Mediated Oxidation Process Research Articles

High-efficiency removal of As(iii) from groundwater using siderite as the iron source in the electrocoagulation process.

Electrocoagulation technology, due to its simplicity and ease of operation, is often considered for treating arsenic-contaminated groundwater. However, challenges such as anode wear have hindered its development and application. This study aims to develop a siderite-filled anode electrocoagulation system for efficient removal of As(iii) and investigate its effectiveness. The impact of operational parameters on the removal rate of As(iii) was analyzed through single-factor tests, and the stability and superiority of the device were evaluated. The response surface methodology was employed to analyze the interactions between various factors and determine the optimal operational parameters by integrating data from these tests. Under conditions where the removal rate of As reached 99.3 ± 0.37%, with an initial concentration of As(iii) at 400 μg L-1, current intensity at 30 mA, initial solution pH value at 7, and Na2SO4 concentration at 10 mM. The flocculant used was subjected to characterization analysis to examine its structure, morphology, and elemental composition under these optimal operational parameters. The oxidation pathway for As(iii) within this system relies on integrated results from direct electrolysis as well as ˙O2 -, ˙OH, and Fe(iv) mediated oxidation processes. The elimination of arsenic encompasses two fundamental mechanisms: firstly, the direct adsorption of As(iii) by highly adsorbent flocculants like γ-FeOOH and magnetite (Fe3O4); secondly, the oxidation of As(iii) into As(v), followed by its reaction with siderite or other compounds to generate a dual coordination complex or iron arsenate, thus expediting its eradication. The anodic electrocoagulation system employing siderite as a filler exhibits remarkable efficiency and cost-effectiveness, while ensuring exceptional stability, thereby providing robust theoretical underpinnings for the application of electrocoagulation technology in arsenic removal.

Ammonium persulfate oxidized nanofibrillated cellulose as a sustainable wet-end paper reinforcement additive

Nanocellulose fibers (NFCs) with specific characteristics were synthesized using the economically attractive ammonium persulfate (APS) mediated oxidation process to evaluate their potential as wet end additives in paper. The surface charge and morphology of as-synthesized NFC were tailored and characterized, and the barrier and strength properties of NFC-reinforced papers were thoroughly examined as a function of NFC contents and characteristics. The addition of two different cationic polyelectrolytes promoted electrostatic bridging between pulp fibers and maintained NFC retention above 93% regardless of the NFC nature. Results demonstrate that the presence of NFC with lower surface charge yields papers with denser fibrous network, reduced air permeability, and higher specific tensile strength. Higher surface charge NFC, on the other hand, increased floc formation and decreased NFC retention likely due to reduced dispersion and NFC agglomeration with the dual component retention system. Significantly, APS-oxidized NFC may be generally applicable as a competitive alternative to expensive and/or environmentally taxing chemicals typically employed in the manufacturing of a variety of papers and boards.

Treatment of Organics in Wastewater Using Electrogenerated Gaseous Oxidants.

This work focuses on the comparison of the performance of direct electrochemical oxidation with indirect electrolysis mediated by gaseous oxidants in the treatment of diluted wastewater. To do this, energy consumptions of the electrolysis using mixed metal oxide (MMO) electrodes are compared with those required for the production and use of chlorine dioxide in the degradation of methomyl contained in aqueous solutions. Results demonstrate the feasibility of the mediated oxidation process and that this process is competitive with direct oxidation. The oxidants are produced under optimized conditions using the same anodic material applied for the direct degradation of organics, thus avoiding efficiency losses associated with mass transfer limitations in the degradation of dilute organic solutions. Thus, using the ClO2 gaseous oxidant, a concentration of 0.1 mM of methomyl from a solution containing 500 mL is completely removed with an energy consumption as low as 50 Wh. The application of the same energy to a direct electrolytic process for treating the same wastewater can only reach less than half of this removal. These findings may have a very important application in the use of electrochemical technology to achieve the remediation of persistent pollutants in wastewater, where their low concentrations typically make direct processes very inefficient.

