TiO2 decorated functionalized halloysite nanotubes (TiO2@HNTs) and photocatalytic PVC membranes synthesis, characterization and its application in water treatment.

In this study photocatalyst, TiO2@HNTs were prepared by  synthesizing TiO2 nanoparticles in situ on the  functionalized halloysite nanotubes (HNTs) surface. Photocatalytic PVC membrane TiO2@HNTs M2 (2 wt.%) and TiO2@HNTs M3 (3 wt.%) were also prepared. Photocatalyst TiO2@HNTs and photocatalytic PVC membranes were used to study the photocatalytic activity against the methylene blue (MB) and rhodamine B (RB) dyes in UV batch reactor. The structure and morphology of photocatalyst and photocatalytic PVC membrane were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), UV-Vis spectrophotometer and photoluminescence (PL). The PL study showed that the oxygen vacancies and surface hydroxyl groups present on the surface of TiO2@HNTs act as excellent traps for charge carrier, reducing the electron-hole recombination rate.TiO2@HNTs 2 (2 wt.%) and TiO2@HNTs 3 (3 wt.%) degraded MB dye up to 83.21%, 87.47% and RB dye up to 96.84% and 96.87%, respectively. TiO2@HNT photocatalyst proved to be stable during the three consecutive cycle of photocatalytic degradation of the RB dye. TiO2@HNTs M2 and TiO2@HNTs M3 degraded MB dye up to 27.19%, 42.37% and RB dye up to 30.78%, 32.76%, respectively. Photocatalytic degradation of both the dyes followed the first-order kinetic model. Degradation product analysis was done using the liquid chromatography-mass spectrometry (LC-MS) and the results showed that the dye degradation was initiated by demethylation of the molecule. MB and RB dye degradation reaction were tested by TBA and IPA as OH* and H+ scavengers respectively. Mechanism of photocatalytic activity of TiO2@HNTs and photocatalytic PVC membrane were also explained.

Role of zinc oxide nanoparticles for effluent treatment using Pseudomonas putida and Pseudomonas aureofaciens.

The biological treatment of textile effluent is enhanced by the use of zinc oxide (ZnO) nanoparticles for the reduction in chemical oxygen demand (COD) from its initial value of 1700 ppm. The present research investigated the effect of ZnO nanoparticles when microbial cultures of Pseudomonas putida and Pseudomonas aureofaciens were used to treat textile effluent in three-phase inverse fluidized bed bioreactor. The parameters like-size of ZnO nanoparticles, static bed height, superficial gas velocities and solid media particle size-together affected the COD reduction and all of these were investigated in this paper. ZnO nanoparticles of 280 nm reduced the maximum COD to 47 ppm (97.24%) at low gas velocity of 0.0027 m/s at 10% inoculum size and at a static bed height of 2.43 cm.

Cerium oxide nanoparticles embedded thin-film nanocomposite nanofiltration membrane for water treatment.

In this paper, a new approach to synthesize thin-film nanocomposite membranes using cerium oxide (CeO2) nanoparticles (NPs) by pre-seeding interfacial polymerization method was reported. Prepared membranes were examined using contact angle, molecular weight cut-off (MWCO), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and scanning probe microscopy (SPM) to observe its hydrophilicity, pore size, morphology, surface chemistry, and roughness, respectively. Surface charges of the prepared membranes were also qualitatively calculated with the help of contact angle measurements by using the Grahame equation. MWCO studies revealed >90% polyethylene glycol (M.W. 1500 Da) rejection, which was fitted in the range of nanofiltration. By increasing the concentration of CeO2 NPs, flux (33.12 to 41.28 L/m2h), hydrophilicity (77.3 to 51.1°) and surface charges (-7.58 to -13.39 mC/m2) of the membranes was successfully improved, and also showed the high (>90%) salt rejections. The CeO2 embedded membrane was also found out in successful prevention from the attack of bacteria (Escherichia coli) compared to pure polyamide (PA) membrane and confirmed through SEM and viable cell count method. The membrane performances were also evaluated using seawater for fouling study and found that CeO2 embedded surface increased the rejection of hydrophobic contaminants, and notably reduced the fouling.

Process parametric study for COD removal of electroplating industry effluent.

