Treatment Of Organic Pollutants Research Articles

Review of the recent advances on the fabrication, modification and application of electrospun TiO2 and ZnO nanofibers for the treatment of organic pollutants in wastewater

The heightened occurrence of emerging organic pollutants (EOPs) in aquatic bodies has been the subject of global apprehension due to the toxicity they pose to the environment, humans and animals alike. The presence of EOPs has soared due to industrialization and is further exacerbated by human activities like the overuse and poor disposal of dyes, pesticides, pharmaceuticals, surfactants, personal care products and food additives. The complete treatment and removal of EOPs from industrial wastewater and sewage has remained a challenge because of their pseudo-persistence and resistance to degradation. Due to their impressive light absorption properties, high surface-area-to-volume ratio, high porosity, superior mechanical strength, electrospun titanium dioxide (TiO2) and zinc oxide (ZnO) nanofibers have been proposed for the photocatalytic treatment of EOPs. Therefore, this review first highlights the fabrication and modification methods of TiO2 and ZnO nanofibers. A systematic survey of the latest progress in the application of TiO2 and ZnO nanofibers for the degradation of EOPs is then elaborated. Thus, the main goal is to shed light and give insight to researchers on the possibilities surrounding the elimination of EOPs by applying electrospun TiO2 and ZnO semiconductor materials. In addition, the loopholes associated with fabrication and modification processes are discussed with the aim of encouraging innovation for prospective technology advancement and commercialization, as well as to enhance research efforts in wastewater treatment and environmental sustainability.

Magnetic perovskite nanohybrid based on g-C3N4 nanosheets for photodegradation of toxic environmental pollutants under short-time visible irradiation

In this study, a magnetic perovskite nanohybrid based on g-C3N4 (gCN) nanosheets was synthesized and developed for the efficient photodegradation of toxic environmental pollutants under short-time visible irradiation. The synthesis of this nanohybrid involved the incorporation of SrTiO3:N (STO:N) and ZnFe2O4 (ZnF) onto the g-C3N4 nanosheets through a simple reflux method. Our investigation encompassed a comprehensive suite of analytical techniques, including BET, TGA, TEM, SEM, EDX, DRS, VSM, XRD, photocurrent, and FT-IR, to elucidate the physicochemical characteristics of this nanocomposite in the context of its application in photodegradation processes. The nanohybrid displayed significantly enhanced photocatalytic activity compared to its individual components, achieving a degradation efficiency of over 90% for various pollutants, including organic dyes like Rhodamine B (Rh-B), within a short irradiation time. This enhanced activity can be attributed to the synergistic effect between gCN, STO:N, and ZnF, which promotes the generation of reactive oxygen species and facilitates the degradation process. Notably, the nanocomposite containing 20 wt% STO:N perovskite and 20 wt% ZnF demonstrated the highest Rh-B degradation rate under visible light irradiation within just 30 min. Furthermore, the nanohybrid displayed excellent stability and reusability over seven consecutive runs, retaining its high photocatalytic activity even after multiple cycles of degradation. This remarkable performance can be attributed to the strong interaction between the gCN nanosheets and the magnetic perovskite components, which prevents their aggregation and ensures their efficient utilization. Additionally, the nanohybrid exhibited excellent visible light absorption, enabling the utilization of a wider range of light for degradation. This feature is particularly advantageous, as visible light is more abundant in sunlight compared to UV light, rendering the nanohybrid suitable for practical applications under natural sunlight. In conclusion, the ternary gCN-STO:N@ZnF nanocomposite represents a promising candidate for the treatment of organic pollutants in aqueous environments, offering a versatile and efficient solution.

