Adsorption and photocatalytic performance of bentonite-titanium dioxide composites for methylene blue and rhodamine B decoloration

Synthesis of gum acacia-cl-acrylic acid-co-itaconic acid hydrogels for efficient removal of toxic dye rhodamine-B: A step for sustainable environment

In the present study, we prepared Gum Acacia-cl-Acrylic acid-co-itaconic acid (GA-cl-AA-co-IA) hydrogels by free radical crosslink polymerization method for the efficient removal of Rhodamine-B (RhB) dye. The hydrogels were further characterized by different characterization techniques: Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Atomic force microscopy (AFM), Brunuer-Emmett-Teller (BET) and field emission scanning electron microscopy (FE-SEM) to confirm synthesis. The synthesis parameters were optimized by swelling studies, which were performed by gravimetric analysis method. The maximum swelling ability of hydrogels synthesized at optimized concentrations was 2170 % in basic medium. GA-cl-AA-co-IA hydrogels showed a good adsorption ability for RhB dye. The impact of various adsorption parameters (adsorbent dose, initial adsorbate (dye) concentration, pH of medium, and temperature) on adsorption ability was also evaluated. Langmuir, Freundlich and temkin adsorption isotherm model and pseudo first, second order model and intra-particle diffusion kinetic models were used to study the nature of adsorption process and kinetics. The adsorption by the hydrogels were best explained by Langmuir isotherm and Pseudo second order kinetic model. The reusability studies of GA-cl-AA-co-IA hydrogel showed that hydrogels showed good adsorption abilities even after 6 consecutive adsorption desorption cycles.

Low-cost novel nano-constructed granite composites for removal of hazardous Terasil dye from wastewater

The hazardous dyes on mixing with water resources are affecting many life forms. Granite stone is popular worldwide for decorating floors, making other forms of decorative materials and items. Granite stone powder waste can be obtained free of cost from marble factories as factories spend on the disposal of this waste. In the present study, novel granite stone powder waste composite has been prepared and utilized for the effective removal of Terasil dye. Two types of granite including gray granite and white granite were used in pure, calcinized, and chemically modified forms. Freundlich adsorption isotherm model best explained the adsorption mechanism of dye removal using granite composites as compared to other adsorption isothermal models. Characterization techniques like scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used for the determination of morphological features and functional groups of granite composites. The obtained results were statistically analyzed using analysis of variance (ANOVA) along with the post hoc Tukey test. An extraordinarily high Terasil dye uptake capacity (more than 400 mg/g) was exhibited by granite composites prepared using sodium metasilicate. The synthesized novel nano-constructed composites provided a viable strategy as compared to the pure granite stone for dye removal from wastewater water.

Novel TiO2/GO/M-MMT nano-heterostructured composites exhibiting high photocatalytic activity

This study proposed a technique to enhance the photocatalytic properties of TiO2 using graphene oxide (GO) and modified Montmorillonite (M-MMT). TiO2/GO/M-MMT nano-heterostructured composites were prepared via hydrothermal and co-precipitation. The photocatalytic performance was evaluated by investigating the photodegradation rate and absorption behavior of methyl orange (MO) under visible light irradiation. The results showed that TiO2/GO/M-MMT heterojunction exhibited excellent photocatalytic degradation performance, as the degradation rate of MO was observed to be 99.3% within 150 min. The density of adsorbed MO decreased by 62.1% after 210 min of dark adsorption using the TiO2/GO/M-MMT composite, which was significantly higher than that achieved using M-MMT, GO/M-MMT, and TiO2/M-MMT. The nano-heterostructure increased the effective interface between TiO2, GO, and MMT, which increased the charge transfer ability and prolonged the electron-hole separation time. Therefore, the results of this study can be used to design novel photocatalysts to eradicate environmental pollutants.

Recent Review of Titania-Clay-Based Composites Emerging as Advanced Adsorbents and Photocatalysts for Degradation of Dyes over the Last Decade

Textile industry being one of the most flourishing industries keeps growing and developing every year, and the consequences are not very pleasant. Even though its contribution towards economy of a country is indisputable, there are many pros and cons associated with it that should not be brushed aside, one of them being textile dye waste which is also growing at alarming rate. Many techniques have been designed to deal with this environmental crisis including adsorption and photodegradation of dye waste by various substances, both natural and synthetic. TiO2 and clay both have gained immense popularity in this area. Over the last decade, many successful attempts have been made to design TiO2-clay-based composites to combine and make the most of their individual capabilities to degrade textile dye waste. While clay is an effective adsorbent, inexpensive, innocuous, and a great ion exchanger, TiO2 provides supplementary active sites and free radicals and speeds up the degradation rate of dyes. This review summarizes various features of TiO2-clay-based composites including their surface characteristics, their role as dye adsorbents and photocatalysts, challenges in their implementation, and modifications to overcome these challenges made over the last decade.

