Degradation of 2,4-dichlorophenol using combined approach based on ultrasound, ozone and catalyst

Comparative study of the binding and activation of 2,4-dichlorophenol by dehaloperoxidase A and B

The dehaloperoxidase-hemoglobin (DHP), first isolated from the coelom of a marine terebellid polychaete, Amphitrite ornata, is an example of a multi-functional heme enzyme. Long known for its reversible oxygen (O2) binding, further studies have established DHP activity as a peroxidase, oxidase, oxygenase, and peroxygenase. The specific reactivity depends on substrate binding at various internal and external binding sites. This study focuses on comparison of the binding and reactivity of the substrate 2,4-dichlorophenol (DCP) in the isoforms DHPA and B. There is strong interest in the degradation of DCP because of its wide use in the chemical industry, presence in waste streams, and particular reactivity to form dioxins, some of the most toxic compounds known. The catalytic efficiency is 3.5 times higher for DCP oxidation in DHPB than DHPA by a peroxidase mechanism. However, DHPA and B both show self-inhibition even at modest concentrations of DCP. This phenomenon is analogous to the self-inhibition of 2,4,6-trichlorophenol (TCP) at higher concentration. The activation energies of the electron transfer steps in DCP in DHPA and DHPB are 19.3 ± 2.5 and 24.3 ± 3.2 kJ/mol, respectively, compared to 37.2 ± 6.5 kJ/mol in horseradish peroxidase (HRP), which may be a result of the more facile electron transfer of an internally bound substrate in DHPA. The x-ray crystal structure of DHPA bound with DCP determined at 1.48 Å resolution, shows tight substrate binding inside the heme pocket of DHPA (PDB 8EJN). This research contributes to the studies of DHP as a naturally occurring bioremediation enzyme capable of oxidizing a wide range of environmental pollutants.

Synthesis of Fe-TiO2@Fe3O4 magnetic nanoparticles as a recyclable sonocatalyst for the degradation of 2, 4-dichlorophenol

2, 4-Dichlorophenol is a type of chlorophenol that, even at low concentrations, causes adverse effects such as anemia, coma, weakening of the nervous system, and cancer in humans and other organisms. Therefore, the aim of this study was to synthesize the Fe-TiO₂@Fe₃O₄ sonocatalyst and to assess the removal efficiency of 2, 4-dichlorophenol using this sonocatalyst. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), value-stream mapping (VSM), Brunauer Emmett Teller (BET), and diffuse reflectance spectroscopy (DRS) analyses were performed for characterizing the synthesized nanoparticles. The effect of different factors, such as pH (3-9), initial concentration 2, 4-dichlorophenol (20-80 mg/L), and level of nanoparticles (200-600 mg/L) at different time points (15-90 min), was assessed on sonocatalytic removal of 2, 4-dichlorophenol, and then the reaction kinetics, process mechanism, and stability of the synthesized nanoparticles were determined under optimal conditions. The highest removal efficiency of 2, 4-dichlorophenol and constant reaction rate was obtained at pH of 5, the initial concentration of 20 mg/L, and the nanoparticles dose of 400 mg/L under ultrasound with a frequency of 35 kHz following the reaction time of 90 min. The maximum mineralization efficiency (total organic carbon TOC) under optimal conditions was 81%. Analysis of the degradation kinetics indicated that the 2, 4-dichlorophenol degradation can follow a first-order reaction. The stability of the synthesized sonocatalyst decreased by 91% after 5 re-uses. This study confirmed the efficiency of the Fe-TiO₂@Fe₃O₄ sonocatalytic process in the degradation and mineralization of 2, 4-dichlorophenol.

