Effects Of Water Matrices Research Articles

Improved ultrafiltration performance through dielectric barrier discharge/sulfite pretreatment: Effects of water matrices and mechanistic insights

The feasibility of utilizing a dielectric barrier discharge (DBD)/sulfite-ultrafiltration system was investigated in various real water bodies, aiming to clarify the mechanism behind alleviating membrane fouling while synchronously degrading perfluorooctanoic acid (PFOA) during the treatment process of Yangtze River water. The results demonstrated that the DBD/sulfite pretreatment exhibited remarkable rates of membrane flux mitigation (>84.10%) and efficient degradation rates of PFOA (>85.13%), which decreased with increasing pH from 3.0 to 11.0. The presence of anions, cations, and natural organic matter slightly hindered the membrane fouling mitigation and PFOA degradation by quenching free radicals; however, the addition of SO42− had a negligible impact. The mitigation of membrane fouling was attributed to the significant involvement of various radicals, including hydroxyl radical (•OH), sulfate radical (SO4•−), electron (e−/eaq−), su-peroxide anion radicals (•O2−), and other radicals such as SO3•−, exhibiting respective contributions of 33.25%, 28.49%, 20.56%, 11.32%, and 6.39% in a synergistic redox effect. The pretreatment effectively reduced standard blocking and cake filtration fouling mechanisms by creating a sparse fouling layer on the membrane surface while increasing its roughness. Additionally, the main active species that played a significant role in the degradation of PFOA were identified as SO4•−, •OH, and eaq−. These species contributed approximately 43.63%, 24.39%, and 20.65% respectively to the degradation process. By employing mass spectrometry and density functional theory, a proposed pathway for PFOA degradation was established, effectively reducing the toxicity associated with its degradation byproducts. This study provides innovative insights into membrane-based water treatment technologies that effectively tackle both membrane fouling mitigation and PFOA degradation.

Effects of water matrices on the removal of oxytetracycline antibiotic and total organic carbon (TOC) using four different oxidation processes

Antibiotic compounds are actively discharged into aquatic environments through wastewater, potentially contributing to the emergence of drug-resistant bacteria and associated health issues. Oxidation processes (OPs), including advanced oxidation processes (AOPs), have gained attention as promising methods for removing antibiotics from wastewater. In this study, we comprehensively compared the efficiencies of removing oxytetracycline (OTC) and total organic carbon (TOC) by four OPs. These processes include three AOPs: the ozone/hydrogen peroxide process (O3/H2O2), photo-Fenton reaction (Fe/H2O2/UV), and Fenton reaction (Fe/H2O2), and ozonation (O3) as a conventional OP. To evaluate the effects of different water matrices, the degradation experiments were conducted using ultrapure water and actual wastewater. All four OPs achieved over 99% OTC degradation within 15 minutes of the experiment. The photo-Fenton reaction exhibited the highest TOC removal rates (66% for ultrapure water and 74% for actual wastewater) after 210 minutes. Conversely, ozonation resulted in the lowest TOC removal rates (7% for ultrapure water and 10% for actual wastewater). Therefore, this study suggests that the photo-Fenton reaction may be most suitable for degrading OTC and removing TOC from wastewater.

Insights on the degradation mechanism of neotame using UV/periodate: Roles of reactive species, kinetics, and pathways

