Real Water Matrices Research Articles

Activation of sodium percarbonate with Fe3O4 @MXene composite for the efficient removal of bisphenol A

Sodium percarbonate (SPC) has been considered as a promising substitute of H2O2 in Fenton reaction due to its lower cost and higher safety, while the frequently-applied homogeneous activation of SPC by metal ions still faces the recovery difficulties. Herein, a Fe3O4 @MXene composite was prepared by anchoring Fe3O4 onto the surface of Ti3C2-based MXene, to heterogeneously activate SPC for bisphenol A (BPA) degradation. The performance of Fe3O4 @MXene/SPC process was evaluated under varies conditions. The results indicated that BPA could be effectively degraded by Fe3O4 @MXene/SPC process, which exhibited much higher organic degradation rate comparing to other heterogeneously activated SPC processes with iron-bearing materials. The introduction of MXene as substrate into the composite not only increased the dispersibility and stability of Fe3O4, but enhanced the Fe(II)/Fe(III) cycle, which promoted the SPC activation. Multiple reactive oxygen species including •OH, CO3•–, and 1O2 were involved in the BPA oxidation while the major contributing species varies with the pH. Additionally, the process worked well in real water matrices, while exhibiting higher selectivity toward organics containing benzene ring. This work provides a prospective heterogeneous material for SPC activation and will facilitate the application of SPC in wastewater treatment.

Chlorination of methotrexate in water revisited: Deciphering the kinetics, novel reaction mechanisms, and unexpected microbial risks

Chlorination of a typical anticancer drug with annually ascending use and global prevalence (methotrexate, MTX) in water has been studied. In addition to the analysis of kinetics in different water/wastewater matrices, high-resolution product identification and in-depth secondary risk evaluation, which were eagerly urged in the literature, were performed. It was found that the oxidation of MTX by free available chlorine (FAC) followed first-order kinetics with respect to FAC and first-order kinetics with respect to MTX. The pH-dependent rate constants (kapp) ranged from 170.00 M−1 s−1 (pH 5.0) to 2.68 M−1 s−1 (pH 9.0). The moiety-specific kinetic analysis suggested that 6 model substructures of MTX exhibited similar reactivity to the parent compound at pH 7.0. The presence of Br− greatly promoted MTX chlorination at pH 5.0–9.0, which may be ascribed to the formation of bromine with higher reactivity than FAC. Comparatively, coexisting I− or humic acid inhibited the degradation of MTX by FAC. Notably, chlorination effectively abated MTX in different real water matrices. The liquid chromatography-high resolution mass spectrometry analysis of multiple matrix-mediated chlorinated samples indicated the generation of nine transformation products (TPs) of MTX, among which seven were identified during FAC oxidation for the first time. In addition to the reported electrophilic chlorination of MTX (the major and dominant reaction pathway), the initial attacks on the amide and tertiary amine moieties with C-N bond cleavage constitute novel reaction mechanisms. No genotoxicity was observed for MTX or chlorinated solutions thereof, whereas some TPs were estimated to show multi-endpoint aquatic toxicity and higher biodegradation recalcitrance than MTX. The chlorinated mixtures of MTX with or without Br− showed a significant ability to increase the conjugative transfer frequency of plasmid-carried antibiotic resistance genes within bacteria. Overall, this work thoroughly examines the reaction kinetics together with the matrix effects, transformation mechanisms, and secondary environmental risks of MTX chlorination.