Pumice-supported ZnO-photocatalyzed degradation of organic pollutant in textile effluent: optimization by response surface methodology, artificial neural network, and adaptive neural-fuzzy inference system

A heterogeneous photocatalysis was adopted to treat textile industry effluent using a combination of pumice-supported ZnO (PUM-ZnO) photocatalyst and solar irradiation. The visible light-responsive PUM-ZnO photocatalyst was prepared via the impregnation method and characterized using various spectroscopic techniques. The photocatalytic degradation process was modeled via response surface methodology (RSM), artificial neural network (ANN), and adaptive neuro-fuzzy inference system (ANFIS), while the optimization of the three independent parameters significant to the photocatalytic process was carried out by a genetic algorithm (GA) and RSM methods. The low standard error of prediction (SEP) of 0.56-1.75% and high coefficient of determination (R²) greater than 0.96 for the models developed indicated that they adequately predicted the photodegradation process with high accuracy in the order of ANFIS > ANN > RSM. The process optimization results from the developed models showed that GA performed better than RSM. The best optimal condition (3.29 g/L catalyst dosage, 45.85 min irradiation time, and 3.13 effluent pH) that resulted in maximum degradation efficiency of 99.46% was achieved by the ANFIS model coupled with GA (ANFIS-GA).

Bentonite-titanium dioxide functional nanocomposite suitable for wastewater treatment; An integrated photocatalyst-adsorbent system

An integrated photocatalytic adsorbent system prepared from bentonite clay and titanium dioxide was used for the adsorption/degradation of model organic pollutants and adsorption of heavy metals from industrial wastewater. The...

La-Doped ZnTiO3/TiO2 Nanocomposite Supported on Ecuadorian Diatomaceous Earth as a Highly Efficient Photocatalyst Driven by Solar Light

Currently, there is great interest in the use of TiO2 for photocatalytic remediation of wastewater. Doping, heterojunction, and immobilization on porous materials are effective methods to improve the photocatalytic efficiency of this semiconductor oxide. In this study, ZnTiO3/TiO2 (ZTO) and ZnTiO3/TiO2/La (ZTO/La) nanocomposites were successfully prepared and immobilized on diatomaceous earth (DE). The composition and texture of the composites prepared were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM-EDX), and specific surface area (SSA). The adsorption capacity and photocatalytic activity of the composites were determined via degradation of methylene blue (MB) in batch reactors. The materials evaluated were prepared in the shape of 0.2 cm (diameter) and 1.0 cm (length) cylindrical extrudates. The results indicate that the ZTO/La-DE composite exhibited higher efficiency for the removal of MB under solar irradiation than both ZTO-DE and DE. The pseudo-second-order model and the Langmuir isotherm model were better suited to explain the adsorption process. The highest degradation percentage of MB obtained was 96% after 150 min of irradiation. The results indicate that synthesized composite could be used for the removal of cationic dyes in wastewater.

Synthesis of a copper (II) metal-organic framework for photocatalytic degradation of rhodamine B dye in water

The Cu(II) metal-organic frameworks (MOFs) based on 1,3,5-benzenetricarboxylic acid (Cu₃(BTC)₂) was synthesized by the hydrothermal method. The synthesized Cu₃(BTC)₂ exhibited pyramid-shaped morphology and showing an average specific area of 32.16 m² g^-1. The Cu₃(BTC)₂ photocatalysts were characterized using Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), field emission scanning electron microscopy-energy-dispersive X-ray spectroscopy (FESEM-EDX), UV-Vis diffusive reflectance spectra, and Brunauer-Emmett-Teller (BET). The photocatalytic activity of Cu₃(BTC)₂ was examined on Rhodamine B (RhB) degradation under visible light irradiation. The outcomes displayed exceedingly enhanced photocatalytic activity under visible light. In addition, its recyclability was also confirmed for multiple cycles. The easiness of construction and high photocatalytic performance of Cu₃(BTC)₂ photocatalysts can be capable in environmental applications to treat water contamination.

Photocatalytic Treatment of Wastewater Containing Simultaneous Organic and Inorganic Pollution: Competition and Operating Parameters Effects

In the present study, methylene blue (MB) removal from aqueous solutions via the photocatalytic process using TiO2 as a catalyst in the presence of external ultra-violet light (UV) was investigated. The results of adsorption in the absence of UV radiation showed that adsorption reached an equilibrium state at 60 min. The experimental kinetic data were found to be well fitted by the pseudo-second-order model. Furthermore, the isotherm study suggested that dye uptake by TiO2 is a chemisorption process with a maximum retention capacity of 34.0 mg/g. The photodegradation of MB was then assessed under various experimental conditions. The related data showed that dye mineralization decreased when dye concentrations were increased and was favored at high pH values and low salt concentrations. The simultaneous presence of organic and inorganic pollution (Zinc) was also evaluated. The effect of the molar ratio Zn2+/MB+ in the solution at different pH values and NaCl concentrations was also monitored. The corresponding experimental results showed that at low values of Zn2+ in the solution (30 mg/L), the kinetic of the MB removal became faster until reaching an optimum at Zn2+/MB+ concentrations of 60/60 mg/L; it then slowed down for higher concentrations. The solutions’ carbon contents were measured during the degradation process and showed total mineralization after about 5 h for the optimal Zn2+/MB+ condition.

