Application of advanced oxidation processes and toxicity assessment of transformation products

Enhancement of wastewater treatment performance using 3D printed structures: A major focus on material composition, performance, challenges, and sustainable assessment

In order to enhance the performance and sustainability of wastewater treatment technologies, researchers are showing keen interest in the development of novel materials which can overcome the drawbacks associated with conventional materials. In this context, 3D printing gained significant attention due to its capability of fabricating complex geometrics using different material compositions. The present review focuses on recent advancements of 3D printing applications in various physicochemical and biological wastewater treatment techniques. In physicochemical treatment methods, substantial research has been aimed at fabricating feed spacers and other membrane parts, photocatalytic feed spacers, catalysts, scaffolds, monoliths, and capsules. Several advantages, such as membrane fouling mitigation, enhanced degradation efficiency, and recovery and reusability potential, have been associated with the aforementioned 3D printed materials. While in biofilm-based biological treatment methods, the use of 3D printed bio-carriers has led to enhanced mass transfer efficiency and microbial activities. Moreover, the application of these bio-carriers has shown better removal efficiency of chemical oxygen demand (∼90%), total nitrogen (∼73%), ammonia nitrogen (95%), and total phosphorous (∼100%). Although the removal efficiencies were comparable with conventional carriers, 3D printed carriers led to ∼40% reduction in hydraulic retention time, which could significantly save capital and operational expenditures. This review also emphasizes the challenges and sustainability aspects of 3D printing technology and outlines future recommendations which could be vital for further research in this field.

Recent advances on nanocellulose biomaterials for environmental health photoremediation: An overview

As one of the potential bionanomaterials, nanocellulose has appeared as a favorable candidate for photoremediation of the environment because of its abundance in nature, inexpensive, eco-friendly, decomposable, high surface area, and outstanding mechanical properties. The current review carefully summarized the diverse type of nanocellulose, their preparation approaches, and several previous works on the use of nanocellulose for photoremediation. These include the role of nanocellulose for the increased surface active site of the hybrid photocatalysts by providing a large surface area for enhanced adsorption of photons and pollutant molecules, as a dispersing agent to increase distribution of metal/non-metal dopants photocatalysts, as well as for controlled size and morphology of the dopants photocatalysts. Furthermore, the recommendations for upcoming research provided in this review are anticipated to ignite an idea for the development of other nanocellulose-based photocatalysts. Other than delivering beneficial information on the present growth of the nanocellulose biomaterials photocatalysts, this review is expected will attract more interest to the utilization of nanocellulose photocatalyst and distribute additional knowledge in this exciting area of environmental photoremediation. This could be attained by considering that a review on nanocellulose biomaterials for environmental health photoremediation has not been described elsewhere, notwithstanding intensive research works have been dedicated to this topic.

Removal mechanism of persistent organic pollutants by Fe-C micro-electrolysis

The degradation of persistent organic pollutants (POPs) in the simulated wastewaters was investigated by Fe-C micro-electrolysis system. With phenanthrene (PHE) and 2,4-dichlorophenol (2,4-DCP) as target pollutants, different iron-carbon (Fe-C) micro-electrolysis systems have been established. The effects of initial pH, Fe/C mass ratio, and intake air flow on the degradation and mineralization of PHE and 2,4-DCP were studied. At the initial pH of 5.0, Fe/C of 1.5:1, and an aeration flow rate of 1.5 L/min, after 120 min of reaction, the removal efficiency of FHE and COD was 94.3% and 73%, respectively. Under the conditions of initial pH is 3.0, Fe/C is 1:2, aeration flow rate of 1.5 L/min, and reaction time of 90 min, the best removal efficiency of 2,4-DCP can be obtained in the Fe-C micro-electrolysis system as 97% and COD removal efficiency can reach 76%. The results of kinetic studies show that the Fe-C micro-electrolysis process of PHE and 2,4-DCP follows pseudo-first-order kinetics. Commercial activated carbon (AC) was used for comparison under the same condition. The results indicated that the removal rate of organic pollutants and chemical oxygen demand (COD) of Fe-C micro-electrolysis were superior to that of AC. Analyze the structure of iron after reaction by SEM and XRD. The degradation pathway and mechanism for PHE and 2,4-DCP were proposed based on LC-MS analyses of treated wastewater.

Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do electrochemistry and photoredox catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) that enable bond formations not constrained by the rules of ionic or 2 electron (e) mechanisms. Instead, they enable 1e mechanisms capable of bypassing electronic or steric limitations and protecting group requirements, thus enabling synthetic chemists to disconnect molecules in new and different ways. However, while providing access to similar intermediates, electrochemistry and photoredox catalysis differ in several physical chemistry principles. Understanding those differences can be key to designing new transformations and forging new bond disconnections. This review aims to highlight these differences and similarities between electrochemistry and photoredox catalysis by comparing their underlying physical chemistry principles and describing their impact on electrochemical and photochemical methods.

Enhanced degradation of complex organic compounds in wastewater using different novel continuous flow non - Thermal pulsed corona plasma discharge reactors

The presence of pharmaceutically active compounds (PhAcs) in water bodies is a major concern due to their persistence, biological activity, and detrimental environmental effects. The present study focuses on the application of pulsed corona plasma technology to degrade such compounds. Three different plasma reactors, namely, sequential flow plasma reactor (SFR), continuous flow top discharge plasma reactor (TDPR) and continuous flow side discharge plasma reactor (SDPR), are designed and fabricated for their performance evaluation with respect to PhAC degradation. In all the reactors, wastewater was discharged as fine droplets for better interaction between the reactive oxidizing species (ROS) generated in the system and the pollutants. Enhanced degradation of the selected pharmaceutical compounds, i.e., diclofenac (DCF) and verapamil hydrochloride (VPL), is achieved with decreased treatment time and lower energy consumption. In SFR reactor water was recycled, whereas in continuous flow reactors hydraulic retention times (HRTs) were varied. The degradation efficiency of DCF (1 mg/L) and VPL (1 mg/L) was 99 % in SDPR, at HRTs of 9 and 12 min, respectively. Deposited energies (SFR- 71 W, TDPR - 92 W, SDPR- 51 W) varied due to the difference in reactor geometries. In the SDPR reactor, 99 % degradation of mixed pollutants with an initial concentration of 10 mg/L was achieved, at a HRT of 21 min. With an input power of 51 W, good energy efficiency (EEO) of 3.8 kWh/m³ and high yield (G) of 256.2 mg/kWh were obtained. . Nitrate formation was reduced by 73.2 % in TDPR and 85.0% in SDPR (32.1-8.6 mg/L) as compared to SFR (32.1 mg/L). The operating cost estimated was 0.71 $/m³, 0.80 $/m³ and 0.67 $/m³ for SFR, TDPR and SDPR, respectively. The results clearly indicate that the continuous flow reactor with side discharge is a viable alternative to traditional plasma reactors.

