To enhance dye removal and energy recovery efficiencies in single-pair electrode photocatalytic fuel cell (PFC-AC), dual cathodes PFC (PFC-ACC) and dual photoanodes PFC (PFC-AAC) were established. Results revealed that PFC-AAC yielded the highest decolorization rate (1.44 h-1) due to the promotion of active species such as superoxide radical (•O2-) and hydroxyl radical (•OH) when the number of photoanode was doubled. The results from scavenging test and UV-Vis spectrophotometry disclosed that •OH was the primary active species in dye degradation of PFC. Additionally, PFC-AAC also exhibited the highest power output (17.99 μW) but the experimental power output was much lower than the theoretical power output (28.24 μW) due to the strong competition of electron donors of doubled photoanodes to electron acceptors at the single cathode and its high internal resistance. Besides, it was found that the increments of dye volume and initial dye concentration decreased the decolorization rate but increased the power output due to the higher amount of sacrificial agents presented in PFC. Based on the abovementioned findings and the respective dye intermediate products identified from gas chromatography-mass spectrometry (GC-MS), the possible degradation pathway of RR120 was scrutinized and proposed.
In advanced oxidation processes (AOPs), the aqueous hydroxyl radical (HO) acts as a strong oxidant to react with organic contaminants. The hydroxyl radical rate constant (kHO) is important for evaluating and modelling of the AOPs. In this study, quantitative structure-property relationship (QSPR) method is applied to model the hydroxyl radical rate constant for a diverse dataset of 457 water contaminants from 27 various chemical classes. The constricted binary particle swarm optimization and multiple-linear regression (BPSO-MLR) are used to obtain the best model with eight theoretical descriptors. An optimized feed forward neural network (FFNN) is developed to investigate the complex performance of the selected molecular parameters with kHO. Although the FFNN prediction results are more accurate than those obtained using BPSO-MLR, the application of the latter is much more convenient. Various internal and external validation techniques indicate that the obtained models could predict the logarithmic hydroxyl radical rate constants of a large number of water contaminants with less than 4% absolute relative error. Finally, the above-mentioned proposed models are compared to those reported earlier and the structural factors contributing to the AOP degradation efficiency are discussed.
The free radical scavenging activity and reducing power of 16 phenolic compounds including four hydroxycinnamic acid derivatives namely ferulic acid, caffeic acid, sinapic acid and p-coumaric acid, benzoic acid and its derivatives namely protocatechuic acid, gallic acid and vanillic acid, benzene derivatives namely vanillin, vanillyl alcohol, veratryl alcohol, veratraldehyde, pyrogallol, guaiacol and two synthetic antioxidants, butylated hydroxy anisole (BHA) and propyl gallate were evaluated using 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH(•)), 2,2'-Azinobis-3- ethylbenzothiazoline-6-sulfonic acid radical (ABTS(+•)), Hydroxyl radical ((•)OH) and Superoxide radical (O2 (•-)) scavenging assays and reduction potential assay. By virtue of their hydrogen donating ability, phenolic compounds with multiple hydroxyl groups such as protocatechuic acid, pyrogallol, caffeic acid, gallic acid and propyl gallate exhibited higher free radical scavenging activity especially against DPPH(•) and O2 (•-). The hydroxylated cinnamates such as ferulic acid and caffeic acid were in general better scavengers than their benzoic acid counter parts such as vanillic acid and protocatechuic acid. All the phenolic compounds tested exhibited more than 85 % scavenging due to the high reactivity of the hydroxyl radical. Phenolic compounds with multiple hydroxyl groups also exhibited high redox potential. Exploring the radical scavenging and reducing properties of antioxidants especially those which are found naturally in plant sources are of great interest due to their protective roles in biological systems.
In the title tri-substituted thio-urea derivative, C13H18N2O3S, the thione-S and carbonyl-O atoms lie, to a first approximation, to the same side of the mol-ecule [the S-C-N-C torsion angle is -49.3 (2)°]. The CN2S plane is almost planar (r.m.s. deviation = 0.018 Å) with the hy-droxy-ethyl groups lying to either side of this plane. One hy-droxy-ethyl group is orientated towards the thio-amide functionality enabling the formation of an intra-molecular N-H⋯O hydrogen bond leading to an S(7) loop. The dihedral angle [72.12 (9)°] between the planes through the CN2S atoms and the 4-tolyl ring indicates the mol-ecule is twisted. The experimental mol-ecular structure is close to the gas-phase, geometry-optimized structure calculated by DFT methods. In the mol-ecular packing, hydroxyl-O-H⋯O(hydrox-yl) and hydroxyl-O-H⋯S(thione) hydrogen bonds lead to the formation of a supra-molecular layer in the ab plane; no directional inter-actions are found between layers. The influence of the specified supra-molecular inter-actions is apparent in the calculated Hirshfeld surfaces and these are shown to be attractive in non-covalent inter-action plots; the inter-action energies point to the important stabilization provided by directional O-H⋯O hydrogen bonds.
