Application for oxytetracycline wastewater pretreatment by Fenton iron mud based cathodic-anodic-electrolysis ceramic granular fillers

Non-thermal plasma activated peroxide and percarbonate for tetracycline and oxytetracycline degradation: Synergistic performance, degradation pathways, and toxicity evaluation

Tetracycline (TC) and Oxytetracycline (OTC) are common antibiotics increasingly detected in the environment, posing a potential risk to human and aquatic lives. Although conventional methods such as adsorption and photocatalysis are used for the degradation of TC and OTC, they are inefficient in removal efficiency, energy yield, and toxic byproduct generation. Herein, a falling-film dielectric barrier discharge (DBD) reactor coupled with environmentally friendly oxidants (hydrogen peroxide (HPO), sodium percarbonate (SPC), and HPO + SPC) was applied, and the treatment efficiency of TC and OTC was investigated. Experimental results showed that moderate addition of the HPO and SPC exhibited a synergistic effect (SF > 2), significantly improving the antibiotic removal ratio, total organic removal ratio (TOC), and energy yield by more than 50%, 52%, and 180%, respectively. After 10 min of DBD treatment, the introduction of 0.2 mM SPC led to a 100% antibiotic removal ratio and a TOC removal of 53.4% and 61.2% for 200 mg/L TC and 200 mg/L OTC, respectively. Also, 1 mM HPO dosage led to 100% antibiotic removal ratios after 10 min of DBD treatment and a TOC removal of 62.4% and 71.9% for 200 mg/L TC and 200 mg/L OTC, respectively. However, the DBD + HPO + SPC treatment method had a detrimental effect on the performance of the DBD reactor. After 10 min of DBD plasma discharge, the removal ratios for TC and OTC were 80.8% and 84.1%, respectively, when 0.5 mM HPO +0.5 mM SPC was added. Moreover, principal component and hierarchical cluster analysis confirmed the differences between the treatment methods. Furthermore, the concentration of oxidant-induced in-situ generated ozone and hydrogen peroxide were quantitatively determined, and their indispensable roles during the degradation process were established via radical scavenger tests. Finally, the synergetic antibiotic degradation mechanisms and pathways were proposed, and the toxicities of the intermediate byproducts were evaluated.

Constructing Highly Active Metal Oxides for Toluene Degradation by Fenton Iron Mud Modulation

Fenton iron mud (IM) is a hazardous solid waste produced by Fenton oxidation technology after treating industrial wastewater. Thus, it is necessary and challenging to develop a recycling technology to back-convert dangerous materials into useful products. Herein, we develop a sustainable approach to prepare highly active metal oxides via a solid-state grinding method. IM, as an amorphous material, can disperse and interact well with these supported metal oxides, boosting toluene degradation significantly. Among these IM-based catalysts, the catalyst 8% MnO_x/IM-0.2VC exhibits the best performance (T₁₀₀ = 290 °C), originating from the oxide-support interaction and optimal balance between low-temperature reducibility and oxygen vacancy concentration. In addition, in situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) results expound that ring breakage is prone to occur on MnO_x, and oxygen vacancies are beneficial to adsorb oxygen and activate oxygen species to boost toluene oxidation following the Mars-van Krevelen mechanism. This work advances a complete industrial hazardous waste recycling route to develop extremely active catalysts.

Degradation of tetracycline hydrochloride in aqueous via combined dielectric barrier discharge plasma and Fe-Mn doped AC

Dielectric barrier discharge (DBD) plasma coupled with Fe-Mn doped AC (Fe-Mn/AC) was used to enhance the degradation of tetracycline hydrochloride (TCH) wastewater. Fe-Mn/AC catalysts with different Fe/Mn molar ratios were prepared by hydrothermal method, and the physical and chemical properties of the samples were explored by different characterization techniques, including XRD, SEM, TEM and XPS. The results showed that the combination of DBD with Fe₂-Mn₁/AC system had the highest effect, and the degradation efficiency of TCH could reach 98.8 % after 15 min treatment, which was 25.5 % higher than that of DBD-only. With the increase of discharge voltage and catalyst dosage, the degradation efficiency of TCH promoted. And initial pH had little effect on the degradation of TCH. In the combined system, the Fe₂-Mn₁/AC catalyst could retain an excellent stability and reusability. The addition of dimethyl sulfoxide (DMSO) showed that ·OH participated in the TCH degradation. The generated O₃ might be catalyzed by Fe-Mn/AC catalyst to produce more ·OH. And more H₂O₂ was produced in DBD-only system than that in DBD-catalytic system. Nine main degradation intermediate products in the combined system were detected by HPLC-MS, and three possible degradation pathways were proposed.

