Photocatalytic ozonation of dimethyl phthalate with TiO2 prepared by a hydrothermal method

Adsorptive removal of dimethyl phthalate using peanut shell-derived biochar from aqueous solutions: equilibrium, kinetics, and mechanistic studies

Rise in polymer industry and extensive use of their products leads to leaching of phthalate esters and distributed into the different matrices of the environment. This chemical group has the potential to hamper the life of living organisms and ecosystem. Thus, it is essential to develop cost-effective adsorbents capable of removing these harmful compounds from the environment. In this work, peanut hull-derived biochar was taken as the adsorbent, and DMP was selected as the model pollutant or adsorbates. The biochars of different properties were produced at three pyrolysis temperatures (i.e., 450, 550, and 650 °C) to check how temperature affected the adsorbent properties and adsorption performance. Consequently, the performance of biochars for DMP adsorption was thoroughly studied by the combination of experiments and compared with commercial activated carbon (CAC). All the adsorbents are meticulously characterized using various analytical techniques and used for adsorption DMP from aqueous solutions. The results suggested that adsorption was favoring chemisorption with multi-layered adsorption as adsorption kinetics and isotherm are in good alignment with pseudo-second-order kinetics and Freundlich isotherm, respectively. Further, thermodynamic study revealed DMP adsorption on adsorbent is physically spontaneous and endothermic. The removal efficiency order of four adsorbent was as follows: BC650 > CAC > BC550 > BC450 with maximum efficiency of 98.8% for BC650 followed by 98.6% for CAC at optimum conditions. And as it is a short carbon chain PAE, dominant mechanisms of adsorption for DMP onto porous biochar were H-bonding, π-π EDA interactions, and diffusion within the pore spaces. Therefore, this study can provide strategies for the synthesis of biochar for effectively removing DMP from aqueous solution.

Advanced oxidation processes for the removal of phthalate esters (PAEs) in aqueous matrices: a review

Over the past few decades, phthalate esters (PAEs) used as additives to improve the persistence and flexibility of polymeric materials. They are also used in cosmetics, insect repellents, and propellants, and their continuous input into drinking waters has constituted a serious risk to human health and the environment. DBPs are compounds classified as hazardous substances and have teratogenic properties. Due to the high bioaccumulation of DBP, they have toxic properties in different organisms, making it very important to remove PAEs before discharging them into environments. In this study a systematic review was designed to evaluate Advanced oxidation processes (AOPs) studies which have successfully treated contaminated water with PAEs. Among AOPs, particularly photocatalytic, UV/H₂O₂ photolysis, sonolysis, and ozone-based processes were more tried to degrade PAEs in aqueous solutions. Additionally, a more detail of each AOPs was explained. Findings showed that all advanced oxidation processes, especially combined AOPs have good results in the degradation of PAEs in water.

Remediation of phthalate acid esters from contaminated environment—Insights on the bioremedial approaches and future perspectives

Phthalates are well-known emerging pollutants that are toxic to the environment and human health. Phthalates are lipophilic chemicals used as plasticizers in many of the items for improving their material properties. These compounds are not chemically bound and are released to the surroundings directly. Phthalate acid esters (PAEs) are endocrine disruptors and can interfere with hormones, which can cause issues with development and reproduction, thus there is a huge concern over their existence in various ecological surroundings. The purpose of this review is to explore the occurrence, fate, and concentration of phthalates in various environmental matrices. This article also covers the phthalate degradation process, mechanism, and outcomes. Besides the conventional treatment technology, the paper also aims at the recent advancements in various physical, chemical, and biological approaches developed for phthalate degradation. In this paper, a special focus has been given on the diverse microbial entities and their bioremedial mechanisms executes the PAEs removal. Critically, the analyses method for determining intermediate products generated during phthalate biotransformation have been discussed. Concluisvely, the challenges, limitations, knowledge gaps and future opportunities of bioremediation and their significant role in ecology have also been highlighted.

