Ultrapure Water Research Articles

Fiber laser irradiation in chemical solution for micro fabrication: Mechanisms and applications

The laser and electrochemical hybrid machining (LECM) could realize high-efficient and quality processing of difficult-to-cut materials and has become a research topic in microfabrication. However, it was difficult to ensure the stability and efficiency of laser transmission in chemical solutions, and an external voltage and auxiliary cathode should be added. In the present study, a novel fiber laser irradiation in chemical solution (LICS) has been proposed to process microstructures. The surface microstructures and chemical composition of the surfaces processed by LICS, laser irradiation in the ultrapure water, and electrochemical machining were compared. In LICS the materials were removed by laser processing and the following high-temperature gradient induced electrochemical dissolution. The high temperature gradient induced electrochemical dissolution could enhance the MRR and improve the surface quality. LICS can be regarded as a novel LECM process. The machining efficiency of LICS had been improved by 46.2 % compared with that laser irradiation in the ultrapure water, and the proportion of laser-induced electrochemical dissolution was 31.6 % in the LICS process. Further, the effects of laser power, chemical solution concentration, and optical fiber end movement control on the processing of micro grooves were explored, considering the dimension, MRR, and surface roughness. A front gap of smaller than 0.8 mm between the optical fiber end and workpiece was recommended during LICS. The repeated feeding of optical fiber was proposed to improve the depth-to-width ratio of the micro grooves fabricated by LICS. Finally, LICS was used to process microstructures with the controlled profiles on the nickel-based superalloy and titanium alloy workpieces without a recast layer, which holds great potential in surface microfabrication and texturing.

Strong enhancement on acetaminophen elimination and effective control of chlorinated/brominated by-products generation in heat/peroxymonosulfate system with sodium perborate

The application of heat/peroxymonosulfate (PMS) system was severely constrained due to the high O–O bond dissociation energy of PMS and the high risk of forming halogenated by-products. Interestingly, this work found that sodium perborate (NaBO3) could significantly improve the removal of acetaminophen in heat/PMS system. The proposed NaBO3/heat/PMS system could achieve 100 % elimination efficiency of ACT within 15 min and exhibited an excellent pseudo-first-order rate constant (kobs), which was 35.6-folds higher than heat/PMS system. 1O2 and OH were identified as the primary reactive species in NaBO3/heat/PMS system. NaBO3 can hydrolyze to produce BO2− and H2O2, where BO2− can subsequently hydrolyze to generate B(OH)4− having strong buffer capacity. The HOOB(OH)3/HOOBO, characterized by their asymmetric O–O bonds, can be formed through the reaction of PMS with BO2− and B(OH)4−. 1O2 mainly originated from the reactions of PMS with the formed HOOB(OH)3/HOOBO, and OH primarily originated from the cleavage of O–O bond in HOOB(OH)3/HOOBO and PMS. Three removal pathways of acetaminophen were proposed. The toxicity of acetaminophen solution was reduced following the treatment using NaBO3/heat/PMS system. Humic acid, CO32−, Br− and Cl− suppressed the acetaminophen removal in NaBO3/heat/PMS system, while initial pH, NO3− and SO42− had minimal impact. Notably, the kobs of acetaminophen removal in actual waters (e.g., groundwater and lake water) were greater than that in ultrapure water. More importantly, NaBO3/heat/PMS system can effectively control the formation of chlorinated/bromine by-products, which was achieved by converting HClO to inert B(OH)3OCl− with B(OH)4−, and reducing the HBrO and HClO to Br– and Cl– with deprotonated H2O2 (HO2−). This study proposed a promising approach for improving heat/PMS system and underscored its application potential in treating water containing Cl−and Br−.

