Aluminum substituted yttrium iron garnet nano particles with compositional variation of Y(3.0-x) A1(x)Fe5O12, where x = 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 were prepared using sol gel technique. The X-ray diffraction results showed that the best garnet phase appeared when the sintering temperature was 800 degrees C. Nano-crystalline particles with high purity and sizes ranging from 20 to 100 nm were obtained. It was found that the aluminum substitution had resulted in a sharp fall of the d-spacing when x = 2, which we speculated is due to the preference of the aluminum atoms to the smaller tetrahedron and octahedron sites instead of the much larger dodecahedron site. High resolution transmission electron microscope (HRTEM) and electron diffraction (ED) patterns showed single crystal nanoparticles were obtained from this method. The magnetic measurement gave moderate values of initial permeability; the highest value of 5.3 was shown by sample Y3Fe5O12 at more than 100 MHz which was attributed to the morphology of the microstructure which appeared to be homogeneous. This had resulted in an easy movement of domain walls. The substitution of aluminum for yttrium is speculated to cause a cubic to rhombodedral structural change and had weakened the super-exchange interactions thus a fall of real permeability was observed. This might have created a strain in the sub-lattices and had subsequently caused a shift of resonance frequencies to more than 1.8 GHz when x > 0.5.
Ferrocene or ferrocenium has been widely studied in the field of organometallic complexes because of its stable thermodynamic, kinetic and redox properties. Novel hexaferrocenium tri[hexa(isothiocyanato)iron(III)]trihydroxonium (HexaFc) complex was the product from the reaction of ferrocene, maleic acid and ammonium thiocyanate and was confirmed by elemental analysis CHNS, FTIR and single crystal X-ray crystallography. In this study, HexaFc was used for the first time as an electroactive indicator for porcine DNA biosensor. The UV-Vis DNA titrations with this compound showed hypochromism and redshift at 250 nm with increasing DNA concentrations. The binding constant (Kb) for HexaFc complex towards CT-DNA (calf-thymus DNA) was 3.1 × 104 M-1, indicated intercalator behaviour of the complex. To test the usefulness of this complex for DNA biosensor application, a porcine DNA biosensor was constructed. The recognition probes were covalently immobilised onto silica nanospheres (SiNSs) via glutaraldehyde linker on a screen-printed electrode (SPE). After intercalation with the HexaFc complex, the response of the biosensor to the complementary porcine DNA was measured using differential pulse voltammetry. The DNA biosensor demonstrated a linear response range to the complementary porcine DNA from 1 × 10-6 to 1 × 10-3 µM (R2 = 0.9642) with a limit detection of 4.83 × 10-8 µM and the response was stable up to 23 days of storage at 4 °C with 86% of its initial response. The results indicated that HexaFc complex is a feasible indicator for the DNA hybridisation without the use of a chemical label for the detection of porcine DNA.
The decolorization of Acid Red 1 (AR1) in aqueous solution was investigated by Fenton-like process. The effect of different reaction parameters such as different iron ions loading on rice husk ash (RHA), dosage of catalyst, initial pH, the initial hydrogen peroxide concentration ([H(2)O(2)](o)), the initial concentration of AR1 ([AR1](o)) and the reaction temperature on the decolorization of AR1 was studied. The optimal reacting conditions were found to be 0.070 wt.% of iron (III) oxide loading on RHA, dosage of catalyst=5.0 g L(-1), initial pH=2.0, [H(2)O(2)](o)=8 mM, [AR1](o)=50 mg L(-1) at temperature 30 degrees C. Under optimal condition, 96% decolorization efficiency of AR1 was achieved within 120 min of reaction.
We demonstrate a green chemistry approach to synthesize narrow-sized zerovalent iron (nZVI) nanoparticles using Artocarpus heterophyllus Lam. leaf extract as reducing and capping agent. The produced nZVI was characterized by various instrumental methods including ultraviolet-visible spectra, transmission electron microscopy, vibrating sample magnetometer (VSM), X-ray diffraction, and Fourier transform infrared spectroscopy. Based on the electron microscopy observations, the particle size was estimated to be ∼30 nm. In VSM, the saturation point of magnetization was observed to be 0.6 emu g-1 under a magnetic field of 0 ± 30 kOe. The synthesized nZVI was amorphous in nature as per the XRD results. The catalytic activity of the nZVI was employed for the catalytic reduction of 4-nitrophenol (4-NP) and decoloration of textile dyes such as methylene blue, methyl orange, and malachite green, respectively. The proposed nZVI synthesis method exhibited better catalytic performance toward reduction of 4-NP and degradation of dyes within 4 min for 0.1 mg of catalyst. Moreover, the synthesized catalyst nZVI can be recoverable and reutilized in many cycles without loss of its significant catalytic activity. The synthesized nZVI could be a promising material to treat industrial wastewater via profitable, sustainable, and ecofriendly approaches.
