Contaminants In Aqueous Media Research Articles

Synergistic degradation of p-nitrophenol using peroxymonosulfate activated with a bimetallic Mn3O4–Cu2O catalyst: Investigation of strong interactions between metal oxides

The use of efficient, eco-friendly catalysts is essential for activating peroxymonosulfate (PMS) to degrade organic contaminants in aqueous media. In this study, we developed a novel approach to fabricating bimetallic MnCu catalysts (Mn:Cu molar ratios: 10:1, 5:1, 3:1, and 2:1) comprising tetragonal Mn3O4 and cubic Cu2O. MnCu-5:1 exhibited superior catalytic activity for the degradation of p-nitrophenol (PNP) using PMS because of the synergistic interplay between Mn and Cu. Experimental and density functional theory (DFT) calculation data revealed that the mixed valence states and strong interactions between Mn and Cu in the MnCu-5:1 system increased the electron transfer efficiency and promoted electron transfer to PMS. The results of quenching experiments elucidated a primary radical mechanism and minor nonradical pathway for the PNP degradation over the MnCu-5:1/PMS system. DFT calculations confirmed a relatively high adsorption energy of the Mn3O4–Cu2O (MnCu) composite, indicating enhanced catalytic performance. The superior reactivity of the composite was verified by analyzing its density of states and electrostatic difference potential. Our findings offer fresh perspectives for harnessing the synergistic potential of less toxic mixed metal oxides for controlling catalytic properties and help achieve a better understanding of the activation mechanism for contaminant degradation over MnCu catalysts.

Zero-dimensional luminescent carbon dots as fascinating analytical tools for the treatment of pharmaceutical based contaminants in aqueous media

A review of the most recent research on the environmental implications of pharmaceutical contaminants, conventional treatment techniques, and the application of CDs for the extraction and degradation of pharmaceutics in wastewater.

TiO2/Arabic Gum for Degradation of Pollutants in Water

Emerging contaminants and pollution are environmental problems threatening public health. Antibiotic ciprofloxacin and methylene blue dye are pollutants frequently detected in water systems worldwide. Photocatalysis is a process for water treatment. TiO2-based catalysts synthesized with natural gums show improved photocatalytic properties. Here, the sol–gel method synthesized TiO2/Arabic gum for photocatalytic performance. The innovation of this work was synthesized at 400 °C and investigated their photocatalytic proprieties using methylene blue and ciprofloxacin as model pollutants. XRD showed that the photocatalyst was in the anatase phase. The result showed that TiO2 with a band gap of 3.29 eV was achieved at a calcination temperature of 400 °C. Corresponding FTIR results suggest only the existence of functional groups related to TiO2. The SEM and BET method characterization indicated that TiO2/Arabic gum were spherical-shaped nanoparticles arranged in clusters with a mesoporous structure, contributing to photocatalytic performance. In addition, photocatalytic studies showed that the methylene blue dye and ciprofloxacin antibiotic degradation rates reached 99% and 94% under UV light, respectively. The hole (h+) and OH ⦁ radicals are essential in photodegradation. The synthesized material showed excellent photostability and maintained almost the same degradation percentage in the three consecutive cycles tested on the different pollutants. The TiO2/Arabic gum is an excellent candidate for future use in treating contaminants in aqueous media using photocatalysis. Therefore, TiO2/Arabic gum nanoparticles are a promising material for wastewater treatment.

Use of Sawdust (Aspidosperma polyneuron) in the Preparation of a Biocarbon-Type Adsorbent Material for Its Potential Use in the Elimination of Cationic Contaminants in Wastewater

Chemically modified bioadsorbents were prepared using sawdust (Aspidosperma polyneuron) functionalized with urea at different concentrations (BC-1M, BC-3M, and BC-6M) to evaluate their adsorption capacity by the methylene blue method. Fourier transform spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) were employed to characterize the surface morphology of the biomaterials. The best adsorption capacity was obtained using the biocarbon modified with urea 6M (BC-6M), displaying a methylene blue index of 12.4 mg/g with a zero-charge point (pHpzc) at 5.5, suggesting the potential application of this chemically modified bioadsorbent for the removal of cationic contaminants in aqueous media.

