Electrochemical degradation of 2,4-Dinitrotoluene (DNT) from aqueous solutions using three-dimensional electrocatalytic reactor (3DER): Degradation pathway, evaluation of toxicity and optimization using RSM-CCD

A comprehensive review of PbO2 electrodes in electrocatalytic degradation of organic pollutants

This paper provides a systematic review of recent advancements in PbO2 electrodes for the electrocatalytic degradation of organic pollutants, emphasizing innovative breakthroughs and key technological optimizations in this domain. This work analyzes PbO2 electrode fabrication methods, assessing strengths/weaknesses, and summarizes recent advances in surface modification. Atomic-scale strategies such as elemental doping, composite oxides, and nanomaterial coupling, enhance its catalytic performance. Kinetic modeling and characterization confirm the improved efficiency and durability in organic contaminant mineralization. Kinetic and experimental analyses demonstrate the high efficiency and stability of modified PbO2 electrodes in degrading organic pollutants. Industrial feasibility analysis indicates that the PbO2 electrode demonstrates technical robustness, economic viability, and scalability for industrial implementation. This work elucidates direct/indirect oxidation mechanisms in electrocatalysis, revealing correlations between surface reactive sites and active oxidant generation, guiding electrode design optimization. Looking ahead, this paper proposes innovative trajectories for PbO2 electrode technology, such as exploring novel modified materials, intelligently designing hierarchical architectures, and integrating advanced systems with smart control. These directions aim to promote its widespread use in environmental protection for more efficient and eco-friendly organic pollutant treatment. This review enriches the theoretical framework for PbO2 electrode electrocatalytic degradation of organic contaminants and offers references and inspirations for future research.

Sustainable biodegradation of malachite green dye by novel non-pathogenic Pseudomonas aeruginosa ED24

Sustainable management of textile industrial wastewater is one of the severe challenges in the current regime. It has been reported that each year huge amount of textile industry discharge especially the dye released into the environment without pre-treatment that adversely affect the human health and plant productivity. In the present study, different bacterial isolates had been isolated from the industrial effluents and investigated for their bioremediation potential against the malachite green (MG) dye, a major pollutant of textile industries. The biochemical and molecular characterization of the bacterial strain showed the resemblance of most potent strain ED24 as Pseudomonas aeruginosa, which showed effective bioremediation potential against the MG dye. During response surface analysis (RSM), best MG degradation conditions have been observed at pH 7.0, 37 °C, 48 h, and 200 mg/L dye concentration, with highest degradation efficiency of 96.56 ± 0.8622 percent. Subsequently, supplementing various carbon and nitrogen sources increases MG decolorization by 1 to 2%, with beef extract (97.23%), sodium nitrate (97.46%), and maltose (98.67%). FT-IR results revealed the disappearance of distinct peaks, namely, 3328.275 cm-1, 2102.842 cm-1, 1101.140 cm-1, and 559.04 cm-1 from MG, and the formation of major intermediate compounds like leucomalachite green, benzoic acid, diacetamide, benzeneacetic acid, hexyl ester, ethyl 4-acetoxy butanoate, butanoic acid, and 2-methyl in GC-MS analysis of degraded dye sample confirms the biodegradation by bacterial strain ED24. The phytotoxicity studies on mung bean seeds confirmed MG dye toxicity reduction up to 67.53%, 54.16%, and 67.53% in biomass accumulation, root, and shoot lengths, respectively. Also, the microbial toxicity of MG was completely reduced on soil microflora Bacillus flexus, Stenotrophomonas maltophilia, Escherichia coli, Staphylococcus aureus, and Alternaria spp. The dual mitigation, both in microbial and plant systems, indicates the strong remediation potential of P. aeruginosa ED24 to break down MG dye ecologically sustainably.

Optimizing chromium removal from synthetic wastewater via electrocoagulation process with a natural coagulant (blended of eggshell powder and lime) using response surface methodology

The presence of chromium (Cr) in synthetic wastewater has become a serious environmental issue. Therefore, main aim of this work was to investigate Cr removal from synthetic wastewater via electrocoagulation (EC) with a natural coagulant using aluminum electrodes. The central composite design (CCD) of the response surface methodology (RSM) method was used to optimized the operating variables of solution pH (5-9), initial Cr concentration (225-475 mgL-1), reaction time (30-40 min), and applied current (0.35-0.55 A). The ANOVA results clearly shows that the quadratic model (p < 0.0001) was sufficient to the best predicting of the removal performance of Cr (R2 = 0.9994 for electrode distance of 0.5 cm and 0.9924 for 1 cm). The maximum removal (99.836 % for electrode distance of 0.5 cm, and 98.175 % for 1 cm) of Cr was achieved with optimized conditions of solution pH 7.053, initial Cr concentration 337.795 mgL-1, reaction time 37.148 min, and applied current of 0.505 A. From this finding, it was proved that the EC process assisted with natural coagulant is an efficient, and cost-effective method for the removal of Cr from synthetic wastewater.