In the present study, a comparison of central composite design (CCD) and Taguchi method was established for Fenton oxidation. [Dye]ini, Dye:Fe(+2), H2O2:Fe(+2), and pH were identified control variables while COD and decolorization efficiency were selected responses. L 9 orthogonal array and face-centered CCD were used for the experimental design. Maximum 99% decolorization and 80% COD removal efficiency were obtained under optimum conditions. R squared values of 0.97 and 0.95 for CCD and Taguchi method, respectively, indicate that both models are statistically significant and are in well agreement with each other. Furthermore, Prob > F less than 0.0500 and ANOVA results indicate the good fitting of selected model with experimental results. Nevertheless, possibility of ranking of input variables in terms of percent contribution to the response value has made Taguchi method a suitable approach for scrutinizing the operating parameters. For present case, pH with percent contribution of 87.62% and 66.2% was ranked as the most contributing and significant factor. This finding of Taguchi method was also verified by 3D contour plots of CCD. Therefore, from this comparative study, it is concluded that Taguchi method with 9 experimental runs and simple interaction plots is a suitable alternative to CCD for several chemical engineering applications.
The mineralisation kinetics of petroleum refinery effluent (PRE) by Fenton oxidation were evaluated. Within the ambit of the experimental data generated, first-order kinetic model (FKM), generalised lumped kinetic model (GLKM), and generalized kinetic model (GKM) were tested. The obtained apparent kinetic rate constants for the initial oxidation step (k'2), their final oxidation step (k'1), and the direct conversion to endproducts step (k3') were 10.12, 3.78, and 0.24 min(-1) for GKM; 0.98, 0.98, and nil min(-1) for GLKM; and nil, nil, and >0.005 min(-1) for FKM. The findings showed that GKM is superior in estimating the mineralization kinetics.
The mineralisation of remazol black B (RBB) was studied at concentrations ranging from 20-1000 mgL(-1). The work was aimed at investigating the Fenton-like peroxidation of RBB at a concentration typically obtained in Batik cottage industries. Other response parameters were degradation and colour removal efficiencies. The parameters that were measured included total organic carbon (TOC), chemical oxygen demand (COD) as well as absorbance for mineralisation, degradation and colour. To optimise the process, the interaction effects of several controlling variables on the treatment process were examined using dispersion matrix-optimal design and response surface analysis. Four specific variables: initial dye concentration (Dye)o; the molar ratio of oxidant to dye organic strength (H2O2):(COD); the mass ratio of the oxidant to the catalyst (H2O2):(Fe3+) and reaction time (t(r)), were observed. Three reduced empirical models, one for each response, were developed for describing the treatment process. For 20, 510 and 1000 mgL(-1), the optimum %TOC reduction and oxidation times were 44% for 95 min, 52% for 52.5 min and 68% for 10 min corresponding to 67, 81 and 75% COD reduction, respectively. The optimum COD reduction and oxidation times were 89% for 95 min, 91% for 10 min and 84% for 95 min for concentrations of 20, 510 and 1000 mg L(-1), respectively. For all concentrations, total colour removal was achieved. A comparison of the results obtained in this study with literature values for traditional Fenton, photo-Fenton and photo-Fenton-like oxidation indicated that the TOC reduction obtained using the Fenton-like process was satisfactory.