As a new artificial sweetener (ASs), the jeopardize of neotame (NEO) to aquatic environment is attracting concern due to its widespread usage and difficulty in removing from wastewater. UV/periodate (UV/PI) is being considered as an effective process for the degradation of micropollutants in wastewater. However, there are few studies of the roles of reactive species (RS) and the effects of complex water matrices on the degradation of NEO via UV/PI. The degradation of NEO in aqueous media by UV/PI was investigated herein. NEO was effectively removed (>97 %) by UV/PI within 4 min. The degradation of NEO was mainly attributed to •OH (75.7 %), IO3• (23.0 %) and 1O2 (1.3 %) with the observed second-order rate constants of 7.71 × 109, 1.56 × 108 and 2.94 × 105 M−1 s−1, respectively. The contribution of IO3• and 1O2 to NEO degradation was greater at acidic and high PI concentrations, but significantly decreased in the presence of natural organic matter. The presence of anions in the water did not obviously impact NEO degradation. During the degradation of NEO, •OH attacked NEO through hydroxylation reaction, while IO3• and 1O2 predominantly participated in decarboxylation and amide hydrolysis reactions. Toxicity evaluation showed that the UV/PI treatment of NEO enhanced the toxicity to Vibrio fischeri within 5 min, and the toxicity reduced with the prolongation of treatment time. The study provides meaningful information on the roles of IO3• and 1O2 for NEO degradation by UV/PI.

Enhanced degradation of acid orange 74 via anodic activation of peroxydisulfate using a silver nanoparticle-modified carbon paper anode

In this study, peroxydisulfate (PDS) was activated using silver nanoparticle-modified carbon paper (AgNPs@CP) anode for the efficient degradation of acid orange 74 (AO 74) in wastewater. The AgNPs@CP anode degraded AO 74 at a 4.96-fold higher rate than the unmodified CP anode, where the degradation efficiency depended mainly on radical oxidation, with ·OH accounting for 63.50% and SO4·− accounting for 16.02%. The current density and PDS concentration were the most important parameters affecting the activation efficiency, and the degradation rate could be quantitatively controlled by adjusting these parameters. In terms of the effect of water matrices, Cl− considerably improved the electrochemical activation efficiency, whereas CO32− and PO43− inhibited it. After five cycles of reuse, the AO 74 degradation efficiency decreased to 88.39%, and the corresponding degradation rate decreased to 30.56% of the original value. However, the AO 74 degradation efficiency was still substantially higher than that achieved by the unmodified CP anode. The main reason for the deactivation of the AgNPs@CP electrode was the formation of Ag2+ during electrochemical activation. Generally, the anodic activation of PDS using the AgNPs@CP anode is an efficient method for degrading refractory organic pollutants.

Effect of dissolved organic matter on bacterial regrowth and response after ultraviolet disinfection

The effect of dissolved organic matter (DOM) on bacterial regrowth in water after disinfection using ultraviolet (UV) light emitting diodes (UVLEDs) is still unclear. Herein, the regrowth and responses of Vibrio parahaemolyticus and Bacillus cereus were investigated after being exposed to UVLEDs at combined wavelengths (265 and 280 nm) in a phosphate-buffered saline consisting of Suwannee River natural organic matter (SRNOM) and Suwannee River fulvic acid (SRFA). Low-molecular-weight (MW) organic compounds, which may form into intermediary photoproducts, and indicate bacterial repair metabolism, were characterized through non-target screening using orbitrap mass spectrometry. This study demonstrates the ability of the UVLEDs-inactivated cells to regrow. After UV exposure, a considerable upregulation of RecA was observed in two strains. With increasing the incubation time, the expression levels of RecA in V. parahaemolyticus increased, which may be attributed to the dark repair mechanism. Coexisting anionic DOM affects both the disinfection and bacterial regrowth processes. The time required for bacterial regrowth after UV exposure reflects the time needed for the individual cells to reactivate, and it differs in the presence or absence of DOM. In the presence of DOM, the cells were less damaged and required less time to grow. The UVLEDs exposure results in the occurrence of low-MW organic compounds, including carnitine or acryl-carnitine with N-acetylmuramic acid, which are associated with bacterial repair metabolism. Overall, the results of this study expand the understanding of the effects of water matrices on bacterial health risks. This can aid in the development of more effective strategies for water disinfection.