Enhanced recovery of R-phycoerythrin using recombination cell-assisted pressurized fluid extraction: yield, characterization, and antioxidant evaluation

The recovery of phycobiliproteins, with an emphasis on R-phycoerythrin (R-PE), from Solieria filiformis macroalgae was investigated in the current study. This is accomplished using an environmentally friendly method known as pressurized fluid extraction. Phycobiliprotein production was analyzed over time, considering four different parameters: i) solvents (ultrapure water and phosphate buffer), ii) macroalgae particle sizes, iii) stirring, and iv) pressure of 200 to 800 bar. Notably, the highest R-PE yield reached an impressive 22.53 mg/g dry biomass. The best extraction conditions were identified as a macerated structure, employing a combination of 500 bar pressure and agitation facilitated by a recombination cell. R-phycocyanin (R-PC) was also extracted with a 3.70 mg/g yield. Two distinct extracts, crude and precipitate, underwent comprehensive characterization. Extracted R-PE exhibited an α-helix structure (80.51–90.39 %), suggesting the existence of other proteins in both extracts. Three different subunits, α (15 kDa), β (21 kDa), and γ (29 kDa), were segregated under SDS-PAGE. Moreover, both extracts demonstrated antioxidant capacity, achieving a 99.55 % reduction in 2,2-diphenyl-1-picryl-hydrazil (DPPH) radicals and a 13.94 % chelation of ferrous ions. This study reports the extraction of biomolecules using the recombination cell for the first time in the literature, proving an appealing alternative for non-aggressive extraction with inherent biological activity. These findings underscore the potential applications of these extracted phycobiliproteins in various fields, including biotechnology and health.

Photocatalytic degradation of methamidophos in water using zinc oxide as a photocatalyst

Conventional agriculture and the need to satisfy the demand for food, cause different types of pesticides to be used indiscriminately, causing them to be dispersed into ecosystems by wind and water currents, representing a serious environmental problem. For this reason, it is important to apply effective technologies for the elimination of pesticides from water bodies. In the present research, heterogeneous photocatalysis using ZnO as a photocatalyst was applied to evaluate the degradation of methamidophos in contaminated water prepared in ultrapure water and river water. Considering the working parameters of 3 g/L of zinc oxide, a concentration of 50 mg/L of methamidophos, with constant agitation of 300 rpm, temperature 25 ± 2 °C and a natural pH, methamidophos degradation percentages of 86.66 % and 57.96 % were achieved in ultrapure water and river water, respectively. The chloride, sulfates, nitrates, and nitrites anions present in the river water could be responsible for the decrease in the effectiveness of the photocatalytic process. The mathematical models that best describe the degradation process were the pseudo-second order model and the Elovich model.

Catalytic ozonation using spent battery-based (SB) catalysts for dyes, micropollutant removal and disinfection

This study aimed to explore the use of three different Spent battery-based (SB) catalysts of ozonation to remove organic contaminants and disinfection. The SB catalysts studied were prepared from three types of spent batteries' electrolytic pastes: Panasonic Super Hyper (SH), Panasonic Alkaline (AK) and yellow Rayovac (RV). Its characterization was made through FTIR, SEM, XRD, XRS and BET. The catalytic ozonation system was optimized through Central Composite Design (CCD) 22 with three replications at the central point, to determine the best catalyst dose and ozone dose (O3) to be applied. The degradation of 5 dyes and atrazine (ATZ) in ultrapure water (UW) and ATZ in secondary effluent (SE) and the disinfection was performed. The SB catalysts resulted in enhanced efficacy compared to ozonation alone. However, the AK showed better efficiency compared to the other catalysts in cleaner water matrices. When applied in SE the results showed equivalent efficiencies in comparison with single O3. The germination and elongation of Eruca sativa were not affected by the SB catalysts applied to O3, demonstrating that the effluent did not present toxicity either before or after the treatments. It highlights that the SB catalysts are capable of improving the organic pollutants removal.

Monte Carlo simulations of microdosimetry and radiolytic species production at long time post proton irradiation using GATE and Geant4-DNA.