Cobalt(II) mediated electro-oxidation of toluene and its derivatives

The oxidation of toluene and its derivatives is crucial for the chemical industry. Traditional liquid-phase oxidation technologies require high-temperature and high-pressure conditions, which causes high safety risks and urgently requires alternatives. This article reports an electrochemical oxidation method using cobalt acetate as a mediator, which successfully realizes the mild oxidation of toluene. The method turns toluene into highly active radicals by the electrochemically generated Co(III) from cobalt acetate, which significantly reduces the anodic potential in contrast to the direct electro-oxidation and the other reported mediated oxidation processes. The target products, benzaldehyde and benzoic acid, exhibit high yields at 85 °C as the ratio of AcO- to Co(II) is close to 2 in the homogeneous anhydrous electrolyte. A benzyl radical-centered mechanism for the Co(II) mediated electro-oxidation of toluene is proposed based on the cyclic voltammetry tests and a radical inhibiting experiment. The method has also been successfully applied to the derivatives of toluene.

Study on the degradability of plastics with prodegradant additives during anaerobic and aerobic biological waste treatment processes

The degradability of conventional plastic packaging specimens made from PP and PET, that were produced with novel prodegradant additives, was investigated during biological waste treatment processes. The additives were merchandised to foster the degradation of commodity plastics by enzymatic or by abiotic processes. Four different plastic packaging specimens and two different additives were evaluated for their biodegradability during anaerobic and aerobic waste treatment conditions. Aerobic treatment was investigated in laboratory rotting tests, simulating conditions during composting in a plant according to the Austrian state-of-the-art, while anaerobic treatment was investigated in laboratory digestion reactors. The study shows that only the PET specimens showed a loss of mass of ca. 6.5%, during 50 days of digestion at 52 °C. None of the specimens degraded during the aerobic rotting process. None of the materials fragmented into microplastic particles of sizes > 1 mm under the investigated conditions. However, FTIR analysis revealed the oxidation in the case of PP specimens, which indicated a mediated oxidation process during composting, independent of the merchandised mechanism of predegradation. Under anaerobic conditions, the plastic specimens containing reactors produced more biogas within the first 20 days of digestion, that did not originate from an observable degradation of the plastics.

Differences in the Oxidizing Species on the Surface of Metal-Doped Ferrihydrite and Hematite in the Alkaline S(IV)-O2 Solution

Although inorganic Fe(IV)═O oxo and Fe(III)-OOH peroxo have attracted more attention in aqueous environments, direct evidence for the characterization and identification of those oxidizing species is still lacking. In this study, the doped Cu/Co increases the reactivity of ferrihydrite/hematite in oxidizing As(III) by S(IV)-O2 under alkaline and dark conditions. Quenching experiments exclude the contributions of ·OH, O2•–, SO3•–, SO4•–, SO5•–, HSO5–, and H2O2 and confirm that peroxo and oxo are primary oxidizing species in As(III) oxidation. Electrochemical analyses indicate that Fe(IV)═O oxo and Fe(III)-OOH peroxo are primarily located on the surface of ferrihydrite and hematite. Selective oxidation of methyl phenyl sulfoxide and methyl phenyl sulfide to the corresponding oxidation products further reveals the presence of ≡Fe(IV)═O oxo on both ferrihydrite and hematite, and the doped Cu/Co significantly decreases the produced ≡Fe(IV)═O oxo on ferrihydrite, while increases the produced ≡Fe(IV)═O oxo on hematite. Meanwhile, selective oxidation of benzyl alcohol to benzaldehyde indicates the presence of ≡Fe(III)-OOH peroxo on both ferrihydrite and hematite, and the doped Cu/Co apparently increases the produced ≡Fe(III)-OOH peroxo on ferrihydrite and hematite. Raman analysis further reveals the presence of ≡Fe(IV)═O oxo and ≡Fe(III)-OOH peroxo on pure and metal-doped ferrihydrite/hematite, which also confirms that the doped Cu/Co decreases the produced ≡Fe(IV)═O oxo on ferrihydrite and increases ≡Fe(IV)═O oxo on hematite, while apparently increasing ≡Fe(III)-OOH peroxo on both ferrihydrite and hematite. This study enriches our understanding on the oxidizing species in the S(IV)-mediated oxidation processes under alkaline conditions, providing new insight on the oxidation reactivity of surface peroxo and oxo species mediated by the doped metal ions.