Dexamethasone degradation in aqueous medium by a thermally activated persulfate system: Kinetics and transformation products

Dexamethasone (DEX) is a synthetic steroid hormone that, owing to its endocrine disruptive effects, has the potential to be detrimental. DEX must be successfully removed during drinking water treatment to preserve human and aquatic animals' health. This study investigates the thermally activated persulfate (TAP) process for the efficient decomposition of DEX. The effectiveness of several variables such as pH, persulfate dose, DEX concentration, reaction temperature, and water matrices was studied. Removal of 500 μg/L DEX reached 100 % by using 100 mg/L of persulfate in ultrapure water (pH = 7) at 50 °C, within 45 min of reaction time. DEX removal usually followed exponential decay. The removal efficiency of DEX in the TAP process was pH-dependent, as 61 % of DEX was removed at a pH value of 9. In contrast, complete degradation was achieved under acidic and near neutral conditions.Moreover, environmentally relevant degradation experiments showed that, in principle, the presence of bicarbonate ions and humic acid had a negative effect on DEX decomposition by reducing the percentage removal of the target compound by >50 %. Six transformation products derived from DEX oxidation were identified using high-resolution LC-MS. TAP system could be proposed as a promising application for removing steroid hormones n real water matrices after process optimization in real conditions.

Improving the ozone-activated peroxymonosulfate process for removal of trace organic contaminants in real waters through implementation of an optimized sequential ozone dosing strategy

The ozone-activated peroxymonosulfate process (O3/PMS) has received increasing attention for the removal of trace organic contaminants (e.g. pesticides and pharmaceuticals) from water bodies. However, the ozone dosing strategy has not yet been properly investigated, especially in real water matrices. Typically, one-step dosing is applied in literature. Nevertheless, optimal dosing is an important step for improving the process. This study investigates the effect of sequential ozone dosing on the PMS activation, atrazine (ATZ) removal, residual ozone concentration and radical exposure, and compares the results to those of a one-step ozone dosing approach. Experiments were performed in three water matrices with a different (in)organic content, i.e. secondary effluent, surface water and groundwater. In all matrices, the highest PMS activation was reached when applying three sequential ozone doses (3 × 5 mg O3/L). This resulted in a 3 times higher ATZ removal efficiency (up to 46 %) in secondary effluent compared to that obtained with a one-step ozone dosing (15 mg O3/L). In surface water and groundwater, similar ATZ removal (>90 %) was observed among the different ozone dosing strategies. However, the sulfate radical (SO4●−) exposure increased after each ozone addition. After three ozone additions of 5 mg/L, SO4●− contributed for 9 %, 26 % and 54 % to ATZ removal in respectively secondary effluent, surface water and groundwater. This high SO4●− contribution compared to ●OH contribution is an advantage as the selectivity of SO4●− gives rise to less radical scavenging by bulk organic matter and thus increases the (cost-)effectiveness of the O3/PMS process.

Hydrothermal synthesis of 3D cauliflower anatase TiO2 and bio sourced activated carbon: adsorption and photocatalytic activity in real water matrices

ABSTRACT The development of advanced photocatalyst for the complete and sustainable removal of emerging organic pollutants such as pharmaceuticals in wastewater is still challenging. Thus, a new three-dimensional cauliflower of TiO2 immobilised on a bio sourced activated carbon (AC/3D-TiO2) was successfully synthesised by a hydrothermal method. Its morphological and physicochemical properties were well-characterised with a pure 3D-TiO2 anatase phase, a high surface area (763 m2.g−1) and a cauliflower-shaped morphology composed of TiO2 tubes in a radial direction at a micrometric scale. 3D-TiO2-AC photocatalytic activity on carbamazepine (CBZ), in water showed that around 90% of CBZ elimination is obtained after 4 h of exposure, that is 1.5 times more efficient than commercial TiO2 P25. This was confirmed on five pharmaceuticals (CBZ, ketoprofen, sulfamethoxazole, ciprofloxacin and diclofenac) by measuring their adsorption, elimination, and mineralisation in wastewater highlighting the promising application of AC/3D-TiO2 in the treatment of wastewaters.

