Reaction Conditions pH Research Articles

Novel synthesis of CuFe2O4/g-C3N4 based on microwave ferromagnetic resonance effect for the thorough removal of TC in mariculture wastewater under natural sunlight

Superior separation of photogenerated carriers holds the key to intensive degradation of tetracycline (TC) in mariculture wastewater under natural sunlight. CuFe2O4/g-C3N4 (CFO/g) was synthesized by secondary microwave co-precipitation (SMCP) based on the ferromagnetic resonance absorption effect. Under the reaction conditions of pH = 6.5, CFO/g = 0.2 g/L, [H2O2] = 1 mM, 99.0 % TC removal was realized in 40 min. Enhanced performance for TC removal in high-salinity environments heavily relied on elevated ionic strength and rapid electron transfer of CFO/g in conjunction with high-salinity interactions. To ecologically remediate mariculture wastewater under natural sunlight, we immobilized powdered CFO/g to a ferrite magnet and devised a continuous flow reaction apparatus, incorporating the controlled injection of hydrogen peroxide (H2O2), to achieve the 100 % TC removal and simultaneously undertake the pretreatment of other contaminants (∼70 %). Ultimately, a safety assessment demonstrated that the degradation of mariculture wastewater by the CFO/g photo-Fenton system is a reliable and efficient technology, and the growth of clownfish remained unimpaired. SMCP successfully accelerated the conversion of high-valent metal ions to low-valent ones and eased the activation barriers of H2O2, enabling various active species to execute their respective roles productively. Innovative application of microwave resonance to enhance the magnetic properties of CFO/g and to support the equilibrium conversion of elemental valence states in high-salinity environments from real wastewater.

Organic Ligand-Mediated Dissolution and Fractionation of Rare-Earth Elements (REEs) from Carbonate and Phosphate Minerals.

Global efforts to build a net-zero economy and the irreplaceable roles of rare-earth elements (REEs) in low-carbon technologies urge the understanding of REE occurrence in natural deposits, discovery of alternative REE resources, and development of green extraction technologies. Advancement in these directions requires comprehensive knowledge on geochemical behaviors of REEs in the presence of naturally prevalent organic ligands, yet much remains unknown about organic ligand-mediated REE mobilization/fractionation and related mechanisms. Herein, we investigated REE mobilization from representative host minerals induced by three representative organic ligands: oxalate, citrate, and the siderophore desferrioxamine B (DFOB). Reaction pH conditions were selected to isolate the ligand-complexation effect versus proton dissolution. The presence of these organic ligands displayed varied impacts, with REE dissolution remarkably enhanced by citrate, mildly promoted by DFOB, and showing divergent effects in the presence of oxalate, depending on the mineral type and reaction pH. Thermodynamic modeling indicates the dominant presence of REE-ligand complexes under studied conditions and suggests ligand-promoted REE dissolution to be the dominant mechanism, consistent with experimental data. In addition, REE dissolution mediated by these ligands exhibited a distinct fractionation toward heavy REE (HREE) enrichment in the solution phase, which can be mainly attributed to the formation of thermodynamically predicted more stable HREE-ligand complexes. The combined thermodynamic modeling and experimental approach provides a framework for the systematic investigation of REE mobilization, distribution, and fractionation in the presence of organic ligands in natural systems and for the design of green extraction technologies.

Engineering gold nanoworms with tunable longitudinal plasmon peak in the near infrared and their refractive index sensing properties.

The plasmonic properties of rod-shaped Au nanoparticles make them promising for numerous applications. The synthesis recipes for Au nanorods are well established and their longitudinal plasmon peak can be tuned over a wide wavelength range. Herein, we demonstrate that the longitudinal plasmon peak of gold NWs (NWs), which are bent nanorods, can be finely tuned in the near-infra-red region. The NWs were synthesized using a one-step reaction method. We have seen that the length and aspect ratio of NWs can be tuned by simply changing the pH of the reaction medium. Under higher pH reaction conditions, NWs with relatively smaller sizes were obtained. Similar to nanorods, NWs have a well-defined longitudinal plasmon peak, which scales linearly with their aspect ratio. Finite element analysis was used to model the optical properties of Au NWs. The simulated results matched well with the experimental spectra. The synthesized NWs have shown good refractive index sensitivities (RIS). The RIS of NWs increased with an increase in their aspect ratio. A maximum sensitivity value of 542 nm per RIU, was obtained for NWs with the plasmon peak at 1033 nm. The RIS values are comparable to that of Au nanorods and bipyramids.