Compound-specific isotopic analysis to characterize the photocatalytic reaction of TiO2 nanoparticles with diethyl phthalate

In this study compound-specific isotope analysis (CSIA) has been used to explore the degradation mechanism of nano titanium dioxide (TiO₂) catalyzes photodegradation of diethyl phthalate (DEP). TiO₂ is a popular photosensitizer with potential in waste water treatment and application in advanced oxidation processes. The degradation process of DEP can be described with a first-order kinetics in the applied concentration ranges. The larger degradation rate constant has been found at neutral conditions. The ¹³C and ²H isotope fractionation associated with the nano TiO₂ catalyzes photodegradation of DEP at pH 3, 7 and 11 yield normal isotope effects. In the TiO₂/UV/DEP and TiO₂/H₂O₂/UV/DEP systems, the correlation of ¹³C and ²H fractionation (Λ) were calculated to be 2.7 ± 0.2, 2.8 ± 0.2 at pH 3, 2.2 ± 0.4, 2.5 ± 0.2, 2.3 ± 0.6 at pH 7 and 2.6 ± 0.3, 2.2 ± 0.3, 2.7 ± 0.2 and 2.3 ± 0.3 at pH11, respectively. The dominant free radical species in studied systems were explored by combining free radical quenching method and electron paramagnetic resonance analysis. The hydroxyl radicals have been found as the main radical species at all pH conditions studied. Furthermore, the ¹³C and ²H fractionation suggested that the addition of •OH on the benzene ring of DEP is the main conversion pathway. Therefore, CSIA is a promising technology for the identification of reaction pathways of DEP for example in water treatment systems.

Insights into the Titania (TiO2) Photocatalysis on the Removal of Phthalic Acid Esters (PAEs) in Water

In this era of globalization, plastic is regarded as one of the most versatile innovations, finding its uses ranging from packaging, automotive, agriculture, and construction to the medical and pharmaceutical industries. Unfortunately, the single-use nature of plastics leads to ecological and environmental problems. Among conventional disposal management of plastic waste are landfilling dumping, incineration, and recycling. However, not all plastic waste goes into disposal management and ends up accumulating in lakes, rivers, and seas. In the aquatic environment, the action of photochemical weathering plastics has resulted in the release of chemical additives such as phthalic acid esters (PAEs), an important plasticizer added to plastic products to improve their softness, flexibility, and durability. Nowadays, PAEs have been ubiquitously detected in our environment and numerous organisms are exposed to PAEs to some extent. As PAEs carry endocrine disruptive and carcinogenicity properties, an urgent search for the development of an efficient and effective method to remove PAEs from the environment is needed. As a viable option, titania (TiO2) photocatalysis is a promising tool to combat the PAEs contamination in our environment owing to its high photocatalytic activity, cost-effectiveness, and its ability to totally mineralize PAEs into carbon dioxide and water. Hence, this paper aims to highlight the concerning issue of the contamination of PAEs in our aquatic environments and the summary of the removal of PAEs by TiO2 photocatalysis. This review concerning the significance of knowledge on environmental PAEs would hopefully spark huge interest and future development to tackle this plastic-associated pollutant. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Photocatalytic Activity Induced by Metal Nanoparticles Synthesized by Sustainable Approaches: A Comprehensive Review

Nanotechnology is a fast-expanding area with a wide range of applications in science, engineering, health, pharmacy, and other fields. Among many techniques that are employed toward the production of nanoparticles, synthesis using green technologies is the simplest and environment friendly. Nanoparticles produced from plant extracts have become a very popular subject of study in recent decades due to their diverse advantages such as low-cost synthesis, product stability, and ecofriendly protocols. These merits have prompted the development of nanoparticles from a variety of sources, including bacteria, fungi, algae, proteins, enzymes, etc., allowing for large-scale production with minimal contamination. However, nanoparticles obtained from plant extracts and phytochemicals exhibit greater reduction and stabilization and hence have proven the diversity of properties, like catalyst/photocatalyst, magnetic, antibacterial, cytotoxicity, circulating tumor deoxy ribo nucleic acid (CT-DNA) binding, gas sensing, etc. In the current scenario, nanoparticles can also play a critical role in cleaning wastewater and making it viable for a variety of operations. Nano-sized photocatalysts have a great scope toward the removal of large pollutants like organic dyes, heavy metals, and pesticides in an eco-friendly and sustainable manner from industrial effluents. Thus, in this review article, we discuss the synthesis of several metal nanoparticles using diverse plant extracts, as well as their characterization via techniques like UV–vis (ultraviolet–visible), XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), FTIR (Fourier transform infrared spectroscopy), etc., and catalytic activity on various hazardous systems.

