摘要 : Capturing organics from wastewater is recognized as the initial step towards carbon valorization, since the direct valorization of organics in domestic wastewater is limited by the low concentration. An innovative method was proposed in our former research, which utilizes captured organics from wastewater as raw material for producing a coarse flocculant, thereafter, using the coarse flocculant to capture organics from wastewater in a cyclical manner. Hydrothermal processing (HTP) and chemical modification are jointly applied to coarse flocculant production . Besides, the hydrothermal liquid fraction of concentrated organic matter was indicated as the potential effective precursor. However, the role of hydrothermal liquid fraction as precursor for coarse flocculant and the regulatory mechanism remain unclear. Therefore, this study aims to evaluate the characteristics of the hydrothermal liquid fraction under different alkaline addition, temperature and time from the perspective of coarse flocculant preparation. The results demonstrated that the dissolved polymeric substances extracting through HTP and acid precipitation process exhibit a high molecular weight (reaching up to 9929 Da) and abundant functional groups (including C O, C N, OH, C O C, etc.). Furthermore, the addition of NaOH, along with relatively moderate temperature and time were recommended for producing the flocculant precursor. Specifically, this study suggests a temperature of 140 °C and a duration of 30 min for the flocculant precursor producing.

摘要 : Organic membrane fouling is a major obstacle to the application of membrane distillation in low surface tension wastewater treatment. Membrane modification might be an effective way to mitigate membrane fouling. This study mainly explored the mechanism of enhanced anti-fouling performance of the MXene modified PVDF membrane by applying XDLVO theory combined with surface elemental integration (SEI) method. The rough membrane surfaces were first reconstructed using fractal function. Then, the interaction energy between low surface tension substances and the membranes before and after modification was calculated. The results showed that oil droplets and surfactant fouling were mainly caused by hydrophobic attraction due to Lewis acid-base (AB) interaction energy. By modifying the virgin PVDF membrane with MXene nanoparticles, the polar component of membrane surface tension (γAB) increased significantly, so that the interaction energy between all contaminants and membrane surface changed from attraction to repulsion. In addition, roughness weakened the interaction energy between contaminants and membrane surface but significantly lengthened the range of interaction distance, which together determined the ability of the membrane to attract or repel the contaminants. These findings may improve the understanding of the structure-effect relationship between membrane modification and anti-fouling ability, and provide new insights into the membrane modification for MD.

摘要 : The regulation behavior of oxygen vacancies (Vo) at different spatial positions (surface or bulk) in catalysts for selective O 3 catalyzation, along with the reaction pathways evolution was well-investigated in α-MnO 2−x /O 3 systems. Combined characterization methods, systematic organic removal experiments, structure-activity relationship analysis, and theoretical calculations were employed to unveil O 3 decomposition and electron transfer behaviors regulated by surface or bulk Vo. The contribution of electron transfer process (ETP) to atrazine (ATZ) removal was reinforced from 5.2 % to 34.8 % with the formation of bulk Vo, and Vo-rich α-MnO 2−x -2/O 3 system achieved ∼96.5 % ATZ removal along with improved TOC mineralization (∼38 % vs. ∼20 %). Surface Vo facilitated O 3 adsorption, promoting its decomposition into •OH, while bulk Vo not only accelerated •OH production but also withdrew electrons from organics to build ETP. This study shed light on precise modification of metal-based catalysts with Vo to modulate •OH/ETP synergistic processes in catalytic ozonation for efficient water purification .

摘要 : Complete dehalogenation of halogenated organic pollutants has attracted increasing attention, and electrocatalytic reduction processes are considered prospective technologies due to their high selectivity for carbon-halogen bonds. In this study, a vitamin B 12 (VB 12 ) composite electrode was prepared and applied to remove the refractory tribromoacetic acid (TBAA). The reduction process dominated by the VB 12 composite electrode showed a degradation efficiency of 55.2 % for 200 μg/L TBAA within 60 min. Interestingly, UV irradiation considerably increased the efficiency of TBAA for dehalogenation on the VB 12 composite electrode. The photoelectrochemical co-catalytic system of a VB 12 composite electrode coupled with UV (LP UV 254 nm) could remove 92.2 % of TBAA in 20 min with a rate constant 12 times higher than the VB 12 -only electrolysis system. The in situ Raman characterization and cyclic voltammetry tests confirmed that the accelerated formation of Co-Br bonds and the enhanced atomic H mediated ability were responsible for improving debromination efficiency. The degradation of TBAA mainly underwent chemical reactions of debromination and mineralization. Acetic acid, formic acid, formaldehyde, and Br - were the major transformation products of TBAA. Acidic conditions favoured TBAA removal in the UV synergistic VB 12 electrolytic system, and excellent cycling stability of debromination was obtained in complex aqueous environments (actual bodies of water containing various inorganic and organic matter). This research provides an efficient dehalogenation technology for halogenated micropollutants and novel perspectives on the scientific design of photoelectrochemical dehalogenation processes.