This paper investigated the effects of parameters, like inoculum size (15, 10 and 5% of the working volume of the reactor), gas velocities (0.0027, 0.00342 and 0.0068 m/s), bed heights (0.3, 0.6 and 0.9 m), static bed heights (4.85 and 2.43 cm), sizes of solid media particles (12, 4 mm), and the height to diameter ratio (H/D: 0.25 and 0.5) onto COD reduction process for electroplating effluent (initial COD values: 1140 ppm) using Pseudomonas aeruginosa and Pseudomonas putida. The authors derived simple mathematical correlations representing the entire COD reduction process. The correlation between the inoculum volume and gas velocities was in the form of an equation Y = ax2 + bx + c, as deduced from nonlinear regressions. The correlations were validated, and percentage errors were found out to infer the effects of all parameters in the COD reduction process. The maximum COD reduction was achieved to 28.30 ppm (97.52%), in a batch mode, at 10% inoculum size, 0.0027 m/s low gas velocity and a static bed height of 2.43 cm.

Immobilization of lipase on carboxylic acid-modified silica nanoparticles for olive oil glycerolysis.

In this study, the silica nanoparticles surface was modified by carboxylic acid with different number of alkyl chain and two different lipases were immobilized on it to increase the glycerolysis activity of the immobilized lipases in organic solvent system. Silica nanoparticles of about 15 nm diameter were grafted with various carboxylic acid modifiers from valeric, caprylic, capric, lauric, stearic and oleic acids. Lipases from Candida antarctica and Candida rugosa were immobilized onto the carboxylic acid, modified silica nanoparticles and used in the mono and diglycerides production through glycerolysis with or without organic solvents. When lipases immobilized on stearic acid-modified silica nanoparticles, both lipases gave higher activity compared to their corresponding free lipases. Immobilized C. rugosa were stable and reused for 11 cycles without loss in activity. The kinetic parameters, K m and V max of free and immobilized lipases were found using Lineweaver-Burk model. Results indicated that the immobilized lipase had a lower K m and V max when compared with the free lipase.

COD reduction of textile effluent in three-phase fluidized bed bioreactor using Pseudomonas aureofaciens and Escherichia coli.

This paper investigated the effect of mixed cultures of Pseudomonas aureofaciens and Escherichia coli and air as gas on degradation of chemical oxygen demand (COD) in three-phase inverse fluidized beds (TPIFBs) for textile effluents with initial COD of 1200 ppm (effluent 1) and 640 ppm (effluent 2). Investigators focused on the importance of different design of gas spargers of the TPIFB for checking its effect on COD reduction performance. For this purpose, four different gas spargers were fabricated for gas flow entry into bioreactor with different  % open area: Gas sparger 1 (18% open area), sparger 2 (10.42% open area), sparger 3 (8.077% open area) and sparger 4 (1.53% open area). These percentage open area decided the amount of gas flow in a unit time in batch studies, which in turn rely mainly on superficial gas velocity. The reduction in COD was measured at two different superficial gas velocity (0.00343 and 0.004068 m/s) and at two ratio of static bed height to diameter (H/D) of 0.5 and 0.25 in an aerobic mode. Textile effluent 1 resulted in 98.07% COD reduction with sparger 3 and discharged at 23.14 ppm in 28 h. Textile effluent 2 resulted in 96.5% COD reduction with sparger 2 and discharged at 22.4 ppm in 22 h. The resulting COD values of Effluent 1 and effluent 2 were in range of discharge limit and resulted at a low gas velocity of 0.00343 m/s and low H/D ratio of 0.25. The gas holdup correlation was found to be ε g = 0.0064 U g0.98 .

Phyto-synthesis and structural characterization of catalytically active gold nanoparticles biosynthesized using Delonix regia leaf extract.

