Asphaltene-derived nanocomposites for the removal of emerging pollutants and its antimicrobial effects: batch and continuous column studies

Emerging contaminants are diverse ecotoxic materials requiring unique treatment for removal. Asphaltenes are environmentally hazardous carbon-rich solid waste product of the petroleum industry. In the current work, asphaltene-derived activated carbon (AC) was loaded with silver (Ag/AC) and used to remove amoxicillin (AMX) and tetracycline (TC) from aqueous phase. The prepared Ag/AC was characterised using FESEM, FTIR, XRD and surface area analysis. The FESEM micrographs confirmed the spherical silver nanoparticle-laden porous AC, and the BET surface area was found to be 213 m2/g. Batch adsorption studies were performed, and the equilibrium data were fit into adsorption isotherm and kinetic models. The Ag/AC exhibited superior monolayer adsorption capacity of 1012 mg/g and 770 mg/g for AMX and TC, respectively. The continuous column studies were also performed to evaluate the breakthrough parameters. Furthermore, the antimicrobial activity of the adsorbent was evaluated using zone of inhibition studies. Ag/AC was found to have an 8-mm-diameter zone of microbial inhibition. The obtained results showed that Ag/AC was a promising material for the removal of antibiotics and inhibition of resistance-developed mutated microbes in effluent water.

Photocatalytic reduction of chromium(VI) using multiwall carbon nanotubes/bismuth oxide nanocomposite under solar irradiation

Semiconductor photocatalysis is the most efficient advanced oxidation processes for wastewater treatment. A new carbon-based photocatalyst bismuth oxide/multi-walled carbon nanotube (Bi2O3/MWCNT) nanocomposite has a considerable impact on improving photocatalytic performance. Bi2O3/MWCNTs (BMC) nanocomposite was prepared through the hydrothermal processing with 2.5, 5, 7.5 and 10 wt% of MWCNTs. The prepared photocatalysts have been thoroughly examined by various techniques. The X-ray diffraction confirmed the prepared photocatalyst as α-Bi2O3 with high crystallinity. The band gap of Bi2O3 and BMC 7.5 nanocomposite was found to be 2.41 and 1.94 eV. The prepared photocatalyst revealed smooth and porous merged flower-like structure with respect to the addition of MWCNTs. The model pollutant chromium(VI) (Cr(VI)) has been used to check the reduction efficiency of the prepared photocatalyst under solar irradiation. It was found that BMC 7.5 nanocomposite showed enhanced photocatalytic metal ion reduction (87.48%) compared to pristine Bi2O3 (69.29%). The preliminary photocatalytic Cr(VI) ion reduction experiments were carried to determine the photoreduction efficiency of pristine bismuth oxide and bismuth MWCNT nanocomposite. The kinetic study on Cr(VI) ion reduction obeyed pseudo-first-order rate kinetics for both the prepared photocatalysts. The efficiency of the photocatalysts was further analysed by reusing the same up to 3 cycles without loss of the efficacy.

Polymeric graphitic carbon nitride layers decorated with erbium oxide and enhanced photocatalytic performance under visible light irradiation

Developing and implementing visible light active organic-inorganic hybrid semiconductor nanomaterials with enhanced photocatalytic properties find newer environmental and energy treatment capabilities. Here, we are reporting polymeric g-C₃N₄ layers coated with different propositions of erbium oxide nanoparticles, characterized using XPS, UV-Vis-DRS, FT-IR, HR-TEM, FE-SEM, elemental mapping, XRD and surface area techniques and its photocatalytic activities were evaluated under visible light irradiations. The hybrid nanocomposite materials possess better crystalline nature and erbium oxide particles were on the surface of polymeric g-C₃N₄. The surface area and bandgap energy of the polymeric g-C₃N₄-erbium oxide (5 wt%) nanohybrid composite were 99.9 m²/g and 2.52 eV. The photocatalytic activities as prepared nanohybrid composites were assessed for the oxidation of orange G dye molecules in the presence of visible light and were highly active in a broader range of pH with the presence of various inorganic anions. The rate of photocatalytic oxidation of dye molecules varied from 4.79 × 10^-4 to 1.77 × 10^-4 min^-1 for the initial concentration of 5 to 20 ppm and retained its activities above 95% up to three cycles of reusability. Hence, the organic-inorganic novel catalytic nanohybrid composite may find more comprehensive applications in the area of environmental and energy applications.