Radiobiological effectiveness of radiation in cancer treatment can be studied at different scales (molecular till organ scale) and different time post irradiation. The production of free radicals and reactive oxygen species during water radiolysis is particularly relevant to understand the fundamental mechanisms playing a role in observed biological outcomes. The development and validation of Monte Carlo tools integrating the simulation of physical, physico-chemical and chemical stages after radiation is very important to maintain with experiments. Therefore, in this study, we propose to validate a new Geant4-DNA chemistry module through the simulation of water radiolysis and Fricke dosimetry experiments on a proton preclinical beam line. In this study, we used the GATE Monte Carlo simulation platform (version 9.3) to simulate a 67.5 MeV proton beam produced with the ARRONAX isochronous cyclotron (IBA Cyclone 70XP) at conventional dose rate (0.2Gy/s) to simulate the irradiation of ultra-pure liquid water samples and Fricke dosimeter. We compared the depth dose profile with measurements performed with a plane parallel Advanced PTW 34045 Markus ionization chamber. Then, a new Geant4-DNA chemistry application proposed from Geant4 version 11.2 has been used to assess the evolution of , , , , , , and reactive species along time until 1-h post-irradiation. In particular, the effect of oxygen and pH has been investigated through comparisons with experimental measurements of radiolytic yields for and Fe3+. GATE simulations reproduced, within 4%, the depth dose profile in liquid water. With Geant4-DNA, we were able to reproduce experimental radiolytic yields 1-h post-irradiation in aerated and deaerated conditions, showing the impact of small changes in oxygen concentrations on species evolution along time. For the Fricke dosimeter, simulated G(Fe3+) is 15.97±0.2 molecules/100eV which is 11% higher than the measured value (14.4±04 molecules/100 eV). These results aim to be consolidated by new comparisons involving other radiolytic species, such as or to further study the mechanisms underlying the FLASH effect observed at ultra-high dose rates (UHDR).

Photochemical fate of nonionic polyacrylamide induced by hydroxyl radicals in the natural water: Mineralization mechanism exploration and half-life time evaluation

Water-soluble polyacrylamide (PAM) compounds have been used extensively in various sectors. The abundance of PAM in the environment raises concerns about its environmental impact. However, the mineralization of PAM in water under natural light irradiation remains insufficiently explored. This study utilizes nonionic PAM (nPAM) as a representative model to investigate both the mechanism and efficiency of nPAM degradation in water when exposed to ultraviolet (UV) light with hydrogen peroxide (H2O2) as the hydroxyl radical source. In the dark or with only UVA irradiation, negligible mineralization of nPAM occurred. In contrast, the presence of hydroxyl radicals (produced by the UVA/H2O2 system) produced 50 % nPAM mineralization over 7 days under our experimental conditions. The corresponding molecular weight (MW) of the nPAM was swiftly reduced from 1.58 ×106 Da to 1.59 ×103 Da in 3 days. Moreover, five carboxylic acids and nitrate ions were identified as the photodegradation intermediates of nPAM. The efficiencies of nPAM photodegradation by the UVA/H2O2 system in different natural waters and environmental conditions were assessed. The rate constant for the reaction between the hydroxyl radical and nPAM was 2.17 ×109 M-unit−1 s−1. The half-lives of nPAM in the sea and continental surface waters were determined to be several years and dozens of days, respectively. The application of UVB obviously accelerated the mineralization of nPAM in ultrapure water (71 % degradation in 7 days). Moreover, mineralization of concentrated nPAM (200 mg/L) in sea water was more efficient when both UVA- and UVB-activated H2O2 were used. Additionally, toxic acrylamide was not generated during nPAM photodegradation. Moreover, the photodegradation intermediates from nPAM were found to be neither acutely nor chronically toxic to aquatic organisms. This comprehensive study sheds light on the photochemical fate of nPAM in natural waters and provides essential insight for practical treatment of PAM in water systems.

Antiviral and antibacterial efficacy of nanocomposite amorphous carbon films with copper nanoparticles

Copper compound-rich films and coatings are effective against widespread viruses and bacteria. Even though the killing mechanisms are still debated, it is agreed that the metal ion, nanoparticle release, and surface effects are of paramount importance to the antiviral and antibacterial efficacy of the surfaces. In this work we have investigated the behavior of the reactive magnetron sputtered nanocomposite diamond-like carbon thin films with copper nanoparticles (DLC:Cu). The films were etched employing oxygen plasma and/or exposed to ultra-pure water, aiming to investigate the differences of the Cu release in the medium and changes in film morphology. The presence of metallic copper and Cu2O phases was confirmed by multiple analytical methods. Pristine films were more effective in the Cu release reaching up to 1.3 mg/L/cm2 concentration. Plasma processing resulted in the oxidation of the films which released less Cu, but after exposure to water, their average roughness increased more, up to 5.5 nm. Pristine and O2 plasma processed DLC:Cu films were effective against both model coronavirus and herpesvirus after 1-hour contact time and reached virus reductions of up to 2.23 and 1.63 log10, respectively. Pristine DLC:Cu films were more effective than plasma-processed ones against herpesvirus, while less expressed difference was found for coronavirus. The virucidal efficacy over up to 24 h exposures in the aqueous medium was validated. A bactericidal study confirmed that pristine DLC:Cu films were effective against gram-negative E. coli and gram-positive E. faecalis bacteria. After 3 h, 100 % antibacterial efficiency (ABE) was obtained for E. coli and 99.97 % for E. faecalis. After 8 h and longer exposures, 100 % ABE was reached. The half-life inactivation of viruses was 8.10–11.08 min and for E. faecalis 15.1–72.2 min.