Current Developments in the Effective Removal of Environmental Pollutants through Photocatalytic Degradation Using Nanomaterials

Photocatalysis plays a prominent role in the protection of the environment from recalcitrant pollutants by reducing hazardous wastes. Among the different methods of choice, photocatalysis mediated through nanomaterials is the most widely used and economical method for removing pollutants from wastewater. Recently, worldwide researchers focused their research on eco-friendly and sustainable environmental aspects. Wastewater contamination is one of the major threats coming from industrial processes, compared to other environmental issues. Much research is concerned with the advanced development of technology for treating wastewater discharged from various industries. Water treatment using photocatalysis is prominent because of its degradation capacity to convert pollutants into non-toxic biodegradable products. Photocatalysts are cheap, and are now emerging slowly in the research field. This review paper elaborates in detail on the metal oxides used as a nano photocatalysts in the various type of pollutant degradation. The progress of research into metal oxide nanoparticles, and their application as photocatalysts in organic pollutant degradation, were highlighted. As a final consideration, the challenges and future perspectives of photocatalysts were analyzed. The application of nano-based materials can be a new horizon in the use of photocatalysts in the near future for organic pollutant degradation.

Remediation strategies for mitigation of phthalate pollution: Challenges and future perspectives

Phthalates are a group of emerging xenobiotic compounds commonly used as plasticizers. In recent times, there has been an increasing concern over the risk of phthalate exposure leading to adverse effects to human health and the environment. Therefore, it is necessary to not only understand the current status of phthalate pollution, their sources, exposure routes and health impacts, but also identify remediation technologies for mitigating phthalate pollution. Present review article aims to inform its readers about the ever increasing data on health burdens posed by phthalates and simultaneously highlights the recent advancements in research to alleviate phthalate contamination from environment. The article enumerates the major phthalates in use today, traces their environmental fate, addresses their growing health hazard concerns and largely focus on to provide an in-depth understanding of the different physical, chemical and biological treatment methods currently being used or under research for alleviating the risk of phthalate pollution, their challenges and the future research perspectives.

Removal of phthalates from aqueous solution by semiconductor photocatalysis: A review

While phthalate esters are commonly used as plasticizers to improve the flexibility and workability of polymeric materials, their presence and detection in various environments has become a significant concern. Phthalate esters are known to have endocrine-disrupting effects, which affects reproductive health and physical development. As a result, there is now increased focus and urgency to develop effective and energy efficient technologies capable of removing these harmful compounds from the environment. This review explores the use of semiconductor photocatalysis as an efficient and promising solution towards achieving removal and degradation of phthalate esters. A comprehensive review of photocatalysts reported in the literature demonstrates the range of materials including commercial TiO₂, solar activated catalysts and composite materials capable of enhancing adsorption and degradation. The degradation pathways and kinetics are also considered to provide the reader with an insight into the photocatalytic mechanism of removal. In addition, through the use of two key platforms (the technology readiness level scale and electrical energy per order), the crucial parameters associated with advancing photocatalysis for phthalate ester removal are discussed. These include enhanced surface interaction, catalyst platform development, improved light delivery systems and overall system energy requirements with a view towards pilot scale and industrial deployment.

Efficient photocatalytic removal of phthalates easily implemented over a bi-functional {001}TiO2 surface

It is stubborn to remove the lowly concentrated phthalic acid esters (PAEs) that usually coexist with other highly concentrated but low-toxic pollutants in municipal sewage. Herein, we report a novel strategy for completely removing the PAEs over a bi-functional {001}TiO₂ surface (with highly exposed {001} facet), which not only serve as functional sites to specifically adsorb the target PAEs pollutants, but also contribute to an enhanced oxidation ability. The adsorption behavior of PAEs on {001}TiO₂ is analyzed deeply through kinetic experiments combining with in situ ATR-FTIR spectroscopy and theoretical calculations. The results reveal that the adsorption capacities of PAEs on {001}TiO₂ are about 4-5 times higher than that on TiO₂, both of which follow the pseudo-second-order and Langmuir model. This is mainly attributed to the interfacial Lewis Acid-Base Pair between {001} facet Ti_5c sites and CO of PAEs. Benefitting from the specific adsorption capability toward target pollutant and enhanced oxidation ability of {001} facets, nearly 100% of DMP or DEP in simulated wastewater can be eliminated by {001}TiO₂ within 2 h illumination, and the relevant degradation rate constants (k) (3.67 h^-1 for DMP and 2.19 h^-1 for DEP) are 5.73 and 3.08 folds higher than that of pure TiO₂, respectively. In the application of municipal wastewater, nearly 76% of DMP and 85% DEP can be eliminated by {001}TiO₂ within 2 h illumination, which are nearly 3-6 fold higher than that of pure TiO₂.