Integration of ozonation with water treatment for pharmaceuticals removal from Arroio Diluvio in southern Brazil

Pharmaceutical compounds can reach water bodies through sewage systems. The process of water treatment is insufficient for the removal of these contaminants. The ozonation has great potential to be integrated into the treatment, since it promotes the reduction of pharmaceuticals, reduces the generation of disinfection byproducts and can reduce operational costs. In this work, the integration of the ozonation process with water treatment was studied. The ozone was applied in the pre-oxidation and intermediate ozonation stages, to evaluate the dependence of different variables. Water samples were collected from Arroio Diluvio, a river of the city of Porto Alegre (Brazil). The doses of ozone were maintained between 0.5 and 1.0 mgO₃ L^-1 while the coagulant was between 25 and 150 mg·L^-1. Pre-ozonation resulted in a removal of pharmaceuticals at pH 10.0, time of 15 min and coagulant concentration of 52.5 mgL^-1. The intermediate ozonation provided a removal with pH 10.0 and a time of 5 min of bubbling. Based on the results, it was confirmed that the synergy of the ozonation process with conventional water treatment is an effective, sensitive and fast method for the removal of pharmaceuticals from the aqueous medium.

Optimization for minimizing the cost of ozonation of highly concentrated textile dyeing wastewater in a bubble column reactor

Ozonation is one of the advanced oxidation methods that provide effective decolorization and detoxification of the dyeing wastewater without causing any sludge formation. Despite being a good alternative to biodegradation, ozonation suffers from a high operating cost. This study conducted the ozonation process at high initial dye concentrations and optimized the process parameters (such as initial ozone concentration, initial dye concentration, and pH) to minimize the operating cost in terms of the overall power consumption of the process. The ozonation of Reactive Blue dye was performed in a bubble column reactor at various process conditions. A central composite design (CCD)-based response surface method (RSM) statistical tool was used to optimize the process. An empirical correlation for the specific power consumption (defined as electricity consumed per unit mass of dye removed from a unit volume of dyeing wastewater) was developed and verified. It was found that the specific power consumption during ozonation can be lowered significantly (by ~25-30%) if the dyeing water was treated at high initial dye concentrations.

Co, Cu, Fe, and Ni Deposited over TiO2 and Their Photocatalytic Activity in the Degradation of 2,4-Dichlorophenol and 2,4-Dichlorophenoxyacetic Acid

Pure TiO2 synthesized by the sol-gel method and subsequently deposited at 5% by weight with Co, Cu, Fe, and Ni ions by the deposition–precipitation method were studied as photocatalysts. The nanomaterials were analyzed by SEM, TEM, UV-Vis DRS, DRX, Physisorption N2, and XPS. The SEM and TEM images present a semi-spherical shape with small agglomerations of particles and average size between 63 and 65 nm. UV-Vis results show that a reduction below 3.2 eV exhibits a redshift displacement and increment in the optical absorption of the nanoparticles promoting the absorption in the UV-visible region. XRD spectra and analysis SAED suggest the characteristic anatase phase in TiO2 and deposited materials according to JCPDS 21-1272. The specific surface area was calculated and the nanomaterial Ni/TiO2 (21.3 m2 g−1) presents a slight increment when comparing to TiO2 (20.37 m2g−1). The information generated by the XPS spectra present the deposition of metallic ions on the support and the presence of different valence states for each photocatalyst. The photocatalytic activity was carried out in an aqueous solution with 80 mg L−1 of 2,4-D or 2,4-DCP under UV light (285 nm) with 100 mg L−1 of each photocatalysts for 360 min. The nanomaterial that presented the best efficiency was Ni/TiO2, obtaining a degradation of 85.6% and 90.3% for 2,4-D and 2,4-DCP, respectively. Similarly, this material was the one that presented the highest mineralization, 68.3% and 86.5% for 2,4-D and 2,4-DCP, respectively. Photocatalytic reactions correspond to the pseudo-first-order Langmuir–Hinshelwood model.

