Henry Hatakka

Oxidation of aqueous pharmaceuticals by pulsed corona discharge

Oxidation of aromatic compounds of phenolic (paracetamol, β-oestradiol and salicylic acid) and carboxylic (indomethacin and ibuprofen) structure used in pharmaceutics was studied. Aqueous solutions were treated with pulsed corona discharge (PCD) as a means for advanced oxidation. Pulse repetition frequency, delivered energy dose and oxidation media were the main parameters studied for their influence on the process energy efficiency. The PCD treatment appeared to be effective in oxidation of the target compounds: complete degradation of pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media. Low-molecular carboxylic acids were identified as ultimate oxidation by-products formed in the reaction.

Pulsed corona discharge: the role of ozone and hydroxyl radical in aqueous pollutants oxidation

Ozone and hydroxyl radical are the most active oxidizing species in water treated with gas-phase pulsed corona discharge (PCD). The ratio of the species dependent on the gas phase composition and treated water contact surface was the objective for the experimental research undertaken for aqueous phenol (fast reaction) and oxalic acid (slow reaction) solutions. The experiments were carried out in the reactor, where aqueous solutions showered between electrodes were treated with 100-ns pulses of 20 kV voltage and 400 A current amplitude. The role of ozone increased with increasing oxygen concentration and the oxidation reaction rate. The PCD treatment showed energy efficiency surpassing that of conventional ozonation.

Oxidation of Aqueous Paracetamol by Pulsed Corona Discharge

Oxidation of paracetamol in aqueous solution was studied by using pulsed corona discharge as a means for advanced oxidation. Pulse repetition frequency, the delivered energy dose, and oxidation media were the main parameters evaluated. The pulsed corona discharge treatment appeared to be effective in oxidation of paracetamol: complete degradation of target pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media, the fastest oxidation rate was observed in oxygen-enriched air. Low-molecular carboxylic acids were identified as the products formed in the reaction.

Crystallization kinetics of potassium sulfate in an MSMPR stirred crystallizer

Abstract Experimental work on a potassium sulfate-water system was carried out using ten and fifty liter crystallizers. Different impeller velocities and suspension densities were used. The crystal size distribution was determined over the range from 0.1 μm to the largest crystals, which have been produced in the crystallizers, by the combination of Coulter LS-130 light scattering laser and by Vidas image analyzer results. Experimental evidence from continuous crystallizers frequently shows, at least for small crystals, deviation from the McCabe ΔL law. In this case, the estimation of kinetics of both nucleation and growth rate becomes more complicated. In this work the crystal size distribution was determined experimentally. The relation between growth rate and particle size is investigated. The methods of estimation of kinetics for industrial use are discussed. The experimental data of population density distribution was fitted directly by the three-parameter model presented by Mydlarz and Jones for a steady state MSMPR crystallizer. Then the relation between growth rate and particle size was calculated by the corresponding three-parameter growth rate model. The relation between growth rate and particle size shows that the apparent crystal growth rate increases linearly with the crystal size when the crystal size is smaller than about 10 μm, is strongly size-dependent when the crystal size is between 10–700 μm, and is size-independent when the crystal size is greater than 700 μm. A mechanism of growth rate dispersion is suggested.