Enhanced activation of PMS by a novel MnFe2O4@N-PC-GM composite for rapid 1-naphthol degradation: Formation and mechanism of singlet oxygen

A novel magnetic catalyst, MnFe2O4 functionalized N-doped porous carbon/geopolymer (MnFe2O4 @N-PC-GM) composite, was synthesized using pine cones and geopolymer as precursors for efficient and sustainable removal of 1-naphthol. Experimental results indicated that MnFe2O4 particles were distributed in in the structure of N-PC-GM carrier, greatly increasing the number of active sites. The removal ratio of 1-naphthol was up to 86.06% in MnFe2O4 @N-PC-GM/PMS system, and the degradation process followed pseudo-second-order kinetics (R2 = 0.996). Quenching experiments and EPR analysis validated that 1-naphthol was degraded in MnFe2O4 @N-PC-GM/PMS system mainly through a non-radical oxidation pathway dominated by 1O2. X-ray photoelectron spectroscopy (XPS) and degradation experiments in different gas atmosphere demonstrated that the sources of 1O2 were closely related to the existence of oxygen vacancies (OVs), the conversion of dissolved oxygen as well as the introduction of active sites (N, Mn and Fe). Furthermore, the good degradation rate of 1-naphthol in real water confirmed the feasibility of MnFe2O4 @N-PC-GM/PMS system in practical application. This work provided a new strategy for the treatment of persistent organic pollutants in water.

Degradation of residual xanthate in flotation tailing wastewater by activated H2O2 with natural ilmenite: A heterogeneous fenton-like reaction catalyzed at natural pH

Efficient treatment of residual xanthate from tailing wastewater has attracted soaring interesting recently. Herein, effect of activated H2O2 by natural ilmenite (FeTiO3) as a catalyst on sodium butyl xanthate (SBX) degradation was systematically investigated. More than 98 % SBX degradation efficiency was achieved by the method under optimal conditions (a natural pH = 8.7, [FeTiO3]0 = 4.0 g/L, [H2O2]0 = 2.0 mM, and [SBX]0 = 40.0 mg/L), and chemical oxygen demand (COD) removal rate was 85.41 %. Kinetic studies indicated that SBX degradation efficiency in FeTiO3-H2O2 system conformed with a pseudo first order kinetic equation. Also, comparative experiments indicated that this system degraded SBX was superior to the H2O2 alone and FeTiO3 alone systems. Reactive oxygen species (ROS) were determined by quenching experiments and electron paramagnetic resonance (EPR) tests, suggesting that OH and O2− were the primary reactive radicals in FeTiO3-H2O2 system. Cycling experiments and leaching metal ion tests suggested that FeTiO3 still exhibited high catalytic activity and excellent stability after five times of recycling. Finally, possible degradation pathways and mechanism of SBX in this system were proposed. Consequently, this study promotes the application of natural iron-based minerals as a catalyst in wastewater treatment, and provides new insights into the effective treatment of organic pollutants in tailing wastewater.

Effective photoelectrocatalysis of levofloxacin antibiotic with Ti/IrO2[sbnd]Nb2O5 in environmental samples

This work reports the development and application of a highly efficient catalyst based on IrO2 and Nb2O5 for the degradation of the antibiotic Levofloxacin (LFX) in simulated and real surface water samples. The IrO2Nb2O5 films, which were obtained by modified Pechini method, were deposited on a titanium substrate, leading to the production of Ti/IrO2Nb2O5 electrode. After being subjected to morphological, structural and electrochemical characterization, the Ti/IrO2Nb2O5 electrode was applied for the degradation of LFX using different processes, including electrolysis (EC) and photoelectrolysis (PhEC), and the results obtained were compared to that of UV–Vis irradiation-based photolysis. The application of the PhEC process led to a relatively higher and faster removal of LFX in the water matrices investigated, where 100% degradation rate and about 70% mineralization rate were obtained at the end of 1.5 h of treatment, compared to the individual photolysis and EC processes. The results obtained from quenching tests showed that LFX degradation under the PhEC process may be associated with the presence of active radicals, such as HO•, SO4•− and O2•−, in addition to the e−/h+ pair formed with the incidence of light during treatment. Apart from excellent photoelectrocatalytic activity and high stability, the Ti/IrO2Nb2O5 electrode exhibited high electrochemically active surface area (ECSA). The excellent results obtained from the application of the PhEC process in terms of TOC removal and the remarkable catalytic properties of Ti/IrO2Nb2O5 point to the high efficiency of the system proposed in this study when applied for the treatment and removal of organic pollutants from real water samples.