Halide salts induced the photodegradation of a fat-burning compound 2, 4-dinitrophenol by iron-montmorillonite

Natural montmorillonite clay and anthropogenic organic pollutants frequently coexist in the estuarine environment where freshwater from rivers mixes with saltwater from the ocean. In this environment, the sharply changed aqueous chemistry especially salt content could significantly alter the photochemical behaviors of pollutants. However, this process was rarely investigated. In this study, the photodegradation of a representative anthropogenic weight-loss compound 2,4-dinitrophenol in the presence of Fe³⁺-montmorillonite and different halide salts was systematically investigated. Results show that 2,4-dinitrophenol was resistant to photodegradation by Fe³⁺-montmorillonite alone, but the presence of NaCl, NaBr, and sea salts in the system can evoke significant 2,4-dinitrophenol degradation. The enhancement effect was further elucidated as the replacement reaction between the clay associated Fe³⁺ and Na ⁺ which leads to the release of more interlayer Fe³⁺ from montmorillonite, resulting in increased production of high active hydroxyl radicals (˙OH) that can substantially damage 2,4-dinitrophenol molecule. In addition, halogen radicals from the reaction of halide ions with ˙OH were also confirmed to participate in 2,4-dinitrophenol degradation. Overall, this study implied that the changed salty condition in the estuarine water could induce the rapid transformation of organic pollutants that move from freshwater and have relatively stable photochemical properties.

The superior adsorption capacity of 2,4-Dinitrophenol under ultrasound-assisted magnetic adsorption system: Modeling and process optimization by central composite design

2,4-Dinitrophenol (DNP) was listed as a priority pollutant; accordingly, DNP-contaminated effluent must be treated before discharging to the receiving resources. In the present study, the hybrid ultrasound-assisted GO-Fe₃O₄ system was employed to decontaminate DNP solution. Ultrasound irradiation makes the mass transfer of adsorbate improved and Fe₃O₄ enables GO separation from liquid phase under external magnetic field. The as-synthesized GO-Fe₃O₄ composite was characterized by SEM, TEM, XRD, FTIR, BET and VSM. A response surface methodology based central composite design (RSM-CCD) was used to estimate and optimize of various variables on DNP removal percentage. Under optimal conditions (pH: 4.45, adsorbent dose: 0.178 g/L, ultrasound frequency: 40.02 kHz and DNP concentration: 50.10 mg/L, maximum adsorption capacity was calculated to be 425.58 mg/g for the ultrasound system, higher than the simple system 309.40 mg/g, indicating the importance of synergistic effect between the ultrasound waves and the adsorption process. The ultrasound-assisted adsorption system showed the better agreement with the Langmuir isotherm (R² > 0.997), while the results of the stirring system were more consistent with the Freundlich model (R² > 0.991). The experimental results indicated that the pseudo-second-order kinetic model well fitted by experiment data and rate constant was calculated to be 0.000148 min^-1 and 0.000002 min^-1 under ultrasound and silent systems, respectively. The rate of desorption under ultrasound was more favorable and reuse of the adsorbent in both systems after 10th consecutive cycles reduced by about 22%. Thermodynamic calculations also confirmed the endothermicity and spontaneity of both systems. Electrostatic attraction, hydrogen bonding, and π -π interactions played key roles during the adsorption of DNP onto the MGO. In conclusion, the outcomes of this study provide valuable information of the ultrasound-assisted GO-Fe₃O₄ system for practical applications.

Activation of peroxydisulfate by a novel Cu0-Cu2O@CNTs composite for 2, 4-dichlorophenol degradation

In this study, a novel Cu⁰-Cu₂O@CNTs composite was synthesized, characterized and applied to activate peroxydisulfate (PDS) for the degradation of 2, 4-dichlorophenol (2,4-DCP) in contaminated lake water. The results indicated that Cu⁰-Cu₂O@CNTs can effectively activate PDS to produce O₂•^- radical, which has high selectivity to degrade organic pollutants in actual contaminated water. The efficiency of 2,4-DCP degradation and mineralization was 99.27% and 66.90%, respectively under the optimal condition. In the presence of Cl^-, HCO₃^- and natural organic matters (NOMs) or in real wastewater containing 2,4-DCP, Cu⁰-Cu₂O@CNTs/PDS system had a good selectivity for 2,4-DCP degradation. O₂•^- was the dominant reactive species in Cu⁰-Cu₂O@CNTs/PDS system for 2,4-DCP degradation. The possible degradation pathway of 2,4-DCP was proposed. It was concluded that Cu⁰-Cu₂O@CNTs composite could overcome the shortcomings of PDS activation by Cu⁰ and Cu₂O alone, such as low activating capability of Cu⁰ and instability of Cu₂O, which was high efficient for activating PDS. Cu⁰-Cu₂O@CNTs composite can be used as an efficient catalyst to activate PDS for the degradation of toxic organic pollutants in water and wastewater.