Synthesised and modified zeolite for effective management of beryllium contaminants in aqueous media under different conditions

The effective management of beryllium (Be) in solution is not well established. In this study, zeolite was synthesised from coal fly ash (CFA) and further modified to enhance Be sorption. Results indicated zeolite NaP1 was effectively synthesised, and cross-linked chitosan was grafted in/on the zeolite structure during modification. The Brunauer, Emmett, and Teller (BET) surface area substantially increased from 1.05 m2/g in CFA to 94.0 m2/g in the synthesised zeolite (SZ). Furthermore, the modified zeolite (MZ) showed improved functionality as a reactive site for Be sorption. A comparative sorption study revealed inferior sorption (11.3 %) and higher desorption (56.1 %) of Be using CFA than the sorption using SZ (93.0 % sorption, 2.9 % desorption) and MZ (93.0 % sorption, 1.5 % desorption). Consequently, SZ and MZ exhibited higher sorption efficacy than commercial zeolite (57.4 %) and other commercial sorbents. At an experimental pH of 5.5 [relevant to the pH of Little Forest Legacy Waste Site (LFLS) soil, a representative site for potential Be contamination], MZ showed higher sorption than SZ. The higher sorption in MZ resulted from its elevated ligand complexation [with nitrogen (N), phosphorous (P), and oxygen (O)] and some ion exchange (with Na+, -NH3+, and H+ ions) mechanisms. Moreover, increased sorption (up to 99 %) was observed using colloidal soil solution (CSS) collected from LFLS soil to simulate field conditions after extensive rainfall. Different environmental factors (e.g. pH, temperature, time, CSS, concentrations of sorbate, and sorbent) regulated Be sorption. The sorption mechanism was best described by the Langmuir model, and the pseudo-second-order kinetic model (R2 = 0.999). Moreover, the sorption reaction was spontaneous (ΔG = -Ve), enthalpically, and entropically influenced. Desorption hysteresis (ndesorption/nsorption < 1) suggested irreversible sorption, and the chemisorption mechanism of Be was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis.

Dual-wavelength UV degradation of bisphenol A and bezafibrate in aqueous solution using excilamps (222, 282 nm) and LED (365 nm): yes or no synergy?

Dual-wavelength ultraviolet (DWUV) irradiation can lead to a synergistic effect in terms of accelerated degradation of emerging organic contaminants in aqueous media. This study compared the kinetics of single-wavelength and DWUV degradation of bisphenol A (BPA) and bezafibrate (BZF) in model aqueous solution using KrCl (222 nm), XeBr (282 nm) excilamps and LED (365 nm). Three novel dual combinations (222 + 282, 222 + 365 and 282 + 365 nm) were examined toward the potential synergy in direct photolysis and advanced oxidation processes (AOPs) using potassium persulfate and hydrogen peroxide. Kinetic comparison showed that the time- and fluence-based synergy did not occur in the dual combinations selected. Meanwhile, the single-wavelength UV treatment using KrCl excilamp was found to be highly efficient for degradation of target contaminants. At a given dosage of oxidants, the UV/S2O8 2− process exhibited higher performance than the UV/H2O2 one, attaining higher degradation rates and requiring lower UV fluences for 90% removal. This study demonstrates that the catalyst-free UV/S2O8 2− process using KrCl excilamp has a high potential for efficient removal of such organic contaminants from real waters with low turbidity.

Activation of peroxymonosulfate by S-scheme Bi2S3/doped gCN heterostructure photocatalyst for highly efficient visible light driven tetracycline degradation: Insights into reaction mechanisms

A solid state microwave (MW) assisted hydrothermal method was used to prepare S-scheme heterojunction composite Bi2S3@doped gCN (BS@CN). TC was degraded upto 99.9 % under 20 min visible light, with synergistic action of 0.2 g/L catalyst having 10 wt% Bi2S3 (BS(10)@CN) and 1.5 g/L PMS, for initial TC concentration of 50 mg/L, exhibiting first order rate constant (kapp): 0.215 min−1. The modulation of band-structure due to the generation of heterojunction, coupled with different surface-bound redox cycles, i.e.,Co2 +/Co3 +surf.,Ce3 +/Ce4 +surf. andBi3 +/Bi4 +surf., helped the charge migration, separation of excited e-/h+ and production of reactive species, like,SO4∙-,∙OH,O2∙-,O21, etc., that played important roles towards TC degradation. Band-structure determination, XPS analysis and other characterizations revealed the formation of S-scheme configuration and corresponding surface-bound metastable complexes towards self-regeneration and excellent catalytic activity of the composite, even in the contaminated real-life surface water sources. Extensive intermediate analysis was carried out to develop a detailed TC degradation pathway. The BS@CN photocatalyst can be recycled multiple times, without significant loss of photocatalytic activity (∼88 % TC degradation after 5 cycles). This study demonstrated the design and fabrication of metal oxide doped gCN/metal chalcogenide-based heterojunction photocatalysts that have potential applications towards the removal of refractory contaminants in aqueous medium.