Optimizing oxytetracycline removal from aqueous solutions using activated carbon from barley lignocellulosic wastes with isotherms and thermodynamic studies

The excessive presence of antibiotics such as Oxytetracycline (OTC) in the wastewater has increased health problems due to their toxic impact on the aquatic ecosystem. Therefore, their removal has become an important topic. This study aims to produce high surface area-activated carbon derived from low-cost and environmentally friendly barley lignocellulosic wastes to remove OTC from aqueous solutions. The synthesized barley wastes-activated carbon (BW-AC) was characterized using Fourier-Transform Infrared spectroscopy, Thermal Gravimetric Analysis, X-ray diffraction analysis, N2 adsorption/desorption isotherms, and Scanning Electron Microscopy. A Central Composite Design under the Response Surface Methodology (CCD-RSM) was applied to optimize the operational parameters (adsorbent dosage, pH, OTC initial concentration, and contact time) affecting the adsorption capacity as the response factor. The optimum condition of OTC adsorption by BW-AC was the adsorbent dosage of 16.25 mg, pH of 8.25, initial concentration of 62.50 mg/L, and contact time of 23.46 min. An analysis of variance (ANOVA) was performed to investigate the significance of the designed quadratic model and evaluate the parameters interactions. The linear regression coefficient (R2) of 0.975 shows a good correlation between predicted and actual results. The adsorption isotherms were used to determine the contaminant distribution over the adsorbent surface, and the equilibrium data was best described by the Freundlich isotherm due to the R2 value of 0.99 compared to other isotherms and β parameter of 0.23 in Redlich-Peterson equation. Moreover, the n value of 1.25 in Freundlich equation and E value of 0.31 in Dubinin-Radushkevich equation indicates a physical nature of adsorption process. According to the equations results, the maximum adsorption capacity of BW-AC for OTC removal was 500 mg/g, based on the Langmuir isotherm equation. In addition, the thermodynamic studies indicated an endothermic process based on the 0.31 value of ΔH° and spontaneous nature due to the negative amount of ΔG° within the temperature range of 288-318 K. Consequently, the prepared BW-AC can be deemed as a highly effective adsorbent with a large surface area, resulting in significant capacity for removing OTC. This synthesized BW-AC can serve as an environmentally friendly adsorbent for affordable wastewater treatment and is poised to make valuable contributions to future research in this field.

Optimisation of PAHs biodegradation by Klebsiella pneumonia and Pseudomonas aeruginosa through response surface methodology

Response Surface Methodology (RSM) with Box-Behnken Design (BBD) is used to optimise the Phenanthrene (PHE) degradation process by Klebsiella pneumoniae (K bacteria) and Pseudomonas aeruginosa (P bacteria). Wherein substrate concentration, temperature, and pH at three levels are used as independent variables, and degradation rate of PHE as dependent variables (response). The statistical analysis, via ANOVA, shows coefficient of determination R2 as 0.9848 with significant P value 0.0001 fitting in second-order quadratic regression model for PAHs removal by Klebsiella pneumonia, and R2 as 0.9847 with significant P value 0.0001 by P bacteria. According to the model analysis, temperature (P < 0.0006) is the most influential factor for PHE degradation efficiency by K bacteria, while pH (P < 0.0001) is the most influential factor for PHE degradation by P bacteria. The predicted optimum parameters for K bacteria, namely, temperature, substrate concentration, and pH are found to be 34.00℃, 50.80 mg/L, and 7.50, respectively, and those for P bacteria are 33.30℃, 52.70 mg/L, and 7.20, respectively. At these optimum conditions, the observed PHE removal rates by two bacteria are found to be 83.36% ± 2.1% and 81.23% ± 1.6% in validation experiments, respectively. Thus RSM can optimise the biodegradation conditions of both bacteria for PHE.

Advances in three-dimensional electrochemical degradation: A comprehensive review on pharmaceutical pollutants removal from aqueous solution

Water pollution, stemming from various contaminants including organic and pharmaceutical pollutants, poses a significant global challenge. Amidst the array of methods available for pollutant mitigation, the three-dimensional electrochemical approach emerges as a standout solution due to its environmental compatibility, cost-effectiveness, and rapid efficiency. This study delves into the efficacy of three-dimensional electrochemical processes in purging organic and pharmaceutical pollutants from aqueous media. Existing research indicates that the three-dimensional electrochemical process, particularly when employing particle electrodes, exhibits notable success in degrading organic and pharmaceutical pollutants. This achievement is largely attributed to the ample specific surface area of particle electrodes and the shortened mass transfer distance, which collectively enhance efficiency in comparison to traditional two-dimensional electrochemical methods. Moreover, this approach is lauded for its environmental friendliness and cost-effectiveness. However, it is imperative to note that the efficacy of the process is subject to various factors including temperature, pH levels, and current intensity. While the addition of oxidants can augment process efficiency, it also carries the risk of generating intermediate compounds that impede the reaction. In conclusion, the three-dimensional electrochemical method proves to be a viable and practical approach, provided that process conditions are meticulously considered and adhered to. Offering advantages from both environmental and economic perspectives, this method presents a promising alternative to conventional water and wastewater treatment techniques.

