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In this paper a novel approach to the flocculation phenomenon was investigated, i.e. application of light-sensitive polymers. A hypothesis was proposed that the energy delivered by an electromagnetic wave will trigger the photo-dimerization reaction, which in turn will lead to the destabilization process via bridging phenomenon. In research two polymers differing in content of light-sensitive component, i.e. cinnamoyl groups, were synthesized by means of conventional free radical copolymerization and postreaction. In the flocculation experiments a model suspension of CaCO3 precipitate in deionized water was used. The experiments were performed using two different mixer configurations. Unfortunately, the postulated mechanism was proved to be wrong. Although both polymers acted as good destabilization agents directly after injection to suspension, the UV radiation had no impact on the process.

In this paper, the experimental research concerning the impact of the hydrophilic-hydrophobic transition of a polymer exhibiting the Upper Critical Solution Temperature (UCST) onto the crystallization process of inorganic salt is presented. A hypothesis was postulated that under favorable process conditions the sudden change of macromolecules properties and the resulting appearance of insoluble particles will induce the nucleation process of the salt. Since the transition point parameters may be precisely designed, the described mechanism would eliminate the stochastic nature of the crystallization process. Although performed experiments proved that the postulated process mechanism was incorrect, the presence of macromolecules had a significant impact on the crystallization course. The stochastic nature of the process was not eliminated, nevertheless, it seems that a specific point of nucleation was created which was independent of the cloud point temperature (TCP) of the polymer. Moreover, the surface morphology of crystals was changed.

The application of polymers as a tool in the crystallization process is gaining more and more interest among the scientific community. According to Web of Science statistics the number of papers dealing with “Polymer induced crystallization” increased from 2 in 1990 to 436 in 2020, and for “Polymer controlled crystallization”—from 4 in 1990 to 344 in 2020. This is clear evidence that both topics are vivid, attractive and intensively investigated nowadays. Efficient control of crystallization and crystal properties still represents a bottleneck in the manufacturing of crystalline materials ranging from pigments, antiscalants, nanoporous materials and pharmaceuticals to semiconductor particles. However, a rapid development in precise and reliable measuring methods and techniques would enable one to better describe phenomena involved, to formulate theoretical models, and probably most importantly, to develop practical indications for how to appropriately lead many important processes in the industry. It is clearly visible at the first glance through a number of representative papers in the area, that many of them are preoccupied with the testing and production of pharmaceuticals, while the rest are addressed to new crystalline materials, renewable energy, water and wastewater technology and other branches of industry where the crystallization process takes place. In this work, authors gathered and briefly discuss over 100 papers, published in leading scientific periodicals, devoted to the influence of polymers on crystallizing solutions.

The key feature of thermosensitive polymers is the reversible transition between the hydrophilic and hydrophopic forms depending on the temperature. Although the main research efforts are focused on their application in different kinds of drug delivery systems, this phenomenon also allows one to precisely control the stability of solid-liquid dispersions. In this paper research on the application of poly(N-isopropylacrylamide) copolymers in processing of minerals is presented. In the experiments tailings from flotation plant of one of the coal mines of Jastrzębska Spółka Węglowa S.A. (Poland) were used. A laser particle sizer Fritsch Analysette 22 was used in order to determine the Particle Size Distribution (PSD). It was proved that there are some substantial issues associated with the application of thermosensitive polymers in industrial practice which may exclude them from the common application. High salinity of suspension altered the value of Lower Critical Solution Temperature (LCST). Moreover, the co-polymers used in research proved to be efficient flocculating agents without any temperature rise. Finally, the dosage needed to achieve steric stabilization of suspension was greatly beyond economic justification.

The increasing demand for the heat transfer intensification in microelectronics, high-tech industries or even in transportation motivates the search for new solutions in this field of science. One of the studied concepts is the application of nanofluids characterized by enhanced thermal properties, e.g. improved thermal conductivity or overall heat transfer coefficient. In this work a simple synthesis method of temperature responsive CuO–water colloidal system is presented. In the experiments a two step synthesis method was employed and several different copolymers of poly(N-isopropylacrylamide) were used as stabilization agents. The main efforts of the research were focused on the obtaining of colloidal system which stability would suddenly collapse at desired chosen temperature. Additionally, such transition should be reversible. The synthesized samples were characterized by particle size distribution analysis, zeta potential, absorbance and thermal conductivity. It was proved that it is possible to achieve the chosen goal using appropriate combination of ultrasonication, polymer adsorption and the change of ionic strength of the mother liquid.