Development of perceptive multi-analyte sensing platform based on fluorescent CdS QDs for selective and sensitive assay of virulent contaminants in aqueous medium

Relentless discharge of organic pollutants into the aqueous realm, including antibiotics, pesticides and nitroaromatic explosives, has necessitated world-wide attention for trace level monitoring of organic pollutants to safeguard water resources. This work aims to develop a multi-analyte fluorescent probe based on the biocompatible chitosan capped CdS QDs (CTS-CdS QDs) for the detection of environmentally deleterious organic pollutants. The facile aqueous chemical approach was opted for the fabrication of CTS-CdS QDs and their structural and morphological features were effectually evinced by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The distinct fluorescent characteristics of CTS-CdS QDs showed an unprecedented selectivity towards nitrophenolic explosives (p-nitrophenol (PNP), 2,4-dinitrophenol (2,4-DNP), picric acid (PA)), fluoroquinolones (ofloxacin (OLX), nor-ofloxacin (NOLX), levofloxacin (LVX)) and organochlorine pesticide (dicofol (DCF)) in waste water. Moreover, extremely low limit of detection was attained by CTS-CdS QDs for each detected analyte i.e., PNP (7.6 µM), 2,4-DNP (3.5 µM), PA (4.2 µM), OLX (0.006 µM), NOLX (0.026 µM), LVX (0.084 µM) and DCF (0.24 µM). Benefiting the outstanding characters of fluorescent probe in terms of high sensitivity, long fluorescent stability, quick response to targeted analytes, these were also successfully employed for trace level detection of organic pollutants in real samples analysis and excellent recoveries of 90–105% were achieved for spiked water samples. Through this work, green CTS-CdS QDs has been reported first time for the detection of nitrophenolic explosives, fluoroquinolone antibiotics and DCF pesticide in aqueous samples using a single probe.

Studies towards the adsorption of sulphate ions from acid mine drainage by modified attapulgite clays

The lack of access to safe drinking water has been a global crisis for the longest time, which has encouraged researchers to improve existing technologies or create new strategies to address issues associated with water pollution from both inorganic and organic pollutants. Adsorption and photodegradation are amongst the simple, cost-effective and environmentally durable methods applied in wastewater treatment. The chemistry and applications attapulgite clays receive ongoing attention in removal of contaminants from water due to their fascinating unique remarkable adsorption properties as well as their economic appeal, attapulgite clays have been extensively studied for the adsorption of various contaminants in aqueous media. In this study, the removal of sulphate ions from Acid Mine Drainage (AMD) using modified attapulgite by electrolyte (BaCl2) and two surfactants viz., hexadecyltrimethylammonium bromide (HDTMA), and trimethyldecylammonium bromide (TDTMA) was investigated. The study is the first to investigate and compare all three modified attapulgite by electrolyte (BaCl2) and two surfactants viz., hexadecyltrimethylammonium bromide (HDTMA), and trimethyldecylammonium bromide (TDTMA) and the factors that affecting removal of sulphate from AMD. A scanning electron microscope (SEM), X-ray diffraction (XRD) patterns, and a Fourier Transform Infrared (FTIR) spectrometer were used to analyse and validate the modified attapulgite clays. Batch adsorption studies were then carried out using the modified attapulgite clays, and the influence of various parameters influencing sulphate ion recovery, such as contact time, temperature, and solids loading, was investigated. At 25 °C, sulphate ion removal rates of 75% were obtained using BaCl2-modified attapulgite at a solid loading of 10% (m/v).TDTMA and HDTMA-modified attapulgites followed, with ion recovery of 69 and 16%, respectively, at a solid loading of 200% (m/v). These results suggest that BaCl2 was the most effective ionic surfactant when used to modify attapulgite clay for sulphate ion removal, and was therefore chosen for downstream studies. When the reaction temperature was increased to 35 °C and 45 °C to investigate the influence of temperature, it was discovered that the removals of sulphate ions were reduced to 66 and 64%, respectively. These results demonstrated that increasing the temperature has a negative impact on the removal of sulphate ions. The Temkin adsorption isotherm and the second-order kinetic model were found to have a very significant correlation with the results, implying that they best describe the experimental data. The activation energy of 23.7 kJ/mol clearly showed that chemisorption was the primary sulphate removal method. The results of this investigation demonstrated that BaCl2-modified attapulgite clay was a good adsorbent for the efficient adsorption of sulphate ions from AMD.