Due to growing environmental concerns for better waste management, this study proposes developing a composite aerogel using cellulose nanofibers (CNF) and spent coffee grounds (SCG) through an eco-friendly method for efficient methylene blue (MB) adsorption. Adding SCG to the CNF aerogel altered the physical properties: it increases the volume (4.14 cm3 to 5.25 cm3) and density (0.018 to 0.022 g/cm3) but decrease the water adsorption capacity (2064 % to 1635 %). FTIR spectrum showed distinct functional groups in both all aerogels, showing hydroxyl, glyosidic bonds, and aromatic compounds. Additionally, SCG improved thermal stability of the aerogels. In term of adsorption efficacy, CNF-SCG40% aerogel as exceptionally well. According to Langmuir isotherm models, the adsorption of MB happened in a monolayer, with CNF-SCG40% showing a maximum adsorption capacity of 113.64 mg/g, surpassing CNF aerogel (58.82 mg/g). The study identified that the pseudo-second-order model effectively depicted the adsorption process, indicating a chemical-like interaction. This investigation successfully produced a single-use composite aerogel composed of CNF and SCG using an eco-friendly approach, efficiently adsorbing MB. By utilizing cost-effective materials and eco-friendly methods, this approach offers a sustainable solution for waste management, contributes to an eco-friendly industrial environment, and reduces production expenses and management costs.
In this study, lignin has been extracted from oil palm empty fruit bunch (EFB) fibers via an organosolv process. The organosolv lignin obtained was defined by the presence of hydroxyl-containing molecules, such as guaiacyl and syringyl, and by the presence of phenolic molecules in lignin. Subsequently, the extracted organosolv lignin and graphene nanoplatelets (GNP) were utilized as filler and reinforcement in photo-curable polyurethane (PU), which is used in stereolithography 3D printing. The compatibility as well as the characteristic and structural changes of the composite were identified through the mechanical properties of the 3D-printed composites. Furthermore, the tensile strength of the composited lignin and graphene shows significant improvement as high as 27%. The hardness of the photo-curable PU composites measured by nanoindentation exhibited an enormous improvement for 0.6% of lignin-graphene at 92.49 MPa with 238% increment when compared with unmodified PU.
In the title compound, C10H11NO2, two independent but virtually superimposable mol-ecules, A and B, comprise the asymmetric unit. The heterocyclic ring in each mol-ecule has a screw-boat conformation, and the methyl-hydroxyl group occupies a position to one side of this ring with N-C-C-O torsion angles of -55.30 (15) (mol-ecule A) and -55.94 (16)° (mol-ecule B). In the crystal, O-H⋯O and N-H⋯O hydrogen bonding leads to 11-membered {⋯HNCO⋯HO⋯HNC2O} heterosynthons, involving three different mol-ecules, which are edge-shared to generate a supra-molecular chain along the a axis. Inter-actions of the type C-H⋯O provide additional stability to the chains, and link these into a three-dimensional architecture.
In this work, quantum chemical analysis was used to predict the degradation potential of a recalcitrant dye, Acid blue 113, by hydrogen peroxide, ozone, hydroxyl radical and sulfate radical. Geometry optimization and frequency calculations were performed at 'Hartree Fock', 'Becke, 3-parameter, Lee-Yang-Parr' and 'Modified Perdew-Wang exchange combined with PW91 correlation' levels of study using 6-31G* and 6-31G** basis sets. The Fourier Transform-Raman spectra of Acid blue 113 were recorded and a complete analysis on vibrational assignment and fundamental modes of model compound was performed. Natural bond orbital analysis revealed that Acid blue 113 has a highly stable structure due to strong intermolecular and intra-molecular interactions. Mulliken charge distribution and molecular electrostatic potential map of the dye also showed a strong influence of functional groups on the neighboring atoms. Subsequently, the reactivity of the dye towards the oxidants was compared based on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy values. The results showed that Acid blue 113 with a HOMO value -5.227 eV exhibits a nucleophilic characteristic, with a high propensity to be degraded by ozone and hydroxyl radical due to their lower HOMO-LUMO energy gaps of 4.99 and 4.22 eV respectively. On the other hand, sulfate radical and hydrogen peroxide exhibit higher HOMO-LUMO energy gaps of 7.92 eV and 8.10 eV respectively, indicating their lower reactivity towards Acid blue 113. We conclude that oxidation processes based on hydroxyl radical and ozone would offer a more viable option for the degradation of Acid blue 113. This study shows that quantum chemical analysis can assist in selecting appropriate advanced oxidation processes for the treatment of textile effluent.