Synergistic effects of photocatalysis-periodate activation system for the degradation of emerging pollutants using GO/MgO nanohybrid

The combination between periodate (PI) activation and photocatalysis processes using heterogeneous catalysts can overcome the slow degradation rates related to photocatalysis and accelerate the degradation of organic pollutants. Thus, a nanohybrid of graphene oxide (GO) and magnesium oxide (MgO) (GO/MgO) was fabricated, characterized, and employed as a photocatalyst and an activator of PI for the degradation of reactive blue-222 (RB-222) dye, sulfamethazine (Sulfonamide antibacterial), and atrazine (Herbicide). Further, the optimization of operating parameters, the stability of the composite, the degradation mechanism, and the effects of water matrices were investigated. The bandgap decreased to 2.6 eV after merging between the GO and MgO, and the separation between charge carriers was improved in the case of the nanohybrid compared to single GO and MgO. The highest degradation percentage of RB-222 dye was achieved under the optimal operating conditions (pH 7, dye concentration of 6.4 mg/L, PI concentration of 1.5 mM, and catalyst dosage of 0.3 g/L) in the presence of light within 120 min. The nanocomposite was reused for five succeeding runs, where the degradation ratios decreased from 97.3% in the first run to 88% in the third run and declined to 81.25% in the fifth run which affirmed the high stability of the catalyst under three succeeding cycles. The degradation mechanism was explored showing that iodate radicals were the main reactive species. The degradation percentages of RB-222 decreased to 85.1% and 67.6% in the case of canal and sea water matrices, respectively. The degradation efficiencies of sulfamethazine and atrazine were 87.5% and 85%, respectively under the optimal conditions. The prepared composite exhibited high degradation performance towards different pollutants which affirmed the applicability of the proposed degradation system for degrading real industrial effluents.

Evaluation of commercial nanofiltration and reverse osmosis membrane filtration to remove per-and polyfluoroalkyl substances (PFAS): Effects of transmembrane pressures and water matrices.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are now widely found in aquatic ecosystems, including sources of drinking water and portable water, due to their increasing prevalence. Among different PFAS treatment or separation technologies, nanofiltration (NF) and reverse osmosis (RO) both yield high rejection efficiencies (>95%) of diverse PFAS in water; however, both technologies are affected by many intrinsic and extrinsic factors. This study evaluated the rejection of PFAS of different carbon chain length (e.g., PFOA and PFBA) by two commercial RO and NF membranes under different operational conditions (e.g., applied pressure and initial PFAS concentration) and feed solution matrixes, such as pH (4-10), salinity (0- to 1000-mM NaCl), and organic matters (0-10mM). We further performed principal component analysis (PCA) to demonstrate the interrelationships of molecular weight (213-499 g·mol-1 ), membrane characteristics (RO or NF), feed water matrices, and operational conditions on PFAS rejection. Our results confirmed that size exclusion is a primary mechanism of PFAS rejection by RO and NF, as well as the fact that electrostatic interactions are important when PFAS molecules have sizes less than the NF membrane pores. PRACTITIONER POINTS: Two commercial RO and NF membranes were both evaluated to remove 10 different PFAS. High transmembrane pressures facilitated permeate recovery and PFAS rejection by RO. Electrostatic repulsion and pore size exclusion are dominant rejection mechanisms for PFAS removal. pH, ionic strength, and organic matters affected PFAS rejection. Mechanisms of PFAS rejection with RO/NF membranes were explained by PCA analysis.

Insights into the potential applications of permanganate/peroxymonosulfate systems: enhancement via amorphous MnO2, effects of water matrices, and optimization using response surface methodology.