Selective oxidation of ammonia to dinitrogen gas by facile Co2+/PMS/chloridion process through reactive chlorine radicals

The selective oxidation of ammonia to dinitrogen gas in some special wastewater is of paramount significance, but still a challenge. In this study, chlorine radical (Cl•)-mediated oxidation process was developed to realize the selective oxidation of NH4+-N to N2, in which Cl• was generated in Co2+/peroxymonosulfate (PMS)/chloridion (Cl−) system. The effect of various operational parameters on the efficiency and selectivity of ammonia oxidation to N2 was investigated, such as PMS concentration, Co2+ concentration, Cl− concentration and pH value. The experiment results showed that Cl•-mediated NH4+-N oxidation reaction exhibited high NH4+-N removal efficiency and considerable selectivity to N2 in the range of pH from 2.0 to 6.5. The removal efficiency of NH4+-N was 90.39%, and the selectivity of NH4+-N to N2 achieved up to 97.16%. The possible mechanism for high efficient and selective oxidation of NH4+-N to N2 was tentatively proposed. The process developed in this study could provide a novel technology for the treatment and selective oxidation of ammonium in some special types of ammonium-containing wastewater.

Radiation mediated oxidation processes for the conversion of 4-aminothiophenol in to 4, 4′-dimercaptoazobenzene

Gold (Au) nanoparticles of average size ∼ 4 nm were in-situ synthesized and simultaneously embedded on SiO2 nanospheres in a single step process by irradiating a solution (HAuCl4, PVP and SiO2 nanospheres) with 6 MeV electrons at a fluence of 1.0 × 1015 e−/cm2. Substrates were prepared by coating silicon wafers with the solution of SiO2 nanospheres embedded with Au nanoparticles and used for recording Surface-enhanced Raman scattering (SERS) spectra of 4-aminothiophenol (4-ATP) and 4-ATP along with NaOH with a Raman spectrometer. The appearance of characteristic SERS peaks of both 4-ATP and 4, 4′-DMAB in Raman spectra confirmed conversion of a fraction of 4-ATP into 4, 4′-DMAB in the presence of Au nanoparticles, and the intensity of SERS peaks increased in the presence of NaOH. In the recorded SERS spectra, the prominent peaks at around 1140 cm−1, 1390 cm−1 and 1438 cm−1 were observed and assigned respectively to β(C–H), ν(NN) and ν(NN) chemical bonds, which are called b2 modes. The results of the present work revealed that in the presence of Au nanoparticles, the OH− radicals produced from NaOH play an important role in the conversion of 4-ATP into 4, 4′-DMAB, and enhancing the intensities of b2 peaks. The Au nanoparticles of size ≤5 nm have inherent nanoscale defects and therefore surface with nanoscale roughness. All these together greatly enhanced electric field which brought out the strong Raman intensity and catalytic oxidation reaction leading to conversion of 4-ATP into 4,4′-DMAB on the Au–SiO2 substrates.

Real-Time Detection of Hydroxyl Radical Generated at Operating Electrodes via Redox-Active Adduct Formation Using Scanning Electrochemical Microscopy.

