Selective adsorption of methylene blue (MB) dye from aqueous mixture of MB and methyl orange (MO) using mesoporous titania (TiO2) – poly vinyl alcohol (PVA) nanocomposite

High-performance adsorption of methylene blue using novel bio-adsorbent based on sargassum fusiforme

Large specific surface area obtained by pyrolyzed biomass is considered as a vital factor in improving the dye adsorption performance. However, pyrolysis would cause the inevitable destruction of the surface functional groups of biomass. Herein, a biomass adsorbent based on sargassum fusiforme without pyrolysis was employed for the removal of methylene blue (MB). Combining the FTIR, XPS, SEM, and BET analysis, sargassum fusiforme bio-adsorbent (SFBA) was found to have low specific surface area whereas rich functional groups, including carboxyl, carbonyl and hydroxyl groups. SFBA presented high adsorption performance towards MB with a maximum adsorption capacity of 1154.05 mg/g, demonstrating that the high adsorption performance could be achieved by abundant functional groups rather than large specific surface area. In this paper, various adsorption parameters including pH, concentration, contact time, and temperature have also been discussed. The results indicated that the kinetic and isotherm models of SFBA followed the pseudo-secondary kinetic model and the Langmuir isotherm model, respectively. The negative thermodynamic parameters showed that the adsorption process is spontaneous and exothermic. The SFBA enriched with functional groups exhibited high adsorption performance as well as simple fabrication, and abundant sources that could provide a novel alternative for the treatment of dye wastewater.

UV-light-responsive Ag/TiO2/PVA nanocomposite for photocatalytic degradation of Cr, Ni, Zn, and Cu heavy metal ions

The rapid growth of industrialization has led to the uncontrolled pollution of the environment, and rapid action is needed. This study synthesized Ag/TiO2/polyvinyl alcohol (PVA) nano photocatalyst for promising light-derived photocatalytic removal of heavy metal ions. The design of experiment (DOE) was used to study the effect of important factors (pH, reaction time, and photocatalyst dosage) to maximize the final performance of the photocatalyst. In the optimized condition, the Ag/TiO2/PVA nano-photocatalyst removed more than 94% of Cr6+ in 180 min, and the efficiency was more than 70% for Cu2+, Zn2+, and Ni2+ metal ions. The adsorption of the heavy metal ions on the photocatalyst was described well with the Langmuir isotherm, while the pseudo-second-order linear kinetic model fitted with the experimental data. The nano-photocatalyst's stability was confirmed after maintaining its performance for five successive runs. The enhanced photocatalytic activity for the heavy metal ions removal can be attributed to the presence of metallic silver nanoparticles (electron transfer and plasmonic fields mechanisms) and PVA, which delayed the recombination of electron-hole. The synthesized ternary Ag/TiO2/PVA nano-photocatalyst showed promising performance for the elimination of heavy metal ions and can be used for environmental remediation purposes.

Fabrication of Fe3O4 core-TiO2/mesoSiO2 and Fe3O4 core-mesoSiO2/TiO2 Double Shell Nanoparticles for Methylene Blue Adsorption: Kinetic, Isotherms and Thermodynamic Characterization

Herein, Fe3O4 core-TiO2/mesoSiO2 and Fe3O4 core-mesoSiO2/TiO2 double shell nanoparticles were prepared by first (R1) and second (R2) routes and applied for the removal of methylene blue. The reported adsorption capacities for R1-0.2, R1-0.4 and R2 samples were 128, 118 and 133 mg.g-1, respectively, which were obtained after 80 min as equilibrium contact time, and pH of 6 using a methylene blue concentration of 200 ppm. The adsorption of methylene blue using the prepared Fe3O4 core-meso SiO2/TiO2 double shell was analyzed by kinetic and isotherms models. In addition, thermodynamic investigations were applied to assess the spontaneous nature of the process. The obtained results confirmed that the pseudo-second order model is well fitted with the adsorption data and the Freundlich-isotherm assumption suggested a multilayer adsorption mechanism. In addition, results of the thermodynamic investigation indicated that ΔG° was in the range of -2.3 to -6.8 kJ/mol for R1-0.2, -2.8 to -6.3 kJ/mol for R1-0.4 and -2.0 to -5.2 kJ/mol for R2. In addition, the ΔH° and ΔS° values were found in the range of 26.4 to 36.19 kJ.mol-1 and 94.9 to 126.3 Jmol-1 K-1, respectively. These results confirm that the surfaces of Fe3O4 core-mesoSiO2/TiO2 and Fe3O4 core-TiO2/mesoSiO2 double shell exhibit a spontaneous tendency to adsorb methylene blue from the aqueous solutions. The achieved performance of Fe3O4 core-meso SiO2/TiO2 and Fe3O4 core-TiO2/meso SiO2 double shell as adsorbent for methylene blue removal will encourage future research investigations on the removal of a broad range of contaminants from wastewater.