Modelling and optimization of fenton process for decolorization of azo dye (DR16) at microreactor using artificial neural network and genetic algorithm

The Fenton process is widely employed for decolorizing industrial wastewater. Therefore, it is imperative to construct a model for optimizing the operational parameters and estimating the efficiency of decolorization within this process. In this study, an artificial neural network (ANN) model was created based on experimental data provided by a previous researcher who examined the decolorization of Direct Red 16 dye (DR16) using a heterogeneous Fenton process within a microchannel reactor. This model was utilized to optimize and forecast the efficiency of decolorization in the Fenton process. The accuracy of the model was validated by comparing its outcomes with actual experimental data. To further improve the efficiency of decolorization, optimal operational parameters were ascertained utilizing the genetic algorithm method. The study revealed that as dye concentrations increased from 10 to 40 mg/l, decolorization efficiencies improved proportionately, peaking at 89.78 %. Optimal operational parameters for maximizing efficiency were identified as a feed flow rate of 1 ml/min, H2O2 concentration at 500 mg/l, Fe2+ concentration of 4 mg/l, and maintaining pH between 2.6 and 2.8. Insights derived from both experimental and model-generated data were used to analyze the impact of operational parameters on decolorization efficiency.

Effects of a novel Mg-C micro-electrolysis system for phenolic wastewater degradation: material characterization, influencing factors, and model optimization

This study investigated a novel magnesium carbon micro-electrolysis (Mg-C ME) system for strengthening the removal of phenolic compounds in wastewater. The effects of the Mg/C mass ratio, aeration intensity, initial pH and reaction time on the degradation of three phenolic compounds and the COD removal efficiency in the simulated wastewater were evaluated using one-factor-at-a-time (OFAT) method. The optimum values obtained for the Mg/C mass ratio, aeration intensity, initial pH and reaction time were 3:1, 4.0 L/(L·min), 5.0 and 2.5 h, respectively. The experimental removal rates of catechol, resorcinol, and phenol, under the mentioned conditions, were obtained to be 95.6%, 71.5%, and 48.8%, respectively. Meanwhile, the COD removal rates were 63.8%,44.7%,34.0%, respectively. Moreover, experiments were designed and analyzed based on the box-based designing response surface (BBD-RSM) method. According to the results, the Mg/C mass ratio was the most significant variable showing incremental effect on the removal efficiency of catechol in a way that maximum removal efficiency of catechol was achieved in Mg/C mass ratio of 3.23:1. The validation experiments showed that the maximum removal efficiency of catechol was 96.24% under optimization conditions. Resorcinol degradation characteristics analysis indicated that the Mg-C ME system performed a key function in phenolic compounds elimination. Results showed that the Mg-C ME has a considerable capability in removing the phenolic compounds and COD. Thus, it could be considered as an efficient pretreatment choice for treating phenolic wastewater in the future.

Pencil and Gold Electrode Materials for the Electrochemical Study and Analysis of Dinitrotoluene

The aim of our work was to investigate practical and robust methods for the electrochemical analysis of DNT. Using gold WEs, we differentiated between the nitro substituents in 2,4- and 2,6-DNT in organic electrolyte systems. Switching to an aqueous electrolyte (2 M H2SO4), a limit of detection (LOD) of 0.158 ppm (0.87 μM) and a limit of quantitation (LOQ) of 0.48 ppm (2.64 μM) were observed for 2,4-DNT. Subsequent simplification to wooden craft pencils as WEs in aqueous 2 M H2SO4 electrolyte achieved a LOD of 4.8 ppm (26.48 μM) and a LOQ of 14.6 ppm (80.54 μM) for 2,4-DNT. Alongside this easily renewable WE choice, 2 M H2SO4 was found to improve the solubility of DNT in aqueous media and has not been previously reported as an electrolyte in DNT electroanalysis. On testing a range of pencil grades from 4H to 8B, it was found that 4B gave the best sensitivity. The work serves as a preliminary study into materials that, through their simplicity and availability, may be suitable for the development of a robust and portable instrumental method through the electrochemical work presented here.