Photodegradation of bisphenol A (BPA) in coastal aquaculture waters: Influencing factors, products, and pathways

Bisphenol A (BPA), an endocrine-disrupting contaminant, is ubiquitous in the environment due to its presence in plastics, wastewater, and agricultural runoff. This study investigated the photodegradation behavior of BPA in coastal aquaculture waters near Qingdao, China. Lower salinity promoted BPA photodegradation, while higher salinity has an inhibitory effect, suggesting slower degradation in seawater compared to ultrapure water. Triplet-excited dissolved organic matter (3DOM*) was identified as the primary mediator of BPA degradation, with additional contributions from hydroxyl radicals (•OH), singlet oxygen (1O2), and halogen radicals (HRS). Alepocephalidae aquaculture water exhibited the fastest degradation rate, likely due to its high DOM and nitrate/nitrite (NO3−/NO2−) content, which are sources of 3DOM* and •OH. A positive correlation existed between NO3−/NO2− concentration and the BPA degradation rate. Ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) analysis identified the primary BPA photodegradation products, formed mainly through oxidative degradation, hydroxyl substitution, nitration, and chlorination pathways. Elucidating these photodegradation mechanisms provides valuable insights into the environmental fate and potential ecological risks of BPA in aquaculture environments. This knowledge can inform strategies for marine environmental protection and the development of sustainable practices.

Exploring the role of hydrogen peroxide dosage strategies in the photo-Fenton process: Scaling from lab-scale to pilot plant solar reactor

This study aims to investigate the role of hydrogen peroxide (HP) continuous dosage in removing Paracetamol (PCT) from different water matrices using the solar photo-Fenton process. Different parameters in the HP dosage strategies (initial HP pulse, dosing time, and HP concentration) were systematically analysed to assess their impacts on pollutant removal (XPCT), oxidant specific consumption (YHP/PCTt), and toxicity levels (I(%)). The analysis involved various water matrices (ultrapure water UW, groundwater GW, anion matrix AW, and synthetic pharmaceutical wastewater IW0.01 or IW0.1), which were firstly treated in a laboratory reactor and subsequently scaled up to a solar prototype. After laboratory testing, the most effective reaction configuration (maximum XPCT and YHP/PCTt close to the stoichiometric one) was chosen as the starting point for scaling up the reaction system. Using the solar reactor setup, complete PCT conversion was achieved within just 60 min of reaction time (UW matrix). However, under IW0.1 condition and employing the same HP dosing strategy, a XPCT of 95.4 % was attained but at 180 min of reaction, highlighting the significant influence of the real matrix. Additionally, the I(%) remained high towards the end of the reaction (close to 60 %), attributed to the presence of hydroquinone in the system, demanding longer reaction times to completely reduce the toxicity when working with industrial wastewater. This comprehensive approach aims to close the gap between lab results and practical applications, offering crucial insights to address pharmaceutical wastewater pollution.

Validation of a bioanalytical HPLC-UV method to quantify Α-Bisabolol in rat plasma applied to pharmacokinetic pilot study with the drug nanoemulsion.

α-Bisabolol (α-BIS) is a sesquiterpene alcohol present in chamomile essential oil [Chamomilla recutita (L.) Rauschert]. Despite its numerous pharmacological effects, its pharmacokinetics remain understudied. An analytical method capable of quantifying α-BIS in plasma is crucial to enable pharmacokinetic analysis. Presently, only one study has quantified it using mass spectrometry. Administering α-BIS requires a nanoemulsion for intravenous injection. This study aimed to develop and validate a bioanalytical method using high-performance liquid chromatography with an ultraviolet detector to quantify α-BIS in rat plasma. The method employed acetonitrile and ultrapure water (80:20, v/v) as the mobile phase, with a flow rate of 1ml/min and concentrations ranging from 465 to 29.625 μg/ml. All US Food and Drug Administration-designated assays were successful, indicating the method's precision, accuracy, sensitivity and linearity in determining α-BIS in rat plasma. The developed nanoemulsion, assessed through dynamic light scattering analysis, the ensemble collection of particles and polydispersity index evaluation, proved safe and effective for intravenous administration. The pharmacokinetic parameters such as volume of distribution, clearance and half-life indicated that α-BIS tends to persist in the body. This study provides a foundation for further research to explore α-BIS's potential pharmaceutical applications in the future.