The hydroxyl radical (•OH) is one of the most attractive reactive oxygen species due to its high oxidation power and its clean (photo)(electro)generation from water, leaving no residues and creating new prospects for efficient wastewater treatment and electrosynthesis. Unfortunately, in situ detection of •OH is challenging due to its short lifetime (few ns). Using lifetime-extending spin traps, such as 5,5-dimethyl-1-pyrroline N-oxide (DMPO) to generate the [DMPO-OH]• adduct in combination with electron spin resonance (ESR), allows unambiguous determination of its presence in solution. However, this method is cumbersome and lacks the necessary sensitivity and versatility to explore and quantify •OH generation dynamics at electrode surfaces in real time. Here, we identify that [DMPO-OH]• is redox-active with E0 = 0.85 V vs Ag|AgCl and can be conveniently detected on Au and C ultramicroelectrodes. Using scanning electrochemical microscopy (SECM), a four-electrode technique capable of collecting the freshly generated [DMPO-OH]• from near the electrode surface, we detected its generation in real time from operating electrodes. We also generated images of [DMPO-OH]• production and estimated and compared its generation efficiency at various electrodes (boron-doped diamond, tin oxide, titanium foil, glassy carbon, platinum, and lead oxide). Density functional calculations, ESR measurements, and bulk calibration using the Fenton reaction helped us unambiguously identify [DMPO-OH]• as the source of redox activity. We hope these findings will encourage the rapid, inexpensive, and quantitative detection of •OH for conducting informed explorations of its role in mediated oxidation processes at electrode surfaces for energy, environmental, and synthetic applications.

Dissolved black carbon induced elimination of bisphenol a by peroxymonosulfate activation through HClO mediated oxidation process

Dissolved black carbon (DBC) is released into environmental media following the wide adoption of biochar-catalyzed peroxymonosulfate (PMS) advanced oxidation processes (AOPs) in wastewater treatment. However, the possible reactivity between DBC and PMS in the process has not yet been reported. In this study, the role of DBC in the biochar-initiated PMS activation process was comprehensively explored. For the first time, we discovered that DBC could significantly improve the oxidation of bisphenol A (BPA) by PMS activation with a pseudo-first-order kinetic rate constant (kapp) of 0.040 min−1. Different biomass feedstocks led to distinguishable kapp values, revealing the reactive species were largely depended on the intrinsic properties of biomass. The activation mechanism was comprehensively elucidated through in-situ and ex-situ techniques. Radical species (i.e., •OH and SO4•−) as well as singlet oxygen (1O2) were not the dominant contributors, while the Cl- induced formation of hypochlorous acid (HClO) was confirmed to be the primary oxidative species responsible for BPA oxidation. On the other hand, dissolved organic components in DBC preferentially consumed HClO and thus inhibited the oxidation of BPA. Typical chlorinated derivatives (i.e., 3-chlorobisphenol A, 3,3′-dichlorobisphenol A, 3,5-dichlorobisphenol A and 3,3′,5- trichlorobisphenol A) were identified after the oxidation process. These findings benefited further understanding of the role of biochar derived DBC and revealed the potential environmental risk of biochar-activated PMS oxidation processes.

Biomass-derived porous carbon with high drug adsorption capacity undergoes enzymatic and chemical degradation

Degradability is a key safety issue when choosing materials for biomedical applications and environmental protection. This factor greatly limits the application of porous carbon in these areas due to the inert and stable nature of carbon network. In this work, this conflict could be well-resolved by rational designing a mesoporous carbon (MC) with biomass as a carbon source. The retained oxygen-containing species simultaneously increase drug adsorption capacity and the degradability of MC. The maximum adsorption quantity for doxorubicin over MC can reach 395.3 mg/g, about 3-fold over carbon nanotubes. The detailed analysis reveals that the degradation of MC occurs via a radical mediated oxidation process. The high electron density feature of MC facilitates the electrophilic addition reaction in the presence of HO. During this process, the carbon network is gradually degraded into fragments, carbon nanodots and ultimately to CO2. This work opens up a new way to fabricate degradable porous materials and provides a promising material for the practical application in biomedical and environmental field.

Electrochemical Ni-EDTA degradation and Ni removal from electroless plating wastewaters using an innovative Ni-doped PbO2 anode: Optimization and mechanism

