Influence of ultrasonication and Fenton oxidation pre-treatment on rheological characteristics of wastewater sludge

The effect of ultrasonication and Fenton oxidation as physico-chemical pre-treatment processes on the change of rheology of wastewater sludge was investigated in this study. Pre-treated and raw sludges displayed non-Newtonian rheological behaviour with shear thinning as well as thixotropic properties for total solids ranging from 10 g/L to 40 g/L. The rheological models, namely, Bingham plastic, Casson law, NCA/CMA Casson, IPC Paste, and power law were also studied to characterize flow of raw and pre-treated sludges. Among all rheological models, the power law was more prominent in describing the rheology of the sludges. Pre-treatment processes resulted in a decrease in pseudoplasticity of sludge due to the decrease in consistency index K varying from 42.4 to 1188, 25.6 to 620.4 and 52.5 to 317.9; and increase in flow behaviour index n changing from 0.5 to 0.35, 0.62 to 0.55 and 0.63 to 0.58, for RS, UlS and FS, respectively at solids concentration 10–40 g/L. The correlation between improvement of biodegradability and dewaterability, decrease in viscosity, and change in particle size as a function of sludge pre-treatment process was also investigated. Fenton oxidation facilitated sludge filterability resulting in capillary suction time values which were approximately 50% of the raw sludges, whereas ultrasonication with high input energy deteriorated the filterability. Biodegradability was also enhanced by the pre-treatment processes and the maximum value was obtained (64%, 77% and 73% for raw, ultrasonicated and Fenton oxidized sludges, respectively) at total solids concentration of 25 g/L. Hence, pre-treatment of wastewater sludge modified the rheological properties so that: (1) the flowability of sludge was improved for transport through the treatment train (via pipes and pumps); (2) the dewaterability of wastewater sludge was enhanced for eventual disposal and; (3) the assimilation of nutrients by microorganisms for further value-addition was increased.     

Concomitant degradation of bisphenol A during ultrasonication and Fenton oxidation and production of biofertilizer from wastewater sludge

Degradation of bisphenol A (BPA), an endocrine disruptor, from wastewater sludge (WWS) has attracted great interest recently. In the present study, the effects of different pre-treatment methods, including ultrasonication (US), Fenton's oxidation (FO) and ferro-sonication (FS) was assessed in terms of increase in solubilization of WWS and simultaneous degradation of BPA. Among US, FO and FS pre-treatment, higher suspended solids (SS), volatile suspended solids (VSS), chemical oxygen demand (COD) and soluble organic carbon (SOC) solubilization (39.7%, 51.2%, 64.5% and 17.6%, respectively) was observed during a ferro-sonication pre-treatment process carried out for 180 min, resulting in higher degradation of BPA (82.7%). In addition, the effect of rheological parameters (viscosity and particle size) and zeta potential on the degradation of BPA in raw and different pre-treated sludges were also investigated. The results showed that a decrease in viscosity and particle size and an increase in zeta potential resulted in higher degradation of BPA. BPA degradation by laccases produced by Sinorhizobium meliloti in raw and pre-treated sludge was also determined. Higher activity of laccases (207.9 U L(-1)) was observed in ferro-sonicated pre-treated sludge (180 min ultrasonic time), resulting in higher removal of BPA (0.083 μg g(-1)), suggesting concomitant biological degradation of BPA.     

The oxidation of fullerene [C70] with various oxidants by ultrasonication

The reaction of C₇₀ by ultrasonication with various oxidants such as 3-chloroperoxy benzoic acid (Fluka 99%), 4-methyl morpholine N-oxide (Aldrich 97%), chromium (VI) oxide (Aldrich 99.9%), and oxone^® monopersulfate compound, at room temperature causes the oxidation of fullerene [C₇₀(O)_n] (n=1–2 or n=1). The FAB-MS, UV–visible, FT-IR spectra, and HPLC analysis confirmed that products of fullerene oxidation are [C₇₀(O)_n] (n=1–2 or n=1).     

The oxidation of fullerene [C70] with various oxidants by ultrasonication

The reaction of C₇₀ by ultrasonication with various oxidants such as 3-chloroperoxy benzoic acid (Fluka 99%), 4-methyl morpholine N-oxide (Aldrich 97%), chromium (VI) oxide (Aldrich 99.9%), and oxone^® monopersulfate compound, at room temperature causes the oxidation of fullerene [C₇₀(O)_n] (n=1–2 or n=1). The FAB-MS, UV–visible, FT-IR spectra, and HPLC analysis confirmed that products of fullerene oxidation are [C₇₀(O)_n] (n=1–2 or n=1).     