Degradation of Sulfamethoxazole Using a Hybrid CuOx–BiVO4/SPS/Solar System

In recent years, advanced oxidation processes (AOPs) demonstrated great efficiency in eliminating emerging contaminants in aqueous media. However, a majority of scientists believe that one of the main reasons hindering their industrial application is the low efficiencies recorded. This can be partially attributed to reactive oxygen species (ROS) scavenging from real water matrix constituents. A promising strategy to cost-effectively increase efficiency is the simultaneous use of different AOPs. Herein, photocatalysis and sodium persulfate activation (SPS) were used simultaneously to decompose the antibiotic sulfamethoxazole (SMX) in ultrapure water (UPW) and real water matrices, such as bottled water (BW) and wastewater (WW). Specifically, copper-promoted BiVO4 photocatalysts with variable CuOx (0.75–10% wt.) content were synthesized in powder form and characterized using ΒΕΤ, XRD, DRS, SEM, and HRTEM. Results showed that under simulated solar light irradiation alone, 0.75 Cu.BVO leads to 0.5 mg/L SMX destruction in UPW in a very short treatment time, whereas higher amounts of copper loading decreased SMX degradation. In contrast, the efficiency of all photocatalytic materials dropped significantly in BW and WW. This phenomenon was surpassed using persulfate in the proposed system resulting in synergistic effects, thus significantly improving the efficiency of the combined process. Specifically, when 0.75 Cu.BVO was added in BW, only 40% SMX degradation took place in 120 min under simulated solar irradiation alone, whereas in the solar/SPS/Cu.BVO system, complete elimination was achieved after 60 min. Moreover, ~37%, 45%, and 66% synergy degrees were recorded in WW using 0.75 Cu, 3.0 Cu, and 10.0 Cu.BVO, respectively. Interestingly, experimental results highlight that catalyst screening or process/system examination must be performed in a wide window of operating parameters to avoid erroneous conclusions regarding optimal materials or process combinations for a specific application.

Mn2O3@Mn5O8 as an efficient catalyst for the degradation of organic contaminants in aqueous media through sulfite activation

Less-toxic, cost-effective, stable, and highly efficient catalysts for sodium sulfite (S(IV)) activation are required to degrade organic pollutants from wastewater. Herein, we report the facile thermal synthesis of Mn2O3@Mn5O8 that activates S(IV) more efficiently than other Mn and transition-metal oxides. Mn2O3@Mn5O8 exhibits good performance and long-term stability for eliminating various contaminants from aqueous media, including phenol, bisphenol A, nitrobenzene, 2,4-dichlorophenol, and acetaminophen. Its high performance is attributed to its multivalency, unique architecture, surface hydroxyl groups (–OH), and high surface area. X-ray diffractometry and high-resolution transmission electron microscopy revealed that Mn2O3@Mn5O8 comprises well-combined cubic Mn2O3 and monoclinic Mn5O8 crystalline structures, whereas electron paramagnetic resonance spectroscopy and scavenging tests showed that SO5•−, SO4•−, and •OH radicals are generated during S(IV) activation, with SO3•− as a precursor. The mixed-valence state provides effective and favorable electron transfer via Mn redox cycling (Mn(II) ↔ Mn(III) ↔ Mn(IV)), improving the S(IV) activation performance and catalytic activity. Mn2O3@Mn5O8/S(IV) system shows stable performance in the 3.0–7.0 pH range. Density functional theory calculations confirmed the higher catalytic activity as indicated by high –OH adsorption energy and significant inter-charge transformation. This study provides new insights and strategies for the activation of S(IV) using less-toxic metal oxides as catalysts and broadens the scope of heterogeneous Mn-based catalysts and S(IV) chemistry in real-world applications, particularly for the treatment of wastewater.