Recent advances on modified reticulated vitreous carbon for water and wastewater treatment - A mini-review

Recently, modifications on reticulated vitreous carbon (RVC) have attracted attention as a promising strategy to produce low-cost, stable, and highly active electrodes leading to significant advances in the water/wastewater treatment field compared with raw RVC. Modified RVC materials have been used as cathode, anode, and membrane. Improvements on physical and electrocatalytic properties are achieved by RVC modification via diverse strategies, including the deposition of metal oxides, the introduction of surface functional groups, and the formation of composites, which were used to remove organic contaminants and pathogens from water matrices, as summarized in this mini-review. This mini-review mainly focused on papers published from 2015 to 2020 that reported modified RVC electrodes to eliminate pollutants and pathogens from water matrices by electrochemical advanced oxidation processes. Likewise, news challenges and opportunities are discussed, and perspectives for the ongoing and future studies in this research field are also given.

Evaluation of Kinetic Pseudo-Order in the Photocatalytic Degradation of Ofloxacin

Ofloxacin is a highly efficient and widely used antibiotic drug. It is classified as a refractory pollutant due to its poor biodegradability. Consequently, it is commonly found in water sources, requiring efficient methods for its removal. Advanced oxidation processes (AOPs) offer efficient alternatives since those yield complete degradation not achieved in adsorption or membrane processes. Previous studies suggest ofloxacin degradation follows a pseudo-first or -second order processes, whereas for full removal of refractory pollutants—lower pseudo-orders are required. Monitoring the actual “pseudo-order” degradation kinetics of ofloxacin is needed to evaluate any proposed AOP process. This study presents a simple procedure to evaluate pseudo-orders of AOPs. Photolysis of 20 μM ofloxacin solutions follow pseudo-zero order kinetics, with half-life times (t1/2) of approx. 60 min. TiO2 heterogenous catalysts have been shown to have no influence at low concentrations (0.2 mg L−1), but a significant reduction of half-life time (t1/2 = 20 min) and increase in pseudo-order (0.8) is measured at 2.0 mg L−1. Similar results are obtained with homogenous catalysis by 2.0 mg L−1 H2O2. The combination of H2O2 and TiO2 catalysts shows additional reduction in half-time life with increase in the pseudo-order to 1.2. The conclusions are (1) heterogenous and homogenous photocatalysis can effectively degrade ofloxacin, (2) combined photocatalysis yields higher pseudo-order, being less prone to achieve full removal, and (3) analysis of specific pseudo-orders in AOPs of refractory pollutants helps to further elucidate the efficiency of the processes.

Efficient degradation of minocycline by natural bornite-activated hydrogen peroxide and persulfate: kinetics and mechanisms

Natural bornite (NBo), a sulfide mineral of copper and iron, is one of the main mineral raw materials for copper extraction. In this study, NBo-activated hydrogen peroxide (H₂O₂) and persulfate processes (PS) for the degradation of minocycline (MNC) in aqueous solution were systemically investigated and compared. The MNC removal rates with the NBo/PS and NBo/H₂O₂ processes were 86.40% and 87.50%, respectively. The mineralization rate of NBo/PS (33.96%) was higher than that of NBo/H₂O₂ (29.94%) after reaction for 180 min. The effects of oxidant and activator dosage, pH, common inorganic anions (i.e., Cl^-, NO₃^-, and HCO₃^-), and water composition on MNC degradation were systematically evaluated. In addition, the degradation of MNC in natural water matrix and toxicity evaluation was also studied to better evaluate the feasibility of practical application of those two processes. The results of free radical quenching experiments and electron paramagnetic resonance spectroscopy (EPR) showed that HO· was the main activated species in the NBo/H₂O₂ system, while SO₄^·- and HO· were the main activated species in the NBo/PS system. The degradation of MNC in the NBo/PS system was achieved through electron transfer, while the degradation of MNC in the NBo/H₂O₂ system was mainly achieved through free radical addition. The degradation pathway mainly included deamidation reactions, C-C bond breakage and hydroxylation. Reusability of NBo showed that NBo was considerably stable in activating PS and H₂O₂ for degradation of MNC, which was cost-effective activator. This work provides a new perspective on the degradation mechanism of pollutants by Fe-Cu bimetallic sulfide activation of PS and H₂O₂.

Heterogeneous photocatalysis of moxifloxacin at a pilot solar compound parabolic collector: Elimination of the genotoxicity

Photocatalysis has been applied for the elimination or reduction concentration of emerging pollutants in water. One of them, is the moxifloxacin (MOX), a fluoroquinolone that have a potential to develop resistant bacteria and have been present toxicity. The MOX achieves the environment due to inefficient wastewater treatment and incorrect disposal. Aiming to find a sustainable solution for photocatalytic process, compound parabolic concentrator (CPC) reactors have been proposed. In this sense, the present study investigates the application of CPC reactor for the degradation of MOX using sunlight and artificial light (UV-A lamp). In addition, the acute toxicity for L. sativa seeds and A. cepa bulbs, as well as the MOX cytotoxicity and genotoxicity for A. cepa root were investigated before and after treatment. The MOX degradation was around 65% using the sunlight and 44% with the artificial light. This difference was due to the kind of incident radiation (direct and diffuse), as well as the type of radiation (visible and/or ultraviolet) used in the processes. For L. sativa the acute toxicity was eliminated after MOX treatment using sunlight. A. cepa root length increased before the treatment and reduced significantly after it, what can indicate hormesis occurrence. MOX cytotoxicity was not observed. In contrast, genotoxicity assays showed high frequency of chromosomal aberrations for MOX solution, indicating elevated genotoxicity that was eliminated after solar treatment. The transformation products of MOX after CPC reactor solar treatment did not show cytotoxicity and genotoxicity in A. cepa and acute toxicity in L. Sativa. The results indicates that photocatalysis in a CPC solar reactor is efficient for MOX toxicity removal in the treated solutions.

Toxicity and removal of parabens from water: A critical review

Parabens are biocides used as preservatives in food, cosmetics and pharmaceuticals. They possess antibacterial and antifungal activity due to their ability to disrupt cell membrane and intracellular proteins, and cause changes in enzymatic activity of microbial cells. Water, one of our most valuable natural resource, has become a huge reservoir for parabens. Halogenated parabens from chlorination/ozonation of water contaminated with parabens have shown to be even more persistent in water than other types of parabens. Unfortunately, there is dearth of data on their (halogenated parabens) presence and fate in groundwater which serves as a major source of drinking water for a huge population in developing countries. An attempt to neglect the presence of parabens in water will expose man to it through ingestion of contaminated food and water. Although there are reviews on the occurrence, fate and behaviour of parabens in the environment, they largely omit toxicity and removal aspects. This review therefore, presents recent reports on the acute and chronic toxicity of parabens, their estrogenic agonistic and antagonistic activity and also their relationship with antimicrobial resistance. This article further X-rays several techniques that have been employed for the removal of parabens in water and their drawbacks including adsorption, biodegradation, membrane technology and advanced oxidation processes (AOPs). The heterogeneous photocatalytic process (one of the AOPs) appears to be more favoured for removal of parabens due to its ability to mineralize parabens in water. However, more work is needed to improve this ability of heterogeneous photocatalysts. Perspectives that will be relevant for future scientific studies and which will drive policy shift towards the presence of parabens in our drinking waters are also offered. It is hoped that this review will elicit some spontaneous actions from water professionals, scientists and policy makers alike that will provide more data, effective technologies, and adaptive policies that will address the growing threat of the presence of parabens in our environment with respect to human health.

