Synthesis of TiO2-Activated Carbon from Coffee Dregs by Hydrothermal Method for Photodegradation of Diazinon

In this work, TiO(2) nanoparticles in anatase phase was prepared by sol-gel low temperature method from titanium tetra-isopropoxide (TTIP) as titanium precursor in the presence of acetic acid (AcOH). The effects of synthesis parameters such as AcOH and water ratios, sol formation time, synthesis and calcination temperature on the photocatalytic activity of TiO(2) nanoparticles were evaluated. The resulting nanoparticles were characterized by X-ray diffraction, UV-Vis reflectance spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller techniques. Photocatalytic activity of anatase TiO(2) nanoparticles determined in the removal of C. I. Acid Red 27 (AR27) under UV light irradiation. Results indicate that with increasing AcOH/TTIP molar ratio from 1 to 10, sol formation time from 1 to 3 h and synthesis temperature from 0 to 25°C, increases crystallite size of synthesized nanoparticles. It was found that optimal conditions for low temperature preparation of anatase-type TiO(2) nanoparticles with high photocatalytic activity were as follows: TTIP:AcOH:water molar ratio 1:1:200, sol formation time 1 h, synthesis temperature 0°C and calcination temperature 450°C.

Controllable synthesis of nanomaterials with different morphologies can significantly affect their properties. Here we report that the morphology and facet orientation of TiO2 nanocrystals can be readily modulated via a hydrothermal method using a simple morphology-controlling agent of NH4F. The photocatalytic activity of resultant TiO2 has been evaluated by photodegradation of methyl orange. The results indicate that the introduction of NH4F can be used to modulate the mophology and, thereby, the photocatalytic activity of TiO2. The obtained TiO2 with high-energy facet, small size, and large surface area can exhibit an improved photocatalytic efficiency, which may be promising for real application.

Contamination of organic and inorganic substances in water, such as heavy metal ions and dyes, is found in almost every country, including developed and developing countries. The presence of these pollutants in the environment frequently resulted in negative effects on the human body and also ecosystem. So far, many technologies to remove pollutants, filtration, precipitation, ion exchange, phytoremediation, adsorption, and so on have been developed. Among these, adsorption is regarded as one of the most promising methods due to its high adsorption capacity and easiness of operation, and then many kinds of adsorbent materials have been researched. The most common adsorbent material used in many places is activated carbon; however, this adsorbent is quite expensive. This chapter introduces some environmentally friendly adsorbents, which are low-cost, safe, and non-harmful adsorbents based on natural products and solid waste materials. Especially, natural materials like plants, solid waste, and agricultural waste investigated in our laboratories are described here. Most of them have the large surface area and some useful functional groups for adsorbing, and then they originally have the high adsorption capacity for pollutants. The treatment of the adsorbents with chemicals like citric acid and phosphoric acid improved their adsorption capacities for metal ions. Some agricultural waste, such as konjac glucomannan, spent coffee grounds, and biochar, have the ability to remove organic compounds and dyes from water. Furthermore, it is introduced that the fermented bark amendment from the thinning of cedar can suppress the uptake of cadmium ion in rice.KeywordsBiocharDrinking water treatment sludgeEnvironmentally friendly adsorbentFermented barkKonjac glucomannanPlatanus leafSpent coffee ground

The photocatalytic activity of TiO2 is limited by the aggregation of nanoparticles and the fast electron–hole pair recombination. Graphene sheets, with high specific surface area and unique electronic properties, can be used as a good support for TiO2 to enhance the photocatalytic activity. Herein, we prepared graphene–TiO2 (G–TiO2) composites through a one-pot solvothermal reaction by using graphite oxide (GO) and tetrabutyl titanate as starting materials. TiO2 particles with anatase phase and a narrow size distribution were dispersed on the surface of graphene sheets uniformly. The fluorescence quenching confirmed that graphene acted as an electron-acceptor material to effectively hinder the electron–hole pair recombination of TiO2. The product prepared with 30 mg of GO and 8 h of reaction time exhibited excellent photocatalysis to methylene blue (MB) degradation under irradiation of simulated sunlight. Such intriguing photocatalyst may find significant applications in various fields.