Nanorod-like Structure of ZnO Nanoparticles and Zn8O8 Clusters Using 4-Dimethylamino Benzaldehyde Liquid to Study the Physicochemical and Antimicrobial Properties of Pathogenic Bacteria

To study their physicochemical and antimicrobial properties, zinc oxide nanoparticles were synthesized using a simple chemical route and 4-dimethylaminobenzaldehyde (4DB) as an organic additive. ZnO nanoparticles were characterized with XRD analysis, which confirmed the presence of a hexagonal wurtzite structure with different crystalline sizes. The SEM morphology of the synthesized nanoparticles confirmed the presence of nanorods in both modifications of ZnO nanoparticles. EDS analysis proved the chemical composition of the synthesized samples via different chemical approaches. In addition, the optical absorption results indicated that the use of 4DB increased the band gap energy of the synthesized nanoparticles. The synthesized Zn₈O₈ and Zn₈O₈:4DB clusters were subjected to HOMO-LUMO analysis, and their ionization energy (I), electron affinity (A), global hardness (η), chemical potential (σ), global electrophilicity index (ω), dipole moment (μ), polarizability (α_tot), first-order hyperpolarizability (β_tot), and other thermodynamic properties were determined. Furthermore, the antimicrobial properties of the ZnO nanoparticles were studied against G+ (S. aureus and B. subtilis) and G- (K. pneumoniae and E. coli) bacteria in a nutrient agar according to guidelines of the Clinical and Laboratory Standards Institute (CLSI).

Green Chemical Synthesis of N-Cholyl-L-Cysteine Encapsulated Gold Nanoclusters for Fluorometric Detection of Mercury Ions

Herein we report a simple, single-step, cost-effective, environmentally friendly, and biocompatible approach using sodium salt of N-cholyl-L-cysteine (NaCysC) capped gold nanoclusters (AuNCs) with green emission properties at above the CMC in aqueous medium under UV-light irradiation. The primary and secondary CMC of NaCysC was found to be 4.6 and 10.7 mM respectively using pyrene as fluorescent probe. The synthesized AuNCs exhibit strong emission maxima at 520 nm upon excitation at 375 nm with a large Stokes shift of 145 nm. The surface functionality and morphology of NCs are studied by fourier transform infrared spectroscopy, dymanic light scattering studies and transmission electron microscopy. The formation of AuNCs was completed within 5 h and exhibit high stability for more than 6 months. The NaCysC templated AuNCs selectively quenches the Hg²⁺ ions with higher sensitivity in aqueous solution over the other metal ions. The fluorescence analysis of Hg²⁺ showed a wide linear range from 15 to 120 µM and a detection limit was found to be 15 nM.

Hexagonal nanostructured cobalt oxide @ nitrogen doped multiwalled carbon nanotubes/polypyyrole composite for supercapacitor and electrochemical glucose sensor

Hexagonal nanostructured cobalt oxide @ N-doped MWCNT /polypyyrole (Co₃O₄/PPy@N-MWCNT) composite was produced by an ultrasonication-mediated solvothermal method for electrochemical supercapacitor and glucose sensor applications. The structural and electrochemical properties of the Co₃O₄/PPy@N-MWCNT were confirmed by various spectroscopic and microscopic techniques. The as-prepared electrode showed an excellent capacitance of ∼872 F/g at 0.5 A/g with a capacitance retention of 96.8 %, even after 10,000 cycles. In addition, analysis of the sensing activity of the composite materials towards the glucose detection showed excellent electrochemical sensing performance that includes the glucose linear limit of (10 to 0.15) μm, detection sensitivity of 195.72 μA/cm²/mM, and lower detection value of S = 0.07327 μA/cm² @ R² = 0.99. The as-prepared composite material can be a promising candidate for the electrochemical supercapacitor and the efficient sensing of glucose.