Efficient simultaneous removal of tetracycline and cefazolin from aqueous solution using a novel adsorbent based on zero-valent iron nanoparticles supported by montmorillonite and graphene oxide: isotherms, kinetic, and thermodynamic studies

ABSTRACT In recent years, antibiotics in aqueous solutions have drawn extensive attention due to their harmful effect on human health and the environment. In this study, efficient and rapid adsorption of two antibiotics, including tetracycline (TC) and cefazolin (CFZ) on synthesised montmorillonite (Mt)/nano zero-valent iron (nZVI)/graphene oxide (GO) from aqueous solutions was studied. The prepared adsorbent was characterised by scanning electron microscope (SEM), energy dispersive X-Ray (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and vibrating sample magnetometer (VSM). One-factor-at-a-time (OFAT) method was used to optimise the experimental factors. The maximum removal percentage was achieved at pH of 7, an adsorbent dosage of 0.4 g, contact time of 7 min = TC and 10 min = CFZ, initial concentration of 5 mg L−1, and a temperature of 298 K. The evaluation of isotherm models indicated that the Langmuir isotherm with a coefficient of determination (R2) value of 0.9992 for both antibiotics was selected as the best fitting model to describe the adsorption process. The maximum adsorption capacities (qmax) of Mt-nZVI-GO were obtained at 43.24 mg g−1 for TC and 20.36 mg g−1 for CFZ. Furthermore, the pseudo-second-order (PSO) kinetic model fitted well for TC (R2 = 0.9937) and CFZ (R2 = 0.9997). Thermodynamic parameters, i.e. adsorption Gibbs free energy (ΔG0), standard enthalpy (ΔH0), and standard entropy (ΔS0) were estimated. It was found that the adsorption had spontaneous and exothermic in nature. The results revealed that Mt-nZVI-GO could be used as a simple, efficient, and eco-friendly adsorbent for the simultaneous removal of contaminants in aqueous media.

Doping of TiO2 Using Metal Waste (Door Key) to Improve Its Photocatalytic Efficiency in the Mineralization of an Emerging Contaminant in an Aqueous Environment

Photocatalysis is an effective advanced oxidation process to mineralize recalcitrant contaminants in aqueous media. TiO2 is the most used photocatalyst in this type of process. To improve the deficiencies of this material, one of the most used strategies has been to dope TiO2 with metallic ions. Chemical reagents are often used as dopant precursors. However, due to the depletion of natural resources, in this work it was proposed to substitute chemical reagents and instead use a metallic residue (door key) as a doping precursor. The materials were synthesized using the sol–gel method and calcined at 400 °C to obtain the crystal structure of anatase. The characterization of the materials was carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), scanning electron microscopy–energy-dispersive X-ray analysis (SEM-EDX) methods X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The results obtained indicate that Cu+/Cu2+ and Zn2+ ions coexist in the support, which modifies the physicochemical properties of TiO2 and improves its photocatalytic efficiency. The synergistic effect of the dopants in TiO2 allowed the mineralization of diclofenac in an aqueous medium when T-DK (1.0) was used as photocatalyst and simulated solar radiation as an activation source.

Environmentally friendly synthesis of silicon dioxide nanoparticles and their application for the removal of emerging contaminants in aqueous media

The highly detrimental potential effects that emerging contaminants have for the environment and human health demand the development of sustainable technologies to eliminate these pollutants. In this work, an eco-friendly approach was followed to synthesize S1O2 nanoparticles to be used to remove caffeine and triclosan from synthetic waters. Rice husk was the precursor used, which was subjected to acid leaching treatments using acetic and oxalic acids, and pyrolysis for 2 h at 700 °C. The resulting powders were characterized by X-ray diffraction, Raman and infrared spectroscopies, the Brunauer-Emmett-Teller method, and scanning and transmission electron microscopy. The particles synthesized were amorphous, had an average size between 4.6 and 9.6 nm, and specific surface areas between 208 and 223 m2/g. The adsorptive performance of the nanosilica obtained using acetic acid was studied by batch tests. The optimum dosage, maximum removal efficiencies and maximum adsorption capacities were 8 g/L, 76%, and 2.74 mg/g, and 24 g/L, 48%, and 0.75 mg/g for triclosan and caffeine, respectively. The data collected fitted the Sips isotherm model, and the pseudo-second and -first order kinetics models, for triclosan and caffeine, respectively. The promising results obtained open the possibility of using the synthesized nanomaterials for removing a variety of toxic and recalcitrant pollutants.