Engineered nanoconfinement activates Fenton catalyst at neutral pH: Mechanism and kinetics study

We proposed to establish nanoscale spatially confined Fenton treatment architectures to overcome the catalyst deactivation issue frequently seen at neutral pH. We demonstrated this idea by growing four typical iron oxide catalysts (Fe3O4, FeOOH, CuFe2O4, and FeOCl), respectively inside the nanochannels of anodized aluminum oxide scaffold, wherein the confined space (≈5 nm) significantly accelerated heterogeneous Fenton treatment of organic pollutants, with up to 310 times kinetics enhancement under normalized surface area compared to the counterpart bulk reactions with suspension catalysts. Based on experimental and computational studies, we gained the mechanistic details on how did the nanoconfinement enhanced the protonation of surfaces driving the catalysis, and showed how much of its significance over other influencing factors on enhancing the treatment kinetics and a sustained catalysis. Our findings mark an important advance on developing nanoconfined Fenton treatment systems that enable efficient catalyst activation and maximal treatment kinetics, without additional chemicals or electro-/photo-energies.

Hydroxylamine promoted degradation of organic contaminants using peroxydisulfate activated by Fe-alginate

ABSTRACT To overcome the shortcomings of Fe(Ⅱ)/peroxydisulfate (PDS) system including the limited working pH range and large iron sludge production, a Fe-doped alginate (Fe-Alg) catalyst was prepared and combined with hydroxylamine (HA) to continuously activate PDS for the removal of organic pollutants in neutral condition. Due to the strong reductive capability of HA, it could significantly enhance the catalytic capability of Fe-Alg for PDS. The results of characterization suggested that Fe(Ⅲ)/Fe(Ⅱ) was evenly distributed in Alg through its complexation with carboxyl groups, and the reduction of Fe(Ⅲ) to Fe(Ⅱ) initiated by HA enabled Orange G (OG) to be continuously degraded in the Fe-Alg/HA/PDS system. The results of quenching experiments suggested that S O 4 ∙ − and HO• played a dominant role for OG removal in the Fe-Alg/HA/PDS process. The effect of influence factors (e.g. initial pH, HA concentration, Fe-Alg dose and PDS concentration) and water matrix components (i.e. S O 4 2 − , N O 3 − , Cl–, HC O 3 − and dissolved organic matters (DOM)) on the performance of Fe-Alg/HA/PDS system was systematically investigated. Other refractory organic contaminants, including diclofenac (DCF), sulfamethoxazole (SMX), oxytetracycline (OTC) and bisphenol AF (BPAF) were also efficiently eliminated in Fe-Alg/HA/PDS system, suggesting the feasibility of this system for the treatment of organic pollutants. This work provides a method to optimize Fe(Ⅱ)/PDS system and a novel process applied to degrade refractory pollutants.

In situ co-crystallization synthesis of the direct Z-scheme Bi5O7I/Bi2SiO5 heterojunction for enhanced photocatalytic rhodamine B and ciprofloxacin degradation

Semiconductor photocatalysis has driven considerable interests for its desirable potential to tackle the worldwide energy shortage and environmental pollution. In this paper, a novel Bi5O7I/Bi2SiO5 Z-scheme heterojunction photocatalyst was in situ synthesized via a co-crystallization process and partial anion exchange strategy. The XRD and FT-IR pattern validated the successful preparation of the heterojunction. The optimal Bi5O7I/Bi2SiO5 heterojunction displayed an excellent photocatalytic activity towards the ciprofloxacin under the simulated solar light, and the rate constant (0.46021 h−1) was 2 and 7.8 times higher than that of pure BiOI (0.22967 h−1) and Bi2SiO5 (0.05877 h−1). Similarly, the degradation efficiency on rhodamine B (RhB) reached 94%, which was much higher than that of the single photocatalysis. The enhanced photocatalytic performance of the heterojunction photocatalyst could be attributed to the formation of the direct Z-scheme heterojunction between the Bi5O7I and Bi2SiO5, which was favorable for retarding the recombination of photoinduced electron-hole pairs. Moreover, the bacteriostatic activity testing illustrated the toxicity of drug solutions decreased sharply after the photocatalytic degradation with the Bi5O7I/Bi2SiO5-3. The ESR characterization analysis and the free radical trapping experiments synergistically determined the Z-scheme electron transfer path of the heterojunction. The possible photocatalytic mechanism of Bi5O7I/Bi2SiO5 heterojunction was proposed. Overall, the well-designed Bi5O7I/Bi2SiO5 heterojunction depicted great practical promise in efficient treatment of organic pollutants.