Sapo-34 Obtained from Amazonian Flint Kaolin: Influence of Impurities of “Oxidized Fe/Ti” in Synthesis and Its Application in the Removal of Cationic Dye from Water

Non-processed kaolin (flint kaolin) from a mine located in the Capim area (Amazon region, northern Brazil), usually considered as waste, was selected as a source of silicon and aluminum in the synthesis of SAPO-34. This is a molecular sieve and cationic exchanger chosen for tests focusing on the removal of methylene blue in aqueous solutions, which is a cationic dye widely used by textile industries in Brazil. The results revealed that the SAPO-34 has been successfully synthesized with typical cubic morphology, good crystallinity (>90%), and thermal stability (~998 °C). Although the oxidized Fe/Ti impurities contained in the flint kaolin affect the degree of crystallinity of the zeolitic product, its adsorptive properties are not significantly affected, which demonstrates the excellent adsorption results (pH = 11; % removal > 90%). It proved to be an adsorbent with considerable adsorption capacity (9.83 mg·g−1). The pH test confirmed the acidic surface characteristics (pH solution 2–4; ↓ removal), and the kinetic model that best fitted the experimental data was pseudo-second-order, with R2 = 0.998 (kinetics controlled by chemisorption).

The highly efficient simultaneous removal of Pb2+ and methylene blue induced by the release of endogenous active sites of montmorillonite

The inherent periodic structure of montmorillonite limits the adsorption capacity of its endogenous active units such as Si-O tetrahedron and Al-O octahedron for pollutants. The high-intensity ultrasound method was used to release these active units and the layer-by-layer assembly was adopted to prepare carbon@chitosan@montmorillointe microsphere adsorbent (C@CS@Mt) to give full play to the adsorption capacity of montmorillonite. The montmorillonite nanosheet exhibited good hole-making ability, resulting in high surface area, pore volume and pore diameter of microspheres. Benefitting from the release of active sites in Si-O tetrahedron and Al-O octahedron of montmorillonite nanosheets, the adsorption capacity of C@CS@Mt was significantly improved. The maximum adsorption capacities of Pb²⁺ and methylene blue (MB) reached 884.19 mg·g^-1 and 326.21 mg·g^-1, respectively. The simultaneous adsorption experiments indicated that the occupation of active sites by Pb²⁺ caused the observed decrease of MB adsorption capacity. The theoretical calculations indicated that Pb was preferentially adsorbed by active adsorption units due to strong electron donating ability in comparison to MB. As an active unit, Si-O tetrahedron exhibited stronger adsorption capacity for cationic dyes than Al-O octahedron due to both the large electronegativity and lower adsorption binding energy.

Synthesis and preparation of acid capped CdSe nanocrystals as successful adsorbent and photocatalyst for the removal of dyes from water and its statistical physics analysis

In this study, mercaptosuccinic acid capped CdSe nanocrystals were successfully synthesized and used as photocatalyst for the effective removal of methylene blue (MB) inaqueous solution under visible light and sunlight irradiations including its analysis with statistical physics theory. Dye adsorption properties of these nanocrystals were investigated via experimental kinetics and equilibrium studies. These experimental data were modeled via the application of statistical physics theory to explain the corresponding adsorption mechanism and to characterize the steric and energetic parameters involved in the dye removal. A maximum adsorption capacity of 27.07 mg g^-1 (80% of dye removal) was observed in 10 min using an initial concentration of 30 mg L^-1. Statistical physics calculations indicated that the adsorption energy was lower than 40 kJ mol^-1. It was also established that the dye adsorption was associated to the electrostatic interactions and hydrogen bonding where dye aggregation and multi-molecular adsorption were expected. Overall, the dye removal was a spontaneous, feasible and exothermic. It was concluded that adsorption properties of CdSe-MSA nanocrystals improved the dye photo-catalytic degradation efficiency under visible light thus achieving up to 80% degradation efficiency in 60 min. The synergic effect of adsorption and photo-catalytic degradation performance was mainly due to the surface area (136.43 m² g^-1), small size (3.7 nm), and structural defects (selenium vacancies S_e, interstitial of cadmium I_Cd) of CdSe nanocrystals, which enhanced both the response of these nanomaterials to visible light and their photo-catalytic activity. In summary, these nanocrystals are promising materials to be used in wastewater treatment under sunlight for the removal of organic compounds like dyes.