Efficient organic contaminant degradation by visible-light-driven Z-scheme g-C3N4/Bi2S3 heterojunction under the experimental and natural environment

In this study, a series of Z-scheme g-C3N4/Bi2S3-X (CN/Bi2S3-X) photocatalysts with different ratios were prepared by a simple hydrothermal method for degradation of MB. The decomposition rate of MB reached 96.12 % over CN/Bi2S3–20 % under 60 min of visible light irradiation, which was 2.05 and 2.02 times higher than that of pure Bi2S3 and g-C3N4, respectively. In addition, CN/Bi2S3–20 % can effectively degrade MB over a wide pH range (3–11) and a low catalyst dosage (10 mg). And CN/Bi2S3–20 % demonstrated a high degradation efficiency of MB in various real water bodies, including rainwater, ultrapure water, tap water, lake water, and industrial wastewater, with a rate of up to 90 %. Furthermore, CN/Bi2S3–20 % has a certain universality and a practical application prospect, which effectively degraded various contaminants, such as RhB (57.8 %), TC (56.7 %), NOR (62.1 %) and MG (70.8 %). The analysis of active species, EPR and well-matched band positions showed that the electron transfer mechanism is consistent with the Z-scheme heterojunction, which could well retain the strong redox ability. Moreover, a possible degradation pathway for MB was deduced according to the HPLC-MS results. This study provides a handy approach to constructing g-C3N4-based Z-scheme photocatalysts for the efficient degradation of pollutants.

Effect of Ion-Exchanger Monoporosity in the Kinetics of Oxygen Sorption by Silver-Containing Nanocomposites

The results of a study of the kinetics of oxygen sorption from water by silver-containing nanocomposites synthesized on the base of macroporous ion exchangers with different pore sizes are presented. In the case of the Lewatit K 2620 ion exchanger, the pore size was fixed (41 nm), and for KU-23, it varied in the range from 10 to 100 nm. The nanocomposite materials Ag0⸱KU-23 and Ag0⸱Lewatit K 2620 were prepared by chemical precipitation. Using the different physicochemical methods, it was found that due to the monoporosity of the ion exchanger, the average size of the silver particles in the Ag0⸱Lewatit K 2620 nanocomposite is smaller than for KU-23. This effect contributes to the intensification of oxygen absorption and is proved by the results of studying the rate and degree of oxygen sorption by nanocomposites in the entire studied range of their capacity on metal. On the other hand, the polyporosity of the KU-23 ion exchanger, due to its better diffusion permeability, contributes to the more uniform distribution of silver over the volume of nanocomposite grains and ensures the steady state of the sorption process. Based on the presented experimental results, the synthesized silver-containing nanocomposites can be recommended as multifunctional materials with bactericidal action and catalytic effect for different industrial applications, including the deep removal of dissolved oxygen in the production of ultrapure water for energetics and microelectronics.

A study on an analytical method for volatile fatty acids (VFAs) in the atmosphere by using ion chromatography and ultrapure water

A study on an analytical method for volatile fatty acids (VFAs) in the atmosphere by using ion chromatography and ultrapure water

Removal of Micropollutants in Water Reclamation by Membrane Filtration: Impact of Pretreatments and Adsorption.

