I\'m doing a lab on Separation by floatation, first we used the geothite and san

Question

I'm doing a lab on Separation by floatation, first we used the geothite and sand then added them in a glass cylinder with dishwashing soap. then we had to adjust th ph tp 4.5-5.0. and observed. then the second part was separation of methylene blue from red food dye, first by using dishwashing soap then measured the absorbance at 625nm then using CTAB and measured the absorbance at 525nm. I really dont get htis lab not I know what to write about it in my lab report. Why did we have to adjust the pH to be within 4.5-5. thne why did the absorbance was decreasing, and the significnt of the reading at a different wavelengths after 15 minutes.

Explanation / Answer

Case 1) Geothite + sand with dish wash soap at pH 4.5-5.0. In this seperation process, pH play a key role.Geothite contains iron and sand is a silicate as well as soap is a surfactant i.e alkyl sulphate. soap adsorbs the components of geothite and sand and forms froath.so hydrophilic materials are collected at froath. So this adsorption process takes place at pH 4.5-5.0 only. finally at this buffer condition the adsorption is higher, seperation of fe and silicate is easy.

Case 2) Methylene blue + Soap forms micelle in a low concentration but with CTAB forms nanomicelles at high concentrations. so the absorption decreses from 625 nm to 525nm. It means CTAB highly active in the formation of micelle than soap, conatins a long chain hydrocarbon with polar head which adsorps the methlene blue form micelle i.e nanomicelle ( latest reports) whcih shifts the wave length from high to low.

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