Biological methods of nanoparticles synthesis are ecologically sound and sustainable alternative to the conventional methods. On the basis of aforesaid premise, the present study deals with the optimization and fabrication of gold nanoparticles (Au-NPs) using easily available bio-resource, Delonix regia leaf extract. The use of practically nontoxic natural extracts and water allows the synthesis pathways presented to be considered as ''green'' and so permitting the synthesized Au-NPs to be used in sensitive areas, such as bioremediation. Various characterization techniques are adopted for the evaluation of size, stability, morphology, crystal nature, and purity of nanoparticles. Ultraviolet-visible spectroscopy analysis showed a surface Plasmon resonance peak for prepared Au-NPs at 542 nm, and its absorbance increased with increasing the interaction time. Transmission electron microscopy analysis showed that the particles were spherical and 4-24 nm in size. Energy dispersive X-ray spectroscopy analysis displayed a 2.2 keV peak corresponding to the pure phase gold nanocrystal. X-ray diffraction analysis proved the fabrication of crystalline Au-NPs with face-centered cubic geometry within 10 min. Furthermore, ζ potential (-15 mV) and Fourier transform infrared data suggested the role of polar polyphenolic compounds of leaf extract in fabrication and stabilization process. Biofabricated nanoparticles are demonstrated to have catalytic activity for the reduction of toxic nitro-organic pollutant o-nitroaniline. Therefore, the present study offers a straightforward, cost-efficient, eco-friendly, and sustainable alternative for the fabrication of catalytically active Au-NPs.

Investigation of photo-assisted and crude peroxidase mediated transformations of chlorinated phenols (CPs) from spiked and industrial wastewaters: identification of reaction products.

This work focused on photo-assisted crude peroxidase mediated transformations of chlorinated phenols (CPs) from spiked and industrial wastewaters and the identification of reaction products formed. Garden radish Raphanus sativus was the source of crude peroxidase. No chlorine bearing compounds were detected by gas chromatography-high resolution mass spectrometry analysis. Under identical test conditions, the concentrations of 4-chlorophenol and 2,4-dichlorophenol were demoted to zero from 514 mg/L, 652 mg/L and that of 2,4,6-trichlorophenol and pentachlorophenol were reduced to 18 mg/L and 37 mg/L from 790 mg/L and 1066 mg/L, respectively (high-pressure liquid chromatography analysis). Chloride ion release profiles also showed a progressively increasing trend. A neat chemical oxygen demand removal to the extent of 63-79% was achieved in the case of spiked wastewater sample and to the extent of 77% for industrial wastewaters. A hypothesis reaction scheme was also suggested to comprehend the mechanism of degradation reactions.

Green synthesis and structural characterization of selenium nanoparticles and assessment of their antimicrobial property.

In the present study, selenium nanoparticles were biologically synthesized by non-pathogenic, economic and easy to handle bacterium Ralstonia eutropha. The selenium oxo anion was reduced to selenium nanoparticles in the presence of the bacterium. The bacterium was grown aerobically in the reaction mixture. An extracellular, stable, uniform, spherical selenium nanoparticle was biosynthesized. The TEM analysis revealed that the biosynthesized selenium nanoparticles were spherical in shape with size range of 40-120 nm. XRD and SAED analysis showed that nanocrystalline selenium of pure hexagonal phase was synthesized. The formation of actinomorphic trigonal selenium nanorods was also observed. A mechanism of biosynthesis of selenium nanoparticles by R. eutropha was proposed. The biosynthesized selenium nanoparticles were investigated for their antimicrobial activity against potential pathogens. Selenium nanoparticles showed excellent antimicrobial activity. The 100, 100, 250 and 100 µg/ml selenium nanoparticles were found to inhibit 99 % growth of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Streptococcus pyogenes, respectively. Similarly, the 500 µg/ml of selenium nanoparticles was found to inhibit the growth of pathogenic fungi Aspergillus clavatus. The antimicrobial efficacy of selenium nanoparticle was comparable with commercially available antibiotic drug Ampicillin.

Photolytic degradation of chlorophenols from industrial wastewaters by organic oxidants peroxy acetic acid, para nitro benzoic acid and methyl ethyl ketone peroxide: identification of reaction products.