Peroxyacetic acid activation by cobalt-doped peanut shell biochar for efficient CBZ degradation: Role of organic radicals, singlet oxygen, and high-valent cobalt species

Peroxyacetic acid (PAA) oxidant has a broad application prospect to be combined with biochar in the treatment of organic pollutants due to its excellent characteristics of eco-friendly and easy activation. In this study, peanut shell biochar-loaded Co nanoparticles (Co-BC-850) catalysts were prepared through pyrolysis to activate PAA for carbamazepine (CBZ) degradation. The pyrolysis temperature significantly affected the CBZ degradation efficiency of the catalysts. The experimental results revealed that the Co-BC-850 catalyst exhibited the highest CBZ degradation efficiency. Within 20 min, a CBZ degradation rate of 99.9% was achieved with Co-BC-850 concentration of 50 mg/L and PAA concentration of 1 mM. The Co-BC-850/PAA system achieved high degradation performance for CBZ at a pH ranging from 5.0 to 9.0, even in the presence of inorganic anions. The analysis of the Co-BC-850/PAA system revealed a complex interplay of reactive species (RSs). Organic radicals (R-O•), singlet oxygen (1O2), and high-valent cobalt species (Co(IV)) collaboratively contributed to CBZ degradation. These findings revealed the intricate mechanism of CBZ degradation via Co-BC-850-activated PAA, thereby elucidating potential degradation pathways. This study demonstrates the promising application of biochar PAA-based AOPs and offers a sustainable and effective solution for the degradation of CBZ and other potential pharmaceutical compounds in water.

Perovskite Type B-CaTiO3 Coupled with Graphene Oxide as Efficient Bifunctional Composites for Environmental Remediation

To prepare boron doped perovskite CaTiO3 nanocubes coupled with graphene oxide (B-CaTiO3/GO), B-CaTiO3 photocatalyst was initially synthesized by the solvothermal method and subsequently attached on GO by a simple hydrothermal process. The phase structure and optical features of the prepared materials were efficiently characterized by several techniques. The XRD patterns indicated that boron doping could not give rise to lattice disruption of CaTiO3. The results of XPS, HRTEM and Raman measurements revealed that the presence of B-CaTiO3 is anchored on the surface of GO effectively. The morphology of the B-CaTiO3/5GO was nanocube particles. The photocatalytic capacity of B-CaTiO3/GO nanocomposites was determined by investigating the degradation of a model dye, methylene blue (MB). Their degradation performance could be enhanced by altering the ratio between B-CaTiO3 and GO. The most effective GO incorporation is 5 wt%, and at this loading percentage, B-CaTiO3/GO nanocomposite showed improved photocatalytic activity compared with CaTiO3 and B-CaTiO3 photocatalyst, which could be attributed to the synergistic efficacy of the adsorbed MB molecule on the GO followed by their degradation after 180 min of visible light. Additionally, the active species trapping tests confirm the dominant role performed by ·OH and O2·− during the degradation of MB. The presence of HCO3− and Cl− indicated moderate prohibitive effect on the degradation of MB, while NO3− and SO42− negatively affected the catalytic activity in a non-significant way. In brief, the results of this study show that boron doped perovskite-type semiconductor catalysts by combining with graphene has significant efficiency in the removal of MB from aqueous solution, which can be employed as effective photocatalyst materials for the treatment of other organic pollutants.