In this paper a comprehensive study on the influence of heating rate on thermosensitive flocculation is presented. Experimental investigation was performed using a laboratory setup consisting of thermostated mixing tank with four baffles agitated by a mechanical propeller. PSD and the resulting mean aggregate size of a model suspension system consisting of calcium carbonate and a p(NIPAM-co-DADMAC) copolymer in RO water was measured with a modified laser particle sizer. It is found that in the studied range of heating rate (from 0.29 K/min–3.73 K/min) the final state of the system is almost identical regardless the heating rate. A semiempirical floc growth kinetics model was proposed and verified. In order to respect the effect of heating regime a parameter named the heating regime efficiency KHR was introduced. The dependence of the model parameters on dimensionless flocculant dosage DF*, heating rate HR and heating regime efficiency KHR was described by a power-law dependence. The experimental data and model predictions were found to be in a very good agreement.

Thermosensitive polymers are gaining increasing interest due to their possible applications as drug delivery systems, flotation agents in mineral ore processing or flocculants in wastewater treatment. Lower Critical Solution Temperature (LCST) is a crucial parameter of thermoresponsive polymers. In this work the comparison of four different methods of LCST determination, i.e. transmittance, viscosimetric, Dynamic Light Scattering (DLS) and pH measurement, are presented. They are found to be complementary and each of them is shown to fail under certain condition. For the purpose of this research a cationic copolymer of poly(N-isopropylacrylamide) with diallyldimethylammonium chloride was synthesized. Moreover two reference polymer samples were investigated.

The goal of this research was to determine the impact of nonionic surfactants on drag reduction effect in water and metal oxide nanofluid. Two nonionic surfactants (Rokacet O7 and Rokanol K7) and copper(II) oxide water-based nanofluid were examined. Friction factors in a 4 mm diameter pipe for the Reynolds number between 8000 and 50000 were determined. Results showed that addition of nonionic surfactants caused the decrease of friction factor in water and nanofluid. The drag reduction effect was similar in both cases. Presence of nanoparticles in the system has no great influence on drag reduction effect.

Flocculation is a key unit operation in many solid–liquid separation processes, especially in wastewater treatment and mineral ore processing. At present, many attempts of flocculation process enhancement may be found in literature. One of them is an ultrasonic conditioning of polymer solution which, among the others, reduces the time needed to achieve the steady state. In this paper a semiempirical model quantifying the effect of flocculant sonication on floc growth kinetics occurring in an agitated vessel is proposed. The model is validated on the basis of experimental research made in a laboratory setup for on-line analysis of particle size distribution. Four different commercially available flocculants were sonicated and used in experiments with a model suspension of commercial chalk dust in distilled water and industrial suspension of ultrafine coal particles. It was proved that the effect of flocculation time and sonication volume energy density on floc size cannot be decomposed into two separated effects. This model may be used for the coarse estimation of other factors’ impact on the course of aggregation and breakage processes.

Flocculation process based on water soluble polymers as flocculating agents is still intensively researched nowadays, despite the introduction of these materials about fifty years ago. Dual polymer flocculation or application of new, more sophisticated macromolecules is proposed as a new approach. Simultaneously, more detailed mathematical models of flocculation are developed. The employment of polymer degradation model in population balance equations (PBE) is proposed in the paper. The suspension of chalk in distilled water was flocculated using three types of ultrasonically conditioned commercial flocculants. The experiments were performed using an apparatus for on-line determination of particle size distribution (PSD). The obtained results were compared with simulations using the Class Method. It was proved that the kinetic constant in the aggregation kernel can be described by a function similar to the one showing a change of mean molecular weight of polymer with sonication time.

Despite the progress in chemical engineering, efficient dewatering of ultra-fine coal (

Dual-polymer flocculation with unmodified and ultrasonically conditioned flocculant is presented in this paper. In the experiments two types of suspensions, i.e. chalk dust and kaolin clay in RO water were investigated. In the former case the bridging mechanism was expected whereas in the latter case charge neutralization and charge patching mechanisms should be dominant. The measurements were carried out in a laboratory setup for on-line particle size distribution (PSD) analysis consisting of stirred vessel with turbine mixer, laser particle size analyzer Fritsch Analysette 22 and peristaltic pump. The flocculation kinetics is described in terms of PSD and mean particle diameter change in time. Authors proved that ultrasonic conditioning may be an effective alternative for a dual-polymer flocculation where two different flocculants are used. In some cases the mechanical strength of flocs, created by combination of unmodified and conditioned polymers, was improved which resulted in reduction of time needed to achieve the steady state of the system.