Fish meal is currently the major protein source for commercial aquaculture feed. Due to its unstable supply and increasing price, fish meal is becoming more expensive and its availability is expected to face significant challenges in the near future. Therefore, feasible alternatives to fish meal are urgently required. Microalgae have been recognized as the most promising candidates to replace fish meal because the protein composition of microalgae is similar to fish meal and the supply of microalgae-based proteins is sustainable. In this study, an indigenous microalga (Chlorella vulgaris FSP-E) with high protein content was selected, and its feasibility as an aquaculture protein source was explored. An innovative photobioreactor (PBR) utilizing cold cathode fluorescent lamps as an internal light source was designed to cultivate the FSP-E strain for protein production. This PBR could achieve a maximum biomass and protein productivity of 699 and 365 mg/L/day, respectively, under an optimum urea and iron concentration of 12.4 mM and 90 μM, respectively. In addition, amino acid analysis of the microalgal protein showed that up to 70% of the proteins in this microalgal strain consist of indispensable amino acids. Thus, C. vulgaris FSP-E appears to be a viable alternative protein source for the aquaculture industry.
The application of the anammox process has great potential in treating nitrogen-rich wastewater. The presence of Fe (II) is expected to affect the growth and activity of anammox bacteria. Short-term (acute) and long-term effects (chronic) of Fe (II) on anammox activity were investigated. In the short-term study, results demonstrated that the optimum concentration of Fe (II) that could be added to anammox is 0.08 mM, at which specific anammox activity (SAA) improved by 60% compared to the control assay, 0.00 mM. The inhibition concentration, IC50, of Fe (II) was found to be 0.192 mM. Kinetics of anammox specific growth rate were estimated based on results of the batch test and evaluated with Han-Levenspiel's substrate inhibition kinetics model. The optimum concentration and IC50 of Fe (II) predicted by the Han-Levenspiel model was similar to the batch test, with values of 0.07 mM and 0.20 mM, respectively. The long-term effect of Fe (II) on the performance of a sequencing batch reactor (SBR) was evaluated. Results showed that an appropriate Fe (II) addition enhanced anammox activity, achieving 85% NH4+-N and 96% NO2--N removal efficiency when 0.08 mM of Fe (II) was added. Quantitative polymerase chain reaction (qPCR) was adopted to detect and identify the anammox bacteria.
The objective of this study was to investigate the performance of employing Fenton's reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and Fenton dosage, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities (<0.0001): chemical oxygen demand (COD), color, NH-N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 90 min, 30 g/m³ ozone, 0.01 mol/L₂H₂O,0.02 mol/L Fe²⁺, and pH 5. COD, color, and NH₃-N removal rates of 79%, 100%, and 20%, respectively, and 0.18 kg O₃/kg COD OC were obtained. The predictions correspond well with experimental results (COD, color, and NH-N removal rates of 78%, 98.5%, and 19%, respectively, and 0.29 kg O₃/kg COD OC). This method reduces the treatment time and improves the treatment efficiency relative to a previously published method that used Fenton's reagent prior to ozonation.
Silica supported iron catalyst was prepared from rice husk ash (RHA) via the sol-gel technique using an aqueous solution of iron(III) salt in 3.0 M HNO3. The sample was dried at 110 degrees C and labeled as RHA-Fe. A sample of RHA-Fe was calcined at 700 degrees C for 5 h and labeled as RHA-Fe700. X-ray diffraction spectrogram showed that both RHA-Fe and RHA-Fe700 were amorphous. The SEM/EDX results showed that the metal was present as agglomerates and the Fe ions were not homogeneously distributed in RHA-Fe but RHA-Fe700 was shown to be homogeneous. The specific surface areas for RHA-Fe and RHA-Fe700 were determined by BET nitrogen adsorption studies and found to be 87.4 and 55.8 m(2) g(-1), respectively. Both catalysts showed high activity in the reaction between toluene and benzyl chloride. The mono-substituted benzyltoluene was the major product and both catalysts yielded more than 92% of the product. The GC showed that both the ortho- and para-substituted monoisomers were present in about equal quantities. The minor products consisting of 16 di-substituted isomers were also observed in the GC-MS spectra of both catalytic products. The catalyst was found to be reusable without loss of activity and with no leaching of the metal.
