Apparent Degradation Rate Research Articles

Substitution of raw lucerne with raw citrus lemon by-product in silage: In vitro apparent digestibility and gas production.

Fruit pomace addition to lucerne silage could rapidly reduce silage pH creating an acidic environment and thus maybe preventing spoilage. However, the purpose of this study was to investigate the effect of different rates of inclusion of citrus lemon by-products on lucerne. In this study, the following five different treatments were prepared: L0 (control) with 100% lucerne; L25 (75% lucerne with 25% lemon pomace); L50 (50% lucerne with 50% lemon pomace); L75 (25% lucerne with 75% lemon pomace); and L100 (100% lemon pomace). After ensiling, the chemical composition, nutritive value, stability, in vitro apparent digestibility, and gas production of silage were determined. The dry matter (DM) content was higher for lemon pomace substitution equal to or exceeded 50% (P < 0.01). Crude protein, on the contrary, decreased (P < 0.01) over the same percentage of substitution. The L100 and L75 treatments showed higher DM apparent disappearance rate and lower (P < 0.05) crude protein and neutral detergent fiber apparent degradation rate vs. L0. Lemon pomace could be used at high inclusion level in lucerne silage, allowing the preservation of this by-product all the year, improving some chemical silage characteristics, and reducing proteolytic processes that usually happen on lucerne silage. Moreover, the in vitro apparent digestibility and gas production results showed that a partial substitution of lucerne with lemon pomace is able to improve silage digestibility.

Ultra-short chain fluorocarboxylates exhibit wide ranging reactivity with hydrated electrons

Recent reports demonstrate that technologies generating hydrated electrons (eaq−; e.g., UV-sulfite) are a promising strategy for destruction of per- and polyfluoroalkyl substances, but fundamental rate constants are lacking. This work examines the kinetics and mechanisms of eaq− reactions with ultra-short chain (C2–C4) fluorocarboxylates using experimental and theoretical approaches. Laser flash photolysis (LFP) was used to measure bimolecular rate constants (k2; M−1 s−1) for eaq− reactions with thirteen per-, and for the first time, polyfluorinated carboxylate structures. The measured k2 values varied widely from 5.26 × 106 to 1.30 × 108 M−1s−1, a large range considering the minor structural changes among the target compounds. Molecular descriptors calculated using density functional theory did not reveal correlation between k2 values and individual descriptors when considering the whole dataset, however, semiquantitative correlation manifests when grouping by similar possible initial reduction event such as electron attachment at the α-carbon versus β- or γ-carbons along the backbone. From this, it is postulated that fluorocarboxylate reduction by eaq− occurs via divergent mechanisms with the possibility of non-degradative pathways being prominent. These mechanistic insights provide rationale for contradictory trends between LFP-derived k2 values and apparent degradation rates recently reported in UV-sulfite constant irradiation treatment experiments.

Insights into the Kinetics, Theoretical Model and Mechanism of Free Radical Synergistic Degradation of Micropollutants in UV/Peroxydisulfate Process

The degradation of acyclovir (ACY) and atenolol (ATL) in the UV/peroxydisulfate (UV/PDS) process has been systematically considered, focusing on the degradation kinetics, theoretical models, and reaction pathways via applying a microfluidic UV reaction system. The removal efficiencies of ACY and ATL were &gt;94.8%, and the apparent degradation rate constants (kobs) were 0.0931 and 0.1938 min−1 at pH 6.0 in the UV/PDS system. The sulfate radical (SO4•−) and hydroxyl radical (•OH) were identified as the major reactive radicals. The pH-dependent reaction rate constants of ACY and ATL with •OH and SO4•− were measured via the competing kinetics. Meanwhile, the contributions of •OH and SO4•− for ACY and ATL degradation were calculated by the radical steady-state hypothesis, and the results revealed that SO4•− occupied a decisive position (&gt;84.5%) for the elimination of ACY and ATL. The contribution of •OH became more significant with the increasing pH, while SO4•− was still dominant. Moreover, ACY and ATL degradation performance were systematically evaluated via the experiments and Kintecus model under different operational parameters (Cl−, Br−, HCO3−, NOM, etc.) in the UV/PDS process. Furthermore, the plausible reaction pathways of ACY and ATL were elucidated based on the Fukui function theory and ultra-performance liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) analysis. The UV/PDS process has been demonstrated to be an efficient and potential application for micropollutants mitigation.

