Peracetic acid-based electrochemical treatment of sulfamethoxazole and real antibiotic wastewater: Different role of anode and cathode

Dynamic electrode reconfiguration promotes in situ electrochemical peracetic acid synthesis for selective water decontamination

In situ synthesis and activation of peracetic acid (PAA) for water decontamination is a promising way to overcome the transport and storage problems in PAA applications. Here, an in situ electrochemical PAA synthesis and activation system is constructed using RuO2-Ti "active" electrode and graphite plate as the anode and the cathode, respectively. PAA is efficiently generated at the RuO2-Ti anode with a maximum real-time concentration of ∼1020 μM and a negligible precursor loss of 2.91 % after 180 min, and can be activated at the cathode to destruct a refractory pollutant (i.e., benzoic acid (BA)) with the rate constant of 0.22-0.28 h-1, even under the interference of co-existing anions. Multiple pieces of evidence, including differential electrochemical mass spectrometry, sulfoxide probing test, and electron paramagnetic resonance spectroscopy, indicate that the oxygen-atom-transferring oxidation of CH3COO- by a high-valent ruthenium-oxo intermediate (i.e., RuO3) in situ formed through the electrode reconfiguration between RuO2 and chem-sorbed HO• mainly accounts for PAA synthesis. Acetylperoxyl radical (CH3C(O)OO•) was evidenced as the dominant species for BA degradation. This study proposes an in situ strategy to electrochemically synthesize and activate PAA for selective water decontamination and enriches the understandings of the mechanism of "active" electrode in peroxide synthesis.

Modification of bacterial cellulose by MoBTx MBene and 1,4-dithiothreitol for rapid and efficient adsorption of indomethacin and losartan potassium

Lowering the threat of antibiotics is a hot issue in environmental chemistry. To overcome this problem, a novel MBene-based adsorbent, DTT@BC@MoBTx, was designed by modification of bacterial cellulose (BC) using MoBTx MBene and 1,4-dithiothreitol (DTT). Several characterization methods, including Fourier transforms infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray Diffraction (XRD), confirmed the successful synthesis of DTT@BC@MoBTx composite. It was discovered that the abundance of functional groups, higher specific surface area, and porosity were facilitative for DTT@BC@MoBTx adsorbents to indomethacin (IDM) and losartan (LP). The adsorption of IDM and LP well fitted to the pseudo-second-order kinetic model and Langmuir isotherm model, suggesting the single-layer chemisorption occurred on the adsorbent. The maximum sorption capabilities of the DTT@BC@MoBTx adsorbent were 1041.26 mg/g for IDM and 887.31 mg/g for LP, indicating excellent adsorption performance. The adsorption capacities of IDM and LP showed a slight decline after four consecutive adsorption-desorption tests, indicating excellent regeneration ability and stability. Interfering monoanionic (Na+ and K+) and monoanionic (Cl- and NO3-) exhibited negligible impacts on IDM and LP elimination rates at all three concentrations. Additionally, it was discovered that metal ions had a greater ability for interference in a higher valency state (Mg2+, Ca2+, SO42-, and CO32-) than in a lower valency state (Na+, K+, Cl-, and NO3-). The adsorption processes of IDM and LP by the DTT@BC@MoBTx adsorbent involved hydrogen bonding and electrostatic attraction, as shown by FTIR and XPS analyses. This work offered a novel MBene-based adsorbent for the quick and effective adsorption of IDM and LP from water.

Analysis of dissolved organic matter characteristics in pharmaceutical wastewater via spectroscopy combined with Fourier-transform ion cyclotron resonance mass spectrometry