In this investigation, chlorophenol (CP) containing industrial wastewater was remediated by ultraviolet irradiation in conjunction with organic oxidants, peroxy acetic acid (PAA); para nitro benzoic acid (PNBA); and methyl ethyl ketone peroxide (MEKP). CP mineralization was studied with regard to chemical oxygen demand (COD) and chloride ion release under identical test conditions. COD depletion to the extent of 81% by PAA, 66% by PNBA, and 67% by MEKP was noted along with an upwardly mobile trend of chloride ion release upon irradiation of samples at 254 nm. A 90-99% decrease in CP concentration (as per high pressure liquid chromatography (HPLC) analysis) was achieved with an additional 15.0 ml of organic oxidant in all cases. Gas chromatography high resolution mass spectroscopy (GC-HRMS) results also indicated the formation of such reaction products as are free from chlorine substitutions. This treatment also leads to total decolorization of the collected samples.

Investigation of UV-assisted chlorophenol congeners' degradation by organic oxidant p-nitrobenzoic acid in basic media.

This research specifically addressed the photodegradation of selected model chlorophenol (CP) congeners, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP), by an organic oxidant, p-nitrobenzoic acid (PNBA), in basic media. The reactions were followed by high-pressure liquid chromatography and gas chromatography-mass spectroscopy analysis for residual concentration and the identification of photodegraded products respectively. Initial degradation was confirmed by the formation of ring cleavage compounds, and subsequent mineralization was evidently marked by an increase in release of chloride ions in the time course profile. The presence of fewer/no chlorine atoms in the degraded compounds corroborated the mineralization by UV/PNBA action. The chemical oxygen demand (COD) was also observed to fall appreciably to the extent of 73% during all CP congeners' degradation. The maximum COD decrease was observed in PNBA-assisted 4-CP degradation. The overall degradation kinetics conforming to second-order reaction is observed to follow the order 4-CP > 2,4,6-TCP ∼ PCP ∼ 2,4-DCP. The findings of this investigation elucidated the fact that PNBA was capable of successfully degrading/mineralizing the selected CP congeners.

Photochemical degradation of 4-chlorophenol in the aqueous phase using peroxyacetic acid (PAA).

The photochemical degradation of 4-chlorophenol (4-CP) using ultraviolet irradiation (UV) of 6, 12 and 18 W with peroxyacetic acid (PAA) was studied in a batch reactor. The objective of this work was to investigate degradation and mineralization of 4-CP by PAA. The degradation efficiency increased with increasing UV input. The degradation process was also pH and initial PAA concentration dependent. The optimum conditions for the photochemical degradation of 4-CP as UV input, pH and PAA concentration was found to be 18 W, 9.5 and 3,040 ppm. The reaction efficiency decreased with increasing initial 4-CP concentrations. More than 95% mineralization of 4-CP was achieved with the UV/PAA process. The chloride ion concentration and chemical oxygen demand (COD) was evaluated. The chloride ion concentration and COD were decreased gradually with increasing UV input. Samples were analyzed by high pressure liquid chromatography (HPLC), UV spectrophotometry and gas chromatography-mass spectrometry (GC-MS) for residual concentration and identification of final degraded products.

Overview of fungal lipase: a review.

Lipases (triacylglycerolacyl hydrolases, EC3.1.1.3) are class of enzymes which catalyze the hydrolysis of long-chain triglycerides. In this review paper, an overview regarding the fungal lipase production, purification, and application is discussed. The review describes various industrial applications of lipase in pulp and paper, food, detergent, and textile industries. Some important lipase-producing fungal genera include Aspergillus, Penicillium, Rhizopus, Candida, etc. Current fermentation process techniques such as batch, fed-batch, and continuous mode of lipase production in submerged and solid-state fermentations are discussed in details. The purification of lipase by hydrophobic interaction chromatography is also discussed. The development of mathematical models applied to lipase production is discussed with special emphasis on lipase engineering.

Kinetic modeling for the biosorption of copper by pretreated Aspergillus niger biomass.

In this present work, a kinetic model for biosorption of copper was developed considering the possibility of different forms of functional groups being present on the surface of the biomass prepared from Aspergillus niger. Results showed that metal uptake by A. niger was a mass transfer driven process, requiring only 30min to achieve 70% adsorption efficiency. Copper sorption by A. niger was influenced by the biomass dose, initial metal ion concentration, and pH of the solution. The Langmuir and Freundlich adsorption isotherms were used to describe the behavior of the system at different pH. The retention capacity of the biomass was determined at pH 6.0 to be equal to 23.62mg/g of biomass. The pretreatment with formalin improved the uptake of metal ion.