The chlorine radical is a potent atmospheric oxidant, capable of perturbing tropospheric oxidative cycles normally controlled by the hydroxyl radical. Significantly faster reaction rates allow chlorine radicals to expedite oxidation of hydrocarbons, including methane, and in polluted environments, to enhance ozone production. Here we present evidence, from the CARIBIC airborne dataset, for extensive chlorine radical chemistry associated with Asian pollution outflow, from airborne observations made over the Malaysian Peninsula in winter. This region is known for persistent convection that regularly delivers surface air to higher altitudes and serves as a major transport pathway into the stratosphere. Oxidant ratios inferred from hydrocarbon relationships show that chlorine radicals were regionally more important than hydroxyl radicals for alkane oxidation and were also important for methane and alkene oxidation (>10%). Our observations reveal pollution-related chlorine chemistry that is both widespread and recurrent, and has implications for tropospheric oxidizing capacity, stratospheric composition and ozone chemistry.
In this paper, a facile synthesis method for CaFe2O4 is introduced that produces a catalyst capable of significant photocatalytic degradation of POME under visible light irradiation. The co-precipitation method was used to produce two catalysts at calcination temperatures of 550 °C and 700 °C dubbed CP550 and CP700. CP550 demonstrated the maximum COD removal of 69.0% at 0.75 g/L catalyst loading after 8 h of visible light irradiation which dropped to 61.0% after three consecutive cycles. SEM images indicated that the higher calcination temperature of CP700 led to annealing which reduced the pore volume (0.025 cm3/g) and pore diameter (10.3 nm) while simultaneously creating a smoother and more spherical surface with lower SBET (9.73 m2/g). In comparison, CP550 had a rough hair-like surface with higher SBET (27.28 m2/g) and pore volume (0.077 cm3/g) as evidenced by BET analysis. XRD data indicated the presence of CaFe5O7 in the CP550 composition which was not present in CP700. The presence of Wustite-like FeO structures in CaFe5O7 are likely the cause for lower photoluminescence intensity profile and hence better charge separation of CP550 as these structures in CaFe2O4 have been known to increase resistivity and electron localization. The COD removal of CP550 dropped from 69.0% to just 7.0% upon adding a small quantity of isopropanol into the reaction mixture indicating hydroxyl radicals as the primary reactive oxidative species.
Natural rubber is one of the most important renewable biopolymers used in many applications due to its special properties that cannot be easily mimicked by synthetic polymers. To sustain the existence of natural rubber in industries, modifications have been made to its chemical structure from time to time in order to obtain new properties and to enable it to be employed in new applications. The chemical structure of natural rubber can be modified by exposure to ultraviolet light to reduce its molecular weight. Under controlled conditions, the natural rubber chains will be broken by photodegradation to yield low-molecular-weight natural rubber. The aim of this work was to obtain what is known as liquid natural rubber via photodegradation, with titanium dioxide nanocrystals as the catalyst. Titanium dioxide, which was firstly synthesized using the sol⁻gel method, was confirmed to be in the form of an anatase, with a size of about 10 nm. In this work, the photodegradation was carried out in latex state and yielded low-molecular-weight natural rubber latex of less than 10,000 g/mol. The presence of hydroxyl and carbonyl groups on the liquid natural rubber (LNR) chains was observed, resulting from the breaking of the chains. Scanning electron microscopy of the NR latex particles showed that titanium dioxide nanocrystals were embedded on the latex surface, but then detached during the degradation reaction.
The objective of this study is to establish conditions that allow optimal yield and antioxidant
activity for Golden Apple Snail (GAS) (Pomacea canaliculata) protein hydrolysate by employing
response surface methodology (RSM). A three level, face-centered, central composite design
(CCD) was adapted to assess the effects of temperature (45–65˚C); pH (8–10); the ratio of
enzyme to substrate (2–4%); and hydrolysis time (60–180 min). The antioxidative activity
of the hydrolysate obtained under optimized conditions was then evaluated via the following
metrics: hydroxyl radical scavenging, reducing power, and chelating effects on ferrous ion.