Nanocrystalline ZnO as a Visible Active Photocatalyst for the Degradation of Benzene-1,4-diol

We have synthesized nanocrystalline ZnO by a simple precipitation method. The prepared ZnO was found to be highly phase pure and nanocrystalline hexagonal wurtzite structure. UV–Visible–DRS spectroscopy showed the material to have bandgap energy of 3.22[Formula: see text]eV. HR-SEM image revealed the material to be made up of distinct hexagonal particles with a highly porous surface. AFM analysis was employed to confirm the high surface roughness and porosity of the material. The photocatalytic activity of the prepared ZnO was evaluated by the degradation of benzene-1,4-diol (hydroquinone), under visible light irradiation. Preliminary experiments showed the catalyst to be effective at neutral pH with an optimum catalyst dosage of 4[Formula: see text]g/L. Kinetic studies showed the degradation reaction to follow pseudo-first-order kinetics. In the presence of commonly used industrial electrolytes, the catalyst exhibited a decrease in efficiency. Reusability studies showed the catalytic efficiency of ZnO to diminish marginally after the third cycle of reuse.

Graphene oxide coated with porous iron oxide ribbons for 2, 4-Dichlorophenoxyacetic acid (2,4-D) removal

Graphene oxide (GO) was prepared from commercially available graphite powder. Porous iron oxide ribbons were grown on the surface of GO by solvothermal process. The prepared GO-Fe₃O₄ nanocomposites are characterized by FT-IR, XRD, VSM, SEM, TEM, Raman spectroscopy, surface functionality and zero point charge studies. The morphology of the iron oxide ribbons grown on GO is demonstrated with TEM at various magnifications. The presence of magnetite nanoparticles is evident from XRD peaks and the magnetization value is found to be 37.28emu/g. The ratio of intensity of D-peak to G-peak from Raman spectrum is 0.995. The synthesized Graphene oxide-Fe₃O₄ nanocomposites (GO-Fe₃O₄) were explored for its surface adsorptive properties by using a model organic compound, 2,4-Dichlorophenoxy acetic acid (2,4-D) from aqueous solution. Batch adsorption studies were performed and the equilibrium data are modelled with Langmuir, Freundlich and Temkin isotherms. The maximum monolayer capacity from Langmuir isotherm is 67.26mg/g. Kinetic studies were also carried out and the studied adsorption process followed pseudo second-order rate equation. Mechanism of the adsorption process is studied by fitting the data with intraparticle diffusion model and Boyd plot. The studied adsorption process is both by film diffusion and intraparticle diffusion.

High-performance N-doped MWCNT/GO/cellulose hybrid composites for supercapacitor electrodes

A nitrogen-doped MWCNT/GO/cellulose hybrid composite was prepared via an in situ hydrothermal process, and its electrochemical performance was evaluated by conducting cyclic voltammetry (CV).

Synthesis and characterization of zinc oxide nanorods and its photocatalytic activities towards degradation of 2,4-D

Semiconductor zinc oxide nanorods (NRZnO) were prepared by sol-gel technique using zinc acetate as the precursor and ammonia as the precipitating agent. The prepared photocatalyst were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), UV-Visible diffuse reflectance spectroscopy (UV-Vis-DRS), X-ray photoelectron spectroscopy (XPS), Field Emission-Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM), High Resolution-Tunneling Microscope (HR-TEM), Brunauer, Emmett and Teller (BET) and electron paramagnetic resonance spectroscopy (EPR) analysis. Particle size of the prepared photocatalyst was established by XRD and FE-SEM analysis. The morphology and the formation of uniform NRZnO was controlled by the temperature, entire concentration of precursors, duration of aging process. High surface roughness and porosity confirmed by AFM analysis. Band gap energy of the synthesized photocatalyst (3.2eV) was determined by using diffuse reflectance spectroscopy. The in-situ production of OH radicals by the prepared photocatalyst was confirmed by electron paramagnetic resonance spectroscopy (EPR) spin trapping technique. The photocatalytic activity of prepared NRZnO was evaluated by photo degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D) under UV and visible light irradiations. Experimental parameter such as effect of pH, catalyst dosage, initial 2, 4- D concentrations and addition of different electrolytes on the degradation of 2, 4-D was also studied in detail. Neutral pH was found to be the optimum and catalyst dosage of 30mg/10ml resulted in higher percentage of degradation. The photo degraded samples were analyzed by chemical oxygen demand (COD) analysis, UV-Visible spectroscopy. Reusability of the prepared photocatalyst was tested upto three cycles without affecting its performance. The experimental shown the rate of degradation follows pseudo-first order rate kinetics with respect to 2, 4 D.