Nitrogen-doped oxidized activated carbon as efficient metal-free bifunctional material for bisphenol removal: A tuning of surface chemistry

Nitrogen modified oxidized activated carbon (N-OAC) was prepared by nitric acid oxidation and ammonia hydrothermal treatment of activated carbon. The surface functional groups of AC were changed by controlling the synthetic conditions and characterized. It was found that oxygen and nitrogen functional groups was introduced on the surface of AC. The deeper degree of oxidation was in favour of N doping. With well-suited amount of oxygen and nitrogen modification, the adsorption and activation ability toward persulfate could be enhanced simultaneously. The adsorption experiment showed that the maximum adsorption capacity (qm) of N-OAC for bisphenol A (BPA) obtained from a Langmuir isotherm was 147 mg g−1 at 298 K, which was about 1.23 and 1.5 times than that of AC (121 mg g−1) and N-free-OAC (108 mg g−1). N-OAC could also activate persulfate, producing strong oxidizing sulfate radicals. The apparent degradation rate constant of BPA on N-OAC was 0.039 min−1, being about 39 times than that (0.001 min−1) on AC. After adsorption equilibrium within 120 min, the use of N-OAC (240 mg L−1) and persulfate (4 mmol L−1) almost completely removed the added bisphenols (60 mg L−1) at pH 6.6 within 60 min. A synergistic effect and correlation between the adsorption ability, catalytic performance and chemical structures of N-OAC was discussed.

ZIF-8-derived single-atom Cu and N co-coordinated porous carbon as bifunctional material for SMX removal

Single-atom Cu and N co-coordinated porous carbon (Cu-N-C) was synthesized by hydrothermal-calcination using zinc zeolite imidazole frameworks (ZIF-8) as the precursor. The catalyst showed excellent adsorption and catalytic ability due to the ideally-dispersed single atomic copper sites and the unique nitrogen-doped porous carbon. The complete removal of sulfamethoxazole (SMX, 18 mg/L) could be achieved within 40 min of pre-adsorption and 25 min of oxidative degradation in the present of peroxymonosulfate (PMS). The adsorption capacity of Cu-N-C (0.2 g/L) was evaluated to be 58.69 mg/g. The apparent degradation rate constant (k) of SMX on Cu-N-C was 0.155 min-1, which was 14.1 times faster than that on N-C (0.011 min-1). From the activation mechanism, it was found that CuN units acted as the main active sites in Cu-N-C for PMS activation. EPR analysis and quenching experiments verified that the reactive oxygen species (ROSs) of SO4·- and 1O2 were involved in the decomposition and mineralization of SMX. This work provides a new perspective for the development of Fenton-like single-atom catalysts.

Degradation pathways and kinetics of chloroacetonitriles by UV/persulfate in the presence of bromide

Chloroacetonitriles (CANs) are highly toxic nitrogenous disinfection by-products (N-DBPs), which frequently appear in water supply systems and have attracted widespread attention. UV/persulfate (PS) is an effective method to degrade CANs. Bromide (Br−) is widespread in aquatic environments and reacts with oxidative radicals to produce secondary reactive bromine species (RBS), which affects the degradation of CANs by UV/PS. It was found that the degradation of CANs was highly inhibited by Br−. The apparent first-order reaction rate constants of monochloroacetonitrile (MCAN), dichloroacetonitrile (DCAN) and trichloroacetonitrile (TCAN) decreased from 2.63 × 10−3, 2.00 × 10−3 and 8.66 × 10−4 s−1 to 2.58 × 10−4, 1.61 × 10−4 and 1.59 × 10−4 s−1, respectively after adding 20 μM of Br−. HO• was the main radicals contributing to the degradation of CANs when the concentration of Br− was less than 10 μM, compared with SO4•− and direct photolysis. When the concentration of Br− was up to 20 μM, the contributions of RBS accounted for 85.7%, 90.7% and 89.9% of the apparent degradation rate constants of CANs, respectively. During the reaction, about 65% of nitrogen atoms were transformed into NO3− by the CC bond cleavage and oxidation. The yields of Cl− by dechlorination reaction accounted for 83.5%, 71.0% and 41.2% of the chlorine contents in MCAN, DCAN and TCAN, respectively. It was verified that CANs react with free bromine (HOBr) to produce bromochloroacetonitrile (BCAN). DCAN and TCAN are hydrolyzed to produce corresponding haloacetamides (HAMs), which are further reacted with HOBr to produce bromodichloroacetic acid (BDCAA). Furthermore, the generation of bromate was also worth noting via the oxidation of Br− in the UV/PS system.