Elimination of neonicotinoids by ozone-based advanced oxidation processes: Kinetics and performance in real water matrices

The Decision 2018/840 included some neonicotinoid insecticides (thiamethoxam (TMX), imidacloprid (ICP), clothianidin (CTD), thiacloprid (TCP), and acetamiprid (AMP)) within the watch list of substances for Union-wide monitoring in the field of water policy due to their potential risk to human health and the environment. In this work, the study of the elimination of these five neonicotinoids present in waters by ozone-based oxidation treatments has been carried out. While AMP and TCP presented very low rate constants with ozone and were hardly degraded, CTD (ozone rate constant of 116 M−1 s−1 at pH ≥ 7) and TMX (ozone rate constant of 22.7 M−1 s−1 for the studied pH range) were partially degraded by ozone. Furthermore, ICP ozonation showed a great pH dependence, with increasing ozone rate constant values from 2.7 M−1 s−1 at pH 5 to 160 M−1 s−1 at pH 9. In addition, rate constants for the reaction of neonicotinoids with hydroxyl radicals (•OH) were determined to be in the range (2.0–4.5)·109 M−1 s−1. The specific contribution of direct ozonation and radical pathways to the overall neonicotinoid degradation was evaluated, being the indirect oxidation with •OH dominant over direct ozone reactions. The influence of real water constituents such as dissolved organic matter (DOM) and bicarbonate, both acting as radical scavengers, on the ozonation process was negative. The ozone dose and the specific ozone dose required to remove neonicotinoids from real water matrices were higher than 5 mg/L and 1 mg O3 mg DOC-1, respectively, typically applied in water treatment. However, the application of the ozone-based advanced oxidation processes O3/H2O2 and O3/activated carbon provided an appreciable improvement in the elimination of neonicotinoids compared to ozone alone. Therefore, ozone-based advanced oxidation processes are needed to sufficiently abate neonicotinoids in contaminated waters.

Degradation of Sulfamethoxazole Using a Hybrid CuOx–BiVO4/SPS/Solar System

In recent years, advanced oxidation processes (AOPs) demonstrated great efficiency in eliminating emerging contaminants in aqueous media. However, a majority of scientists believe that one of the main reasons hindering their industrial application is the low efficiencies recorded. This can be partially attributed to reactive oxygen species (ROS) scavenging from real water matrix constituents. A promising strategy to cost-effectively increase efficiency is the simultaneous use of different AOPs. Herein, photocatalysis and sodium persulfate activation (SPS) were used simultaneously to decompose the antibiotic sulfamethoxazole (SMX) in ultrapure water (UPW) and real water matrices, such as bottled water (BW) and wastewater (WW). Specifically, copper-promoted BiVO4 photocatalysts with variable CuOx (0.75–10% wt.) content were synthesized in powder form and characterized using ΒΕΤ, XRD, DRS, SEM, and HRTEM. Results showed that under simulated solar light irradiation alone, 0.75 Cu.BVO leads to 0.5 mg/L SMX destruction in UPW in a very short treatment time, whereas higher amounts of copper loading decreased SMX degradation. In contrast, the efficiency of all photocatalytic materials dropped significantly in BW and WW. This phenomenon was surpassed using persulfate in the proposed system resulting in synergistic effects, thus significantly improving the efficiency of the combined process. Specifically, when 0.75 Cu.BVO was added in BW, only 40% SMX degradation took place in 120 min under simulated solar irradiation alone, whereas in the solar/SPS/Cu.BVO system, complete elimination was achieved after 60 min. Moreover, ~37%, 45%, and 66% synergy degrees were recorded in WW using 0.75 Cu, 3.0 Cu, and 10.0 Cu.BVO, respectively. Interestingly, experimental results highlight that catalyst screening or process/system examination must be performed in a wide window of operating parameters to avoid erroneous conclusions regarding optimal materials or process combinations for a specific application.

Enhanced solar inactivation of fungal spores by addition of low-dose chlorine: Efficiency and mechanism