Nitrogen doped nanocrystalline semiconductor metal oxide: An efficient UV active photocatalyst for the oxidation of an organic dye using slurry Photoreactor

Water pollution is a cause for serious concern in today's world. A major contributor to water pollution is industrial effluents containing dyes and other organic molecules. Waste water treatment has become a priority area in today's applied scientific research as it seeks to minimize the toxicity of the effluents being discharged and increase the possibility of water recycling. An efficient and eco-friendly way of degrading toxic molecules is to use nano metal-oxide photocatalysts. The present study aims at enhancing the photocatalytic activity of a semiconductor metal oxide by doping it with nitrogen. A sol-gel cum combustion method was employed to synthesize the catalyst. The prepared catalyst was characterized by FT-IR, XRD, UV-DRS, FESEM and AFM techniques. UV-DRS result showed the catalyst to possess band gap energy of 2.97eV, thus making it active in the UV region of the spectrum. Its photocatalytic activity was evaluated by the degradation of a model pollutant-Orange G dye, under UV light irradiation. Preliminary experiments were carried out to study the effects of pH, catalyst dosage and initial dye concentration on the extent of dye degradation. Kinetic studies revealed that the reaction followed pseudo first order kinetics. The effect of electrolytes on catalyst efficiency was also studied. The progress of the reaction was monitored by absorption studies and measuring the reduction in COD. The catalyst thus prepared was seen to have a high photocatalytic efficiency. The use of this catalyst is a promising means of waste water treatment.

Sonocatalytic degradation of malachite green oxalate by a semiconductor metal oxide nanocatalyst

Advanced Oxidation Process (AOP) technologies are considered to be better technique for the degradation or mineralization of many recalcitrant compounds and pollutants. In the present study heterogeneous sonocatalytic degradation of a model organic compound such as Malachite green oxalate (MGO) was carried out in the aqueous phase. Zinc oxide nanorods were prepared by precipitation method employing zinc acetates as precursors and were characterized by FT-IR, XRD, FE-SEM and EDAX analysis. Degradation of MGO in the aqueous phase was studied in detail under the sonocatalytic process. Effects of pH, dye concentration, oxidant concentration, kinetics and effect of electrolytes on dye degradation were carried out to check the efficiency of the sonocatalyst. Effect of energy input on the degradation processes was also investigated. The degradation of dye molecules were monitored by UV-visible spectrophotometer and Chemical Oxygen demand (COD). The dye molecules were readily degraded at above 90% in the pH range 5.0-7.0 under ultrasound with zinc oxide nanorods. The interference of electrolytes like NaCl, KCl, Na₂CO₃, NaHCO₃ and MgSO₄ on the degradation of dye molecules were also studied on the sonocatalytic degradation of MGO. From the kinetic studies it was observed that at lower initial concentration of dye molecules the degradation efficiency was above 90%. The rate of the reaction decreased on increasing the initial dye concentrations of the dye molecules. It was observed that the complete mineralization of dye molecules was achieved without the formation of toxic by-products. The reusability of the catalyst also showed the effective degradation of the dye molecules up to five cycles without loss of the catalytic activities.

Enhanced visible photocatalytic activity of cotton ball like nano structured Cu doped ZnO for the degradation of organic pollutant

