Influence of ultrasonic treatment on size of borax crystals : bachelor thesis

Abstract

Cilj ovog rada bio je sagledati princip rada ultrazvuka te ispitati utjecaj amplitude ultrazvuka na veliĉinu kristala boraksa dobivenih postupkom kontroliranog hlaĊenja u kristalizatoru s miješanjem. U prvom dijelu istraživanja provedena je šaržna kristalizacija u reaktoru s miješanjem iz otopine zasićene pri temperaturi od 30 °C i hlaĊene brzinom od 6 ° C h -1 . Pri tome je praćena promjena koncentracije otopine kako bi se utvrdio poĉetak nukleacije i promjena koncentracije uslijed rasta kristala, a po završetku procesa izvršeno je prosijavanje i granulometrijska analiza produkta. U drugom dijelu radu sagledavan je utjecaj amplitude ultrazvuka na tri izdvojene klase prethodno dobivenog produkta šaržne kristalizacije uz miješanje. Pri ovim ispitivanjima su klase kristala srednje veliĉine od 45, 170 i 375 m, ultrazvuĉno su suspendirane u otopini acetona zasićenoj i termostatiranoj pri 25 °C. Amplitude ultrazvuka iznosile su 20, 30 i 40 %. Nakon djelovanja ultrazvuka u trajanju od 10, 20 i 30 min granulometrijska svojstva kristala analizirana su metodom laserske difrakcije. Istodobno, uz mjerenje veliĉine kristala odreĊivana je elektriĉna vodljivost otopine, , kako bi se sagledale koncentracijske promjene unutar otopine. Rezultati rada ukazali su da niti jedna od izdvojenih klasa kristala nije znaĉajno promijenila svoju veliĉinu tijekom procesnog vremena pri ispitivanim amplitudama ultrazvuka. TakoĊer ni vodljivost otopine nije se promijenila, zbog ĉega se može zakljuĉiti da navedene amplitude neće uzrokovati lom niti otapanje kristala boraksa te ih se može koristiti pri ispitivanju utjecaja ultrazvuka na kinetiku kristalizacije boraksa.The purpose of this study was to observe the ultrasound working principle and to examine the influence of ultrasonic amplitude on the size of borax crystal obtained by the controlled cooling in the batch stirred crystallizer. In the first part of the study, batch crystallization was carried out in a stirred reactor from a solution saturated at 30 ° C and cooled at 6 ° C h -1 . Concentration change of the mother liquor over process time was measured in order to determine the onset of nucleation and the change in the concentration due to crystal growth. Upon the completion of the process, sieving and granulometric analysis of the product was done. In the second part of the work, the effect of ultrasound amplitude on three classes of crystals obtained in a batch stirred reactor was examined. The classes of crystals of average size 45, 170 and 375 m were ultrasonically suspended in a solution of acetone saturated and thermostated at 25 ° C. Ultrasound amplitude was 20, 30 and 40%. After 10, 20 and 30 min of ultrasonic treatment, the granulometric properties of the crystal were analysed by laser diffraction method. At the same time, with the measurement of the crystal size, the electrical conductivity of the solution, , was measured in order to monitor concentration change within the solution. The results of the study showed negligible change in size of examined crystal classes over process time at the applied ultrasound amplitudes. Also, the conductivity of the solution has not changed, which indicated that applied amplitude will not cause breakage or dissolution of the borax crystals and can be used in the further study of influence of ultrasound on the crystallization kinetics of borax

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This paper was published in Croatian Digital Thesis Repository.

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