This work demonstrated that the solar inactivation of fungal spores was enhanced by addition of low-dose chlorine. Although the effect of low-dose chlorine alone (2.0 mg/L) on culturability of fungal spores was negligible, the solar/chlorine inactivation on fungal spores performed better than solar alone inactivation, with a lower shoulder length and a higher maximum inactivation rate constant. The enhanced inactivation of Aspergillus niger can be ascribed to the membrane oxidation by chlorine, and the enhanced inactivation of Penicillium polonicum can be ascribed to the membrane oxidation by chlorine and ·OH (·OH plays a major role). The oxidization by chlorine and ·OH led to an increase in membrane permeability of fungal spores, which enhanced the solar inactivation, resulting in an increase in intracellular ROS and more serious morphological damage. Due to the presence of background substances such as dissolved organic matter and metal ions (Fe2+, Mn2+, etc.), the inactivation efficiency in real water matrices was decreased. The main disinfection by-products (DBPs) produced in the inactivation of fungal spores in chlorine alone and solar/chlorine treatments were dichloroacetic acid, trichloroacetic acid, trichloroacetone and trichloromethane. Generally, DBPs formation in solar/chlorine treatment was lower than those in chlorine alone treatment. Moreover, the regrowth potential of the two genera of fungal spores in R2A medium could be inhibited by adding low-dose chlorine.

Radiolytic degradation of β-lactam and tetracycline antibiotics in the presence of protein

In this study, to explore the influence of protein on antibiotics degradation during ionizing irradiation, the binding interaction between bovine serum albumin (BSA) and the broad spectrum β-lactam and tetractycline antibiotics and its effect on antibiotic degradation were investigated. Static quenching happened between BSA and antibiotics involving penicillin G (PEG), cephalosporin C (CPC), oxytetracycline (OTC) and tetracycline hydrochloride (TTC), indicating the formation of non-fluorescence complexes. The binding capacity followed the order: TTC > CPC > OTC > PEG. As exposed to γ-irradiation, the β-lactam antibiotics showed a higher degradation rate than the tetracyclines. The degradation rate constant (k) of CPC and PEG was 1.4–2.0 times higher than that of OTC and TTC. In presence of BSA, the k values (kBSA) of all the four antibiotics decreased greatly and the degradation rate of CPC and PEG was still higher by 1.2–1.3 times than that of OTC and TTC. No correlation between k/kBSA and the binding affinity was observed. The presence of BSA has little effect on the trend of abatement of antimicrobial activity to S. aureus during γ-irradiation. This suggests that the inhibition of protein to antibiotic degradation was mainly attributed to the competition of protein for the active species such as ·OH radical formed during γ-irradiation, while the binding ability of protein to antibiotics has no obvious effect. The results of this study contributed to develop technical strategies to improve the removal of antibiotics completely in real water matrices.

Flow-through integration of FeOCl/graphite felt-based heterogeneous electro-Fenton and Ti4O7-based anodic oxidation for efficient contaminant degradation

Improvement to the synergistic performance of cathodic electro-Fenton (EF) and anodic oxidation (AO) has been severely restricted by the tendency for ineffective decomposition of cathode-produced H2O2 at the non-active anode and poor OH utilization. Herein, a paired heterogeneous EF-AO flow-through system, consisting of an FeOCl-deposited graphite felt (FeOCl/GF) cathode and a Ti4O7 membrane anode, was constructed for rapid degradation of oxytetracycline (OTC). The real-time spatiotemporal distribution of H2O2 was systematically investigated and results revealed that the necessity for H2O2 diffusion was eliminating in the proposed system, thus contributing a 2.66-fold increase with respect to OTC degradation kinetics compared to the conventional homogeneous EF-AO system. Meanwhile, the flow-through configuration demonstrated significantly enhanced OH utilization with a 6.65-fold increase in the OTC degradation rate constant compared to the batch mode system. In addition, the EF-AO flow-through system demonstrated a high OTC degradation rate (>80 %) over a wide pH range from 3 to 7 and with different real water matrices. This work opens new avenues for advanced treatment of refractory wastewater using electrochemical advanced oxidation processes.