Stringent Environmental standards followed worldwide led to the emergence of advanced oxidation process for the removal of toxic contaminants from water and wastewater. Among all semiconductor photocatalysts have great potential in the degradation of organic and inorganic pollutants into lesser harmful products under visible light irradiations. The present research work describes the synthesis of Cu doped ZnO (CuDZ) via a co-precipitation method to attain high crystallized powder confirmed by XRD analysis. The FE-SEM images showed that the CuDZ has cotton ball like morphology with a uniform size ranged from 25 to 40nm. TEM, FT-IR and UV-DRS studies of the synthesized CuDZ are also discussed in detail. The photocatalytic activity of the as prepared CuDZ catalyst was tested for the degradation of Direct Blue 71 (DB 71) dye in aqueous phase under visible light irradiation. The degree of degradation was found to be dependent on aqueous phase pH, duration of irradiation time, amount of photocatalyst, the initial dye concentration and kinetics of photodegradation. The maximum photocatytic degradation of DB 71 dye was found to be effective at pH 6.8. The optimum amount of photocatalyst was found 3gL^-1 of CuDZ for the complete degradation of DB 71 dye (0.01gL^-1). The reusability of the photocatalyst indicates that 96% of DB 71 dye was degraded up to 3rd cycles of use. The visible photodegradation of DB 71 dye was exhibited pseudo-first-order kinetics. Chemical oxygen demand and ESI-MS studies confirmed the complete mineralization of DB 71 dye molecules.

Nanocrystalline semiconductor doped rare earth oxide for the photocatalytic degradation studies on Acid Blue 113: A di-azo compound under UV slurry photoreactor

Preventive measures for the control of environmental pollution and its remediation has received much interest in recent years due to the world-wide increase in the contamination of water bodies. Contributions of these harmful effluents are caused by the leather processing, pharmaceutical, cosmetic, textile, agricultural and other chemical industries. Nowadays, advanced oxidation processes considered to be better option for the complete destruction of organic contaminants in water and wastewater. Acid Blue 113 is a most widely used di-azo compound in leather, textile, dying and food industry as a color rending compound. In the present study, we have reported the photo catalytic degradation of Acid Blue 113 using a nanocrystalline semiconductor doped rare earth oxide as a photo catalyst under UV light irradiation. The photocatalyst was prepared by a simple precipitation technique and were characterized by XRD, FT-IR, UV-DRS and FE-SEM analysis. The experimental results proved that the prepared photo catalyst was nanocrystalline and highly active in the UV region. The UV-DRS results showed the band gap energy was 3.15eV for the prepared photo catalyst. The photodegradation efficiency was analyzed by various experimental parameters such as pH, catalyst dosage, variation of substrate concentration and effect of electrolyte addition. The photo degradation process followed a pseudo first order kinetics and was continuously monitored by UV-visible spectrophotometer. The experimental results proved the efficacy of the nanocrystalline zinc oxide doped dysprosium oxide which are highly active under UV light irradiations. It is also suggested that the prepared material would find wider applications in environmental remediation technologies to remove the carcinogenic and toxic moieties present in the industrial effluents.

Preparation of char from lotus seed biomass and the exploration of its dye removal capacity through batch and column adsorption studies

Char was obtained from lotus seed biomass by a simple single-step acid treatment process. It was used as an adsorbent for the removal of malachite green dye (MG) from simulated dye bath effluent. The adsorbent was characterized for its surface morphology, surface functionalities, and zero point charge. Batch studies were carried out by varying the parameters such as initial aqueous pH, adsorbent dosage, adsorbent particle size, and initial adsorbate concentration. Langmuir and Freundlich isotherms were used to test the isotherm data and the Freundlich isotherm best fitted the data. Thermodynamic studies were carried out and the thermodynamic parameters such as ∆G, ∆H, and ∆S were evaluated. Adsorption kinetics was carried out and the data were tested with pseudofirst-order model, pseudosecond-order model, and intraparticle diffusion model. Adsorption of MG was not solely by intraparticle diffusion but film diffusion also played a major role. Continuous column experiments were also conducted using microcolumn and the spent adsorbent was regenerated using ethanol and was repeatedly used for three cycles in the column to determine the reusability of the regenerated adsorbent. The column data were modeled with the modeling equations such as Adam-Bohart model, Bed Depth Service Time (BDST) model, and Yoon-Nelson model for all the three cycles.