Uniform Mesoporous Amorphous Cobalt-Inherent Silicon Oxide as a Highly Active Heterogeneous Catalyst in the Activation of Peroxymonosulfate for Rapid Oxidation of 2,4-Dichlorophenol: The Important Role of Inherent Cobalt in the Catalytic Mechanism

Amorphous cobalt-inherent silicon oxide (Co-SiOx) was synthesized for the first time and employed as a highly active catalyst in the activation of peroxymonosulfate (PMS) for the rapid oxidation of 2,4-dichlorophenol (2,4-DCP). The characterization results revealed that the 0.15Co-SiOx possessed a high specific surface area of 607.95 m²/g with a uniform mesoporous structure (24.33 nm). The X-ray diffraction patterns indicate that the substituted cobalt atoms enlarge the unit cell parameter of the original SiO₂, and the selected area electron diffraction pattern confirmed the amorphous nature of Co-SiOx. More bulk oxygen vacancies (O_v) existing in the Co-SiOx were identified to be one of the primary contributors to the significantly enhanced catalytic activation of PMS. The cobalt substitution both creates and stabilizes the surficial O_v and forms the adequately active Co(II)-O_v pairs which engine the electron transfer process during the catalytic activities. The active Co(II)-O_v pairs weaken the average electronegativity of Co/Si and Co/O sites, resulting in the prevalent changes in final state energy, which is the main driving cause of the binding energy shifts in the X-ray photoelectron spectroscopy (XPS) spectra of Si and O among all samples. The increase of the relative proportion of Co(III) in the spent Co-SiOx probably causes the binding energy shifts of the Co XPS spectrum compared to that of the Co-SiOx. The amorphous Co-SiOx outperforms stable and quick 2,4-DCP degradation, achieving a much higher kinetic rate of 0.7139 min^-1 at pH = 7.02 than others via sulfate radical advanced oxidation processes (AOPs), photo-Fenton AOPs, H₂O₂ reagent AOPs, and other AOP approaches. The efficient degradation performance makes the amorphous Co-SiOx as a promising catalyst in removing 2,4-DCP or organic-rich pollutants.

Adsorption, degradation, and mineralization of emerging pollutants (pharmaceuticals and agrochemicals) by nanostructures: a comprehensive review

This review discusses a fresh pool of research findings reported on the multiple roles played by metal-based, magnetic, graphene-type, chitosan-derived, and sonicated nanoparticles in the treatment of pharmaceutical- and agrochemical-contaminated waters. Some main points from this review are as follows: (i) there is an extensive number of nanoparticles with diverse physicochemical and morphological properties which have been synthesized and then assessed in their respective roles in the degradation and mineralization of many pharmaceuticals and agrochemicals, (ii) the exceptional removal efficiencies of graphene-based nanomaterials for different pharmaceuticals and agrochemicals molecules support arguably well a high potential of these nanomaterials for futuristic applications in remediating water pollution issues, (iii) the need for specific surface modifications and functionalization of parent nanostructures and the design of economically feasible production methods of such tunable nanomaterials tend to hinder their widespread applicability at this stage, (iv) supplementary research is also required to comprehensively elucidate the life cycle ecotoxicity characteristics and behaviors of each type of engineered nanostructures seeded for remediation of pharmaceuticals and agrochemicals in real contaminated media, and last but not the least, (v) real wastewaters are extremely complex in composition due to the mix of inorganic and organic species in different concentrations, and the presence of such mixed species have different radical scavenging effects on the sonocatalytic degradation and mineralization of pharmaceuticals and agrochemicals. Moreover, the formulation of viable full-scale implementation strategies and reactor configurations which can use multifunctional nanostructures for the effective remediation of pharmaceuticals and agrochemicals remains a major area of further research.

