Ultrasonic-assisted eggshell extract-mediated polymorphic transformation of calcium carbonate

This study aimed to evaluate the combined effects of eggshell extract and ultrasonic irradiation on the polymorphic transformation of calcium carbonate (CaCO₃). In this context, XRD, Raman spectroscopy, SEM, AFM, TGA-FTIR, BET, and zeta potential analysis were used to identify and characterize the different polymorphs of CaCO₃ obtained in the absence and presence of eggshell extract in the media with and without ultrasonic irradiation. The morphology and polymorphic nature of the CaCO₃ crystals were observed to change, which indicated that the eggshell extract and ultrasonication influenced the structure and crystallization of CaCO₃. The structural analysis results indicated that the addition of eggshell extract to the media resulted in the full transformation of calcite to the vaterite polymorph. The results also showed that ultrasonic irradiation had a more significant influence on the BET specific surface area of the crystals compared to the eggshell extract media. Furthermore, a Box–Behnken design with response surface methodology was employed to determine the optimal operating conditions for CaCO₃ crystallization. The effects of stirring rate, extract concentration, and ultrasonic power on the BET surface area were investigated. The results show that the data sufficiently fit the second-order polynomial model. Understanding the eggshell extract-mediated polymorphic transformation with ultrasonic irradiation obtained in this study makes it possible to control the polymorphic formation and modify the product characteristics.     

Ultrasonic-assisted production of precipitated calcium carbonate particles from desulfurization gypsum

This study aimed to investigate the effect of ultrasonic application on the production of precipitated calcium carbonate (PCC) particles from desulfurization gypsum via direct mineral carbonation method using conventional and venturi tube reactors in the presence of different alkali sources (NaOH, KOH and NH₄OH). The venturi tube was designed to determine the effect of ultrasonication on PCC production. Ultrasonic application was performed three times (before, during, and after PCC production) to evaluate its exact effect on the properties of the PCC particles. Scanning electron microscope (SEM), X-ray diffraction (XRD), Atomic force microscope (AFM), specific surface area (SSA), Fourier transform infrared spectrometry (FTIR), and particle size analyses were performed. Results revealed the strong influence of the reactor types on the nucleation rate of PCC particles. The presence of Na⁺ or K⁺ ions in the production resulted in producing PCC particles containing only calcite crystals, while a mixture of vaterite and calcite crystals was observed if NH₄⁺ ions were present. The use of ultrasonic power during PCC production resulted in producing cubic calcite rather than vaterite crystals in the presence of all ions. It was determined that ultrasonic power should be conducted in the venturi tube before PCC production to obtain PCC particles with superior properties (uniform particle size, nanosized crystals, and high SSA value). The resulting PCC particles in this study can be suitably used in paint, paper, and plastic industries according to the ASTM standards.     

Precipitation of calcium carbonate by ultrasonic irradiation

Supersaturated solution of calcium carbonate ([Ca²⁺]=1.2 mmol/L, [HCO₃⁻]=3.2 mmol/L, pH=8.8, T=30±0.5 °C), a scale forming component, was irradiated by an ultrasonic homogenizer (24 kHz, 15–250 W/cm²) to study the factors that affect its precipitation rate. The factors of (1) depth of horn immersion, (2) ultrasonic intensity and horn tip size and (3) cavitation, which can affect the precipitation rate were investigated in this study. Ultrasonic irradiation was observed to accelerate the precipitation of calcium carbonate and it was found that there exists an optimum range of horn immersion depth for maximizing the precipitation rate. The experimental data also established that the precipitation rate was proportional to ultrasonic intensity and diameter of horn tip. These findings were correlated to the effects of physical mixing, that arises due to ultrasonic irradiation. However, the effect of cavitation in accelerating the precipitation rate was found to be small. Thus it is forwarded that the physical mixing effect, especially macrostreaming is the main factor that accelerates the precipitation rate of calcium carbonate during ultrasonic treatment. Further, neither the morphology nor the size of the calcium carbonate crystals formed were found to be affected by the ultrasonic irradiation.     

