized on isolated industrial textile bacteria (ITB) for degradation of basic blue 41 (BB 41). To prove the effect of improving the surface area of NSTO, NSTO also was immobilized on glass balls (NSTO-GB). NSTO nanoparticles were synthesized using sol-gel methods, and characterization of NSTO and NSTO-GB were measured using SEM, TEM, XPS, and DLS analysis. The results showed that the average size of NSTO was 50-60 nm. Moreover, the morphology and surface microstructure of ITB and ITB-NSTO were determined by the SEM, XPS technique. According to the results, ITB has a rod structure, NSTO nanoparticles are placed on the surface of ITB. However, NSTO was attached to the surface of ITB with the hydroxyl group. The ITB-NSTO indicated a higher BB 41 degradation yield (99%) than pure NSTO (65%) and ITB (74%). The effect of different factors was evaluated on biodegradation by ITB-NSTO. The high biodegradation was obtained in ITB (10 mg), NSTO (50 mg), BB41 (50 ppm), and pH 11. The GC-Mass, LC-Mass, and FT-IR analysis, which monitored the BB 41 degradation efficiency, proved the degradation efficiency by 99%. In the following, the toxicities of BB 41 solution before and after degradation were accessed through the brine shrimp lethality assay (BSLA) and seed germination assay, which displayed a considerable reduction in BB 41 after degradation. Toxicity results exhibited that ITB-NSTO has potential for industrial application.

Recycling Carbon Fiber from Carbon Fiber-Reinforced Polymer and Its Reuse in Photocatalysis: A Review

Driven by various environmental and economic factors, it is emerging to adopt an efficient and sustainable strategy to recycle carbon fibers (rCFs) from carbon fiber-reinforced polymer (CFRP) wastes and reuse them in high-value applications. This review summarized the latest progress of CFRP waste recycling methods (including mechanical, chemical, and thermal methods), discussed their advantages and disadvantages, influence parameters and possible environmental effects, and their potential effects on the mechanical and surface chemical properties of rCFs. In addition, the latest optimization schemes of leading recycling technologies were detailed. According to the literature, CFs are the key points in the structural support of semiconductor-based recyclable photocatalytic systems and the enhancement of performance, which means that rCFs have high reuse potential in sustainable photocatalysis. Therefore, this paper also emphasized the possibility and potential value of reusing recovered fibers for developing recyclable photocatalytic products, which may be a new way of reuse in environmental purification often ignored by researchers and decision-makers in the field of CFs.

Highly-Efficient and Visible Light Photocatalytical Degradation of Organic Pollutants Using TiO2-Loaded on Low-Cost Biomass Husk

A composite composing of TiO₂ nanoparticles load on biomass rice husk (RH) is developed by directly growing TiO₂ nanoparticles on RH. The in-situ growth of the nanocrystals on RH is achieved by a low-cost and one-step homogeneous precipitation. Rapid hydrolysis proceeds at 90 °C by using ammonium fluotitanate and urea to facilitate the selective growth of TiO₂. The method provides an easy access to the TiO₂-RH composite with a strong interaction between TiO₂ nanoparticles and the underlying RH. The structure and composition of TiO₂-RH are characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and UV-vis absorption spectroscopy. TiO₂ nanoparticles-RH exhibits a good photocatalytic degradation of methyl orange. The results show that 92% of methyl orange (20 mg L^-1) can be degraded within three hours in visible light. The catalytic activity of the composite is not reduced after 6 cycles, and it still reaches 81% after 6 cycles. The enhanced performance is ascribed to the suitable particle size the good dispersibility. It is expected that the high photocatalytical performance and the cost-effective composite presented here will inspire the development of other high-performance photocatalysts.

Nanohybrid catalysts with porous structures for environmental remediation through photocatalytic degradation of emerging pollutants

Water supplies have been seriously challenged by new emerging pollutants, which are difficult to remove by traditional wastewater treatment. Thus, new technologies such as catalytic advanced oxidation processes have merged as suitable solutions; however, the drawbacks of typical catalysts limit their application. To overcome this issue, new materials with enhanced textural properties have been developed, showing that their porosity and chemical nature influence their potential as a catalyst. Herein, the recent progress in highly porous catalysts and their suitable deployment to effectively nano-remediate the polluted environmental matrices are reviewed in detail. First, following a brief introduction, several environmental pollutants of emerging concerns from different sectors, including pharmaceutical residues, endocrine-disrupting chemicals (EDCs), pesticides, and hazardous dyes are also introduced with relevant examples. To effectively tackle the sustainable remediation of emerging pollutants, this work also focuses on the multifunctional features of nanohybrid porous materials that act as catalysts constructs to degrade emerging pollutants. The influence of surface reactive centers, stability, bandgap energies, light absorption capacities, and pollutants adsorption capacities are also discussed. Successful examples of the employment of nanohybrid porous catalysts for the degradation of pharmaceutical pollutants, EDCs, pesticides, and hazardous dyes are summarized. Finally, some challenges faced by nanohybrid porous materials to achieve their potential application as advanced catalysts for environmental remediation have been identified and presented herein.