In this study, the effect of the synthesis method (solid state, sol-gel and hydrothermal) on the photocatalytic activity of the anatase and rutile phases of TiO2 was evaluated. As a result of XRD, FESEM and BET analysis of pure phase TiO2 powders in anatase and rutile phases, the changes in particle structures, surface areas and morphologies were examined and the differences in both synthesis method and phase structures were evaluated with Photodegradation experiments. The results of the X-ray diffraction (XRD) analysis showed that the TiO2 compound synthesized in the anatase phase and by the synthesized hydrothermal method exhibited a much smaller crystal size than the other synthesis methods and the rutile phase. Surface morphology examinations of the samples were made with scanning electron microscopy (FESEM), particle sizes were determined in the range of 90-200 nm, and their surface areas were examined by Brunauer–Emmett–Teller (BET) analysis.The adsorption-desorption isotherms shown also support the XRD data of the highest surface area.The photocatalytic behavior of the compounds was investigated using methylene blue degradation.As a result of all the syntheses and characterization studies, it has been shown that TiO2 obtained by hydrothermal method exhibits the best photocatalytic activity.

Incorporation of TiO2 into cementitious materials is an important technology in the field of photocatalytic pollution mitigation; however, the photocatalytic activity of TiO2 is limited by specific surface area, poor gas diffusion and light transmission performance of cementitious materials. In this study, a novel photocatalytic lightweight aggregate—photocatalytic ceramsite sand (PCS) was synthesized by loading TiO2 on activated porous ceramsite sand (CS) with negative pressure method to solve problems in application of photocatalysts in cementitious materials. Photocatalytic cement material (PCM) was prepared by loading PCS on the surface of cementitious materials, which improved the photocatalytic activity and efficiency of TiO2 in cementitious materials. It was found that the pore structure (pore volume, size distribution and interconnectivity) of ceramsite sand (CS) varies with particle size. The photocatalytic removal rate of benzene on PCS increased significantly through adjusting ceramsite sands in appropriate pore structure and TiO2 at best coating ratio. The photocatalytic activity of PCS slightly decreased but still remained active after incorporated into concrete. 2 μL benzene was degraded completely in 200 min by 5 g 4PCS-1.25~2.35 and 300 min by PCM-5, and was still degraded over 80% in 400 min by PCM-5 after exposure to natural environment for 6 months. The results suggested that the photocatalytic activity of TiO2 in cementitious materials was enhanced by the preparation of PCS and PCM, which could provide more gas diffusion, higher specific surface area, more TiO2 active sites, and prevent TiO2 particles from being influenced by the envelope of cement hydration products and the carbonation of cement.

By way of electrospinning followed by annealing at different temperatures, TiO 2 nanofibers with different phases have been successfully fabricated. The corresponding ultraviolet photocatalytic activity was evaluated using rhodamine B degradation as a probe reaction. The photocatalytic activity of TiO 2 nanofibers is found to be enhanced when annealed at higher temperatures with amount of anatase phase transformed to rutile. An optimal annealing temperature exists on the photocatalytic activity of TiO 2 nanofibers, which increases with the increasing of the calcination temperature up to 600°C and then decreases. According to their phase transformations monitored by X ‐ray diffraction, the different crystalline structures could be the reason for the enhanced photocatalytic activity of these electrospun TiO 2 nanofibers.

Easy synthesis of TiO 2 /g-C 3 N 4 heterostructure photocatalyst with large surface area and excellent photocatalytic activity

Specific surface area of titanium dioxide (TiO2) particles influences cyto- and photo-toxicity