Co-adsorption of tetracycline and copper by the thiourea-modified porous sodium alginate microspheres

The gradual increase of antibiotics and heavy metals in aquatic environments poses a serious threat to human health and ecosystems, and finding effective methods for simultaneous removal of antibiotics and heavy metals has attracted increasing concern. In this study, a novel porous structure of thiourea-modified sodium alginate microspheres (UA-Ca) was synthesized by modification with thiourea, epichlorohydrin, and calcium chloride, and was applied for the simultaneous removal of tetracycline (TC) and Cu(II) from water. The results indicated that the UA-Ca material with 1:2 mass ratio of thiourea and sodium alginate showed the highest removal of TC and Cu(II) under the reaction condition of pH= 7. The removal process of both TC and Cu(II) follows the pseudo-second-order adsorption model and Langmuir isotherm model. UA-Ca had a high adsorption capacity toward TC and Cu(II) with the maximum value of 1.099 mmol/g and 2.793 mmol/g based on the Langmuir model at 298 K, respectively. Thermodynamical parameters revealed that TC and Cu(II) adsorption is spontaneous with endothermic nature. Competing ionic cations (Ca2+、Mg2+、NH4+) and organics (sulfamethoxazole, hygromycin) had a certain inhibitory effect on the removal of TC and Cu(II) by UA-Ca, whereas the anionic ions (CO32-、PO43-、SO42-) all had little effect on its removal. Fourier transform infrared spectra and X-ray photoelectron spectroscopy analyses showed that the removal of TC and Cu(II) by UA-Ca was mainly due to electrostatic adsorption and surface complexation. This work provides a promising UA-Ca material for the effective removal of TC and Cu(II) in contaminated water.

Preparation of β-galacto-oligosaccharides using a novel endo-1,4-β-galactanase from Penicillium oxalicum

Endo-1,4-β-galactanase is an indispensable tool for preparing prebiotic β-galacto-oligosaccharides (β-GOS) from pectic galactan resources. In the present study, a novel endo-1,4-β-galactanase (PoβGal53) belonging to glycoside hydrolase family 53 from Penicillium oxalicum sp. 68 was cloned and expressed in Pichia pastoris GS115. Upon purification by affinity chromatography, recombinant PoβGal53 exhibited a single band on SDS-PAGE with a molecular weight of 45.0 kDa. Using potato galactan as substrate, PoβGal53 showed optimal reaction conditions of pH 4.0, 40 °C, and was thermostable, retaining >80 % activity after incubating below 45 °C for 12 h. Significantly, PoβGal53 exhibited relatively conserved substrate specificity for (1 → 4)-β-D-galactan with an activity of 6244 ± 282 U/mg. In this regard, the enzyme is in effect the most efficient endo-1,4-β-galactanase identified to date. By using PoβGal53, β-GOS monomers were prepared from potato galactan and separated using medium pressure liquid chromatography. HPAEC-PAD, MALDI-TOF-MS and ESI-MS/MS analyses demonstrated that these β-GOS species ranged from 1,4-β-D-galactobiose to 1,4-β-D-galactooctaose (DP 2–8) with high purity. This work provides not only a highly active tool for enzymatic degradation of pectic galactan, but an efficient protocol for preparing β-GOS.