In this study, we developed a novel self-catalytic oxidation system involving peroxymonosulfate (PMS) and permanganate (KMnO4), named as CUPP, to efficiently mineralize sulfamethoxazole (SMX) in groundwater. It was found that amorphous MnO2 derived from the in situ reduction of KMnO4 can directly adsorb HSO5-, a complex hydroxyl group, mediate the internal disproportionation reaction of HSO5- with the manganese complex, and effectively activate PMS, thereby promoting the oxidation of SMX and its degradation intermediates through sulfonate radiation. Furthermore, by using electron spin resonance (EPR), HPLC/MS full scan, and response surface methodology, the coexistence of HO˙, SO4-˙, O2-˙, 1O2, and active chlorine (Cl2, HOCl) in the CUPP system was confirmed. A total of 24 intermediate products were detected, and four possible degradation pathways were identified for SMX. In addition, it was found that the CUPP system has a strong impact resistance to pH variations, groundwater anions, and natural organic matter stress. Undoubtedly, the CUPP system presents an innovative approach for the degradation of various emerging organic pollutants in groundwater.

Ofloxacin degradation in water and porous media: Synergy effects via hydrogen peroxide activation by a micro electrolytic iron-carbon composite

Ofloxacin (OFL) may cause potential ecological risks since it cannot be effectively removed by conventional biological degradation. The advanced oxidation process is an efficient approach for antibiotic removal. Herein, a heterogeneous system for hydrogen peroxide (H2O2) activation by nanoscale zero-valent iron (nZVI) supported on powdered activated carbon (PAC) composite (nZVI@PAC) was proposed to proceed with the removal of OFL. Typically, OFL (25 mg/L) can be removed up to 94.7 % within 60 min ([H2O2] = 10 mM, [nZVI@PAC] = 125 mg/L, pH = 6, T = 318 K). The effects of initial OFL concentration, pH, nZVI@PAC dosage, H2O2 concentration, and different actual water matrices were examined to explore the application conditions and resistance of the nZVI@PAC/H2O2 system. Meanwhile, the quenching experiment, PMSO probe experiment, and EPR results showed •OH and FeIVO were the dominant reactive species in the system. Moreover, a sensible mechanism for OFL removal was proposed that nZVI@PAC aggregates OFL on its surface by adsorption, and then persistent free radicals (PFRs) and nZVI on the PAC degrade OFL by activating H2O2 to produce •OH and FeIVO. Furthermore, the effect of micro-electronic iron-carbon composite was proved by electrochemical experiments and density functional theory (DFT) calculations. Moreover, the degradation pathway of OFL in the nZVI@PAC/H2O2 system and the toxicity assessment of intermediates were also given. Meanwhile, sequential runs and continuous flow column experiments showed nZVI@PAC/H2O2 system had high stability. This work provides an innovative strategy of an advanced oxidation process based on heterogeneous reactions for organic contaminants removal using metal–carbon catalysts.

Inorganic–organic hybrid quantum dots for AOP-mediated photodegradation of ofloxacin and para-nitrophenol in diverse water matrices

Due to concerns about the accessibility of clean water and the quality of treated wastewater, developing a suitable solution to enhance the water quality is critical. Thus, the current study focused on the synthesis of cadmium-doped CdIn2S4 incorporated in chitosan, forming Cd/CdIn2S4@Ch quantum dots using a solvothermal technique for the efficient photodegradation of hazardous pollutants like ofloxacin and para-nitrophenol through H2O2-mediated AOP. Cd/CdIn2S4@Ch quantum dots were characterized by several advanced methods, including XRD, PL, UV-DRS, FTIR, SEM, HR-TEM, XPS, DSC, TGA, EDX, and Elemental mapping analysis. The influence of varying reaction parameters, such as the effect of organic compounds, inorganic ions, and water matrices, was also investigated. The prepared composite showed outstanding photodegradation efficiency of 85.51 ± 1.35% and 96.70 ± 1.31%, with a rate constant of 0.02334 and 0.15134 min−1, which is about 1.24 and 2.07 times higher than pristine CdIn2S4 for ofloxacin and para-nitrophenol, respectively. The COD values were reduced to 80.67 ± 1.67% for ofloxacin and 88.36 ± 1.43% for para-nitrophenol, whereas the TOC values reduced to 73.49% and 86.34%, respectively, from their initial values. The improved performance is ascribed to the encapsulation of CdIn2S4 by chitosan, leading to the self-doping of cadmium into the photocatalyst, as the incorporated cadmium doping site can generate a local electron accumulation point, improving the charge separation efficacy and surface charge mitigation capability of chitosan nanosheets even further. The scavenger experiments showed that hydroxyl and superoxide radicals played a significant part in the photodegradation of contaminants. Additionally, the quantum dots showed excellent constancy and were recyclable up to six times, suggesting exceptional stability and reusability of the manufactured photocatalyst. The fabricated Cd/CdIn2S4@Ch quantum dots could be an excellent photocatalyst for removing organic pollutants from wastewater in the near future.