Accelerated Cr (VI) removal by a three-dimensional electro-Fenton system using green iron nanoparticles

Green-synthesized iron nanoparticles (GAP-FeNP) were used as particle electrodes in a three-dimensional electro-Fenton (3DEF) process to accelerate the removal of hexavalent chromium [Cr (VI)]. Removal was evaluated by varying the pH (3.0, 6.0, and 9.0) and initial Cr (VI) concentrations (10, 30, and 50 mg/L) at 5 and 25 min. These results demonstrated that GAP-FeNP/3DEF treatment achieved more than 94% Cr (VI) removal under all tested conditions. Furthermore, it was observed that Cr (VI) removal exceeded 98% under pH 9.0 in all experimental parameters tested. The results of the response surface methodology (RSM) determined two optimal conditions: the first, characterized by a pH of 3.0, Cr (VI) concentration at 50 mg/L, and 25 min, yielded a Cr (VI) removal of 99.7%. The second optimal condition emerged at pH 9.0, with Cr (VI) concentrations of 10 mg/L and 5 min, achieving a Cr (VI) removal of 99.5%. This study highlights the potential of the GAP-FeNP to synergistically accelerate Cr (VI) removal by the 3DEF process, allowing faster elimination and expansion of the alkaline (pH 9.0) applicability. PRACTITIONER POINTS: The required time for >99% of Cr (VI) removal by the GAP-FeNP/3DEF process was shortened from 25 to 5 min. EF process with GAP-FeNP reduces the time necessary for Cr (VI) removal, which is 67% faster than conventional methods. EF process using GAP-FeNP removed >94% of Cr (VI) after 25 min for all initial Cr (VI) concentrations and pH treatments. Cr (VI) removal by the GAP-FeNP/3DEF process was >98% at a pH of 9.0, widening the solution pH applicability.

Optimization of the photocatalytic degradation of phenol using superparamagnetic iron oxide (Fe3O4) nanoparticles in aqueous solutions

The present work was carried out to remove phenol from aqueous medium using a photocatalytic process with superparamagnetic iron oxide nanoparticles (Fe3O4) called SPIONs. The photocatalytic process was optimized using a central composite design based on the response surface methodology. The effects of pH (3-7), UV/SPION nanoparticles ratio (1-3), contact time (30-90 minutes), and initial phenol concentration (20-80 mg L-1) on the photocatalytic process were investigated. The interaction of the process parameters and their optimal conditions were determined using CCD. The statistical data were analyzed using a one-way analysis of variance. We developed a quadratic model using a central composite design to indicate the photocatalyst impact on the decomposition of phenol. There was a close similarity between the empirical values gained for the phenol content and the predicted response values. Considering the design, optimum values of pH, phenol concentration, UV/SPION ratio, and contact time were determined to be 3, 80 mg L-1, 3, and 60 min, respectively; 94.9% of phenol was eliminated under the mentioned conditions. Since high values were obtained for the adjusted R2 (0.9786) and determination coefficient (R2 = 0.9875), the response surface methodology can describe the phenol removal by the use of the photocatalytic process. According to the one-way analysis of variance results, the quadratic model obtained by RSM is statistically significant for removing phenol. The recyclability of 92% after four consecutive cycles indicates the excellent stability of the photocatalyst for practical applications. Our research findings indicate that it is possible to employ response surface methodology as a helpful tool to optimize and modify process parameters for maximizing phenol removal from aqueous solutions and photocatalytic processes using SPIONs.

Degradation and phosphorus immobilization treatment of organophosphate esters hazardous waste by Fe-Mn bimetallic oxide

Organophosphate esters (OPEs) waste is difficult to dispose effectively because of its stability and the potential risk of P element. In this study, taking one typical organic extractant of tributyl phosphate (TBP) as an example, we proposed a strategy to treat OPEs inspired by chemical looping combustion (CLC) technology-oxygen carrier immobilization process (OCIP), aiming at efficient TBP degradation and simultaneous P immobilization. Adopting Fe-Mn bimetallic oxide (FMBO) as oxygen carrier, an almost 100% P immobilization efficiency was achieved under recommended conditions which were obtained by response surface methodology. Meanwhile, gaseous products released from TBP degradation, e.g., non-methane hydrocarbon, was lower than the maximum allowable emission concentration limit. Further characterizations implied that P-species released from reaction process were mainly immobilized as stable inorganic forms of metaphosphate, phosphate and pyrophosphate. On the basis of identifying degradation intermediates, we proposed a possible degradation pathways. FMBO as an oxygen carrier provided sufficient oxygen molecules for flameless combustion of OCIP process. Electron paramagnetic resonance measurement confirmed the existence of oxygen vacancies on FMBO surface, which contributed to the formation of •O₂^-. Oxidation by oxygen molecules and •O₂^- attack resulted in the degradation and mineralization of TBP, with simultaneously achieving P stabilization.