Efficient Removal of Organic Dye from Aqueous Solution Using Hierarchical Zeolite-Based Biomembrane: Isotherm, Kinetics, Thermodynamics and Recycling Studies

Bio adsorbents have received tremendous attention due to their eco-friendly, cheap and non-toxic nature. Recently, bio-adsorbent-based membranes have been frequently employed for water treatment. The work reports the preparation of a novel adsorbent membrane from hierarchical zeolite, polyvinyl alcohol, carboxymethyl cellulose and agar. The fabricated membrane was characterized spectroscopically and microscopically with several techniques such as XRD, UTM, TGA, optical microscopy and FT-IR, as well as contact-angle studies. The result showed that the hierarchical-zeolite-loaded membrane is superior in terms of thermal stability, mechanical properties and surface roughness. The fabricated membrane was investigated for its efficiency in the removal of Congo red dye in aqueous conditions. The influence of pH, temperature, contact period and the initial concentration of dye and zeolite loading on the adsorption process are also explored. The adsorption results highlighted the maximum sorption property of Congo red on agar/zeolite/carboxymethyl cellulose/polymer biomembrane was found to be higher (15.30 mg/g) than that of zeolite powder (6.4 mg/g). The adsorption isotherms and kinetic parameters were investigated via Langmuir, Freundlich and pseudo-first order, pseudo-second order and the intraparticle diffusion model, respectively. The adsorption isotherms fitted well for both considered isotherms, whereas pseudo-second order fitted well for kinetics. The thermodynamic parameter, ΔG at 303 K, 313 K and 323 K was −9.12, −3.16 and −0.49 KJ/mol, respectively. The work further explores the antibacterial efficacy of the prepared membrane and its reusability.

Quantitative Biosensing Based on a Liquid Crystal Marginally Aligned by the PVA/DMOAP Composite for Optical Signal Amplification

The working principle for a liquid crystal (LC)-based biosensor relies on the disturbance in the orderly aligned LC molecules induced by analytes at the LC-aqueous or LC-solid interface to produce optical signals that can be typically observed under a polarizing optical microscope (POM). Our previous studies demonstrate that such optical response can be enhanced by imposing a weak electric field on LCs so that they are readily tilted from the homeotropic alignment in response to lower concentrations of analytes at the LC-glass interface. In this study, an alternative approach toward signal amplification is proposed by taking advantage of the marginally tilted alignment configuration without applying an electric field. The surface of glass substrates was modified with a binary aligning agent of poly(vinyl alcohol) (PVA) and dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP), in which the amount of PVA was fine-tuned so that the interfacing LC molecules were slightly tilted but remained virtually homeotropically aligned to yield no light leakage under the POM in the absence of an analyte. Two nematic LCs, E7 and 5CB, were each sandwiched between two parallel glass substrates coated with the PVA/DMOAP composite for the detection of bovine serum albumin (BSA), a model protein, and cortisol, a small-molecule steroid hormone. Through image analysis of the optical appearance of E7 observed under the POM, a limit of detection (LOD) of 2.5 × 10−8 μg/mL for BSA and that of 3 × 10−6 μg/mL for cortisol were deduced. Both values are significantly lower than that obtained with only DMOAP as the alignment layers, which correspond to signal amplification of more than six orders of magnitude. The new approach for signal amplification reported in this work enables analytes of a wide range of molecular weights to be detected with high sensitivity.

Physicochemical assessment of anionic dye adsorption on bone char using a multilayer statistical physics model

The statistical physics modeling is a reliable approach to interpret and understand the adsorption mechanism of both organic and inorganic adsorbates. Herein, a theoretical study of the adsorption mechanism of anionic dyes, namely reactive blue 4 (RB4), acid blue 74 (AB74), and acid blue 25 (AB25), on bone char was performed with a multilayer statistical physics model. This model was applied to fit the equilibrium adsorption data of these dyes at 298-313 K and pH 4. Results indicated that the global number of formed dye layers on the bone char varied from 1.62 to 2.24 for RB4, AB74, and AB25 dyes depending on the solution temperature where the saturation adsorption capacities ranged from 0.08 to 0.12 mmol/g. Dye molecular aggregation was also identified for these dyes where dimers and trimers prevailed at different operating conditions especially for adsorbates RB4 and AB74. Adsorption mechanism of these dyes was multimolecular and endothermic with adsorption energies from 10.6 to 20.8 kJ/mol where van der Waals interactions and hydrogen bonding could be present. This investigation contributes to understand the physicochemical variables associated to dye adsorption using low-cost adsorbents as bone char.