Eco-friendly Synthesis of Silver Nanoparticles using Bignay (Antidesma bunius) Leaves for Antibacterial Application

Background:: Foodborne pathogenic bacteria continue to become a global concern despite the advancements in food packaging technology. Silver nanoparticles (AgNPs) are widely studied in the field as they exhibit desirable inhibitory properties against foodborne pathogens. AgNPs are conventionally synthesized by toxic chemical and physical means; hence, there is a need to seek environmentally safe alternative routes for producing AgNPs. Objective:: The study aimed to synthesize AgNPs using bignay (Antidesma bunius) leaf extract and assess its antimicrobial activity against the common foodborne pathogens S. aureus and E. coli. Methods:: Bignay leaf extract was characterized using total phenolic content (TPC) assay and 2,2- Diphenyl-1-picrylhydrazyl (DPPH) assay. AgNPs were produced under optimized pH, temperature, and incubation time and were characterized using UV-Vis spectroscopy, Fourier Transform Infrared spectroscopy, and Transmission Electron Microscopy. The antimicrobial activity of AgNPs was evaluated against S. aureus and E. coli using the Resazurin Microtiter Assay (REMA). Results:: Bignay leaf extract exhibited a total phenolic content of 0.315 ± 0.015 mg GAE/mg extract and an IC50 of 36.36 ± 0.003 μg/mL, which suggests its good reducing properties. The AgNPs synthesized under reaction conditions of pH 7, 45 ºC, and 30 min showed SPR peaks in the range of 412- 426 nm. Particles were spherical with an average size of 23.72 ± 7.30 nm. FTIR analysis revealed that the phenolic compounds in the extract capped the resulting nanoparticles. AgNPs demonstrated superior inhibitory activity against S. aureus and E. coli with MIC90 values of 2.90 ± 0.03 and 3.08 ± 0.004 μg/mL, respectively. Conclusion:: The study was able to develop a green approach for the synthesis of AgNPs with antibacterial properties using bignay leaf extract.

Effective Removal of Hexavalent Chromium from Aqueous Solutions Using Quaternary Ammonium-Functionalized Magnetic Graphene Oxide Composites

Novel quaternary ammonium/magnetic graphene oxide composites (M-PAS-GO) that efficiently remove Cr(VI) ions were fabricated through the introduction of the (3-aminopropyl) triethoxysilane and Fe3O4 nanoparticles on the surface of GO, and then modified with n-butyl bromide. The fabricated M-PAS-GO was comprehensively characterized by SEM, TEM, EDX, XRD, Raman spectroscopy and FTIR, and the results manifest that the quaternary ammonium group was introduced onto the surface of GO. Under the reaction conditions of pH 3.20, temperature of 25 °C and M-PAS-GO dosage of 0.01 g/50 mL, 90% of 10 mg/L Cr(VI) ions were removed from the solution within 20 min. The kinetics study indicates that the adsorption process followed the pseudo-second-order model and was surface reaction-controlled. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggest that the adsorption process was an exothermic and spontaneous process. The maximum adsorption capacities of Cr(VI) ions on M-PAS-GO composites calculated by the Langmuir model were 46.48 mg/g. Moreover, the reusability and stability of M-PAS-GO demonstrates its economic sustainability. This study suggests that M-PAS-GO is a potential candidate adsorbent for the separation of Cr(VI) from wastewater.

Enhancement of 15% calcium oxide doped nano zero-valent iron on arsenic removal from high-arsenic acid wastewater.

Nano zero-valent iron (nZVI) has a great potential for arsenic removal, but it would form aggregates easily and consume largely by H+ in the strongly acidic solution. In this work, 15%CaO doped with nZVI (15%CaO-nZVI) was successfully synthesized from a simplified ball milling mixture combined with a hydrogen reduction method, which had a high adsorption capacity for As(V) removal from high-arsenic acid wastewater. More than 97% As(V) was removed by 15%CaO-nZVI under the optimum reaction conditions of pH 1.34, initial As(V) concentration 16.21g/L, and molar ratio of Fe/As (nFe/nAs) 2.5:1. The effluent pH solution was weakly acidic 6.72, and the secondary arsenic removal treatment reduced the solid waste and improved arsenic grade in slag from the mass fraction of 20.02% to 29.07%. Multiple mechanisms including Ca2+ enhanced effect, adsorption, reduction, and co-precipitation coexisted for As(V) removal from high-arsenic acid wastewater. Doping of CaO might lead to improving cracking channels which was benefit for electronic transmission and the confusion of atomic distribution. The in situ weak alkaline environment generated on the surface of 15%CaO-nZVI would increase the content of γ-Fe2O3/Fe3O4, which was in favor for As(V) adsorption. In addition, H+ in the strongly acidic solution could accelerate corrosion of 15%CaO-nZVI and abundant fresh and reactive iron oxides continuously generated, which would provide plenty specific reactive site and fast charge transfer and ionic mobility for arsenic removal.