Advanced Oxidation Processes Based on Sulfate Radicals for Wastewater Treatment: Research Trends

In this work, the recent trends in the application of the sulfate radical-based advanced oxidation processes (SR-AOPs) for the treatment of wastewater polluted with emerging contaminants (ECs) and pathogenic load were systematically studied due to the high oxidizing power ascribed to these technologies. Additionally, because of the economic benefits and the synergies presented in terms of efficiency in ECs degradation and pathogen inactivation, the combination of the referred to AOPs and conventional treatments, including biological processes, was covered. Finally, the barriers and limitations related to the implementation of SR-AOPs were described, highlighting the still scarce full-scale implementation and the high operating-costs associated, especially when solar energy cannot be used in the oxidation systems.

Reclaimed water driven lettuce cultivation in a hydroponic system: the need of micropollutant removal by advanced wastewater treatment

For a novel approach of resource-efficient water reuse, a municipal wastewater treatment plant was extended at pilot scale for advanced wastewater treatment, i.e., ozonation and biological activated carbon filtration, and a hydroponic system for reclaimed water driven lettuce cultivation. The treatment specific wastewater lines with the corresponding lettuce plants, differentiated into roots and shoots, were monitored for priority wastewater micropollutants, i.e., acesulfame (sweetener), caffeine (stimulant), carbamazepine, diclofenac, ibuprofen, sulfamethoxazole with acetyl-sulfamethoxazole (human pharmaceuticals), 1H-benzotriazole, and 4/5-methylbenzotriazole (industrial chemicals). As clearly demonstrated, conventional tertiary treatment could not efficiently clean up wastewater. Removal efficiencies ranged from 3% for carbamazepine to 100% for ibuprofen. The resulting pollution of the hydroponic water lines led to the accumulation of acesulfame, carbamazepine, and diclofenac in lettuce root systems at 32.0, 69.5, and 135 μg kg-1 and in the uptake of acesulfame and carbamazepine into lettuce shoots at 23.4 and 120 μg kg-1 dry weight, respectively. In contrast, both advanced treatment technologies when operating under optimized conditions achieved removal efficiencies of > 90% also for persistent micropollutants. Minimizing the pollution of reclaimed water thus met one relevant need for hydroponic lettuce cultivation.

Predicting the trend and utility of different photocatalysts for degradation of pharmaceutically active compounds: A special emphasis on photocatalytic materials, modifications, and performance comparison

The rapid rise in the healthcare sector has led to an increase in pharmaceutically active compounds (PhACs) in different aqueous bodies. The toxicity of the PhACs and their ability to persist after conventional treatment processes have escalated research in the field of photocatalytic treatment. Although different photocatalysts have been successful in degrading PhACs, their inherent drawbacks have severely limited their application on a large scale. A substantial amount of research has been aimed at overcoming the high cost of the photocatalytic material, low quantum yield, the formation of toxic end products, etc. Hence, to further research in this field, researchers must have a fair idea of the current trends in the application of different photocatalysts. In this article, the trends in the use of various photocatalysts for the removal of different PhACs have been circumscribed. The performance of different groups of photocatalysts to degrade PhACs from synthetic and real wastewater has been addressed. The drawbacks and advantages of these materials have been compared, and their future in the field of PhACs removal has been predicted using S-curve analysis. Zinc and titanium-based photocatalysts were efficient under UV irradiation, while bismuth and graphene-based materials exhibited exemplary performance in visible light. However, iron-based compounds were found to have the most promising future, which may be because of their magnetic properties, easy availability, low bandgap, etc. Different modification techniques, such as morphology modification, doping, heterojunction formation, etc., have also been discussed. This study may help researchers to clarify the current research status in the field of photocatalytic treatment of PhACs and provide valuable information for future research.

Occurrence, influencing factors, toxicity, regulations, and abatement approaches for disinfection by-products in chlorinated drinking water: A comprehensive review

Disinfection is considered as a vital step to ensure the supply of clean and safe drinking water. Various approaches are adopted for this purpose; however, chlorination is highly preferred all over the world. This method is opted owing to its several advantages. However, it leads to the formation of certain by-products. These chlorination disinfection by-products (DBPs) are genotoxic, carcinogenic and mutagenic. Still chlorination is being practiced worldwide. Present review gives insights into the occurrence, toxicity and factors affecting the formation of regulated (THMs, HAAs) and emerging DBPs (N-DBPs, HKs, HAs and aromatic DBPs) found in drinking water. Furthermore, remediation techniques used to control DBPs have also been summarized here. Key findings are: (i) concentration of regulated DBPs surpassed the permissible limit in most of the regions, (ii) high chlorine dose, high NOM, more reaction time (up to 3 h) and high temperature (up to 30 °C) enhance the formation of THMs and HAAs, (iii) high pH favors the formation of THMs while low pH is suitable of the formation of HAAs, (iv) high NOM, low temperature, low chlorine dose and moderate pH favors the formation of unstable DBPs (N-DBPs, HKs and HAs), (v) DBPs are toxic not only for humans but for aquatic fauna as well, (vi) membrane technologies, enhanced coagulation and AOPs remove NOM, (vii) adsorption, air stripping and other physical and chemical methods are post-formation approaches (viii) step-wise chlorination is assumed to be an efficient method to reduce DBPs formation without any treatment. Toxicity data revealed that N-DBPs are found to be more toxic than C-DBPs and aromatic DBPs than aliphatic DBPs. In majority of the studies, merely THMs and HAAs have been studied and USEPA has regulated just these two groups. Future studies should focus on emerging DBPs and provide information regarding their regulation.