Unveiling the mechanisms of peracetic acid activation by iron-rich sludge biochar for sulfamethoxazole degradation with wide adaptability

Advanced oxidation processes (AOPs) based on peracetic acid (PAA) has been extensively concerned for the degradation of organic pollutants. In this study, metallic iron-modified sludge biochar (Fe-SBC) was employed to activate PAA for the removal of sulfamethoxazole (SMX). The characterization results indicated that FeO and Fe2O3 were successfully loaded on the surface of the sludge biochar (SBC). Fe-SBC/PAA system achieved 92% SMX removal after 30 min. The pseudo-first-order kinetic reaction constant of the Fe-SBC/PAA system was 7.34 × 10−2 min−1, which was 2.4 times higher than the SBC/PAA system. The degradation of SMX was enhanced with increasing the Fe-SBC dosage and PAA concentration. Apart from Cl−, NO3− and SO42− had a negligible influence on the degradation of SMX. Quenching experiments and electron paramagnetic resonance (EPR) techniques identified the existence of reactive species, of which CH3C(O)OO•, 1O2, and O2•- were dominant reactive species in Fe-SBC/PAA system. The effect of different water matrices on the removal of SMX was investigated. The removal of SMX in tap water and lake water were 79% and 69%, respectively. Four possible pathways for the decay of SMX were presented according to the identification of oxidation products. In addition, following the ecological structure-activity relationship model (ECOSAR) procedure and the germination experiments with lettuce seeds to predict the toxicity of the intermediates. The acute and chronic ecotoxicity of SMX solution was dramatically diminished by processing with Fe-SBC/PAA system. In general, this study offered a prospective strategy for the degradation of organic pollutants.

Co3O4 electronic-structure tuning via Se doping for peroxymonosulfate activation: Synergy of reactive-oxygen species generation and adsorption–desorption strength

Increasing peroxymonosulfate (PMS) activation efficiency by Co3O4 to produce more reactive sites remains a challenge. Here, we report Se doping to simultaneously tune oxygen vacancy densities, Co2+ active site levels, and the Co3O4 3d-band center for activating PMS to degrade levofloxacin (LEV). The Se-doped Co3O4 (Se@Co3O4) was fabricated by pyrolyzing a mixture of Se powder and Co3O4 precursors. It had many more Co2+ active sites and oxygen vacancies relative to Co3O4. This favored generation of reactive oxygen species that degraded LEV in bulk solution. Density functional theory calculations revealed a downshift of the Co 3d-band in Se@Co3O4 with an enhanced electron-donating ability and an optimized adsorption–desorption strength, which increased reactive oxygen production and subsequent leave from hetero-surface to extinct LEV in bulk solution. Se@Co3O4 exhibited over 95% degradation of 10 mg/L LEV with 0.2 g/L PMS activated within 25 min at 25 °C, while Co3O4 exhibited 20% degradation under the same conditions. The first-order rate constant for LEV degradation by Se@Co3O4 was approximately 42 times that of Co3O4, and it exhibited good PMS activation over the pH range 5.0–9.0. LEV degradation conditions and effects of water matrices were optimized and explored, respectively. The Se@Co3O4/PMS system could still degrade over 85% of LEV after five cycles, as well as pefloxacin, p-nitrophenol, tetracycline and rhodamine B. This suggests its excellent universality. The potential mechanism of PMS activation by the Se@Co3O4 and probable LEV degradation routes were discussed based on the outcomes of active reactive species tests and LEV degradation intermediates confirmed by liquid chromatography-mass spectrometry. This work revealed that Se doping promoted electronic modulation in Se@Co3O4 for PMS activation, and indicated potential high-performance Fenton-like catalysts.