Thermally activated persulfate oxidation of ampicillin: Kinetics, transformation products and ecotoxicity

The heat-activated persulfate system showed encouraging results for the destruction of the widely used antibiotic Ampicillin (AMP). AMP removal follows exponential decay, and the observed kinetic constant was enhanced with persulfate (PS) dosage at the range 50–500 mg L−1 and temperature (40–60 °C), while AMP thermolysis at 60 °C was almost negligible. The apparent activation energy was estimated to 124.7 kJ mol−1. Alkaline conditions, water matrix constituents like bicarbonates, humic acid, and real water matrices retarded AMP oxidation. Experiments performed with tert-butanol and methanol as scavengers demonstrated the contribution of sulfate radicals as the dominant reactive species. Seven transformation products (TPs) of AMP have been identified from AMP destruction. An EC50 value equal to 187 mg L−1 was calculated for 72 h of exposure of the microalgae Chlorella sorokiniana to AMP. According to the ecotoxicity experiments that conducted after treatment of AMP with PS for different reaction times, no important inhibition of microalgae was noticed for contact time of 72 h and 10 d. These results indicate the formation of no toxic AMP by-products for the applied experimental conditions.

Hydrogen sulfite promoted the activation of persulfate by μM Fe2+ for bisphenol A degradation.

This study evaluated the improvement of bisphenol A (BPA) elimination through hydrogen sulfite (HS) coupling with persulfate (PS) activated by low amounts of Fe2+. Under the optimum condition (10μM Fe2+, 0.6mM HS, 0.8mM PS, pH = 4.0), 100% BPA (5μM) was removed within 15min. Sulfate radical (SO4•-) and singlet oxygen (1O2) were confirmed as the primary active species for BPA degradation in the Fe2+/HS/PS system, and the steady-state concentration of SO4•- and 1O2 was 2.43 × 10-9M and 1.67 × 10-9M, respectively. Besides, FeHSO3+ and FeOHSO3H+ were the main iron species in the Fe2+/HS/PS system. The removal potency of BPA depended on the operation parameters, such as chemical reagent dosages, reaction temperature, and the solution initial pH. The impact of NO3-, SO42-, and humic acid (HA) on BPA removal was negligible, whereas Cl-, HCO3-, and HPO42- restrained BPA decomposition. Two injections of HS could improve the limitation of BPA degradation efficiency due to the rapid consumption of HS in the reaction process. The lower removal efficiency of BPA was observed in real water matrices than that in ultrapure water. Whatever, up to 58.1%, 66.3%, 68.1%, and 88.1% of BPA were removed from domestic wastewater, lake water, river water, and tap water within 10min, respectively. In addition, the BPA degradation process was characterized by the 3D fluorescence spectra technique, which indicated the BPA oxidation intermediates also have fluorescence characteristics. Moreover, 6 intermediate products were identified, and the possible degradation pathways of BPA were proposed. Additionally, the Fe2+/HS/PS system also exerted an excellent performance for the removal of other representative organic contaminants including enrofloxacin, acid orange 7, acetaminophen, and phenol. All results indicated that the Fe2+/HS/PS system could be a promising method for organic pollutant removal.

Radix Astragali residue-derived porous amino-laced double-network hydrogel for efficient Pb(II) removal: Performance and modeling

Valorizing solid waste for heavy metal adsorption is highly desirable to avoid global natural resources depletion. In this study, we developed a new protocol to valorize Radix Astragali residue (one of the Chinese medicine residues) into a low-cost, chemically robust, and highly permeable (ca. 90%) amino-laced porous double-network hydrogel (NH2-CNFs/PAA) for efficient Pb(II) adsorption. The NH2-CNFs/PAA showed (i) excellent Pb(II) adsorption capacity (i.e., 994.5 mg g−1, ~4.8 mmol g−1), (ii) fast adsorption kinetics (kf = 2.01 ×10−5 m s−1), (iii) broad working pH range (2.0–6.0), and (iv) excellent regeneration capability (~15 cycles). (v) excellent performance in various real water matrices on Pb(II) removal. Moreover, its high selectivity (distribution coefficient Kd ~2.4 ×106 mL g−1) toward Pb(II) was owing to the present of abundant amino groups (-NH2). Furthermore, the fix-bed column test indicated the NH2-CNFs/PAA can effectively remove 114.6 bed volumes (influent concentration ~5000 μg L−1) with an enrichment factor 10.9. The full-scale system modeling (i.e., pore surface diffusion model (PSDM)) has been applied to predict the NH2-CNFs/PAA performance on Pb(II) removal. Overall, we have provided an alternative “win-win” scenario that can resolve the Chinese medicine residues disposal issue by valorizing it into high performance gel-based adsorbents for efficient heavy metal removal.

