TiO2 Suspensions Research Articles

Green synthesized nano-TiO2 from Tamarindusindica leaf extract for photo-degradation of combination of dyes by suspension and immobilization on inert supports

ABSTRACT The present study aims to use green synthesized TiO2 as a photocatalyst in suspended and immobilized form under UV light to efficiently degrade a combination of reactive dyes, namely titan yellow, methyl orange, rhodamine B, and methylene blue. TiO2 nanoparticles (NPs) were synthesized using Tamarindus indica leaf extract and were utilized to parametrically study photo-degradation at room temperature. The green synthesized NPs were characterized by Powder XRD, SEM, and FTIR techniques to understand the crystalline phase/purity, morphology, and functional groups respectively. The TiO2 in suspension under UV light showed >90% degradation towards a 10 ppm composite dye at a loading of 1.5 gL−1, pH 7, and an irradiation time of 120 min. Subsequently, TiO2 was further immobilized in-situ, on inert supports of perlite granules and glass and studied for catalytic activity in batch and continuous modes. The TiO2 nanoparticles immobilized on perlite granules and glass showed 59 and 48% degradation in batch operation under the same conditions as in suspended form. In continuous mode, the highest degradation activity was recorded at 2 Lh−1 after 4 passes. Further, kinetic studies reveal that the degradation reaction is best described by Langmuir Hinshelwood kinetics for both suspended and immobilized TiO2.

Acidic phosphonium-based ionic liquid encapsulated on titania particles with enhanced electrorheological response

Research on electrorheological (ER) fluids has led to significant advancements in the development of smart materials that adjust their viscosity in response to applied electric fields. This study focused on synthesizing titania ionogel-based particles (TiO2-IL) using an environmentally friendly sol-gel process involving tetrabutoxy-titanium (TBT) combined with an ionic liquid (IL), specifically 11-carboxyundecyl-triphenyl-phosphonium bromide. The successful incorporation of the IL into the TiO2 particles was confirmed through thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and zeta potential analysis. The electrorheologial properties of TiO2-IL ionogel suspension in silicone oil were compared with those of pure TiO2 suspension. The addition of the ionic liquid (IL) significantly enhanced the electrorheological (ER) properties of the fluid, achieving a shear stress of approximately 1340Pa at an electric field strength of 5kV/mm. The fluid also exhibited excellent reversibility and a rapid response to changes in the electric field, which is attributed to the higher polarizability by the IL. Furthermore, the study observed low current density during operation, which helps maintain the fluid’s integrity and longevity under high electric fields. The fluids demonstrated stable ER effect across a temperature range of 40 to 70 ℃ and a reasonable sedimentation stability of around 80%. These characteristics, combined with the moderate conditions for particle preparation, make the TiO2-IL fluid a promising candidate for ER applications.

Slow‐release fertilizer behavior of polyvinyl alcohol (PVA)/urea/TiO2 nanofiber membrane

AbstractNanofiber is a material used as a drug carrier matrix in drug release materials. Its morphology has high porosity and good flexibility, making it suitable for this purpose. The use of nanofiber as a carrier matrix in slow‐release fertilizer (SRF) material is expected to provide a solution for releasing fertilizer into the soil more measurably and efficiently In this study, PVA/Urea/TiO2 nanofibers were fabricated using the electrospinning method. PVA/Urea/TiO2 SRFs were prepared using varying urea mass percentages (10%, 15%, and 20% of PVA mass) and the concentration of titanium dioxide suspension solution (0, 0.2, and 0.4 mL). Every sample was analyzed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) and tested using contact angle and slow‐release tests. From SEM characterizations, all samples showed the ability to form nanofiber. It was found that the membrane diameter sizes for each sample A, B, C, D, E, and F were 341 ± 5, 309 ± 12, 109 ± 3, 313 ± 10, 109 ± 3, and 158 ± 6 nm, respectively. The FTIR characterizations showed that all the matrix samples successfully contained the nitrogen group, which was found at wave number 1605 cm−1 (NH deformation), 1574 cm−1 (CN stretching), and 3430 cm−1 (NH stretching). The SEM mapping images confirmed the presence of titanium dioxide (green dots). The contact angle test showed that all samples had hydrophilic properties (the contact angle value lower than 90°), and the greatest value of contact angle measurement was 31.08° for sample C/E (sample with the most presence of TiO2 suspension solution 0.4 mL). The sample with the greatest TiO2 suspension concentration (0.4 mL) had the longest urea release time, lasting 8 days. This result indicates the addition of TiO2, can potentially suppress the hydrophilic properties of the PVA membrane. It is found that the addition of TiO2 influenced the membrane's hydrophilicity, consequently increasing the release rate. This study used the Korsmeyer–Peppas mathematical kinetic model to show that diffusion and swelling are release mechanisms for SRF membranes.