Photocatalytic Advanced Oxidation Processes for Water Treatment: Recent Advances and Perspective

Nowadays, an ever-increasing variety of organic contaminants in water has caused hazards to the ecological environment and human health. Many of them are persistent and non-biodegradable. Various techniques have been studied for sewage treatment, including biological, physical and chemical methods. Photocatalytic advanced oxidation processes (AOPs) have received increasing attention due to their fast reaction rates and strong oxidation capability, low cost compared with the non-photolytic AOPs. This review is dedicated to summarizing up-to-date research progress in photocatalytic AOPs, such as Fenton or Fenton-like reaction, ozonation and sulfate radical-based advanced oxidation processes. Mechanisms and activation processes are discussed. Then, the paper summarizes photocatalytic materials and modification strategies, including defect chemistry, morphology control, heterostructure design, noble metal deposition. The future perspectives and challenges are also discussed.

Enhanced biodegradation of an endocrine disrupting micro-pollutant: Di (2-ethylhexyl) phthalate using biogenic self-assembled monolayer of silver nanoparticles

Di (2-ethylhexyl) phthalate (DEHP) is one of the predominant plasticizer and an endocrine disrupting chemical occurring almost in all partitions of the environment. Though DEHP occur at lower concentration, reluctance arises due to their ability to disrupt endocrine system even lower concentration. In the present study, DEHP was assessed for degradation at minimal level (1-100 μg L^-1) by a novel bacterial strain, Rhodococcus jostii PEVJ9. In the experimental design, significant variables were concentration of silver nitrate and DEHP, pH, temperature, time and agitation. Degradation without SAM-silver nanoparticles was 30-66% (predicted value = 30.8-66.8%, R² = 99.7%) while, degradation in the presence of SAM-silver nanoparticles onto bacterial cells was 100% (predicted value = 98.4-102.1%, R² = 99.6%) within 72 h. In short, this is the first report illustrating the experimental designs in biogenic synthesis of SAM-silver nanoparticles and enhanced degradation of DEHP at minimal level. The study overcomes poor bioavailability and assimilation of DEHP at lower concentration by the microbial population present in the environment. Thus, an efficient clean-up would prevent or minimize DEHP exposure at all trophic levels ranging from feminization of fishes to reproductive disorders in humans.

Novel Technology for the Removal of Brilliant Green from Water: Influence of Post-Oxidation, Environmental Conditions, and Capping

Chemical dyes are used in a wide range of anthropogenic activities and are generally not biodegradable. Hence, sustainable recycling processes are needed to avoid their accumulation in the environment. A one-step synthesis of Fe_core-maghemite_shell (Fe-MM) for facile, instantaneous, cost-effective, sustainable, and efficient removal of brilliant green (BG) dye from water has been reported here. The homogenous and monolayer type of adsorption is, to our knowledge, the most efficient, with a maximum uptake capacity of 1000 mg·g^-1, for BG on Fe-MM. This adsorbent was shown to be efficient in occurring in time-scales of seconds and to be readily recyclable (ca. 91%). As iron/iron oxide possesses magnetic behavior, a strong magnet could be used to separate Fe-MM coated with BG. Thus, the recycling process required a minimum amount of energy. Capping Fe-MM by hydrophilic clay minerals further enhanced the BG uptake capacity, by reducing unwanted aggregation. Interestingly, capping the adsorbent by hydrophobic plastic (low-density polyethylene) had a completely inverse effect on clay minerals. BG removal using this method is found to be quite selective among the five common industrial dyes tested in this study. To shed light on the life cycle analysis of the composite in the environment, the influence of selected physicochemical factors (T, pH, hν, O₃, and NO₂) was examined, along with four types of water samples (melted snow, rain, river, and tap water). To evaluate the potential limitations of this technique, because of likely competitive reactions with metal ion contaminants in aquatic systems, additional experiments with 13 metal ions were performed. To decipher the adsorption mechanism, we deployed four reducing agents (NaBH₄, hydrazine, LiAlH₄, and polyphenols in green tea) and NaBH₄, exclusively, favored the generation of an efficient adsorbent via aerial oxidation. The drift of electron density from electron-rich Fe_core to maghemite shells was attributed to be responsible for the electrostatic adsorption of N⁺ in BG toward Fe-MM. This technology is deemed to be environmentally sustainable in environmental remediation, namely, in waste management protocol.