In this work, a novel Ni-doped PbO2 anode (Ni-PbO2) was prepared via a co-electrodeposition method and used to remove Ni-ethylenediaminetetraacetic acid (Ni-EDTA) from solutions typical of electroless nickel plating wastewater. Compared with a pure PbO2 electrode, Ni doping increased the oxygen evolution potential as well as the reactive surface area and reactive site concentration and reduced the electron transfer resistance thereby resulting in superior Ni-EDTA degradation performance. The 1% Ni-doped PbO2 electrode exhibited the best electrochemical oxidation activity with a Ni-EDTA removal efficiency of 96.5 ± 1.2%, a Ni removal efficiency of 52.1 ± 1.4% and an energy consumption of 2.6 kWh m−3. Further investigations revealed that 1% Ni doping enhanced both direct oxidation and hydroxyl radical mediated oxidation processes involved in Ni-EDTA degradation. A mechanism for Ni-EDTA degradation is proposed based on the identified products. The free nickel ion concentration initially increased as a result of the degradation of Ni-EDTA complexes and subsequently decreased as a consequence of nickel electrodeposition on the cathode surface. Further characterization of the cathode deposits by X-ray diffraction and X-ray photoelectron spectra indicated that the deposition products were a mixture of Ni0, NiO and Ni(OH)2 with elemental Ni accounting for roughly 80% of the deposited nickel. Results of this study pave the way for the application of anodic oxidation processes for efficient degradation of Ni-containing complexes and recovery of Ni from nickel-containing wastewaters.

The optimization of enzymatic oxidation of levofloxacin, a fluoroquinolone antibiotic for wastetwater treatment.

The global presence of antibiotics in the environment has created concerns about the emergence of antibiotic resistance bacteria and potential hazard to humans and the ecosystem. This work aims to study the removal of levofloxacin, a new generation fluoroquinolone antibiotic from aqueous solutions by enzyme mediated oxidation process and optimization of the conditions thereof by response surface methodology (RSM) using Box-Behnken design (BBD). For this study, experiments were conducted to analyze the effect of independent variables namely, pH, temperature, mediator concentration and antibiotic concentration on the degradation percentage of levofloxacin antibiotic using laccase enzyme derived from Trametes versicolor. The residual levofloxacin concentration was determined using high performance liquid chromatography (HPLC). On applying the quadratic regression analysis, among the main parameters, it was found that the percentage degradation was significantly affected by all the four variables. The predicted values for percentage degradation of levofloxacin were close to the experimental values obtained and the R2 (0.95) indicated that the regression was able to give a good prediction of response for the percentage degradation of levofloxacin in the studied range. The optimal conditions for the maximum degradation (99.9%) as predicted by the BBD were: temperature of 37°C, pH of 4.5, mediator concentration of 0.1mM and levofloxacin concentration of 5μgmL-1. The findings of the study were further extended to study the effect of partially purified enzymes isolated from Pleurotus eryngii, Pleurotus florida and Pleurotus sajor caju on the degradation of levofloxacin at concentrations ranging from as low as 0.1 to as high as 50µgmL-1 in synthetic wastewater utilizing the optimized conditions generated by BBD. A maximum degradation of 88.8% was achieved with the partially purified enzyme isolated from Pleurotus eryngii at 1µgmL-1 levofloxacin concentration which was at par with the commercial laccase which showed 89% degradation in synthetic wastewater at the optimized conditions. The biodegradation studies were conducted using only 2 units of laccase. Thus, the expensive commercial laccase can be effectively replaced by crude laccase isolated from indigenous macrofungi such as P. eryngii, P. florida and P. sajor caju as a cost effective alternative to degrade levofloxacin present in contaminated wastewater using as low as 2 units of enzyme for a 72h treatment period.

Acid mine drainage and sewage impacted groundwater treatment by membrane distillation: Organic micropollutant and metal removal and membrane fouling