Mannich-mediated synthesis of a recyclable magnetic kraft lignin-coated copper nanostructure as an efficient catalyst for treatment of environmental contaminants in aqueous media

Recently, the fabrication of heterogeneous catalysts using biopolymers has been considered due to some advantages such as biodegradability, easy handling, high efficiency and so on. In this work, 5-amino-1H-tetrazole modified kraft lignin/Fe3O4 supported highly catalytic active copper complex (Fe3O4@LigA/Cu) has been synthesized as a novel catalyst. The support was prepared by the Mannich reaction of 5-amino-1H-tetrazole and kraft lignin. The prepared catalyst was characterized by different techniques including Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectrometry (EDX), elemental mapping, Brunauer-Emmett-Teller (BET) and vibrating sample magnetometry (VSM). The Fe3O4@LigA/Cu catalyst was used in the catalytic reduction of organic pollutants such as 4-nitrophenol (4-NP), methylene blue (MB), and congo red (CR) using sodium borohydride (NaBH4) as the reducing agent and the catalytic efficiency was studied by UV–visible spectroscopy. Fe3O4@LigA/Cu catalyst showed high yield (˃ 99%) in the reduction of 4-NP in four min. Moreover, Fe3O4@LigA/Cu catalyst showed good recyclability and reusability. This work provides a simple method for the preparation of lignin based catalysts with high catalytic activity and easy recovery to degrade organic pollutants from aqueous solution.

Bifunctional copper zinc bimetallic tungstate nanoparticles decorated reduced graphene oxide (CuZnWO4/rGO) for high-performance photocatalytic and supercapacitor application

In the present work, synthesis of bimetallic copper zinc tungstate (CuZnWO4) nanoparticles with reduced graphene oxide (CuZnWO4/rGO) via one-step hydrothermal technique was attempted. The synthesized CuZnWO4/rGO composite are characterized by Fourier transform infrared spectroscopy (FTIR), Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis diffuse reflectance spectroscopy (UV DRS) and Photoluminescence (PL). The photocatalytic performance is examined by the degradation of methylene blue (MB) dye under visible light irradiation. The MB dye is almost 73% degraded within 80 min. Further, the electrochemical performance of hybrid CuZnWO4/rGO composite showed the specific capacity (SC) of 480 F/g at 4 A/g in 6 M KOH electrolyte with excellent cyclability conserving a capacitance retention of 127% after 5000 cycles due to increase diffusion of electrolyte ions to the electrode materials. These results support the hybrid CuZnWO4/rGO composite as an appropriate electrode material for high-performance SCs electrode and an auspicious catalyst for the degradation of dye (organic) contaminants in aqueous media.

Composite carbon materials from winery composted waste for the treatment of effluents contaminated with ketoprofen and 2-nitrophenol

The present work consisted of preparing and characterizing composite carbon materials (WRCC) from raw winery residues (WR) activated with zinc chloride to produce a carbon adsorbent. The WRCC was used for the adsorption of emerging contaminants in aqueous media. The WRCC presented a morphology with favorable characteristics for the adsorption process, giving an abundant porous structure with pores of different sizes. The results show the WRCC’s effectiveness, presenting surface area values (227 m2 g−1) and total pore volume (0.175 cm3 g−1). The general order kinetic model predicted the experimental curves sufficiently. The Sips model better described the two adsorbates' equilibrium data, with maximum adsorption capacities of 376.0 and 119.6 mg g−1 for 2-nitrophenol and ketoprofen, respectively. The WRCC carbon material was also highly efficient, with maximum removal of 81.4% and 94% in 1000 mg L−1 of the compounds 2-nitrophenol and ketoprofen. Finally, the prepared material has essential characteristics that make it an efficient adsorbent in treating effluents with emerging contaminants.