Ozonation, combined with the Fenton process (O(3)/H(2)O(2)/Fe(2+)), was used to treat matured landfill leachate. The effectiveness of the Fenton molar ratio, Fenton concentration, pH variance, and reaction time were evaluated under optimum operational conditions. The optimum removal values of chemical oxygen demand (COD), color, and NH(3)-N were found to be 65%, 98%, and 12%, respectively, for 90 min of ozonation using a Fenton molar ratio of 1 at a Fenton concentration of 0.05 mol L(-1) (1700 mg/L) H(2)O(2) and 0.05 mol L(-1) (2800 mg/L) Fe(2+) at pH 7. The maximum removal of NH(3)-N was 19% at 150 min. The ozone consumption for COD removal was 0.63 kg O(3)/kg COD. To evaluate the effectiveness, the results obtained in the treatment of stabilized leachate were compared with those obtained from other treatment processes, such as ozone alone, Fenton reaction alone, as well as combined Fenton and ozone. The combined method (i.e., O(3)/H(2)O(2)/Fe(2+)) achieved higher removal efficiencies for COD, color, and NH(3)-N compared with other studied applications.
The effect of pH and redox potential on the redox equilibria of iron oxides in aqueous-based magnetite dispersions was investigated. The ionic activities of each dissolved iron species in equilibrium with magnetite nanoparticles were determined and contoured within the Eh-pH framework of a composite stability diagram. Both standard redox potentials and equilibrium constants for all major iron oxide redox equilibria in magnetite dispersions were found to differ from values reported for noncolloidal systems. The "triple point" position of redox equilibrium among Fe(II) ions, magnetite, and hematite shifted to a higher standard redox potential and an equilibrium constant which was several orders of magnitude higher. The predominant area of magnetite stability was enlarged to cover a wider range of both pH and redox potentials as compared to that of a noncolloidal magnetite system.
Iron and 4-(methylamino)benzoic acid have been successfully incorporated into silica extracted from rice husk. The silica/Fe/amine complex, RH-Fe(5% amine), showed a ca. 24% increase in specific surface area compared to RH-Fe. This increase was attributed to the templated formation of regular pores. The XRD showed the RH-Fe(5% amine) to be amorphous. The Friedel-Crafts benzylation reaction with toluene using RH-Fe(5% amine) showed a drastic reduction in the di-substituted products to ca. 1.0%.
Limestone has been proven effective in removing metals from water and wastewater. A literature review indicated that limestone is capable of removing heavy metals such as Cu, Zn, Cd, Pb, Ni, Cr, Fe and Mn are through a batch process or by filtration technique. The removal capability is reported at up to 90%. However, to date most of the studies have been focused on synthetic wastewater. The present study attempts to investigate the suitability of limestone to attenuate total iron (Fe) from semi aerobic leachate at Pulau Burung Landfill Site in Penang, Malaysia. Iron was found in significant quantities at the landfill site. The study also aims to establish the Fe isotherm and breakthrough time of the proposed limestone filter for post-treatment to the migrating landfill leachate before its release to the environment. The Fe isotherms were established using a batch equilibrium test, while the breakthrough characteristics were determined using continuous flow permeating through a limestone column. The latter was used in order to simulate the continuous flow of leachate that would occur in the proposed limestone filter. The limestone media used in the experiment contain more than 90% CaCO3 with particle sizes ranging from 2 to 4 mm. Four filter columns (each 150 mm in diameter and 1000 mm depth) were installed at the landfill site. Metal loadings were kept below 0.5 kg /m3 day and the experiment was run continuously for 30 days. Initial results indicated that 90% of Fe can be removed from the leachate based on retention time of 57.8 min and surface loading of 12.2 m3/m2 day. For the batch study on the Fe isotherm, the results indicated that limestone is potentially useful as an alternative leachate treatment system at a relatively low cost.
The efficiency of advanced oxidation processes (AOPs), enzymatic treatment and combined enzymatic/AOP sequences for the colour remediation of soda and chemimechanical pulp and paper mill effluent was investigated. The results indicated that under all circumstances, the AOP using ultraviolet irradiation (photo-Fenton) was more efficient in the degradation of effluent components in comparison with the dark reaction. It was found that both versatile peroxidase (VP) from Bjerkandera adusta and laccase from Trametes versicolor, as pure enzymes, decolorize the deep brown effluent to a clear light-yellow solution. In addition, it was found that in the laccase treatment, the decolorization rates of both effluents were enhanced in the presence of 2, 2'-azinobis (3-ethylbenzthiazoline-6-sulfonate), while in the case of VP, Mn(+2) decreased the efficiency of the decolorization treatment. The concomitant use of enzymes and AOPs imposes a considerable effect on the colour remediation of effluent samples.