The quality and safety of agricultural products are strongly related to human livelihood. Thus, the government and consumers have recently paid increased attention to the quality and safety of agricultural products. The development of efficient, rapid, and sensitive analytical methods for detecting pesticides, veterinary drugs, heavy metals, mycotoxins, and environmental pollutants in agricultural products is of great significance. Owing to the complexity of many sample matrices and the low concentration of pollutants in a typical sample, appropriate sample pretreatment steps are necessary to enrich pollutants in agricultural products. Solid-phase extraction (SPE) is the most widely used sample pretreatment technology; in this technique, the adsorbent generally determines the selectivity and efficiency of the extraction process. An increasing number of novel materials have been used as SPE adsorbents. The extraction efficiency, extraction selectivity, and analytical throughput of SPE could be greatly improved by combining these novel materials with various extraction modes (e. g., solid-phase microextraction, dispersed SPE, and magnetic SPE (MSPE)) during sample preparation. Because of their large specific surface area and high affinity toward target analytes, nanomaterials are often used as SPE adsorbents, thereby greatly improving the selectivity and sensitivity of the analytical technology. More importantly, these materials have become a priority area of research on preconcentration technologies for trace compounds in agricultural products. This paper summarizes the adsorption characteristics of several new nanomaterials, including magnetic materials, carbon-based materials, metal nanomaterials (MNs), metal oxide nanomaterials (MONs), metal organic frameworks (MOFs), and covalent organic frameworks (COFs). These nanomaterials present numerous advantages, such as large specific surface areas, high adsorption capacities, and tailorable structural designs. MSPE employs magnetic materials as sorbents to afford fast dispersion and efficient recycling when applied to complex sample matrices under an external magnetic field. The use of MSPE can avoid several typical problems associated with SPE such as poor adsorbent packing and high pressure, thereby greatly simplifying the pretreatment process and providing a high flux for sample analysis. Carbon-based materials are powdered or bulk nonmetallic solid materials with carbon as the main component; carbon and nitrogen materials, mesoporous carbon, carbon nanotubes, and graphene are some examples of these materials. These materials provide large specific surface areas, abundant pore structures, good thermal stability, high mechanical strength and adsorption capacity, and controllable morphology. Pure and modified carbon nanomaterials have been successfully used to purify target analytes from agricultural products. Given their unique physical and chemical properties, MNs and MONs have attracted significant interest for use in sample preparation. MNs and MONs with excellent thermal and mechanical stabilities show good resistance to a wide pH range and diverse organic solvents, which is crucial in adsorbent-based extraction methods. The surface of these materials can be easily modified with various ligands to improve their selectivity. MOFs and COFs present many advantages such as large specific surface areas, high porosity, adjustable pore performance, and good thermal stability. Several methods that employ novel adsorbent materials to analyze pollutants in a variety of agricultural products, such as chromatography, spectroscopy, mass spectrometry, and other detection technologies, have been established. This paper also reviews the application of adsorbent materials in the analysis of agricultural product quality and safety, and discusses the future development trends of these sorbents in sample preparation for the safety analysis of agricultural products.

Photocatalytic activities of TiO 2 thin films prepared on Galvanized Iron substrate by plasma-enhanced atomic layer deposition

Developing a low-cost and well-recyclable adsorbent with high adsorption capacity is greatly desirable in dye wastewater treatment. Here, we demonstrate a kind of novel tough and reusable hydrogel beads with quite high capacity of dye adsorption via incorporating mussel-bioinspired poly(L-DOPA) (PDOPA) into alginate/poly(acrylamide) double network (DN) hydrogels. The synthesized PDOPA nanoaggregates were introduced into the DN hydrogels by simple one-pot mixing with the monomers prior to polymerization. The fabricated hydrogel beads exhibited high mechanical strength and good elastic recovery due to the interpenetrating Ca2+-alginate and poly(acrylamide) networks. It was shown that the beads exhibited relatively high dye adsorption capacity compared to other adsorbents reported in literature, and the introduction of PDOPA with an appropriate amount raised the adsorption capacity. It is believed that the addition of PDOPA and the matrix of double network architecture contributed synergistically to the high adsorption capacity of hydrogel beads. Moreover, the desorption of dyes could be easily realized via rinsing in acidic water and ethanol solution. The hydrogel beads remained the high adsorption capacity even after 5 times of adsorption and desorption cycles. This tough and stable hydrogel with high adsorption capacity may have potential in treatment of dye wastewater released by textile dyeing industry.

Synthesis and study of low-cost nitrogen-rich porous organic polyaminals for efficient adsorption of iodine and organic dye

TiO 2 nanomaterials were prepared by a sol-gel derived electrospinning, calcination from 500 o C to 650 o C, and subsequent mechanical grinding to investigate the effect of calcination temperature on crystal structure, crystallinity, and photocatalytic activity of methylene blue (MB). XRD results indicated that TiO 2 nanorods calcined at 500 o C is composed of anatase TiO 2 only. However, mixed crystals of anatase and rutile were observed for TiO 2 calcined above 550 o C. Higher MB degradation was found for the TiO 2 nanorods calcined at 550 o C probably due to the mixed crystals and larger surface area. However, the improved photocatalytic activity was achieved for TiO 2 nanotube due to the synergic combinations of mixed crystals, larger specific surface area, and light trapping effect. Keywords: TiO 2 , nanofiber, nanorod, nanotube, photocatalytic activity, methylene blue 1. INTRODUCTION TiO 2 photocatalysts have been investigated extensively for envi ronmental applications such as air, water treatment and deodorizer, because of its strong oxidizing power, high photocatalytic activity, self-cleaning function, bactericidal and detoxification activity.

Immobilization of KTS-3 on an electrospun fiber membrane for efficient removal of Cs+ and Sr2+