A robust self-regenerating graphene-based adsorbent for pharmaceutical removal in various water environments

The presence of active pharmaceutical ingredients (APIs) in wastewater effluents and natural aquatic systems threatens ecological and human health. While activated carbon-based adsorbents, such as GAC and PAC, are widely used for API removal, they exhibit certain deficiencies, including reduced performance due to the presence of natural organic macromolecules (NOMs) and high regeneration costs. There is growing demand for a robust, stable, and self-regenerative adsorbent designed for API removal in various environments. In this study, we synthesized a self-generating metal oxide nano-composite (S-MGC) containing titanium dioxide (TiO2) and silicon dioxide (SiO2) combined with 3D graphene oxide (GO) to adsorb APIs and undergo regeneration via light illumination. We determined optimal TiO2:SiO2:GO compositions for the S-MGCs through experiments using a model contaminant, methylene blue. The physical and chemical properties of S-MGCs were characterized, and their adsorption and photodegradation capabilities were studied using five model APIs, including sulfamethoxazole, carbamazepine, ketoprofen, valsartan, and diclofenac, both in single-component and multi-component mixtures. In the absence of TiO2/SiO2, 3D graphene oxide (CGB) displayed better adsorption performance compared to GAC, and S-MGCs further improve CGB's adsorption capacity. This performance remained consistent in two complex water environments: aqueous solutions at varying NOM levels and artificial urine. TiO2 supported on the GO surface exhibits similar photocatalytic activity to suspended TiO2. In a continuous fixed-bed column test, S-MGCs demonstrated robust API adsorption performance that is maintained in the presence of NOM or urine, and can be regenerated through multiple cycles of adsorption and light illumination.

Life Cycle Assessment of Immobilised and Slurry Photocatalytic Systems for Removal of Natural Organic Matter in Water

This study investigates the environmental impacts caused by the scaling up of the photocatalytic purification of drinking water using ultraviolet light-emitting diode technology. The life cycle assessment methodology was utilised to estimate the environmental impacts of two different reactor setups commonly used in lab-scale studies: an immobilised and a suspended TiO2 catalytic system. The functional unit adopted was the treatment of 1 L of water with an initial 7.8 mg/L concentration of natural organic matter, achieving a final 1 mg/L concentration. The use of a suspended photocatalyst was found to have an environmental footprint that was 87% lower than that of the immobilised one. From the sensitivity analysis, the environmental hotspots of the treatment process were the electricity usage and immobilised catalyst production. Therefore, alternative scenarios investigating the use of a renewable electricity mix and recyclable materials were explored to enhance the environmental performance of the photocatalytic treatment process. Using a renewable electricity mix, a decrease of 55% and 15% for the suspended and immobilised catalyst, respectively, was observed. Additionally, the process of recycling the glass used to support the immobilised catalyst achieved a maximum reduction of 22% in the environmental impact from the original scenario, with 100 glass reuses appearing to provide diminishing returns on the environmental impact savings.