Established optimal conditions for the enzymatic protein hydrolysis of GAS were a temperature
of 45˚C, a pH of 10, an enzyme concentration of 2%, and hydrolysis time of 159 minutes. The
optimized GAS protein hydrolysate produced an experimental yield of 9.72% and antioxidant
activity of 73.54%—slightly less than the predicted yield of 11.36% and antioxidant activity of
78.88%. The optimized GAS protein hydrolysate formed demonstrated both higher chelating
effects and hydroxyl scavenging activity but had lower reducing power. These results suggest
that GAS protein hydrolysate holds potential as a natural antioxidant for use in food processing.
The main objective of this review is to derive the salient features of previously developed ultrasound-assisted methods for hydroxylating graphene and Buckminsterfullerene (C60). The pros and cons associated to ultrasound-assisted synthesis of hydroxy-carbon nanomaterials in designing the strategical methods for the industrial bulk production are also discussed. A guideline on the statistical methods has also been considered to further provide the scopes towards the application of the previously reported methods. Irrespective of many useful methods that have been developed in order to functionalize C60 and graphene by diverse oxygenated functional groups e.g. epoxide, hydroxyl, carboxyl as well as metal/metal oxide via a combination of organic chemistry and sonochemistry, there is no report dealing exclusively on the application of ultrasonic cavitation particularly to synthesising polyhydroxylated carbon nanomaterials. On this context, this review emphasizes in investigating the critical aspects of sono-nanochemistry and the statistical approaches to optimize the variables in the sonochemical process towards a large-scale synthesis of polyhydroxylated graphene and C60.
Perovskite-like oxides SrCo1-xTixO3-δ (SCTx, x = 0.1, 0.2, 0.4, 0.6) were used as heterogeneous catalysts to activate peroxymonosulfate (PMS) for phenol degradation under a wide pH range, exhibiting more rapid phenol oxidation than Co3O4 and TiO2. The SCT0.4/PMS system produced a high activity at increased initial pH, achieving optimized performance at pH ≥ 7 in terms of total organic carbon removal, the minimum Co leaching and good catalytic stability. Kinetic studies showed that the phenol oxidation kinetics on SCT0.4/PMS system followed the pseudo-zero order kinetics and the rate on SCT0.4/PMS system decreased with increasing initial phenol concentration, decreased PMS amount, catalyst loading and solution temperature. Quenching tests using ethanol and tert-butyl alcohol demonstrated sulfate and hydroxyl radicals for phenol oxidation. This investigation suggested promising heterogeneous catalysts for organic oxidation with PMS, showing a breakthrough in the barriers of metal leaching, acidic pH, and low efficiency of heterogeneous catalysis.
In Malaysia, most colored wastewater from dyeing factories is discharged to the environment causing serious problems. In this paper the influence of several reacting conditions, i.e. H2O2, pH, Ultraviolet (UV) intensity and dye concentration, on the performance of the immobilized system is discussed. The pH of the solution was varied from 3 to 11 while H2O2 concentration tested was from 10(-4) M to 5 x 10(-2) M. UV was tested at 365 nm and 254 nm, while dye concentration ranged from 2.5 x 10(-4) M to 10(-3) M. The influence of the reacting conditions was assessed based on absorbance. Using an OG concentration of 10(-3) M, the degradation increases from 17.8% to 49.7%. Optimum concentration of H2O2 was found to be 5 x 10(-3) M for degradation. Increasing the intensity of the UV light via shorter light wavelength also improves the performance of the system. Increasing the concentration of the dye reduces the overall performance of the system. Using the dye concentration of 2.5 x 10(-4) M (H2O2 = 10(-2) M, lambda = 254 nm, pH = 11), gives a degradation of 93.2%. At dye concentration of 10(-3) M, the performance was reduced to 53.1%.
Mushroom cultivation has become an important component of agriculture, providing food and contributing to the global economy. It uses vertical space and addresses issues of food quality, health improvement, and environmental sustainability. Auricularia mushrooms are popular ingredients in traditional Chinese cuisine. The objective of this study was to determine yield and evaluate radical scavenging capacity of A. polytricha cultivated on rubberwood sawdust on a large scale; we measured total phenolic content; DPPH, hydroxyl, superoxide anion, and peroxyl radical scavenging; and reducing power. Cultivation on rubberwood sawdust produces an average of 4 harvests per bag and a biological efficiency of 80-82%. The antioxidant capacity investigations revealed that the ethyl acetate fraction was the most potent radical scavenger in all assays except that for superoxide anions, whereas the aqueous fraction exhibited mild to moderate antioxidant capacity in scavenging the various radicals. Artificial cultivation of A. polytricha on rubberwood sawdust yields many sporophores with potent antioxidant capacity.