Fabrication of bacterial cellulose thin films self-assembled from sonochemically prepared nanofibrils and its characterization

Bacterial cellulose (BC) film formation could be a critical issue in nanotechnology applications such as biomedical or smart materials products. In this research, purified pretreated BC was subjected to high intensity ultrasound (HIUS) and was investigated for the development of BC films. The morphological, structural and thermal properties of the obtained films were studied by using FE-SEM, AFM, FT-IR, XRD, TGA and DSC characterizations. Results showed that the most favorable purification treatment was the 0.01 M NaOH at 70 °C for 2 h under continuous stirring. The most suitable ultrasound operating conditions were found to be, 1 cm distance of ultrasonic probe from the bottom of the beaker, submerged in cold water bath cooling around 12 ± 2 °C. The power (25 W/cm²), time (30 min), BC concentration (0.1% w/w), amplitude (20 μm) and frequency (20 kHz) were maintained constant.     

Polymerization of aniline on bacterial cellulose and characterization of bacterial cellulose/polyaniline nanocomposite films

Bacterial cellulose/polyaniline nanocomposite film was prepared by the chemical oxidative polymerization of aniline with bacterial cellulose. Polyaniline conducting polymer nanocomposite films with bacterial cellulose fibers was prepared and characterized. In nanocomposite film, the bacterial cellulose was fully encapsulated with polyaniline by direct polymerization of the respective monomers using the oxidant and dopant. These bacterial cellulose/polyaniline nanocomposite films materials exhibited the inherent properties of both components. The deposition of a polyaniline on the bacterial cellulose surface was characterized by SEM. XPS revealed a higher doping level of the nanocomposite films doped with p-TSA dopant. From the cyclic voltammetry results, the polyaniline polymer was thermodynamically stable because redox peaks of electrochemical transitions in the voltagrams were maintained in bacterial cellulose/polyaniline nanocomposite films.     

Ultrasonic modification of carbonate scale electrochemically deposited in tap water

Influence of the ultrasound intensity (28 kHz, 1.1–7.5 W/cm²) on CaCO₃ nucleation-growth on the surface of a cylinder mild steel electrode rotating at 500 rpm was studied in tap water. The deposition kinetics was analyzed by chronoamperometry; the calcareous layer was characterized by gravimetry, scanning electron microscopy and XRD. Application of ultrasound to calcium carbonate crystallization affects nucleation site density, mass-transport rate and cavitation erosion of the deposits. Lower intensity ultrasound reduces scale porosity and area density by increasing nucleation site density and accelerating the mass transport. Higher intensity ultrasound promotes cavitation erosion of the formed layer, thus cleaning the surface from the scale. A scale layer with the highest blocking properties formed under applied ultrasound intensity of 1.9 W/cm². The ultrasound doubled crystallization rate, reduced the scale porosity 5 times and halved its area density compared to non-sonicated conditions. Ultrasound of controllable intensity can solve both scale and corrosion problems of industrial heat-exchange equipment by forming a protective scale layer and removing excessive deposits.     

土壤碳酸钙中红外光声光谱特征及其应用

测定并分析了碳酸钙(CaCO3)的中红外光声光谱及光谱特征,利用中红外光声光谱并结合主成分回归(PCR)、偏最小二乘回归(PLSR)和人工神经网络(GRNN)三种分析方法建立回归模型,分析了土壤CaCO3的含量。结果表明CaCO3具有丰富的中红外吸收,最强吸收峰波数在1 450cm-1,且干扰少,可以作为土壤CaCO3的特征吸收峰;三种回归建模方法所建模型线性都很好,PLSR和GRNN最好,相关系数(R2)均大于0.9,PCR次之,为0.847;验证样本预测能力PLSR和PCR最佳,R2大于0.9;GRNN次之,为0.882。偏最小二乘回归在校正和预测过程中的结果都非常好,RPD值均大于3.0,具有较强的适用性。     

Investigation on NIR, coating mechanism of PS-b-PAA coated calcium carbonate particulate

Particulate calcium carbonate is treated by polystyrene (PS)/polyacrylic acid (PAA) block copolymer with varied amount. Coating efficiency is obtained by measuring the dissolve curve. The results of near-infrared (NIR) analysis reveal the thickness and structural information of the surface polymer layer. The alignment of PS-b-PAA chain on and the interaction of carboxyl with the calcite surface are deduced on the basis of X-ray photoelectron spectroscopy (XPS) results.     