Degradation of dimethyl phthalate using a liquid phase plasma process with TiO2 photocatalysts

The liquid phase plasma (LPP) method with a TiO₂ photocatalyst and hydrogen peroxide was used to decompose dimethyl phthalate (DMP). As the applied voltage, pulse width, and frequency were increased, the rate of decomposition was increased and the decomposition rate was 63% for 180 min under plasma optimum conditions. The addition of TiO₂ photocatalyst and hydrogen peroxide increased the DMP decomposition reaction rate, but an excess cause a decrease in decomposition rate due to a decrease in conductivity, blocking of ultraviolet light, and scavenger effect. When the TiO₂ photocatalyst and hydrogen peroxide were used together, the decomposition reaction rate of DMP was greatly improved by using LPP single process alone. Also, when all the processes were used at the same time, the decomposition reaction rate was improved to about 2.8 times. DMP undergoes bond cleavage and ultimately decomposes into CO₂ and H₂O via dimethyl 4-hydroxyphthalate and methyl salicylates due to hydroxyl radicals and various active species generated by the LPP reaction.

Automated on-line monitoring of the TiO2-based photocatalytic degradation of dimethyl phthalate and diethyl phthalate

An automated on-line system for monitoring the TiO₂-based photocatalytic degradation of dimethyl phthalate and diethyl phthalate.

Design and evaluation of a compact photocatalytic reactor for water treatment

A compact reactor for photocatalytic oxidation and photocatalytic ozonation water treatment was developed and evaluated by using four model pollutants. Additionally, combinations of pollutants were evaluated. Specially produced Al₂O₃ porous reticulated monolith foams served as TiO₂ carriers, offering a high surface area support. UV lamps were placed in the interior to achieve reduced dimensions of the reactor (12 cm in diameter × 20 cm in height). Despite its small size, the overall photocatalytic cleaning capacity was substantial. It was evaluated by measuring the degradation of LAS + PBIS and RB19 as representatives of surfactants and textile dyes, respectively. These contaminants are commonly found in household grey wastewater with phenol as a trace contaminant. Three different commercial photocatalysts and one mixture of photocatalysts (P25, P90, PC500 and P25 + PC500) were introduced in the sol-gel processing and immobilized on foamed Al₂O₃ monoliths. RB19 and phenol were easily degradable, while LAS and PBIS were more resistant. The experiments were conducted at neutral-acidic pH because alkaline pH negatively influences both photocatalyic ozonation (PCOZ) and photocatalysis. The synergistic effect of PCOZ was generally much more expressed in mineralization reactions. Total organic carbon TOC half lives were in the range of between 13 and 43 min in the case of individual pollutants in double-deionized water. However, for the mixed pollutants in tap water, the TOC half-life only increased to 53 min with the most efficient catalyst (P90). In comparison to photocatalysis, the PCOZ process is more suitable for treating wastewater with a high loading of organic pollutants due to its higher cleaning capacity. Therefore, PCOZ may prove more effective in industrial applications.

Removal of dimethyl phthalate from water by ozone microbubbles

This work investigates the removal of dimethyl phthalate (DMP) from water using ozone microbubbles in a pilot plant of 20 dm³ capacity. Experiments were performed under various reaction conditions to examine the effects of the initial concentration of DMP, pH of the medium, ozone generation rate, and the role of H₂O₂ on the removal of DMP. The DMP present in water was effectively removed by the ozone microbubbles. The removal was effective in neutral and alkaline media. Increase in the initial concentration of the target pollutant negatively affected its removal efficiency. The removal efficiency dramatically increased from 1% to 99% when the ozone generation rate was increased from 0.28 to 1.94 mg s^-1 at pH 7. The total organic carbon measurements revealed that a complete mineralization of DMP was achieved within 1.8 ks at the high ozone feed rate. The use of t-butyl alcohol as the hydroxyl radical scavenger confirmed that the reaction between the target organic compound and ·OH radical dominated over its direct reaction with ozone. The reaction between DMP and ozone followed an overall second-order kinetics. The volumetric mass transfer coefficient of ozone in the reacting system and the enhancement factor increased with increasing initial concentration of DMP. Very low values of Hatta number were obtained at all initial concentrations of DMP and pH, which show that the mass transfer resistance was small.