摘要 : Iron sludge, produced during the drinking water treatment process, can be recycled as potential iron resource to create environmental functional material. In this study, sulfur-iron composites derived from iron sludge (S–Fe composites) was synthesized through sulfidation and carbonization, and used for the tetracycline (TC) removal under aerobic and anoxic conditions. The reactivities of these as-prepared products were strongly depended on pyrolysis temperatures. In particular, sulfidated nanoscale zero-valent iron loaded on carbon (S-nFe 0 @CIS) carbonized at 800 °C exhibited the highest TC removal efficiency with 86.6% within 30 min at circumneutral pH compared with other S–Fe composites. The crystalline structure of α-Fe 0, FeS x and S 0 as main active sites in S-nFe 0 @CIS promoted the degradation of TC. Moreover, the Fe/S molar ratios significantly affected the TC removal rates, which reached the best value as the optimal S/Fe of 0.27. The results illustrated that the optimized extent of sulfidation could facilitate electron transfer from nFe 0 towards contaminants and accelerate Fe(III)/Fe(II) cycle in reaction system compared to bared nFe 0 @CIS. We revealed that removal of TC by S-nFe 0 @CIS in the presence of dissolved oxygen (DO) is mainly attributed to oxidation, adsorption and reduction pathways. Their contribution to TC removal were 31.6%, 25.2% and 28.8%, respectively. Furthermore, this adsorption-oxygenation with the formation of S-nFe 0 @CIS-TC complexes was a surface-mediated process, in which DO was transformed by the structural FeS x on complex surface to •OH with the generation of H 2 O 2 intermediate. The intermediates of TC and toxicity analysis indicate that less toxicity products generated through degradation process. This study provides a new reclamation of iron sludge and offers a new insight into the TC removal by S-nFe 0 @CIS under aerobic conditions .

摘要 : Chlorine activation-inefficient and the generation of disinfection by-products (DBPs) has indeed limited the application of UV/chlorine process. In this study, the typical metal-organic frameworks (MOFs) NH 2 -MIL53(Fe) were successfully modified with organic ligands containing sulfur functional groups and applied to construct a novel UV-LED-driven heterogeneous chlorine activation system. The generation of intermediate energy levels and the charge redistribution effect on Fe-S bond facilitated the excitation of electrons and realized the effective separation of photohole (h vb + ) and photoelectron (e cb - ). The involvement of S-NH 2 -MIL53(Fe) improved the efficiency of UV-LED/chlorine process by 6 times. The effective activation of HOCl/OCl - by h vb + and e cb - significantly enhanced the yield of HO · and Cl · . More importantly, HOCl/OCl - played a dual role in UV-LED/chlorine/S-NH 2 -MIL53(Fe) process as a precursor for the generation of free radicals and a catalyst for the enhancement of HO · yield, which could achieve efficient removal of the target pollutants at lower chlorine doses. In addition, the presence of low-valent sulfur species and e cb - accelerated the cycle of Fe(II)/Fe(III) and in-situ generation of HO · and Cl · . The known generation of DBPs in UV-LED/chlorine/S-NH 2 -MIL53(Fe) process decreased by 37.9% compared to UV-LED/chlorine process. Developing novel UV-LED/chlorine/S-NH 2 -MIL53(Fe) processes provided a reliable strategy to efficiently purify actual micro-polluted water bodies.

摘要 : As a strong oxidizing agent, ozone is used in some water treatment facilities for disinfection, taste and odor control, and removal of organic micropollutants. Phenylalanine (Phe) was used as the target amino acid to comprehensively investigate variability of disinfection byproducts (DBPs) formation during chlorine disinfection and residual chlorine conditions subsequent to ozonation. The results showed that subsequent to ozonation, the typical regulated and unregulated DBPs formation potential (DBPsFP), including trichloromethane (TCM), dichloroacetonitrile (DCAN), chloral hydrate (CH), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and trichloroacetamide (TCAcAm) increased substantially, by 2.4, 3.3, 5.6, 1.2, 2.5, and 6.0 times, respectively, compared with only chlorination. Ozonation also significantly increased the DBPs yield under a 2 day simulated residual chlorine condition that mimicked the water distribution system. DBPs formations followed pseudo first order kinetics. The formation rates of DBPs in the first 6 hr were higher for TCM (0.214 hr−1), DCAN (0.244 hr−1), CH (0.105 hr−1), TCAcAm (0.234 hr−1), DCAA (0.375 hr−1) and TCAA (0.190 hr−1) than thereafter. The peak DBPsFP of TCM, DCAN, CH, TCAcAm, DCAA, and TCAA were obtained when that ozonation time was set at 5–15 min. Ozonation times > 30 min increased the mineralization of Phe and decreased the formation of DBPs upon chlorination. Increasing bromine ion (Br−) concentration increased production of bromine- DBPs and decreased chlorine-DBPs formation by 59.3%–92.2%. Higher ozone dosages and slight alkaline favored to reduce DBP formation and cytotoxicity. The ozonation conditions should be optimized for all application purposes including DBPs reduction. © 2023