Ensuring Photocatalyst Properties on Cellulosic Fabric by Using Citric Acid Modified with TiO2 Degussa P25 Nanoparticles

Citric acid, which is a type of polycarboxylic acid, is environmentally friendly, and non-harmful and it can be used as a cross-linker. Titanium dioxide (TiO2) nanoparticle is a catalyst that provides many properties for textile products with its large surface area. Present study, a mixture was prepared with different concentrations of citric acid and commercial TiO2 Degussa P25 nanopowder suspensions. Two different curing temperatures (120°C and 140°C) were applied to the cotton fabrics in the pad-dry-cure method. The adhesion of the chemicals to the fiber surface was confirmed by scanning electron microscopy (SEM) and Fourier transform infrared spectrophotometer (FT/IR) analysis. The yellowing effect caused by citric acid on cotton fabrics was eliminated with white TiO2 nanoparticles. Methylene blue was used for staining the samples. Color analyses were performed with a spectrophotometer to determine photocatalytic properties of the samples. It was determined that the samples treated with a mixture of 30 g/L citric acid and TiO2 suspensions were the most discolored samples after exposure to solar light. The photocatalyst properties of the samples were further improved by removing the aggregation of TiO2 NPs on the fiber surface with the washing procedure.

Nitrate radical formation and reaction with limonene by TiO2 photocatalysis: A kinetic study

The oxidative cleavage and the epoxidation of the endocyclic double bond of limonene can be performed in irradiated suspensions of TiO2 because of the formation of nitrate radical species deriving from the hole-induced oxidation of nitrate ions. The reaction is boosted by electron acceptors such as silver ions or in the presence of silver nanoparticles at the surface of TiO2. A thorough kinetic analysis of the reaction performances under several experimental conditions provided a set of kinetic constants, which characterise the elementary steps of this complex reaction. In particular, for the first time an evaluation of the kinetics of the formation of nitrate radicals in heterogeneous photocatalysis has been provided. Moreover, the effect of silver ions in solution and of silver nanoparticles at the surface of TiO2 could be quantitatively estimated. The developed set of kinetic equations satisfactorily predict the experimental data under several experimental conditions and can be used as the starting point of reactor design activities, in view of a future scale-up of the process. Moreover, the successful fitting of the model corroborates the proposed reaction mechanism, and provides fundamental insights on the elementary reaction steps.

High-concentration TiO2 suspension (>70 wt%) with low viscosity suitable for waterborne coatings

High-concentration TiO2 suspension is favored by industry since it would effectively simplify the processing of coatings, benefiting energy and cost savings. However, achieving a dense TiO2 suspension with low viscosity and good dispersion remains a challenge due to the large particle size and high density of pigment-grade TiO2 particles (200–400 nm). In this work, we proposed high-concentration TiO2 suspensions with low viscosity and excellent storage stability by grafting copolymer nanospheres to TiO2. The TiO2 particles are isolated through the steric hindrance and electrostatic repulsion of PMS (P(MMA-MPS)) nanospheres which are synthesized by emulsion polymerization of methyl methacrylate (MMA) and γ-methacryloxypropyltrimethoxysilane (MPS). The TiO2 suspension modified by PMS of 90 nm exhibits the highest concentration in water (74 wt%) while maintaining the lowest viscosity (95 mPa·s at the shear rate of 200 r/s). Through thermal storage at 50 °C in 28 d, the concentrated TiO2-PMS suspensions demonstrated excellent stability without any noticeable decline in coating properties compared to pure TiO2. The coating film of TiO2-PMS-90 suspension exhibited the optimal contrast ratio (92.4 %) and gloss value (78.5 GU) after thermal storage. The 50 L macro production results of TiO2-PMS-90 coincided with the lab results which will favor larger scale-up production. This work presents a strategy to enhance the dispersion stability of TiO2 particles to obtain a high-concentration slurry with low viscosity and superior flowability, particularly suitable for waterborne coatings.

Study of the photocatalytic activity of clay supported TiO2 nanoparticles for methylene blue degradation.