Fabrication, characterizations and performance of a high-efficiency micro-electrolysis filler for isobutyl xanthate (IBX) degradation

Micro-electrolysis is a cost-effective method widely applied in wastewater treatment. In this paper, a high-efficiency micro-electrolysis filler was prepared by a facile calcination method for the degradation of isobutyl xanthate (IBX). The optimization of filler fabrication process was investigated from aspects of compressive strength, abrasion loss and degradation rate. Combined with multi-characterization techniques, it can be found that the zero-valent iron (ZVI) was partially changed to Fe(2+) in the phase of fayalite (Fe₂SiO₄) during the treatment. The influence of operation parameters of filler dosage, initial pH and initial concentration were thoroughly studied. The result shows that the IBX degradation rate by optimized filler can reach 93.30%, superior to that of Fe/C filler (the element Fe kept at ZVI during heat treatment) with 61.8% removal. The degradation pathway of IBX was studied by GC-MS in details and the bis(2-methylpropyl)carbonate was postulated as the main by-product. The stability of filler was evaluated by batch cycle tests and column tests. This work provides a novel perspective about micro-electrolysis filler preparation. The extraordinary performance brings it potential for industrial application.

Simultaneous degradation of p-arsanilic acid and inorganic arsenic removal using M-rGO/PS Fenton-like system under neutral conditions

In this study, magnetic material based reduced graphene oxide (M-rGO) was prepared through co-precipitation and displayed high catalytic efficiency together with persulfate (PS) for simultaneous p-arsanilic acid (p-ASA) decomposition and arsenic removal. Linear sweep voltammetry and chronoamperometric measurements with M-rGO revealed that PS was effectively bound to M-rGO surface and probably formed charge transfer complex, in which M-rGO was pivotal in mediating facile electron transfer. The effects of pH, temperatures, anions, p-ASA concentration, PS, and M-rGO dosages on p-ASA decomposition were studied in the system. Excellent degradation of p-ASA was carried out at a wide range of pH values, which was unattainable by other Fenton-like processes. Under optimal conditions, M-rGO exhibited prominent removal of both p-ASA (98.8 %) and inorganic arsenic (89.8 %). M-rGO had reasonably excellent repeatability and stability, and 77.7 % p-ASA degraded in the third recovered catalyst. The advantages of environmental friendliness, short reaction time, and straightforward synthesis of M-rGO will facilitate the development of heterogeneous Fenton-like catalysts under neutral conditions.

Removal of tetracyclines from aqueous solutions by electrocoagulation/pecan nutshell coupling processes: synergistic effect and mechanism

The present work compared electrocoagulation (EC)/pecan shell (PS) coupling process with a simple electrocoagulation (EC) process for the removal of tetracyclines (TCs). The results indicated that the addition of appropriate PS could lead to the enhancement of the removal efficiency and decrease of operating time via synergistic influence, including conventional EC process, biomass materials adsorption, charge neutralization and coordination adsorption. The ideal condition for the coupling process was 2.5 mA/cm² for current density and 3 cm for plate spacing. Based on the optimum condition, when the dosage of PS was 5 g/L, the initial concentration of tetracycline hydrochloride (TC), oxytetracycline hydrochloride (OTC) and chlortetracycline hydrochloride (CTC) was 250 mg/L, the removal rate of PS was 55.90%, 45.10% and 14.98% higher than those of EC process after 40 min treatment. In addition, compared to conventional EC process, the unit energy demand (UED) decreased by 49.62%, 53.2 4% and 26.35% and the unit electrode material demand (UEMD) decreased by 49.80%, 85.65% and 44.37%, respectively, which means more energy conservation and environmental protection.

Adsorption of oxytetracycline on kaolinite

As antibiotic contamination increases in wastewater and aqueous environments, the reduction of antibiotics has become a pertinent topic of research regarding water treatment. Clay minerals, such as smectite or kaolinite, are important adsorbents used in water treatment, and sufficient removal of antibiotics by clay minerals is expected. In this study, the adsorption of oxytetracycline (OTC) on kaolinite was investigated. The experimental data of OTC adsorption on kaolinite fit the pseudo-second-order kinetics model well (R2>0.98). After 24 h, adsorption equilibrium of OTC on kaolinite was reached. The Langmuir model was better fitting with the adsorption isotherms generated from experimental data and OTC adsorption occurred on the external surface of kaolinite. The analysis of several thermodynamic parameters indicated that the adsorption of OTC on kaolinite was spontaneous and thermodynamically favorable. With the increase of the pH of a solution, the adsorption capacity increased and then decreased. The adsorption coefficient (Kd) of 102-103 were obtained for adsorption process of OTC on kaolinite.

Continuous flow electrosorption-microbial fuel cell system for efficient removal of oxytetracycline without external electrical supply

The removal of antibiotics from wastewater has attracted much attention. In this research, an intimately coupled autarkical electrosorption (ES)-microbial fuel cell (MFC) system was developed for real-time removal of the antibiotic oxytetracycline (OTC) from wastewater. The removal efficiency was founded to be up to 98.8% at an OTC concentration of 2 mg/L with 3 g/L sodium acetate (NaAC) as co-substrate and 3 MFCs as power supply. The removal efficiencies increased in the ES unit and decreased in the MFC unit with increasing treating time. The adsorption of OTC on activated carbon fibers (ACFs) in the ES unit proceeds via chemical adsorption resulting from electrostatic attraction and cation exchange. The OTC degradation pathways in the MFC unit were proposed by identifying the intermediates with HPLC-MS/MS. The ACFs in the ES unit were proven to be recyclable and the coupled ES-MFC system is applicable for the removal of antibiotics from wastewater.