Facile synthesis of magnetic ZnFe2O4/AC composite to activate peroxydisulfate for dye degradation under visible light irradiation.

Heterogeneous photocatalysis/persulfate oxidation process has been considered as a promising technology for dye contaminants removal. The magnetic ZnFe2O4/active carbon (AC) composites were hydrothermally synthesized and firstly used to activate peroxydisulfate (PDS) for rhodamine B (RhB) degradation under visible LED light irradiation. The optimized Vis-ZnFe2O4/AC(4/1)-PDS system can enhance the RhB degradation efficiency by 32.01% and 13.87% compared with Vis-ZnFe2O4-PDS and Vis-AC-PDS systems, respectively. The influence of operational parameters such as catalyst dosage (0.2 - 0.4g L-1), PDS concentration (1.0 - 2.0g L-1), temperature (25 - 45°C), solution pH (2.7 - 10.9), and coexisting inorganic ions (Cl-, NO3-, HCO3-, PO43-, Cu2+, Fe3+, and Ca2+) on RhB degradation was studied, and 100% of RhB (20mg L-1) was degraded after 80min at operational condition: 0.30g L-1 of ZnFe2O4/AC(4/1) and 1.5g L-1 of PDS, solution pH of 2.74, reaction temperature of 25°C. The quenching experiments, EPR test, and XPS analysis were employed to reveal the proposed mechanism, which demonstrated that 1O2 played a more important role than other reactive species (SO4•-, •OH, O2•-, and h+) in RhB degradation. The generation of 1O2 via the two routes was as follows: (i) the in situ formed active oxygen (O*) reacted with HSO5- to produce 1O2; (ii) O2•- was oxidized by h+ to form 1O2. After five consecutive cycles, the photodegradation efficiency of RhB by ZnFe2O4/AC(4/1) catalyst slightly decreased from 88.52 to 83.92%, indicating the excellent reusability of ZnFe2O4/AC(4/1) photocatalyst. As designed, Vis-ZnFe2O4/AC-PDS oxidation system can effectively remove RhB from the different real water matrices, and the degradation efficiency of RhB in tap water, river water, and secondary effluent was 78.24%, 79.55%, and 74.53% after 80min of reaction, respectively.

Boosting non-radical oxidation in peroxydisulfate activation with carbonaceous catalytic membranes by coupling structural defects and nitrogen doping sites

Non-radical oxidation is a critical pathway of peroxydisulfate (PDS) activation for organic degradation with metal-free carbonaceous nanomaterial. In this study, reduced graphene oxide (rGO) sheets with carbon to oxygen atomic ratios of 2.9 and 6.6 (rGO2.9 and rGO6.6) were composited with pristine or nitrogen-doped carbon nanotubes (CNTs or N-CNTs) to fabricate rGO2.9/CNTs, rGO2.9/N-CNTs, rGO6.6/CNTs, and rGO6.6/N-CNTs catalytic membranes. These membranes were employed to perform in-situ catalytic oxidation to remove N4-acetyl-sulfamethoxazole (NSMX) as the target pollutant in continuous filtration mode. The results showed that rGO6.6/N-CNTs coupled structural defects and nitrogen (N)-doping sites to obtain superior water flux and efficient NSMX removal via PDS activation. After 50 h of continuous filtration experiments, rGO6.6/N-CNTs exhibited NSMX removal rates (rNSMX) of 16.3 mg.m−2.h−1 at a carbon loading dosage of 8 g.m−2, which was 3.1-, 2.2-, and 1.4-times higher than the values for rGO6.6/CNTs, rGO2.9/N-CNTs, and rGO2.9/CNTs, respectively. N-doping sites took precedence over structural defects in activating PDS and enhanced the catalytic stability of carbon mats. In addition, surface chemical characterization and radical quenching experiments verified that the singlet oxygen (1O2) and surface-active species dominated in NSMX degradation as non-radical pathways. Although carbon loading, PDS dosage, initial pH, inorganic ions, and natural organic matter (NOM) influenced in-situ catalytic oxidation, both higher rNSMX and lower transmembrane pressures were achieved with rGO6.6/N-CNTs in real water matrices as compared to rGO6.6/CNTs. Further rational tailoring of carbonaceous catalytic membranes should focus on improving the catalytic stability and anti-fouling performance in advanced water treatment.