Preparation and characterization of corn cob activated carbon coated with nano-sized magnetite particles for the removal of Cr(VI)

Activated carbon prepared from corn cob biomass, magnetized by magnetite nanoparticles (MCCAC) was used for the adsorption of hexavalent chromium from aqueous solution. The adsorbent was characterized by SEM, TEM, XRD, VSM, surface functionality and zero-point charge. The iron oxide nanoparticles were of 50 nm sizes and the saturation magnetization value for the adsorbent is 48.43 emu/g. Adsorption was maximum at pH 2. Isotherm data were modeled using Langmuir, Freundlich and Temkin isotherm. The prepared MCCAC had a heterogeneous surface. The maximum monolayer adsorption capacity was 57.37 mg/g. Kinetic studies were carried out and the data fitted the pseudo second-order equation. The mechanism of the adsorption process was studied by incorporating the kinetic data with intraparticle diffusion model, Bangham equation and Boyd plot. The adsorption was by chemisorption and the external mass transfer was the rate-determining step. A micro column was designed and the basic column parameters were estimated.

Synthesis and characterization of maleimide-functionalized polystyrene-SiO2/TiO2 hybrid nanocomposites by sol-gel process

Maleimide-functionalized polystyrene (PSMA-SiO2/TiO2) hybrid nanocomposites were prepared by sol-gel reaction starting from tratraethoxysilane (TEOS) and titanium isopropoxide in the solution of polystyrene maleimide in 1,4-dioxane. The hybrid films were obtained by the hydrolysis and polycondensation of TEOS and titanium isopropoxide in maleimide-functionalized polystyrene solution followed by the Michael addition reaction. The transparency of polymer (PSMA-SiO2/TiO2) hybrid was prepared from polystyrene titanium isopropoxide using the γ-aminopropyltriethoxy silane as crosslinking agent by in situ sol-gel process via covalent bonding between the organic-inorganic hybrid nanocomposites. The maleimide-functionalized polystyrene was synthesized by Friedel-Crafts reaction from N-choloromethyl maleimide. The FTIR spectroscopy data conformed the occurrence of Michael addition reaction between the pendant maleimide moieties of the styrene and γ-aminopropyltriethoxysilane. The chemical structure and morphology of PSMA-SiO2/TiO2 hybrid nanocomposites were characterized by FTIR, nuclear magnetic resonance (NMR), 13 C NMR, SEM, XRD, and TEM analyses. The results also indicate that the inorganic particles are much smaller in the ternary systems than in the binary systems; the shape of the inorganic particles and compatibility for maleimide-functionalized polystrene and inorganic moieties are varied with the ratio of the inorganic moieties in the hybrids. Furthermore, TGA and DSC results indicate that the thermal stability of maleimide-functionalized polystyrene was enhanced through the incorporation of the inorganic moieties in the hybrid materials.

Equilibrium, kinetic and thermodynamic studies on the biosorption of reactive acid dye on Enteromorpha flexuosa and Gracilaria corticata

PURPOSE

Biosorption is an emerging, eco-friendly and economical method for treating the wastewater effluents. Compared to many other biological materials, algae biomass proved to be the better biosorbent due to the presence of cell wall polymers in them.

METHODS

Algal biomasses namely Enteromorpha flexuosa and Gracilaria corticata were dried, crushed and used as biosorbents. Ponceau S, a diazo dye was used as a model adsorbate for the biosorption studies. The biosorbents were characterized by Scanning Electron Microscopy, FT-IR and zero point charge. Batch studies were performed by varying pH, biosorbent dosage and initial dye concentrations. Adsorption isotherms, kinetic and thermodynamic analyses were carried out. The effect of electrolytes was also studied. Batch desorption studies were also carried out using various reagents.

RESULTS

Isotherm data were tested with Langmuir and Freundlich isotherm models and the results suggested that the Freundlich isotherm fitted the data well. Kinetic studies were performed with varying initial dye concentrations and the data were incorporated with pseudo first-order and pseudo second-order kinetic equations and was found that the studied biosorption processes followed pseudo second-order kinetic equation. Thermodynamic parameters were evaluated at three different temperatures 293 K, 300 K and 313 K. About 95% of the dye could be desorbed from both the biosorbents.

CONCLUSION

Both the algal biomasses had heterogeneous surfaces and followed pseudo second-order chemical kinetics. Thermodynamic parameters proved that the biosorption by both the biomasses were spontaneous, feasible and endothermic processes. Desorption studies proved the worth of the algal biomasses as biosorbents in industrial level.