Influence of the root plaque formation with different species on oxytetracycline accumulation in rice (Oryza sativa L.) and its elimination in culture solution

Hydroponic experiments were conducted to investigate the role of different root plaque formation on oxytetracycline (OTC) uptake/translocation by rice seedlings (Oryza sativa L.) and solution-OTC elimination at two initial OTC concentrations (10 and 30 mg L^-1). The results indicated OTC accumulation in rice was always in the order root surface > shoot > inside root whether plaques were formed or not. It demonstrated that Fe-Mn-Mt (montmorillonite) treatment was easier to promote significantly (p < 0.05) OTC accumulation in the underground part (root surface and inside root) and decrease significantly (p < 0.05) OTC translocation from the root to the shoot in rice compared to no plaque treatments (CK), especially for OTC 30 mg L^-1 level with the lowest shoot-OTC accumulation in Fe-Mn-Mt treatment. Plaque treatments increased half-life of solution-OTC elimination in the order Fe-Mn-Mt > Fe-Mn > Fe > CK, which was caused mainly by OTC degradation from Fe²⁺-binding influence in solution, not by the enhancement of OTC accumulation on the root surface and inside root. And solution-OTC elimination increased with decreasing initial OTC concentrations, the drop of Fe²⁺ and the increment of Fe³⁺ and pH during the experiment. These findings are useful for reducing OTC accumulation and translocation in rice aboveground parts and eliminating OTC contamination in agricultural environment simultaneously through complicated plaque formation under higher OTC concentration exposure (30 mg L^-1) in the future design.

Application for oxytetracycline wastewater pretreatment by Fe-C-Ni catalytic cathodic-anodic-electrolysis granular fillers from rare-earth tailings

Fe-C-Ni catalytic cathodic-anodic-electrolysis granular fillers (REGF) coupled with a reactor was studied for oxytetracycline (OTC) wastewater pretreatment. In this study, the REGF were manufactured from the rare-earth tailing (RET), powdered activated carbon (PAC), scrap iron and nickel by balling and calcining. The REGF was characterized by X-Ray Diffraction and Scanning Electron Microscope analysis. The influences of pH value (2-7), OTC concentrations, hydraulic retention time and aeration on the removal efficiency of OTC and total organic carbon (TOC) were studied. This system had good removal efficiency of TOC of 80.0% and OTC of 98.2% under the optimal conditions, which were influent pH of 3, aeration rate of 0 mg L^-1, and HRT of 3 h. After running for 50 d, the REGF did not become hardened and the ability of reaction was more lasting. The system was back-washed by acid solution (pH = 1) in the 25th day. The removal mechanisms were electrophoresis, redox and flocculation. The nickel, which was as the catalyst, was added into REGF to enhance the reduction of pollution with the absorbed atomic hydrogen. This paper provides a way for the recycle of the rare earth tailings and an effective application for wastewater.

Evaluation of antibiotic oxytetracycline removal in water using a gas phase dielectric barrier discharge plasma

Degradation of oxytetracycline (OTC), a primary member of antibiotics in water, was performed by a gas phase dielectric barrier discharge (GPDBD) plasma reactor. The influences of operation conditions including applied voltages, air bubbling rates, initial OTC concentrations and initial pH values on OTC abatement were investigated respectively. The results showed that the decontamination process can be fitted by first order kinetics, and the removal ratio and rate were affected obviously by those parameters. After 20 min of discharge treatment, approximately 93.4% of OTC was removed under the experimental conditions: applied voltage of 7.5 kV, air flow rate of 1.0 L/min, initial OTC concentration of 100 mg/L, and initial pH of 5.0. In addition, TOC and COD removal efficiency reached 43.0% and 73.7% at the original pH 9.3, respectively. Furthermore, the amounts of hydrogen peroxide and ozone in aqueous were quantitatively measured to evaluate their roles during antibiotic removal, and the main function of hydroxyl radicals was demonstrated by the radicals scavenger test. At last, the analyses of UV-Vis spectra and HPLC-MS were employed to study the OTC elimination mechanism, and the possible decomposition pathway was proposed based on the speculated intermediates.

Pretreatment technologies for industrial effluents: Critical review on bioenergy production and environmental concerns

The implementation of different pretreatment techniques and technologies prior to effluent discharge is a direct result of the inefficiency of several existing wastewater treatment methods. A majority of the industrial sectors have known to cause severe negative effects on the environment. The five major polluting industries are the paper and pulp mills, coal manufacturing facilities, petrochemical, textile and the pharmaceutical sectors. Pretreatment methods have been widely used in order to lower the toxicity levels of effluents and comply with environmental standards. In this review, the possible environmental benefits and concerns of adopting different pretreatment technologies for renewable energy production and product/resource recovery has been reviewed and discussed.

Sulfur-doped CoFe2O4 nanopowders for enhanced visible-light photocatalytic activity and magnetic properties

Magnetic recovery S-CoFe₂O₄ nanopowders showed excellent visible photocatalytic degradation of oxytetracycline and recycling performances in aqueous solution.