Preparation of fenofibrate nanoparticles by combined stirred media milling and ultrasonication method

The production of fenofibrate nanoparticles combining stirred media milling and ultrasonication method was investigated in the current work. The fenofibrate drug sample was first wet milled in stirred media mill for different times and subsequently processed by ultrasonication. The effects of ultrasonication time, power on final product particle sizes were studied. The pre milling by stirred media milling was resulted into reduction of comminution resistance of material. Subsequent treatment by ultrasonication produced smaller particles than obtained by stirred media milling alone. The resulting nanoparticles were found to exhibit excellent stability as investigated by particle size, zeta potential, and multiple light scattering measurement techniques. Further, qualities of nanoparticles obtained by combined approach were characterized by TEM and XRD analysis.     

Optimizing the synergistic effect of sodium hydroxide/ultrasound pre-treatment of sludge

Ultrasound (ULS), sodium hydroxide (NaOH) and combined ultrasound/NaOH pre-treatment were applied to pre-treat waste activated sludge and improve the subsequent anaerobic digestion. Synergistic effect was observed when NaOH treatment was coupled with ultrasound treatment. The highest synergistic Chemical Oxygen Demand (COD) solubilization was observed when 0.02M NaOH was combined with five minutes ultrasonication: an extra 3000 mg/L was achieved on top of the NaOH (1975 mg/L) and ultrasonication (2900 mg/L) treatment alone. Further increase of NaOH dosage increased Soluble Chemical Oxygen Demand (SCOD), but did not increase the synergistic effect. Nine and 18 minutes ultrasonication led to 20% and 24% increase of methane production, respectively; Whereas, 0.05M NaOH pre-treatment did not improve the sludge biodegradability. Combined ultrasound/NaOH (9 min+0.05 M) showed 31% increase of methane production. A stepwise NaOH addition/ultrasound pre-treatment (0.02M+ULS for 5 min+0.02M+ULS for 4 min) was tested and resulted in 40% increase of methane production using 20% less chemicals.     

Electrochemical synthesis of microporous polyaniline films using foam templates prepared by ultrasonication

We report a new soft template method for the synthesis of unique polyaniline (PANI) films with microporous structures. In this process, ultrasonication is used to foam an electrolyte solution containing a surfactant, which is subsequently employed as a soft template for PANI growth via the electrochemical polymerization of aniline. Analysis by scanning electron microscopy demonstrates that the resulting PANI films contain numerous micropores. These microporous PANI films exhibit faster charging (doping) and discharging (dedoping) current responses compared to ordinary flat films of the same material.     

Development of sheared and ultra-pure DNA thin films prepared by ultrasonication and purification

DNA solutions were prepared by ultrasonication and purification to compare the characteristics between DNA solutions different in size, purity, or both. Ultrasonication effectively minimized the size variation in native DNA, while purification enhanced the transparency of fabricated DNA thin film. Each DNA solution was used to fabricate water-soluble or organic-soluble thin film. According to the electrical measurement of DNA and CTMA-modified DNA thin films and the fluorescence measurement of PicoGreen-embedded DNA thin films, ultrasonication and purification affect the electrical characteristics and intercalating efficiency of DNA thin films. The electrical properties of the water-soluble thin film and the organic-dissolved thin film were predominantly affected by purification, but opposite tendencies were observed. The highest resistance was observed in water-soluble DNA thin film fabricated from ultra-pure DNA, whereas organic-soluble DNA thin film from ultra-pure DNA showed the lowest resistance. Ultrasonication showed a synergistic effect on PicoGreen-DNA insertion, whereas purification suppressed the fluorescence signal.     