Biodegradation pathway of penicillins by β-lactamase encapsulated in metal-organic frameworks

The pollution caused by the abuse of antibiotics has posed a serious threat to the ecological environment and human health, so development of effective strategies for degradation and disposal of antibiotic residues is urgently needed. In this work, penicillinase, a kind of β-lactamase, was immobilized into zeolitic imidazolate framework-8 (ZIF-8) by self-assembly method and the catalytic performance of the β-lactamase@ZIF-8 porous materials for degradation of penicillins has been investigated by high performance liquid chromatography coupled with mass spectrometry. The results illustrated that the catalytic activity of the encapsulated enzyme was significantly enhanced comparing with that of free enzyme. Meanwhile, the β-lactamase@ZIF-8 exhibited excellent stability under denaturing conditions including high temperature, organic solvent and the enzyme inhibitor. The catalytic degradation mechanism of the β-lactamase@ZIF-8 for penicillins has been probed and verified, and it has been found that the Zn (II) ion on ZIF-8 frameworks could form the complex with the target molecule, which weakened the bond of the four-membered β-lactam ring in the penicillin molecule, and thus enhanced the degradation efficiency of the enzyme. This work provided a promising strategy for eliminating the penicillin residues in water environment.

Structured photocatalytic systems: photocatalytic coatings on low-cost structures for treatment of water contaminated with micropollutants-a short review

The persistence of many micropollutants in water and wastewater is of great concern to the contemporary scientific community. Several types of advanced techniques such as heterogeneous photocatalysis are being used for the degradation of micropollutants in waters from domestic, industrial, and agricultural activities. Thus, structured photocatalytic systems are a great alternative in the development of photocatalytic reactors and continuous water treatment systems, as they present good autonomy during the treatment process. Many aspects such as type and geometry of the catalytic structure to be developed must be carefully chosen for the proper functioning of the system, as well as the best routes by which the photocatalysts will be immobilized. In this sense, this work brings the main photocatalytic coating techniques in low-cost structures for the treatment of water and wastewater contaminated with micropollutants. The methodologies and synthesis parameters that can influence the final result of the coating were highlighted, as well as the ability to reuse photocatalysts and methods for pretreating the structural surface. The dip-coating technique was the most reported among the current works due to its simplicity and, predominantly, the pretreatment techniques of the structure are still cleaning the surface with water, soap, and also some alcohols.

Review on UV/sulfite process for water and wastewater treatments in the presence or absence of O2

Based on previous reports, UV/sulfite process is generally used as an advanced reduction process (ARP) since e_aq^- and/or ∙H, both with strong reduction potential, could be substantially generated herein. Very recently, the combination of UV and sulfite as an advanced oxidation process (AOP) or an oxidation-reduction coupling process has attracted increasing interest due to the yield of SO₄^∙- and/or HO∙. Herein, the application of UV/sulfite as an ARP and AOP (or oxidation-reduction coupling process) during water and wastewater treatments is reviewed respectively. (1) In the absence of O₂, UV/sulfite works as an ARP. The generation mechanism of reactive reduction species and various contaminants removal (including degradation kinetics and efficiency, decomposition mechanisms, effects of some factors, etc.) is summarized in detail and systematically. Moreover, both the application of different types of UV lights and the economic evaluation are summarized systematically. (2) In the presence of O₂, UV/sulfite could be used as an AOP or oxidation-reduction coupling process. The generation mechanism of reactive oxidation species and influencing factors is also presented in detail. Moreover, two ways (including homogeneous and heterogeneous activation) used to enhance the UV/sulfite oxidation potential are summarized respectively. Moreover, several knowledge gaps and research needs for further research are proposed. Overall, this review provides an overview for in-depth understanding of UV/sulfite as an ARP or AOP (oxidation-reduction coupling process) during water and wastewater treatments.

Remediation of contaminated sediments containing both organic and inorganic chemicals using ultrasound and ozone nanobubbles

Most river sediments are contaminated with organic and inorganic pollutants and cause significant environmental damage and health risks. This research is evaluated an in-situ sediment remediation method using ultrasound and ozone nanobubbles to remove organic and inorganic chemicals in contaminated sediments. Contaminated sediment is prepared by mixing synthetic fine sediment with an organic (p-terphenyl) and an inorganic chemical (chromium). The prepared contaminated sediment is treated with ultrasound and ozone nanobubbles under different operating conditions. For the samples with the maximum initial concentration of 4211 mg/kg Cr and 1875 mg/kg p-terphenyl, average removal efficiencies are 71% and 60%, respectively, with 240 min of sonication with 2-min pulses, whereas 97.5% and 91.5% removal efficiencies are obtained for the same, respectively, as a single contaminant in the sediment. For the same maximum concentrations, the highest removal of p-terphenyl is 82.7% with 127.2 J/ml high energy density, and for Cr, it is 77.1% using the highest number of the treatment cycle and ozone usage with 78.75/ml energy density. The Cr highest removal efficiency of 87.2% is recorded with the reduced initial concentration of 1227 mg/kg with the highest treatment cycles. The Cr removal efficiency depends on the availability of oxidizing agents and the number of washing cycles of sediments, whereas P-terphenyl degradation is most likely influenced by the combined effects of oxidation and ultrasound-assisted pyrolysis and combustion of organics.

New frontiers and prospects of metal-organic frameworks for removal, determination, and sensing of pesticides

Pesticides have been widely used in agriculture to control, reduce, and kill insects. Humans are also being using pesticides to control insidious animals in daily life. By these practices, a huge volume of pesticides is introduced to the environment. Despite broad-spectrum applicability, pesticides also have hazardous effects on both humans and animals at high and low concentrations. Long-term exposure to pesticides can cause different diseases, like leukemia, lymphoma, and cancers of the brain, breasts, prostate, testis, and ovaries. Reproductive disorders from pesticides include birth defects, stillbirth, spontaneous abortion, sterility, and infertility. Therefore, the application of determination and treatment methods for pre-concentration and removal of these toxic materials from the environment appears a vital concern. To date, different materials and approaches have been employed for these purposes. Among these approaches, multifunctional metal-organic frameworks (MOFs)-assisted adsorption and determination processes have always been in the spotlight. These facts are due to exclusive properties of MOFs in terms of the crystallinity, large surface area, high chemical, and physical stability, and controllable structure as well as unique features of adsorption and determination process in terms of simple, easy, cheap, available method and ability to use in large and industrial scales. In the present work, we illustrate the exceptional features of MOFs as well as the possible mechanism for the adsorption of pesticides by MOFs. The use of these fantastic materials for pre-concentration and removal of pesticides are extensively explored. In addition, the performance of MOFs was compared with other adsorbents. Finally, the new frontiers and prospects of MOFs for the determination, sensing, and removal of pesticides are presented.

Anatoxin-a degradation by using titanium dioxide

Advanced oxidation processes, such as using titanium dioxide (TiO₂) photocatalysis, are being developed to reduce or eliminate the toxicity of treated water. In this study, the removal of purified anatoxin-a (ANTX-a), live Dolichospermum flos-aquae cells, and a cell extract of this organism under UV-A/TiO₂ photocatalysis, creation of decomposition products and their toxicity were investigated. Total degradation of purified ANTX-a from the initial concentration of 10 mg·L^-1 with the addition of TiO₂ under UV-A irradiation was achieved in 30 min. Under these conditions several decomposition products were noted with m/z ratio from 156.11 to 216.1. Analysis of the completely degraded ANTX-a sample using Thamnotoxkit F™ toxicity test showed that it was no longer toxic. TiO₂ photocatalysis was also efficient in the decomposition of the living cyanobacterial cells. Degradation of their cell structures and degradation of released toxin was also achieved in 30 min. Earlier homogenization of cyanobacteria culture significantly accelerated degradation of ANTX-a to 10 min.