Mesoporous TiO2 enhanced by anchoring Mn3O4 for highly efficient photocatalyst toward photo-oxidation of ciprofloxacin

We describe the synthesis of mesoporous Mn3O4/TiO2 nanocomposites in the occurrence soft template. TEM images exhibited the Mn3O4/TiO2 nanocomposites homogeneous morphology with a particle size of ∼10–15 nm with close contact between TiO2 anatase and Mn3O4 crystals. The mesoporous Mn3O4/TiO2 nanocomposites were assessed toward degradation of ciprofloxacin (CIP) under visible illumination, which achieved 98.6% CIP degradation within 120 min. The degradation efficiency over porous 3% Mn3O4/TiO2 was greater 18 fold than that bare TiO2. The apparent degradation rate of the optimum 3% Mn3O4/TiO2 photocatalyst was fostered 22 folds higher than that of bare TiO2 NPs. Interestingly, the enhanced photocatalytic ability for Mn3O4/TiO2 heterojunction was significantly referred to the high absorption of visible light, synergistic effect and the unique structure with large surface area, which improved the CIP adsorption on porous Mn3O4/TiO2. Besides, the Mn3O4/TiO2 photocatalysts displayed stability and recyclability toward degradation of CIP for 10 h illumination. The photoelectrochemical and photoluminescence measurements of Mn3O4/TiO2 nanocomposites revealed an enhanced light-harvesting and effective electron-holes separation compared with bare TiO2. The prospective mechanism for degradation of CIP over Mn3O4/TiO2 heterojunction was presented.

Hierarchical ZnO/MXene (Nb2C and V2C) heterostructure with efficient electron transfer for enhanced photocatalytic activity

Recently, MXene has attracted much attention as photocatalysts for efficient pollutant degradation in the field of environmental remediation but a rapid recombination of photogenerated carriers usually leads to a decrease in the photocatalytic performance. Constructing a heterostructure is considered as an effective way to improve the catalytic performance of MXene-based photocatalysts due to the promoted interfacial electron transfer. In this work, the chimeric ZnO nanosheets with good carrier mobility were formed on the accordion-shaped MXene (Nb2C and V2C) surface to construct hierarchical ZnO/MXene heterostructure as a photocatalyst for dye degradation. The obtained ZnO/Nb2C and ZnO/V2C hierarchical structure exhibited excellent photocatalytic performance in the degradation of methylene blue (MB): the degradation rate reached 62.62% and 99.53%, respectively, after irradiation with ultraviolet light for 120 min. Also, the apparent degradation rate constants (k) were 0.00777 min−1 and 0.04317 min−1, respectively, which were 2.92 and 16.23 times higher than those of pure ZnO. This was probably attributed to the heterostructures between ZnO and MXene which could shorten the carrier transfer path, which could facilitate the transfer of photo-generated electrons from conduction band (CB) of ZnO to CB of MXene, thereby significantly improving the photocatalytic degradation efficiency. In addition, the ZnO/Nb2C and ZnO/V2C hierarchical structure showed good photocatalytic stability: the degradation rate remained at 58.6% and 97.3%, respectively, after 4 cycles while it only maintained at 22.0% for pure ZnO because the obtained ZnO/MXene hierarchical structure could provide uniform active sites on the surface and porous structure, preventing the aggregation of ZnO or MXene. Therefore, this work could provide a feasible design strategy to improve the catalytic performance of 2D photocatalysts and shed a light on the design of other photocatalysts.