Facile Microwave Hydrothermal Synthesis of ZnFe2O4/rGO Nanocomposites and Their Ultra-Fast Adsorption of Methylene Blue Dye

The industry development in the last 200 years has led to to environmental pollution. Dyes emitted by pharmaceutical and other industries are major organic pollutants. Organic dyes are a pollutant that must be removed from the environment. In this work, we adopt a facile microwave hydrothermal method to synthesize ZnFe2O4/rGO (ZFG) adsorbents and investigate the effect of synthesis temperature. The crystal structure, morphology, chemical state, and magnetic property of the nanocomposite are investigated by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and a vibrating sample magnetometer. Furthermore, the synthesized ZFGs are used to remove methylene blue (MB) dye, and the adsorption kinetics, isotherm, mechanism, and reusability of this nanomaterial are studied. The optimal ZFG nanocomposite had a dye removal percentage of almost 100%. The fitting model of adsorption kinetics followed the pseudo-second-order model. The isotherm model followed the Langmuir isotherm and the theoretical maximum adsorption capacity of optimal ZFG calculated by this model was 212.77 mg/g. The π-π stacking and electrostatic interaction resulted in a high adsorption efficiency of ZFG for MB adsorption. In addition, this nanocomposite could be separated by a magnet and maintain its dye removal percentage at almost 100% removal after eight cycles, which indicates its high suitability for utilization in water treatment.

Facile synthesis of chitosan-based acid-resistant composite films for efficient selective adsorption properties towards anionic dyes

To effectively and selectively remove toxic anionic dyes which are heavily discharged and to promote them recovery, a sustainable cellulose nanofiber/chitosan (CNF/CS) composite film was elaborately designed through a facile procedure. Based on the strong supporting effect of CNF and excellent compatibility between CNF and CS, the composite film presents low swelling and acid-proof properties, which can prevent the adsorption process from the disintegration of adsorbent. Moreover, the positive electrical property of CNF/CS film increases the discrepancy in adsorption capacities for anionic and cationic dyes. The maximum adsorption capacity of anionic methyl orange (MO) on CNF/CS film reaches 655.23 mg/g with a desirable recyclability. The adsorption behavior attributed to a physico-chemical and monolayer adsorption process. This work opens a new route for the development of eco-friendly and highly efficient adsorbents on selective removal and recycling of anionic dyes from wastewater.

Synthesis of Magnetic Ferrocene-Containing Polymer with Photothermal Effects for Rapid Degradation of Methylene Blue

Photothermal materials are attracting more and more attention. In this research, we synthesized a ferrocene-containing polymer with magnetism and photothermal properties. The resulting polymer was characterized by Fourier-transform infrared (FT-IR), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Its photo-thermocatalytic activity was investigated by choosing methylene blue (MB) as a model compound. The degradation percent of MB under an irradiated 808 nm laser reaches 99.5% within 15 min, and the degradation rate is 0.5517 min⁻¹, which is 145 times more than that of room temperature degradation. Under irradiation with simulated sunlight, the degradation rate is 0.0092 min⁻¹, which is approximately 2.5 times more than that of room temperature degradation. The present study may open up a feasible route to degrade organic pollutants.

N, S doped carbon quantum dots inside mesoporous silica for effective adsorption of methylene blue dye

This study aimed to develop non-metal elements for doping carbon quantum dots (CQDs) with nitrogen and sulfur (N, S-CQDs), which loaded inside hexagonal mesoporous silica (HMS) in order to effectively remove methylene blue dye (MB) from an aqueous solution. The histidine and cysteine amino acids were used as the source for synthesis N, S-CQDs through the hydrothermal method. Morphology and structure of the N, S-CQDs, and adsorbent (N, S-CQDs/HMS) were characterized by using different microscopic and spectroscopic techniques. The adsorption parameters such as adsorbent dosage (0.25–1 g/L), pH (2–10), contact time (15–75 min), and initial MB dye concentration (20–300 mg/L) were investigated. The maximum adsorption capacity and removal efficiency of MB were determined at 370.4 mg/g and 97%, respectively, under optimum conditions at 303 K. The adsorption isotherm studies were fitted with the Freundlich isotherm equation, and the dye removal kinetics of the adsorbent followed the pseudo-second-order model. Thermodynamic studies showed that the adsorption process had exothermic and spontaneous behavior. The removal of MB next to the Rhodamine B and Reactive Black 5 dyes indicated that the N, S-CQDs/HMS had excellent selective behavior for MB absorption. This prepared adsorbent could be well recycled with suitable activity after four repeated adsorption–desorption cycles. Results revealed that the porous characters, surface area, charge properties, reduction in the bandgap, and quantum yield of the N, S-CQDs/HMS were essential factors that affected dye adsorption.