Evaluation of Pb (II) Removal by Tea Pulp Modified with Magnetite Nanoparticle

Tea waste was used to successfully synthesize magnetic nanoparticles (TWMNPs). In this investigation, Pb (II) was eliminated by tea waste modified with magnetite nanoparticles (TWMNPs) was investigated. To prepare the TWMNPs, FeCl3.6H2O was dissolved in double distilled water (DDW) and 20 g of pulp tea was added slowly and stirred, after 30 min TWMNPs adsorbent were separated through an external magnetic field and washed three times with double distilled water (DDW) and ethanol then dried at 60°C. The FESEM test of TWMNPs shows the particle size in the range of 15–20 nm and spherical/cuboid-shaped crystal structure of Fe3O4 (magnetite). X-ray analysis showed that the main XRD diffraction peaks of TWMNPs are related to Fe3O4, HighScore plus X’Pert software was used to identify the phase in this sample. The specific surface area of the prepared magnetite nanoparticles was 25.2 m2.g−1. The pore volume, maximum pore radius, and VSM of TWMNPs were 14.4 cm3.g−1, 2.3 nm, and 3.37–2.41, respectively. The effects of various parameters, such as contact time, pH, concentration, and adsorbent dosage, were studied. The experimental isotherm data were analyzed using the Langmuir and Freundlich models, and it was found that the removal process followed the Langmuir isotherm and the maximum adsorption capacity calculated by Langmuir fitting was 10.67 mg.g−1. In addition, the adsorption kinetics followed the first-order kinetic model and the value of rate constant was found to be 14.04 × 10−2 min−1. The results showed that increasing the pH level led to a rise in the response level and Pb (II) removal. Also, the trend in Pb (II) removal and response level had an increase with increasing the initial concentration of Pb (II). Increasing contact time from 5 to 20 minutes has a slight effect on Pb (II) removal. Considering the results, TWMNPs could lead to suitable results for the removal of Pb (II) from wastewater containing this metal. And the maximum adsorption capacity was found to be 10.67 mg.g−1.

Optimization and Modeling of Cr (VI) Removal from Tannery Wastewater onto Activated Carbon Prepared from Coffee Husk and Sulfuric Acid (H2SO4) as Activating Agent by Using Central Composite Design (CCD)

The primary goal of this research is to lower the hexavalent chromium (Cr (VI)) concentration that has occurred from the growth of the tannery industry. As a result, the potential for heavy metal concentration is increasing day by day. Industrial effluent containing Cr (VI) contributes significantly to water pollution. Chromium hexavalent ion (Cr (VI)) in wastewater is extremely hazardous to the environment. It is critical to address such a condition using activated carbon derived from biomass. Adsorption is one of the most successful methods for removing hexavalent chromium from wastewater. Treated wastewater has no substantial environmental contamination consequences. The ash content, moisture content, volatile matter content, and fixed carbon content of wet coffee husk were 3.51, 10.85, 68.33, and 17.31, respectively. The physicochemical properties of coffee husk-based activated carbon (CHBAC) obtained during experimentation were pH, porosity, the yield of CHBAC, bulk density, point of zero charges, and specific surface area of 5.2, 58.4 percent, 60.1 percent, 0.71 g/mL, 4.19, and 1396 m2/g, respectively, indicating that CHBAC has a higher capacity as an adsorbent medium. For optimization purposes, the parameters ranged from pH (0.3–3.7), dose (2.3–5.7) $g$ , and contact time (0.3–3.7) hr. The quadratic models were chosen for optimization, and the $p$ value for the model was significant since it was less than 0.05, but the lack of fit model was inconsequential because it was more than 0.05. The optimum adsorption obtained with numerical optimization of Cr (VI) was 97.65 percent. This was obtained at a pH of 1.926, a dose of 4.209 g/L, and a contact time of 2.101 hours. This result was observed at a pH of 1.93, a dosage of 4.2 g/L, and a contact duration of 2.1 hours. The desirability obtained during numerical optimization was 1. Coffee husk-based activated carbon has a bigger surface area, and it has a stronger ability to absorb hexavalent chromium from tannery wastewater effluents.

Insight into the Fe-Ni/biochar composite supported three-dimensional electro-Fenton removal of electronic industry wastewater

For the efficient removal of the bio-refractory organic pollutants in the electronic industry wastewater, the Ni-Fe (oxides) modified three-dimension (3D) particle electrode was applied in electro-Fenton system (3D/EF), where iron ions were released from anode and deposited onto algal biochar (ABC) to prepare composite catalyst during reaction process. Firstly, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis were applied to confirm successful fabrication of the 3D particle electrode materials. Secondly, COD removal efficiency could reach about 80%, which was about 20% higher than that in 2D/EF system, under the optimized conditions as 2.0 g/L of Ni-ABC particle electrodes, initial pH of 3, 100 mL/min of aeration intensity and 20 mA/cm² of applied current density. Thirdly, characterized using three-dimensional fluorescence spectroscopy and GC-MS analysis, it seemed that most of the macromolecular substances could be degraded, whereas mono-2-ethylhexyl phthalate (MEHP) was identified as the most abundant and representative compound. Finally, possible degradation pathway of MEHP in 3D/EF system was proposed including dealkylation, cleavage of C-O bond, and demethylation. Therefore, this study provides a new strategy in designing EF system employing bimetal doped biochar composite for an efficient elimination of organic pollutants within electronic industry wastewater.