Thermally activated persulfate oxidation of Basic Fuchsin dye: Effect of different operating parameters, kinetic, and thermodynamic study

AbstractThe present paper aims to investigate the efficiency of thermal activation persulfate in eliminating the organic dye “Basic Fuchsin” (BF). In addition, the study attempts to elucidate the effect of different operating parameters, such as persulfate dosage (0.44–4.4 mM), the initial solution pH of (3–10), and temperature (25–50°C), on the process. The effects of various anions and water matrices on BF discoloration were investigated. Thus, the findings revealed that 94.15% of BF can be eliminated using persulfate at a concentration of 4.4 mM and a temperature equal to 50°C. It occurs under the following operating conditions: oxidation time of 60 min, initial pH equal to 6, the pollutant concentration of 10 ppm, and stirring speed equal to 300 rpm. Furthermore, the kinetic study indicated that the degradation of the BF dye using PS followed a first‐order pattern with rate constants varying within a range of 15.3 × 10−3–43.2 × 10−3 min−1. Based on the Arrhenius equation, the activation energy of the studied process was determined to be 29 kJ mol−1, suggesting that a moderate activation energy is required for BF discoloration. The results of the thermodynamic study confirm that the oxidation process is non‐spontaneous and endothermic. Coexisting inorganic anions delayed BF discoloration to varying degrees, and the inhibitory action followed the following order: carbonate > chloride > sulfate > nitrate. Organic pollutants oxidation by the thermal activation of the persulfate is a simple and effective method for the depollution of waste textile water.

Molecular structure-dependent contribution of reactive species to organic pollutant degradation using nanosheet Bi2Fe4O9 activated peroxymonosulfate

Iron-based catalysts have attracted increasing attention in heterogeneous activation of peroxymonosulfate (PMS). However, the activity of most iron-based heterogenous catalysts is not satisfactory for practical application and the proposed activation mechanisms of PMS by iron-based heterogenous catalyst vary case by case. This study prepared Bi2Fe4O9 (BFO) nanosheet with super high activity toward PMS, which was comparable to its homogeneous counterpart at pH 3.0 and superior to its homogeneous counterpart at pH 7.0. Fe sites, lattice oxygen and oxygen vacancies on BFO surface were believed to be involved in the activation of PMS. By using electron paramagnetic resonance (EPR), radical scavenging tests, 57Fe Mössbauer and 18O isotope-labeling technique, the generation of reactive species including sulfate radicals, hydroxyl radicals, superoxide and Fe (IV) were confirmed in BFO/PMS system. However, the contribution of reactive species to the elimination of organic pollutants very much depends on their molecular structure. The effect of water matrices on the elimination of organic pollutants also hinges on their molecular structure. This study implies that the molecular structure of organic pollutants governs their oxidation mechanism and their fate in iron-based heterogeneous Fenton-like system and further broadens our knowledge on the activation mechanism of PMS by iron-based heterogeneous catalyst.

Enhanced degradation performance and mineralization of ciprofloxacin by ionizing radiation combined with g-C3N4/CDs

In this study, the degradation of ciprofloxacin (CIP) was investigated in the synergetic system of electron beam irradiation (EBI) combined with graphite carbon nitride/carbon nanodots (g-C3N4/CDs). The results suggested that the presence of g-C3N4/CDs could not only promote the degradation of CIP but also significantly enhanced the mineralization ratio. At 25 kGy, the mineralization ratio increased from 18.1% to 69.0% while g-C3N4/CDs was added. Regeneration experiments revealed that the g-C3N4/CDs composite possessed good reusability. In addition to finding that the presence of CO32−, HCO3−, NO3− and NO2− obviously restrained the radiolysis process of CIP, the adding of Cl− and SO42− could also have slight inhibitory effects. The effect of various water matrices in EBI&g-C3N4/CDs systems suggested that the degradation efficiency decreased in lake and tap water. Moreover, the studies in the presence of different radical scavengers suggested that ·OH was the main reactive species in the degradation process. The possible degradation pathway of CIP was proposed in the light of intermediate products using Liquid chromatograph-mass spectrometer (LC–MS) analysis coupled with DFT calculations.