Photocatalytic degradation of Orange G dye under solar light using nanocrystalline semiconductor metal oxide

INTRODUCTION

The photocatalytic degradation of Orange G (OG) dye has been investigated using synthesised nanocrystalline ZnO as a photocatalyst and sunlight as the irradiation source. The formation of ZnO prepared from its precursor was confirmed through FT-IR and powder X-ray diffraction analyses.

MATERIALS AND METHODS

Surface morphology was characterised by scanning electron microscope and transmission electron microscope analysis. Band gap energy of synthesised nanocrystalline ZnO was calculated using diffuse reflectance spectroscopy (DRS). Different experimental parameters such as effects of pH, dye concentrations and mass of catalyst were standardised in order to achieve complete degradation of the dye molecules under solar light irradiation.

RESULTS

The kinetics of oxidation of OG was also studied. The complete degradation of OG was evident after 90 min of irradiation at an initial pH of 6.86. The degradation of OG was confirmed by UV-Visible spectrophotometer, high-pressure liquid chromatography, ESI-Mass and chemical oxygen demand analyses.

CONCLUSION

The adsorption of dye onto catalytic surface was analysed employing model equations such as Langmuir and Freundlich isotherms, and it was found that the Langmuir isotherm model best fitted the adsorption data. The solar photodegradation of OG followed pseudo-first-order kinetics. HPLC and ESI-Mass analyses of the degraded samples suggested that the dye molecules were readily degraded under solar irradiation with nanocrystalline ZnO.

Adsorptive removal of an acid dye by lignocellulosic waste biomass activated carbon: equilibrium and kinetic studies

Chemically prepared activated carbon material derived from palm flower was used as adsorbent for removal of Amido Black dye in aqueous solution. Batch adsorption studies were performed for the removal of Amido Black 10B (AB10B), a di-azo acid dye from aqueous solutions by varying the parameters like initial solution pH, adsorbent dosage, initial dye concentration and temperature with three different particle sizes such as 100 μm, 600 μm and 1000 μm. The zero point charge was pH 2.5 and the maximum adsorption occurred at the pH 2.3. Experimental data were analyzed by model equations such as Langmuir, Freundlich and Temkin isotherms and it was found that the Freundlich isotherm model best fitted the adsorption data and the Freundlich constants varied from (K(F)) 1.214, 1.077 and 0.884 for the three mesh sizes. Thermodynamic parameters such as ΔG, ΔH and ΔS were also calculated for the adsorption processes and found that the adsorption process is feasible and it was the endothermic reaction. Adsorption kinetics was determined using pseudo first-order, pseudo second-order rate equations and also Elovich model and intraparticle diffusion models. The results clearly showed that the adsorption of AB10B onto lignocellulosic waste biomass from palm flower (LCBPF) followed pseudo second-order model, and the pseudo second-order rate constants varied from 0.059 to 0.006 (g mg(-1)min) by varying initial adsorbate concentration from 25 mg L(-1) to 100 mg L(-1). Analysis of the adsorption data confirmed that the adsorption process not only followed intraparticle diffusion but also by the film diffusion mechanism.

Adsorption of Malachite Green dye onto activated carbon derived from Borassus aethiopum flower biomass

In the present study, chemically prepared activated carbon derived from Borassus aethiopum flower was used as adsorbent. Batch adsorption studies were performed for the removal of Malachite Green (MG) from aqueous solutions by varying the parameters like initial solution pH, adsorbent dosage, initial MG concentration and temperature with three different particle sizes such as 100 microm, 600 microm and 1000 microm. The zero point charge was 2.5 and the maximum adsorption occurred at the pH range from 6.0 to 8.0. Experimental data were analyzed by model equations such as Langmuir, Freundlich and Temkin isotherms and it was found that the Langmuir isotherm model best fitted the adsorption data. Thermodynamic parameters such as DeltaG, DeltaH and DeltaS were also calculated for the adsorption processes. Adsorption rate constants were determined using pseudo first-order, pseudo second-order rate equations and also Elovich model and intraparticle diffusion models. The results clearly showed that the adsorption of MG onto PFAC followed pseudo second-order model and the adsorption was both by film diffusion and by intraparticle diffusion.