Designing S-scheme Au/g-C3N4/BiO1.2I0.6 plasmonic heterojunction for efficient visible-light photocatalysis

A novel S-scheme Au/g-C3N4/BiO1.2I0.6 plasmonic heterojunction was constructed by calcining a mixture of flower-like BiOI and Au/g-C3N4 nanosheets for the first time. This Au/g-C3N4/BiO1.2I0.6 heterojunction exhibited excellent photocatalytic activity in bisphenol AF (BPAF) degradation and Cr(VI) reduction with high cycle stability under visible light irradiation. In particular, the photocatalytic performance of the optimum material developed (4-Au/g-C3N4/BiO1.2I0.6) can reach 0.0174 min−1 (apparent rate of BPAF degradation) and 0.0204 min−1 (apparent rate of Cr(VI) reduction), which were 6.5 and 3.7 times that of pristine g-C3N4, respectively. The high photocatalytic performance was due to the high efficiency of charge separation, the excellent light absorption of localized surface plasmon resonance (LSPR) caused by the Au deposition, and the formation of S-scheme heterojunctions, which maintained strong photocatalytic reduction and oxidation activity. Noticeably, the charge density difference and band offsets of the g-C3N4/BiO1.2I0.6 were calculated. The results revealed that an internal electric field (IEF) was created, which further demonstrated the formation of an S-scheme photocatalytic mechanism.

Insight into the multiple roles of nitrogen doped carbon quantum dots in an ultrathin 2D-0D-2D all-solid-state Z scheme heterostructure and its performance in tetracycline degradation under LED illumination

The rational design of an all-solid-state Z scheme composite through a single-step hydrothermal treatment by combining ultrathin defect engineered graphitic carbon nitride nanosheets (DCN), tungsten oxide hydrate nanoplates (W), and nitrogen doped carbon quantum dots (NCQDs) has been reported. For the first time, this study demonstrates that NCQD could successfully exfoliate g-C3N4 to produce few-layered thick g-C3N4 nanosheets, besides playing the role of an electron mediator in the composite. The 10%W/1%NCQD/DCN composite exhibited the highest photocatalytic tetracycline degradation efficiency under an 18 W LED illumination. It illustrated a 31.5, 7.7, and 5.2-times higher apparent degradation rate constant (0.044 min−1) than W, bulk g-C3N4, and DCN, respectively. Further, the composite exhibited an outstanding efficacy toward the degradation of various real water matrices. The composite demonstrated high stability and reusability. Furthermore, a plausible all-solid-state Z scheme charge carrier mechanism is proposed based on the results of the radical scavenging experiments.

Nitrogen-doped biochar as peroxymonosulfate activator to degrade 2,4-dichlorophenol: Preparation, properties and structure–activity relationship

Nitrogen-doped biochar (NCMs) has shown great potential as metal-free catalysts for persulfates. To understand the evolution law of properties of NCMs with preparation conditions, eleven NCMs were prepared and characterized by EA, BET, Raman, XPS, and conductivity. Surface area and conductivity can be improved by higher pyrolysis temperature and longer retention time. Distribution of nitrogen species of NCMs was greatly influenced by pyrolysis temperature. Subsequently, these NCMs were applied to activate peroxymonosulfate to degrade 2,4-dichlorophenol. A linear correlation of the initial apparent degradation rate constant (kobs) of 2,4-dichlorophenol with conductivity and ratio of graphitic N was newly established, revealing that conductivity and graphitic N of NCMs would be the key property deciding degradation efficiency of 2,4-dichlorophenol. Positive effect of conductivity can be ascribed to the mediated electron-transfer mechanism. Electron-transfer mechanism is also proved by quenching experiments and solvent deuterium isotope effect experiment. Graphitic N would be the main active site for PMS activation. Understanding the evolvement rule of properties of NCMs with preparation conditions combined with the correlations between reactivity and properties of NCMs is meaningful for preparation of nitrogen-doped biochar as well as the development of carbonaceous materials with high performance in persulfates-based advanced oxidation processes.

In-situ fabrication of novel BiOCl/Bi5O7I 2D/3D heterostructures with enhanced photocatalytic activity