The photocatalytic degradation of a methylene blue (MB) solution was studied using a formulation of TiO2 nanoparticles (NPs) suspended in a commercial antibacterial paint, and supported on clay strips. All experiments were carried out in a batch reactor containing a UV-C light source and the MB solution under stirring. Parameters such as catalyst mass loading, MB concentration, as well as catalyst properties were considered for the experimental procedure. The effect of the mass loading on the photocatalytic activity of the TiO2 formulations immobilized on the clay supports was evaluated using 100, 200, and 500 mg of TiO2 on 40 mL of paint, sampling the MB solution under degradation at 0, 2, 5, 10, 20, 50, 100 and 200 min. The aliquots were analyzed by optical spectroscopy in the 400-1000 range to determine the absorbance, calculate the concentration with the Beer-Lambert equation, and obtain the amount of MB degradation. The maximum photocatalytic degradation of MB for the supported photocatalyst was 52%, 55%, and 60%, respectively. For comparison, suspended TiO2 nanoparticles lead to ca. 95% of MB photodegradation in ca. 60 min. The supported photocatalysts were tested in three consecutive cycles of 200 min to study the mechanical and photocatalytic stability. The activity of the photocatalysts with mass loading of 100 and 200 mg TiO2 decreased to ca. 35% after the three cycles, while the formulation with 500 mg TiO2 remained stable for three cycles. The final samples of each cycle were characterized by XRF, discarding erosion of the material from the support.

Overlooked role of aqueous chromate (VI) as a photosensitizer in enhancing the photochemical reactivity of ferrihydrite and production of hydroxyl radical

The reactive oxygen species (ROS) photochemically generated from natural iron minerals have gained significant attention. Amidst the previous studies on the impact of heavy metal ions on ROS generation, our study addresses the role of the anion Cr(VI), with its intrinsic photoactivity, in influencing ROS photochemical generation with the co-presence of minerals. We investigated the transformation of inorganic/organic pollutants (Cr(VI) and benzoic acid) at the ferrihydrite interface, considering sunlight-mediated conversion processes (300–1000 nm). Increased photochemical reactivity of ferrihydrite was observed in the presence of aqueous Cr(VI), acting as a photosensitizer. Meanwhile, a positive correlation between hydroxyl radical (•OH) production and concentrations of aqueous Cr(VI) was observed, with a 650% increase of •OH generation at 50 mg L−1 Cr(VI) compared to systems without Cr(VI). Our photochemical batch experiments elucidated three potential pathways for •OH photochemical production under varying wet chemistry conditions: (1) ferrihydrite hole-mediated pathway, (2) chromium intermediate O-I-mediated pathway, and (3) chromium intermediates CrIV/V-mediated pathway. Notably, even in the visible region (> 425 nm), the promotion of aqueous Cr(VI) on •OH accumulation was observed in the presence of ferrihydrite and TiO2 suspensions, attributed to Cr(VI) photosensitization at the mineral interface. This study sheds light on the overlooked role of aqueous Cr(VI) in the photochemical reactivity of minerals, thereby enhancing our understanding of pollutant fate in acid mining-impacted environments.

Experimental study on the film droplet production from a bubble burst on the free surface

The aerosol released during a severe reactor accident may be retained in the liquid pool. During the venting stage of the suppression pool, bubbles generated in the pool will rise to the free surface and burst to generate droplets. The airflow re-entrains aerosols from the liquid to the air via droplets. Accurate evaluation of droplet entrainment needs to acquire the diameter and number of droplets generated by a bubble, so studying the various behaviors that affect the above parameters is necessary. In this paper, high-speed photography is used to visualize the phenomenon of a single bubble burst to generate film droplets in deionized water and TiO2 suspensions at different phase temperatures. Image processing is used to obtain the bubble film opening rate, the bubble burst position, the bubble lifetime, and the diameter and number of film droplets. The results show that the film thickness decays with time in a power law with a parameter of 2/3, and the newly defined film thickness also decays with time in a power law after considering the bubble radius and physical parameters. This rule is applicable in different liquid temperatures and solutes. Besides, the film thickness increases with liquid temperature and aerosol concentration; the bubble lifetime obeys the Weibull distribution, with the average bubble lifetime of deionized water varies non-monotonically with the liquid temperature, the average lifetime increase with aerosol concentration and liquid temperature in aerosol suspension; The average droplet diameter decreases with bubble lifetime in a power law with a parameter of 5/16, the droplet diameter distribution can be calculated by the gamma distribution of the normalized droplet diameter and the bubble lifetime, and in good agreement with the experimental data, the droplet entrainment factor can also be calculated from the critical droplet diameter and bubble lifetime, which decreases with bubble lifetime.