Experimental Study and an RSM Modelling on Drilling Characteristics of the Sheep Horn Particle Reinforced Epoxy Composites for Structural Applications

Recent environmental concern has been raised about the development of biocomposites because of their low cost, eco-friendliness, and biodegradability. Machining of polymeric composite is inevitable during assembly of structural components. In view of creating holes in structural composites, drilling is necessary and it is essential to carry out research to find the optimal machining parameters. The experimental assessment and prediction of the thrust force and torque involved in drilling composites reinforced with sheep horn are presented in this work. The matrix and sheep horn particles were combined in the right proportions before being moulded and poured into a mould, then allowed to cure at room temperature. Investigated properties included ultimate tensile strength, flexural strength, and hardness. To evaluate the quality of the hole, micrographs of the drilled hole were employed. When the mixture was optimised based on the properties, it was found that a 70:30 ratio produced the best results. Thrust force and torque of 58 N and 4.8 N-mm, respectively, were observed for sheep horn filler laminates which were drilled using the combination of 6 mm diameter, 0.1 mm/rev feed rate, and 400 rpm speed. This is by far the best among the combinations used in the experiment. Additionally, the experimental outcomes indicate that the feed rate and spindle speed are the most significant factors affecting the thrust force. Since there were minimal errors in the comparison, the central composite design modelling is consummate. Overall, the extensive experimental effort offers several options to utilise this composite material in future applications across a wide range of fields.

Construction of ANbO3 (A= Na, K)/f-carbon nanofiber composite: Rapid and real-time electrochemical detection of hydroxychloroquine in environmental samples

Hydroxychloroquine (HCQ) is a significant viral resistant drug widely acknowledged for its immunomodulatory and anti-inflammatory activities. To minimize the impact of HCQ residues on environmental pathways, exploring control measures is vital. In this regard, electrochemical sensing of HCQ using well-structured functional materials is advantageous. This work aims to provide an economical and sustainable route for the synthesis of ANbO₃ (A = Na,K) perovskites via a thymol-menthol-based natural deep eutectic solvent. The as-synthesized NaNbO₃ and KNbO₃ are pinned to functionalized carbon nanofibers (f-CNF) via an ultrasonication approach. Benefitting from the synergistic effect of rapid electron transfer and improved surface area, enhanced electrochemical activity for NaNbO₃@f-CNF/GCE is achieved. The fabricated NaNbO₃@f-CNF displays a LOD (DPV = 0.01 μM, i-t = 0.007 μM), wide dynamic range (DPV = 0.09-22.5 μM, i-t = 0.006-35 μM), outstanding selectivity, and reproducibility, proving feasible in real-time analysis with good recovery rates (±97.67-99.81%). The NADES-mediated preparation of perovskites evades the incorporation of traditional toxic solvents and yields atom-efficient ANbO₃ (A = Na,K) associated with green solvent templates. This validates the sustainable fabrication of electrode materials with reduced energy stipulations for detecting hazardous drug pollutants in the ecosystem.

Kinetics of zero-valent iron-activated persulfate for methylparaben degradation and the promotion of Cl. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2022;321:115973. [PMID: 36104884 DOI: 10.1016/j.jenvman.2022.115973]

Methylparaben (MP) is an emerging pollutant, and the optimal conditions and kinetics of MP degradation using nano-zero-valent iron-activated persulfate (nZVI/PDS) need to be further investigated. This paper firstly investigated the response surface methodology (RSM) analysis of MP degradation by the heterogeneous system nZVI/PDS and concluded that the initial pH had the most significant effect on MP degradation. The optimal experimental conditions predicted by the RSM were as follows: initial pH 2.75, [nZVI]₀ = 2.87 mM, [PDS]₀ = 2.18 mM (MP degradation level of 95.30%). First- and second-order kinetic fits were performed for different initial pH levels and different concentrations of MP, nZVI, and PDS. It was determined that k = 0.0365 min^-1 (R² = 0.984) when the initial pH was 3, [PDS]₀ = 2 mM, [MP]₀ = 20 mg L^-1, and [nZVI]₀ = 3 mM (MP degradation level of 94.25%). The rest of the conditions were more closely fitted to the second-order reactions. The effects of different concentrations of anions and humic acid (HA) on the MP degradation level and k were examined, and it was found that Cl^- could promote MP degradation to 97.69% (increased by 3.65%) and increase the k in accordance with the first-order reaction kinetics (0.0780 min^-1, R² = 0.991). Finally, the analysis of intermediates revealed 5 reaction pathways and 7 reaction intermediates, which inferred a possible reaction mechanism with the recycling performance of nZVI. In this paper, the superiority of nZVI/PDS for the purposes of activating MP degradation was affirmed. The presence of Cl^- can enhance the level of MP degradation was confirmed, which provides a new direction for future practical engineering applications.