Preparation and Application of Immobilized Surfactant-Modified PANi-CNT/TiO₂ under Visible-Light Irradiation

Hydrothermally and sol-gel-synthesized immobilized surfactant-modified polyaniline-carbon nanotubes/TiO₂ (PANi-CNT/TiO₂) photocatalysts were prepared and their application in the degradation of diethyl phthalate (DEP) under visible light at 410 nm was investigated in this sturdy. To improve the dispersion of nanoparticles and the transfer of electrons, the TiO₂ surface was modified with both sodium dodecyl sulfate (SDS) and functionalized carbon nanotubes (CNT-COOH and CNT-COCl). With the addition of PANi, which was increased from 1–5%, the adsorption edge of the prepared photocatalysts shifted to 442 nm. The SDS linked the PANi polymers to achieve a thickness of coating of the film of up to 314–400 nm and 1301–1600 nm for sol-gel hydrolysis and hydrothermally-synthesized photocatalysts, respectively. An appropriate film thickness would extend the transfer path of the electrons and inhibit the recombination of the electrons and the electron-holes. The photo-degradation performance of DEP by the hydrothermally-synthesized photocatalysts was better than those by sol-gel hydrolysis. The results revealed that the hydroxyl radicals were the key oxidant in the degradation of DEP using hydrothermally-synthesized PANi-CNT/TiO₂ photocatalysts. The morphology and functional groups of the raw materials of photocatalysts were characterized and a comparison of photocatalytic activity with other TiO₂-based photocatalysts was also provided.

Biodegradation of Dimethyl Phthalate by Freshwater Unicellular Cyanobacteria

The biodegradation characteristics of dimethyl phthalate (DMP) by three freshwater unicellular organisms were investigated in this study. The findings revealed that all the organisms were capable of metabolizing DMP; among them, Cyanothece sp. PCC7822 achieved the highest degradation efficiency. Lower concentration of DMP supported the growth of the Cyanobacteria; however, with the increase of DMP concentration growth of Cyanobacteria was inhibited remarkably. Phthalic acid (PA) was detected to be an intermediate degradation product of DMP and accumulated in the culture solution. The optimal initial pH value for the degradation was detected to be 9.0, which mitigated the decrease of pH resulting from the production of PA. The optimum temperature for DMP degradation of the three species of organisms is 30°C. After 72 hours' incubation, no more than 11.8% of the residual of DMP aggregated in Cyanobacteria cells while majority of DMP remained in the medium. Moreover, esterase was induced by DMP and the activity kept increasing during the degradation process. This suggested that esterase could assist in the degradation of DMP.

Environmental application of nanotechnology: air, soil, and water

Global deterioration of water, soil, and atmosphere by the release of toxic chemicals from the ongoing anthropogenic activities is becoming a serious problem throughout the world. This poses numerous issues relevant to ecosystem and human health that intensify the application challenges of conventional treatment technologies. Therefore, this review sheds the light on the recent progresses in nanotechnology and its vital role to encompass the imperative demand to monitor and treat the emerging hazardous wastes with lower cost, less energy, as well as higher efficiency. Essentially, the key aspects of this account are to briefly outline the advantages of nanotechnology over conventional treatment technologies and to relevantly highlight the treatment applications of some nanomaterials (e.g., carbon-based nanoparticles, antibacterial nanoparticles, and metal oxide nanoparticles) in the following environments: (1) air (treatment of greenhouse gases, volatile organic compounds, and bioaerosols via adsorption, photocatalytic degradation, thermal decomposition, and air filtration processes), (2) soil (application of nanomaterials as amendment agents for phytoremediation processes and utilization of stabilizers to enhance their performance), and (3) water (removal of organic pollutants, heavy metals, pathogens through adsorption, membrane processes, photocatalysis, and disinfection processes).

Enhancement of the photocatalytic activity of a TiO2/carbon aerogel based on a hydrophilic secondary pore structure

The surface/interface synergy effect plays a positive role on the spatial separation and utilization of electrons and holes in photocatalytic process, which suggests a potential strategy for designing high efficiency photocatalysts.