Size characterization and quantification of E171 titanium dioxide particles in food sauces using spICP-MS

A sample preparation method associated to a single particle inductively coupled plasma mass spectrometry (spICP-MS) analysis was developed to ensure a quantitative characterization of TiO2 particles in food sauces. The method was optimized with a fat sauce matrix for which the pristine E171 additive was available. The highest extracted amount of TiO2 particles was obtained using an ultrasound-assisted dispersion in tetramethylammonium hydroxide (TMAH). TEM analysis confirmed these results, showing that these conditions effectively solubilised the fat matrix. The trueness of the method evaluated using a Ti-free mayonnaise spiked with the E171 additive or the NM-100 reference material (NM-100 RM) proved satisfactory with quantitative mass recoveries (>90%). A good agreement in terms of particle sizes was also obtained between those of the spiked mayonnaise and the TiO2 suspensions used for spiking. However, as also shown in the optimization study, the presence of fatty compounds tended to improve particle dispersion. The application of this procedure to E171 labelled food sauces purchased from the EU market showed concentrations of TiO2 particles in the (0.6 – 6) g/kg range with median diameters between 170 and 320 nm. The TiO2 nanoparticle fraction (size < 100 nm) was evaluated between 2% and 12%, depending on the sample. No titanium was detected in the food sauces not labelled E171. Conclusively, the developed method can provide an efficient and reliable analytical approach for TiO2 particles determination in fat food samples which complies with the EU current regulations.

Entropy generation in water conveying nanoparticles flow over a vertically moving rotating surface: Keller box analysis

PurposeThe purpose of this study is to investigate the entropy generation in different nanofluids flow over a vertically moving rotating disk. Unlike the classical Karman flow, water-based nanofluids have various suspended nanoparticles, namely, Cu, Ag, Al2O3 and TiO2, and the disk is also moving vertically with time-dependent velocity.Design/methodology/approachThe Keller box technique numerically solves the governing equations after reduction by suitable similarity transformations. The shear stress and heat transport features, along with flow and temperature fields, are numerically computed for different concentrations of the nanoparticles.FindingsThis study is done comparatively in between different nanofluids and for the cases of vertical movement of the disk. It is found that heat transfer characteristics rely not only on considered nanofluid but also on disk movement. Moreover, the upward movement of the disk diminishes the heat-transfer characteristics of the fluid for considered nanoparticles. In addition, for the same group of nanoparticles, an entropy generation study is also performed, and an increasing trend is found for all nanoparticles, with alumina nanoparticles dominating the others.Originality/valueThis research is a novel work on a vertically moving rotating surface for the water-conveying nanoparticle fluid flow with entropy generation analysis. The results were found to be in good agreement in the case of pure fluid.

Nitrate radicals generated by TiO2 heterogeneous photocatalysis: Application to the cleavage of C=C double bond to carbonyl compounds

The oxidative cleavage of alkenes represents a relevant chemical process with immense potential for the synthesis of partially oxidized compounds. Several methodologies have been proposed for achieving oxidative cleavage of alkenes, aiming to obtain carbonyl products. However, none of these approaches have been successfully scaled up for industrial applications beyond the laboratory scale. In this study, we report the selective photocatalytic oxidative cleavage of limonene to limononaldehyde using irradiated TiO2 suspensions in the presence of silver nitrate under ambient conditions. Results demonstrate that within one hour of irradiation, a notable conversion and selectivity of 60% towards limononaldehyde can be achieved. The investigation reveals that the oxidation process is primarily driven by nitrate radicals, generated through hole-induced oxidation of nitrate ions. Notably, this selective photocatalytic approach shows potentials that bode well for its application to other olefinic substrates in addition to limonene. These results present a promising pathway for the scalable industrial synthesis of partially oxidized compounds through selective photocatalytic oxidation of alkenes.