Polymer surface modification and characterization of particulate calcium carbonate fillers

The efficacy of the surface treatment of particulate fillers depends on the chemical character of the components, on the method and conditions of the treatment, and on the amount of the treating agent. Here, the ultra-fine calcium carbonate is surface treated with 1, 2, 3 and 4 wt.% polyacrylic acid (PAA) synthesized by ourselves, which has strong ionic interaction and is an efficient surface modifier. The PAA coated filler is submitted to the measurement of the surface bonded amount, bonding efficacy, X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography. Maximum efficacy is expected at the monolayer coverage of the surface, which is about 0.6 wt.% according to the calculation based on the way they are aligned and is basically in agreement with the “substrate overlayer” model based on the mole ratio of C²⁸⁶ and C²⁹⁰ taking no account of the possible underestimation because of the inaccuracy or because of the CH_x contamination present originally on the CaCO₃. The initial decrease of the mole ratio of C²⁹⁰/O and C²⁹⁰/Ca with the surface bonded PAA may indicate that the bonding interaction between the polymer and the filler surface is the leaving of one molecular carbon dioxide. The IGC measurement shows that there is a considerable surface tension falling in the case of the PAA modified filler compared with the reference. An abnormal high surface energy in the case of filler treated with 4% PAA is observed.     

Novel Pd-Cu/bacterial cellulose nanofibers: Preparation and excellent performance in catalytic denitrification

In this work, we describe a novel facile method to prepare long one-dimensional hybrid nanofibers by using hydrated bacterial cellulose nanofibers (BCF) as template. Palladium-copper nanoparticles were prepared in BCF by immersing BCF in a mixture solution of PdCl₂ and CuCl₂ in water and followed reduction of absorbed metallic ion inside of BCF to the metallic Pd-Cu nanoparticles using potassium borohydride. The bare BCF and the composites were characterized by a range of analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results reveal that the Pd-Cu nanoparticles were homogeneously precipitated on the BCF surface. The Pd-Cu/BCF was used as a catalyst for water denitrification, which showed that it has high catalytic activity.     

Facile synthesis of calcium silicate hydrate using sodium dodecyl sulfate as a surfactant assisted by ultrasonic irradiation

Calcium silicate hydrate (CSH) consisting of nanosheets has been successfully synthesized assisted by a tip ultrasonic irradiation (UI) method using calcium nitrate (Ca(NO₃)·4H₂O), sodium silicate (Na₂SiO₃·9H₂O) and sodium dodecyl sulfate (SDS) in water. Systematic studies found that reaction time of ultrasonic irradiation and concentrations of surfactant (SDS) in the system were important factors to control the crystallite size and morphologies. The products were characterized by X-ray power diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrometry (FTIR). The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the CSH. These characterization techniques revealed the successful formation of a crystalline phase with an average crystallite size of about 13 nm and nanosheet morphology at a reaction time of 10 min UI with 0.2 g SDS in solvent which were found to be optimum time and concentrations of SDS for the synthesis of CSH powders.     

Simultaneously depositing polyaniline onto bacterial cellulose nanofibers and graphene nanosheets toward electrically conductive nanocomposites

In this study, we report the construction of a ternary flexible nanocomposite of bacterial cellulose/graphene/polyaniline (BC/GE/PANI) via a facile two-step strategy. Bacterial cellulose/graphene (BC/GE) is first prepared by a novel in situ membrane-liquid-interface method, in which the three-dimensional continuous BC nanofibers can be maintained and the introduced GE can improve the mechanical properties mainly due to the uniform dispersion of GE in the BC matrix. To construct the effectively interconnected conductive paths between separated GE nanosheets, polyaniline (PANI) is simultaneously deposited on the surfaces of both BC nanofibers and GE nanosheets to obtain BC/GE/PANI with excellent electrical conductivity. It is found that the as-prepared BC/GE/PANI has an electrical conductivity of 1.7 ± 0.1 S cm⁻¹, which is higher than most of PANI-based composites. It is believed that the BC/GE/PANI nanocomposite possesses great potential for applications in electromagnetic shielding and flexible electrodes.     