Solar photo-Fenton treatment of the anti-cancer drug anastrozole in different aqueous matrices at near-neutral pH: Transformation products identification, pathways proposal, and in silico (Q)SAR risk assessment

Anastrozole (ANZ) is a breast cancer drug that was introduced onto the pharmaceutical market in the 1990s and is still one of the most widely consumed cytotoxic compounds. Due to the persistence of the drug, its continued presence after passing through wastewater treatment plants can lead to harm to aquatic environments. The present study investigates use of the solar photo-Fenton (SPF) process applied for ANZ degradation, considering the fate of ANZ and its transformation products (TPs). The SPF process was performed using different concentrations of ferrous iron (Fe²⁺) and H₂O₂ in solutions produced with deionized water (DW) and hospital wastewater (HWW), at pH close to neutrality. When solar irradiation in the SPF process was carried out the best ANZ removal rates were found under the following conditions: (i) for the DW matrix, [ANZ]₀ = 50 μg L^-1, [Fe²⁺] = 5 mg L^-1, and [H₂O₂]₀ = 25 mg L^-1, achieving 95% primary ANZ elimination; (ii) for the HWW matrix, [ANZ]₀ = 50 μg L^-1, [Fe²⁺] = 10 mg L^-1(multiple additions), and [H₂O₂]₀ = 25 mg L^-1, achieving 51% primary ANZ elimination. LC-QTOF MS analysis allowed to identify tentatively five transformation products (TPs) formed during the ANZ degradation process in DW, and two TPs when HWW was used. The main proposed degradation pathways were demethylation and hydroxylation. Different in silico models free available (quantitative) structure-activity relationship ((Q)SAR) software were used to predict the ecotoxicities and environmental fates of ANZ and the TPs. The in silico (Q)SAR predictions indicated that ANZ and the TPs were non-biodegradable compounds. In silico (Q)SAR predictions for mutagenicity and carcinogenicity end-points identified some TPs that require further study. Attention is drawn to the formation of several TPs for which statistical and rule-based positive alerts for mutagenic activities were found, requiring further confirmatory in vitro validation tests.

State-of-the-art and current challenges for TiO2/UV-LED photocatalytic degradation of emerging organic micropollutants

The development of ultraviolet light-emitting diodes (UV-LED) opens new possibilities for water treatment and photoreactor design. TiO₂ photocatalysis, a technology that has been continuously drawing attention, can potentially benefit from LEDs to become a sustainable alternative for the abatement of organic micropollutants (OMPs). Recently reported data on photocatalytic degradation of OMPs and their parameters of influence are here critically evaluated. The literature on OMP degradation in real water matrices, and at environmentally relevant concentrations, is largely missing, as well as the investigations of the impact of photoreactor design in pollutant degradation kinetics. The key factors for reducing UV-LED treatment technology costs are pointed out, like the increase in external quantum and wall-plug efficiencies of UV-LEDs compared to other technologies, as well as the need for an appropriate design optimizing light homogeneity in the reactor. Controlled periodic illumination, wavelength coupling and H₂O₂ addition are presented as efficiency enhancement options. Although electrical energy per order (E_EO) values for UV-LED photocatalysis have decreased to the range of traditional mercury lamps, values are still not low enough for practical employment. Moreover, due to the adoption of high initial OMP concentration in most experiments, it is likely that most literature E_EO values are overestimated. Given the process characteristics, which are favoured by translucent matrices and small diameters for more homogenous light distribution and better transportation of radicals, innovative reactor designs should explore the potential of point-of-use applications to increase photocatalysis applicability at large scale.

Processing methods and mechanisms for alkaloid-rich Chinese herbal medicines: A review

The processing of Chinese herbal medicine is a form of pharmaceutical technology developed over thousands of years, in order to increase efficiency and decrease toxicity of herbs in traditional Chinese medicine (TCM). Herbal processing is essential for safe and effective application of TCM in clinical practice, as it alters the active chemical components and therefore the functions of herbal medicines. Alkaloid-rich herbal medicines in TCM are commonly processed by cleansing, cutting, processing by dry stir-frying, stir-frying with liquid adjuvants, and processing by water decoction. In addition, commonly used adjuvants for processing alkaloid-rich herbal medicines are river sand, wine, vinegar, brine, honey and herbal juice. For alkaloid-rich herbal medicines, the main chemical reactions that occur during processing include hydrolysis, oxidation, replacement, decomposition and condensation. This paper aimed to summarize the processing methods and mechanisms for alkaloid-rich Chinese herbal medicines, and provide much-needed theoretical support and scientific evidence for understanding those mechanisms and effects. Information on processing methods for alkaloid-rich herbal medicines was collected from classic books of herbal medicine, PhD and MSc dissertations, online scientific databases including PubMed, SciFinder, Scopus, Web of Science, Baidu Scholar and Google Scholar. This paper should help to advance our knowledge of the processing mechanisms and aid in the development of processing methods for alkaloid-rich Chinese herbal medicines.

A critical review on advanced oxidation processes for the removal of trace organic contaminants: A voyage from individual to integrated processes

Advanced oxidation processes (AOPs), such as photolysis, photocatalysis, ozonation, Fenton process, anodic oxidation, sonolysis, and wet air oxidation, have been investigated extensively for the removal of a wide range of trace organic contaminants (TrOCs). A standalone AOP may not achieve complete removal of a broad group of TrOCs. When combined, AOPs produce more hydroxyl radicals, thus performing better degradation of the TrOCs. A number of studies have reported significant improvement in TrOC degradation efficiency by using a combination of AOPs. This review briefly discusses the individual AOPs and their limitations towards the degradation of TrOCs containing different functional groups. It also classifies integrated AOPs and comprehensively explains their effectiveness for the degradation of a wide range of TrOCs. Integrated AOPs are categorized as UV irradiation based AOPs, ozonation/Fenton process-based AOPs, and electrochemical AOPs. Under appropriate conditions, combined AOPs not only initiate degradation but may also lead to complete mineralization. Various factors can affect the efficiency of integrated processes including water chemistry, the molecular structure of TrCOs, and ions co-occurring in water. For example, the presence of organic ions (e.g., humic acid and fulvic acid) and inorganic ions (e.g., halide, carbonate, and nitrate ions) in water can have a significant impact. In general, these ions either convert to high redox potential radicals upon collision with other reactive species and increase the reaction rates, or may act as radical scavengers and decrease the process efficiency.