Synthesis and Characterization of 3,3′-bis (3-maleimidophenyl) Phenyl Phosphine Oxide (BMI)/1, 3-Cyanatobenzene Epoxy Inter-crosslinked Matrices for Engineering Applications

Cyanate ester (CE) -3,3′-bis (3-maleimidophenyl) phenyl phosphine oxide (BMI)-modified epoxy matrices were made by using epoxy resin (DGEBA) and 1,3-dicyantobenzene and diaminodiphenyl methane as a curing agent. The properties of BMI-CE epoxy matrices were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis, scanning electron microscopy, water absorption behavior and heat deflection temperature. The matrices were also characterized for their mechanical properties such as tensile strength, flexural strength and unnotched Izod impact strength by ASTM methods. The mechanical and tensile properties were improved by increasing the percentage of the CE in the epoxy resin. DSC thermograms of 1,3-dicyantobenzene as well as BMI-modified epoxy resin showed an unimodal reaction exothermicity.

In situ biodecolorization kinetics of Acid Red 66 in aqueous solutions by Trametes versicolor

The biological decolorization methodology and the mechanism involved in the degradation of Acid Red 66 was chosen as a model of azo dye using the white rot fungi Trametes versicolor was studied. Biodecolorization of Acid Red 66 using white rot fungi T. versicolor was demonstrated by the decolorization of the culture medium, the extent of which was determined by monitoring the decrease in absorbance at 506 nm. The biodecolorization kinetics of Acid Red 66 (100 ppm) was found to be first order and the degradation rate coefficient is 1.312 x 10(-2)min(-1) (R=0.96683, n=8) at 30 degrees C. The effects of independent variables such as carbon sources, nitrogen sources pH, and temperature on the biodecolorization of Acid Red 66 was also investigated.

Catalytic applications in the production of biodiesel from vegetable oils

The predicted shortage of fossil fuels and related environmental concerns have recently attracted significant attention to scientific and technological issues concerning the conversion of biomass into fuels. First-generation biodiesel, obtained from vegetable oils and animal fats by transesterification, relies on commercial technology and rich scientific background, though continuous progress in this field offers opportunities for improvement. This review focuses on new catalytic systems for the transesterification of oils to the corresponding ethyl/methyl esters of fatty acids. It also addresses some innovative/emerging technologies for the production of biodiesel, such as the catalytic hydrocracking of vegetable oils to hydrocarbons. The special role of the catalyst as a key to efficient technology is outlined, together with the other important factors that affect the yield and quality of the product, including feedstock-related properties and various system conditions.

Removal of rhodamine B from aqueous solution by adsorption onto sodium montmorillonite

The adsorption of rhodamine B dye was carried out using sodium montmorillonite clay. The effect of parameters such as pH, adsorbent dosage and initial dye concentration was studied. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best fit the equilibrium isotherm data. Langmuir adsorption capacity was found to be 42.19 mg/g. Kinetic data followed pseudo-second-order kinetics. Maximum color removal was observed at pH 7.0. The DeltaG degrees value was found to be negative, the adsorption process was feasible. The results indicate that sodium montmorillonite clay can be used for the removal of basic dyes from aqueous solutions.

Decolorization of textile dye effluent by genetically improved bacterial strains

Synthetic dyes are released into the environment from textile industrial effluents. The discharge of this colored wastewater into rivers and lakes leads to a reduction in sunlight penetration in natural water bodies, which, in turn, decreases both photosynthetic activity and dissolved oxygen concentration and is toxic to living beings. Bacterial isolates are optimized for growth and biomass production before using them for decolorizing dye effluent. The bacterial isolates Bacillus sp. 1 and Bacillus sp. 2 were employed at different percentages by volume with standard nutrient concentration. Of these bacterial isolates Bacillus sp. 2 recorded maximum color reduction. The pH and electrical conductivity (EC) were reduced in the decolorized effluent, and a reduction in biologic oxygen demand, chemical oxygen demand, total suspended solids, and total dissolved solids (TDS) were also observed.