Activation of ozone by peroxymonosulfate for selective degradation of 1,4-dioxane: Limited water matrices effects

The presence of 1,4-dioxane in various water streams poses a threat to the health of human beings. In this study, the oxidative combination of ozone with peroxymonosulfate (PMS) was for the first time used to remove 1,4-dioxane from water. Near complete abatement of 1,4-dioxane was achieved by ozone-PMS after reaction of only 15 min and the degradation kinetics was found to be positively correlated with doses of PMS and ozone. Ozone-PMS oxidation had the optimum performance at slight base pH values. Both sulfate radicals and hydroxyl radicals were generated in ozone-PMS oxidation and these radicals resulted in the degradation of 1,4-dioxane. The effects of common water constituents and real water matrices were investigated. It was found that bicarbonate ions with a concentration up to 10 mM had a slight promoting effect, while either chloride ions or natural organic matter inhibited only slightly the degradation. Meanwhile, no obvious difference in the degradation of 1,4-dioxane was found among the real water matrices and deionized water, which demonstrates that ozone-PMS oxidation has high tolerance and stability. The results from this study demonstrate that ozone-PMS may be a promising technology for the removal of 1,4-dioxane from various water matrices.

Non-radicals dominated degradation of sulfamethoxazole by a chemical-less microwave enhanced photolysis process

A chemical-less microwave enhanced photolysis process (named MW/UV) was established for sulfamethoxazole (SMX) degradation and the mechanisms were specifically studied. 96.7% of SMX could be removed in an extremely short reaction time of 140 s under 400 W of microwave and 23.0 mW/cm2 of UV light at 254 nm. The half-live of SMX was greatly shortened to 5 s in MW/UV process, compared with 67 s in UV process and 1386 s in MW process. MW/UV process was also effective when applied to complex real water matrices, such as river water, seawater, and synthetic waste water. Non-thermal effects of microwave were found to play an essential role in elevating photolysis degradation efficiency. The ROS formation detected by quenching experiments and EPR test showed that SMX degradation by MW/UV followed non-radicals dominated method, although 1O2 and OH co-existed in this system. 16 intermediates in total were detected by HPLC-Q-TOF and three degradation pathways based on 1O2 and OH oxidation were proposed according to the structural characteristics of the intermediates. Besides, toxicity evaluation of SMX and its intermediates revealed that MW/UV process could effectively reduce the toxicity of SMX. This study provides an efficient and promising scheme for practical SMX degradation.

Facilitated physisorption of ibuprofen on waste coffee residue biochars through simultaneous magnetization and activation in groundwater and lake water: Adsorption mechanisms and reusability