Disinfection by-products in drinking water: Occurrence, toxicity and abatement

Disinfection means the killing of pathogenic organisms (e.g. bacteria and its spores, viruses, protozoa and their cysts, worms, and larvae) present in water to make it potable for other domestic works. The substances used in the disinfection of water are known as disinfectants. At municipal level, chlorine (Cl₂), chloramines (NH₂Cl, NHCl₂), chlorine dioxide (ClO₂), ozone (O₃) and ultraviolet (UV) radiations, are the most commonly used disinfectants. Chlorination, because of its removal efficiency and cost effectiveness, has been widely used as method of disinfection of water. But, disinfection process may add several kinds of disinfection by-products (DBPs) (∼600-700 in numbers) in the treated water such as Trihalomethanes (THM), Haloacetic acids (HAA) etc. which are detrimental to the human beings in terms of cytotoxicity, mutagenicity, teratogenicity and carcinogenicity. In water, THMs and HAAs were observed in the range from 0.138 to 458 μg/L and 0.16-136 μg/L, respectively. Thus, several regulations have been specified by world authorities like WHO, USEPA and Bureau of Indian Standard to protect human health. Some techniques have also been developed to remove the DBPs as well as their precursors from the water. The popular techniques of DBPs removals are adsorption, advance oxidation process, coagulation, membrane based filtration, combined approaches etc. The efficiency of adsorption technique was found up to 90% for DBP removal from the water.

Bibliometric approach to the perspectives and challenges of membrane separation processes to remove emerging contaminants from water

The presence of contaminants in water is concerning due to the potential impacts on human health and the environment, and ingested contaminants cause harm in various ways. The conventional water treatment systems are not efficient to remove these contaminants. Therefore, novel techniques and materials for the removal of contaminants are increasingly being developed. The separation process using modified membranes can remove these micropollutants; therefore, they have attracted significant research attention. Among the materials used for manufacturing of these membranes, composites based on graphene oxide and reduced graphene oxide are preferred owing to their promising properties, such as mechanical resistance, thermal and chemical stability, antifouling capacity, water permeability, high thermal and electrical conductivity, high optical transmittance and high surface area. Membrane separation processes (MSP) can be used as secondary or tertiary treatment during the supply of wastewater. However, the efficient and accessible applications of these technologies are challenging. This study aims to demonstrate the main concepts of membrane separation processes and their application in the removal of emerging contaminants. This study reports bibliometric mapping, relevant data on studies using membranes as water treatment processes, and their viability in industrial applications. The main challenges and perspectives of these technologies are discussed in detail as well.

Efficient and stable catalysis of hollow Cu9S5 nanospheres in the Fenton-like degradation of organic dyes

The development of new heterogeneous catalysts with stable catalytic activity in a wide pH range to prevent polluting precipitation plays a vital role in large-scale wastewater treatment. Here, a facile anion exchange strategy was designed to fabricate hollow Cu₉S₅ nanospheres by using Cu₂O nanospheres as hard-templates. The structural and compositional transformation from Cu₂O nanospheres to hollow Cu₉S₅ nanospheres were investigated via X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The Fenton-like degradation of organic dyes was used to evaluate the catalytic performance of the obtained Cu-containing catalysts. Results reveal that the hollow Cu₉S₅ nanospheres have the best catalytic activity among five kinds of Cu-containing catalysts. Hollow Cu₉S₅ nanospheres can effectively accelerate the decomposition of H₂O₂ into hydroxyl radicals and superoxide radical, which have been proven to be mainly oxidative species in the Fenton-like degradation of organic pollutants. Hollow Cu₉S₅ nanospheres have a wide pH application range of 5.0-9.0, and their extremely stable activity can be maintained in at least 15 catalytic cycles with a Cu²⁺ ion leaching rate of less than 1.0 %. The outstanding catalytic performance of the Cu₉S₅ catalyst is expected to enhance the practical applications of copper sulfide catalysts in Fenton-like wastewater treatment.

Fe-Doped g-C3N4: High-Performance Photocatalysts in Rhodamine B Decomposition

Herein, Fe-doped C3N4 high-performance photocatalysts, synthesized by a facile and cost effective heat stirring method, were investigated systematically using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area measurement, X-ray photoelectron (XPS), UV-Vis diffusion reflectance (DRS) and photoluminescence (PL) spectroscopy. The results showed that Fe ions incorporated into a g-C3N4 nanosheet in both +3 and +2 oxidation states and in interstitial configuration. Absorption edge shifted slightly toward the red light along with an increase of absorbance in the wavelength range of 430-570 nm. Specific surface area increased with the incorporation of Fe into g-C3N4 lattice, reaching the highest value at the sample doped with 7 mol% Fe (FeCN7). A sharp decrease in PL intensity with increasing Fe content is an indirect evidence showing that electron-hole pair recombination rate decreased. Interestingly, Fe-doped g-C3N4 nanosheets present a superior photocatalytic activity compared to pure g-C3N4 in decomposing RhB solution. FeCN7 sample exhibits the highest photocatalytic efficiency, decomposing almost completely RhB 10 ppm solution after 30 min of xenon lamp illumination with a reaction rate approximately ten times greater than that of pure g-C3N4 nanosheet. This is in an agreement with the BET measurement and photoluminescence result which shows that FeCN7 possesses the largest specific surface area and low electron-hole recombination rate. The mechanism of photocatalytic enhancement is mainly explained through the charge transfer processes related to Fe2+/Fe3+ impurity in g-C3N4 crystal lattice.

Nanoparticles in Agroindustry: Applications, Toxicity, Challenges, and Trends

Nanotechnology is a tool that in the last decade has demonstrated multiple applications in several sectors, including agroindustry. There has been an advance in the development of nanoparticulated systems to be used as fertilizers, pesticides, herbicides, sensors, and quality stimulants, among other applications. The nanoencapsulation process not only protects the active ingredient but also can affect the diffusion, interaction, and activity. It is important to evaluate the negative aspects of the use of nanoparticles (NPs) in agriculture. Given the high impact of the nanoparticulated systems in the agro-industrial field, this review aims to address the effects of various nanomaterials on the morphology, metabolomics, and genetic modification of several crops.

Fe3O4/PVDF catalytic membrane treatment organic wastewater with simultaneously improved permeability, catalytic property and anti-fouling

Fe₃O₄/Polyvinylidene fluoride (PVDF) three-channel hollow fiber catalytic membrane was successfully fabricated via non-solvent induced phase inversion and used for organic wastewater degradation in this work. The effects of Fe₃O₄ nanoparticles addition on the surface and cross-section morphologies, hydrophilicity and thermal properties of the catalytic membrane were characterized by the field emission scanning electron microscopy (SEM), water contact angle and thermogravimetric analysis (TGA), respectively. The obtained catalytic membrane exhibited good hydrophilicity, a high pure water flux of 175.8 L m^-2 h^-1 and a high removal of methylene blue (up to 97.6%) with Fenton catalytic reaction. Meanwhile, the catalytic membrane shows excellent anti-fouling property due to the presence of Fenton reaction. Our results show that Fe₃O₄/PVDF three-channel hollow fiber catalytic membrane was a promising alternative for the degradation of organic contaminants.