Optical chemical sensor of Gd(iii) based on 5-(2'-bromophenyl- azo)-6-hydroxypyrimidine-2,4-dione immobilized on poly(methyl methacrylate) and 2-nitrophenyloctylether matrix

A novel optical chemical sensor (optode) was fabricated for the determination of Gadolinium ions. The optical sensor was prepared by incorporating a recently synthesized ionophore, 5-(2'-bromophenylazo)-6-hydroxy pyrimidine-2,4-dione (BPAHPD), and 2-nitrophenyloctylether (NPOE) as a plasticizer in poly(methyl methacrylate) (PMMA) membrane. The color of the sensing membrane in contact with Gd(iii) ions changed from yellow to red-orange due to the adsorption of Gd(iii) with the maximum absorbance (λ max) at 563 nm. The chemical sensor responds optimally towards Gd(iii) ions at the optimum conditions of pH 7.5, contact time 10 min, 150 ng mL-1 Gd(iii), and 5.0 mL solution. The linear regression equation achieved was A = 4.36C (μg mL-1) - 0.15 (r = 0.9976). A linear Gd(iii) calibration curve can be established in the concentration range of 5.0-250 ng mL-1 with R 2 = 0.9976. Detection and quantification limits are 1.47 and 4.75 ng mL-1, respectively. The molar absorptivity and Sandell sensitivity are found to be 6.86 × 107 L mol-1 cm-1 and 0.023 ng cm-2, respectively. In addition to its stability and reproducibility, the optode revealed a great selectivity toward Gd(iii) ions as compared to other coexisting ions in real samples. The recovery of Gd(iii) ions from the sensor material was achieved using 0.4 M HNO3 . The offered optode sensor membrane has been employed to monitor Gd(iii) in soil, sediments, river water, and urine with an internal standard addition method and compared statistically with the ICP-OES method. The results revealed calculated t-values between 1.11-1.85, whereas F values were in the range of 2.46-3.77 which did not exceed the theoretical values, indicating no significant difference at 95% confidence level. The observed percent recovery is in the range of 97.24-102.52%.

An eco-friendly and sustainable support of agave-fibers functionalized with graphene/TiO2:SnO2 for the photocatalytic degradation of the 2,4-D herbicide from the drinking water

In this research, we evaluated the photocatalytic performance of biodegradable composites for the removal of the 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide. The composite was composed by agave fibers (AgF), graphene-microplates (GM) and titanium dioxide TiO₂/SnO₂ (TSn) nanoparticles (NPs) and was named TSn + AgF/GM. Both, the TSn NPs and the GM were deposited on the AgF using the Dip-coating method. According to the analysis by X-Ray Diffraction (XRD), the crystalline phase for the TiO₂ and SnO₂ was anatase and tetragonal-rutile, respectively. The Scanning Electron Microscopy (SEM) images demonstrated that the AgF were completely saturated by the GM (which had average dimensions of 15 μm × 22 μm) and by conglomerations of TSn NPs with average size of 642 nm. The TSn NPs and the TSn + AgF/GM composite were evaluated for the photocatalytic degradation of the 2,4-D herbicide under ultraviolet-visible (UV-Vis) light and found a maximum degradation of 98.4 and 93.7% (after 4 h) for the TSn NPs and the TSn + AgF/GM composite, respectively. Reuse cycles were also performed and the degradation percentage decreased by 13.1% and by 7.8% (after 3 cycles of reuse) when the TSn NPs and the TSn + AgF/GM composite are employed, respectively. Scavenger experiments were also carried out and found that the oxidizing agents are mainly produced in the order of: •OH>•O₂^- > h⁺; then, the main oxidizing agents generated during the photocatalytic reaction were the hydroxyl radicals. Thus, the photocatalytic system studied in this work for the degradation of 2,4-D could pave the way for the development of new eco-friendly/floatable photocatalysts, which can be applied in wastewater-treatment plants.

Performance Optimization and Toxicity Effects of the Electrochemical Oxidation of Octogen

Octogen (HMX) is widely used as a high explosive and constituent in plastic explosives, nuclear devices, and rocket fuel. The direct discharge of wastewater generated during HMX production threatens the environment. In this study, we used the electrochemical oxidation (EO) method with a PbO2-based anode to treat HMX wastewater and investigated its degradation performance, mechanism, and toxicity evolution under different conditions. The results showed that HMX treated by EO could achieve a removal efficiency of 81.2% within 180 min at a current density of 70 mA/cm2, Na2SO4 concentration of 0.25 mol/L, interelectrode distance of 1.0 cm, and pH of 5.0. The degradation followed pseudo-first-order kinetics (R2 > 0.93). The degradation pathways of HMX in the EO system have been proposed, including cathode reduction and indirect oxidation by •OH radicals. The molecular toxicity level (expressed as the transcriptional effect level index) of HMX wastewater first increased to 1.81 and then decreased to a non-toxic level during the degradation process. Protein and oxidative stress were the dominant stress categories, possibly because of the intermediates that evolved during HMX degradation. This study provides new insights into the electrochemical degradation mechanisms and molecular-level toxicity evolution during HMX degradation. It also serves as initial evidence for the potential of the EO-enabled method as an alternative for explosive wastewater treatment with high removal performance, low cost, and low environmental impact.