Groundwater is the dominant source of freshwater in many countries around the globe, and the deterioration in its quality by contaminants originating from anthropogenic sources raises serious concern. In this study, a scenario where groundwater is contaminated by acid mine drainage (AMD) from mining activities and/or sewage was envisaged, and the performance of a direct contact membrane distillation (DCMD) system was investigated comprehensively for different compositions of the AMD- and sewage-impacted groundwater. Regardless of the composition, MD membrane achieved 98–100% removal of metals and bulk organics, while the removal of the selected micropollutants ranged between 80 and 100%. Effective retention of contaminants by the MD led to their accumulation over time, which affected the hydraulic performance of the MD membrane by reducing the permeate flux by 29–76%. When persulfate (PS)-mediated oxidation process was integrated with the DCMD, degradation of bulk organics (50–71%) and micropollutants (50–100%) by PS reduced their accumulation. Characterisation of the fouling layer revealed the occurrence of membrane scaling that was mainly due to the deposition of iron oxide or oxyhydroxide precipitates. For an identical composition of the AMD- and sewage-impacted groundwater, flux decline was 10% less in PS-assisted DCMD as compared to that in the standalone DCMD. However, this did not prevent the formation of iron oxide scales on MD membrane during the operation of PS-assisted DCMD. This study demonstrates the long-term performance of a standalone and PS-assisted DCMD operated in continuous-flow mode to treat AMD- and sewage-impacted groundwater for the first time.

Investigation of a Widely Applicable Process for Extracting Carboxyl-rich Cellulose Nanocrystal (CNC)

Herein, carboxyl-rich cellulose nanocrystals (CNC) were obtained through a designed TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) mediated oxidation process without any subsequent mechanical treatment, which was proved to be widely suitable for commonly used cellulosic sources, including fibril-like fibers and lignocellulose biomasses. CNC prepared from the acid-free process showed better dispersion stability, less aggregation, higher aqueous UV transmittance and crystallinity compared with that from sulfuric acid hydrolysis process. Furthermore, the residuals in the insoluble precipitate were further conducted ultrasonic treatment and extra CNC was obtained from the oxidized cotton and ramie cellulose while cellulose nanofibril (CNF) was extracted from rice straw and pine powder, attributing to their different native structures. The total yields of nanocelluloses (NCs) were up to 63.2–68.3 %, improving the utilization ratio of the raw materials. This work provided a widely applicable acid- and mechanic-free route in fabricating CNC with inherent carboxyl groups and described an understanding of the relationship between the native structure of raw materials and their products, which is beneficial for improving the application of NCs.

Selective oxidation of H1-antihistamines by unactivated peroxymonosulfate (PMS): Influence of inorganic anions and organic compounds

The rapid and selective peroxymonosulfate (PMS) induced transformation of H1-antihistamines cetirizine (CET) and diphenhydramine (DPH) can be influenced by the presence of common organic and inorganic water constituents. Presence of HCO3– and/or CO32–, which often exhibit powerful inhibition on the advanced oxidation processes (AOPs), can enhance the PMS mediated transformation of CET/DPH. The observed promotion is demonstrated by the changed solution pH through detailed kinetic studies. The impact of halide ions is remarkable, with I– inhibiting the process through consumption of PMS, while Cl– increases slightly the transformation kinetics through the formation and subsequent reactions of HOCl. The CET/DPH degradation in the Br–/PMS system is influenced by the generation of reactive species such as HOBr which leads to different reaction pathways as compared to PMS alone. The results demonstrated the performance of PMS can be tailored through varying the experimental parameters. In addition, the presence of model organic constituents found in water, e.g., humic acid, phenol, pyridine or sorbate, has a minimal effect on the PMS mediated oxidation processes, highlighting the strong application potential of PMS in water treatment.

Dispersion Stability of Nanocellulose in Nonpolar Solvent: Chloroform

Nanocellulose (NC) has been successfully isolated from Oil Palm Empty Fruit Bunch (OPEFB) by using catalyst 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) through mediated oxidation process. For use as a reinforcing component in polymer bionanocomposites, NC has to be completely dried to avoid agglomeration in the non-polar solvent. In this research three types of approaches namely, oven drying (OD), freeze drying (FD) and solvent exchange (SE) were used to remove the water. Based on the dispersion stability results, the NC prepared from the OD technique gave longer stable suspension than that produced by FZ and SE. Besides, this method is also relatively simple and cost effective.