A state-of-the-art review on wastewater treatment techniques: the effectiveness of adsorption method

The world's water supplies have been contaminated due to large effluents containing toxic pollutants such as dyes, heavy metals, surfactants, personal care products, pesticides, and pharmaceuticals from agricultural, industrial, and municipal resources into water streams. Water contamination and its treatment have emerged out as an escalating challenge globally. Extraordinary efforts have been made to overcome the challenges of wastewater treatment in recent years. Various techniques such as chemical methods like Fenton oxidation and electrochemical oxidation, physical procedures like adsorption and membrane filtration, and several biological techniques have been recognized for the treatment of wastewater. This review communicates insights into recent research developments in different treatment techniques and their applications to eradicate various water contaminants. Research gaps have also been identified regarding multiple strategies for understanding key aspects that are important to pilot-scale or large-scale systems. Based on this review, it can be determined that adsorption is a simple, sustainable, cost-effective, and environmental-friendly technique for wastewater treatment, among all other existing technologies. However, there is a need for further research and development, optimization, and practical implementation of the integrated process for a wide range of applications.

Recent Developments in Polymer Nanocomposite-Based Electrochemical Sensors for Detecting Environmental Pollutants

The human population is generally subjected to diverse pollutants and contaminants in the environment like those in the air, soil, foodstuffs, and drinking water. Therefore, the development of novel purification techniques and efficient detection devices for pollutants is an important challenge. To date, experts in the field have designed distinctive analytical procedures for the detection of pollutants including gas chromatography/mass spectrometry and atomic absorption spectroscopy. While the mentioned procedures enjoy high sensitivity, they suffer from being laborious, expensive, require advanced skills for operation, and are inconvenient to deploy as a result of their massive size. Therefore, in response to the above-mentioned limitations, electrochemical sensors are being developed that enjoy robustness, selectivity, sensitivity, and real-time measurements. Considerable advancements in nanomaterials-based electrochemical sensor platforms have helped to generate new technologies to ensure environmental and human safety. Recently, investigators have expanded considerable effort to utilize polymer nanocomposites for building the electrochemical sensors in view of their promising features such as very good electrocatalytic activities, higher electrical conductivity, and effective surface area in comparison to the traditional polymers. Herein, the first section of this review briefly discusses the most important methods for polymer nanocomposites synthesis, such as in situ polymerization, direct mixing of polymer and nanofillers (melt-mixing and solution-mixing), sol-gel, and electrochemical methods. It then summarizes the current utilization of polymer nanocomposites for the preparation of electrochemical sensors as a novel approach for monitoring and detecting environmental pollutants which include heavy metal ions, pesticides, phenolic compounds, nitroaromatic compounds, nitrite, and hydrazine in different mediums. Finally, the current challenges and future directions for the polymer nanocomposites-based electrochemical sensing of environmental pollutants are outlined.

Enhanced photocatalytic degradation of organic dyes by ultrasonic-assisted electrospray TiO2/graphene oxide on polyacrylonitrile/β-cyclodextrin nanofibrous membranes