Decomposition and Mineralization of Dimethyl Phthalate in an Aqueous Solution by Wet Oxidation

Dimethyl phthalate (DMP) was treated via wet oxygen oxidation process (WOP). The decomposition efficiency η_DMP of DMP and mineralization efficiency η_TOC of total organic carbons were measured to evaluate the effects of operation parameters on the performance of WOP. The results revealed that reaction temperature T is the most affecting factor, with a higher T offering higher η_DMP and η_TOC as expected. The η_DMP increases as rotating speed increases from 300 to 500 rpm with stirring enhancement of gas liquid mass transfer. However, it exhibits reduction effect at 700 rpm due to purging of dissolved oxygen by overstirring. Regarding the effects of pressure P_T, a higher P_T provides more oxygen for the forward reaction with DMP, while overhigh P_T increases the absorption of gaseous products such as CO₂ and decomposes short-chain hydrocarbon fragments back into the solution thus hindering the forward reaction. For the tested P_T of 2.41 to 3.45 MPa, the results indicated that 2.41 MPa is appropriate. A longer reaction time of course gives better performance. At 500 rpm, 483 K, 2.41 MPa, and 180 min, the η_DMP and η_TOC are 93 and 36%, respectively.

Hydrotalcite-TiO2 magnetic iron oxide intercalated with the anionic surfactant dodecylsulfate in the photocatalytic degradation of methylene blue dye

The new magnetic photocatalysts HT/TiO2/Fe and HT-DS/TiO2/Fe, modified with the anionic surfactant sodium dodecylsulfate (DS) were successfully synthesized in this work. Titanium dioxide (anatase) followed by iron oxide were deposited on the hydrotalcite support. Several catalyst samples were prepared with different amounts of titanium and iron. The photocatalysts were characterized by infrared and Raman spectroscopy, X-ray diffraction, scanning electron microscopy. Photocatalytic performance was analyzed by UV-visible radiation (filter cutoff, λ > 300 nm) of an aqueous solution (24 mg/L) of methylene blue (MB). The most efficient catalyst was obtained at an iron oxide:TiO2 molar ratio of 2:3. This catalyst showed high photocatalytic activity, removing 96% of the color and 61% of total organic carbon from the MB solution after 120 min. It was easily removed from solution after use because of its magnetic properties. The reuse of the HT-DS/TiO2/Fe23 catalyst was viable and the catalyst was structurally stable for at least four consecutive photocatalytic cycles.

Organic pollutants removal in wastewater by heterogeneous photocatalytic ozonation

Heterogeneous photocatalysis and ozonation are robust advanced oxidation processes for eliminating organic contaminants in wastewater. The combination of these two methods is carried out in order to enhance the overall mineralization of refractory organics. An apparent synergism between heterogeneous photocatalysis and ozonation has been demonstrated in many literatures, which gives rise to an improvement of total organic carbon removal. The present overview dissects the heterogeneous catalysts and the influences of different operational parameters, followed by the discussion on the kinetics, mechanism, economic feasibility and future trends of this integrated technology. The enhanced oxidation rate mainly results from a large amount of hydroxyl radicals generated from a synergistically induced decomposition of dissolved ozone, besides superoxide ion radicals and the photo-induced holes. Six reaction pathways possibly exist for the generation of hydroxyl radicals in the reaction mechanism of heterogeneous photocatalytic ozonation.

Reaction mechanism and metal ion transformation in photocatalytic ozonation of phenol and oxalic acid with Ag(+)/TiO2

Photocatalytic ozonation of phenol and oxalic acid (OA) was conducted with a Ag(+)/TiO2 catalyst and different pathways were found for the degradation of different compounds. Ag(+) greatly promoted the photocatalytic degradation of contaminants due to its role as an electron scavenger. It also accelerated the removal rate of OA in ozonation and the simultaneous process for its complex reaction with oxalate. Phenol could be degraded both in direct ozonation and photolysis, but the TOC removal rates were much higher in the simultaneous processes due to the oxidation of hydroxyl radicals resulting from synergetic effects. The sequence of photo-illumination and ozone exposure in the combined process showed quite different effects in phenol degradation and TOC removal. The synergetic effects in different combined processes were found to be highly related to the properties of the target pollutants. The color change of the solution and TEM result confirmed that Ag(+) was easily reduced and deposited on the surface of TiO2 under photo-illumination, and dissolved again into solution in the presence of ozone. This simple cycle of enrichment and distribution of Ag(+) can greatly benefit the design of advanced oxidation processes, in which the sequences of ozone and photo-illumination can be varied according to the needs for catalyst recycling and the different properties of pollutants.