The impact of various drug ferrying additives on phase transitions behavior of Calcite,Vaterite and Aragonite

The study aimed to explore the influence of eleven excipients (in three groups) on the phase transition of CaCO3. The groups were; Group 1: Ca-TEG (CaCO3- Tetraethylene Glycol), Ca-PVP (Polyvinylpyrollidone), Ca-LUT (Lutrol Micro 127 MP), Ca-HPMC (Hydroxypropylmethyl Cellulose) and Ca-Blank, Group 2: Ca-G44/14 (Gelucire 44/14), Ca-CRH40 (Cremophor RH40), Ca-SHS (Solutol HS15), Ca-LAB (Labrasol) and Group 3: Ca-GE (Garlic extract), Ca-CAS (Casein), Ca-TCT (Transcutol). Group 1 confers the characteristics of only Calcite, while, Group 2, gave the highest mole fraction of Vaterite. Group 3 gave the highest mole fraction of Vaterite followed by Calcite/Aragonite. FESEM of Ca-CRH40 illustrated numerous parallel stacks of nano-hexagonal vaterite columns building the inner structure of bacillus type Vaterite, while that of Ca-TCT suggested the presence of sunflower shaped Vaterite particles and rhombohedral calcite. The % dissolution efficiency was found maximum for Ca-TEG (90.65%) followed by Ca-PVP (86.13%), Ca-HPMC (76.25%), Ca-LUT (52.12%) and CaBlank (22.96%).     

超声对硫酸钙结晶过程影响的研究

研究了超声对硫酸钙结晶过程的影响。实验表明，与对比样相比，超声可以明显缩短成核时间，改变结晶量，影响结晶在不同方向的成长速度，使结晶的形状比例(长／宽)减小。粒度分布的定量测定和计算显示，超声使硫酸钙结晶粒度分布范围由200μm缩小到100μm，体积平均直径从69．9μm降到26．59μm；硫酸钙的成核速率提高2．74倍，但结晶成长速率减少到对比样的40．9％。两者番加的结果体现为结晶过程总速率的增加。     

Study on removing calcium carbonate plug from near wellbore by high-power ultrasonic treatment

In this paper, the effects of ultrasonic wave on the removal of inorganic scaling and plugging in cores and the influence of the key wave field parameters, process parameters and core physical parameters on the plugging removal efficiency are systematically studied. The main dynamic mechanism of ultrasonic plugging removal is also systematically analyzed. Results show that the transducer frequency, transducer power, ultrasonic treatment time and initial permeability of core have great influence on the effect of ultrasonic scale removal. When the cumulative treatment time of ultrasonic wave exceeds 60 min, the recovery rate of core permeability tends to be stable. Best effect can be achieved when processing for 80–120 min cumulatively; the plugging removal effect is improved with the increase of ultrasonic transducer power and ultrasonic frequency, but the effect of plugging removal is not obvious with the further increasing of them. In addition, it is proved that the effect of removing calcium carbonate plug from near wellbore by hydrochloric acid solution is slightly better than that by ultrasonic treatment alone. Finally, the micro dynamic mechanism of removing inorganic scale plug by high-power ultrasonic treatment is discussed in view of ultrasonic inorganic scale body crushing, ultrasonic cavitation, ultrasonic friction, ultrasonic peristaltic transport operation and ultrasonic fracture-making and permeability-increasing effect.     