Sonolytic degradation of bisphenol S: Effect of dissolved oxygen and peroxydisulfate, oxidation products and acute toxicity

In this paper, the kinetics of bisphenol S (BPS) degradation in the presence of peroxydisulfate (PDS) or dissolved oxygen (DO) in ultrasound (US) system were investigated. For PDS (US/PDS), increased PDS concentration result in faster BPS degradation, but the enhancement was not remarkable with multiplying PDS dosages. Therefore, heterogeneous PDS activation model based on a Langmuir-type adsorption mechanism was proposed to explain the trait of BPS abatement. The equilibrium constant of PDS (K_PDS) was calculated to be 2.91 × 10^-4/μM, which was much lower than that of BPS, suggesting that PDS was hard to adsorb on the gas-liquid interface of the cavitation bubble following by activation. Besides, the formation of •OH and SO₄^•- in US/PDS system was reinvestigated. The result showed that SO₄^•- rather than •OH was the predominant radical, which was quite different from previous study. Dissolved oxygen largely improve the degradation of BPS in US system and •OH rather than O₂^•- was proved to be the main reactive oxygen species (ROS). The improvement of •OH generation possibly caused by the reaction of DO with •H so that it cannot recombine with •OH. The transformation of the BPS in US system mainly included BPS radical polymerization, hydroxylation and hydrolysis. Frustratingly, the acute toxicity assay of Vibrio fischeri suggests that the degradation products of BPS are more toxic. These results will improve the understanding on the activation mechanisms of PDS and the role of dissolved oxygen play in US. Further investigations may need to explore other treatment ways of BPS and evaluate the acute toxicity of degradation products.

Sustainability criteria for assessing nanotechnology applicability in industrial wastewater treatment: Current status and future outlook

Application of engineered nanomaterials for the treatment of industrial effluents and to deal with recalcitrant pollutants has been noticeably promoted in recent years. Laboratory, pilot and full-scale studies emphasize the potential of this technology to offer promising treatment options to meet the future needs for clean water resources and to comply with stringent environmental regulations. The technology is now in the stage of being transferred to the real applications. Therefore, the assessment of its performance according to sustainability criteria and their incorporation into the decision-making process is a key task to ensure that long term benefits are achieved from the nano-treatment technologies. In this study, the importance of sustainability criteria for the conventional and novel technologies for the treatment of industrial effluents was determined in a general approach assisted by a fuzzy-Delphi method. The criteria were categorized in technical, economic, environmental and social branches and the current situation of the nanotechnology regarding the criteria was critically discussed. The results indicate that the efficiency and safety are the most important parameters to make sustainable choices for the treatment of industrial effluents. Also, in addition to the need for scaling-up the nanotechnology in various stages, the study on their environmental footprint must continue in deeper scales under expected environmental conditions, in particular the synthesis of engineered nanomaterials and the development of reactors with the ability of recovery and reuse the nanomaterials. This paper will aid to select the most sustainable types of nanomaterials for the real applications and to guide the future studies in this field.

Novel approaches based on hydrodynamic cavitation for treatment of wastewater containing potassium thiocyanate

Significant development in the industrial technologies and applications based on the use of cyanide derivatives has also led to significant environmental problems critically needing research in developing new technologies for effluent treatment. Present study investigates the use of novel treatment approach of hydrodynamic cavitation (HC) combined with chemical oxidation and catalyst for the degradation of Potassium Thiocyante (KSCN) for the first time. The effect of operating pressure (over the range of 2-5 bar) and initial pH (over the range of 2-7.1) on the degradation has been studied initially. Effect of combination of HC with H₂O₂ (varying KSCN:H₂O₂ ratios as 1:0.5-1:3), HC + O₃ (varying ozone mass flow rate over the range of 200-400 mg/h), HC + O₃ + catalyst (TiO₂/ZnO/CuO at fixed loading of 0.1 g/L at optimized ozone flow rate) as process intensifying approaches on the KSCN degradation has also been studied. Combination of HC + O₃ + CuO at different loadings of CuO has also been investigated. Use of combination of HC with H₂O₂ and HC with Ozone resulted in extent of KSCN degradation as 73% and 71.1% respectively. Among the different combinations of HC + O₃ + Catalysts (TiO₂/ZnO/CuO), HC + O₃ + CuO (at loading of 0.15 g/l) resulted in highest KSCN degradation as 86.5%. Combination of HC + H₂O₂ + O₃ + CuO was established to be the best approach yielding complete degradation with synergistic index of 2.98 and 92.9% as the COD removal. The study also focused on establishing kinetic rate constants which revealed that all the approaches followed first order mechanism with higher rate constants for the combination approaches as compared to individual approach. Overall, it has been conclusively established that hydrodynamic cavitation based combined treatment schemes are very effective for the treatment of biorefractory wastewaters containing cyanide derivatives.