The influence of temperature on particle size distribution of chalk suspension in the presence of a thermosensitive flocculant based on N-isopropylacrylamide and 3-(acryloyloxy)propanoic acid was investigated. No aggregation was observed at room temperature upon the addition of the polymer. When the system was heated, flocculation took place and the mean particle diameter was found to be temperature dependent. The polymer dosage influence on the process was examined. In higher polymer concentration the investigated process was fully reversible, i.e. aggregates broke upon cooling. The possibility to control particle size by temperature adjustment is discussed and the process' model is proposed.

Aggregation is a very widely encountered phenomenon in nature as well as in industrial processes. It plays an important role in processing of air and water, e.g. wastewater treatment plants, power plants, mining facilities. The new, cost-effective solutions are developed. Among the others modification of the flocculants by means of ultrasounds, mixtures with surfactants or polydispersive flocculant blends can be mentioned. Flocculants used in the aggregation process are long-chain polymers that can be of negative, positive or neutral charge. The aggregation caused by usage of such flocculants is the result of three different mechanisms: bridging, charge neutralization or electrostatic patch. The influence of ultrasonic field on the efficiency of different flocculants was investigated. Suspension of chalk in water was used and the measurements were taken in the laser particle sizer. The influence of the sonication time on flow curves is also presented.

A lumped discrete population balance model has been selected for the verification of the experimental data. Solid aggregates of chalk suspended in vigorously mixed suspension were treated as fractal objects with a mass fractal dimension taken as 2.02. A specially written computer program has been used for determining the evolution of population of aggregates during the course of mixing. The PSD (particle size distribution) results obtained by numerical calculation for fractal and non-fractal approaches have been compared, showing a better fit in the case of the fractal model. The aggregation and breakage rate coefficients were correlated as a function of the average energy dissipation rate in the vibrating mixer.

Experimental data are provided for the breakage of chalk aggregates in liquid suspensions agitated by rotating and vibrating mixers. The results are analysed using a mechanistic model of breakage which relates the pseudoequilibrium aggregate size to the energy dissipation rate in the stirred vessel. The analysis suggests that the growth and breakage of the chalk aggregates are reversible processes which lead to the formation of fractal aggregates with a dimensionality close to 2. Additionally, the breakage of aggregates in both the vibrating and the rotating mixers occurs by turbulent fluid stresses and is uniquely related to the energy dissipation rate in the vessel and the fractal dimensionality of the aggregates.

The impact of suspension heating method on the flocculation process using thermosensitive polymer is reported in this paper. In experiments a model suspension of chalk in RO water (purified by Reverse Osmosis) was destabilized using a copolymer of N-isopropylacrylamide (NIPAM) and cationic diallyldimethyl ammonium chloride (DADMAC). The measurements were made using a laboratory setup consisting of a mixing tank with four baffles, Rushton turbine, laser particle sizer Analysette 22 by Fritsch and a system of pump and thermostating devices. Two different modes of heating were used. In the first case the temperature of the system was gently raised above the Lower Critical Solution Temperature (LCST) using an electrical heater placed inside the tank, while in the second case the system temperature was rapidly raised by an injection of hot water directly into the tank. It was proven that heating method as well as the polymer concentration was crucial to the shape and size of created flocs.

Paper presents results of investigations on rheological properties of CuO-water and CuO-ethylene glycol nanoflmds. It was found that mentioned nanofluids exhibit non-Newtonian properties and their flow curves can be approximated by means of Hershel-Bulkley's rheological model. A mutual influence of share stress and temperature on viscosity of nanofluids can be described accurately by means of Klein's equation.

Experimental investigations of convective heat transfer in nanofluid based on the Cu (approx. 0.15% and 0.25% vol.) nanoparticles synthesized in polyol process were conducted at constant heat flux conditions. A 30% increase in average heat transfer coefficient was found against the results obtained for a pure host liquid (ethylene glycol). Even more significant increase was in the entrance region.Copyright © 2008 by ASME