Surface modification of calcium carbonate: radical graft polymerization of vinyl monomers onto calcium carbonate surface initiated by azo groups introduced onto the surface

—The preparation of calcium carbonate modified by 12-hydroxystearate groups and the grafting of polymers onto the surface by the polymerization of vinyl monomers initiated by azo groups introduced onto the surface were investigated. The preparation of calcium carbonate modified by 12-hydroxystearate was achieved by the reaction of calcium chloride with sodium carbonate containing a small amount of sodium 12-hydroxystearate. The introduction of azo groups onto calcium carbonate was successfully achieved by the direct condensation of the carboxyl group of 4,4'-azobis(4-cyanopentanoic acid) with 12-hydroxystearate groups on the modified calcium carbonate using N,N'-dicyclohexylcarbodiimide as a condensing agent. It was found that the radical polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole (NVC), was initiated by azo groups introduced onto the surface, and the corresponding polymers were grafted onto the surface based on the propagation of polymer from the surface: the percentage of grafting of polyMMA, polystyrene, and polyNVC reached 5.7, 9.5 and 3.5%, respectively, at 70°C. The percentage of grafting was found to decrease with decreasing monomer concentration. The wettability of calcium carbonate surface was found to turn from hydrophilic to hydrophobic by the grafting of polymers.     

Electrical conductivity and optical transparency of bacterial cellulose based composite by static and agitated methods

Composites consisting of bacterial cellulose (BC) and ionic conducting polymer (ICP) were prepared. BC was biosynthesized in media at 0, 25, 50 and 100 rpm. ICP was chemically synthesized at different concentrations of ionic salt. The corresponding electrical conductivity of the composites was measured as a function of ionic salt concentration. ICP improved the optical transparency and electrical conductivity of the BC/ICP composites. Morphological images of BC/ICP composites showed that the pore size of the BC pellicle increased while the diameter and density of the BC fibers decreased. The cultivation method was critical in affecting the structure and electrical conductivity of the composites.     

Ultrasound assisted preparation of calcium alginate beads to improve absorption of Pb+2 from water

Calcium alginate (CaAlg) beads were prepared using ultrasound for use in the removal of lead from natural and wastewaters by ion exchange. Ultrasound was applied in a batch mode with an ultrasonic bath or in a flow mode using an ultrasonic clamp-on device. For comparison purposes the synthesis was performed in batch mode in the absence of the ultrasound. The beads prepared using ultrasound showed a greater ion exchange capability which could be ascribed to a larger specific surface area as a result of surface roughening induced by cavitation.Scanning Electron Microscopy (SEM) images revealed that the roughening was in the form of corrugation for the product with the best ion exchange capability obtained in the flow process where preformed CaAlg droplets were subjected to ultrasound during the setting process. These beads performed 11% better for lead removal than those synthesized in the absence of ultrasound.     

A simple synthesis method to produce metal oxide loaded carbon paper using bacterial cellulose gel and characterization of its electrochemical behavior in an aqueous electrolyte

A simple synthetic chemical process to produce metal oxide loaded carbon papers was developed using bacterial cellulose gel, which consisted of nanometer-sized fibrous cellulose and water. Metal ions were successfully impregnated into the gel via aqueous solution media before drying and carbonization methods resulting in metal oxide contents that were easy to control through variations in the concentration of aqueous solutions. The papers loaded by molybdenum oxides were characterized as pseudocapacitor electrodes preliminary, and the large redox capacitance of the oxides was followed by a conductive fibrous carbon substrate, suggesting that a binder and carbon black additive-free electrode consisting of metal oxides and carbon paper was formed.     

Effects of ultrasound energy on degradation of cellulose material

The rationale for selection of waste cellulose source and method for its degradation, such as ultrasound, aeration and coupled energy, is examined. Consideration is given to the availability of waste material for the conservation of global resources, pollution effects from energy forms and efficiency of energy transfer. Availability of the sources and possible ways of converting them to fuels, processes involved in its production and the possible effects on the environment are discussed. Manufactured cellulose and waste paper are used as the source for these experiments and the rationale behind their use in the environment is analysed. An ultrasound reactor that operates at 80 W and 38 kHz was used in breaking down the samples to produce glucose and other chemical species. One of the routes being explored is the further conversion of these molecules into fuel (alcohol).