Sonocatalytic treatment of phosphonate containing industrial wastewater intensified using combined oxidation approaches

Treatment of actual industrial wastewater is a challenging task and has not been investigated using the cavitation-based approaches significantly. In the present work, sonocatalytic degradation (catalysts as CuO and TiO₂) of phosphonate based industrial wastewater, procured from a local company, has been studied in terms of COD reduction under optimized conditions (established using initial studies involving only ultrasound) of pH as 3.2, the temperature of 32 ± 2 °C and 120 min as treatment time. The combination of ultrasound with H₂O₂ and ozone in different approaches has been investigated for maximizing the COD reduction. The optimum set of operating conditions for the sonocatalytic degradation were established as power dissipation of 90 W and catalyst loading as 0.75 g/L for CuO and 0.5 g/L for TiO₂. Use of only ultrasound resulted in COD reduction of 37.2% whereas the combination of US with different approaches resulted in higher extents of COD reduction. The combined operation of US + H₂O₂ + O₃, US + O₃ + H₂O₂ + CuO, and US + O₃ + H₂O₂ + TiO₂ resulted in the extent of COD reduction as 91.5%, 93.8%, and 95.8% respectively. Overall, it has been clearly established that maximum COD reduction is obtained for the combined operation of sonocatalysis (catalyst as TiO₂) with ozone and H₂O₂.

Ultrasound-assisted preparation of a nanostructured zinc(II) amine pillar metal-organic framework as a potential sorbent for 2,4-dichlorophenol adsorption from aqueous solution

Using a green and simple route with ultrasound illumination under atmospheric pressure and at room temperature, the nanosized preparation of a Zn(II) metal-organic framework, [Zn(ATA)(BPD)]_∞ (ATA = 2-aminoterephthalic acid), BPD = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene), having nano-plate shape and 3D channel framework, was considered and the product was named as compound 1. The X-ray diffraction (XRD), scanning electron microscopy (SEM), IR spectroscopy, Brunauer-Emmett-Teller (BET), and thermogravimetric analysis (TGA) were used for characterization of the synthesized micro/nano-structures. Further, impact of different sonication times and initial reagent contents on the shape and size of the micro/nano-structures was investigated. The results show that under ultrasound irradiation non-aggregated plates with uniform morphology can be obtained with content of [0.0125] M of the initial reagents in the presence of triethylamine (TEA) at 120 min. Moreover, through N₂ adsorption, effect of the preparation route on the porosity was explored. The bulk and nano-plates of compound 1 were also studied for adsorption of 2,4-dichlorophenol as a pollutant sample. Kinetic studies indicated that 2,4-dichlorophenol adsorption via MOF nano-plates are of first-order kinetics. Also, MOF nano-plates have significantly been reutilized for five times while their adsorption properties have remained unchanged.