NiFe LDH/MoS2/Ni3S2 p-n/Mott-Schottky heterojunction for efficient hydrogen generation coupled with electrochemical oxidation of organic molecules

Urea and organic molecules assisted electrochemical water splitting is a promising strategy to realize energy-saving hydrogen production and simultaneous treatment of wastewater containing urea and organic pollutants. It is an effective approach to develop advanced electrocatalysts being of excellent catalytic performance by constructing a metal-semiconductor or semiconductor-semiconductor heterogeneous interface to regulate the electronic structure, thus forming the highly catalytic sites. Herein, we prepared a NiFe LDH/MoS2/Ni3S2 ternary heterojunction as a bifunctional catalyst on nickel foam (NiFe LDH/MoS2/Ni3S2/NF) via constructing Schottky interface and p-n heterojunction interface. In view of the built-in electric field between the heterogeneous interfaces, the electron transfer in interfaces is accelerated, and the adsorption of OH- and the dissociation of urea are also promoted, which results in excellent electrocatalytic performance including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), urea oxidation reaction (UOR) and ethanol oxidation reaction (ETOR). At 50 mA cm−2, the voltages of HER, OER, UOR and ETOR are −0.100, 1.511, 1.410, 1.427 V vs. RHE, respectively, better than the most of reported electrocatalysts. In two-electrode electrolytic cells using NiFe LDH/MoS2/Ni3S2/NF as cathode and anode catalysts, this material also exhibits the outstanding catalytic performance in electrolytes of 1.0 M KOH, 1.0 M KOH containing 0.5 M urea and 1.0 M KOH containing 0.5 M lactic acid. This research provides a feasible approach for constructing advanced electrocatalysts by combining the different metal-based compounds to form the heterojunction with highly catalytic sites, thus realizing the aim of acquiring hydrogen energy and simultaneous treatment of urea wastewater and other organic pollutants.

Electrocoagulation technique and statistical analysis for treatment of real effluent from the pulp and paper industry

The electrochemical treatment of Organic Pollutants is a promising technique for substances with biodegradability resistance. In this research, the black liquor effluent originating from the Rakta Paper and Paper Company's mill, which employs rice straw as a raw material for paper fiber production, was subjected to treatment using the electrocoagulation method utilizing monopolar aluminum electrodes. The experiments were carried out using a 2.5 L electrochemical cell equipped with monopolar aluminum electrodes connected in parallel. The study examined the impact of operating parameters such as initial pH, current density, number of plates and electrolyte concentration on percentage removal and power consumption. The results revealed a positive correlation between the percentage of color removal and the duration of electrolysis, current density, sodium chloride concentration, and the number of electrodes used. The maximum color removal was observed at initial solution pH 6.5, experimental time 120 min, current density 61.8 A m−2, initial NaCl solution concentration 2 g L−1 and six aluminum plates. The statistical and mathematical data based on experimental results were analyzed using the central composite design from response surface methodology (RSM). The quadratic model is deemed appropriate owing to its substantial coefficient of determination (R2 = 0.99) and statistically significant p-value (≤ 0.0002), suggesting the model's significance. The experimental results indicate that the utilization of electrocoagulation as a treatment method for paper mill effluents has demonstrated superior efficacy compared to the adsorption technique.

Recyclable magnetic AgBr/BiOBr/Fe3O4 photocatalytic activation peroxymonosulfate for carbamazepine degradation: Synergistic effect and mechanism