Bacteria with the ability to tolerate, remove, and/or degrade several xenobiotics simultaneously are urgently needed for remediation of polluted sites. A previously isolated bacterium with sodium dodecyl sulfate- (SDS-) degrading capacity was found to be able to reduce molybdenum to the nontoxic molybdenum blue. The optimal pH, carbon source, molybdate concentration, and temperature supporting molybdate reduction were pH 7.0, glucose at 1.5% (w/v), between 25 and 30 mM, and 25°C, respectively. The optimum phosphate concentration for molybdate reduction was 5 mM. The Mo-blue produced exhibits an absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. None of the respiratory inhibitors tested showed any inhibition to the molybdenum-reducing activity suggesting that the electron transport system of this bacterium is not the site of molybdenum reduction. Chromium, cadmium, silver, copper, mercury, and lead caused approximately 77, 65, 77, 89, 80, and 80% inhibition of the molybdenum-reducing activity, respectively. Ferrous and stannous ions markedly increased the activity of molybdenum-reducing activity in this bacterium. The maximum tolerable concentration of SDS as a cocontaminant was 3 g/L. The characteristics of this bacterium make it a suitable candidate for molybdenum bioremediation of sites cocontaminated with detergent pollutant.
In this study, effect of degree of deacetylation on property and adsorption capacity of chitosan/polyvinyl Alcohol electrospun membrane has been investigated. Resulting nanofibers were characterized by FESEM, FTIR, XRD, TGA, tensile testing, weight loss test and adsorption test. FESEM result shows, finer nanofiber was fabricated from 42h hydrolyzed chitosan and PVA blend solution. FTIR and XRD result showed a strong interaction between chitosan and polyvinyl alcohol. Higher tensile strength was observed for the nanofiber having 42h hydrolyzed chitosan. Blend solution of chitosan/PVA having low DD chitosan had higher viscosity. The nanofibrous membrane was stable in distilled water, acidic and basic medium. The isotherm study shows that the adsorption capacity (qm) of nanofiber containing higher DD chitosan was higher for Cr(VI). In contrary, the membrane containing chitosan with lower DD showed the higher adsorption capacity for Fe(III) and methyl orange. Moreover, the effect of DD on removal percentage of adsorbate was dependent on the initial concentration of the adsorbate.
This study evaluated the effectiveness of Fenton's technique for the treatment of semi-aerobic landfill leachate collected from Pulau Burung Landfill Site (PBLS), Penang, Malaysia. The Fe2+ or Fe3+ as catalyst and H2O2 as oxidizing agent are commonly used for the classical Fenton's reaction. In present study, the effect of operating conditions such as pH, reaction time, molar ratio, agitation rate, feeding mode and Fenton reagent concentrations which are important parameters that affect the removal efficiencies of Fenton method were investigated. Under the most favorable conditions, the highest removals of 58.1 and 78.3% were observed for COD and color, respectively. In general, the best operating conditions were pH = 3, Fe = 560 mg L(-1), H2O2 = 1020 mg L(-1), H2O2/Fe2+ molar ratio = 3, agitation rate = 400 rpm and reaction time = 120 minutes. The results highlighted that stepwise addition of Fenton's reagent was more effective than adding the entire volume in a single step. Excessive hydrogen peroxide and iron have shown scavenging effects on hydroxyl radicals and reduced degradation of refractory organics in the landfill leachate.
Leachate pollution is one of the main problems in landfilling. Researchers have yet to find an effective solution to this problem. The technology that can be used may differ based on the type of leachate produced. Coliform bacteria were recently reported as one of the most problematic pollutants in semi-aerobic (stabilized) leachate. In the present study, the performance of the Electro-Fenton process in removing coliform from leachate was investigated. The study focused on two types of leachate: Palau Borung landfill leachate with low Coliform content (200 MPN/100 m/L) and Ampang Jajar landfill leachate with high coliform content (>24 × 10(4)MPN/100 m/L). Optimal conditions for the Electro-Fenton treatment process were applied on both types of leachate. Then, the coliform was examined before and after treatment using the Most Probable Number (MPN) technique. Accordingly, 100% removal of coliform was obtained at low initial coliform content, whereas 99.9% removal was obtained at high initial coliform content. The study revealed that Electro-Fenton is an efficient process in removing high concentrations of pathogenic microorganisms from stabilized leachate.