Degradation of 2, 4-dichlorophenol in aqueous solution by dielectric barrier discharge: Effects of plasma-working gases, degradation pathways and toxicity assessment

Chlorinated phenols are a class of contaminants found in water and have been regarded as a great potential risk to environment and human health. It is thus urgent to develop effective techniques to remove chlorinated phenols in wastewater. For this purpose, we employed dielectric barrier discharge (DBD) in this work and studied the efficiency of DBD for the degradation of 2,4-dichlorophenol (2,4-DCP), one of the most typical chlorophenols in the environment. The effects of pH value, applied voltage and plasma-working gases on the dichlorophenol-removal efficiency were investigated. The results demonstrate that DBD plasma could successfully degrade 2,4-DCP, achieving efficiency of 98.16% (k = 1.09 min^-1) in the Ar-DBD system, and 77.60% (k = 0.48 min^-1) in the N₂-DBD system, with the process following the first-order kinetics. The removal efficiency was reduced in the presence of radical scavengers, confirming that hydroxyl radicals played a key role in the degradation process, while other active substances were also found such as nitrogen radicals in the N₂-DBD system, which was found to have also contribution to the degradation of 2,4-DCP. The intermediates and final products generated in the degradation process were analyzed using gas chromatography-mass spectrometry (GC-MS). Based on the identification of intermediates, the degradation pathways and mechanism were proposed and discussed. Besides, the toxicity of the DBD treated 2,4-DCP solution was also assessed using GFP-expressing recombinant Escherichia coli (E. coli) as the testing organism, showing that plasma treatment could substantially reduce the toxic effect of 2,4-DCP.

Silver ion-enhanced particle-specific cytotoxicity of silver nanoparticles and effect on the production of extracellular secretions of Phanerochaete chrysosporium

This study investigated the influence of silver ions (Ag⁺) on the cytotoxicity of silver nanoparticles (AgNPs) in Phanerochaete chrysosporium and noted the degree of extracellular secretions in response to the toxicant's stress. Oxalate production was elicited with moderate concentrations of 2,4-dichlorophenol (2,4-DCP) and AgNPs reaching a plateau at 10 mg/L and 10 μM, respectively. Increased oxalate accumulation was accompanied by higher activities of manganese peroxidase (MnP) and lignin peroxidase (LiP). However, the secretion of oxalate, MnP and LiP was significantly inhibited owing to Ag⁺ incorporation into AgNP solution. Production of extracellular polymeric substances (EPS) significantly elevated with an increase in 2,4-DCP concentrations; however, after 24 h of exposure to 100 mg/L 2,4-DCP, an obvious decrease in EPS occurred, indicating that part of EPS could be consumed as carbon and energy sources to ameliorate biological tolerance to toxic stress. Furthermore, AgNP-induced "particle-specific" cytotoxicity was substantially enhanced with additional Ag⁺ as evidenced by its significant negative impact on cellular growth, plasma membrane integrity, and morphological preservation compared with AgNPs at equal Ag concentration.

Ultrasound-assisted synthesis of Zinc(II)-based metal organic framework nanoparticles in the presence of modulator for adsorption enhancement of 2,4-dichlorophenol and amoxicillin

In this study, under a sonochemical method, a 3D, porous Zn(II)-based metal-organic framework [Zn(TDC)(4-BPMH)]_n·n(H₂O) is produced, which is called compound 1. To this end, the dicarboxylate linker of TDC, (2,5-thiophene dicarboxylic acid) and the pillar spacer of 4-BPMH, (N,N-bis-pyridin-4-ylmethylene-hydrazine) were employed. Moreover, variations in the morphology and growth of the micro/nanoparticles of compound 1 were investigated in terms of the effect of temperature, ultrasound irradiation power, sonication time, initial reagent concentrations, and pyridine concentration as a modulator. DFT model was used to examine the sonication effect on the distribution of the pore sizes. Moreover, the preparation method effect on the porosity and removal of two sample pollutants (i.e., 2,4-dichlorophenol (24-DCP) and amoxicillin (AMX)) from wastewater was studied.

Comparative study on 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol removal from aqueous solutions via ozonation, photocatalysis and non-thermal plasma using a planar falling film reactor

Ozonation and advanced oxidation processes based on photocatalysis (P.C.) and non-thermal plasma generated in a dielectric barrier discharge (DBD) in different gas atmospheres were compared for the degradation and mineralization of 2,4-dichlorophenoxy acetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) in aqueous solutions, using a planar falling film reactor with comparable design. The energetic yields (G₅₀) as measure of the efficiencies of the different methods are for 2,4-D in the order DBD/Ar-Fenton>ozonation>DBD/Ar>P.C.ozonation>DBD/Ar:O₂≫DBD/Air>P.C.oxidation. For 2,4-DCP the order is ozonation≫DBD/Ar-Fenton>P.C.ozonation>DBD/Ar>DBD/Ar:O₂≫P.C.oxidation>DBD/Air. The degradation by using ozone is very effective, but it should be noted that the mineralization measured by the total organic carbon (TOC) removal is low. The reason is the formation of stable towards ozone intermediates, especially low chain carboxylic acids. The fate of these intermediates during the degradation with the different methods has been followed and discussed.