Sonophotocatalytic disinfection of Shigella species under visible light irradiation: Insights into its molecular mechanism, antibacterial resistance and biofilm formation

Microbial contamination of water is one of the major sources of many diseases worldwide. Evolution of antibacterial resistance (ABR) alongside the caveats in most of the water treatment methods causes the severity of the current problem extremely vexing. This calls for an urgent need to develop new treatment methods aiming to reduce the microbial as well as ABR load in the environment. Herein, we successfully developed a visible light assisted sonophotocatalysis (SPC) using Fe/ZnO nanoparticles (NPs) for the disinfection of Shigella dysenteriae. A consortia containing S. dysenteriae and S. flexineri was also completely disinfected using SPC. Growth conditions of S. dysenteriae like growth phases and growth temperaturehad different outcomes on the overall efficacy of SPC. Compared with catalysts such as ZnO and TiO₂, Fe/ZnO resulted in better disinfection. Multi-ROS production, mostly containing h⁺ and O₂· radicals, due to the electron displacement in the catalyst and acoustic cavitation was identified as the factors behind bacterial lethality. The ROS produced was found to interfere with the metabolic activities of S. dysenteriae by causing membrane perturbation. We identified DNA damage inside the cells and the subsequent release of intracellular components. The compositional changes in the fatty acid makeup of the cells were altered as a result of SPC and few fatty acid markers indicating the stress posed by SPC were also identified. Loss of ABR in S. dysenteriae was also recorded post SPC treatment. Abatement in the biofilm forming ability of the injured bacterial cells was also recorded, proving the extremity of stress induced by SPC. Hence, the excellent efficacy of SPC in disinfecting bacteria is proposed for tertiary water treatment applications.

Ecotoxicity screening evaluation of selected pharmaceuticals and their transformation products towards various organisms

The intensive development of medical science has led to an increase in the availability and use of pharmaceutical products. However, nowadays, most of scientific attention has been paid to the native forms of pharmaceuticals, while the transformation products (TPs) of these substances, understood herein as metabolites, degradation products, and selected enantiomers, remain largely unexplored in terms of their characterization, presence, fate and effects within the natural environment. Therefore, the main aim of this study was to evaluate the toxicity of seven native compounds belonging to different therapeutic groups (non-steroidal anti-inflammatory drugs, opioid analgesics, beta-blockers, antibacterial and anti-epileptic drugs), along with the toxicity of their 13 most important TPs. For this purpose, an ecotoxicological test battery, consisting of five organisms of different biological organization was used. The obtained data shows that, in general, the toxicity of TPs to the tested organisms was similar or lower compared to their parent compounds. However, for example, significantly higher toxicity of the R form of ibuprofen to algae and duckweed, as well as a higher toxicity of the R form of naproxen to luminescent bacteria, was observed, proving that the risk associated with the presence of drug TPs in the environment should not be neglected.

The Effect of Electrolytes on the Photodegradation Kinetics of Caffeine

Unsuccessfully treated by the existing wastewater-treatment processes, caffeine concentrations in wastewater effluents and natural reservoirs are constantly rising. Photodegradation treatment processes are drawing much attention due to their potential to oxidize and remove such, and similar contaminating compounds from treated waters. In continuation to our previous work on the photodegradation kinetics of caffeine in water by UV/H2O2 and UV/TiO2, this work evaluates the influence of various electrolytes, including NaCl, KCl, MgCl2, NaBr, and KBr, on the kinetics of the UV/H2O2 photodegradation of caffeine, aiming at estimating the efficiency of the method in more complex water systems. Results show that the efficiency of the UV/H2O2 photodegradation reactions is strongly affected by ionic strength and the presence of electrolytes in the solution. While chloride electrolytes were shown to optimize or reduce the process efficiency pending on their concentration. The sole presence of NaBr and KBr shows an immediate reduction in the efficiency of the photodegradation. Empirical apparent-rate-coefficients and curves describing the effect of the different electrolytes on the photodegradation kinetics of caffeine are presented.

Advanced oxidative processes in the degradation of 17β-estradiol present on surface waters: kinetics, byproducts and ecotoxicity

Endocrine disruptors represent risks to aquatic ecosystem and humans, and are commonly detected in surface water. Photochemical treatments can be used to remove 17β-estradiol (E2), but few studies have analyzed the kinetics, intermediates, and 17β-estradiol degradation pathways in natural matrices. In this study, the photochemical behavior of E2 under ultraviolet irradiation (UVC, 254 nm) associated with oxidants (H₂O₂ or O₃) or photocatalyst (TiO₂) was investigated to evaluate the degradation potential and the transformation pathway in a natural surface water matrix. Additionally, computational modeling analyses with Ecological Structure Activity Relationships (ECOSAR) software were performed to predict the toxicity from the E2 and its transformation byproducts. E2 degradation kinetics showed adjusted to the pseudo-first-order kinetic model, being k_UV/O3 > k_UV/TiO2 > k_UV/H2O2 > k_UV. Eight transformation byproducts were identified by liquid chromatography with time-of-flight mass spectrometry (HPLC/TOF-MS) in natural surface water samples. These byproducts formed as the result of opening the aromatic ring and adding the hydroxyl radical. The E2 degradation pathway was proposed based on the byproducts identified in this study and in previous studies, suggesting the formation of aliphatic and hydroxylated byproducts. E2 treatment presented both very toxic and not harmful byproducts.

Synthesis of metallic copper modified g-C3N4 by molecular self-assembly structure and its combined catalytic performance with activated sludge

Copper modified carbon nitride (CuCN) was prepared by a hydrothermal self-assembly reaction and following high temperature thermal polymerization process. Finally, the sample exhibits uniform one-dimensional tubular structure. Interestingly, the separation efficiency of electron-hole pair is improved, and more catalytic active sites are exposed due to the special hollow structure. Meanwhile, the presence of copper element narrows its band gap, leading to the enhancement of photocatalytic degradation performance under simulated sunlight. In addition, the effect of CuCN on dehydrogenase activity of activated sludge was determined by TTC reduction method. After adding CuCN-2, the activity of activated sludge reached 0.134 μmol g^-1 min^-1, which indicated that the prepared CuCN-2 had good biocompatibility. It is suitable for both photocatalytic process and activated sludge treatment process. Therefore, the combination of photocatalytic technology and activated sludge process can further completely degrade organic pollutants. We found that CuCN could protect the survival and growth of microorganisms in activated sludge, so that the degradation efficiency of CuCN to nitrobenzene could reach 94.4 %. Therefore, CuCN has broad application prospects in photocatalytic-activated sludge combined treatment.