The adsorption of ibuprofen (IBU) onto the pristine (CB), magnetic (MCB), and simultaneously magnetic activated waste coffee residue biochars (MACB) in groundwater and lake water was rigorously investigated in order to offer profound insights into the differences in their adsorption mechanisms and performances (i.e., adsorption capacity and separability). The higher adsorption capacity of IBU for MACB compared CB and MCB in groundwater and lake water was mainly attributed to the well-developed micropore structures of MACB via the simultaneous magnetization and activation. These phenomena were pronounced for groundwater than lake water due to its lower dissolved organic carbon concentrations. The calculated kinetic, intra-particle diffusion, isotherm, and thermodynamic parameters indicate that the adsorption of IBU onto CB, MCB, and MACB proceeded spontaneously and endothermically and their adsorption processes in groundwater and lake water were mainly governed by the physisorption (i.e., pore-filling effects, hydrogen bonding, and π-π electron donor-acceptor interactions), liquid film diffusion, and intra-particle diffusion. The noticeable increase of the X-ray photoelectron spectroscopy peak intensity related to the CO bond of the carbonyls in IBU-loaded MACB suggests that the accelerated pore-filling effects via the simultaneous magnetization and activation lead to the adsorption capacity improvement of IBU in groundwater and lake water. From the superior reusability of MACB in 3–4 adsorption-desorption cycles even under real water matrices (reuse efficiency > 60%), it can be postulated that the simultaneous magnetization and activation might provide a practicable way for enhancing the adsorption capacity of IBU toward waste coffee residue biochars and their separability in groundwater and lake water.

Highly efficient manganese (III) oxide submerged catalytic ceramic membrane for nonradical degradation of emerging organic compounds

In this study the performance of catalytic ceramic membranes in activating peroxymonosulfate (PMS) for the degradation of emerging organic contaminants (EOCs) was investigated. The catalytic ceramic membrane (MnCM) integrated with Mn2O3 nanoparticles was fabricated by a solid-state sintering method. Physical and chemical properties of MnCM were characterized by SEM/EDX, XRD, BET, AFM and XPS. The MnCM/PMS system has shown excellent decontamination efficiencies (81–97% removal) for different EOCs. Acetaminophen (APAP) has been efficiently degraded by MnCM/PMS in different real water matrices and harsh water conditions. Based on results of quenching experiments and electron paramagnetic resonance (EPR) analyses, non-radical pathway with singlet oxygen (1O2) was the dominant ROS for the degradation of EOCs. The membrane pores in active layer acted as micro-reactors for the interaction among active sites, PMS, and EOCs. The MnCM/PMS system showed outstanding catalytic stability with high mineralization (TOC removal of ∼ 65%) and negligible leaching of the manganese (1.3–1.5 µg/L) in permeate. Hydroxylation and C-N bond cleavage were found to be the main degradation pathways of APAP by MnCM/PMS system. The MnCM prepared in this study with excellent performance could be a way forward for applications at large-scale or full-scale water systems suffering from heavy loads or trace amount of refractory organic compounds.

NaOH-assisted H2O2 post-modification as a novel approach to enhance adsorption capacity of residual coffee waste biochars toward radioactive strontium: Experimental and theoretical studies

In this study, NaOH-assisted H2O2 post-modification was proposed as a novel strategy to enhance the adsorption of radioactive strontium (Sr) onto residual coffee waste biochars (RCWBs). To validate its viability, the adsorption capacities and mechanisms of Sr(II) using pristine (RCWBP), H2O2 post-modified (RCWBHP), and NaOH-assisted H2O2 post-modified residual coffee waste biochars (RCWBNHP) were experimentally and theoretically investigated. The highest adsorption capacity of Sr(II) for RCWBNHP (10.91 mg/g) compared to RCWBHP (5.57 mg/g) and RCWBP (5.07 mg/g) was primarily attributed to higher negative surface zeta potential (RCWBNHP = –5.66 → −30.97 mV; RCWBHP = –0.31 → −11.29 mV; RCWBP = 1.90 → −10.40 mV) and decoration of Na on the surfaces of RCWBP via NaOH-assisted H2O2 post-modification. These findings agree entirely with the theoretical observations that the adsorption of Sr(II) onto RCWBP and RCWBHP was controlled by electrostatic interactions involving carbonyls whereas enriched carboxylic acids and decorated Na on the surfaces of RCWBNHP through the replacement of Mg and K by NaOH-assisted H2O2 modification stimulated electrostatic interactions and cation exchanges governing the adsorption of Sr(II). Hence, NaOH-assisted H2O2 post-modification seemed to be practically applicable for improving the adsorption capacity of Sr(II) using RCWB-based carbonaceous adsorbents in real water matrices.