Bioremediation of Textile Industrial Effluents Using Nutraceutical Industrial Spent: Laboratory-Scale Demonstration of Circular Economy

This research reports the first-ever study on abundantly available, environmentally friendly, low-cost and ready-for-use Nutraceutical Industrial Cumin Seed Spent (NICUS) as an innovative adsorbent for bioremediation of a bisazo Acid Red 119 (AR119) dye, a probable mutagen from textile industrial effluents (TIEs). The experiment at the laboratory scale is designed to suit the concepts of sustainability and valorisation under the domain of circular economy. The experimental qe value obtained was 96.00 mg g−1. The optimised conditions of parameters are as follows: pH of 2; adsorption time, 210 min; adsorbent dosage, 0.300 g L−1; particle size, 175 µM; initial dye concentration, 950 mg L−1; orbital shaking, 165 rpm and temperature, 50 °C, producing an impressive value of 748 mg of dye adsorbing on 1 g of dry NICUS. The adsorption capacity of NICUS obtained from the quadratic model developed for process optimisation gave values of 748 mg g−1. As a prelude to commercialisation, five variables that affect the adsorption process were experimentally studied. For the feasibility and efficiency of the process, a two-level fractional factorial experimental design (FFED) was applied to identify variables that influence the adsorption capacity of NICUS. The identified variables were applied to scale experiments by three orders. Nine isotherm models were used to analyse the adsorption equilibrium data. The Vieth–Sladek adsorption isotherm model was found to be the best fit. The pseudo-second-order reaction was the appropriate mechanism for the overall rate of the adsorption process. Mechanistic studies related to mass transfer phenomena were more likely to be dominant over the diffusion process. Techniques such as SEM, FTIR and CHN analysis were used to characterise NICUS. The dye-adsorbed NICUS obtained as “sludge” was used as a reinforcing material for the fabrication of composites using plastic waste. The physicomechanical and chemical properties of thermoplastic and thermoset composite using dye-adsorbed NICUS were evaluated and compared with NICUS composites. Prospects of integrating Small and Medium Enterprises (SMEs) into the circular economy of Nutraceutical Industrial Spent (NIS) are discussed.

Enhanced degradation of Rhodamine B dye by Fenton/peracetic acid and photo-Fenton/peracetic acid processes

In this research, the efficiency of advanced oxidation processes (AOPs) including Fenton−Peracetic Acid (PAA) and photo-Fenton− PAA in the removal of the Rodamine B (RhB) dye from aqueous solutions were studied. Investigating the effect of operating parameters such as pH (3–9), contact time (2–30 min), PAA concentration (10–80 mg/L), FeCl3.7H2O concentration (10–100 mg/L), and dye concentration (25–500 mg/L) on the performance of AOPs in removal of RhB was considered. The results showed that by decreasing pH and dye concentration, RhB removal efficiency increased. The optimal conditions for removal of RhB using Fenton− PAA process were determined to be as follows: dye concentration = 50 mg/L, pH = 3, PAA concentration = 50 mg/L, contact time = 10 min, and FeCl3 = 50 mg/L; in these conditions, removal efficiency of the RhB was 99.9%. In contrast, the photo-Fenton− PAA process was able to remove this amount of dye in just 5 min. The high performance of the system in a short time is attributed to the synergistic effect of the photo-Fenton− PAA process in the presence of UV. Finally, RhB dye was completely degraded by the photo-Fenton− PAA process and converted into CO2 and H2O products. In general, the photo-Fenton− PAA process compared to other methods can be used as a suitable and reliable method for the treatment of effluents of the dyeing industry and discharge them to the environment.

Optimization of the Anaerobic-Anoxic-Oxic Process by Integrating ASM2d with Pareto Analysis of Variance and Response Surface Methodology

Wastewater treatment plants (WWTPs) are high-energy-consuming units. Reasonable operation strategies can enable WWTPs to meet discharge standards while reducing the operating cost. In this study, the activated sludge model 2d (ASM2d), Pareto analysis of variance (ANOVA), and response surface methodology (RSM) were jointly used to simulate and optimize the operation of a lab-scale anaerobic-anoxic-oxic (AAO) reactor. The optimization objective was to determine the optimal design and operational parameters (DOPs) that could enhance both pollutant removal and energy saving. The DOPs that had significant influence on the optimization objective, such as sludge retention time (SRT), dissolved oxygen (DO), and the ratio of biodegradable chemical oxygen demand to total nitrogen (BCOD/TN), were identified by Pareto ANOVA. The optimal DOPs with SRT of 15 days, DO concentration of 0.5 mg/L, and BCOD/TN of 5.21 were determined by RSM. Under the optimal conditions, the removal efficiencies of NH4+-N, total nitrogen (TN), and total phosphorus (TP) were 96.2%, 76.8%, and 92.8%, respectively, and the annual operating cost was $26.4. Furthermore, this combination of DOPs was validated using a pilot-scale AAO system. The TN and TP removal efficiencies were improved by 11.0% and 5.0%, respectively, and the annual operating cost could be reduced by 15.0%. Overall, this study confirmed that the method integrating ASM2d with Pareto ANOVA and RSM was effective in optimizing wastewater treatment processes.