In order to effectively curb the various hazards posed by carbamazepine (CBZ) to aquatic ecosystems, a recyclable magnetic AgBr/BiOBr/Fe3O4 composite photocatalytic material was successfully synthesized in this study. When the content of Fe3O4 was 5 wt% (ABF-5), the ABF-5/Vis/PMS system was formed under peroxymonosulfate (PMS) and visible light (Vis). The system was able to degrade 96.84 % of CBZ within 30 min, with good photocatalytic synergy and degradation effect. Meanwhile, the system also showed a satisfactory degradation effect on CBZ in real water bodies such as reservoir water and hospital wastewater. In the ABF-5/Vis/PMS system, CBZ was degraded mainly by cleavage, hydroxylation, oxidation, and decarboxylation, and the active substances such as 1O2, O2−, h+ played a major role in the degradation process. After five cycles of experiments, the degradation efficiency of CBZ remained above 85 %. Moreover, ABF-5 can be quickly separated and easily reused under an external magnetic field with good stability. In summary, the recoverable magnetic ABF-5 has good potential for practical application and could provide novel perspectives methods, and ideas for the treatment of persistent organic pollutants treatment in water ecosystems.

Study on the Effect of AO-Coupled Constructed Wetlands on Conventional and Trace Organic Pollutant Treatment.

In this study, a pilot-scale integrated process was developed, which combined the integrated biological contact oxidation technology (AO) and the improved constructed wetland technology. The results showed significant removal efficiency for both conventional and trace organic pollutants. The average removal efficiencies for COD, NH4+-N, and TP were 78.52, 85.95, and 49.47%, respectively. For trace organic pollutants, triclocarban, triclosan, and sulfadiazine, the removal efficiencies reached 60.14, 57.42, and 84.29%, respectively. The AO stage played a crucial role in removing trace organic pollutants, achieving removal efficiencies of 37.28, 43.44, and 83.82% for triclocarban, triclosan, and sulfadiazine, respectively. Subsequent treatment using improved constructed wetland technology with coal slag + gravel fillers demonstrated the highest removal efficiency, with average efficiencies of 68.66, 63.38, and 81.32% for triclocarban, triclosan, and sulfadiazine, respectively. Correlation analysis revealed positive correlations between temperature, precipitation, and the removal efficiency of COD, NH4+-N, and TP, while negative correlations were observed with the removal efficiency of triclocarban, triclosan, and sulfadiazine. Furthermore, the influent concentrations of triclocarban and triclosan were significantly negatively correlated with the removal efficiency of COD and TP. The presence of triclocarban and triclosan potentially reduced the microbial diversity and hindered sludge sedimentation performance.

Simultaneous adsorption and biodegradation of oxytetracycline in wastewater by Mycolicibacterium sp. immobilized on magnetic biochar

Due to the adverse effects of long-term oxytetracycline (OTC) residues in aquatic environments, an effective treatment is urgently needed. Immobilized microbial technology has been widely explored in the treatment of various organic pollutants in aquatic environments with its excellent environmental adaptability. Nevertheless, studies on its application in the removal of antibiotics are relatively scarce and not in sufficient depth. Only a few studies have further investigated the final fate of antibiotics in the immobilized bacteria system. In this study, a novel kind of OTC-degrading bacteria Mycolicibacterium sp. was immobilized on straw biochar and magnetic biochar, respectively. Magnetic biochar was proved to be a more satisfactory immobilization carrier due to its superior property and the advantage of easy recycling. Compared with free bacteria, immobilized bacteria had stronger environmental adaptability under different OTC concentrations, pH, and heavy metal ions. After 5 cycles, immobilized bacteria could still remove 71.8% of OTC, indicating that it had a stable recyclability. Besides, OTC in real swine wastewater was completely removed by immobilized bacteria within 2 days. The results of FTIR showed that bacteria were successfully immobilized on biochar and O–H, N–H, and C–N groups might be involved in the removal of OTC. The fate analysis indicated that OTC was removed by simultaneous adsorption and biodegradation, while biodegradation (92.8%) played a dominant role in the immobilized bacteria system. Meanwhile, the amount of adsorbed OTC (7.20%) was rather small, which could effectively decrease the secondary pollution of OTC. At last, new degradation pathways of OTC were proposed. This study provides an eco-friendly and effective approach to remedy OTC pollution in wastewater.