Novel 3D sphere-like β-In2S3/Biochar nanoflowers for remediation of dyes in single and binary systems and interpretation using statistical physical modeling

A novel 3D sphere-like β-In2S3/Biochar nanoflowers have been fabricated through the solvothermal process for effectively removing cationic malachite green and methylene blue dye in both single and binary systems. XRD, SEM, EDX, Elemental Mapping, TEM, BET, XPS, and FT-IR were used to characterize the physical and chemical properties of β-In2S3/Biochar. It was found that MG and MB had an adsorption capacity of 636.94 mg/g and 625.02 mg/g for β-In2S3/Biochar in single systems, while in binary systems, they had an adsorption capacity of 564.97 and 438.58 mg/g, respectively. The adsorption capacities in the multicomponent system were calculated using the extended Langmuir modeling, and the kinetic behavior of the adsorption in both systems followed pseudo-second-order kinetics. From the statistical physical modeling, the nD parameter values for MG adsorption obtained were 0.468, 0.498, and 0.612 at 298, 308, and 318 K, and the nD parameter values for MB adsorption were 0.63, 0.833, and 0.896, respectively in the single systems. These results showed that the dyes were adsorbed in a parallel orientation, and the adsorption followed a multi-interaction mechanism. The effect of water matrices and competing species, such as organic and inorganic compounds, are also investigated to find potential applications in real wastewater. In addition, the decrease in adsorption capacity for both dyes in the binary system was credited to the antagonistic effect, and the high efficiency and reusability of the fabricated β-In2S3/Biochar might provide new ideas for developing competent adsorbents to remove dyes from wastewater.

Adsorption of Fluoroquinolone Antibiotics from Water and Wastewater by Colemanite.

Pharmaceutical residues in water and wastewater have become a worldwide problem with environmental and public health consequences. Antibiotics are of special importance because of the emergence of antibiotic-resistant genes. This study evaluates the adsorptive removal of four common fluoroquinolone antibiotics by using natural colemanite as an alternative adsorbent for the first time. Batch adsorption experiments were conducted for the mixture of fluoroquinolones as well as for individual compounds during the isotherm studies. Adsorption kinetic results indicated that the process followed the pseudo-second-order (PSO) model, while the Langmuir model described the sorption isotherms. The effects of pH and temperature on adsorption performance were determined, and the results indicated that the adsorption was endothermic and spontaneous, with increasing randomness at the solid-liquid interface. The effects of real water and wastewater matrices were tested by using tap water, surface water, and wastewater samples. Reusability experiments based on five adsorption-desorption cycles indicated that the adsorption performance was mostly retained after five cycles. The adsorption mechanism was elucidated based the material characterization before and after adsorption. The results indicate that colemanite can be used as an effective and reusable adsorbent for fluoroquinolone antibiotics as well as for other pollutants with similar physicochemical properties.

