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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.

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.

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.