Enhanced degradation of methionine by eco-friendly and low-cost tannin extract modified Fenton oxidation: Promotion of the Fe(III)/Fe(II) cycle

In this study, a low-cost natural biomass extracted from higher plants - Tannin - was used to improve the Fenton system by promoting iron cycling due to the abundant phenolic hydroxyl groups in the molecular structure. Tannin extract (TE) of black wattle was combined with Fe(Ⅱ)/H2O2 system at room temperature and under pH 3 to 8. Methionine (Met) was chosen as a target pollutant, as its critical role in the global sulfur cycle and algae-induced black bloom events. The results found that TE could significantly promote Fe(Ⅱ)/H2O2 system, Met degradation increased from 44 % to 86 % under pH 6.0, and the mineralization increased from 14.86 % to 38.96 %. Both quenching experiments and electron paramagnetic resonance (EPR) analysis confirmed that OH and O2− contributed to Met degradation, and OH played a key role in TE/Fe(Ⅱ)/H2O2 system. The reducibility of TE at different pH values was evaluated, the highest Fe(Ⅲ) reducing rate of TE was obtained at pH of 4.5 (k = 22.48 M−1min−1) based on the formation model. TE and its complex catalyzed the dismutation of O2− to form OH. The degradation rate constant of TE/Fe(Ⅱ)/H2O2 system was 3.63 min−1, and the intermediates of Met degradation was proved to be non-toxic. In conclusion, TE could facilitate the iron recycle in Fenton system, consequently to strengthen H2O2 activation, and it offered an energy-saving and eco-friendly way for organic pollutants treatment.

Efficient multi-stage electrochemical flow-through system for refractory organic pollutant treatment: Kinetics, mass transfer, and thermodynamic analysis

Improving the kinetics rate and mass transfer is essential for expanding the potential of electrochemical technologies in wastewater treatment. The electrochemical flow-through configuration promises a high oxidation efficiency and low energy consumption. We aimed to provide a thorough understanding of the enhanced kinetics, mass transfer, and thermodynamic parameters during the degradation of amoxicillin (AMX) in a multi-stage flow-through (MSFT) system using porous Ti-ENTA/SnO2–Sb anodes. All operating conditions strongly influenced the kinetics of AMX degradation and followed pseudo-first-order rate kinetic model (R2 > 0.85), with the highest kobs of 0.228 min−1 at high temperature (318 K).In comparison to the flow-by mode, the AMX removal rate in the three-stage flow-through mode was greatly enhanced by 70%, exhibiting the superior capacity of a porous anode. This system exhibited outstanding performance regarding the high kinetics rate and mass transfer rate (km), which increased by factors of 3.46 and 10.74, respectively, obtained in the flow-by mode. It also revealed that •OH generation was 5.64 times higher, and the EE/O was 19.89-fold lower than those in flow-by mode. Temperature plays a vital role in the reaction process, and thermodynamic features found the positive enthalpy (ΔHo) of +27.06 kJ mol−1, signifying the process was endothermic. A Hatta number (Ha) of >0.02 at all temperatures proved this finding, confirming an undeniable role in mass transfer. Finally, these findings reveal the system's performance and offer the possibility of establishing a multi-stage flow-through for wastewater treatment.

Investigating the Potential of Greener-Porous Graphene for the Treatment of Organic Pollutants in Wastewater

Pharmaceuticals have emerged as a new class of ecological pollutants and have majorly contributed to harmful effects on the environment and human health. The presence of these pharmaceuticals in wastewater treatment plants, ground, and seawater has been reported widely. Organic dyes and other organic contaminants which are being considered as emerging contaminants are now in the race among the top organic pollutants that need effective treatment. Removal of these contaminants via green adsorbents has become an essential requirement towards a green and cleaner environment. Herein, we report the efficacy of the novel greener porous graphene obtained via the near-green synthesis method as an adsorbent material for treating seven organic pollutants: Methyl orange, Methyl red, Rhodamine-B, Ciprofloxacin, Atenolol, Ibuprofen, and Carbamazepine. Batch tests were conducted to investigate the effect of adsorption time and varying adsorbent dosages. The obtained greener porous graphene showed fast kinetics, which was determined to be guided by pseudo second-order kinetics and the maximum pollutant removal efficiency (>80%) was seen at a high adsorbent dosage (2 mL injected from a 5 g/L solution). Furthermore, the nonlinear adsorption modeling confirmed that the greener porous graphene followed the Langmuir model for the dye rhodamine-B sorption and the Freundlich model for all the other six contaminants. This greener porous graphene can be considered an effective adsorbent for the removal of organic pollutants in wastewater.