Enhancement of photocatalytic degradation of dimethyl phthalate with nano-TiO2 immobilized onto hydrophobic layered double hydroxides: a mechanism study

The organic layered double hydroxides (LHDs)/TiO(2) composites with various mass ratios were prepared by the reconstruction of mixed metal oxides to photodegrade dimethyl phthalate (DMP). The physicochemical properties of the obtained products were analyzed by X-ray diffraction (XRD) spectra, X-ray photoelectron spectra (XPS), UV-vis diffuse reflectance spectroscope and scanning electron microscope (SEM). The results showed that the TiO(2) particles and the organic LDHs were combined together through chemical bonds, and TiO(2) particles were well distributed on the surface of the interconnecting organic LDHs nano-flakes. According to the experimental results of adsorptive and photodegradation of DMP, the organic LDHs with flaky structure could effectively adsorb the DMP molecules and the adsorption isotherm by the composites modeled well with the Langmuir equation. The enrichment of DMP onto the composites and the external hydroxyl groups of the composites produce a synergistic effect leading to greatly enhance the rate of DMP photocatalytic degradation by the obtained composites.

Oxidative Degradation of Dimethyl Phthalate (DMP) by Persulfate Catalyzed by Ag+ Combined with Microwave Irradiation

The removal of dimethyl phthalate (DMP), which is a pollutant of concern in water environments, was carried out by sodium persulfate (SPS,Na2S2O8) catalyzed by Ag+combined with microwave irradiation. Effects of persulfate concentration, reaction time, microwave(MW) power and catalytic ion Ag+ on the degradation efficiency of DMP by persulfate were examined in batch experiments. The results showed that optimum Na2S2O8 concentration was 0.083mmol/L, and Ag+ concentration was 0.042 mmol/L. Increasing the MW irradiation time , persulfate concentration or Ag+ concentration might significantly accelerate DMP degradation. Catalytic ion Ag+combined with microwave irradiation was an rapid method to activate persulfate, and thus to produce SO4−• which was a powerful oxidant and could degrade DMP effectively. About 80% of DMP and 70% of COD could be degraded in 140s under the conditions of 800W MW power.

Environmental impact of phthalic acid esters and their removal from water and sediments by different technologies--a review

This article describes the most recent methods developed to remove phthalic acid esters (PAEs) from water, wastewater, sludge, and soil. In general, PAEs are considered to be endocrine disrupting chemicals (EDCs), whose effects may not appear until long after exposure. There are numerous methods for removing PAEs from the environment, including physical, chemical and biological treatments, advanced oxidation processes and combinations of these techniques. This review largely focuses on the treatment of PAEs in aqueous solutions but also reports on their treatment in soil and sludge, as well as their effects on human health and the environment.

Enhanced decomposition of dimethyl phthalate via molecular oxygen activated by Fe@Fe2O3/AC under microwave irradiation

In this study, we demonstrate that the decomposition of dimethyl phthalate under microwave irradiation could be greatly enhanced over Fe@Fe(2)O(3) nanowires supported on activated carbon (Fe@Fe(2)O(3)/AC). The great enhanced decomposition of dimethyl phthalate could be attributed to a unique microwave induced molecular oxygen activation process. Upon microwave irradiation, electrons could be transferred from activated carbon to zero-valent iron, and then react with molecular oxygen to form O(2)(-) and OH radicals for the decomposition of dimethyl phthalate. The deactivation and the regeneration of Fe@Fe(2)O(3)/AC catalyst were systematically studied. We also found that microwave heating could accelerate the electron transferring from AC to Fe@Fe(2)O(3) to generate more reactive oxygen species for the decomposition of DMP than conventional oil bath heating. This novel molecular oxygen activation approach may find applications for wastewater treatment and drinking water purification.

Removal of phthalates from aqueous solution by different adsorbents: a short review

This work presents a short review of adsorptive materials proposed and tested for removing phthalates from an aqueous environment. The objective is not to present an exhaustive review of all the types of adsorbents used, but to focus on selected types of "innovative" materials. Examples include modified activated carbon, chitosan and its modifications, β-cyclodextrin, and specific types of biomass, such as activated sludge from a wastewater treatment plant, seaweed and microbial cultures. Data from the literature do not confirm the existence of a broad-spectral adsorbent with high sorption efficiency, low production costs and environmentally friendly manufacture. According to the coefficients of Freundlich's isotherm, the most promising adsorbent of those mentioned in this work appears to be the biomass of activated sludge, or extracellular polysaccharides extracted from it. This material benefits from steady production, is cheap and readily available. Nevertheless, before putting it in practice, the treatment and adaptation of this raw material has to be taken into consideration.