Leaching of polycyclic aromatic hydrocarbons (PAHs) from industrial wastewater sludge by ultrasonic treatment

Ultrasonic treatment for sludge reduction in wastewater treatment plants (WWTPs) can substantially affect the fate of trace pollutants. However, their fates in the different phases of sludge and mass balances have rarely been reported. In this study, wastewater sludge samples were ultrasonicated at 600 W for 0–30 min. Then, the leaching of the 16 priority polycyclic aromatic hydrocarbons (PAHs) from the sludge solids (sediment) to the liquid phase (supernatant) was investigated. The total concentration of PAHs (∑₁₆ PAHs) in the sludge sediment (2.10 μg/g) was comparable with those of previous worldwide studies. Among the 16 PAHs, naphthalene and acenaphthylene were dominant. The total concentrations of PAHs in the supernatant generally increased with sonication time, indicating that PAHs associated with sludge materials, such as microorganisms, were released into the supernatant. Lighter and more water soluble PAHs were released preferentially into the supernatant in dissolved form, whereas heavier and more hydrophobic PAHs were strongly bound to particles. According to mass balance calculations, 21% of the PAHs in the sludge sediment moved to the supernatant without discernible sonodegradation. An additional experiment for degradation of PAHs supported this interpretation, and several reasons for the no significant sonodegradation were discussed. This result suggests that leaching trace pollutants may significantly contaminate the sludge filtrate after ultrasonic treatment, and therefore their fates should be investigated.     

Studies to control biofilm formation by coupling ultrasonication of natural waters and anodization of titanium

The main objective of this study was to investigate the combined effect of ultrasonication of natural waters and anodization of titanium on microbial density and biofilm formation tendency on titanium surfaces. Application of 24 kHz, 400 W high power ultrasound through a 14 mm horn type SS (stainless steel) Sonicator with medium amplitude of 60% for 30 min brought about three order decrease in total bacterial density of laboratory tap water, cooling tower water and reservoir water and two order decrease in seawater. Studies on the effect of ultrasonication on dilute pure cultures of Gram-negative and Gram-positive bacteria showed five order and three order decrease for Pseudomonas sp. and Flavobacterium sp. respectively and two order and less than one order decrease for Bacillus sp. and Micrococcus sp. respectively. Ultrasonication increased lag phase and reduced logarithmic population increase and specific growth rate of Gram-negative bacteria whereas for Gram-positive bacteria specific growth rate increased. Studies on the biofilm formation tendency of these ultrasonicated mediums on titanium surface showed one order reduction under all conditions. Detailed biofilm imaging by advanced microscopic techniques like AFM, SEM and epifluorescence microscopy clearly visualized the lysed/damaged cells and membrane perforations due to ultrasonication. Combination of ultrasonication and anodization brought about maximum decrease in bacterial density and biofilm formation with greater than two order decrease in seawater, two order decrease in Bacillus sp. culture and more than four order decrease in Flavobacterium sp. culture establishing the synergistic effect of anodization and ultrasonication in this study.     

Evaluation of a biological wastewater treatment system combining an OSA process with ultrasound for sludge reduction

Sludge production is an undesirable by-product of biological wastewater treatment. The oxic-settling-anaerobic (OSA) process constitutes one of the most promising techniques for reducing the sludge produced at the treatment plant without negative consequences for its overall performance. In the present study, the OSA process is applied in combination with ultrasound treatment, a lysis technique, in a lab-scale wastewater treatment plant to assess whether sludge reduction is enhanced as a result of mechanical treatment. Reported sludge reductions of 45.72% and 78.56% were obtained for the two regimes of combined treatment tested in this study during two respective stages: UO1 and UO2. During the UO1 stage, the general performance and nutrient removal improved, obtaining 47.28% TN removal versus 21.95% in the conventional stage. However, the performance of the system was seriously damaged during the UO2 stage. Increases in dehydrogenase and protease activities were observed during both stages. The advantages of the combined process are not necessarily economic, but operational, as US treatment acts as contributing factor in the OSA process, inducing mechanisms that lead to sludge reduction in the OSA process and improving performance parameters.     

Facile preparation of superhydrophobic copper surface by HNO3 etching technique with the assistance of CTAB and ultrasonication

Superhydrophobic rough structure was prepared on copper wafer via HNO₃ etching technique with the assistance of Cetyltrimethyl Ammonium Bromide (CTAB) and ultrasonication. After modification of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTES), the copper wafer showed stable superhydrophobicity. The morphologies, chemical compositions and hydrophobicity of the substrates were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. Dense and spherical micropits appeared on copper wafer after it was etched by 5 M nitric acid with 1.2 mM CTAB under ultrasonication for 20 min. The SEM results indicated that the joint action of CTAB and ultrasonication caused the formation of dense and spherical micropits.     