Insight into the novel ZIF-8@N-CQDs/ZIF-67 nanocomposite for photocatalytic degradation of methylene blue under visible light irradiation

A novel and stable composite of ZIF-8@N-CQDs/ZIF-67 was synthesized using simple solvothermal methods. The structural and morphological properties of the composite were investigated using different techniques. The ability of N-CQDs to improve the photocatalytic activity of ZIF-8@ZIF-67 for the photodegradation of methylene blue (MB) using visible and solar light was tested.The composite exhibited higher light adsorption and charge separation capabilities than N-CQDs and ZIF-8@ZIF-67. The degradation % of 32.0 ppm MB under visible light irradiation reached 94.0 % after 180 min, and the composite maintained its photoactivity after four cycles with a minimal decrease in the degradation efficiency.Scavenging tests indicated that the free electrons (superoxide radicals) played a major role in the photodegradation of MB, which is followed by hydroxyl radicals and holes. Therefore, this work provides a new, stable, environmentally friendly, and highly effective photocatalyst for the treatment of various organic pollutants under visible light irradiation.

Strong Interface Interaction of ZnO Nanosheets and MnSx Nanoparticles Triggered by Light over Wide Ranges of Wavelength to Enhance Their Removal of VOCs

The characteristics of the surface and interface of nanocomposites are important for exerting multi-functional properties and widening interdisciplinary applications. These properties are mainly depending on the electronic structures of materials. Some key factors, such as the surface, interface, grain boundaries, and defects take vital roles in the contribution of desired properties. Due to the excellent sensitivity of the QCM (quartz crystal microbalance) device, the surface and interface features of the nanocomposite were studied with the aid of the gas-response of the sensors (Sensor’s Gas-Sensitivity) in this work. To make full use of the visible light and part of NIR, a ZnO/MnSx nanocomposite was constructed using hydrothermal synthesis for narrowing the bandgap width of wide bandgap materials. The results indicated that the absorbance of the resulting nanocomposite was extended to part of the NIR range due to the introduction of impurity level or defect level, although ZnO and MnS belonged to wide bandgap semiconductor materials. To explore the physical mechanism of light activities, the photoconductive responses to weak visible light (650 nm, etc.) and NIR (near-infrared) (808 nm, 980 nm, and 1064 nm, etc.) were studied based on interdigital electrodes of Au on flexible PET (polyethylene terephthalate) film substrate with the casting method. The results showed that the on/off ratio of ZnO/MnSx nanocomposite to weak visible light and part of NIR light were changed by about one to five orders of magnitude, with changes varying with the amount of MnSx nanoparticle loading due to defect-assisted photoconductive behavior. It illustrated that the ZnO/MnSx nanocomposite easily produced photo-induced free charges, effectively avoiding the recombination of electrons/holes because of the formation of strong built-in electrical fields. To examine the surface and interface properties of nanocomposites, chemical prototype sensor arrays were constructed based on ZnO, ZnO/MnSx nanocomposite, and QCM arrays. The adsorption response behaviors of the sensor arrays to some typical volatile compounds were examined under a similar micro-environment. The results exhibited that in comparison to ZnO nanosheets, the ZnO nanosheets/MnSx nanocomposite increased adsorption properties to some typical organic volatile compounds significantly. It would have good potential applications in photo-catalysts, self-cleaning films, multi-functional coatings, and organic pollutants treatment (VOCs) of environmental fields for sustainable development. It provided some reference value to explore the physical mechanism of materials physics and photophysics for photo-active functional nanocomposites.