EVALUATION OF OCCUPATIONAL EXPOSURE TO TIO2 NANOPARTICLES: MICROWAVE-ASSISTED ACID DIGESTION METHOD ON AIR MEMBRANE FILTERS

Titanium dioxide (TiO2) nanoparticles have been extensively used in various industrial sectors and applications, including cosmetics, catalysts, food additives, inks, paints, and coatings. However, the International Agency for Research on Cancer (IARC) has classified TiO2 nanoparticles as a potential carcinogen for humans, meaning they may cause cancer and pose serious health complications, particularly for manufacturing workers. This highlights the need for better evaluation to determine worker exposure. In this study, suspended TiO2 nanoparticles were sampled using a nanoparticle respiratory deposition (NRD) sampler fitted with specially designed membrane filters and analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The digestion method used for titanium element recovery after nanoparticle sampling is crucial for optimal ICP-MS analysis. Therefore, this study aimed to investigate the most suitable digestion method. A microwave-acid digestion method using concentrated nitric acid and concentrated hydrochloric acid at a 7:4 ratio, with a run time of 30 minutes and the temperature set to 200°C showed remarkable titanium recovery compared to other methods. These findings may pave the way for optimal analysis of suspended TiO2 nanoparticles in assessing occupational exposure while promoting sustainability and eco-friendliness in resource utilization.

Experimental Photodegradation of OPs and CBs by Advanced Oxidation Techniques in the Aqueous TiO2 Suspensions

The reaction of pesticides with the OH radical, is the most dominant annihilation reaction ofthe atmosphere. Phosmet, Azamethiphos, Coumaphos and Temephos were used as organophosphorouspesticides, and Methiocarb, Carbofuran and Pirimicarb compounds were used as carbamate pesticideswith the aim of investigating the kinetics of the reactions of Organophosphorous (OPs) and Carbamate(CBs) Pesticides with the OH radicals. In aqueous TiO2 suspensions, the degradation reactions viaphotocatalytic-effect of the seven pesticides selected as pollutants were analysed, and the impact of theinitial concentration was calculated. All experiments were conducted in the same photoreactor and underthe same conditions as three repetitions. The optimum amount of photocatalyst for the studied pesticidewas determined and TiO2 concentration for all experiments were taken as 0.2 g/100 mL. Considering thatorganic pollutants are present in water in trace amount, the initial concentrations for all organiccompounds were added so as to be1.0x10-4 molxL-1, into the suspensions and the solution containing theorganic pollutant. In this study, degradation speed of pesticides were determined experimentally, and thefastest degrading pesticide was tried to be found out.

Disinfection of Digestate Effluents Using Photocatalytic Nanofiltration

The disinfection properties of photocatalysis on liquid digestate derived from biogas plants have been investigated for the first time. The study presents the physiological characteristics of liquid digestate retrieved from various biogas plants based in northern Greece, revealing the heterogeneity of this matrix. Preliminary photocatalysis experiments conducted on inoculated liquid digestate samples showed that disinfection was possible when a pre-treated digestate underwent a combination of centrifuge–flocculation–μfiltration after 5.5 h with 0.7 g/L suspended TiO2 under UVA illumination. To explore the feasibility of an industrial application based on this concept, a novel design photocatalytic nanofiltration reactor was implemented for disinfection experiments on pre-treated liquid digestate. The synergistic action of photocatalysis during nanofiltration alleviated the leakage phenomena, and both the retentate and permeate effluents had lower concentrations of pathogens by approximately 1–2 log10 cfu/mL. This work sets out the basis for the efficient operation and engineering application of collaborative technology, with photocatalysis as the final step for liquid digestate sanitation and reusable water recovery.