Effect of ultrasonication time on microstructure,thermal conductivity,and viscosity of ionanofluids with originally ultra-long multi-walled carbon nanotubes

The stability along with thermal and rheological characteristics of ionanofluids (INFs) profoundly depend on the protocol of preparation. Therefore, in this work, the effect of ultrasonication time on microstructure, thermal conductivity, and viscosity of INFs containing 0.2 wt% of originally ultra-long multi-walled carbon nanotubes (MWCNTs) and four different ILs, namely 1-propyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium thiocyanate, or 1-ethyl-3-methylimidazolium tricyanomethanide, was studied. The INFs were obtained by a two-step method using an ultrasonic probe. The ultrasonication process was performed for 1, 3, 10, or 30 min at a constant nominal power value of 200 W. The obtained results showed that for the shortest sonication time, the highest thermal conductivity enhancement of 12% was obtained. The extended sonication time from 1 to 30 min caused the cutting of MWCNTs and breaking the nanoparticle clusters, leading to a decrease in the average length of the nanotube bundles by approx. 70%. This resulted in a decline in thermal conductivity even by 7.2% and small deviations from the Newtonian behavior of INFs.     

Degradation of azo dye Acid black 1 using low concentration iron of Fenton process facilitated by ultrasonic irradiation

A combination of ultrasonic and low concentration iron (<3 mgL(-1)) of Fenton process (US/Fenton) has been used to treat wastewater containing Acid black 1 (AB1). The results show that the oxidation power of low concentration iron of Fenton could be significantly enhanced by ultrasonic irradiation. The degradation of AB1 in aqueous solution by US/Fenton can receive better results compared with either Fenton oxidation or ultrasonic alone. Many operational parameters, such as ultrasonic power density, the pH value, the Fe(2+) dosage, the H(2)O(2) dosage, AB1 concentration and the temperature, affecting the degradation efficiency were investigated. Also, the effects of various inorganic anions (such as Cl(-), NO(3)(-), CO(3)(2-), etc.) on the oxidation efficiency of US/Fenton were studied. Under the given test conditions, 98.83% degradation efficiency was achieved after 30 min reaction by US/Fenton. The effect of various inorganic anions was in the following decreasing order: SO(3)(2-)>CH(3)COO(-)>Cl(-)>CO(3)(2-)>HCO(3)(-)>SO(4)(2-)>NO(3)(-). The results show that the US/Fenton can be an effective technology for the treatment of organic dyes in wastewater.     

A novel ultrasonication method in the preparation of zirconium impregnated cellulose for effective fluoride adsorption

In the present work, we propose for the first time a novel ultrasound assisted methodology involving the impregnation of zirconium in a cellulose matrix. Fluoride from aqueous solution interacts with the cellulose hydroxyl groups and the cationic zirconium hydroxide. Ultrasonication ensures a green and quick alternative to the conventional time intensive method of preparation. The effectiveness of this process was confirmed by comprehensive characterization of zirconium impregnated cellulose (ZrIC) adsorbent using Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD) studies. The study of various adsorption isotherm models, kinetics and thermodynamics of the interaction validated the method.     

Fish oil based vitamin D nanoencapsulation by ultrasonication and bioaccessibility analysis in simulated gastro-intestinal tract

Recently, nanoemulsions have been employed for different applications including food and drug industries for efficient nutrient delivery system. In this study, vitamin D (a lipophilic molecule) was encapsulated in fish oil for higher oral bioavailability. The oil-in-water nanoemulsion was formulated by ultrasonication technique with a droplet size range of 300–450 nm and a shelf life of more than 90 days. The influence of oil, water and surfactant concentration was investigated by phase diagram. The formulated nanoemulsion had encapsulation efficiency in the range of 95.7–98.2%. Further, nanoemulsion passed through simulated gastro-intestinal tract revealed an increased bioavailability than non-encapsulated vitamin. Thus, the formulation can be used as a drug delivery vehicle for various lipophilic compounds. Till date, no one have fabricated an efficient nano-vehicle for the delivery of vitamin D as well as analyzed the efficient delivery system in simulated GI-tract, this is first of its kind study in this regard. This can be scaled up further after analyzing the safety aspects.     