Hybrid treatment strategies for 2,4,6-trichlorophenol degradation based on combination of hydrodynamic cavitation and AOPs

Utilization of hybrid treatment schemes involving advanced oxidation processes and hydrodynamic cavitation in the wastewater treatment forms the prime focus of the present work. The initial phase of the work includes analysis of recent literature relating to the performance of combined approach based on hydrodynamic cavitation (HC) for degradation of different pollutants followed by a detailed investigation into degradation of 2,4,6-trichlorophenol (2,4,6-TCP). The degradation of the priority pollutant, 2,4,6-TCP, using combination of HC based on slit-venturi used as the cavitating device, ozone and H₂O₂ has been investigated. The effect of operating pressure (2-5bar) and initial pH (3-11) have been investigated for the degradation using only HC. The degradation using only ozone (100-400mg/h) and only H₂O₂ has also been studied. The efficacy of the combined operation of HC+O₃ at different ozone flow rates (100-400mg/h) and the combined operation of HC+H₂O₂ at different loadings of H₂O₂ (2,4,6-TCP:H₂O₂ as 1:1-1:7) have been subsequently investigated. The degradation efficacy has also been established for the combined treatment strategies of O₃+H₂O₂ and HC+O₃+H₂O₂ at the optimum conditions of temperature as 30°C, inlet pressure of 4bar and initial pH of 7. Extent of 2,4,6-TCP degradation, TOC and COD removal obtained for HC+O₃ process were 97.1%, 94.4% and 78.5% respectively whereas for O₃+H₂O₂ process, the values were 95.5%, 94.8% and 76.2% and for HC+O₃+H₂O₂ process the extent of reduction were 100%, 95.6% and 80.9% in the same order. The combined treatment approach as HC+O₃+H₂O₂ was established as the most efficient approach for complete removal of 2,4,6-TCP with near complete TOC removal.

Degradation of carbamazepine using hydrodynamic cavitation combined with advanced oxidation processes

Degradation of carbamazepine (CBZ), a widely detected recalcitrant pharmaceutical in sewage treatment plant (STP) effluent, has been studied in the present work using combination of hydrodynamic cavitation (HC) and advanced oxidation processes (AOPs). Due to its recalcitrant nature, it cannot be removed effectively by the conventional wastewater treatment plants (WWTPs) which make CBZ a pharmaceutical of very high environmental relevance and impact as well as stressing the need for developing new treatment schemes. In the present study, the effect of inlet pressure (3-5bar) and operating pH (3-11) on the extent of degradation have been initially studied with an objective of maximizing the degradation using HC alone. The established optimum conditions as pressure of 4bar and pH of 4 resulted in maximum degradation of CBZ as 38.7%. The combined approaches of HC with ultraviolet irradiation (HC+UV), hydrogen peroxide (HC+H₂O₂), ozone (HC+O₃) as well as combination of HC, H₂O₂ and O₃ (HC+H₂O₂+O₃) have been investigated under optimized pressure and operating pH. It was observed that a significant increase in the extent of degradation is obtained for the combined operations of HC+H₂O₂+O₃, HC+O₃, HC+H₂O₂, and HC+UV with the actual extent of degradation being 100%, 91.4%, 58.3% and 52.9% respectively. Kinetic analysis revealed that degradation of CBZ fitted into first order kinetics model for all the approaches. The processes were also compared on the basis of cavitational yield and also in terms of total treatment cost. Overall, it has been demonstrated that combined process of HC, H₂O₂ and O₃ can be effectively used for treatment of wastewater containing CBZ.