摘要 : Soil cadmium (Cd) contamination is a world-wide challenge and chemical stabilization is the most used remediation strategy. To solve the disadvantages of high stabilizer dosage and cost, we innovated a cost-efficient steam flash heating (SFH) approach to chemically immobilize Cd in contaminated soils, which introduced high-pressure saturated water vapor into soil microstructure, broke their binding with soil particles and accelerated Cd reactions with stabilizers by ultrafast pressure release. Using calcium dihydrogen phosphate, potassium hydrogen phosphate or calcium carbonate as stabilizer, Cd stabilization efficiency was 10.4%, 13.4% and 17.1% higher by SFH than conventional chemical stabilization, and the lowest Cd content in leachate was 0.61 mg/L. Additionally, SFH approach averagely reduced 50.1 ± 7.29% of stabilizer dosage, 34.1% of cost, and 29.9% of CO2 emission. BCR sequential extraction results suggested that acid extractable Cd was preferentially transformed into residual Cd by SFH. Analysis of X-ray absorption near edge structure (XANES) documented that SFH treatment produced more stable Cd-minerals of Cd3(PO4)2, CaCO3-Cd, and CdCO3. Our findings proved the state-of-the-art SFH approach and uncovered its mechanisms to stabilize Cd in contaminated soils, offering a green and cost-efficient remediation alternative for heavy metal contaminated site management. © 2023 Elsevier Ltd

摘要 : The role of H2O molecule during the PMS activation has been rarely followed, although the interfacial mechanism was inseparable from its adsorption and dissociation on catalysts. An efficient catalyst (α-Fe0.9Zn0.1OOH) was synthesized via Zn2+ isomorphous substitution of Fe3+ in α-FeOOH to trigger peroxymonosulfate (PMS) for distinguishing the overlooked interfacial process. The α-Fe0.9Zn0.1OOH/PMS system showed high performance for meclofenamic acid (MCF) degradation (97.0%) owing to the generation of powerful sulfate radicals (SO4•−) and hydroxyl radicals (•OH). Characterization of α-Fe0.9Zn0.1OOH via EDS, ESR and XPS spectra confirmed that Zn2+ doping induced the formation of oxygen vacancy (OV) in the structure. The OV-rich structure promoted the adsorption (Eads = -1.49 eV) and dissociation of H2O to form surface hydroxyl groups (-OHdiss), which was different from the structure -OHlatt. By ATR-FTIR tests in heavy water (D2O), the -OHdiss could be exchanged by PMS, and forming surface complexed ≡Fe(III)-(HO)-OSO3−, which enlarged the O-O bond (from 1.317 Å to 1.506 Å). The electron transfer inner ≡Fe(III)-(HO)-OSO3− benefited O-O cleavage thus inducing SO4•− generation. Overall, the presence of OV in α-Fe1-xZnxOOH greatly promoted this spontaneous process. © 2023 Elsevier B.V.

摘要 : Tap water is boiled by families across the globe in their daily life for cooking food and beverages, as well as for controlling some chlorine-resistant organisms to improve the water quality. However, the effects of boiling methods (heating temperature, heating modes, open or closed containers) on water quality, in particular the reduction of disinfection byproducts (DBPs), are unclear. This comprehensive research demonstrates that during the heating process, trihalomethanes (THMs) were markedly decreased, haloacetonitriles (HANs) were drastically reduced and sometimes completely removed, while haloacetic acids (HAAs) were reduced the least. Heating to boiling in open containers reduced DBPs concentrations more than heating in the closed containers. Residual chlorine from 0.1 to 5.0 mg/L did not affect the removal of HANs, but could increase concentrations of HAAs likely due to reaction of organic matter with chlorine at elevated temperatures. THMs demonstrated good removal at 0.1–1 mg/L residual chlorine, but less removal at 5 mg/L residual chlorine. Sodium chloride (salt), often added as seasoning agent in the process of family cooking, was found to have little effect on the removal of DBPs during cooking and boiling. Compared with the toxicity of DBPs in tap water, boiling could greatly reduce both the cytotoxicity and carcinogenicity through removal of DBPs. Consequently, boiling of tap water had a significant effect on reducing human exposure to DBPs and their associated toxicities. © 2023 Elsevier B.V.