Preparation and characterization of waxy maize starch nanoparticles via hydrochloric acid vapor hydrolysis combined with ultrasonication treatment

The objective of this work was to develop a simple and efficient method to prepare waxy maize starch nanoparticles (SNPs) by hydrochloric acid (HCl) vapor hydrolysis combined with ultrasonication treatment. The size, morphology, thermal property, and crystal structure of the SNPs were systematically studied. HCl treatment introduces a smaller particle diameter of starch particles from 13.73 ± 0.93 μm to 1.52 ± 0.01–8.32 ± 0.63 μm. Further ultrasonication treatment formed SNPs that displayed desirable uniformity and near-perfect spherical and ellipsoidal shapes with a diameter of 150.65 ± 1.91–292.85 ± 0.07 nm. The highest yield of SNPs was 80.5%. Compared with the native starch, the gelatinization enthalpy changes of SNPs significantly decreased from 14.65 ± 1.58 J/g to 7.40 ± 1.27 J/g. Interestingly, the SNPs showed a wider melting temperature range of 22.77 ± 2.35 °C than native starch (10.94 ± 0.87 °C). The relative crystallinity of SNPs decreased to 29.65%, while long-time ultrasonication resulted in amorphization. HCl vapor hydrolysis combined with ultrasonication treatment can be an affordable and accessible method for the efficient large-scale production of SNPs. The SNPs developed by this method will have potential applications in the food, materials, and medicine industries.     

TiO2 treatment using ultrasonication for bubble cavitation generation and efficiency assessment of a dye-sensitized solar cell

In this study, the impacts of different ultrasonic treatments on TiO₂ particles were determined and they were used to manufacture the photoelectrodes of a dye-sensitized solar cell (DSSC). Two methods were used to prepare TiO₂ particles directly sonicated by an ultrasonic horn, and TiO₂ treated indirectly by an ultrasonic cleaner. TEM, XPS analysis was confirmed that cavitation bubbles generated during ultrasonication resulted in defects on the surface of TiO₂ particles, and the defect induced surface activation. To understand the effect of TiO₂ surface activation on energy conversion efficiency of DSSC, ultrasonic horn DSSC and ultrasonic cleaner DSSC were prepared. The UV–vis analysis exhibited that the ultrasonic horn DSSC possessed higher dye adsorption when compared to the ultrasonic cleaner DSSC, and the EIS analysis confirmed that the electron mobility was greatly increased in the ultrasonic horn DSSC. The energy conversion efficiency of the ultrasonic horn DSSC was measured to be 3.35%, which is about 45% increase in comparison to that of the non-ultrasonic treated DSSC (2.35%). In addition to this regard, recombination resistance of ultrasonic horn DSSC was calculated to be 450 Ω·cm², increasing more than two times compared to the non-ultrasonic treated DSSC (200 Ω·cm²). Taken together, these ultrasonic treatments significantly improved the energy conversion efficiency of DSSC, which was not tried in DSSC-related research, and might lead us to develop more efficient practical route in the manufacturing of DSSC.     

Impact of ultrasonication on the aggregation structure and physicochemical characteristics of sweet potato starch

In order to understand the relationship between the aggregation structure and physicochemical characteristics of ultrasonicated sweet potato starches, sweet potato starch modified with different sonication time (15, 20, 25 and 30 min) was studied in this work for developing starch-based ingredients with tailored functionality. SEM, XRD, FTIR, Raman and DSC measurements were conducted to investigate the transformations of morphological features, crystalline structure, short-range ordered structure and ordered molecular structure of starch granules. Not only could pores and cracks be observed at the surface of starch, but also the structural disorganizations were more evidently induced with the treatment time increasing, especially for the degrees of crystallinity, short-range molecular orders and ordered molecular structures. And these disordering in the aggregation structure not only increased the swelling power and solubility but also declined the pasting temperature, peak viscosity, final and breakdown viscosity of gelatinized starch. In addition, the strengthened retrogradation and gel structures formed by the rearrangement and entanglement of starch polymer chains also demonstrated the structural disorganizations of starch granules during ultrasonic treatment. Therefore, the results of this study may provide further insight in understanding the structural basis of starch physicochemical properties.     

光助Fenton法降解水中间氨基苯酚的研究

采用光助Fenton氧化法处理间氨基苯酚模拟废水,考察了光强、Fenton试剂的用量、初始pH、反应时间对降解效果的影响,初步探讨了其降解动力学规律。结果表明:在不同光源下(闭光、高压汞灯照射以及较强太阳光照射),450W高压汞灯照射以及较强太阳光照射的条件均可以明显加快Fenton法催化氧化降解间氨基苯酚溶液的过程。选择1.5mL2.5g.L-1FeSO4.7H2O,1.0mL6%H2O2,初始pH=3.5,太阳光照射下降解间氨基苯酚效果较好,反应40min后降解率高达99%;降解过程符合准一级反应动力学方程。