Experimental and theoretical insights into kinetics and mechanisms of hydroxyl and sulfate radicals-mediated degradation of sulfamethoxazole: Similarities and differences

Hydroxyl radical (•OH)- and sulfate radical (▪)-based advanced oxidation technologies (AOTs) have been proven an effective method to remove antibiotics in wastewater treatment plants (WWTPs). This study aims to gain insights into kinetics and mechanisms of neutral sulfamethoxazole (SMX) degradation, a representative antibiotic, by •OH and ▪ using an experimental and theoretical approach. First, the second-order rate constants (k) of SMX with •OH and ▪ were determined to be (7.27 ± 0.43) × 109 and (2.98 ± 0.32) × 109 M−1 s−1 in UV/H2O2 and UV/persulfate (UV/PS) systems, respectively. The following theoretical calculations at the M06–2X level of theory revealed that addition of radicals to the benzene ring is the most favorable first-step reaction for both •OH and ▪, but that ▪ exhibits higher energy barriers and selectivity than •OH due to steric hindrance. We further analyzed subsequent reactions and, interestingly, our findings closely corroborated HOMO/LUMO distributions of SMX to the oxidation pathways. Finally, the estimation of energy consumption for UV alone, •OH–, and ▪–mediated oxidation processes was compared. These comparative results, for the first time, provide insights into the similarities and differences of degradation of SMX by •OH/▪ at the molecular level and can help improve antibiotics removal using radical based AOTs in WWTPs.

Effect of Cellulose Nanofibrils and TEMPO-mediated Oxidized Cellulose Nanofibrils on the Physical and Mechanical Properties of Poly(vinylidene fluoride)/Cellulose Nanofibril Composites.

Cellulose nanofibrils (CNFs) are high aspect ratio, natural nanomaterials with high mechanical strength-to-weight ratio and promising reinforcing dopants in polymer nanocomposites. In this study, we used CNFs and oxidized CNFs (TOCNFs), prepared by a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation process, as reinforcing agents in poly(vinylidene fluoride) (PVDF). Using high-shear mixing and doctor blade casting, we prepared free-standing composite films loaded with up to 5 wt % cellulose nanofibrils. For our processing conditions, all CNF/PVDF and TOCNF/PVDF films remain in the same crystalline phase as neat PVDF. In the as-prepared composites, the addition of CNFs on average increases crystallinity, whereas TOCNFs reduces it. Further, addition of CNFs and TOCNFs influences properties such as surface wettability, as well as thermal and mechanical behaviors of the composites. When compared to neat PVDF, the thermal stability of the composites is reduced. With regards to bulk mechanical properties, addition of CNFs or TOCNFs, generally reduces the tensile properties of the composites. However, a small increase (~18%) in the tensile modulus was observed for the 1 wt % TOCNF/PVDF composite. Surface mechanical properties, obtained from nanoindentation, show that the composites have enhanced performance. For the 5 wt % CNF/PVDF composite, the reduced modulus and hardness increased by ~52% and ~22%, whereas for the 3 wt % TOCNF/PVDF sample, the increase was ~23% and ~25% respectively.

Mediated electrochemical oxidation (MEO) process: a study on nonylphenol ethoxylates (NPE) oxidation in batch mode using cerium (IV) oxidant

Nonylphenol ethoxylate (NPE-10) is one type of non-ionic surfactants from the class of alkylphenol ethoxylate (APE). This compound is already tightened their use in European Union countries. However, these surfactants are still used widely in Indonesia because the price is relatively cheap. Consequently, these compounds can accumulate in aquatic environments. NPE-10 can disrupt aquatic ecosystems. This study aimed to describe the electro-oxidation process of NPE-10 based on the parameters of a potential difference, concentration of NPE-10, concentration of Ce (III), and oxidation time. The result of oxidation NPE-10 was measured by the amount of current generated from voltammetry technique. Studies of cyclic voltammetry using carbon paste electrodes illustrates the potential value of the oxidation of Ce (III) / Ce (IV) of 1.25 V and the reduction potential value of Ce (IV) / Ce (III) of 1.192 V. NPE-10 are electroactive irreversible because it only provides the potential value of oxidation at 1.44 V. Percent of total degradation of 84.96% was obtained at electro-oxidation of 500 ppm NPE-10 by the addition of 0.015 M Ce (III) for 90 minutes at 0.2 M H2SO4and the use of potential of 6 V.