Preparation and Characterization of Chitosan/TiO2 Composite Membranes as Adsorbent Materials for Water Purification

As it is used in all aspects of human life, water has become more and more polluted. For the past few decades, researchers and scientists have focused on developing innovative composite adsorbent membranes for water purification. The purpose of this research was to synthesize a novel composite adsorbent membrane for the removal of toxic pollutants (namely heavy metals, antibiotics and microorganisms). The as-synthesized chitosan/TiO₂ composite membranes were successfully prepared through a simple casting method. The TiO₂ nanoparticle concentration from the composite membranes was kept low, at 1% and 5%, in order not to block the functional groups of chitosan, which are responsible for the adsorption of metal ions. Nevertheless, the concentration of TiO₂ must be high enough to bestow good photocatalytic and antimicrobial activities. The synthesized composite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and swelling capacity. The antibacterial activity was determined against four strains, Escherichia coli, Citrobacter spp., Enterococcus faecalis and Staphylococcus aureus. For the Gram-negative strains, a reduction of more than 5 units log CFU/mL was obtained. The adsorption capacity for heavy metal ions was maximum for the chitosan/TiO₂ 1% composite membrane, the retention values being 297 mg/g for Pb²⁺ and 315 mg/g for Cd²⁺ ions. These values were higher for the chitosan/TiO₂ 1% than for chitosan/TiO₂ 5%, indicating that a high content of TiO₂ can be one of the reasons for modest results reported previously in the literature. The photocatalytic degradation of a five-antibiotic mixture led to removal efficiencies of over 98% for tetracycline and meropenem, while for vancomycin and erythromycin the efficiencies were 86% and 88%, respectively. These values indicate that the chitosan/TiO₂ composite membranes exhibit excellent photocatalytic activity under visible light irradiation. The obtained composite membranes can be used for complex water purification processes (removal of heavy metal ions, antibiotics and microorganisms).

Activated Carbon-Loaded Titanium Dioxide Nanoparticles and Their Photocatalytic and Antibacterial Investigations

Activated carbon doping TiO2 nanoparticles were synthesised by zapota leaf extract using the co-precipitation method. The bio-constituents of plant compounds were used in the reactions of stabilization and reductions. The carbon loading on the TiO2 nanoparticles was characterised by XRD, FTIR, UV-DRS, SEM with EDX, and TEM analysis. The loading of activated carbon onto the TiO2 nanoparticles decreased the crystallite size and optical bandgap, and their doping improved the surface structure of AC/TiO2 nanoparticles. Mesoporous/microporous instability was remodified from the activated carbon, which was visualised using SEM and TEM analysis, respectively. The photocatalytic dye degradation of Rh-B dye was degraded in TiO2 and AC/TiO2 nanoparticles under visible light irradiation. The degradation efficiencies of TiO2 and AC/TiO2 nanoparticles were 73% and 91%, respectively. The bacterial abilities of TiO2 and AC/TiO2 nanoparticles were examined by E. coli and S. aureus. The water reclamation efficiency and bactericidal effect of TiO2 and AC/TiO2 nanoparticles were examined via catalytic dye degradation and bacterial efficiency of activated carbon-doped titanium dioxide nanoparticles.

Designing Novel Strategy to Produce Active Nanohybrids in Sunlight for Purification of Water Based on Inorganic Nanolayers, Magnetic Nanocomposites and Organic Species

Energy and water related problems have attracted strong attention from scientists across the world because of deficient energy and water pollution. Following this line, new strategy depended on preparing nanolayers of Al/Zn and magnetic nanoparticles of cobalt iron oxides nanocomposite in addition to long chains of hydrocarbons of stearic acid to be used as roofs, fillers and pillars; respectively, to design optical-active nanohybrids in sunlight for removing the colored pollutants from water in few minutes. By using long chains of hydrocarbons of stearic acid, X-ray diffraction (XRD) results and TEM images showed expansion of the interlayered spacing from 0.76 nm to 2.02 nm and insertion of magnetic nanoparticles among the nanolayers of Al/Zn. The optical properties and activities showed that the nanohybrid structure based on zinc oxide led to clear reduction of the band gap energy from 3.3 eV to 2.75 eV to be effective in sunlight. Photocatalytic degradation of the dye of acid green 1 confirmed the high activity of the prepared zinc oxide nanohybrids because of a complete removal of the dye after ten minutes in sunlight. Finally, this strategy was effective for producing photo-active nanohybrids for using renewable and non-polluting energy for purifying water.

Facile Synthesis of Microporous Ferrocenyl Polymers Photocatalyst for Degradation of Cationic Dye

Microporous organic polymers (MOPs) were prepared by condensation reactions from substituent-group-free carbazole and pyrrole with 1,1′-ferrocenedicarboxaldehyde without adding any catalysts. The resultant MOPs were insoluble in common solvent and characterized by FTIR, XPS, TGA and SEM. An N₂ adsorption test showed that the obtained polymers PFcMOP and CFcMOP exhibited Brunauer–Emmett–Teller (BET) surface areas of 48 and 105 m² g⁻¹, respectively, and both polymers possessed abundant micropores. The MOPs with a nitrogen and ferrocene unit could be potentially applied in degrading dye with high efficiency.