Polyacrylonitrile (PAN)/β-cyclodextrin (β-CD) composite nanofibrous membranes immobilized with nano-titanium dioxide (TiO₂) and graphene oxide (GO) were prepared by electrospinning and ultrasonic-assisted electrospinning. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) confirmed that TiO₂ and GO were more evenly dispersed on the surface and inside of the nanofibers after 45 min of ultrasonic treatment. Adding TiO₂ and GO reduced the fiber diameter; the minimum fiber diameter was 84.66 ± 40.58 nm when the mass ratio of TiO₂-to-GO was 8:2 (PAN/β-CD nanofibrous membranes was 191.10 ± 45.66 nm). Using the anionic dye methyl orange (MO) and the cationic dye methylene blue (MB) as pollutant models, the photocatalytic activity of the nanofibrous membrane under natural sunlight was evaluated. It was found that PAN/β-CD/TiO₂/GO composite nanofibrous membrane with an 8:2 mass ratio of TiO₂-to-GO exhibited the best degradation efficiency for the dyes. The degradation efficiency for MB and MO were 93.52 ± 1.83% and 90.92 ± 1.52%, respectively. Meanwhile, the PAN/β-CD/TiO₂/GO composite nanofibrous membrane also displayed good antibacterial properties and the degradation efficiency for MB and MO remained above 80% after 3 cycles. In general, the PAN/β-CD/TiO₂/GO nanofibrous membrane is eco-friendly, reusable, and has great potential for the removal of dyes from industrial wastewaters.

Adsorption of methylene blue dye from aqueous solution by a novel PVA/CMC/halloysite nanoclay bio composite: Characterization, kinetics, isotherm and antibacterial properties

Here the fabrication of a novel PVA/CMC/halloysite nanoclay membrane for the effective adsorption of cationic dye (methylene blue, MB) from aqueous environment is reported. The membranes were analyzed through scanning electron microscopy (SEM), optical microscopy (OM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), contact angle and universal testing machine (UTM) analysis. The adsorption behavior of the membrane in terms of nanoclay loading, contact time, initial concentration of MB, pH and temperature were also discussed. The membrane exhibits excellent removal efficiency (99.5%) for MB in the optimal conditions such as nanoclay dose = 6 wt%, initial dye concentration = 10 ppm, contact time = 240 min, pH = 10 and temperature = 30 °C. Three isotherm models (Freundlich, Langmuir and Temkin) were employed to analyze the dye adsorption data. The results revealed that the adsorption process could be described well with both Freundlich and Langmuir isotherm model. The kinetics of MB adsorption onto membrane follows pseudo-second-order model while thermodynamic parameter indicate that adsorption is feasible and endothermic in nature. The antibacterial studies revealed that the PVA/CMC/halloysite nanoclay membrane possess notable antibacterial property. Finally, the desorption studies showed that the membrane have good reusability even after four recycles.

Present applications of titanium dioxide for the photocatalytic removal of pollutants from water: A review

The evolution of modern technology and industrial processes has been accompanied by an increase in the utilization of chemicals to derive new products. Water bodies are frequently contaminated by the presence of conventional pollutants such as dyes and heavy metals, as well as microorganisms that are responsible for various diseases. A sharp rise has also been observed in the presence of new compounds heretofore excluded from the design and evaluation of wastewater treatment processes, categorized as "emerging pollutants". While some are harmless, certain emerging pollutants possess the ability to cause debilitating effects on a wide spectrum of living organisms. Photocatalytic degradation has emerged as an increasingly popular solution to the problem of water pollution due to its effectiveness and versatility. The primary objective of this study is to thoroughly scrutinize recent applications of titanium dioxide and its modified forms as photocatalytic materials in the removal and control of several classes of water pollutants as reported in literature. Different structural modifications are used to enhance the performance of the photocatalyst such as doping and formation of composites. The principles of these modifications have been scrutinized and evaluated in this review in order to present their advantages and drawbacks. The mechanisms involved in the removal of different pollutants through photocatalysis performed by TiO2 have been highlighted. The factors affecting the mechanism of photocatalysis and those affecting the performance of different TiO2-based photocatalysts have also been thoroughly discussed, thereby presenting a comprehensive view of all aspects involved in the application of TiO₂ to remediate and control water pollution.

Fabrication and physical properties of a novel macroporous poly(vinyl alcohol)/cellulose fibre product

The objective of this work was to prepare functionalized cellulose fiber from sugar cane leaf (SCF) used to produce novel biomaterial. The SCF was treated with chloroacetic acid and sodium hydroxide (NaOH) to produce a modified cellulose fibre (MSCF). At higher MSCF loading, a greater porous density was observed under SEM. The addition of MSCF improved, the water resistance of the cured PVA/MSCF in both acid and base media through chemical reactions. The moisture absorption and moisture content of the cured PVA/MSCF film increased as the loading increased MSCF. Tg of the cured PVA/MSCF showed a clear decrease that was attributed to the greater molecular weight and softness of the molecular chains. The cured PVA/MSCF showed good MB absorption from wastewater. The improvement in biodegradability of the cured PVA/MSCF film may make it a candidate material for use in environmentally-sensitive applications.