Tuning TiO2 suspension stability with poly(α-alkyl carboxylic acids) via side chain length and chain stereochemistry

Effects of hydrophobicity and stereochemistry of poly(α-alkyl carboxylic acids) on the properties of TiO2 suspensions were studied with experimental and in silico methods. Zeta potential measurements show that the addition of the more hydrophilic poly(acrylic acid) (PAA) to TiO2 suspensions shifts the isoelectric point of the nanoparticles towards lower pH the most, followed by poly(methacrylic acid) (PMA) and poly(ethacrylic) acid (PEA). Stereochemistry has a less pronounced effect on suspension stability, except at low pH, where isotactic PMA (iPMA) is not soluble in water. Dynamic light scattering measurements show that the aggregate size of the nanoparticles correlates well with their zeta potential and the aggregates are largest at the isoelectric point of the nanoparticles. Molecular dynamics (MD) and Monte Carlo (MC) computer simulations were used to study the interaction of polyacids with the surface of nanoparticles. MD simulations show that PAA forms the largest amount of hydrogen bonds with TiO2, followed by PMA. PEA forms very low numbers of hydrogen bonds with the nanoparticle surface. MC simulations were used to study the effect of pKa of COOH groups of polyacids on their adsorption on TiO2. It was found that even small differences in pKa between the polyacids have a strong effect.

Titanium Dioxide (TiO2) Modified Bentonite for Photodegradation in Methylene Blue Dye

Dye is one of the waste waters, which will be a problem if the content is excessive in the water. Modifying bentonite with titanium dioxide (TiO2) as a photocatalyst for removal of dye waste. In this study, composite synthesis was carried out by mixing bentonite and TiO2 suspensions. The mass of bentonite is 20 g, and the mass variations of TiO2 are 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%. The resulting composite was heated using a furnace at 550°C for 5 hours. Bentonite-TiO2 composites were characterized using Fourier Transform Infrared, X-Ray Diffraction, and Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX). Photodegradation of methylene blue dye with bentonite-TiO2 was carried out by varying the mass of bentonite-TiO2 photocatalysts (0.02, 0.04, 0.06, 0.08 g); variations in pH (1, 3, 5, 7, and 9), and variations in UV irradiation time (30, 60, 90, and 120 minutes). The results of characterization with FTIR showed the presence of Ti-O-Ti vibrations at wavenumber 1419 cm-1 and Si-O-Ti at wave numbers 780 cm-1 and 799 cm-1. Characterization of 20% bentonite-TiO2 by XRD showed rutile, anatase, and montmorillonite phases. The SEM-EDX bentonite-TiO2 characterization results produced some small particles with a layered structure with TiO2 particles clumping and still in the form of agglomerates, and the EDX results showed the chemical composition of Si and Ti. The results of photodegradation showed that the best activity for the bentonite-TiO2 composite occurred in photocatalyst BT-20% with a mass of 0.08 g, pH 1, and UV irradiation time of 120 minutes with methylene blue 99.942% degraded.

Prediction of the optical properties of TiO2 suspension by coupling the classical particle agglomeration model with the discrete dipole approximation algorithm and experimental verification

Nanofluids are widely used in the field of energy and environment. However, the optical properties of such multiphase suspension are quite complex. Even for the well-studied TiO2 suspension, theoretical investigation of its optical parameters is quite rare, which remarkably restricts the extension of their application especially in the field of solar energy and optofluidics. Therefore, in this paper, the optical properties of TiO2 suspension were studied by coupling the classical particle agglomeration model and the discrete dipole approximation algorithm. The absorption and scattering coefficients of TiO2 aqueous suspension have been calculated and verified by experimental results. The effects of cluster compactness, size and other factors on the phase function were analyzed. Our work can also provide a reference for the study of optical properties of other nanofluids.