Electron-transfer pathways insights into contaminants oxidized by [tbnd]Cu-OOSO3- intermediate: Effects of oxidation states of Cu and solution pH values

The copper-peroxy complex (Cu-OOSO3-) metastable intermediate has been confirmed to oxidize contaminants via a single-electron-transfer pathway or an oxygen-atom-transfer pathway. And the effects of Cu oxidation states and reaction pH conditions on the intermediate properties have not been explored in depth. Here, copper oxide (CuOx) catalysts with different Cu oxidation states were synthesized by a simple precipitation method by controlling the reaction temperature from 0 to 45 °C. CuOx displayed a strong catalytic dependence on the Cu oxidation state, and CuOx-30 with Cu average valence on the catalyst surface of 1.61 was more reactive for catalytic degradation of bisphenol A with peroxymonosulfate (PMS). Notably, CuOx-30, with the best electron-accepting ability, was easier to bonding with PMS to form the Cu-OOSO3- reactive complex, and the generated intermediate exhibited the strongest capacity to obtain electrons from contaminants. Moreover, the electron-transfer pathways were closely related to the average valence of Cu, and the contribution of the oxygen-atom-transfer pathway changed volcanic with increasing Cu valence. Meanwhile, the reaction predominantly involved the oxygen-atom-transfer pathway under acidic conditions (pH=3), while the contribution of the single-electron-transfer pathway raised with increasing pH values. Hence, this work was devoted to providing new insights into the CuOx-inducing PMS activation and vital supplementary to the properties of the Cu-OOSO3- intermediate.

Integrated Photocatalytic Oxidation and Adsorption Approach for the Robust Treatment of Refinery Wastewater Using Hybrid TiO2/AC

This study reports the removal of hydrocarbon (HC) pollutants from petroleum refinery wastewater by integrated photocatalytic oxidation and adsorption using a TiO2/AC hybrid material. The hybrid adsorbent/catalyst was prepared by the impregnation of TiO2 over AC and characterized by FTIR, SEM, EDX, and XRD analyses. Under the optimized reaction conditions of pH 3, 30 °C, and 1000 mg TiO2/AC per 500 mL of sample in 50 min, the integrated photocatalytic oxidation-adsorption achieved a net percentage removal of benzene, toluene, aniline, and naphthalene of 91% from model HC solutions. Under these conditions, for the treatment of real refinery wastewater, TiO2/AC caused a 95% decrease in chemical oxygen demand (COD). The integrated photocatalytic oxidation and adsorption using TiO2/AC showed a clear advantage over the individual adsorption and photocatalytic oxidation using AC and TiO2, whereby about the same level of removal of model HCs and a decrease in the COD of refinery wastewater was attained in 105 min and 90 min, respectively, utilizing larger adsorbent/catalyst dosages. GC-MS analysis revealed that during the integrated process of adsorption-photocatalytic oxidation, all the parent HCs and oxidation byproducts were completely removed from the refinery wastewater. Based on the outstanding performance, cost-effectiveness, and environmental greenness, the newly designed TiO2/AC via the integrated adsorption-photocatalytic oxidation can be counted as an effective alternative route for the large-scale processing of refinery wastewater.

Visible light photochemical synthesis of ultrasmall palladium/copper bimetallic particles at room temperature and its catalytic application in degradation of p-NP

Pt-based metals are very effective catalysts widely adopted in many fields. But the high cost prevents its further industrial application. One of the effective ways to solve the problem is to replace platinum with relatively cheap palladium and its alloy with copper. However, producing Pd/Cu bimetallic catalysts efficiently and economically with controllable particle size and uniform distribution is still challenging, especially when trying to reduce the consumption of precious metals. In this paper, ultrasmall palladium/copper (Pd/Cu) bimetallic catalysts with even dispersion were prepared on multi-walled carbon nanotubes (MWCNTs) by adding polyethylene glycol 400 (PEG 400) as a reducing agent and stabilizer under visible light irradiation at room temperature. The catalytic performance was studied in the catalysis of p-nitrophenol (p-NP) reduction. Of all the bimetallic catalysts produced in different conditions, the best one was obtained under the reaction condition of pH = 7 and violet light irradiation (wavelength 380–435 nm). The average particle size of 0.85 nm, and the apparent rate constant in the catalysis is 1.47 min−1. This research probes the role of visible light as a key kinetic controlling method in the formation of ultrasmall particles (UPs). It proves the effectiveness of using visible light irradiation as an effective and more “green chemistry” approach to get precious metal UPs as catalysts beyond the traditional ultraviolet or laser photochemistry methods.