Coupled photocatalytic-bacterial degradation of pyrene: Removal enhancement and bacterial community responses

Polycyclic aromatic hydrocarbons (PAHs) are a class of pollutants that ubiquitously present in environment and hard to be degraded by microorganisms. Herein, we reported a novel photocatalytic-bacterial coupled removal system to treat PAH-polluted water. Using pyrene as the model pollutant, we demonstrated that the removal percentage of different groups was in order: 63.89% ± 1.03% (Vis-Biological) > 61.27% ± 1.08% (UV-Biological) > 59.58% ± 1.15% (UV) > 57.41% ± 1.13% (Vis) > 6.65% ± 0.72% (Biological) > 1.70% ± 0.34% (Control), showing the coupled system significantly improved the removal percentage of pyrene. Additionally, we observed that the coupled system driven by visible light showed higher removal percentage than UV light, exhibiting a good potential for future application. Sequencing analysis of 16S rRNA genes showed that alpha diversity (richness, evenness and diversity) got promoted and data of the relative abundance showed that Pseudomonadaceae was substituted as the dominant bacteria for Planococcaceae, with some other functional bacteria quickly acclimatizing in the bacterial community. Difference analysis indicated that over half of top fifteen genera were generally different significantly (p < 0.001) among two different samples, and UV light altered structure and composition of bacterial community more than visible light. Functional features' change suggested that the bacterial community not only protected itself but also participated in degrading pyrene. Overall, our study offered a new method for PAH degradation and contributed to further understanding of coupled catalytic-bacterial degradation processes.

Development and Validation of a LC-MS/MS Method for Determination of Multi-Class Antibiotic Residues in Aquaculture and River Waters, and Photocatalytic Degradation of Antibiotics by TiO2 Nanomaterials

This study presents a multi-residue method for simultaneous qualitative and quantitative analysis of eight antibiotics from some common classes, including beta-lactam, tetracyclines, lincosamides, glycopeptides, and sulfonamides in 39 aquaculture and river water samples from the Mekong Delta (Vietnam) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). As a result, doxycycline (DXC), oxytetracycline (OTC), lincomycin (LCM), sulfamethoxazole (SMX), and sulfamethazine (SMZ) were detected with high frequency over 65% and an average concentration of 22.6–76.8 ng·mL−1. The result suggests that antibiotic residues in the aquaculture and river waters are considered as an emerging environmental problem of the region. To address this issue, we fabricated the well-defined TiO2 nanotube arrays (TNAs) and nanowires on nanotube arrays (TNWs/TNAs) using the anodization method. The TNAs had an inner tube diameter of ~95 nm and a wall thickness of ~25 nm. Meanwhile, the TNWs/TNAs had a layer of TiO2 nanowires with a length of ~6 µm partially covering the TNAs. In addition, both TNAs and TNWs/TNAs had pure anatase phase TiO2 with (101) and (112) dominant preferred orientations. Moreover, the TNAs and TNWs/TNAs effectively and rapidly degraded the antibiotic residues under UV-VIS irradiation at 120 mW/cm2 and obtained over 95% removal at 20 min. Indeed, the photocatalytic reaction rate constants (k) were in the range of 0.14–0.36 min−1 for TNAs, and 0.15–0.38 min−1 for TNWs/TNAs. Noticeably, the k values of TNWs/TNAs were slightly higher than those of TNAs for LCM, DXC, OTC, SMZ, and SMX that could be attributed to the larger surface area of TNWs/TNAs than TNAs when TNWs/TNAs had an additional ~6μm TNWs top layer.

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

In this study, we report a surfactant-mediated synthesis of ferrites (MFe2O4: M = Co, Ni, Cu, Zn) using the co-precipitation-oxidation method. The band gap calculated from UV-Visible diffuse reflectance spectra were found in the range of 1.11-1.81 eV. These ferrite nanocatalysts were studied for the photocatalytic degradation of multiple organic dyes in a 32 W UV-C/H2O2 system. All the four ferrites showed an excellent dye degradation rate in the range of 2.065-2.417 min-1 at neutral pH. In the optimized condition, NiF was found to degrade 89%, 92%, 93%, and 78% of methylene blue, methyl orange, bromo green, and methyl red, respectively within 1 min of UV-irradiation. A 40% TOC removal was recorded after 5 min of degradation reaction, which increased to 60% after 50 min. Mechanism elucidated by scavenger studies and fluorescence spectroscopy revealed that •OH and holes were the primary reactive radicals responsible for the degradation process. Ferrite photocatalysts showed an insignificant performance loss in seven consecutive cycles. The photocatalyst was found efficient in the presence of a high concentration of salts. Thus, it was concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.

Selective adsorption and recovery of volatile fatty acids from fermented landfill leachate by activated carbon process

An adsorption-desorption process was applied on fermented landfill leachate to adsorb and recover acetic and butyric acid, using activated carbon. In this study, the first, volatile fatty acids adsorption process from fermented leachate was optimized, by investigating various affecting factors such as pH, time, agitation speed, activated carbon dosage, and temperature. The optimum condition for maximum adsorption of 88.94% acetic acid and 98.53% butyric acid, was 19.79 %wt activated carbon dosage, 40.00 rpm of agitation speed, in 9.45 °C and contact time of 179.89 h, while the pH of the substrate was kept fixed at pH:3.0. Results of X-ray fluorescence (XRF) spectrometry, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and zeta potential revealed that carbon is the dominant component in the adsorbent with a significant effect to remove organic impurities, and it was observed that the activated carbon after the adsorption process showed an amorphous structure peak with a large internal surface area and pore volume. The results exposed that the adsorption on the surface of activated carbon was due to the chemisorption, and the chemisorption mechanism was supported by covalent bonding. The kinetic study displayed excellent fit to Pseudo-second order kinetics model. The second phase of this study was to recover the adsorbed VFAs using multistage desorption unit, in which application of deionized water and ethanol (as desorption agents) resulted in 89.1% of acetic acid and 67.8% of the butyric acid recovery.

Advanced Oxidation Processes for the Removal of Antibiotics from Water. An Overview

In this work, the application of advanced oxidation processes (AOPs) for the removal of antibiotics from water has been reviewed. The present concern about water has been exposed, and the main problems derived from the presence of emerging pollutants have been analyzed. Photolysis processes, ozone-based AOPs including ozonation, O3/UV, O3/H2O2, and O3/H2O2/UV, hydrogen peroxide-based methods (i.e., H2O2/UV, Fenton, Fenton-like, hetero-Fenton, and photo-Fenton), heterogeneous photocatalysis (TiO2/UV and TiO2/H2O2/UV systems), and sonochemical and electrooxidative AOPs have been reviewed. The main challenges and prospects of AOPs, as well as some recommendations for the improvement of AOPs aimed at the removal of antibiotics from wastewaters, are pointed out.