Adsorptive recycle of phosphate by MgO-biochar from wastewater: Adsorbent fabrication, adsorption site energy analysis and long-term column experiments

Magnesium doped spent coffee grounds (Mg-SCG) biochar was fabricated in this research and its adsorption performance was investigated thoroughly in batch and column studies. The effects of time, pH, organic matter, co-existing anions, and water matrices on phosphate removal were explored. The 500 °C pyrolysis temperature (Mg-SCG-500) was proved to be the optimal condition for phosphate adsorption and achieved 111.20 mg/g theoretical maximum adsorption capacity. The adsorption site energy analysis revealed that 500 °C pyrolysis temperature also provided more sites with suitable adsorption energy for phosphate adsorption. The used Mg-SCG-500 could be efficiently desorbed and regenerated using 1 M NaOH and recalcination. Meanwhile, Mg-SCG showed great stability under realistic conditions. In long-term column experiments, 20 cycles of adsorption were conducted with different contact times, total treated volume, and water matrices. The results proved that the Mg-SCG based column could efficiently remove the phosphate from aqueous solutions. This work would extend the potential application of Mg-SCG based column, acting as a promising solution for phosphate removal and recycle from real wastewater.

Significant roles of surface functional groups and Fe/Co redox reactions on peroxymonosulfate activation by hydrochar-supported cobalt ferrite for simultaneous degradation of monochlorobenzene and p-chloroaniline

CoFe2O4/hydrochar composites (FeCo@HC) were synthesized via a facile one-step hydrothermal method and utilized to activate peroxymonosulfate (PMS) for simultaneous degradation of monochlorobenzene (MCB) and p-chloroaniline (PCA). Additionally, the effects of humic acid, Cl-, HCO3-, H2PO4-, HPO42- and water matrices were investigated and degradation pathways of MCB and PCA were proposed. The removal efficiencies of MCB and PCA were higher in FeCo@HC140–10/PMS system obtained under hydrothermal temperature of 140 °C than FeCo@HC180–10/PMS and FeCo@HC220–10/PMS systems obtained under higher temperatures. Radical species (i.e., SO4•-, •OH) and nonradical pathways (i.e., 1O2, Fe (IV)/Co (IV) and electron transfer through surface FeCo@HC140–10/PMS* complex) co-occurred in the FeCo@HC140–10/PMS system, while radical and nonradical pathways were dominant in degrading MCB and PCA respectively. The surface functional groups (i.e., C-OH and CO) and Fe/Co redox cycles played crucial roles in the PMS activation. MCB degradation was significantly inhibited in the mixed MCB/PCA solution over that in the single MCB solution, whereas PCA degradation was slightly promoted in the mixed MCB/PCA solution. These findings are significant for the provision of a low-cost and environmentally-benign synthesis of bimetal-hydrochar composites and more detailed understanding of the related mechanisms on PMS activation for simultaneous removal of the mixed contaminants in groundwater.

Catalytic ozonation of atrazine with stable boron-doped graphene nanoparticles derived from waste polyvinyl alcohol film: Performance and mechanism

To prepare a high-performance catalyst for heterogeneous catalytic ozonation (HCO) of atrazine (ATZ, a refractory pollutant) in water, graphene nanoparticles (GNPs) were successfully prepared by facile in situ pyrolysis method. Waste polyvinyl alcohol film was chosen as carbonaceous precursor in a “waste-to-treasure” strategy. By introducing boron (B) in the synthesis, the obtained B-doped GNPs (B-GNPs) exhibited more robust HCO performance. The ATZ degradation efficiencies by ozonation, GNPs, and B-GNPs catalytic ozonation after 10 min were 40.2 %, 69.8 %, and 83.2 %, respectively. In contrast to ozone activation in GNPs induced by oxygenated defects, boronated defects dominated ozone decomposition and subsequent reactive oxygen species generation (OH and O2–), imparting B-GNPs with greater activity and stability. Generally, B-doping promoted the electron transfer of B-GNPs, thus enhancing ozone adsorption and degradation. Also, the effect of various water matrices on ATZ degradation during HCO was comprehensively evaluated. Acute toxicity tests indicated rapid detoxification through deep ATZ degradation by B-GNP-catalyzed ozonation. This study provides a robust and efficient carbonaceous catalyst based on a “waste-treats-waste” strategy for environmental remediation, thereby providing insights into the mechanism and application of heteroatom-doped carbonaceous catalysts for the HCO process.