Degradation of Antibiotics by Fenton-like Reaction Catalyzed by Iron Oxide

In recent years, antibiotics have been widely used in the treatment of human and animal diseases due to their effectiveness. Most antibiotics enter the environment in the form of primitive or metabolites, making them new environmental pollutants, destroying the ecological environment, and endangering human health. The Fenton method is one of the advanced oxidation technologies including the traditional Fenton method and various Fenton methods. It has a good effect on the degradation of antibiotics in wastewater. Among them, the Fenton-like method has been widely studied by scholars because of its wide pH reaction conditions and better degradation efficiency. This article takes the Fenton-like reaction as the research object to study the catalytic and promotion effect of iron oxide as a catalyst on the degradation of antibiotics in the Fenton-like reaction. The experimental results show that the iron oxide catalytic system is much better than the traditional ferrous ion-catalyzed Fenton system to degrade antibiotics. Under certain experimental conditions, the degradation rate of ofloxacin in the Fe3O4-H2O2 reaction system for 72 hours reached 79.3%.

Structural, and functional properties of phosphorylated pea protein isolate by simplified co-spray drying process

In this work, to improve the functionality of pea protein isolate (PPI), sodium hexametaphosphate (SHMP) was added during last step of protein extraction and co-spray dried. The influence of PPI to SHMP mixing ratios (95:5 and 90:10) and reaction pH conditions (pH 6, 7, 8, and 9) on reaction efficiency, structural and functional properties of phosphorylated PPI were evaluated. Results showed that both mixing ratios had a similar degree of phosphorylation, suggesting the high efficiency of a 95:5 mixing ratio. The mixing ratio affected powder yield and proximate composition whereas hydrophobicity and denaturation temperature were regulated by pH conditions. For functionality, both mixing ratios showed significantly increased solubility at pH 6. Moreover, an increase in foaming capacity was observed in all phosphorylated PPI. The result from the current study may work as a basis for PPI phosphorylation in the food industry using the simplified method.

Carbothermal synthesis of nano-iron-carbon composites for arsenate removal from high-arsenic acid wastewater

The current carbothermal method involves impregnation and reduction of ferric salt with the problems of low product activity and high cost, limiting the large-scale production and application of nano-zero-valent iron (nZVI). In this work, the nano-iron-carbon composites (CB-nZVI) were successfully synthesized at a high efficiency, low consumption and batch production process and showed a rapid and efficient As(V) removal from high-arsenic acid wastewater (pH<2 and As(V)> 5 g/L). More than 99.77% As(V) was removed by CB-nZVI under optimum reaction conditions of pH 1.7, initial As(V) concentration 5 g/L and nZVI dosage 11 g/L at 40 ℃ with approximately 11 mg/L As(V) still remained in the filtrate. A novel continuous two-stage treatment process was proposed with only 0.12 mg/L As(V) remained in the filtrate, which met the demands specified in Emission Standard of Pollutants for the Sulfuric Acid Industry issued by Ministry of Environmental Protection of China (GB26132–2010), and solid wastes were greatly reduced at the same time. The iron species distributed on the CB-nZVI core-shell structure possessed a high chemical reduction potential gradient driving force which resulted in the adsorbed As(V) would further be reduced to As(III) and As(0) and then diffusing across the thin oxide layer, leading to accumulating or immobilizing the arsenic at the CB-nZVI. Moreover, strongly acidic condition and Fe/C micro-electrolysis could accelerate the corrosion of CB-nZVI and generate iron oxides for As(V) adsorption. These results suggested that CB-nZVI has great potential for the disposal of strongly acidic wastewater with high concentration in the smelting industry.