Organic micropollutants (OMPs) present in water and wastewater are in the spotlight because of their potentially harmful effects even at low concentrations and the difficulties of their elimination in urban wastewater treatment plants (UWWTPs). This study explores the impact of some membrane filtration processes on the removal of a group of 11 OMPs with an eye on the effects of two pretreatments (i.e., coagulation and adsorption onto powdered activated carbon (PAC)) and the adsorption of OMPs onto the membranes on the overall removal. For this purpose, ultrafiltration (UF) and nanofiltration (NF) experiments were conducted with selected OMPs spiked in ultrapure water and secondary effluents from UWWTPs. It was observed that the adsorption of OMPs onto the membranes was influenced by the characteristics of the membranes, as well as the presence of effluent organic matter (EfOM). Since adsorption was the dominant mechanism for the rejection of OMPs by UF membranes, a study of the adsorption equilibrium of the micropollutants using UF membrane pieces as the adsorbent was conducted. The adsorption isotherms for the most hydrophobic OMPs fitted the Langmuir model. The efficiency of coagulation and powdered activated carbon (PAC) adsorption coupled with UF were also investigated. Both pretreatments alleviated membrane fouling and improved the rejection of organic and inorganic matter. The PAC pretreatment significantly improved the removal of OMPs in the combined PAC/UF process. The best options for achieving reclaimed water with satisfactory physicochemical quality, nearly devoid of OMPs and microorganisms, and suitable for diverse reuse purposes are either the NF treatment or the combination of PAC/UF.

Corrosion phenomena and deposits in ITER Neutral Beam Test Facility primary cooling circuits

The ITER Neutral Beam Test Facility (NBTF) is hosted in Padua and includes two experiments: MITICA, the 1 MeV full-scale prototype of the ITER HNB injector, and SPIDER, the 100 keV full-size ITER Radio Frequency (RF) negative ion source. SPIDER and MITICA experiments are actively cooled by Ultrapure Water (UPW) to electrically insulate in-vessel components that are biased to high voltage levels. Water conductivity is an important monitored parameter to ensure components' insulation by limiting the leakage current of active cooled equipment. A very low conductivity water is especially important in MITICA, where components need to operate up to 1 MVdc, an insulation level beyond the actual industrial standard. Careful selection of suitable materials for any in-vessel (vacuum insulation) and out-vessel component (air insulation) is of utmost importance, as their interaction with water and different environment may affect their chemical and mechanical properties. Additionally, materials selection can severely influence water chemical characteristics: cooling circuits are made of metals (copper, aluminium, steel) and insulating materials (plastic, rubber) when connecting parts at different electric potentials.During the first years of cooling plant exploitation, it was shown that water degrades more quickly than estimated by design. The Primary Circuits (PCs) that showed the most severe water degradation during operation are SPIDER and MITICA power supply ones, respectively called PC01 and PC08. This paper describes the results of specific experimental tests performed on MITICA PC08 to evaluate possible causes of water degradation and detect sources of contaminants that might compromise future experimental campaigns. The cooling circuit was subdivided in different sections and water circulation tests were performed at constant temperature and flowrate. Water samples were collected and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses were performed to quantify the type and amount of metals released. Moreover, components samples collected along their cooling circuits were characterized by Scanning Electron Microscope (SEM) technique to detect undesired contaminants and immersed in UPW to study their corrosion behaviour using metal release tests.

Laser‐Induced Nucleation of Acetaminophen through the Addition of Insoluble Impurities and Acidic Polymers

AbstractThis study investigates the crystallization of acetaminophen (ACET) in ultrapure water and a 10 wt.% aqueous polyacrylic acid (PAA) solution using non‐photochemical laser‐induced nucleation (NPLIN) for the first time. Using a 532 nm nanosecond laser, two distinct crystal morphologies—rhombic and tetragonal plate‐like—are formed in both solvents after adding impurities. Notably, the PAA solution showed a reduced number of crystals and slower growth rates compared to ultrapure water, suggesting that the acidic polymer modulates crystal growth. Interestingly, crystals are not induced by the laser without impurities. However, impurities like copper phthalocyanine (CuPc) or boron carbide (CB4) enabled successful NPLIN, with CB4 showing higher nucleation efficiency than CuPc. The study also explores how laser power affects nucleation probability and identifies potential laser energy thresholds. Experimental data on ACET crystal sizes over time are fitted to derived equations, which accurately represented trends and predicted results. The nanoparticle heating mechanism and the role of acidic polymers in affecting nucleation probability and growth rate are discussed, along with potential mechanisms for changes in crystal morphology.