Studying the changes in organic matter and characteristic pollutants during the treatment of penicillin-containing pharmaceutical wastewater, which can be reflected by changes in dissolved organic matter (DOM), is crucial for improving the effectiveness of wastewater treatment units and systems. Herein, water quality indicators, spectroscopic methods, and Fourier-transform ion cyclotron resonance mass spectrometry were utilized to characterize the general molecular compositions and specific molecular changes in DOM during the treatment of typical penicillin-containing pharmaceutical wastewater, including in each of the influent, physicochemical treatment, biological treatment, oxidation treatment, and effluent stages. The influent exhibited a high organic matter content (concentration of dissolved organic carbon >10,000 mg·L-1), its DOM mainly contained protein- and lignin-like substances composed of CHON and CHONS molecules, and the relative intensity (RI) of penicillin was extremely high (RI = 0.220). Compared with the influent, the abundance of CHON and CHONS molecules detected after physicochemical treatment decreased by 70.3 % and 62.5 %, respectively, and the RI of penicillin decreased by 85.5 %. Biological treatment caused substantial changes in DOM components through oxidation, dealkylation, and denitrification reactions, accounting for 36.8 %, 28.9 %, and 14.8 % of the total identified reactions, respectively. Additionally, lignin-like substances were generated in large quantities, the overall humification level significantly increased, and the RI value increased for the penicillin intermediate, 6-aminopenicillanic acid (6-APA). Oxidation treatment effectively removed phosphorus-containing substances and some lignin-like substances produced by biological treatment; however, it was not effective in removing characteristic pollutants such as 6-APA. Such characteristic substances continued to be present in the effluent, and the DOM mainly contained protein- and humus-like substances, accounting for 30.8 % and 47.3 %, respectively. The study findings reveal the changes in organic matter and characteristic pollutants during the treatment of penicillin-containing wastewater from the perspective of the general molecular composition and specific molecular changes in DOM, providing support for further exploration of wastewater treatment mechanisms and improvements in treatment unit efficiency.

Electrochemistry promotion of Fe(Ⅲ)/Fe(Ⅱ) cycle for continuous activation of PAA for sludge disintegration: Performance and mechanism

In this study, electrochemistry was used to enhance the advanced oxidation of Fe(Ⅱ)/PAA (EC/Fe(Ⅱ)/PAA) to disintegrate waste activated sludge, and its performance and mechanism was compared with those of EC, PAA, EC/PAA and Fe(Ⅱ)/PAA. Results showed that the EC/Fe(Ⅱ)/PAA process effectively improved sludge disintegration and the concentrations of soluble chemical oxygen demand, polysaccharides and nucleic acids increased by 62.85%, 41.15% and 12.21%, respectively, compared to the Fe(Ⅱ)/PAA process. Mechanism analysis showed that the main active species produced in the EC/Fe(Ⅱ)/PAA process were •OH, R-O• and FeIVO2+. During the reaction process, sludge flocs were disrupted and particle size was reduced by the combined effects of active species oxidation, electrochemical oxidation and PAA oxidation. Furthermore, extracellular polymeric substances (EPS) was degraded, the conversion of TB-EPS to LB-EPS and S-EPS was promoted and the total protein and polysaccharide contents of EPS were increased. After sludge cells were disrupted, intracellular substances were released, causing an increase in nucleic acids, humic acids and fulvic acids in the supernatant, and resulting in sludge reduction. EC effectively accelerated the conversion of Fe(Ⅲ) to Fe(Ⅱ), which was conducive to the activation of PAA, while also enhancing the disintegration of EPS and sludge cells. This study provided an effective approach for the release of organic matter, offering significant benefits in sludge resource utilization.

Exploring the viability of peracetic acid-mediated antibiotic degradation in wastewater through activation with electrogenerated HClO

Electrochemical advanced oxidation processes (EAOPs) face challenging conditions in chloride media, owing to the co-generation of undesirable Cl-disinfection byproducts (Cl-DBPs). Herein, the synergistic activation between in-situ electrogenerated HClO and peracetic acid (PAA)-based reactive species in actual wastewater is discussed. A metal-free graphene-modified graphite felt (graphene/GF) cathode is used for the first time to achieve the electrochemically-mediated activation of PAA. The PAA/Cl- system allowed a near-complete sulfamethoxazole (SMX) degradation (kobs =0.49 min-1) in only 5 min in a model solution, inducing 32.7- and 8.2-fold rise in kobs as compared to single PAA and Cl- systems, respectively. Such enhancement is attributed to the occurrence of 1O2 (25.5 μmol L-1 after 5 min of electrolysis) from the thermodynamically favored reaction between HClO and PAA-based reactive species. The antibiotic degradation in a complex water matrix was further considered. The SMX removal is slightly susceptible to the coexisting natural organic matter, with both the acute cytotoxicity (ACT) and the yield of 12 DBPs decreasing by 29.4 % and 37.3 %, respectively. According to calculations, HClO accumulation and organic Cl-addition reactions are thermodynamically unfavored. This study provides a scenario-oriented paradigm for PAA-based electrochemical treatment technology, being particularly appealing for treating wastewater rich in Cl- ion, which may derive in toxic Cl-DBPs.