A novel BiOCl/Bi5O7I (BOC-BOI) heterojunction was prepared by growing ultrathin 2D BiOCl nanosheets in situ on the surface of 3D Bi5O7I microspheres. The 2D/3D heterostructure of BOC-BOI composites inhibited the agglomeration of BiOCl nanosheets, and benefited the multiple reflection and refraction of light, which greatly enhanced the absorption and utilization of light. The 50-BOC-BOI composite showed 97.7% degradation efficiency of rhodamine B (RhB) after 70 min Xe light irradiation. And its apparent degradation rate constant (k) was 0.0377 min−1, being 4.9 and 15.1 times than that of pristine BiOCl (0.0077 min−1) and Bi5O7I (0.0025 min−1), respectively. The enhanced photocatalytic activity of BOC-BOI composites was attributed to stronger light capture ability, more abundant active sites and higher charge carrier separation efficiency, confirmed by UV-Vis DRS, SEM, TEM, BET, Zeta potential and electrochemical characterizations. The free radical capture experiments showed that the main active species in this system were holes (h+) and superoxide free radicals (·O2−). Combining the results of UV-Vis DRS and Mott-Schottky test, a reasonable type II heterojunction mechanism was proposed.

Reevaluation of the Reactivity of Superoxide Radicals with a Sulfonamide Antibiotic, Sulfacetamide: An Experimental and Theoretical Study

Superoxide radical (O2•–) is a ubiquitous reactive oxygen species in sunlit natural waters. Here, we selected sulfacetamide (SCT) as a representative sulfonamide antibiotic to investigate its reactivity with O2•–, as this reaction was reported to be fast with the rate constant k of 7.0 × 107 M–1 s–1. The degradation kinetics of SCT were first studied in the classic McDowell systems (i.e., ultraviolet, acetone, and alcohols) for optimal O2•– productivity. Comparison of the apparent first-order degradation rates (kapp) revealed that 70 mM acetone and 1 M isopropanol were optimal for kapp, but it was only ∼10% faster than the control. The small degree of enhancement of kapp led us to suspect its high reported reactivity with O2•–. Therefore, we reevaluated this reaction in organic and aqueous solutions by a suite of spectroscopic techniques, and all evidence indicated that the measured k values were 6 orders of magnitude smaller than the reported one. The low reactivity was also confirmed by theoretical calculations at the M06-2X level of theory. Our results are of practical and scientific importance for the holistic assessment of the role of O2•– in remediation and attenuation of organic contaminants in natural and engineered waters.

Highly dispersible graphitic carbon nitride: Synthesis and its 2-electron photocatalytic reduction activity of O2

Graphitic carbon nitride (g-CN) is a promising visible light-driven photocatalyst due to its favorable band gap. However, the limited number of active sites and rapid electron-hole recombination largely limit the photocatalytic efficiency of g-CN. This work provides a salt-template method (STM) to produce carbon nitride nanoparticles with high crystalline and dispersibility. 20–50 nm g-CN particles are achieved with high dispersion in aqueous phase, which permits a quasi-homogeneous aqueous photocatalytic oxidation and reduction conditions. It shows excellent photocatalytic activity for H2O2 generation and RhB degradation under visible light. An apparent H2O2 generation rate of 6.32 mmol·g−1·h−1 and an apparent RhB degradation rate constant (kapp) of 0.1707 min−1 were achieved on g-CN from salt-templated method, which are about 32 times and 2 times higher than that of g-CN derived from non-salt-template method, respectively. Increasing the crystallinity as well as reducing the g-CN nanoparticle size were found enhancing the electron-hole separation efficiency and resulting in more active sites. It offers a better and promising photocatalyst for H2O2 generation and organic pollution photodegradation.

Mechanistic investigation of photocatalytic degradation of Bisphenol-A using MIL-88A(Fe)/MoS2 Z-scheme heterojunction composite assisted peroxymonosulfate activation

In this study, a green synthesis method was employed to synthesize MoS2 incorporated MIL-88A(Fe) composite photocatalyst, MIL-88A(Fe)/MoS2 (MSMIL). Its catalytic property was utilized to degrade Bisphenol-A (BPA) in aqueous solution, using peroxymonosulfate (PMS) as oxidant under UV irradiation (intensity: 48 W). Doping of 20 wt% MoS2 was found to produce heterojunction with optimal activity, increased surface area (15.8 m2/g for MIL-88A(Fe) to 78.2 m2/g for MSMIL20) and abundant number of active sites. Insitu formation of intimate heterojunction, coupled with hierarchical porosity, conductive network, and abundant exposed active sites results efficient charge carrier migration to the catalyst surface and accelerates PMS activation to yield highly active radicals. X-ray photoelectron spectroscopy indicates that surface bound Fe3+/Fe2+ and Mo4+/Mo6+ redox interconversions play significant roles in surface adsorbed PMS activation. Scavenging experiments established that both radicalOH·,SO4·-,O2·-and non-radical O21,h+ based degradation pathways were responsible for BPA degradation. The excellent photocatalytic activity was due to the formation of suitable heterojunction which resists e-/h+ recombination, along with formation of an efficient Z-scheme heterojunction. LCMS/MS analysis was employed to determine the intermittent intermediates during BPA degradation and plausible pathways were designed. The apparent degradation rate constant of MSMIL(20)/PMS system was 0.083 min−1 which was 16.6 times and 25.4 times that of PMS alone and MSMIL(20) alone, in presence of UV irradiation. This work elicits critical insights towards synthesizing highly efficient and stable MOF based heterojunction photocatalyst and corresponding mechanistic elucidation of the catalytic activity towards degradative removal of refractory contaminants.