The hybrid electrochemical system of photocatalytic fuel cell - peroxi-coagulation (PFC-PC) is a combined technology of advanced oxidation process (AOP) which involve the hydroxyl radical formation for simultaneous degradation of organic pollutant and electricity generation. The p-nitrosodimethylaniline (RNO) spin trapping technique was applied by analyzing the RNO bleaching performance to detect the OH at the PFC and PC reactors. The presence of UV light showed higher RNO bleaching rate at the PFC reactor (11.7%) with maximum power density (Pmax = 3.14 mW cm-2). Results revealed that the optimum of maximum power density was observed at iron plate size of 30 cm2. UV light became a limiting factor in the PFC system as a power source in the PFC-PC system. Meanwhile, iron plate plays an important role to supply the soluble Fe2+ ions by oxidation process and become a suitable catalyst for in-situ production of H2O2 and OH through the PC process to degrade the organic molecules.
The aim of this study is to report the yield of extraction, as well as the physicochemical and antioxidant properties of extracted chitosan from mud crabs (S.olivacea) as compared to commercial chitosan. The yield obtained for extracted chitosan was 44.57 ± 3.44 % with a moisture and ash content of 9.48 ± 0.59 % and 5.97 ± 0.90 %, respectively. Commercial chitosan demonstrated a higher degree of deacetylation (58.42 ± 2.67 %), water (250 ± 9.90 %) and fat (329 ± 7.07 %) binding capacity, solubility (73.85 %), viscosity (463.25 ± 13.10 %) and also the whiteness value (77.8 ± 0.47) compared to the extracted chitosan, which were only 53.42 ± 0.88 %, 180 ± 0.00 %, 260 ± 0.00 %, 53.38 %, 383.9 ± 28.43 % and 62.1 ± 7.52 %, respectively. The structure of extracted and commercial chitosan was also investigated using Fourier Transform Infrared Spectroscopy (FTIR). In conclusion, the extracted chitosan possessed potential properties similar to the commercial chitosan with high reducing power but low in the scavenging activity on the DPPH and hydroxyl radicals compared to the commercial chitosan.
Psidium guajava L. (guava) is predominantly grown throughout the world and known for its medicinal properties in treating various diseases and disorders. The present work focuses on aqueous extraction of bioactive compounds from the guava leaf and its utilization in the formulation of jelly to improve the public health. The guava leaf extract has been used in the preparation of jelly with pectin (1.5 g), sugar (28 g) and lemon juice (2 mL). The prepared guava leaf extract jelly (GJ) and the control jelly (CJ, without extract) were subjected to proximate, nutritional and textural analyses besides determination of antioxidant and antimicrobial activities. GJ was found to contain carbohydrate (45.78 g/100 g), protein (3.0 g/100 g), vitamin C (6.15 mg/100 g), vitamin B3 (2.90 mg/100 g) and energy (120.6 kcal). Further, the texture analysis of CJ and GJ indicated that both the jellies showed similar properties emphasizing that the addition of guava leaf extract does not bring any change in the texture properties of jelly. GJ exhibited antimicrobial activity against various bacteria ranging from 11.4 to 13.6 mm. Similarly, GJ showed antioxidant activity of 42.38% against DPPH radical and 33.45% against hydroxyl radical. Mass spectroscopic analysis of aqueous extract confirmed the presence of esculin, quercetin, gallocatechin, 3-sinapoylquinic acid, gallic acid, citric acid and ellagic acid which are responsible for antioxidant and antimicrobial properties.
Saponin was extracted from Acanthophyllum glandulosum root under subcritical water conditions, and effects of root powder and pH of the solution were evaluated on the concentration of the saponin as manifested in its foamability and antioxidant activity using RSM. FT-IR analysis indicated that A. glandulosum root extract had 2 main functional groups (hydroxyl and amide I groups). Saponin with the highest foam height (4.66 cm), concentration (0.080 ppm) and antioxidant activity (90.6 %) was extracted using 10 g of the root powder and pH value of 4. Non-significant differences were observed between the predicted and experimental values of the extraction response variables. The study demonstrated good appropriateness of resulted models by Response Surface Methodology. Furthermore, higher values of R2 was attained for the foamability (>0.81) and antioxidant activity (>0.97), as well as large p-values (p > 0.05) indication of their lack-of-fit response verified the acceptable fitness of the provided models. The extracted saponin also showed bactericidal effect, which shows potential as a natural antibacterial compound.