DFT Study of Methylene Blue Adsorption on ZnTiO3 and TiO2 Surfaces (101)

The search for alternative materials with high dye adsorption capacity, such as methylene blue (MB), remains the focus of current studies. This computational study focuses on oxides ZnTiO₃ and TiO₂ (anatase phase) and on their adsorptive properties. Computational calculations based on DFT methods were performed using the Viena Ab initio Simulation Package (VASP) code to study the electronic properties of these oxides. The bandgap energy values calculated by the Hubbard U (GGA + U) method for ZnTiO₃ and TiO₂ were 3.17 and 3.21 eV, respectively, which are consistent with the experimental data. The most favorable orientation of the MB adsorbed on the surface (101) of both oxides is semi-perpendicular. Stronger adsorption was observed on the ZnTiO₃ surface (−282.05 kJ/mol) than on TiO₂ (–10.95 kJ/mol). Anchoring of the MB molecule on both surfaces was carried out by means of two protons in a bidentate chelating (BC) adsorption model. The high adsorption energy of the MB dye on the ZnTiO₃ surface shows the potential value of using this mixed oxide as a dye adsorbent for several technological and environmental applications.

The effect of graphitized carbon on the adsorption and photocatalytic degradation of methylene blue over TiO2/C composites

The TiO₂/C composites with approximately 40 wt% of carbon were prepared by calcination of precursors, formed from a one-pot liquid phase reaction between Ti(SO₄)₂ and flour. All TiO₂/C composites displayed mesoporous structures with high BET surface areas (117-138 m² g^-1) and small crystal sizes of TiO₂ (8-27 nm). The contents of graphitic carbon and rutile TiO₂ increased, while the surface area and TiO₂ crystal size decreased for the TiO₂/C composite on increasing the calcination temperature from 650 to 800 °C; when calcinated at 800 °C, the anatase TiO₂ completely changed into rutile TiO₂ in the TiO₂/C composite. The TiO₂/C composite calcinated at higher temperatures exhibited better adsorptive and photocatalytic degradation performance in the removal of methylene blue (MB). For the entire rutile TiO₂/C-800 composite, the adsorption process of MB can be well described by the pseudo-second-order kinetic model and is governed by chemical adsorption with the maximum adsorption capacity value equal to about 15 mg g^-1. Under continuous illumination with a 254 nm UV lamp (15 W) for 3 h, the percentage of MB (14 mg l^-1) photocatalytic degradation on 50 mg of TiO₂/C-800 was 25.1% higher than that of the maximum adsorption removal. These results suggest that the graphitized carbon has a significant effect on the adsorptivity and photocatalytic activity of the TiO₂/C composite.

Adsorption and photocatalytic activity of Cu-doped cellulose nanofibers/nano-titanium dioxide for different types of dyes

Cu-doped cellulose nanofibers/nano-titanium dioxide (Cu-TOCN/TiO₂) photocatalysts were prepared by the hydrolysis-precipitation method using TiCl₄ as the source of titanium and cellulose nanofibers suspension as a reaction medium. The prepared photocatalysts were used to decolorize organic dyes (reactive brilliant red K-2BP and cationic red X-GRL) efficiently under the synergistic effect of simultaneous adsorption and photocatalysis. The combination of TOCN inhibited the growth of TiO₂ crystals, reduced agglomeration and increased the specific surface area. When compared with TiO₂, TOCN/TiO₂ improved the decolorization efficiency of the two dyes by 14.82% and 22.87%, respectively, under UV-light irradiation. The absorption edge exhibited red-shift from 380 to 410 nm after Cu doping. An excellent photocatalytic activity was recorded by 0.5 mol % Cu-TOCN/TiO₂ and the decolorization efficiency of the two dyes was further improved by 34.76% and 10.44% respectively, compared with no Cu doping. After 2 hours of irradiation, the decolorization efficiency reached 96.57% and 99.73% respectively, while under dark conditions, it was 47.64% and 91.56% for the two dyes. The degradation mechanism of the dyes was verified as the destruction of the azo chromophore and benzene ring. This work provides a potential method for the development of a novel adsorptive photocatalyst with excellent recyclability.