Removal and transformation of sulfamethoxazole in acclimated biofilters with various operation modes – Implications for full-scale application

The knowledge gaps regarding the degradation of sulfamethoxazole (SMX) in biofilters include the effect of aeration, constant feeding with readily biodegradable organic carbon and the presence of reactive media such as manganese oxides (MnOx). Thus, the goal of this study was to assess the removal of SMX in lab-scale biofilters with various operation variables: aeration, presence of MnOx as an amendment of filtering medium and the presence of readily biodegradable organic carbon (acetate). The sand used in the experiment as a filtering medium was previously exposed to the presence of SMX and acetate, which provided acclimation of the biomass. The removal of SMX was complete (>99%) with the exception of the unaerated columns fed with the influent containing acetate, due to apparent slower rate of SMX degradation. The obtained results suggest that bacteria were able to degrade SMX as a primary substrate and the degradation of this compound was subsequent to the depletion of acetate. The LC-MS/MS analysis of the effluents indicated several biotransformation reactions for SMX: (di)hydroxylation, acetylation, nitrosation, deamonification, S–N bond cleavage and isoxazole-ring cleavage. The relative abundance of transformation products was decreased in the presence of MnOx or acetate. Based on the Microtox assay, only the effluents from the unaerated columns filled with MnOx were classified as non-toxic. The results offer important implications for the design of biofilters for the elimination of SMX, namely that biofilters offer the greatest performance when fed with secondary wastewater and operated as non-aerated systems with a filtering medium containing MnOx.

Valorization of waste potato peel as iron adsorbent and catalyst in photo-oxidation: a sustainable waste management strategy

The study presents a unique approach for synergistic remediation of iron and methylene blue from aqueous media using waste potato peel. The waste potato peel was thermally modified at 550 oC to improve the properties desirable for adsorption (high-specific surface area and porosity). The thermally modified waste potato peel was employed in batch adsorption of iron from an aqueous medium at natural pH. Maximum iron adsorption of 202 mg g−1 was recorded for 7.5 mM iron concentration and 1 g L−1 of adsorbent dose. The iron adsorption on thermally modified waste potato peel followed pseudo-second-order kinetics and was best described by the Langmuir isotherm model. The iron adsorption was noted as endothermic, spontaneous, and thermodynamically feasible. The iron-adsorbed waste potato peel derived sorbent was used as a catalyst for photo-oxidative degradation of methylene blue in aqueous solution. The impacts of various process variables (initial dye concentration, catalyst dosage, and hydrogen peroxide concentration) on methylene blue degradation were analyzed. The highest methylene blue degradation of 91.76% was achieved using 1 mM of hydrogen peroxide and 3 g L−1 of iron-adsorbed catalyst in 15 min of exposure time to ultraviolet radiation. An apparent degradation rate of 0.116 min−1 was noted for the photo-degradation. The activation energy of the iron-adsorbed catalyst in the photo-oxidative of methylene blue was 12.97 kJ mol−1. The catalyst was noted to have good long-term stability. The low-cost catalyst obtained from waste peel was found to perform exceptionally well, relative to commercial activated carbon-based photo-catalysts.