Synthesis and characterization of Pd(0) Schiff base complex supported on halloysite nanoclay as a reusable catalyst for treating wastewater contaminants in aqueous media

In this study, a novel and recyclable heterogeneous Pd(0) catalyst was synthesized via the immobilization of a Pd(0)-Schiff base complex onto the surface of halloysite (HaI) nanoclay and fully characterized by FTIR, TEM, TG/DTG, FE-SEM, EDS, elemental mapping, XPS and XRD. The catalytic role of Pd NPs@HaI nanocatalyst was then evaluated in the reduction of 4-nitrophenol (4-NP), congo red (CR), K3[Fe(CN)6] and methyl orange (MO) by employing NaBH4 as the reducing agent at room temperature. The main advantages of using Pd NPs@HaI catalyst include an easy experimental procedure, short reaction time, low loading of the catalyst, and the ability to use various contaminants. The ensuing Pd NPs@HaI demonstrated superior catalytic prowess (100% conversion within a few seconds for the aforementioned pollutants), excellent stability and superior recyclability. The results displayed that the nanocatalyst could be reused by simple filtration for several times, demonstrating high recyclability and excellent chemical stability.

Synthesis of nZVI-Ni@BC composite as a stable catalyst to activate persulfate: Trichloroethylene degradation and insight mechanism

In Fenton-like oxidation processes, the use of biochar (BC) as support material for the nanoscale zero valent iron-nickel (nZVI-Ni) bimetallic particles attained much attention to activate persulfate (PS) for TCE degradation in aqueous medium. In present work, nZVI-Ni@BC particles with nZVI-Ni to BC mass ratio of 1:5 exhibited excellent results (> 99 % ± 0.24) for TCE degradation. The physico-chemical characteristics, surface morphologies, and elemental mapping of the synthesized nZVI-Ni@BC particles investigated through SEM, EDX, TEM, XPS, XRD, BET and FTIR spectroscopy. For the nZVI-Ni@BC-persulfate system, the effects of PS concentration, initial pH, inorganic ions and natural organic matter (NOM) on TCE degradation were evaluated. Batch experiments revealed that complete removal of TCE (> 99 % ± 0.25) was attained at 250 mg L−1 of nZVI-Ni@BC and 4.0 mM PS dosages at pH 3.49 ± 0.55. Scavenging and electron paramagnetic resonance (EPR) verified the dominant role of both SO4ˉ and OH radicals in acidic environment for degradation of TCE. Moreover, high level of carbonate, bicarbonates and NOM inhibited the overall TCE oxidation reaction. In summary, these results suggested that nZVI-NI@BC composite was an alternative, economic and promising catalyst for the activation of PS to degrade chlorinated contaminants in aqueous medium.

Estudio de la movilidad de nanofluidos estables basados en hierro para remediación in situ de contaminantes inorgánicos

Las nanopartículas de hierro cerovalente (FeNPs) se han empleado para la remoción de una gran variedad de contaminantes en medio acuoso, transformándolos en especies de menor toxicidad mediante mecanismos de adsorción superficial y reacciones rédox. En tratamientos de remediación in situ de aguas subsuperficiales se inyectan como nanofluidos (NFs), donde las suspensiones de FeNPs deben estabilizarse para evitar su precipitación y favorecer su transporte. En este trabajo se prepararon nanofluidos estables a partir de FeNPs empleando estabilizantes como carboximetilcelulosa (CMC) o goma xántica (GX), y se evaluó su movilidad en columnas rellenas de lecho poroso, a escalas de laboratorio y piloto. Los parámetros del lecho se obtuvieron por modelado de las curvas de ruptura de un trazador de NaCl, empleando un software específico. Los NFs mostraron buena movilidad, mientras que las FeNPs sin estabilizar quedaron retenidas en el medio poroso. Con el objetivo de dilucidar completamente los mecanismos de transporte y los modelos de flujo actuantes se comenzó también con la caracterización reológica de los NFs, encontrándose resultados iniciales interesantes. Mediante una combinación adecuada de los experimentos de movilidad en columna, el modelado y la caracterización, se encontraron resultados alentadores que ayudarán a diseñar un sistema de inyección in situ de los NFs.