Enhanced 17α-estradiol removal by biosynthesized rGO@Fe NPs using a response surface methodology

Recently, estrogen has attracted widespread concern because it is increasing being detected in wastewater treatment plants. While techniques for estrogen removal have been reported, these have mostly focused on exploring the effect on removal using simple single-factor experiments, rather than applying more complex multifactor mathematical models to wastewater treatment. In this study, reduced graphene oxide-based iron nanoparticles (rGO@Fe NPs) were used for 17α-estradiol (αE2) removal based on adsorption and Fenton oxidation. A response surface methodology, based on a Box-Behnken design, was used to determine the relationships between critical operation factors (pH, temperature, αE2 concentration, rGO@Fe NPs dose and H2O2 concentration) and removal efficiency to establish the optimal conditions for 1 mg L−1 αE2 removal. Under the determined optimal reaction condition of pH 6.0, temperature 40 °C, 0.08 g L−1 rGO@Fe NPs dose and 6 mM H2O2, a maximum removal efficiency of 99.9% was obtained. Subsequently, the presence of co-existing anions (Cl−, SO42− and NO3−) significantly decreased the removal efficiency of αE2. However, αE2 removal from domestic wastewater could be increased by 38.0% when applying RSM results. Moreover, αE2 removal by rGO@Fe NPs remained stable over five reuse cycles indicating that rGO@Fe NPs would be an efficient and practical advanced materials for αE2 removal.

Ti-ATMP catalyzed esterification of levulinic acid to synthesize butyl ester

In the present work, a hybrid catalytic material of the class of tetravalent metal acid (TMA) salts has been synthesized by the sol–gel method, wherein solution of titanium tetrachloride is allowed to react with claw-type organic phosphonic acid, amino tris methylenephosphonic acid (ATMP) under appropriate reaction conditions of pH, temperature, time and ageing period. The resultant hybrid material (Ti-ATMP) was found to possess proton donating behaviour, and hence it was thought of interest to use it as solid acid catalyst to perform catalysed esterification reaction of biomass-derived levulinic acid with n-butanol to synthesize n-butyl levulinate. Various process parameters such as catalyst concentration % (X1), LA:n–butanol molar ratio (X2) and reaction time (min) (X3) were optimized by response surface methodology (RSM), using the Box–Behnken Design (BBD). Analysis of variance was performed in order to check the suitability of the quadratic model. The catalytic reusability study has been performed in order to have an idea about feasibility of its reuse. Ti- ATMP catalyst was found efficient and promising with satisfactory yields and excellent reusability. The results clearly indicate its potentiality as solid acid catalyst to catalyse other organic transformations.

Activation of peroxymonosulfate by CoFeNi layered double hydroxide/graphene oxide (LDH/GO) for the degradation of gatifloxacin

Layered double hydroxide (LDH) was a kind of layer materials with multi-metal elements and good catalytic performance, but the metals can be dissolved during catalysis. Graphene oxide (GO) was a two-dimensional structure with abundant anionic groups with the potential of immobilizing metals. However, LDH combined with GO (LDH/GO) was few reported in the treatment of pharmaceuticals and personal care products (PPCPs). In this work, CoFeNi LDH/GO composites were designed and synthesized for activating peroxymonosulfate (PMS). Meanwhile, gatifloxacin (GAT), a typical antibiotic, was used to assess the performance of LDH/GO + PMS system. The characterization of LDH/GO using various measures showed that the adding GO was inserted the layer structure of LDH and the surface functional group of GO was immobilized in LDH well. GAT could be degraded completely after 45 min under the reaction conditions of pH 7.0, 38 mg L−1 GAT, 40 mg L−1 LDH/GO and 400 mg L−1 PMS. The removal of total organic carbon and defluorination reached 55.5% and 78.0% after 5 h reaction, respectively. Quenching tests suggested that the main radicals responsible for GAT degradation and mineralization was sulfate radical (SO4−). The redox cycle made the catalysis of the LDH/GO composites work continuously. Compared with LDH + PMS system, the concentration of dissolved metals decreased 60.6%-74.3% at pH 3.0–11.0 in LDH/GO + PMS system. The reusability test indicates that LDH/GO has stable catalytic performance in removing PPCPs from wastewater.