Effects of surface structure and defect behavior on the magnetic, electrical, and photocatalytic properties of Gd-doped CeO2 nanoparticles synthesized by a simple chemical process

Magnetic, electrical, and photocatalytic characteristics of a series of nanoparticles (NPs) of Gd-doped CeO2 (GdxCe1-xO2 (100x% GDC); x = 0.03, 0.05, 0.10, and 0.20) were analyzed in correlation with their surface structure and defect behavior. The GDC NPs were synthesized by a simple chemical process through a polymer-based precursor. X-ray diffraction (XRD) studies confirmed the effective substitution of Gd3+ in the face centered cubic (fcc) lattice of the host matrix of CeO2. The optical band gap (Eg) and oxygen vacancies (VO) increased with Gd-doping as validated by UV–visible reflectance and Raman spectroscopy. Further analysis with X-ray photoelectron spectroscopy (XPS) substantiated the formation of non-stoichiometric CeO2 structure through Ce4+ → Ce3+ reduction to maintain charge neutrality after Gd-doping. Samples of 20% GDC processed at 400 °C, showed the highest saturation magnetization (MS) of 17.58 memu/g at room temperature. A maximum conductivity of 2.11 × 10−3 S/cm was recorded at 650 °C in air in the 20% GDC samples processed at 1100 °C. Using 20% GDC NPs processed at 400 °C, a typical value of apparent degradation rate constant (k) of 2.13 × 10−2 min−1 was obtained for methyl orange (MO) dye under UV–visible irradiation for 10 min.

Biodegradation of polyethylene by the bacterium Pseudomonas aeruginosa in acidic aquatic microcosm and effect of the environmental temperature

The main problem about plastic packaging after their use is the fate of the plastic waste disposed of into the environment. This study was carried out in aquatic microcosm and aimed at assessing the impact of the temperature of an acidic environment on the polyethylene degradation by the bacterium Pseudomonas aeruginosa, as well as the electrical conductivity of the medium and the temporal abundance dynamics of cells involved. Sterilized pieces of polyethylene of 0.08 g in weight were immersed in sterile mineral solutions of pH 5 in glass flasks containing P. aeruginosa cells at concentration adjusted to 186.103 CFU/100 µL. The whole was incubated at 7 °C, 23 °C, 37 °C and 44 °C for 10 days, 20 days and 30 days. Analysis after incubations showed that electrical conductivity which was 3386 µS/cm at the initial moment increased with an increase in incubation period. Its highest value 5476 µS/cm was noted at 44 °C after 30 days. The pH of solutions decreased. Its lowest value 4.11 was noted at 7 °C after 10 and 20 days. The apparent degradation rates of polyethylene fragments varied from 8.10−5 g/10days (at 7 °C and 23 °C) to 2.10−4 g/10days (at 44 °C). The highest percentage of weight loss of the polyethylene was 6.25% registered after 30 days at 44 °C. The apparent changing rates in cell abundance varied with variation in incubation temperature. It was positive under 7 °C and 23 °C reflecting relative cell growth, and negative under 37 °C and 44 °C reflecting relative cell inhibition. The highest relative apparent cell growth rate was 1.831 CFU/10days recorded at 23 °C and the highest relative apparent cell inhibition rate was 7.831 CFU/10days recorded at 44 °C. In solutions, the pH, electrical conductivity and the weight of the fragments varied significantly from one incubation temperature to another and from one incubation period to another (P<0.05). Cell abundances varied only from one incubation temperature to another (P <0.05). The biodegradation process of polyethylene by P. aeruginosa under various environmental conditions and the impact of the products released on cells remains incompletely understood.

Fabrication of silica supported Turkevich silver nanocomposites for efficient photocatalytic performance

Herein, a novel approach is reported to design metallodielectric silica (SiO2) supported Turkevich silver nanoparticles (Ag NPs) for direct fabrication of SiO2/Ag nanocomposites (NCs). The technique utilizes electrostatic interaction of ex situ synthesized amine-functionalized positively-charged SiO2 NPs and citrate-capped negatively-charged Ag NPs. The formation of nanoparticles was confirmed using various analytical techniques and explored for photocatalytic degradation of methyl orange (MO) at ambient temperature under sunlight irradiation. SiO2/Ag-NCs showed significant degradation of MO (94.50% in 40 min) with an estimated apparent degradation rate of 6.9 ×10−2 min−1, can be attributed to efficient charge separation by Ag NPs decorated on SiO2 NPs. This strategy may offer innovative considerations for the design of photocatalyst/carrier nanocomposites.