Synthesis of the ZnTiO3/TiO2 Nanocomposite Supported in Ecuadorian Clays for the Adsorption and Photocatalytic Removal of Methylene Blue Dye

Currently, the study of semiconductor materials is very promising for the photocatalytic remediation of hazardous organic substances present in the air and water. Various semiconductors have been investigated in this interesting photo-assisted methodology, among them metal oxides such as ZnO, TiO2 and their derivatives. In this study, ZnTiO3/TiO2 was synthesized by the sol-gel method using Ti(OC3H7)4 and Zn(CH3COO)2 · 2H2O as reagents. The role of several conditions such as synthesis temperature and TiO2:ZnO proportion on the morphology and purity of compounds obtained was studied, and the suitable conditions for the synthesis of photocatalysts were determined. Various techniques were used to conduct a systematic investigation on the structural, morphological, and photocatalytic properties of ZnTiO3/TiO2. Scanning Electron Microscopy (SEM) images show that ZnTiO3/TiO2 have a typical particle size of approximately 100 nm with a quasi-spherical shape. The adsorption and photocatalytic activity were investigated by the decolorization of Methylene Blue (MB) as an organic contaminant under UV irradiation both in TiO2 and ZnTiO3/TiO2 supported over some Ecuadorian clays. The materials evaluated were prepared in the shape of 0.2 cm (diameter) and 1.0 cm (length) cylindrical extrudates. The degradation percentage of MB obtained was 85% approximately after 150 min of irradiation. The results obtained allow us to conclude that these synthesized materials can be used as adsorbents and photocatalysts.

Structural characterization of Argania spinosa Moroccan wooden artifacts during natural degradation progress using infrared spectroscopy (ATR-FTIR) and X-Ray diffraction (XRD)

The present work is focused on spectroscopic study of four samples of Argan wooden artifact pertaining to the 17^th, 18^th, 20^th and 21^st centuries. The objective is to characterize their unknown structures by the study of their non degraded parts and to investigate changes occurred in their degraded parts due to the natural degradation process. Attenuated total reflectance Fourier transform infrared spectroscopy gauges the presence of many functional groups related to cellulose I and/or II (OH, C–O–C and –CH₂), hemicelluloses (particularly C=O acetoxy ester band at 1732 cm⁻¹), and lignin (OH phenolic, C_ar-O and C=C_ar) and provides qualitative information on the state of wood alteration by informing on the evolution of new former C=O bands. The degree of conversion to carbonyl group, especially quinone or p-quinone at 1650 cm⁻¹, is correlated to lignin degradation, while the absence of the C=O acetoxy absorption is ascribable to occurred deterioration in hemicelluloses, and partial degradation of cellulose with enhancement of the C=O region between 1730-1630 cm⁻¹. X-ray diffraction determines the presence of two forms of cellulose; amorphous cellulose at 18.5° 2θ and predominant crystalline cellulose I_β at 2θ = 22.6° which characterized by an intense peak. The decrease of crystallinity index values confirms the deterioration level and obvious changes in crystallinity level. However, the microcrystalline structure appears unaltered because no significant changes were observed for calculated cristallite seize. The obtained results depend on the prolonged time of ageing, natural deterioration phenomena, and wood part (internal or external) that is exposed to degradation. The combination of these two methods is useful for an accurate estimation of the degradation level of argan wood.

Highly adsorptive chitosan/saponin-bentonite composite film for removal of methyl orange and Cr(VI)

Robust and simple composite films for the removal of methyl orange (MO) and Cr(VI) have been prepared by combining chitosan, saponin, and bentonite at a specific ratio. There are several composite films (chitosan-saponin-bentonite (CSB)) prepared; among them, the composite films CSB_2:3 and CSB_1:1 have the highest removal efficiency toward MO and Cr(VI) where the maximum removal is 70.4% (pH 4.80) and 92.3% (pH 5.30), respectively. It was found that different types of adsorbate have different thermodynamic properties of the adsorption process; the adsorption of MO onto CSB_2:3, chitosan, and acid-activated bentonite (AAB) proceeded endothermically, while the adsorption of Cr(VI) onto CSB_1:1, chitosan, and AAB proceeded exothermically. The parameters of the adsorption were modeled by using isotherm and kinetic equations. The models of Langmuir, Freundlich, Redlich-Peterson, Sips, and Toth were used for fitting the adsorption isotherm data at a temperature of 30, 45, and 60 °C; all of the isotherm models could represent the data well. The result indicates that CSB_2:3 has the highest adsorption capacity toward MO with q_m of 360.90 mg g^-1 at 60 °C; meanwhile, CSB_1:1 has the highest adsorption capacity toward Cr(VI) with q_m 641.99 mg g^-1 at 30 °C. The pseudo-second-order model could represent the adsorption kinetics data better than the pseudo-first-order equation. The adsorption mechanism was proposed, and the thermodynamic properties of the adsorption were also studied.