Cloning and expression of a novel α-galactosidase from Lactobacillus amylolyticus L6 with hydrolytic and transgalactosyl properties.

Lactobacillus amylolyticus L6, a gram-positive amylolytic bacterium isolated from naturally fermented tofu whey (NFTW), was able to hydrolyze raffinose and stachyose for the production of α-galactosidase. The cell-free extract of L. amylolyticus L6 was found to exhibit glycosyltransferase activity to synthesize α-galacto-oligosaccharides (GOS) with melibiose as substrate. The coding genes of α-galactosidase were identified in the genome of L. amylolyticus L6. The α-galactosidase (AglB) was placed into GH36 family by amino acid sequence alignments with other α-galactosidases from lactobacilli. The optimal reaction conditions of pH and temperature for AglB were pH 6.0 and 37°C, respectively. Besides, potassium ion was found to improve the activity of AglB while divalent mercury ion, copper ion and zinc ion displayed different degrees of inhibition effect. Under the optimum reaction condition, AglB could catalyze the synthesis of GOS with degree of polymerization (DP) ≥5 by using 300 mM melibiose concentration as substrate. The maximum yield of GOS with (DP) ≥3 could reach 31.56% (w/w). Transgalactosyl properties made AglB a potential candidate for application in the production of GOS.

Photocatalytic oxidative degradation of hydrocarbon pollutants in refinery wastewater using TiO2 as catalyst.

This study reports the photocatalytic oxidative degradation of hydrocarbon pollutants present in refinery wastewater under UV light using Fe2 O3 , MnO2 , TiO2 , and ZnO as catalysts. Among the catalysts, TiO2 exhibited the highest photocatalytic degradation activity, that is, 92, 98.8, 91.5, and 93% conversion for benzene, toluene, phenol, and naphthalene, respectively, in the model refinery wastewater under the optimum reaction conditions of pH 3, 30°C, 90-min reaction time, and 100mg/L catalyst dose. The photocatalytic degradation of a real refinery wastewater sample containing 69.23% aliphatics, 25.36% aromatics, 3.2% oxygenates, and 2.21% naphthenic hydrocarbons under the optimum conditions revealed a net decrease in chemical oxygen demand (93.2%), that is, from 970mg/L to 65mg/L. GC-MS analysis of the reaction products confirmed that using UV/TiO2 system, complete photodegradation of the parent hydrocarbons occurred, but some oxygenated byproducts were also observed. This study provides useful reference information for the treatment of wastewater from oil refineries to cope with the increasing environmental issues. PRACTITIONER POINTS: Benzene, toluene, phenol and naphthalene were successfully degraded by UV/TiO2 system, under 30°C, 1hr, pH 3 and 100mg catalyst. Photocatalytic oxidation of Refinery wastewater (Attock Oil refinery, Pakistan), UV/ TiO2 system resulted in 93.92% COD removal. GC-MS analysis shows complete removal of parent hydrocarbons from refinery wastewater, leaving only traces of oxygenated hydrocarbons as oxidation byproducts.

Production of 7,10,12-trihydroxy-8(E)-octadecenoic acid from ricinoleic acid by Pseudomonas aeruginosa KNU-2B.

Microbial production of hydroxy fatty acids (HFAs) was widely studied because of important biological properties of HFAs. Among microorganisms producing HFAs, Pseudomonas aeruginosa PR3 was well known to produce various HFAs from different unsaturated fatty acids. Recently, a new variant species of P. aeruginosa PR3 was isolated and characterized, showing improved efficiency for producing 7,10-dihydroxy-8(E)-octadecenoic acid from oleic acid. In this study, we report the production of 7,10,12-trihydroxy-8(E)-octadecenoic acid (TOD) from ricinoleic acid by the newly isolated P. aeruginosa KNU-2B. TOD was efficiently produced from ricinoleic acid by KNU-2B with the maximum conversion yield of 56.7% under the optimum reaction conditions of pH 8.0 and 48-h incubation at 27°C, 150rpm. Under optimized reaction conditions, maximum TOD production reached 340.3mg/100mL of the culture. However, requirement of nutritional factors by KNU-2B for production of TOD were considerably different from those by PR3 strain.