The colloidal stability of molybdenum disulfide nanosheets in different natural surface waters: Combined effects of water chemistry and light irradiation

With the increasing production and application, more molybdenum disulfide (MoS2) nanosheets could be released into environment. The aggregation and dispersion of MoS2 nanosheets profoundly impact their transport and transformation in the aquatic environment. However, the colloidal stability of MoS2 remains largely unknown in natural surface waters. This study investigated the colloidal stability of MoS2 nanosheets in six natural surface waters affected by both light irradiation and water chemistry. Compared to that of the pristine MoS2 nanosheets, the colloidal stability of MoS2 photoaged in ultrapure water declined. Light irradiation induced the formation of Mo-O bonds, the release of SO42− species, and the decrease in 1T/2H ratio, which reduced negative charge and enhanced hydrophobicity. However, the colloidal stability of MoS2 photoaged in natural surface waters was increased relative to that in ultrapure water not only for the smaller extent of photochemical transformation but more importantly the surface modification by water chemistry. Furthermore, the colloidal stability of MoS2 photoaged in natural surface waters followed the order of sea water > lake water > river water. The abundant cations (e.g., Ca2+ and Mg2+) in sea water facilitated the covalent grafting (S-C bonds) of more dissolved organic matter (DOM) on MoS2 via charge screening and cation bridging, thus inducing stronger electrostatic repulsion and steric effect to stabilize nanosheets. The crucial role of the covalent grafting of DOM was further confirmed by the positive correlation between the critical coagulation concentration values and S-C ratios (R2 = 0.82, p < 0.05). Our results highlighted the dominant role of water chemistry than light irradiation in dictating the colloidal stability of MoS2 photoaged in natural surface waters, which provided new insight into the environmental behavior of MoS2 in aquatic environment.

"Core/Shell" Nanocomposites as Photocatalysts for the Degradation of the Water Pollutants Malachite Green and Rhodamine B.

"Core/shell" composites are based on a ferrite core coated by two layers with different properties, one of them is an isolator, SiO2, and the other is a semiconductor, TiO2. These composites are attracting interest because of their structure, photocatalytic activity, and magnetic properties. Nanocomposites of the "core/shell" МFe2O4/SiO2/TiO2 (М = Zn(II), Co(II)) type are synthesized with a core of MFe2O4 produced by two different methods, namely the sol-gel method (SG) using propylene oxide as a gelling agent and the hydrothermal method (HT). SiO2 and TiO2 layer coating is performed by means of tetraethylorthosilicate, TEOS, Ti(IV) tetrabutoxide, and Ti(OBu)4, respectively. A combination of different experimental techniques is required to prove the structure and phase composition, such as XRD, UV-Vis, TEM with EDS, photoluminescence, and XPS. By Rietveld analysis of the XRD data unit cell parameters, the crystallite size and weight fraction of the polymorphs anatase and rutile of the shell TiO2 and of the ferrite core are determined. The magnetic properties of the samples, and their activity for the photodegradation of the synthetic industrial dyes Malachite Green and Rhodamine B are measured in model water solutions under UV light irradiation and simulated solar irradiation. The influence of the water matrix on the photocatalytic activity is determined using artificial seawater in addition to ultrapure water. The rate constants of the photocatalytic process are obtained along with the reaction mechanism, established using radical scavengers where the role of the radicals is elucidated.

Removal of Bisphenol S (BPS) by Adsorption on Activated Carbons Commercialized in Brazil.

This study assessed three powdered activated carbons (BETM, COCO, and SIAL) commercialized in Brazil at the bench scale in agitated reactors, analyzing their kinetic behavior and adsorptive capacity for BPS and BPA in ultrapure water. BETM exhibited the highest adsorption capacities (Q0max) for BPS and BPA at 260.62 and 264.64 mg/g, respectively, followed by SIAL, with a Q0max of 248.25 mg/g for BPS and for 231.20 mg/g BPA, and COCO, with a Q0max of 136.51 mg/g for BPS and 150.03 mg/g for BPA. The Langmuir isotherm model can describe the processes well. A pseudo-second-order model can describe the adsorption kinetics, and SIAL carbon had the highest rate constants (7.45 × 10-3 mg/g/min for BPS and 2.84 × 10-3 mg/g/min for BPA). The Weber-Morris intraparticle diffusion model suggests intraparticle diffusion as the rate-limiting step of all adsorption processes. Boyd's model confirmed more than the mechanism actuating in the bisphenol adsorption. The results suggest that adsorbents with basic surfaces, high specific surface areas, and high mesopore volumes tend to remove BPS and BPA efficiently. Therefore, activated carbons can effectively complement the existing treatment in Brazilian water treatment plants (WTPs).